CN114482014B - Construction method for hammering pile sinking of precast pile in deep foundation pit in offshore ultra-thick silt region - Google Patents

Abstract

The invention discloses a construction method for hammering and sinking precast piles in a deep foundation pit in an offshore ultra-thick silt region, which belongs to the technical field of building construction, and aims to solve the technical problems of ensuring the safety of the foundation pit in the precast pile construction process, reducing the influence of hammering construction vibration and stress extrusion of the precast piles in the deep foundation pit on a deep foundation pit support pile, and adopting the following technical scheme: the method comprises the following steps: s1, installing an inclinometer and automatic foundation pit detection equipment; s2, constructing stress release holes and stress release grooves; s3, hammering construction of the precast pile; s4, monitoring feedback to dynamically adjust the construction sequence and finishing stress release through the stress release groove and the stress release hole; s5, calculating and selecting a proper construction machine tool according to a detection data theory; s6, cleaning the groove and digging the common pit of the local pit.

Description

Construction method for hammering pile sinking of precast pile in deep foundation pit in offshore ultra-thick silt region

Technical Field

The invention relates to the technical field of building construction, in particular to a hammering pile sinking construction method for precast piles in deep foundation pits in offshore ultra-thick silt areas.

Background

Precast piles become the preferred scheme of more pile foundations with the advantages of high construction speed, simple and convenient field management, good quality control and low engineering cost. At present, a method for constructing from the ground is mainly adopted, namely piling is started from the ground before a foundation pit is excavated, a pile-driving technology is adopted to sink the pipe pile into the designed depth, and the construction procedure arrangement of the prestressed pipe pile has the problems that the pile-driving depth is overlarge, precast piles are extremely easy to topple over and damage in the process of excavating foundation pit earthwork, and the like. The deep foundation pit in the offshore ultra-thick silt area is filled with the flowing plastic silt powdery clay, the precast pile is poured when the precast pile is firstly constructed and then the earthwork is excavated, the large-area precast pile is caused to incline in quality accidents, and meanwhile, the engineering cost is greatly increased.

Therefore, how to ensure the safety of the foundation pit in the construction process of the precast pile and reduce the influence of the hammering construction vibration and the stress extrusion of the precast pile in the deep foundation pit on the deep foundation pit support pile is a technical problem to be solved urgently at present.

Disclosure of Invention

The invention aims to provide a construction method for hammering and pile sinking of precast piles in a deep foundation pit in an offshore ultra-thick silt region, which aims to solve the problem of how to ensure the safety of the foundation pit in the construction process of the precast piles and reduce the influence of hammering construction vibration and stress extrusion of the precast piles in the deep foundation pit on a deep foundation pit supporting pile.

The technical task of the invention is realized in the following manner, namely a pile-hammering construction method for precast piles in deep foundation pits in offshore ultra-thick silt areas, which comprises the following steps:

s1, installing an inclinometer and automatic foundation pit detection equipment;

s2, constructing stress release holes and stress release grooves;

s3, hammering construction of the precast pile;

s4, monitoring feedback to dynamically adjust the construction sequence and finishing stress release through the stress release groove and the stress release hole;

s5, calculating and selecting a proper construction machine tool according to a detection data theory;

s6, cleaning the groove and digging the common pit of the local pit.

Preferably, the installation inclinometer and the automatic foundation pit detection device in step S1 are specifically as follows:

s101, installing a deep foundation pit supporting pile in an ultra-thick silt area;

s102, installing a static level gauge for automatic observation and an inclination sensor on a crown beam;

s103, installing an axial force meter on the anchor rod, pre-burying an inclinometer pipe, and then pre-excavating earthwork;

s104, observing the influence of the excavation of the upper soil on the lower soil in the earthwork excavation process, detecting the soil movement through an inclinometer, carrying out theoretical analysis on the influence of the earthwork excavation on the pile body stress of the precast pile in the silt layer and the influence of the machine on the pile so as to guide construction, and avoiding pile foundation inclination damage caused by mechanical deflection.

