CN114086968B - Construction method for undermining existing building undercut tunnel - Google Patents

Abstract

The application relates to a underpass existing building undercut tunnel construction method relates to the technical field of tunnel construction, including grouting reinforcement, supporting mechanism reinforcement and tunnel construction, the tunnel construction includes: and (3) pipe shed construction: constructing a concrete guide wall at a tunnel portal to be excavated, penetrating a guide pipe around the top of the guide wall, grouting, and penetrating the guide pipe through the bottom of the existing building and inserting the guide pipe into a rock mass at the upper part of a tunnel; excavating and supporting a tunnel body; and (5) secondary lining of the tunnel. The application has the advantage of high-efficiency construction under the condition of guaranteeing the construction safety of houses and tunnels.

Description

Construction method for undermining existing building undercut tunnel

Technical Field

The application relates to the technical field of tunnel construction, in particular to a method for constructing a subsurface tunnel of an existing building.

Background

Along with the increasing subway construction in China, the tunnel crossing of the existing building is difficult to avoid. At this time, the existing building needs to be reinforced, and the existing house foundation reinforcing method at present comprises the following steps: (1) The method for enlarging the foundation bottom area adopts concrete or reinforced concrete to enlarge the existing foundation bottom surface and reduce the contact pressure acting on the foundation; (2) The foundation deepening method is to set a pier foundation under the original foundation so that the foundation is located on a better soil layer; (3) pile-adding and underpinning the original foundation; and (4) grouting reinforcement.

The related technology is disclosed in the patent application of the invention with the publication number of CN109944593A, and discloses a method for reinforcing an existing building by downwards penetrating a shield tunnel, reinforcing piles are constructed on two lateral sides of the existing building, anchor cables are penetrated in soil bodies between the existing building and the shield tunnel, the anchor cables are tensioned to the design strength, two ends of the anchor cables are fixed on the reinforcing piles, grouting is carried out on soil bodies below the existing building, and the grouting wraps the anchor cables to form a reinforced concrete structure.

As shown in fig. 1 and 2, when the section tunnel 1 is penetrated down and located in the existing building F in downtown area, the tunnel vault is small in distance d <5m from the house foundation, and the foundation of the existing building is a strip stone foundation, and under the condition that the resident of the existing building is not moved, the tunnel construction method cannot meet the requirement of efficient and safe construction.

Disclosure of Invention

In order to solve the problem that the existing building cannot be efficiently and safely constructed when the tunnel is penetrated down, the application provides a method for constructing the underground excavation tunnel of the existing building.

The application provides a construction method for a subsurface tunnel penetrating through an existing building, which adopts the following technical scheme:

a method for constructing a subsurface tunnel of an existing building by underpass comprises

S1, grouting reinforcement:

s11, grouting and reinforcing a curtain: solidifying and sealing soil near the existing building to form a curtain;

s12, soil grouting reinforcement: reinforcing a soil layer below 2m of the ground of the existing building;

s13, grouting and reinforcing a rock-soil body: grouting and reinforcing soil below 2m of the existing building ground and rock mass at the top of the tunnel, so that a solidified whole is formed by the foundation soil and the rock mass;

s2, reinforcing a bearing mechanism:

s21, installing a supporting component below an existing building;

s22, performing steel pipe pile construction near the existing building, and pouring joists at the tops of the steel pipe piles;

one end of the supporting component is fixed in the joist, and the other end of the supporting component is fixed in the rock mass;

s3, tunnel construction:

s31, pipe shed construction: constructing a guide wall of concrete at a tunnel portal to be excavated, penetrating a guide pipe around the top of the guide wall, grouting, and penetrating the guide pipe through the bottom of an existing building and inserting the guide pipe into a rock mass at the upper part of a tunnel;

s32, excavating and supporting a tunnel body;

s33, secondary lining of the tunnel.

By adopting the technical scheme, the curtain grouting ensures that soil near the civil house foundation is consolidated and sealed to form the curtain, so that the second-step soil grouting and the third-step rock grouting are prevented from running. Soil body grouting reinforcement improves shear strength indexes of soil body of civil house foundation, and rock soil body grouting reinforcement enables the soil body and rock body of the foundation to form a relatively solidified whole, so that deformation influence of tunnel excavation on a ground building is reduced.

The support component provides support for the civil house, transmits force to the joist, and the steel pipe pile supports the joist to reduce sedimentation. Due to the effect of the bearing mechanism, the stability of the building structure and the construction safety of the new line can be effectively ensured when the new line is constructed by penetrating the building structure.

The pipe shed construction makes one layer of supporting structure more between the tunnel to be excavated and the existing building, so that the influence on the upper-layer existing building is reduced when the tunnel is excavated.

Optionally, in step S32, during construction, an advance conduit is inserted into the arch of the excavated section for grouting, the advance conduit is driven into the rock stratum along the periphery of the excavation outline of the tunnel at an external insertion angle of 10-15 degrees, and the advance conduit is annularly and alternately arranged above the arch of the tunnel to be excavated.

By adopting the technical scheme, the structural strength of the top of the tunnel to be excavated is reinforced, and the construction safety is improved.

Optionally, when the tunnel body is excavated, grouting pre-reinforcement treatment is carried out on the tunnel face, then contour holes are drilled along the contour line of the tunnel to form a closed area, then a plurality of splitting holes are drilled in the closed area, and then splitting rods are inserted into the splitting holes from top to bottom to crack rock bodies.

By adopting the technical scheme, the disturbance to surrounding rock is reduced, and the construction safety is improved.

Optionally, a reinforcement cage is arranged in the conduit in a penetrating way.

By adopting the technical scheme, the bending resistance of the catheter is improved, and when the end part of the catheter abuts against the rock stratum and is blocked, external force can be applied to the catheter to insert the rock mass.

