CN113338950A

CN113338950A - Shield closed arrival construction method of freezing method and cement system combined steel sleeve

Info

Publication number: CN113338950A
Application number: CN202110722756.7A
Authority: CN
Inventors: 李国鹏; 张斌; 钟明; 范喜德; 葛广春; 方朝刚; 李波; 翟洪志; 苏科; 汪优; 赵晓薇
Original assignee: China Railway Shanghai Investment Group Co Ltd
Current assignee: China Railway Shanghai Investment Group Co Ltd
Priority date: 2021-06-28
Filing date: 2021-06-28
Publication date: 2021-09-03

Abstract

The invention relates to the technical field of subway construction, and discloses a shield airtight arrival construction method of a freezing method and a cement system combined steel sleeve, which comprises the following steps: step one, cement system reinforcement construction; step two, horizontal freezing method construction; step three, shield arrival construction of the steel sleeve: installing and fixing a steel sleeve, sealing and checking the steel sleeve, chiseling a portal door, adjusting tunneling parameters, controlling the tunneling direction, pouring a receiving base, chiseling the rest part of the portal door, pulling out a freezing pipe, backfilling the steel sleeve, tunneling at a reaching section, grouting at a shield tail, entering the steel sleeve by a shield tunneling machine, and separating the steel sleeve to seal the portal door. The invention not only carries out end reinforcement through the combination of horizontal freezing and cement system reinforcement, solves the defects of short reinforced area and poor water stop effect of the steel sleeve shield receiving technology, thereby avoiding the occurrence of serious shield receiving safety accidents, but also realizes a tunnel portal in a pressure maintaining state through the steel sleeve closed receiving construction technology, and most effectively ensures the receiving safety of the shield machine.

Description

Shield closed arrival construction method of freezing method and cement system combined steel sleeve

Technical Field

The invention relates to the technical field of subway construction, in particular to a shield airtight arrival construction method of a freezing method and a cement system combined steel sleeve.

Background

At present, the construction of urban subways in China is mostly carried out by adopting a shield method so as to ensure that engineering tasks are completed safely and in good quality as required. The shield arrival receiving is the last key link of the shield method tunnel construction site and is also one of the key points and difficulties of the shield method construction site. Whether the shield can smoothly enter the tunnel is related to success or failure of the whole tunnel construction. The shield machine arrival construction refers to the whole construction process that a tunnel in a penetration interval of the shield machine enters a station and is pushed onto a shield receiving base from 50m before the shield machine arrives at the next station (a turnaround well). The shield machine can be ensured to arrive smoothly in a correct posture, and the prevention of accidents such as collapse is the key point of construction. The traditional end head reinforcing scheme mainly adopts the methods of stratum stirring, rotary jetting, grouting and the like to improve indexes such as stratum strength, permeability and the like, and avoids water and soil instability accidents such as ground collapse, sand jetting, water burst and the like in the process of entering a tunnel by a shield machine. The steel sleeve receiving construction method is an in-hole receiving process capable of reducing ground reinforcing measures, has the characteristics of safety, strong adaptability, short construction period, reusability and the like, and is suitable for projects with complex geological conditions and high requirements on surrounding environment protection in shield tunnel construction.

The starting end of part of the subway is mainly a fine sand layer, and the water-rich fine sand has the characteristics of poor self-stability, small cohesive force, poor workability, strong water permeability and the like, and has poor engineering properties. The sand content of the water-rich sand layer reaches more than 30 percent, the porosity ratio is large, the water content is large, and the water-rich sand layer has the characteristics of large fluidity, small bearing capacity, poor self-stability and the like. Sedimentation in water-rich sand layers occurs mainly in two ways: firstly, the settlement generated by the reduction of the pore water pressure and secondly the displacement of the soil body generated by excavation. The stratum has the characteristics that the stratum flow is large under the condition that local space leaks, the stratum disturbance in a large range is easily caused, meanwhile, the compressibility and the flowability of the soil layer are poor under the condition that the soil layer is locally extruded in a certain space, and the friction force of the soil layer is increased rapidly. In a common soft soil stratum, the soil layer loss is small in the flowing process of underground water, soil can flow to the periphery under the condition that soil is extruded, and the friction increase of the soil is much smaller than that of a pure sand layer. Under the geological conditions of the water-rich sand layer, the method has the specific problems which are difficult to solve: (1) the ground settlement is difficult to control, and large-area extra-large settlement is easy to occur under the condition of poor tunneling control; (2) the soil pressure setting requirement of the soil bin is reasonable, various problems (ground settlement, cutter abrasion and tunneling speed) caused by poor soil pressure control are immediately reflected, in addition, the shield launching risk is extremely high, the tunneling posture control difficulty is also high, the conventional stratum reinforcing method cannot guarantee that the reinforcing effect reaches the standard, in complex strata such as deep earth covering and high-water-pressure fine sand, the conventional tunnel portal sealing cannot guarantee the underground water pressure, once underground water breaks through the tunnel portal sealing, the underground water gushes out the fine sand in the interlayer stratum along gaps on the periphery of the shield body, and serious safety quality accidents can be caused.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a shield airtight arrival construction method of a freezing method and a cement system combined steel sleeve, which not only can be used for reinforcing the end by combining horizontal freezing and cement system reinforcement to ensure the stability of the tunnel face when a tunnel portal is chiseled off, but also can be used for overcoming the defects of short reinforcing area and poor water stop effect of a steel sleeve shield receiving technology, thereby avoiding the occurrence of major shield receiving safety accidents, realizing the tunnel portal in a pressure maintaining state by using the steel sleeve airtight receiving construction technology, and most effectively ensuring the receiving safety of a shield machine.

The purpose of the invention is realized by adopting the following technical scheme:

a shield airtight arrival construction method of a freezing method and a cement system combined steel sleeve comprises the following steps:

step one, cement system reinforcement construction:

a. constructing a triaxial mixing pile: leveling a construction site, lofting a pile position, constructing a guide groove, drilling a three-axis deep mixing pile, sinking and lifting a drill rod of a pile machine, grouting, stirring, lifting, re-stirring and engaging construction of the three-axis mixing pile;

b. constructing a triple-pipe rotary jet grouting pile: construction preparation, positioning of a drilling machine, hole leading drilling, core barrel pulling out, grouting pipe insertion, rotary spraying lifting and drilling machine displacement;

step two, horizontal freezing method construction: positioning, perforating and mounting an orifice pipe, mounting an orifice device, drilling, measuring, sealing the bottom of a hole, and pressing for leakage test;

step three, shield arrival construction of the steel sleeve: installing and fixing a steel sleeve, sealing and checking the steel sleeve, chiseling a portal door, adjusting tunneling parameters, controlling the tunneling direction, pouring a receiving base, chiseling the rest part of the portal door, pulling out a freezing pipe, backfilling the steel sleeve, tunneling at a reaching section, grouting at a shield tail, entering the steel sleeve by a shield tunneling machine, and separating the steel sleeve to seal the portal door.

Further, before proceeding to step two, it is necessary to perform freeze hole placement and set horizontal freeze parameters.

And further, before the third step, the construction preparation work is required to be carried out, and the method specifically comprises the steps of shield tunneling machine attitude measurement, monitoring control, tunnel portal chiseling, horizontal freezing pipe extraction, steel sleeve backfilling and tunnel portal tensioning device installation.

And further, the concrete steps of installing and fixing the steel sleeve in the third step are that personnel, materials and equipment are put in place, the steel sleeve is positioned to prevent the wire, the transition connecting plate is hoisted to go into the well, the transition connecting plate is transported to a working surface and is assembled in place, the transition connecting plate and the portal steel ring are welded, a plurality of force-transmitting frames are hoisted to go into the well in sequence, the end cover plate is hoisted to go into the well in sequence, the steel sleeve is installed and connected with the steel sleeve, the steel sleeve is integrally moved and connected with the transition connecting plate, a counter-force system is installed, the sleeve body is reinforced, a mortar base is poured, and the filler and the shield in the steel sleeve are pushed to receive.