More preferably, the construction stress relief hole and the stress relief groove in step S2 are specifically as follows:

s201, leveling mucky soil within a range of 3m around the foundation pit;

s202, stress relief ditch excavation and correction;

s203, draining accumulated water;

s204, positioning a drilling machine;

s205, forming holes, simultaneously installing PVC (four-side punching) plastic pipes and pouring coarse sand around the plastic pipes: when the stress release holes are constructed, the circle construction is carried out in a skip mode of three-in-one punching, holes are sequentially punched in sequence, and the PVC plastic pipe and sand filling treatment are carried out in time after the stress release holes are punched;

s206, shifting the drilling machine;

s207, cleaning the site after construction is finished.

More preferably, the stress relief trench excavation correction in step S202 is specifically as follows:

s20201, in order to ensure that the soil squeezing effect is weakened in the construction process of the prefabricated engineering square piles of the civil air defense garage, the stress release requirements are met, stress release holes are arranged on the periphery of the inner side of a crown beam of the garage, the diameter of each stress release hole is 300mm, the distance is 1000mm, PVC plastic pipes with the diameter of 50mm are placed in the middle, coarse sand is filled between each PVC plastic pipe and the hole wall, and the PVC plastic pipes are exposed for 300mm;

s20202, the stress relief groove is 1m wide and 1.5 m deep; the construction of the stress release holes is adjusted in time according to the observation result, and if the soil displacement is still greater than an alarm value in the pile sinking process after the construction, the number of holes is increased on the basis of the original layout. The principle is to consider that the hole sites which are multiplied between the inner row holes adjacent to the construction area are increased first, so that the economical efficiency of the protection effect is guaranteed to the greatest extent.

More preferably, the accumulated water removal in step S203 is specifically as follows:

s20301, firstly excavating to a position 50cm lower than a garage cushion layer along the foundation pit edge, paving a circle of stones, and placing a drain pipe with soil to enter a blockage;

s20302, placing the PVC-U corrugated pipe with the hole on the pipe wall along a ditch, and reserving 11 positions for building the water collecting well in the middle;

s20303, finishing the construction of the equal water collecting well, covering a 850mm stone water filtering layer on the PVC-U corrugated pipe, and then backfilling with gravel to-2.61 m;

s20304, placing a water pump in the water collecting pit to pump water, and timely discharging the squeezed water after piling.

More preferably, the precast pile hammering pile sinking construction in the step S3 is specifically as follows:

s301, backfilling gravel soil;

s302, leveling a field;

s303, measuring and lofting;

s304, pile foundation positioning;

s305, pile sinking; the method comprises the following steps:

s30501, hammering and tapping, namely enabling piles to be kept vertical under the inspection of two theodolites, and formally sinking the piles when no abnormality exists;

s30502, when hammering is started, the drop distance is smaller, and when the pile is buried to a certain depth and stabilized, the pile is sunk according to the required drop distance; the hammer is suitable for piling and low-impact, and the hammer weight is selected according to geological conditions, pile types, structures, density and construction conditions; according to the density of piles, the pile driving sequence can be symmetrically applied from the middle to two sides or from the middle to the periphery;

s30503, hammering pile sinking, wherein a steel wire rope formed by stacking vertical hard wood or coiled wires is used as a hammer pad between a pile cap and a pile hammer, and the thickness of the steel wire rope is 150-200 mm;

s306, pile sinking is carried out in place;

s307, pile extension or pile cutting;

s308, pile inspection.

More preferably, the pile sinking in step S305 is specifically as follows:

s30501, hammering and tapping, namely enabling piles to be kept vertical under the inspection of two theodolites, and formally sinking the piles when no abnormality exists;

s30502, when hammering is started, the drop distance is smaller, and when the pile is buried to a certain depth and stabilized, the pile is sunk according to the required drop distance; the hammer is suitable for piling and low-impact, and the hammer weight is selected according to geological conditions, pile types, structures, density and construction conditions; according to the density of piles, the pile driving sequence can be symmetrically applied from the middle to two sides or from the middle to the periphery;

s30503, hammering pile sinking, wherein a steel wire rope formed by stacking vertical hard wood or coiled wires is used as a hammer pad between the pile cap and the pile hammer, and the thickness of the steel wire rope is 150-200mm.