Optionally, the grouting of the guide pipe adopts 1:1 cement slurry, the initial pressure of grouting is 0.5-1.0 MPa, the final pressure is 2.0MPa, and the sectional grouting is adopted.

By adopting the technical scheme, the final grouting pressure is greater than the discharge pressure, so that the grouting device is favorable for fully filling slurry and improves the grouting effect.

Optionally, a sealing plate is fixed at the exposed end of the conduit and sealed, a grouting pipe is fixedly arranged on the sealing plate in a penetrating way, and a valve is arranged on the grouting pipe; after grouting is completed on each grouting pipe, the sealing plate is removed, the water pipe penetrates into the bottom of the guide pipe, clean water is injected into the guide pipe to clean cement slurry in the guide pipe, and M30 cement mortar is used for grouting.

By adopting the technical scheme, the M30 cement mortar is used for tightly filling, so that the rigidity and the strength of the pipe shed are improved.

Optionally, in the step S1, the curtain grouting, the soil grouting and the rock-soil grouting are interval type drilling grouting.

By adopting the technical scheme, grouting is performed at intervals between the holes, so that the hole spacing of the first lot of grouting is large, and the possibility of slurry leakage during grouting of two adjacent holes is reduced. And during the subsequent second batch of grouting, grouting is performed in the holes on the two adjacent sides, and grouting is performed again, so that the two adjacent sides are connected and fixed into a whole simultaneously during slurry permeation, and the grouting effect is improved.

Optionally, after grouting reinforcement of the curtain is completed, only the grouting pipe of the joist area to be built is taken out; and/or, only taking out the grouting pipe of the joist area to be built after the grouting reinforcement of the rock soil is completed.

By adopting the technical scheme, the non-taken grouting pipe can be used as a reinforcing support to further strengthen the existing building foundation.

Optionally, the rock-soil mass grouting is divided into soil layer section grouting and rock stratum section grouting, wherein the soil layer section grouting pressure is 0.1-0.3 MPa, and the rock stratum section grouting pressure is 0.5-1 MPa;

specifically, the cement-sand ratio of the grouting body is 0.8-1.5, and the cement-water ratio is 0.38-0.5;

specifically, the grouting pipe is 0.5m away from the hole bottom, a grouting plug is arranged at the position, close to the outlet end, of the grouting pipe, and the grouting plug is positioned at the position of 0.5m away from the grouting bottom;

specifically, the grouting adopts circulating type sectional grouting from top to bottom; and after each section of grouting is finished, at least waiting for solidification for 4 hours, and the next section of construction can be performed.

Through adopting above-mentioned technical scheme, can prevent to leak thick liquid for thick liquid can be annotated fully, has reduced the not structural risk that full thick liquid arouses. The grouting liquid has high fluidity, permeability, setting time and other comprehensive properties, and is favorable to site operation conditions. And 4, waiting for solidification for 4 hours to fully solidify the grouting of the previous section, and avoiding being influenced by the construction of the next section.

Optionally, the supporting component comprises a steel pipe and I-steel inserted into the steel pipe, and the steel pipe is filled with concrete; specifically, the I-steel is formed by splicing multiple sections, connecting plates are arranged on two sides of two adjacent sections of I-steel, and the connecting plates are fixed with the I-steel through bolts.

By adopting the technical scheme, the steel pipe can reduce the erosion of external moisture to the I-steel and prolong the service life of the I-steel. The I-steel and the concrete jointly fill and support the steel pipe. The multi-section I-steel is firmly connected, so that the possibility of structural instability caused by shaking is reduced. The multi-section I-steel is convenient to insert into the steel pipe section by section for construction, reduces the installation weight and the installation length of a single section, and facilitates field operation.

In summary, the present application includes at least one of the following beneficial technical effects: the foundation below the existing house is reinforced, and the steel pipe support beam is adopted to reinforce the foundation of the existing house, so that the stability of the building structure and the construction safety of the new circuit during the construction of the building structure by underpass construction of the new circuit can be effectively ensured. The reinforcement method has low clear distance requirement on the newly built line and the existing building; the investment of the newly built line on the symptom land removing part is reduced to a certain extent, and the construction period pressure is reduced.

Drawings

FIG. 1 is a schematic plan view of a relationship between an inter-zone tunnel and an existing building location in the background art;

FIG. 2 is a schematic diagram of a tunnel and existing building foundation location in the background art;

FIG. 3 is a schematic plan view of curtain grouting reinforcement;

FIG. 4 is a schematic cross-sectional view of curtain grouting reinforcement;

FIG. 5 is a plan view of soil body reinforcement grouting;

FIG. 6 is a cross-sectional view of soil reinforcement grouting;

FIG. 7 is a plan view of a rock-soil body reinforcement grouting;

FIG. 8 is a cross-sectional view of a rock-soil body reinforcement grouting;

FIG. 9 is a joist elevation view;

FIG. 10 is a cross-sectional view of a joist;

FIG. 11 is a reinforcing plan view of the support assembly;

FIG. 12 is a schematic view of a steel pipe pile, a support assembly and joist connection structure;

FIG. 13 is a schematic diagram of a I-steel connection structure;

FIG. 14 is a cross-sectional view taken along the B-B plane in FIG. 12;

FIG. 15 is a schematic view of a guide wall construction support;

fig. 16 is a diagram showing the structure of the connection of the guide pipe and the reinforcement cage;

FIG. 17 is a schematic view of a catheter grouting structure;

FIG. 18 is a profile hole and split hole distribution diagram;

FIG. 19 is a schematic view of a pre-support structure for a lead catheter;

FIG. 20 is a schematic view of a CD method arch frame assembly;

fig. 21 is a schematic view of a grid column and arch connection structure.