Further, the concrete step of pouring the mortar base is to pour a C20 mortar base with the thickness of 15cm in the range of 60 degrees at the middle position of the bottom of the steel sleeve.

Further, the concrete steps of the steel sleeve sealing inspection in the third step include the steps of inspecting the roundness of the steel sleeve, inspecting the sealing performance of the steel sleeve and inspecting the welding seam of the steel sleeve.

And further, the concrete step of pulling out the freezing pipe in the third step comprises brine heating, brine circulation and trial pulling through a plurality of chain blocks.

Further, the end-to-end tunneling in step three can be divided into five steps, specifically:

tunneling the shield transition section until reaching 50-10 m of the tunnel portal;

in the first stage, the shield machine is 5m away from a reinforced area, a tunnel portal is broken, a freezing pipe is pulled out, and a jacket is backfilled;

in the second stage, the shield machine enters the hole for the first time;

in the third stage, the shield enters the hole for the second time, the hole door ring is closed, and the secondary grouting is carried out;

and when the final stage is reached, the shield tunneling machine is pushed to the receiving bracket.

Further, the secondary grouting is double-liquid slurry and is prepared from a liquid A and a liquid B in a ratio of 2:1, wherein the liquid A is prepared from 42.5-grade cement and water in a ratio of 1:1, and the liquid B is 1:3 diluted water glass.

And step three, the concrete steps of separating the steel sleeve to seal the tunnel portal comprise the steps of performing drawknot on the last 10 ring pipes, dismantling a reaction frame, disconnecting the steel sleeve from the steel ring of the tunnel portal, dismantling the upper semicircle of the steel sleeve, dismantling the lower semicircle of the steel sleeve, dismantling a steel plate and finishing the site.

Compared with the prior art, the invention has the beneficial effects that:

(1) the end is reinforced by adopting a freezing method, the stratum reinforced by the freezing method has the advantages of high strength, good water sealing performance and the like, and meanwhile, the cement system is adopted for reinforcement, so that the cement system can bear larger water and soil pressure generated by disturbance or vibration, the reinforcement range is small, the cement system is particularly suitable for construction sites with small construction sites and dense underground pipelines, the balance of soil can be continuously maintained after the opening door is broken through the end wall of the enclosure structure, and the stability of the soil body of the end stratum is ensured.

(2) By adopting the steel sleeve closed receiving construction technology, a water-soil balance environment can be established for shield tunneling construction before the tunnel portal is broken, so that the tunnel portal under a pressure maintaining state is realized after the shield machine enters the steel sleeve, receiving safety of the shield machine is effectively guaranteed, and the method has high safety, reliability and economy.

The method not only can be used for reinforcing the end by combining horizontal freezing and cement system reinforcement, ensuring the stability of the tunnel face when the tunnel portal is chiseled off, and solving the defects of short reinforcing area and poor water stop effect of a steel sleeve shield receiving technology, thereby avoiding the occurrence of serious safety accidents of shield receiving, but also can be used for realizing the tunnel portal in a pressure maintaining state by using a steel sleeve closed receiving construction technology, and most effectively ensuring the receiving safety of the shield machine.

Drawings

FIG. 1 is a schematic plan view of a horizontal freezing method according to an embodiment of the present invention;

FIG. 2 is a detailed drawing of the sleeve driving of the triaxial mixing stub in the embodiment of the present invention;

FIG. 3 is a detailed view of the overlapping of three-axis mixing piles in the embodiment of the present invention;

FIG. 4 is a detailed view of the overlapping of the jet grouting piles in the embodiment of the invention;

FIG. 5 is a flowchart of step three in an embodiment of the present invention;

FIG. 6 is a schematic plan view of the construction of the embodiment of the present invention;

FIG. 7 is a schematic cross-sectional view illustrating the construction of an embodiment of the present invention.

FIG. 8 is a flow chart of steel sleeve installation in an embodiment of the present invention.

FIG. 9 is a schematic view of a mortar base according to an embodiment of the present invention.

Fig. 10 is a schematic drawing of a chain block tube drawing in the embodiment of the invention.

In the figure: 11. pre-burying a steel ring in the tunnel portal; 12. freezing the hole; 21. freezing the reinforced area; 22. a cement-based reinforcement zone; 23. a steel sleeve region; 31. triple pipe high pressure jet grouting pile; 32. reinforcing the first area; 33. reinforcing the second area; 34. a shield tunnel; 35. freezing area; 41. a steel sleeve; 42. a mortar base; 51. a scaffold; 52. a chain block; 53. a trench wall; 54. an orifice tube; 55. freezing the tube.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.

As shown in fig. 1-10, a shield airtight arrival construction method of a freezing method and a cement system combined steel sleeve comprises the following steps:

step one, cement system reinforcement construction:

in this embodiment, the specific operations of the three-axis mixing pile construction steps are as follows:

and (3) guide groove construction: because certain replacement soil is produced during the construction of the triaxial mixing pile, the replacement amount is 50% of the mixing volume, and in order to ensure the normal construction of the triaxial cement mixing pile and meet the requirement of a civilized construction site, the grooves are excavated and the replaced earthwork is timely transported outwards. The depth of the guide groove is 0.9m, the width of the guide groove is 1.2m, and a PC300 excavator is adopted for mechanical excavation.

Drilling construction of the triaxial deep mixing pile: pile position lofting: pile testing is carried out firstly, and formal production can be carried out after all process parameters are qualified. According to the coordinate reference points provided by owners, pile positions are released by field technicians, and the error of the pile positions in the construction process must be less than 20 mm. Secondly, the pile driver is in place: and moving the stirring pile drilling machine to an operation position, and adjusting the verticality of the pile frame to within 3 per mill. The pile machine displacement is uniformly directed by the current flight leader, the field condition must be carefully observed before the pile machine displacement is carried out, the obstacles are found to be cleared in time, and the positioning condition is carefully checked and corrected in time after the pile machine displacement is finished. The pile driver is stable and flat, the flatness of a platform of the pile driver can be detected by a horizontal ruler or a level gauge after the pile driver is moved every time, the vertical positioning observation is carried out on the upright column by a plumb bob to ensure the verticality of the pile driver, the theodolite is frequently checked, the detection frequency of the theodolite is at least once per day, and a professional supervision engineer is required to go to a site for retesting if necessary. And (4) positioning and rechecking the triaxial mixing pile machine after positioning, wherein the deviation value is less than 2 cm. In the engineering implementation process, the positioning pile and the positioning line are strictly forbidden to shift, once the positioning pile and the positioning line are collided to be shifted when the excavator is found to clear the guide groove, the excavator is immediately paid out again, and construction is strictly carried out according to design drawings. Pile machine straightness that hangs down rectifies: the pile frame verticality indicator can adjust the pile frame verticality and check by a plumb theodolite. An iron ring with the radius of 5cm is welded on the pile frame, a plumb bob is hung at the height of 10m, and the verticality of the drill rod is straightened by using a theodolite, so that the plumb bob just passes through the center of the iron ring. Before each construction, the drill rod must be properly adjusted to ensure that the plumb bob is positioned in the iron ring, namely the verticality error of the drill rod is controlled within 3 per mill. Pile length control mark: the control of the pile length of the mixing pile is important, the mark is made on a drill rod before construction, the pile length of the mixing pile is controlled to be not less than the designed pile length, when the pile length changes, the old mark is wiped off, and a new mark is made.