More preferably, the monitoring feedback in step S4 dynamically adjusts the construction sequence and completes the stress release through the stress release groove and the stress release hole as follows:

s401, performing deformation observation in real time from the beginning of excavation to the completion of precast pile construction by adopting an automatic foundation pit deformation monitoring system;

s402, the automatic foundation pit deformation monitoring system sends data acquired by a sensor to a cloud platform in real time through an intelligent node by utilizing a 4G/5G network to realize instant early warning and alarming, and the monitored data is counted and processed to automatically generate corresponding curves and reports;

s403, timely adjusting the construction sequence and drainage in the stress release hole through detection data to ensure the stability of the support structure.

More preferably, in the step S5, the selection of a proper construction machine tool according to the detection data theory refers to that through the selected mechanical equipment, the pile foundation dumping caused by earth excavation is avoided in the process of cleaning the pit, collecting the pit and excavating the partial pit of the reclaimed water treatment station by the reversely pushing precast pile; the method comprises the following steps:

s501, excavator: a large-sized 300-type backhoe excavator, a 260-type long-arm excavator and a small-sized 60-type excavator are adopted;

when a Xu Gong XE215CA excavator is used in a foundation pit, the total weight of the excavator is 21750kg, the total length is 9565mm, the track wheelbase is 3462mm, the minimum turning radius is 3.5m, and the estimated excavator load is as follows:

s502, an earthmoving vehicle: the earthwork is carried out by adopting front four and rear eight dump trucks, and the total axle weight of the rear wheel double-axle is 600kN; assuming that the wheel distance at the outer side of the automobile is 3.5m from the slope top line of the foundation pit, when the action of the equivalent distributed load of the automobile is calculated, the diffusion angle of the wheel diffusion pressure is 30 degrees, and the diffusion area of the wheel pressure of the rear wheel double bridge is (2.4+2×3.5) × (1.6+2×3.5) = 71.44m ² ；

The equivalent distributed load of the automobile is:

therefore, the minimum turning radius of the 21t excavator is 3.5m, and the equivalent load of the excavator is 6.34kPa; if the wheel distance of the outer side of the earthwork vehicle is 3.5m from the slope top line of the foundation pit, the equivalent load of the vehicle is 8.4kPa; since the automobile and the excavator cannot act on one at the same time, the depth of the embedded rock is L _d =1.5b can meet the requirement; the construction machine comprises a full-load large excavator and an earthmoving vehicle, and is matched with a working steel plate in mucky soil, wherein the size of the working steel plate is 6000 x 2000 x 20mm; paving the pavement with the grain steel plate with the size of 4000-2000-5 mm, so as to meet the requirements;

s503, determining that the construction excavator adopts a large 300-type backhoe excavator, a 260-type long-arm excavator and a small 60-type excavator; the earth transporting vehicle adopts four front and eight rear earth-moving vehicles, and is equipped with a small farm vehicle for emergency matching.

More preferably, the pit cleaning and partial pit common pit excavation in the step S6 is specifically as follows:

s601, determining an excavation sequence: 1-1, 2-1, 1-2- > 2-2, 1-3, 2-3- > 1-4, 2-4, 1-5- > 2-5, 1-6, 2-6- > 1-7, 2-7- > 1-8;

s602, constructing two digging machines simultaneously.

The construction method for hammering and pile sinking of the precast pile in the deep foundation pit in the offshore ultra-thick silt region has the following advantages:

when the foundation pit support in the silt area is constructed, a static level gauge and an inclination angle sensor are arranged on a crown beam, an anchor force meter is arranged on a self-advancing anchor rod, and a Hua building automatic online monitoring system is adopted, so that continuous, real-time and online monitoring and timely pre-alarming reminding are realized, and the safety of the foundation pit in the process of hammering precast piles and earth excavation in the deep foundation pit is ensured;

secondly, analyzing the influence of the excavation unloading on the soil displacement and the change rate by using an installation inclinometry pile test, quantitatively analyzing the influence of the excavation unloading on the precast pile according to the displacement change rule of the soil around the pile, and verifying the excavation construction method of the mucky soil precast pile by theoretical calculation; a stress release groove and a stress release hole are formed in the periphery of the deep foundation pit; the stress release is completed while the precast pile is constructed, so that the problems of soil squeezing effect and influence of vibration impact on the supporting structure caused by hammering the pile sinking are solved;