Reference numerals illustrate:

1. an interval tunnel; 11. a guide wall; 111. a contour hole; 112. splitting holes; 12. a conduit; 121. a sealing plate; 122. grouting pipe; 123. a valve; 13. an arch form; 14. a reinforcement cage; 15. a lead catheter; 16. a secondary lining plate; 17. a concrete layer;

2. a curtain; 21. a curtain grouting pipe;

3. soil body reinforcing grouting pipe;

4. a rock-soil body reinforcing grouting pipe;

5. joist;

6. a steel pipe pile;

7. a support assembly; 71. i-steel; 711. a connecting plate; 72. a steel pipe;

8. an arch frame; 81. a connecting plate; 82. stiffening ribs;

9. grid uprights;

J ₂ s-Ss, sandy mudstone; j (J) ₂ s-Sm, sandstone; q (Q) ₄ ^ml And (5) backfilling the soil layer.

Detailed Description

The present application is described in further detail below in conjunction with figures 1-21.

The embodiment of the application discloses a construction method for undermining an existing building undercut tunnel.

Referring to fig. 1 and 2, a schematic diagram of the positional relationship between the present section tunnel 1 and an existing building is shown. The vault burial depth of the tunnel 1 in the section is 1.62-30.27 m. The geological condition of the section tunnel 1 along the line is complex, and the section tunnel passes through sandy mudstone J along the line ₂ s-Ss, sandstone J ₂ s-Sm and backfill layer Q ₄ ^ml Surrounding rock grade III-V. Above a certain section there is an existing building, the name of which is building F, and as shown in figure 1, the building is in an oblique relationship with the line. The building F is a 7-layer brick-concrete structure house, the foundation is a strip stone foundation, the bearing capacity of the foundation base is not high, the distance between the vault of the section tunnel and the foundation d of the building F is only 3.4m, and under the condition that a resident is not moved, the tunnel excavation has extremely high requirements on the settlement control of the building. In order to solve the problem of field practical construction, technicians research and design a construction method for undermining the existing building undercut tunnel.

A construction method for a subsurface tunnel penetrating through an existing building comprises the following steps:

reinforcing the existing building foundation:

s1, grouting reinforcement:

s11: grouting and reinforcing the drilling curtain. Referring to fig. 3 and 4, the horizontal spacing of the holes is 2m, the depth of the holes is 10m, the diameter of the holes is 75mm, the holes are inserted into curtain grouting pipes 21, the curtain grouting pipes 21 can be steel flower pipes with the diameter of 48mm, the flower pipe grouting is adopted, the curtain grouting pipes 21 in the area of the joist 5 to be built are taken out, the curtain grouting pipes 21 in other areas are not taken out, no. 42.5 cement paste is adopted as reinforcing support, and the grouting pressure can be 0.1-0.2 mpa. The grouting pressure must be properly adjusted according to in-situ manufacturability tests and observed deformation conditions. The reinforcement area is the reinforcement of the strip stone retaining wall back soil body and the retaining wall foundation soil body near the F building, and the reinforcement purpose is to consolidate and seal the soil body to form a curtain so as to prevent the second-step soil grouting and the third-step rock grouting from generating slurry leakage.

S12: grouting and reinforcing soil. Referring to fig. 5 and 6, the horizontal spacing of the holes is 1m, the depth of the holes is about 20 m, the diameter of the holes is 75mm, the holes are inserted into the soil grouting pipes 3, the soil grouting pipes 3 can be steel flower pipes with the diameter of 48mm, the flower pipe grouting is adopted, the soil grouting pipes 3 in the area of the joist 5 to be built are taken out, the soil grouting pipes 3 in other areas are not taken out, no cement paste of 42.5 is adopted as reinforcing support, and the grouting pressure can be 0.1-0.3 mpa. The grouting pressure must be properly adjusted according to in-situ manufacturability tests and observed deformation conditions. The reinforced area is the reinforcement of the soil layer grouting below 2m of the F building ground, and the purpose of the reinforcement is to improve the shear strength index of the F building ground soil body.

S13: grouting and reinforcing a rock-soil body. Referring to fig. 7 and 8, the horizontal distance between the holes is 1m, the depth of the holes is about 20-30 m, the diameter of the holes is 75mm, the holes are inserted into the rock-soil body grouting pipe 4, and the rock-soil body grouting pipe 4 also adopts a steel flower pipe with the diameter of 48 mm. The slurry adopts 42.5 cement paste, 10% of expanding agent is added into the slurry, the grouting pressure of a soil layer section can be 0.1-0.3 MPa, the grouting pressure of a rock layer section can be 0.5-1 MPa, the grouting pressure must be properly adjusted according to the on-site process test and the observed deformation condition, and a grouting plug must be arranged at the rock entering position between the grouting of the rock layer section to ensure that the grouting leakage is avoided. The reinforced area is the grouting reinforcement of the soil body below 2m of the F building floor and the rock mass at the top of the tunnel, and the purpose of the reinforcement is to form a relatively solidified whole body by grouting reinforcement, so that the deformation influence of tunnel excavation on the ground building is reduced.

Drilling grouting is performed from bottom to top, grouting is performed in time after hole forming, grouting construction is performed at hole jumping intervals, and a unidirectional pushing grouting mode cannot be adopted.