The main engineering quantity is as follows: shield end well reinforcing method

The triaxial mixing pile is calculated according to the reinforced projection area, the comprehensive cement parameter in the projection area of the weak reinforced area (empty pile section) is 7% (namely the full-section cement parameter of each triaxial mixing pile is 7%), and the comprehensive cement parameter in the projection area of the forced solid (solid) is 20% (namely the full-section cement parameter of each triaxial mixing pile is 20%).

Sinking and lifting a drill rod of the pile machine: according to the construction process requirements of the mixing pile, cement slurry is required to be injected into the drill rod during sinking and lifting. The sinking speed of the drill rod is not more than 0.8m/min, the lifting speed is not more than 1m/min, a specially-assigned person is arranged on site to track, detect and monitor the sinking and lifting stirring speed of the pile machine, an obvious mark can be arranged on the pile frame at intervals of 1m, the speed of the drill rod is tested by a stopwatch so as to adjust the speed of the drilling machine in time to achieve the aim of stirring uniformly, the proper continuous stirring and grouting are carried out on the bottom part of the pile for at least 60 seconds, the pile forming uniformity of the cement soil stirring pile is ensured, and the original record of each pile forming is made.

The concrete operations of grouting, stirring, lifting and re-stirring are as follows: and starting the mortar pump, lifting the stirring head at the speed required by calculation after the pure cement slurry reaches the stirring head, performing grouting, stirring and lifting simultaneously to fully mix the cement slurry and the original foundation soil until the cement slurry is lifted to a position 50cm away from the ground or the designed elevation of the pile top, then sinking, re-stirring and lifting, and closing the mortar pump after the cement slurry is lifted to the designed elevation again. The pile body of the mixing pile needs to be uniformly mixed, and the surface needs to be compact and flat. Because the construction of the triaxial mixing pile has large soil replacement amount, the bare soil covering work is done, the field civilized construction is kept, and measures for preventing mud from splashing outside the enclosure are needed when the construction is close to the enclosure in the construction process.

The occlusion construction of the triaxial mixing pile comprises the following specific operations: the lapping of the triaxial mixing pile and the verticality compensation of the formed mixing pile are realized by repeatedly trepanning and drilling single holes of the mixing pile, and the lapping among the piles is realized, so that the end reinforcement effect of the mixing pile is ensured.

in this embodiment, the concrete operations of each step of triple-pipe jet grouting pile construction are as follows:

(1) preparation for construction

Flattening the field: before formal approach construction, carrying out pipeline investigation, determining the position of a pipeline, clearing obstacles within 5M below the ground of a construction site, making protective measures which cannot be cleared, and then leveling and tamping; meanwhile, the positions of construction machinery, a conveying pipeline and a power line are reasonably arranged, and the tee joint of a construction site is guaranteed to be flat.

Pile position lofting: before construction, a total station is used for measuring control points of jet grouting pile construction, stone burying and marking are carried out, after a retest line is qualified, pile positions are arranged on the spot by using a steel ruler and a measuring line, and the pile positions are nailed tightly by using bamboo sticks, one pile is stuck, and the central displacement deviation of a pile hole is ensured to be less than 50 mm.

Thirdly, constructing a pollution discharge and mortar mixing system: 10-20% of slurry return amount can be generated in the construction process of the jet grouting pile, waste slurry is introduced into a sedimentation tank, and clear water after sedimentation can be discharged in a pollution-free manner according to site conditions. The deposited soil is transported away together when the foundation pit is excavated. The sediment and the sewage are uniformly brought into a whole sewage treatment system. The mortar mixing system is mainly arranged near cement, is convenient to operate and mainly comprises mortar mixing equipment, mortar storage equipment and mortar conveying equipment.

(2) Positioning a drilling machine: after the drilling machine is in place, leveling and centering the pile machine, adjusting the verticality of the pile machine, ensuring that a drill rod is consistent with a pile position, the deviation is within 10mm, and the drilling verticality error is less than 0.15%; before drilling, an air compressor and a slurry pump are required to be debugged, so that the equipment can normally operate; and checking the length of the drill rod, and marking a depth line beside the drilling tower by using red paint to ensure that the elevation of the bottom of the hole meets the design depth.

(3) Drilling a guide hole: before the construction of the drilling machine, trial spraying is firstly carried out on the ground, and after the trial running of the drilling machine is normal, the pilot hole drilling is started. The number of drill rod sections needs to be recorded in detail in the drilling process, and the accuracy of the drilling depth is guaranteed.

(4) Pulling out the core barrel and inserting the grouting pipe: and after the hole is led to the designed depth, the rock core pipe is pulled out, and the injection grouting pipe is replaced to be inserted into the preset depth. In the pipe inserting process, in order to prevent the sand from blocking the nozzle, water jetting and pipe inserting are carried out, the water pressure is not more than 1Mpa, so that the pressure is not too high, the hole wall is jetted through, and the high-pressure water nozzle is wrapped by plastic cloth to prevent soil from entering the pipe.

(5) Rotary spraying and lifting: and after the injection grouting pipe is inserted into the designed depth, a slurry pump is switched on, then the slurry is sprayed from bottom to top in a rotating mode, and simultaneously the slurry is cleaned and discharged. When spraying, the rotary spray pipe is lifted gradually after the preset spraying pressure and the gunite are reached so as to prevent the rotary spray pipe from being twisted off. In order to ensure the quality of the bottom end of the pile, when the nozzle sinks to the designed depth, the nozzle rotates at the original position for about 10 seconds, and then the nozzle is lifted by rotary spraying after the hole orifice is normally overflowed. The rotation and lifting of the drill rod should be continuously carried out without interruption, the drilling machine breaks down, the lifting of the drill rod and the rotation should be stopped to prevent pile breakage, the pile is immediately overhauled and cleared, and the time for guniting and rotary spraying of the drill rod should be properly increased within 1.0m of the bottom of the pile in order to improve the quality of the bottom end of the pile. In the rotary spraying lifting process, the rotary spraying parameters can be adjusted according to different soil layers.

(6) Shifting a drilling machine: stopping the rotary spraying when the rotary spraying is lifted to the designed pile top elevation, lifting a drill bit outlet, cleaning a grouting pump and a conveying pipeline, and then moving the drilling machine.

In the present example, the cement-based reinforcement ranges are: the foundation reinforcement length is 10m, the reinforcement width is 3m on each side of the shield tunnel 34 structure, the range of vertical strong reinforcement (reinforcement in the second zone 33) is 3m above and below the shield tunnel 34 structure, the range of the earth surface to the strong upper edge line is a weak reinforcement (reinforcement in the first zone 32), and 2 rows of triple-pipe jet grouting piles are adopted between the reinforcement zone and the station enclosure structure to fill gaps. A circle of stirring pile waterproof curtain is constructed at the outer side of the reinforcing area of the freezing-free reinforcing end head, and 8 emergency dewatering wells are arranged within the range of the waterproof curtain.

As shown in fig. 2-4, the end reinforcement body of the shield well adopts

The triaxial mixing pile is characterized in that the mixing amount of cement in the first reinforcing area 32 is 7%, and the strength is not lower than that of undisturbed soil; the cement addition amount of the second reinforcing area 33 is 20%, and the soil body reinforcing strength index is as follows: the 28-day unconfined compressive strength is not less than 1.0MPa, the permeability coefficient is not more than 1 x 10 < -7 >/cm/s, and the uniformity, the sealing property and the self-standing property of the reinforced soil body are ensured. The cement is ordinary Portland cement above 42.5 grade.