thirdly, the construction of the stress release holes is adjusted in time according to the observation result, if the soil displacement is still larger than an alarm value in the pile sinking process after the construction, the number of the holes is increased on the basis of the original layout; the principle is that the hole sites with multiple times are added among the inner row holes adjacent to the construction area are considered at first, so that the economical efficiency of the protection effect is guaranteed to the greatest extent;

the automatic on-line monitoring system, the stress release ditch and the stress release hole technology are adopted, the horizontal displacement of the top of the supporting structure, the tension of the anchor rod and the underground water level are monitored in real time, the safety of a foundation pit in the construction process of the precast pile is ensured, and the influence of hammering construction vibration and stress extrusion of the precast pile in the deep foundation pit on the deep foundation pit supporting pile is effectively reduced;

the deformation, the strength and the stability of the foundation pit supporting structure are automatically monitored when the precast pile is applied in the construction process, the foundation pit supporting deformation of a construction site is known in time through monitoring data, the safety evaluation is carried out on the integral stability and the deformation of the foundation pit, the reason for generating the deformation is analyzed, the construction is fed back in time, the construction steps and the stress release holes are adjusted, the precipitation stress is released, and therefore the construction safety is further ensured;

according to the invention, after the foundation pit is excavated in the earthwork, stress release holes are formed in the periphery of the foundation pit, pressure-bearing water in the medium coarse sand layer is relieved, the soil squeezing effect of precast pile construction is released by the stress release holes, so that the problem that precast concrete piles in deep foundation pits are extremely easy to cause the soil squeezing effect to cause foundation pit support collapse, namely the phenomenon of 'dumpling making', is solved, the construction quality of precast piles is ensured, meanwhile, the influence of excavation unloading on the size and change rate of soil displacement is analyzed by means of installation inclinometry pile test, the excavating construction method of the mucky soil precast piles is verified through theoretical calculation, and the optimal mucky soil excavating scheme is selected.

Drawings

The invention is further described below with reference to the accompanying drawings.

FIG. 1 is a schematic structure diagram of a construction method for hammering and pile sinking of precast piles in a deep foundation pit in an offshore ultra-thick silt region;

FIG. 2 is a schematic diagram of construction of prefabricated engineering square piles of the civil air defense garage;

fig. 3 is a schematic diagram of a small ash brick masonry water collection well phi 2000 with 240 x 115 x 53;

fig. 4 is a schematic diagram of a small ash brick masonry water collection well phi 1000 of 240 x 115 x 53;

FIG. 5 is an interface screenshot of a cumulative change time chart;

FIG. 6 is an interface screenshot of a single change amount time table;

FIG. 7 is a line graph of side shift versus depth of burial;

FIG. 8 is a plot of side shift versus time;

fig. 9 is a schematic diagram of an excavation sequence.

In the figure: 1. the static leveling instrument comprises a static leveling instrument 2, a water level observation instrument 3, an axial force meter 4, an inclination angle sensor 5, a stress release hole 6, a stress release ditch 7, coarse sand 8, an engineering pile 9, a PVC plastic pipe 10, a drainage ditch 11, a stone filter layer 12, gravel soil 13, a garage main body structure 14 and a PVC-U corrugated pipe.

Detailed Description

The method for driving and sinking the precast pile in the deep foundation pit in the offshore ultra-thick silt region according to the present invention will be described in detail below with reference to the accompanying drawings and specific examples.

In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, only for convenience in describing the present invention and simplifying the description. Rather than indicating or implying that the apparatus or elements herein referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

Examples:

as shown in figure 1, the method for hammering pile sinking construction of precast piles in deep foundation pits in offshore ultra-thick silt areas comprises the following steps:

s1, installing an inclinometer and automatic foundation pit detection equipment;

s2, constructing stress release holes and stress release grooves;

s3, hammering construction of the precast pile;

s4, monitoring feedback to dynamically adjust the construction sequence and finishing stress release through the stress release groove and the stress release hole;

s5, calculating and selecting a proper construction machine tool according to a detection data theory;

s6, cleaning the groove and digging the common pit of the local pit.