The mixing water is preferably drinking water, and the water does not contain harmful substances affecting the normal setting and hardening of cement, so that sewage cannot be used; the sand is preferably medium-fine sand, when the ultra-fine sand is adopted, the fineness modulus is not less than 0.7, the mud content in the sand is not more than 3% by weight, and the content of harmful substances such as mica, organic matters, sulfides, sulfuric acid and the like is not more than 1% by weight; the cement-sand ratio of the grouting body is 0.8-1.5, and the cement ratio is 0.38-0.5. When the pipe is drilled by using the pipe, the pipe is a hot rolled seamless steel pipe with phi 80 multiplied by 3.5mm, and the steel strength is Q345. Grouting mode: the grouting adopts circulating type sectional grouting from top to bottom, and the grouting pipe is 0.5m away from the hole bottom. The grouting plug is plugged at the 0.5m position of the grouting bottom to prevent the grouting. After each section of grouting is finished, the grouting must be coagulated for 4 hours, and the next section of construction can be performed. Grouting end: and (3) under the designed grouting pressure, continuing grouting for 30min when the injection rate of the grouting section is not more than 1L/min, and finishing grouting.

And (3) quality inspection of grouting reinforcement foundation:

1) The grouting test time should be 28 days after grouting is finished. The grouting effect is assessed, the comparison of data before and after grouting is emphasized, and the grouting effect is comprehensively assessed by combining the settlement observation result of the building;

2) Sampling at intervals of 1 meter in the whole depth range of the reinforced soil for indoor test to determine indexes such as compressibility and strength;

3) The grouting detection points are arranged between the grouting holes, and the detection quantity is 2% -5% of the number of the grouting holes. When the qualification rate of the detection points is less than or equal to 80 percent, or the average value of the detection points is more than 80 percent but does not meet the design requirement of strength, repeated grouting is carried out on the unqualified grouting areas;

4) The grouting solidification body test block should be subjected to a strength test.

S2, reinforcing a bearing mechanism:

s21, drilling. The holes are formed by a drilling machine.

S22, constructing the support assembly 7. Referring to fig. 9 and 10, a phi 194 seamless steel pipe is drilled for the second time to form a hole, the seamless steel pipe is processed into a perforated pipe, 14-type hot rolling I-steel is penetrated into the seamless steel pipe, after the design depth is reached, the residual space in the hole is filled with M30 cement mortar in a double-pipe grouting mode to be compact, and the grouting pressure can be 0.1-0.3 MP. The grouting pressure must be properly adjusted according to in-situ manufacturability tests and observed deformation conditions.

S23, constructing the steel pipe pile 6 and the pile top joist 5. Referring to fig. 11 and 12, the steel pipe piles 6 are drilled with a drill, Φ194 steel pipe + No. 14 hot rolled i-steel is inserted, and the steel pipe piles 6 are divided into four rows, each row crossing an underground pipeline. Before the construction of the steel pipe pile 6, the natural gas pipeline, the fire-fighting water pipe and the electric power pipe ditch are required to be isolated and protected. The pile top adopts the joist 5, and joist 5 cross-section size is 2.1mX3m, and joist 5 is connected with supporting component 7, and the channel-section steel is adopted to joist 5 bottom transversely welds on steel-pipe pile 6, strengthens as steel-pipe pile 6 exposed part, simultaneously again as the die block support frame of joist 5.

Referring to fig. 13 and 14, the support assembly 7 includes a steel pipe 72 and i-beams 71 inserted into the steel pipe 72, the i-beams 71 have a plurality of sections, two adjacent sections of the i-beams 71 are fixed by a connection plate 711, the connection plate 711 is distributed at both sides of the interface of the i-beams 71, and the connection plate 711 is fixed with the i-beams 71 by bolts.

And then carrying out the construction of the underground excavation tunnel.

1. Hole excavation

After the open cut foundation pit support structure is formed, a hole slope support is timely made, then earth excavation is started, the excavation needs to meet the requirements of mechanical equipment in-out and construction of the guide wall 11, a reserved part of core soil is convenient for construction of a step part on the guide wall 11, an excavator is adopted for excavation and support from top to bottom, a dump truck is used for transportation, part of guard piles are chiseled according to the position of the tunnel hole during transportation, and the guard pile steel bars keep lap joint length so as to be anchored in the guide wall 11.

2. Advanced pipe shed support construction

(1) The length of the leading pipe shed is 40m, a hot-rolled seamless steel pipe with phi 108mm and wall thickness of 6mm is adopted, the pitch length is 3m and 6m, and the circumferential spacing is 40cm. And (5) a special pipe shed drilling machine and a grouting machine are arranged for construction.

(2) Guide wall construction

Referring to FIG. 15, a long pipe shed construction guide is formed by setting 2.5m long and 1m thick C25 concrete at the hole, 11, 3I 22a I-beams are adopted as steel frames in the sleeve arch, the spacing is 750mm, the steel frames are erected and then welded and connected by phi 22 steel bars to form a whole, then a conduit 12 is installed, the conduit is a phi 133 multiplied by 4 seamless steel pipe, the length is 2.5m, the circumferential spacing is 40cm, the elevation angle is 1-3 degrees (no route longitudinal slope is included), and the conduit 12 is welded and fixed according to a design drawing.

After the guide pipe 12 is installed, the arch construction template 13 is made of 50mm thick wood plates, secondary ribs are made of 100mm square wood, the distance is 300mm, the bracket is made of I16I-steel and is used for arc support, and horizontal support rods are arranged at the end parts of the arc support.

(3) Drilling construction

The drilling is performed by adopting a pipe shed drilling machine, and a phi 133 orifice pipe pre-buried in the sleeve arch is used as a guide pipe 12 for drilling. The slope must be sprayed with a layer of plain concrete as a slurry wall so as to ensure that slurry leakage and collapse do not occur when the slope is subjected to pressure grouting and ensure the stability of surrounding rocks of the slope. The drilling angle is drilled according to an angle of 1-3 degrees.