The joint of the waterproof curtain and the enclosure structure is reinforced by adopting 2 triple-pipe rotary spraying piles, and the cement mixing amount is 270kg/m³(ii) a The construction cold joint of the enclosure structure and the reinforced area is reinforced by triple-pipe rotary jet piles, the hole spacing is 500mm, and the cement consumption is 270kg/m³Stirring the reinforced strength index of the jet grouting pile in the corresponding areaAnd (6) mixing the piles. Before construction, pile testing is required so as to determine the construction process and various construction parameters according to the reinforcement effect.

The reinforcement of the mixing pile needs to be carried out before the excavation of the foundation pit, the reinforcement of the jet grouting pile needs to be completed in a station structure, and the reinforcement of the shield is carried out before the propulsion so as to ensure that no water seepage channel is left between the underground wall of the station and the reinforced soil body; before starting, drilling and coring are carried out on the reinforced soil body to detect whether the foundation reinforcement meets the design requirements, and if the design strength cannot be reached, the weak area is immediately reinforced.

in this embodiment, the specific operation of step two is as follows:

(1) positioning, tapping and orifice tube mounting

The freezing holes 12 are arranged according to the construction drawing of the freezing holes 12 according to the construction reference point. Openings are positioned in the slot wall 53 according to the respective hole locations. A J-200 type diamond drilling machine is selected, a diamond coring bit with the diameter of 133mm is used for drilling, when the drilling depth reaches 800mm, the drilling is stopped (a protective layer with the thickness of more than 200mm is reserved), a steel wedge is used for wedging off a rock core, and the orifice pipe 54 is installed after the rock core is taken out. The orifice pipe 54 is processed by a phi 133 multiplied by 5mm seamless steel pipe, and the head part is processed with a fish scale buckle with the length of 250 mm. The orifice pipe 54 is installed by the following method: firstly, a hole is chiseled flat, four expansion screws are installed, then, a sealing object such as hemp thread or cotton thread is wound on a fish scale buckle of a hole pipe 54, the hole pipe 54 is hammered in, the expansion screws are used for tightening, then, nuts are removed, a DN125 ball valve is installed, the ball valve is opened, a hole is formed in the ball valve through a diamond drill bit with the diameter of 110mm, the groove wall 53 is opened all the time, and if the water and sand flow in the stratum is large, the valve is closed in time for grouting.

(2) Orifice device mounting

The orifice device is mounted on the ball valve by screws, and the sealing gasket is added. When the first hole is opened, drilling can be continued without water gushing and sand gushing, but an orifice device is still installed in the subsequent drilling hole to prevent the occurrence of sudden water gushing and sand gushing; if the gushing water and the gushing sand are serious, the water should be stopped by injecting slurry (or double-liquid slurry).

(3) Drill and freezer installation

1) One machine, an MD-60A type drilling machine, torque 2000 N.M and thrust 17KN is used. One BW-250/50 slurry pump was selected, and the flow rate was 200L/min. The total power of the drilling rig and the mud pump is 45 kw.

2) The freezing pipe 55 is used as a drill rod, the freezing pipe 55 is connected by screw threads, the seam is welded to ensure the concentricity and the welding strength, the freezing pipe 55 is used for sealing the bottom of the hole by a screw plug after reaching the design depth, the specific method is to use an extension rod to put the screw plug on the bottom of the hole, and the screw plug is tightened while the back thread is used for removing the thread.

3) The position of a drilling machine is adjusted according to the construction direction requirement of a freezing hole 12 and is fixed, a drill bit is arranged in a hole opening device, a packing is lightly pressed in a packing box, dry drilling is firstly adopted, when drilling is strenuous and the drilling is not carried out, water injection drilling is carried out on the drilling machine, a small valve is opened at the same time, the water outlet and sand outlet conditions are observed, the slurry outlet amount is controlled by using a switch of the valve, the ground safety is ensured, and settlement does not occur.

4) To ensure drilling accuracy, the open hole section is critical. When drilling 2m before, checking the direction of the freezing pipe 55 repeatedly, adjusting the position of the drilling machine, and using a precise compass or a theodolite to detect the situation that the deviation is not problematic, and then continuously drilling.

5) Before the freezing pipe 55 is put into the hole, the pipe is arranged to ensure the concentricity of the freezing pipe 55. After the freezing pipe 55 is put down, the theodolite light inclinometry is adopted for detection, then the depth of the freezing hole 12 is measured again, and the pressure is carried out for leakage test. The leakage testing pressure of the freezing hole 12 is controlled to be 0.8-1.0 MPa, the pressure is stable for 30 minutes and is not changed or the pressure drop in the first 30 minutes is less than 0.05MPa, and the pressure is not reduced to be qualified in the last 15 minutes.

6) A feed tube is inserted into the freezing tube 55. The length of the liquid supply pipe is less than that of the freezing pipe 55 by 150 mm. The de, return sheepfold and freeze tube 55 end caps are then installed.

7) After the freezing pipe 55 is installed, the gap between the freezing pipe 55 and the orifice pipe 54 is sealed with a plugging material, and then the orifice sealing device is removed.

8) The temperature measuring hole construction method is the same as that of the freezing pipe 55.

And step one, cement system reinforcement is mainly determined according to comprehensive analysis and evaluation of end engineering geology, hydrogeology, ground buildings, pipeline conditions, end structures and the like aiming at the periphery so as to ensure the stability of a bottom layer and prevent accidents such as collapse or water burst of an end stratum. And the freezing reinforcement of the second step mainly aims at the portal and is auxiliary reinforcement, the main purpose is water resistance, and the freezing reinforcement and the cement system reinforcement together bear the water and soil pressure.

In this embodiment, the design of the steel sleeve is also included:

1) designing a cylinder body: the cylinder body part is 10500mm long and 6700mm in diameter (inner diameter), and is divided into four sections (each section is 2400mm long), and each section is divided into an upper block and a lower block. The material of the cylinder body is Q235A steel plate with the thickness of 20mm, the periphery of each section of the cylinder body is welded with longitudinal and circumferential rib plates to form a net shape so as to ensure the rigidity of the cylinder body, and the rib plates have the thickness of 15mm, the height of 140mm and the interval of about 560 × 580 mm; the end of each section of cylinder body and the circular arc joint surfaces of the upper section and the lower section are welded with connecting flanges, the flanges are made of Q235A steel with the thickness of 40mm, the connecting parts of the upper section and the lower section and the two sections of cylinder bodies are connected by M30X 908.8 grade bolts, and a rubber gasket with the thickness of 3mm is added in the middle of the connecting parts to ensure the sealing effect.

2) Design of a bracket at the bottom of the cylinder body: the bracket at the bottom of the cylinder body is manufactured into four blocks. The bottom bracket bearing plate is made of a Q235A steel plate with the thickness of 30mm, the rib plate is made of 30mmQ235A steel, and the bottom plate is made of 30mmQ235A steel.

The bottom frame and the lower cylinder are welded into a whole, and the frame plate is welded with the cylinder firstly, then the transverse rib plate is welded, and the bottom plate and the I-shaped steel are welded. After the frame is assembled, the bottom edge of the I-shaped steel is welded with an embedded part of a station bottom plate, the frame needs to be tightly propped against the side wall of the station by using section steel, and the upper part of the steel sleeve is tightly propped against the middle plate beam by using channel steel.

3) Designing a rear end cover: the rear end cover is a plane cover, the material is Q235A steel plate with the thickness of 30mm, 4 steel plate rib plates with the thickness of 30mm and the height of 500mm are welded on the plane annular plate, and the plate is welded on the rear end cover in a # -shaped manner. The rear cover edge flange and the steel sleeve end flange are connected by M30 × 1308.8 grade bolts.