The installation inclinometer and the automatic foundation pit detection device in step S1 in this embodiment are specifically as follows:

s101, installing a deep foundation pit supporting pile in an ultra-thick silt area;

s102, installing a static level 1 and an inclination sensor 4 for automatic observation on a crown beam;

s103, installing an axial force meter 3 on the anchor rod, pre-burying an inclinometer pipe, and then pre-excavating earthwork;

s104, observing the influence of the excavation of the upper soil on the lower soil in the earthwork excavation process, detecting the soil movement through an inclinometer, carrying out theoretical analysis on the influence of the earthwork excavation on the pile body stress of the precast pile in the silt layer and the influence of the machine on the pile so as to guide construction, and avoiding pile foundation inclination damage caused by mechanical deflection.

The construction stress relief hole and the stress relief groove in step S2 in this embodiment are specifically as follows:

s201, leveling mucky soil within a range of 3m around the foundation pit;

s202, excavating and correcting a stress release ditch 6;

s203, draining accumulated water: the water level depth is measured by the water level observer 2, so that timely drainage can be ensured;

s204, positioning a drilling machine;

s205, forming holes, simultaneously installing PVC (four-side punching) plastic pipes 9 and pouring coarse sand 7 around the plastic pipes: when the stress release holes 5 are constructed, the construction of the swivel is carried out in a skip mode of three-in-one punching, holes are sequentially punched in sequence, and the stress release holes 5 are punched to timely carry out PVC plastic pipe 9 and sand filling treatment;

s206, shifting the drilling machine;

s207, cleaning the site after construction is finished.

The stress relief trench excavation correction in step S202 in this embodiment is specifically as follows:

s20201, in order to ensure that the soil squeezing effect is weakened in the construction process of the prefabricated engineering square piles of the civil air defense garage, the stress release requirements are met, stress release holes 5 are arranged on the periphery of the inner side of a crown beam of the garage, the diameters of the stress release holes 5 are 300mm, the distance is 1000mm, PVC plastic pipes 9 with the diameters of 50mm are placed in the middle, coarse sand 7 is filled between the PVC plastic pipes 9 and the hole walls, and the PVC plastic pipes 9 are exposed for 300mm;

s20202, the stress relief grooves 6 are 1m wide and 1.5 m deep, as shown in figure 2; the depth of the stress relief hole 5 is the same as that of the engineering pile 8, and the depth of the stress relief hole 5 is 13.5 meters. The construction of the stress release holes 5 should be adjusted in time according to the observation result, if the soil displacement is still greater than the alarm value in the pile sinking process after the construction, the hole number should be increased on the basis of the original layout. The principle is to consider that the hole sites which are multiplied between the inner row holes adjacent to the construction area are increased first, so that the economical efficiency of the protection effect is guaranteed to the greatest extent.

The accumulated water removal in step S203 in this embodiment is specifically as follows:

s20301, firstly excavating to a position 50cm lower than a garage cushion layer along the foundation pit edge, paving a circle of stones, and placing a drain pipe with soil to enter a blockage;

s20302, placing the PVC-U corrugated pipe 14 with the pipe wall provided with holes along a ditch, and reserving 11 positions for building water collecting wells in the middle;

s20303, finishing the construction of the equal water collecting well, covering a 850mm stone water filtering layer 11 on a PVC-U corrugated pipe 14, and then replacing and filling with gravel 12 to-2.61 m;

s20304, placing a water pump in the water collecting pit to pump water, and timely discharging the squeezed water after piling.

As shown in fig. 3, a stone filter layer 11 is replaced and filled along the periphery of a foundation pit at a main structure 13 of the garage, a phi 200mmPVC-U corrugated pipe 14 (the space around the pipe is 100mm phi 10mm holes) is buried; the stone filter layer 11 is replaced and filled along the periphery of the foundation pit, and the depth is 850mm; drainage ditches 10 are excavated along the periphery of the foundation pit, and the size is 1500mm 2000mm.

As shown in fig. 4, the water collection wells phi 1000mm and the depth 2m are built by 240 x 115 x 53 small bricks.