(1) Checking whether the mechanical condition of the drilling machine is normal or not before drilling; determining whether to drill by adding slurry or cement slurry according to the situation when drilling, and continuously drilling by adding the slurry to protect the wall when drilling to the holes easy to collapse in the sand layer; if no hole can be formed, a sleeve can be added or a drill bit can be directly welded at the front end of the guide pipe 12 for drilling;

(2) after the drilling machine is in place, measuring the well-lofted point drilling positions in advance; when drilling is performed, the palm face is propped up, so that the drilling precision is improved; the drilling speed is low when the drilling machine opens holes, and the drilling speed is changed into the normal drilling speed after the drilling depth reaches 20 cm; and the drilling direction of the drilling machine is continuously adjusted in the drilling process.

(3) And stopping drilling when the tail of the first section of drill rod is drilled into the rock stratum and is left for 20-30 cm, manually clamping the drill rod by using two pipe tongs, reversing the drilling machine at a low speed, and disengaging the drill rod. The drilling machine returns to the original position along the guide rail, a second section of drill rod is manually installed, a connecting sleeve is installed at the front end of the drill rod, the drilling machine is sent to the tail part of the first drilling hole at a low speed, and the drilling machine is connected into a whole after the direction alignment. Each time lengthening is carried out according to the method.

(4) When the drill rod is replaced, whether the drill rod is bent, damaged or not, whether a central water hole is smooth or not and the like are checked, and the drill rod is not required to be replaced, so that normal operation is ensured;

(5) in order to prevent the drill rod from vibrating up and down under the dual actions of thrust and vibration force, so that the drill hole is not straight, the centralizer is sleeved on the drill rod during drilling and translates forward along with the drilling of the drill rod.

(4) Pipe shed processing and installation

Referring to FIG. 16, a pipe shed grouting pipe 122 is processed according to a design drawing, the grouting pipe is made of phi 108 multiplied by 6 hot rolled seamless steel pipes, grouting holes are blown through by oxygen acetylene, the aperture phi is 10-16 mm, the distance is 30cm, and the grouting pipes are annularly arranged in a quincuncial shape. The grouting pipe 122 is connected by screw thread, the length of the screw thread section is 15cm, the inner sleeve wire steel pipe is phi 102 multiplied by 6 hot rolled seamless steel pipe, the length is 30cm, in order to stagger the joints of the grouting pipe 122, the length of the first section of the odd-numbered holes is 3m, the length of the first section of the even-numbered holes is 6m, and each section is 6 m. The foremost end of the conduit 12 is pointed, and the length of the last section is 4.5 meters.

The steel pipes which are numbered in advance correspond to the hole numbers, the steel pipes are fastened by steel ropes and then are directly conveyed into the pipe, if the steel pipes are blocked, external force can be applied to convey the steel pipes, and the pipe 12 is exposed for 20cm.

Referring to fig. 16, in order to improve the bending resistance of the guide pipe 12, a reinforcement cage 14 may be added in the guide pipe 12, the reinforcement cage 14 is composed of four main ribs with a diameter of 18mm and fixing rings formed by welding reinforcement rings with a diameter of 6mm, the reinforcement rings are welded with the main ribs, and two adjacent fixing rings are arranged at a 1m interval.

(5) Grouting

Grouting the pipe shed by adopting 1:1 cement paste, wherein the initial pressure of grouting is 0.5-1.0 MPa, the final pressure is 2.0MPa, and sectional grouting is adopted.

Referring to fig. 17, the exposed end of the duct 12 is tightly sealed by welding a sealing plate 121, the sealing plate 121 may be a steel plate, a grouting pipe 122 is welded on the sealing plate 121, and a valve 123 is installed on the grouting pipe 122. After each grouting pipe 122 finishes grouting, acetylene is used for cutting off a sealing plate 121 at the end of the guide pipe 12, a phi 32 water pipe is used for penetrating into the bottom of the guide pipe 12, clear water is injected for cleaning cement slurry in the guide pipe 12, and M30 cement mortar is used for grouting. And the M30 cement mortar is used for tightly filling, so that the rigidity and the strength of the pipe shed are improved.

3. Excavation of cave body

The tunnel is provided with a small advance guide pipe to pre-reinforce the rock mass in the front range of the face, the non-blasting excavation of a water mill drill and a splitting machine is adopted, the disturbance to surrounding rock is reduced, the circular excavation footage of the excavation footage CD method is strictly controlled to be not more than 2 steel frames (1 m), and the longitudinal excavation footage of the left guide hole and the right guide hole is staggered by more than 15 m.

Referring to fig. 18, the water mill drill holes are arranged along the outline of the excavated part, a plurality of coring points are formed at the coring points, the coring diameter is 150mm, the coring circles are tangent, cores are sequentially drilled, the height of the extracted cores is about 500mm, a closed free surface is formed at the part after the cores are completely extracted, then the hand wind drill is adopted to drill the splitting holes 112 in the formed closed area, the length of the holes is about 3-4 m, the length circulation of 6-8 water mill drill holes 111 is satisfied, and then the splitting bars of the splitting machine are inserted into the holes from top to bottom to crack rock. The rock mass is transported out of the hole by a dump truck through procedures of small excavator slag skimming, manual cooperation cleaning, slag loading and the like.

4. Support construction

4.1. Advanced small conduit construction

The advanced guide pipe 15 pre-support is arranged in the range of 120 DEG of the arch part of the cross section of the CD method, the advanced guide pipe A42 is adopted, the annular distance is 400mm, the L=3.5m, the longitudinal distance is 1.5m, and the external insertion angle is 10-15 deg.

(1) Process flow

Geological formation analysis, catheter manufacture, pore-forming or air pick gun feeding into a catheter, slurry stirring and grouting

(2) Manufacture of the advance catheter 15

Referring to fig. 19 and 20, the leading conduit 15 is made of hot rolled seamless steel pipe with an outer diameter of 42mm and a wall thickness of 3.5mm, the length of the conduit is 3.5m, the front end is processed into a cone shape, the tail part is welded with a 6mm reinforcing steel bar hoop for reinforcement, 17 rows of 10mm grouting holes are drilled on the periphery of the pipe wall, the leading conduit 15 is driven into a rock stratum along the periphery of the tunnel excavation outer contour line at an external insertion angle of 10-15 degrees during construction, the circumferential spacing of the leading conduit 15 is 0.4m, the longitudinal spacing is 1.5m, and the arrangement range is 120 degrees of the arch part.