4) Designing a reaction frame: the steel sleeve stress column is made of 400 multiplied by 400HW section steel with 20mm steel plates welded on both sides. The support column is made of 300 multiplied by 300 square steel, and two ends of the support column are welded with 20mm steel plates. The diagonal brace is made of I20I-shaped steel. One end of the stress column is tightly leaned on the end well bottom plate, and the other end of the stress column is leaned on the station middle plate. One end of the inclined strut is firmly welded with the embedded part of the station bottom plate, and the other end of the inclined strut is firmly welded with the stress column. After the stress column is positioned, a 400t jack is used for jacking the plane cover and the support column to eliminate the installation gap from the tunnel door to the rear cover plate. The reaction frame consists of an upper cross beam, a lower cross beam and a vertical column. The structure of the upper cross beam is a box body structure, the main stress plate is a 30mm steel plate, the rib plates are 20mm steel plates, the materials are Q235-A steel, and the cross section size of the box body structure is 700mmX500 mm; the lower cross beam is of a box body structure, the main stress plate is 30mm, the rib plates are 20mm steel plates, the materials are Q235-A, and the cross section size of the box body structure is 250mmX500 mm; the upright post is of a box body structure, the main stress plate is a 30mm steel plate, the rib plate is a 20mm steel plate, the materials are Q235-A steel, the cross section of the box body structure is 700mmX500mm, and the structure diagram is the same as that of the upper cross beam.

As a preferred embodiment, before the second step, the arrangement of the freezing holes 12 and the setting of horizontal freezing parameters are required, wherein the arrangement of the freezing holes 12 is as shown in FIG. 1, the freezing holes 12 are arranged at an angle close to the horizontal according to the design of the freezing curtain, and the number of the freezing holes 12 is 53 per portal. The cylinder freezing holes 12 are circularly arranged along the opening phi 7.5m, the distance between the openings is 0.76m (arc length), the number of the freezing holes 12 is 31, and the length of the freezing holes 12 is 3 m. The specification of the freezing pipe 55 is phi 89 multiplied by 8 mm. The plate freezing holes 12 are circularly arranged along the openings phi 5.1m and phi 2.7 m. Wherein the hole pitch of the middle ring of holes is 1.135m, the number of the freezing holes 12 is 14, and the length of the freezing holes 12 is 3 m; the hole spacing of the inner ring holes is 1.172m, the number of the freezing holes 12 is 7, and the length of the freezing holes 12 is 3 m; 1 freezing hole 12 is arranged in the center of the opening, and the length of the freezing hole 12 is 3 m. 5 temperature measuring holes are formed, and the depth is consistent with that of freezing. The horizontal freezing holes 12 are drilled in the sequence that the outer ring holes are drilled first, and then the freezing holes 12 in the door ring are drilled after the outer ring holes are drilled.

The horizontal freeze parameters include: the temperature of saline water in the positive freezing period is-28' C; maintaining the temperature in the freezing period to be-25 ℃ to-28 ℃; the distance Lmax between the final holes of the peripheral freezing holes 12 is less than or equal to 1000mm, the time for circling the freezing curtain is 20 days and the time for reaching the designed thickness is 40 days according to the development speed of 25mm every day; the active freezing time was 35 days in total; 53 freezing holes 12 are arranged; the number of the temperature measuring holes is 5, the depth is 3.0m, the temperature measuring holes are generally fixed at the positions with larger distance between the final holes, and the positions can be adjusted according to actual construction.

As a preferred embodiment, before the third step, preparation work for reaching the construction needs to be performed, specifically comprising attitude measurement of the shield tunneling machine, monitoring and control, tunnel portal chiseling, horizontal freezing pipe extraction, steel sleeve backfill and tunnel portal tensioning device installation.

In this embodiment, the specific operation of the shield machine attitude measurement is as follows:

(1) and (3) rechecking measurement at the position of the hole door: in order to accurately master the construction condition of the arriving portal, the shield arriving at the portal is rechecked and measured before the shield is run through by 300m, and the measurement items comprise: the center position deviation of the portal, the full circle radius of the portal and the like. And if necessary, carrying out corresponding treatment on the tunnel portal or correspondingly adjusting the shield attitude according to the measurement result.

(2) And (3) contact measurement: the measurement adopts a three-wire method double-triangle or wire direct transmission method, and the error in the measured mean value of the azimuth angle of the starting edge of the underground wire can meet the requirement of less than or equal to +/-2.0' according to the standard requirement and the past experience.

(3) Adjusting the shield attitude: the shield machine receives the front 100m section, namely strengthens the shield attitude and the tunnel linear measurement, discusses and makes a shield attitude adjustment scheme according to the shield attitude measurement and tunnel portal re-measurement results, and corrects the deviation in time to ensure that the shield smoothly enters the shield receiving well. The measurement contents comprise a orientation, b main guide line, c measurement segment position and d trend deviation. Through measurement, the axis control of the shield tunneling is strengthened to the section before receiving, so that the notch plane deviation of the shield tunneling machine meets the requirements when the shield tunneling machine enters a shield receiving well: the plane is less than or equal to plus or minus 20mm, and the elevation is less than or equal to plus or minus 20 mm; when the shield penetrating posture is determined, the condition that the shield is likely to sink due to the fact that the construction progress is slow when the shield arrives is generally considered, the shield can be conveniently and smoothly pushed onto the receiving bracket, and the shield posture can be gradually raised by 20mm 30m before penetrating.

(4) Attitude measurement of the first 20 rings of arrival: and stopping tunneling after the shield machine tunnels to the rest 20 rings, rechecking the shield posture, determining the shield machine posture, and adjusting the shield posture by combining the tunnel portal position to ensure the normal receiving of the shield machine.

The specific operation of monitoring control is as follows: in order to ensure the safety of surrounding and underpassing buildings, pipelines, roads and the like during construction and the construction safety of a shield interval structure, the project establishes a special organization, carries out information construction, monitors and measures the whole construction process and feeds back information, and ensures the construction safety of engineering. The main purposes of measurement are as follows:

(1) the method comprises the steps of monitoring the stress and deformation conditions of soil body media, tunnel structures (mainly segment lining) and surrounding environments among line sections, mastering the dynamic conditions, verifying the design effect of the tunnel structures (mainly segment lining), and ensuring the stability of the tunnel structures and the safety of ground and surface buildings and underground pipelines. And the environmental impact which may be generated by engineering construction is comprehensively monitored. And information is provided for daily management of construction, and construction safety is ensured.

(2) Providing a basis for judging the basic stability of the tunnel structure and determining the construction time of the main structure of the shield interval.

(3) By monitoring and measuring, the scientificity and rationality of the construction method and the construction means are known, and the defects in the theoretical analysis process are made up by using the result of field actual measurement, so that the construction method can be adjusted in time, and the construction safety is ensured.

(4) Through the analysis and processing of the measured data, the change rule of the stability of the tunnel structure is mastered, and the design parameters of the main structure of the tunnel are modified or confirmed. The subsidence of the ground surface is controlled, and the smooth ground traffic and the normal use of ground buildings are ensured.

(5) Some underground engineering rules and characteristics expressed and reflected under the engineering conditions are known through monitoring and measuring, and reference and guidance functions are provided for development of similar engineering in future.

(6) And a section is arranged along the central line of the tunnel every 20m within the range of 100m of the entrance and exit, part of the section is encrypted, two measurements are carried out every day in the receiving process, and the data are fed back in time once in the morning and at night.

The specific operation of the portal chiseling is as follows: the tunnel portal chiseling method comprises the following three steps: the scaffold 51 is set up, and the horizontal hole detection and the chiseling of the tunnel door are carried out.