The pile driving construction of the precast pile in step S3 in this embodiment is specifically as follows:

s301, backfilling gravel soil 12;

s302, leveling a field;

s303, measuring and lofting;

s304, pile foundation positioning;

s305, pile sinking; the method comprises the following steps:

s30501, hammering and tapping, namely enabling piles to be kept vertical under the inspection of two theodolites, and formally sinking the piles when no abnormality exists;

s30502, when hammering is started, the drop distance is smaller, and when the pile is buried to a certain depth and stabilized, the pile is sunk according to the required drop distance; the hammer is suitable for piling and low-impact, and the hammer weight is selected according to geological conditions, pile types, structures, density and construction conditions; according to the density of piles, the pile driving sequence can be symmetrically applied from the middle to two sides or from the middle to the periphery;

s30503, hammering pile sinking, wherein a steel wire rope formed by stacking vertical hard wood or coiled wires is used as a hammer pad between a pile cap and a pile hammer, and the thickness of the steel wire rope is 150-200 mm;

s306, pile sinking is carried out in place;

s307, pile extension or pile cutting;

s308, pile inspection.

The pile sinking in step S305 in this embodiment is specifically as follows:

s30501, hammering and tapping, namely enabling piles to be kept vertical under the inspection of two theodolites, and formally sinking the piles when no abnormality exists;

s30502, when hammering is started, the drop distance is smaller, and when the pile is buried to a certain depth and stabilized, the pile is sunk according to the required drop distance; the hammer is suitable for piling and low-impact, and the hammer weight is selected according to geological conditions, pile types, structures, density and construction conditions; according to the density of piles, the pile driving sequence can be symmetrically applied from the middle to two sides or from the middle to the periphery;

s30503, hammering pile sinking, wherein a steel wire rope formed by stacking vertical hard wood or coiled wires is used as a hammer pad between the pile cap and the pile hammer, and the thickness of the steel wire rope is 150-200mm.

As shown in fig. 5 and 6, the monitoring feedback in step S4 in the present embodiment dynamically adjusts the construction sequence and completes the stress release through the stress release groove and the stress release hole specifically as follows:

s401, performing deformation observation in real time from the beginning of excavation to the completion of precast pile construction by adopting an automatic foundation pit deformation monitoring system;

s402, the automatic foundation pit deformation monitoring system sends data acquired by a sensor to a cloud platform in real time through an intelligent node by utilizing a 4G/5G network to realize instant early warning and alarming, and the monitored data is counted and processed to automatically generate corresponding curves and reports;

s403, timely adjusting the construction sequence and drainage in the stress release hole through detection data to ensure the stability of the support structure.

In step S5 in this embodiment, the selection of a suitable construction tool according to the detection data theory is specifically as follows:

the change curve of displacement along with the increase of the burial depth can be seen through 6 measuring points which are arranged on the support pile in a test of the installation side inclinometer, as shown in figure 7, wherein each reference mark is inserted into the change curve of displacement along with time when the reference marks are respectively 4m,6m, 7m, 7.5m and 8m, the data of the measuring point on the first day is the initial offset of the inclinometer, and the displacement on the first day is subtracted from the displacement measured every day later to obtain the sliding displacement of the final soil. A feature point is taken as representative.

The displacement change in the 4m under the excavation surface is obvious, the influence of soil unloading and construction is larger, the influence of the outside is smaller outside in the 4m under the excavation surface, mainly the influence of foundation pit excavation is smaller, and the displacement of the soil body under 4m is smaller and basically unchanged. Wherein the general regularity of the shift from day 4 to day 25 labels 2, 4, 6 at 4m,6m, 7m, 7.5m, 8m is the same, as is the regularity of 1, 3, 5. The data from the 4 th to 25 th day marks show that the change is apparent at 4m and 6m, then gradually stabilizes, and the displacement is substantially unchanged at 8m, approximately 0.

As shown in figure 8, along with the excavation of the foundation pit, the soil body can displace, the influence depth on the soil body is in the range of 8m, along with the excavation depth, the soil body is greatly influenced by the excavation, the displacement is larger, the soil body gradually tends to be stable after 6m, the soil body is basically stable after 8m, and the excavation of the soil body has less influence on the soil body.