(3) Advance catheter 15 installation

Drilling holes at predetermined positions with a pneumatic rock drill. The leading conduit 15 is inserted into the hole, a screw thread protective cap is arranged, and the special plug is jacked into the required depth, so that the hemp thread plunger is fully extruded and pressed with the hole wall. The orifice is then filled with CS cement. The exposed length of the grouting pipe is 20-30 cm. So as to connect the orifice valve and the conduit. The tail of the steel pipe is protected from being damaged during pipe jacking so as to be connected with a high-pressure grouting pipe.

(3) Grouting

The cement slurry is adopted as the slurry, the cement-cement ratio is 1:1 (weight ratio), the construction is selected by a laboratory, and cement with the strength not lower than PO.42.5 is used.

4.2. Primary support

The tunnel primary support consists of a steel bar hanging net, sprayed concrete, a mortar anchor rod and a section steel arch/grid steel frame.

(1) Anchor rod construction

The mortar anchor rods are made of twisted steel bars, the length and the distance are determined according to the surrounding rock condition and design, and the system anchor rods are arranged in a quincuncial manner. The mortar anchor rod adopts an anchor rod trolley, an anchor rod drilling machine or a pneumatic rock drill to drill, the anchor rod is installed by mechanical cooperation with manual work, and an orifice backing plate is installed after the cement mortar is finally set. The diameter of the drilling hole is 15mm larger than the diameter of the anchor rod. And then, injecting early strength cement paste into the drill hole by adopting a special grouting pump for the mortar anchor rod, wherein the proportion of cement is as follows: sand: the water is preferably 1 (1-1.5): (0.45-0.5), the early strength cement adopts sulphoaluminate early strength cement and is doped with an early strength agent. When grouting, the grouting pipe is inserted to a position 5-10 cm away from the hole bottom, slowly and uniformly pulled out along with the injection of cement paste, and then the rod body is quickly inserted, wherein the length of the inserted rod body of the anchor rod in the hole is not shorter than 95% of the designed length. If no mortar overflows from the hole, the rod body is pulled out for grouting again.

(2) Construction of sprayed concrete

1) The tunnel spray concrete support adopts a dry spray construction process, and the concrete method comprises the following steps:

before spraying, the tunnel cross section size is carefully checked, the undermined part and all cracked, broken and water-soluble disintegrated broken rocks are removed and treated, pumice and wall corner virtual slag are removed, and the rock face is washed by high-pressure water or wind.

After the installation and debugging of the sprayer, water is injected and then ventilated, and the barrel and the pipeline are cleared for feeding. Continuous feeding is carried out, the hopper is always kept full, a screen mesh with the aperture of 12mm is arranged on the hopper, and the phenomenon that the pipe is blocked due to the fact that oversized aggregate enters the machine is avoided. During spraying, water is injected firstly, the nozzle is noted to be downward, and water is prevented from flowing into the conveying pipe; and then air is blown, and then feeding is carried out, and the water injection quantity is adjusted according to the sprayed surface and the sprayed mixture condition, so that the sprayed paint is easy to adhere, has small rebound and has wet luster on the surface. Injection sequence: the spraying operation is carried out by adopting the sequence of sectioning, blocking, wall-first and arch-later and from the lower cloth. The tunnel is internally provided with a section of 3-4 m along the longitudinal direction, and each section of the tunnel is provided with a section of 2m width. During spraying, the nozzle makes a slow spiral movement, so that the movement track of the sprayed material beam moves in an annular spiral manner, the rotation diameter is about 20-30 cm, the horizontal rotation spraying is started from the lower part of the spraying surface, the sprayed material needs to be pressed for half a circle, and moves upwards to return when being sprayed to the tail of the section, and meanwhile, a row of pressing rows are required to be sprayed in a reciprocating manner. When spraying, if the concave part of the sprayed surface is uneven, the sprayed part is sprayed first, and the sprayed part is approximately leveled.

In order to ensure the compactness of the sprayed concrete and reduce the rebound quantity, the air pressure, the water pressure, the spraying distance of the spray head and the spraying angle are reasonably adjusted. The distance from the nozzle to the surface to be sprayed is preferably 0.6 to 1.0m, and the beam is preferably perpendicular to the surface to be sprayed.

The setting speed of the jet material beam and the jet thickness are preferably one turn every 2 seconds, the jet thickness is preferably not more than 5cm when the jet thickness reaches the critical thickness of falling back or reaches the design requirement thickness, and the jet thickness is generally not less than 5cm. If the required spraying thickness is large, the second spraying is carried out after the first layer of concrete is finally set for 1 hour when the first spraying cannot be achieved. The two injections are used for paying attention to leveling the rock surface so as to lay a waterproof layer. The wind pressure and the feeding amount are adjusted according to different spraying positions and the type of the adopted spraying machine.

2) The water-bearing section sprays concrete and adopts the following measures:

when the water points are not more, a guide pipe can be arranged to guide water and then spray concrete; when the water inflow range is larger, a small conduit can be arranged for grouting and stopping water, and then concrete is sprayed; when water burst is serious, a water discharge hole can be arranged, and concrete is sprayed while water is discharged.

Increasing the cement consumption, changing the mixing ratio, gradually approaching the water gushing point from far to near, arranging a conduit at the water gushing position, leading out water, and spraying concrete near the conduit.