Firstly, erecting a scaffold 51: before the portal chisels out, need to set up two rows of three-layer scaffold 51 before the portal, every row sets up four pole settings, three horizontal poles, the cloth is apart from being 1.5m, the pole of sweeping the floor apart from ground 18cm, scaffold 51 sets up highly about 7m, scaffold 51 takes up and adopts the dish knot formula support, should set up corresponding bridging and bracing and prevent that the production from rocking in the work progress, it need lay the pavement board as construction platform to set up after the completion, it protects to face frontier defense well, it can carry out the portal chiseling out to wait to check to receive the check back.

II, horizontal hole probing: the method is used for further accurately judging the conditions of the geotechnical geology and the underground water of the receiving end and verifying the reinforcing strength of the end well. Before the tunnel portal is chiseled, 9 horizontal geological drill holes with the diameter of 50mm are drilled at 9 positions of the measured tunnel body. And drilling a hole with the depth of 1.5m, penetrating the enclosure structure, entering a reinforcing area, and checking the end reinforcing quality. If water leakage and sand leakage exist, the hole door can be broken after grouting reinforcement is carried out on the inspection hole.

Thirdly, chiseling the hole door: and when the freezing temperature reaches the design requirement, chiseling the portal, wherein the portal is chiseled for three times. The hole door is chiseled out manually. The opening is divided into 9 sections. (1) And chiseling out the surface concrete, simultaneously cutting out the surface reinforcing steel bars, and chiseling out the surface concrete, the surface reinforcing steel bars sequentially from top to bottom, the middle and the two sides. (2) Chiseling the underground diaphragm wall concrete, operating according to the upper part, the lower part, the middle part and the two sides, simultaneously timely clearing the concrete slag, and hoisting the concrete slag out of a wellhead by a crane or other modes. (3) And cutting off the rest reinforcing steel bars and the rest concrete after chiseling off the concrete of the diaphragm wall, and completely cutting off the reinforcing steel bars invading the excavation contour line when cutting off the reinforcing steel bars.

The following remarks are made in the chiseling process: after an abnormal condition is found, the wall is quickly supported by the wood boards and the steel pipes, and the soil outside the wall is prevented from collapsing. And then grouting reinforcement is carried out from the outside of the building envelope as soon as possible. Secondly, if the pressure of the soil body is larger, the prefabricated reinforcing mesh is quickly welded with the reinforcing steel bars of the building enclosure structure, and then the wood plates and the steel pipes are used for supporting and stabilizing. And then grouting reinforcement is carried out on the periphery of the enclosure structure, and grouting reinforcement is carried out in the tunnel door. And thirdly, after the portal is chiseled off, a displacement observation point is arranged on the reinforcing body, and the safety state of the portal is monitored every day. Fourthly, construction is strictly carried out according to the requirement of high-altitude operation, and safety ropes are required to be worn for the operation more than 2 m. Fifthly, when the freezing construction tunnel door is chiseled, the freezing pipe 55 needs to be protected.

The concrete operation of steel sleeve backfill is as follows: after the freezing pipe 55 is pulled out, sundries in the barrel body are cleaned in time, and soil is filled into the barrel body after the cleaning is finished. When the steel sleeve is filled with the filler, mainly the soil excavated by the shield, the soil body is improved if necessary, and the mobility of the soil body is enhanced. In order to convey the filler into the steel sleeve, a conveying pipeline is led from the ground to the steel sleeve through a station end head, a 400mm pipeline is adopted for connection, a funnel is arranged on the ground, and the filler is directly conveyed into the steel sleeve from the funnel. If the filler is not smoothly conveyed in the filling process, the filler can be flushed down by adopting a flushing mode.

The concrete operation of the installation of the tunnel portal tension device is as follows: because tunnel link up back shield place ahead does not have the counter-force, hydro-cylinder thrust is less, for preventing that the section of jurisdiction from producing after losing back shield section of jurisdiction support or shield thrust and lax and leading to the section of jurisdiction circumferential weld to open, 20 vertical straining device of ring canal piece installation at last, install 4 groups altogether, the top is two sets of, it is respectively a set of to control the waist, every section of jurisdiction of assembling ring just adopts the channel-section steel to be connected the section of jurisdiction assembled with last ring canal piece, impel a ring and connect a ring, the junction between every ring channel steel should weld firmly, guarantee to have sufficient intensity.

As a preferred embodiment, the concrete steps of installing and fixing the steel sleeve in the third step are that personnel, materials and equipment are in place, the steel sleeve is positioned on a defense line, the transition connecting plate is hoisted to go into the well, the transition connecting plate is transported to a working surface and is assembled in place, the transition connecting plate and the portal steel ring are welded, a plurality of force-transmitting frames are hoisted to go into the well in sequence, the end cover plate is hoisted to go into the well in sequence, the steel sleeve is installed and connected with the steel sleeve, the steel sleeve is integrally moved and connected with the transition connecting plate, a counter-force system is installed, the sleeve is reinforced, a mortar base 42 is poured, and filling materials and shields are pushed to receive the steel sleeve.

In this embodiment, the specific steps of installing the reaction force system include:

reaction frame installation: the steel sleeve stress column is made of 400 multiplied by 400HW section steel with 20mm steel plates welded on both sides. The support column is made of 300 multiplied by 300 square steel, and two ends of the support column are welded with 20mm steel plates. The diagonal brace is made of I20I-shaped steel. One end of the stress column is tightly leaned on the end well bottom plate, and the other end of the stress column is leaned on the station middle plate. One end of the inclined strut is firmly welded with the embedded part of the station bottom plate, and the other end of the inclined strut is firmly welded with the stress column. After the stress column is positioned, a 400t jack is used for jacking the plane cover and the support column to eliminate the installation gap from the tunnel door to the rear cover plate. In the process, whether each inclined strut of the stress column is loosened or not and whether each section of flange connecting bolt is loosened or not are checked. After the completion, the joints of all parts are checked, the joint installation places of all the parts are checked, the connection integrity is ensured, particularly, the welding between the transition connecting plate and the portal ring plate is checked to see whether spot welding or floating welding exists or not for checking the connection between the upper semicircle and the lower semicircle of the steel sleeve and the joint parts, and the hidden danger is found and the timely treatment is needed.

Connecting a transition connecting plate of the steel sleeve with a tunnel portal annular plate: and (4) after the transition connecting plate is transferred and transported to the working face to be assembled, retesting the central line through the measuring group, and welding the portal ring plate and the transition connecting plate after confirming that no fault exists. After the transition connecting plate of the steel sleeve is contacted with the portal ring plate, whether the two planes can be connected or not is checked, and the situation that the portal ring plate is deformed or has large flatness deviation in the pre-embedding process is possible, so that the situation that the transition connecting plate cannot be closely attached to the portal ring plate at some places is possible to occur, and at the moment, steel plates are required to be filled in the gaps and firmly welded with the transition plate, and the gaps are required to be blocked as much as possible. And after the portal ring plate is determined to be completely attached to the transition plate, the transition plate is fully welded on the portal ring plate.

Thirdly, supporting and installing:

1) mounting of upper support of cylinder

And after the steel sleeve and the portal annular plate are welded, the upper support of the cylinder body is installed after inspection and confirmation. Each side of the steel sleeve is provided with 3 transverse supports which are propped against the middle plate girder.

2) Installation of reaction frame and steel sleeve rear end cover support

The shield initial reaction frame is tightly leaned on the end well negative second-layer ring frame beam and the bottom cross beam. The shield initial reaction frame is tightly leaned on the end well negative second-layer ring frame beam and the bottom cross beam. For reaction frames

The steel pipe is used as an inclined strut and is tightly propped against the station bottom plate. After the reaction frame is positioned, firstly, a plurality of 100t jacks are used for jacking a plane cover and the reaction frame, after an installation gap from a tunnel door to a rear cover plate is eliminated, 9 rows of 300 multiplied by 300mm supporting columns are uniformly distributed on the upper portion and the lower portion of the reaction frame and tightly propped against a plane plate of a rear end cover, the supporting columns and the reaction frame are tamped and welded by supporting wedge blocks, the supporting inclined supports and a bottom plate embedded part are firmly welded, the positions of welding seams are checked, and no hidden dangers such as slag inclusion, insufficient welding and the like are ensured. In the process, whether the supports of the reaction frame are loosened and whether the flange connecting bolts of the sections are loosened are checked.