In the step S5 of the present embodiment, selecting a suitable construction machine according to the detection data theory refers to that by using a selected mechanical device, the pile foundation is prevented from dumping due to earth excavation during the process of cleaning the pit, collecting pit and partial pit excavation of the reclaimed water treatment station; the method comprises the following steps:

s501, excavator: a large-sized 300-type backhoe excavator, a 260-type long-arm excavator and a small-sized 60-type excavator are adopted;

when a Xu Gong XE215CA excavator is used in a foundation pit, the total weight of the excavator is 21750kg, the total length is 9565mm, the track wheelbase is 3462mm, the minimum turning radius is 3.5m, and the estimated excavator load is as follows:

s502, an earthmoving vehicle: the earthwork is carried out by adopting front four and rear eight dump trucks, and the total axle weight of the rear wheel double-axle is 600kN; assuming that the wheel distance at the outer side of the automobile is 3.5m from the slope top line of the foundation pit, when the action of the equivalent distributed load of the automobile is calculated, the diffusion angle of the wheel diffusion pressure is 30 degrees, and the diffusion area of the wheel pressure of the rear wheel double bridge is (2.4+2×3.5) × (1.6+2×3.5) = 71.44m ² ；

The equivalent distributed load of the automobile is:

therefore, the minimum turning radius of the 21t excavator is 3.5m, and the equivalent load of the excavator is 6.34kPa; if the wheel distance of the outer side of the earthwork vehicle is 3.5m from the slope top line of the foundation pit, the equivalent load of the vehicle is 8.4kPa; since the automobile and the excavator cannot act on one at the same time, the depth of the embedded rock is L _d =1.5b can meet the requirement; the construction machine comprises a full-load large excavator and an earthmoving vehicle, and is matched with a working steel plate in mucky soil, wherein the size of the working steel plate is 6000 x 2000 x 20mm; paving the pavement with the grain steel plate with the size of 4000-2000-5 mm, so as to meet the requirements;

s503, determining that the construction excavator adopts a large 300-type backhoe excavator, a 260-type long-arm excavator and a small 60-type excavator; the earth transporting vehicle adopts four front and eight rear earth-moving vehicles, and is equipped with a small farm vehicle for emergency matching.

The pit cleaning and partial pit common pit excavation in step S6 in this embodiment is specifically as follows:

s601, determining an excavation sequence: 1-1, 2-1, 1-2- > 2-2, 1-3, 2-3- > 1-4, 2-4, 1-5- > 2-5, 1-6, 2-6- > 1-7, 2-7- > 1-8, as shown in figure 9;

s602, constructing two digging machines simultaneously.

The material and the equipment related to the invention comprise:

1. the main construction machine tool comprises:

2. main measuring equipment

Level, theodolite, total station, tape measure, etc.;

3. main construction material

The quality control of the invention is as follows:

1. the method achieves relevant specifications and regulations of unified standards for construction quality inspection of building engineering GB50300-2013, technical regulations for supporting foundation pit of building JGJ120-2012, technical regulations for inspection of construction quality inspection of foundation engineering of building GB50202-2018, technical regulations for inspection of foundation pit of building GB50497-2009, and regulations for supervision of construction engineering GB/T-5039-2013.

2. Material quality control

201. Material assurance measures

The preparation and related inspection work of the preliminary spare parts of the materials are strictly carried out according to the required time by the users, so that the materials are ensured to enter the field in time and are inspected and accepted in time.

202. Construction quality requirements of engineering materials

A. Before construction, materials, equipment materials, specifications, models and the like are checked, and after the checking, construction is performed strictly according to design requirements and construction specifications.

B. When the construction is carried out, the construction preparation work is needed to be fully carried out, and the construction is closely matched with each professional coordination construction so as to carry out the process crossing and lap joint work, ensure the normal operation of foundation pit support and avoid reworking.

3. Construction quality control

301. And (3) construction of precast piles: and (3) constructing according to the drawing set L15G329 of the construction quality acceptance criterion of the foundation engineering of the building foundation and the prefabricated high-strength concrete square pile. Pile top elevation deviation is +/-100 mm, and axial and vertical axial direction deviation is +/-50 mm. The verticality deviation is 1%.

302. Foundation pit earthwork construction: the construction should follow the principle of sectioning excavation and sectioning support, and the construction should not be carried out in a mode of once excavation and support; before construction, the position, drilling depth, diameter, angle length, grouting proportion, pressure, grouting amount, strength and the like of the anchor are checked, so that the design requirements are met.

The safety measures of the invention are as follows:

1. in the construction process, the border enclosure of the foundation pit opening is timely made, and high-altitude throwing and falling prevention are forbidden.

2. Foundation pit excavation should be carried out in layers, and the height difference should not be too large. The softer the soil, the smaller the height difference should be.