3) Construction notes:

the equipment condition is carefully checked before spraying, dangerous stones are treated in advance, the spraying machine is arranged in a safety zone and is close to the spraying position as much as possible, palm personnel can be conveniently connected with spraying hands, and working wind pressure can be adjusted at any time. The discharge elbow, the material conveying pipe and the pipeline joint of the sprayer are frequently checked, and the problem is found to be treated in time. When spraying is started, water injection is needed, air supply is needed, and then starting up and feeding are needed. And stopping the machine and the mixing materials in the pipe after the spraying operation is finished, closing water and cutting off wind. After each class of construction operation is completed, the jet machine is cleaned and overhauled, and the working state of the next class of machine is guaranteed to be good.

In the construction process, the materials are strictly mixed according to the designed mixing proportion and the mixing method, the metering is accurate, and particularly the dosage of the additive must meet the design requirement. The transportation road is ensured to be smooth, the lighting power consumption is ensured, and the wind pressure and the water pressure are stable.

(3) Reinforcing mesh construction

The reinforcing mesh is processed into grid meshes according to design requirements, and the intersections of the longitudinal and transverse reinforcing bars can be welded into blocks. The reinforcing mesh is generally arranged after the primary spraying of concrete, and is conveyed to a working surface for laying during construction, the mesh is closely attached to the primary spraying surface, and the thickness of the concrete protection layer must meet the design requirement. The mesh sheets are firmly welded with each other and the anchor rod. The steel bar must pass the test to detect the qualified performance; before use, the steel bar needs to be subjected to rust removal and decontamination treatment; the joint of the reinforcing mesh and the anchor rod are firmly welded by adopting electric welding, the mesh is tied or welded by using iron wires, and the mesh cannot move during spraying operation; the reinforcement mesh is paved to be fluctuant along with the initial spraying surface of the concrete and is closely contacted with the wall surface; after the concrete is sprayed again, the reinforcing mesh is completely covered, the reinforcing mesh cannot be exposed, and a protective layer with the thickness of 3-5 cm is needed. The sprayed concrete surface should be smooth after the re-spraying.

(4) Section steel arch mounting, refer to fig. 20 and 21

(4.1) in-situ fabrication and processing

The arch frame 8 is formed by processing in advance in a hole outer structural member factory according to design requirements. The processing site is hardened by concrete, and a 1:1 processing sample is discharged according to the design. And reserving welding shrinkage allowance and cutting allowance according to technological requirements during lofting. The grid steel bar is formed by cold bending, and the requirement of the grid steel bar is accurate in size and smooth in arc shape. The arch frame 8 can be connected by using I-steel, the splicing end of the I-steel is fixedly connected with a connecting plate 81, stiffening ribs 82 are fixed between the connecting plate 81 and the I-steel, and the connecting plate 81 is fixed together into a whole by bolts between two adjacent I-steel sections.

(4.2) requirements of the arch frame 8 erection process

In order to ensure that the arch frame 8 is arranged on a stable foundation, reserving a 0.15-0.2 m original foundation at the footing part of the arch frame 8 in construction; when the arch frame 8 is erected, the grooves are cut into place, and the foot locking anchor rods and the channel steel are arranged at the foot positions of the arch frame 8 in the weak surrounding rock section so as to increase the bearing capacity of the substrate. The plane of the arch frame 8 is perpendicular to the central line of the tunnel, and the inclination is not more than 2 degrees. Any part of the arch 8 deviates from the vertical plane by no more than 5cm. In order to ensure the stability and effectiveness of the arch frame 8, foot locking anchor rods are additionally arranged at two arch feet and two wall feet, and each foot locking anchor rod consists of 2-4 anchor rods.

The arch frame 8 is arranged according to the design position, and in the arranging process, when a larger gap exists between the arch frame 8 and the primary spraying layer, a saddle cushion block is arranged, and the gap between the arch frame 8 and surrounding rock (or cushion block) is not more than 50mm. To enhance the overall stability of the arch 8, the arch 8 is coupled to an anchor rod. Longitudinal connecting bars are arranged along the arch 8.

In order to accurately position the arch frame 8, the arch frame 8 needs to be pre-tied with a preset position tie bar before being erected. One end of the tie bar is connected with the arch frame 8, the other end is anchored in surrounding rock for 0.5-1 m and is anchored by mortar, and the anchor bar is used for positioning as much as possible when the anchor bar is arranged at the erection position of the arch frame 8. After the arch frame 8 is erected, concrete is sprayed as soon as possible, and the arch frame 8 is covered completely, so that the arch frame 8 and the sprayed concrete are stressed together. The sprayed concrete is sprayed upwards from the arch foot or the wall foot to prevent the upper sprayed material from virtually covering the arch foot (wall foot) and being not compact, so that the strength is insufficient and the arch foot (wall foot) is unstable.

(5) Grid column 9 and CD method partition wall installation

Firstly, processing each numbered steel bar into a semi-finished product, performing trial assembly on site according to unit processing and forming, and transporting the qualified steel bars to site for installation, wherein the tops of the grid upright posts 9 are connected with the arch centering 8 into a whole.

5. Slag discharging transportation

According to the actual condition of the construction site, the project tunnel slag discharge adopts trackless transportation. The method adopts a loader or an excavator to load slag, and the slag transportation adopts a dump truck with a tail gas purifying device. The tunnel waste slag is conditioned and utilized as much as possible, and the rest is discarded to a slag field.

6. Waterproof and drainage construction

The underground tunnel adopts full-package interlayer waterproof, wherein the waterproof layer is a pre-paved non-asphalt high polymer self-adhesive film waterproof roll material with the thickness of 1.5mm and a geotextile buffer layer, and geotextiles are all short-fiber geotextiles with the thickness of 400g/m < 2 >. The waterproof layer of the bottom plate is made of fine stone concrete with the thickness of 70 mm. When the construction period is short, the coiled materials can be required to be pre-paved and viscosity reduction measures are taken, and the inverted arch structure is directly constructed. The second lining is waterproof concrete, and the impervious grade is not less than P8.