After the support installation is completed, the firmness of the support of the left bracket, the right bracket and the reaction frame is checked.

And (4) checking the position of the steel sleeve, and retesting the position of the installed cylinder body to determine whether the position coincides with the center line of the shield machine.

3) Connection and fixation of steel sleeve and main structure

And after the reaction frame is reinforced, prestress is constructed, all parts of the steel sleeve are compacted, and the bottom frame of the steel sleeve is welded and connected with the embedded steel plate on the bottom plate. And a steel plate is embedded in the station bottom plate, and the bottom frame is welded with the embedded steel plate after the steel sleeve completes the force application of the reaction frame.

In a preferred embodiment, as shown in fig. 9, the concrete step of casting the mortar bed 42 is to cast a 15cm thick C20 mortar bed 42 within 60 ° of the middle position of the bottom of the steel sleeve.

In a preferred embodiment, the concrete steps of the steel sleeve sealing inspection in the step three include the steps of inspecting the roundness of the steel sleeve, inspecting the sealability of the steel sleeve, and inspecting the weld of the steel sleeve.

In this embodiment, the concrete operations of the steel sleeve roundness check are as follows: before the shield machine is used, the roundness of the integral steel sleeve is checked, if necessary, a manufacturer checks the roundness to ensure the roundness, and accidents such as displacement and deformation of the steel sleeve caused by collision between a shield body and the steel sleeve due to uneven distance between the shield machine and the steel sleeve when the shield machine enters the steel sleeve are avoided.

The specific operation of the leak tightness check of the steel sleeve is as follows: the steel sleeve is divided into a plurality of blocks, a rubber gasket is added between each block, the quality of the rubber gasket must be strictly controlled, damage or leakage is avoided, and slurry leakage and pressure relief are avoided. In addition, all parts of the steel sleeve are connected by adopting bolt connection, the bolt connection surface is also required to be checked, and the part of the connection surface which is deformed or damaged is repaired, so that a leak is avoided. The connecting bolt is an important component for ensuring the tight connection of all parts, and the quality and the quantity of the connecting bolt are ensured before use, so that the connection strength of all parts is ensured. After the steel sleeve is assembled, the air is added into the sleeve body to check the tightness, the air pressure is 0.2Mpa, if the air pressure is kept at 0.18Mpa within 12 hours, the receiving requirement of the steel sleeve can be met, if the air pressure is less than 0.18Mpa, an air leakage part is found out, the sealing quality of the air leakage part is checked and repaired, and then the pressure test is carried out again until the pressure test requirement is met.

The concrete operation of the steel sleeve weld inspection is as follows: the steel sleeve is formed by welding steel plates, welding seams of all parts of the steel sleeve are required to be comprehensively checked before use, damaged welding seams are subjected to repair welding, the quality of the welding seams is ensured, and the integrity of the whole steel sleeve is ensured.

In this embodiment, the steel sleeve needs to be fixed after the sealing inspection, and the specific operations are as follows: the interval receiving line types are straight line segments, when the steel sleeve is positioned, two control lines of the center line of the steel sleeve frame and the center line of the line are required to be superposed, and the error is not more than 1 cm. Before the installation of the steel sleeve begins, the line centre, i.e. the centre line of the steel sleeve, is first determined in the foundation pit. And after the steel sleeve is installed, retesting the position of the sleeve body, and checking whether the position of the sleeve body coincides with the center line of the shield tunneling machine. And after the position and the elevation of the steel sleeve meet the requirements, the steel sleeve and the side wall of the end well are supported and positioned by 20# H-shaped steel, and the welding is firm.

As a preferred embodiment, the specific steps of pulling out the freezing pipe in the third step include brine heating, brine circulation, and trial pulling through several chain blocks 52. In this embodiment, the specific operations of pulling out the horizontal freezing pipe are as follows: and (4) drawing the pipe by utilizing a manual local thawing scheme, and starting to draw the pipe after the portal is chiseled. The specific method comprises the following steps: when the frozen soil around the freezing pipe 55 is melted to 50mm to 80mm by circulating hot brine in the freezer, the pipe drawing is started as shown in fig. 10.

(1) Heating saline water: the brine is stored in a brine tank of about 1m3 and heated by 18 sets of 5kw heating wires.

(2) Brine circulation: circulating the brine by using a brine pump with the flow rate of more than 50m3/h, and circulating the brine for about 10 minutes at the temperature of 40-50 ℃ to perform test drawing while circulating.

In the tube drawing process, a proper amount of heat circulation is needed for the freezing tube 55 to prevent the freezing wall from excessively melting; the filling quality of the freezing holes 12 is ensured to prevent sedimentation.

(3) Two 10-ton chain blocks 52 are used for trial drawing, when the chain blocks are drawn up for about 0.5m, the circulation of hot brine can be stopped, and the brine in the pipe is discharged by using an air compressor to press air. The freezing pipe 55 cannot be tightened when being pulled out, the freezing pipe 55 is rotated frequently when being pulled out, the freezing pipe 55 cannot be pulled out firmly, and if the freezing pipe 55 cannot be pulled out, the hot saline is circulated continuously to be thawed until the freezing pipe 55 is pulled out.

As a preferred embodiment, the step three reaching end tunneling can be divided into five steps, specifically:

and (3) tunneling the transition section of the shield until the transition section reaches 50-10 m of the tunnel opening, wherein the tunneling speed and the soil bin pressure of the transition section are basically the same as those of the transition section at ordinary times, the tunneling speed is controlled in a conventional mode and is slightly reduced to 15-20 mm/min from 30-50 mm/min of the original normal section. And ending the tunneling of the transition section until the distance is about 10 meters away from the tunnel portal, and starting to enter a receiving operation. During the construction, attention should be paid to adjusting the posture of the shield machine, so that the tunneling direction of the shield machine is consistent with the original designed axis direction as much as possible, and the axis control precision during tunneling is +/-20 mm;

in the first stage of arrival, the shield machine is 5m away from a reinforcement area, a tunnel portal is broken, the freezing pipe 55 is pulled out, the sleeve box is backfilled, the receiving end head is frozen and reinforced, in order to prevent the shield machine from entering the freezing area 35 and being frozen when the tunnel portal is broken, the tunnel portal needs to be broken in advance, the freezing pipe 55 in the tunnel ring is pulled out after the tunnel portal is broken, the freezing pipe 55 outside the tunnel ring is reserved, and the operation is continued; after the tunnel portal is completely chiseled, timely cleaning concrete slag, laying a base, sealing a steel sleeve man-cabin door after cleaning is finished, backfilling soil by using a feeding hole, and continuously propelling the shield after the sleeve is filled with the soil;

and in the second stage, the shield tunneling machine enters the hole for the first time, when the shield tunneling machine tunnels in the freezing area 35, the cutter head is kept to rotate continuously, the cutter head is required to rotate once every 3 minutes to prevent the cutter head from being frozen, when the shield body pushes out the inner lining wall for 7m, the tunneling is stopped, and double-fluid slurry is injected into the shield tail spacer ring by using the segment grouting holes (15 holes per ring) to form a hoop. And each hoop grouting adopts hole-separated circulating pressure grouting. Namely, the holes of No. 1, 3, 5, 7, 9, 11, 13 and 15 are firstly injected into 15 holes, then the holes of No. 2, 4, 6, 8, 10, 12 and 14 are injected into the 15 holes, the single hole injection amount is 0.3m3, the bottom injection pressure is not more than 0.4MPa, and the upper injection pressure is not more than 0.35 MPa. Performing double control of pressure and volume, namely when the pressure injection volume reaches 0.3m3, if the pressure does not exceed the requirement, finishing single-hole grouting; if the grouting amount does not reach 0.35m3, but the grouting pressure reaches the requirement, finishing the single-hole grouting;