And the construction of the secondary lining plate 16 and the construction of the arch wall are carried out subsequently.

The foregoing are all preferred embodiments of the present application, and are not intended to limit the scope of the present application in any way, therefore: all equivalent changes in structure, shape and principle of this application should be covered in the protection scope of this application.

Claims (7)

1. A construction method for a subsurface tunnel penetrating through an existing building is characterized by comprising the following steps of: comprising

S1, grouting reinforcement:

s11, grouting and reinforcing a curtain: solidifying and sealing soil near the existing building to form a curtain; inserting a curtain grouting pipe (21), grouting by using a flower pipe, taking out the curtain grouting pipe (21) in the area of the joist (5) to be built, and taking the curtain grouting pipe (21) in other areas out of the curtain grouting pipe as a reinforcing support;

s12, soil grouting reinforcement: reinforcing a soil layer below 2m of the ground of the existing building; inserting a soil grouting pipe (3), grouting by using a flower pipe, taking out the soil grouting pipe (3) in the area of the joist (5) to be built, and taking the soil grouting pipe (3) in other areas out of the area as a reinforcing support;

s13, grouting and reinforcing a rock-soil body: grouting and reinforcing soil below 2m of the existing building ground and rock mass at the top of the tunnel, so that a solidified whole is formed by the foundation soil and the rock mass;

s2, reinforcing a bearing mechanism:

s21, installing a supporting component (7) below the existing building;

s22, constructing a steel pipe pile (6) close to the existing building, and pouring a joist (5) at the top of the steel pipe pile (6);

one end of the supporting component (7) is fixed in the joist (5) and the other end is fixed in the rock mass;

the bottom of the joist (5) is welded to the steel pipe pile (6) transversely by adopting channel steel, and is used as a bottom die supporting frame of the joist (5) while being reinforced by the exposed part of the steel pipe pile (6);

the support assembly (7) comprises a steel pipe (72) and I-steel (71) inserted into the steel pipe (72), wherein the I-steel (71) is provided with a plurality of sections, two adjacent sections of I-steel (71) are fixed through connecting plates (711), the connecting plates (711) are distributed on two sides of an interface of the I-steel (71), and the connecting plates (711) are fixed with the I-steel (71) through bolts;

s3, tunnel construction:

s31, pipe shed construction: constructing a guide wall (11) of concrete at a tunnel opening to be excavated, penetrating a guide pipe (12) around the top of the guide wall (11) and grouting, wherein the guide pipe (12) penetrates through the bottom of an existing building and is inserted into a rock mass at the upper part of a tunnel;

s32, excavating and supporting a tunnel body;

s33, secondary lining of the tunnel;

in the S1 step, curtain grouting, soil grouting and rock-soil grouting are interval type drilling grouting, the rock-soil grouting is divided into soil layer section grouting and rock layer section grouting, the soil layer section grouting pressure is 0.1-0.3 MPa, and the rock layer section grouting pressure is 0.5-1 MPa.

2. The method for constructing the undercut tunnel of the underpass existing building as claimed in claim 1, wherein the method comprises the following steps: in the step S32, during construction, an advance guide pipe (15) is inserted into the arch part of the excavated section for grouting, the advance guide pipe (15) is driven into a rock stratum along the periphery of the outer contour line of the tunnel excavation at an external insertion angle of 10-15 degrees, and the advance guide pipes (15) are annularly and alternately arranged above the arch part of the tunnel to be excavated.

3. The method for constructing the undercut tunnel of the underpass existing building as claimed in claim 2, wherein the method comprises the following steps: when a tunnel body is excavated, grouting pre-reinforcement treatment is carried out on a tunnel face, profile holes (111) are drilled along the profile lines of the tunnel to form a closed area, a plurality of splitting holes (112) are drilled in the closed area, and splitting rods are inserted into the splitting holes (112) from top to bottom to crack rock bodies.

4. A method of constructing a underpass existing building undercut tunnel according to any one of claims 1-3, characterized by: a reinforcement cage (14) is arranged in the conduit (12) in a penetrating way.

5. The method for constructing the undercut tunnel in the underpass existing building as claimed in claim 4, wherein: the grouting of the guide pipe (12) adopts 1:1 cement slurry, the initial pressure of grouting is 0.5-1.0 MPa, the final pressure is 2.0MPa, and the sectional grouting is adopted.

6. The method for constructing the undercut tunnel in the underpass existing building as claimed in claim 5, wherein: a sealing plate (121) is fixed at the exposed end of the guide pipe (12) and sealed, a grouting pipe (122) is fixedly arranged on the sealing plate (121) in a penetrating manner, and a valve (123) is arranged on the grouting pipe (122); after grouting is completed, the sealing plate (121) is removed from each grouting pipe (122), the water pipe is used for penetrating into the bottom of the guide pipe (12), clean water is injected into the guide pipe (12) to clean cement slurry in the guide pipe (12), and M30 cement mortar is used for grouting.

7. The method for constructing the undercut tunnel of the underpass existing building as claimed in claim 1, wherein the method comprises the following steps: specifically, the cement-sand ratio of the grouting preparation is 0.8-1.5, and the cement-water ratio is 0.38-0.5;

specifically, the grouting pipe is 0.5m away from the hole bottom, a grouting plug is arranged at the position, close to the outlet end, of the grouting pipe, and the grouting plug is positioned at the position of 0.5m away from the grouting bottom;

specifically, the grouting adopts circulating type sectional grouting from top to bottom; and after each section of grouting is finished, at least waiting for solidification for 4 hours, and the next section of construction can be performed.