and in the third stage, the shield enters the hole for the second time, a hole gate ring is sealed, secondary grouting is carried out, after shield tunneling construction and hole gate plugging grouting are finished, the grouting effect is detected through a detection valve on the prefabricated steel sleeve, and if leakage exists, grouting is continued until no leakage exists, and then hole gate sealing is carried out. The hole door plugging is implemented by adopting an external sealing method. Blocking and plugging in a block manner from top to bottom, and cutting off a section of the transition ring to recover a section until the blocking is finished;

and when the final stage is reached, the shield machine is pushed to the receiving bracket, and when the sealing of the portal ring is completed, the shield machine continues to be pushed until the shield machine completely pushes the receiving bracket. After the segments of the shield tunnel 34 are assembled, the shield machine does not reach the preset position of the bracket, and the shield machine is enabled to continue to advance by continuously installing temporary segments (1A-type concrete segment is installed at the right lower part of each ring) until the shield machine reaches the preset position of the bracket.

In a preferred embodiment, the secondary grouting is a two-fluid slurry prepared from a fluid a and a fluid B2: 1, wherein the fluid a is prepared from 42.5-grade cement and water 1:1, and the fluid B is 1:3 diluted water glass, and in the present embodiment, the secondary grouting slurry is prepared as follows:

after each two hoops are pressed and injected, single-liquid-slurry filling (cement with a water-cement ratio of 1:1 and 42.5 grade) is pressed and injected between the two hoops, the grouting pressure is not more than 0.4MPa, the single-hole grouting amount is 0.2m3, and double control of pressure and amount is realized. And strictly monitoring the deformation of the tunnel during injection. And starting secondary hole feeding when the slurry reaches the set strength.

As a preferred embodiment, the concrete steps of separating the steel sleeve to seal the tunnel portal in the step three are to perform drawknot, reaction frame dismantling, steel sleeve and tunnel portal steel ring disconnection, steel sleeve upper semicircle dismantling, steel sleeve lower semicircle dismantling, steel plate dismantling and site arrangement on the last 10 ring pipes.

In this embodiment, the concrete operations of the steps of closing the tunnel door by the separating steel sleeve are as follows:

(1) the last 10 loop pieces were tied first to prevent the piece from loosening.

(2) Gas cutting demolition of the support of the reaction frame, disassembly of the reaction frame

1) The upper cross beam is matched and disassembled by a chain block 52 through a lifting hook pre-embedded in a station floor slab, and a bottom plate is placed;

2) the two upright posts are also laid down by matching the lifting hooks of the floor slab with the chain block 52;

3) the cross beam and the upright post of the reaction frame are carried to the wellhead by a forklift and then are hoisted out by a crane.

(3) And after the steel sleeve is disconnected with the portal steel ring, the steel sleeve is pulled backwards to the shield wellhead by using a pushing traction device and a steel strand. The steel sleeve is stressed at the 4 th force transmission frame base side and is connected through a bracket, and the jacking oil cylinder is fixed at the side, close to the station, of the shield well and is connected with the embedded part through the bracket.

(4) Disassembling and assembling upper semicircle of steel sleeve

Only one of the two can be removed at each time, the two are removed from the force transmission frame 1, and the portal crane is used for hoisting and taking out the well.

(5) Disassembling and assembling lower semicircle of steel sleeve

(6) Dismantling of steel plate

And cutting off the planted bars, coiling the steel plate to the wellhead by using a forklift, and lifting one steel plate out by using a gantry crane.

(7) Site arrangement

Cleaning up the garbage on the bottom plate, discharging the elevation of the bottom surface of the track of the battery car walking track, pouring concrete, building a platform after the strength is equal, paving the track, and performing edge protection.

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.

Claims

1. A shield airtight arrival construction method of a freezing method and a cement system combined steel sleeve is characterized in that: the method comprises the following steps:

step one, cement system reinforcement construction:

2. The shield airtight arrival construction method of the freezing method and cement system combined steel sleeve as claimed in claim 1, wherein: before step two, the freeze hole arrangement and the setting of horizontal freeze parameters are required.

3. The shield airtight arrival construction method of the freezing method and cement system combined steel sleeve as claimed in claim 1, wherein: before the third step, the construction preparation work is required to be carried out, and the method specifically comprises the steps of shield tunneling machine attitude measurement, monitoring control, tunnel portal chiseling, horizontal freezing pipe pulling out, steel sleeve backfilling and tunnel portal tensioning device installation.

4. The shield airtight arrival construction method of the freezing method and cement system combined steel sleeve as claimed in claim 1, wherein: and step three, the concrete steps of installing and fixing the steel sleeve comprise that personnel, materials and equipment are put in place, the steel sleeve is positioned to prevent the wire, the transition connecting plate is hoisted and lowered into the well, the transition connecting plate is transported to a working surface and assembled in place, the transition connecting plate and the portal steel ring are welded, a plurality of force-transmitting frames are hoisted and lowered into the well in sequence, end cover plates are sequentially assembled and connected, the steel sleeve is hoisted and lowered into the well, the steel sleeve is installed and connected, the steel sleeve is integrally moved and connected with the transition connecting plate, a counter-force system is installed, a cylinder body is reinforced, a mortar base is poured, and filling materials and a shield are pushed into the steel sleeve for receiving.

5. The shield airtight arrival construction method of the freezing method and the cement system combined steel sleeve as claimed in claim 4, wherein: the concrete step of pouring the mortar base is to pour a C20 mortar base with the thickness of 15cm in the range of 60 degrees at the middle position of the bottom of the steel sleeve.

6. The shield airtight arrival construction method of the freezing method and cement system combined steel sleeve as claimed in claim 1, wherein: and the concrete steps of the steel sleeve sealing inspection in the third step comprise the steps of inspecting the roundness of the steel sleeve, inspecting the sealing performance of the steel sleeve and inspecting the welding seam of the steel sleeve.

7. The shield airtight arrival construction method of the freezing method and cement system combined steel sleeve as claimed in claim 1, wherein: and step three, the concrete step of pulling out the freezing pipe comprises brine heating, brine circulation and trial pulling through a plurality of chain blocks.

8. The shield airtight arrival construction method of the freezing method and cement system combined steel sleeve as claimed in claim 1, wherein: and step three, the arrival end tunneling can be divided into five steps, specifically:

in the second stage, the shield machine enters the hole for the first time;

9. The shield airtight arrival construction method of the freezing method and cement system combined steel sleeve as claimed in claim 8, wherein: the secondary grouting is double-liquid slurry and is prepared from a liquid A and a liquid B in a ratio of 2:1, wherein the liquid A is prepared from 42.5-grade cement and water in a ratio of 1:1, and the liquid B is 1:3 diluted water glass.

10. The shield airtight arrival construction method of the freezing method and cement system combined steel sleeve as claimed in claim 1, wherein: and step three, the concrete steps of separating the steel sleeve to seal the tunnel portal comprise the steps of performing drawknot on the last 10 ring pipes, dismantling a reaction frame, disconnecting the steel sleeve from the tunnel portal steel ring, dismantling the upper semicircle of the steel sleeve, dismantling the lower semicircle of the steel sleeve, dismantling a steel plate and finishing the site.