3. The special operator must pass the training examination and hold the certificate on duty.

4. The pile is fed into the field to discharge and lift, and the lifting point and the field storage are stable and safe.

5. The position of the operator below is noted in the pile body butt joint process, and the position is not in the range of the hydraulic pipe.

6. The electric welder and the mechanical equipment are protected by the site power. The professional electrician is responsible for the electricity safety during construction and periodically organizes the inspection of related personnel.

7. The overload operation is strictly forbidden by piling, the moment is not accurate, and the elevation angle is not beyond the limit, so that the accident of turning over can be prevented.

8. And when the fight event occurs after the drunk and the working is forbidden, the fight event is started to return to the ground immediately after the fight event is found.

9. Personnel entering the scene must wear a safety helmet without working against rules at any time. Smoking is strictly forbidden in the construction site.

The benefit analysis of the invention is as follows: taking the engineering as an example, compared with a cast-in-place pile in a deep foundation pit, the economic benefit analysis of precast pile construction is shown in the table:

one prefabricated square pile is 16 m long, and 1150 piles are 18400 m long.

Compared with the common precast pile construction, the method has the advantages of saving the construction cost by 1150 x 15%, 256 x 16+900000-42100-12520= 1551940 yuan and better economic benefit.

10.2 social and environmental benefits:

the construction method effectively solves the construction problems of large-area dumping, shifting and the like of the precast pile in the deep foundation pit in the offshore ultra-thick silt region in the excavation process, also solves the adverse effect of the soil compaction effect of the precast pile in the foundation pit on the foundation pit support, indirectly plays the role of drainage and precipitation, and ensures the construction quality of the precast pile. Meanwhile, the construction method can be used for hammering and conveying the prefabricated engineering pile, so that the perpendicularity is guaranteed, and the bearing capacity of the pile body and the bearing platform is guaranteed without taking other measures. The perfect combination of the construction progress and the quality can be quickened, and meanwhile, the cost and mineral resources are saved; saving auxiliary steel materials and the like. The construction is quick, the construction procedure is reduced, the construction period is shortened, and the unit cost is reduced. Has good social and economic benefits.

Application example:

3.1 Qingdao infant Master and slave projects

3.1.1 engineering profile: the Qingdao infant's high-grade specialty school (first-stage) project is located in Jiaozhou city in the south of the yellow river and in the north of the Huaihe river. The foundation pit excavation range of the engineering is filled with the flowing plastic silt powdery clay, if the precast pile is constructed first and then the earthwork is excavated, the precast pile is poured, so that the large-area precast pile inclination quality accident is caused, and meanwhile, the engineering cost is greatly increased.

3.1.2 construction effects: and an automatic on-line monitoring system, a stress release ditch and a stress release hole technology are adopted. And after the foundation pit is excavated in the earthwork, stress release holes and stress release holes are formed in the periphery of the foundation pit. The influence of excavation unloading on the soil displacement and the change rate is analyzed by means of an installation inclinometer pile test, the construction method of the mucky soil precast pile excavation is verified through theoretical calculation, and the optimal mucky soil excavation scheme is selected.

3.1.3 application effects: by adopting the construction method, the construction progress is quickened, the construction quality of the main structure is ensured, the construction cost is reduced, and the social reputation of our company is improved.

3.2 lan Wenyuan second-phase project

3.2.1 engineering profile: the second-stage project of Guanlan aster is located in Jiaozhou economic and technical development area and is composed of 6# and 7# and 8# and 9# and 10# and B1# and B2# and underground garage. The construction method is used for constructing the pile foundation of the precast pile in the deep foundation pit in the offshore ultra-thick silt area.

3.2.2 construction effects: and the inclination measurement is adopted to analyze the influence generated by the displacement of the pile body, so that the pile driver is properly controlled, and the perfect combination of the pile in the pile driving and pile driving processes is ensured. The pile body has no large deflection after excavation.

3.2.3 application effects: by adopting the invention, the quality accidents of pouring and breakage, large-area inclination and the like of the construction of the precast pile foundation in the deep foundation pit in the offshore ultra-thick silt region are solved, the consistency and the good evaluation of supervision and the first party are obtained, the application prospect is wider, and the method has good popularization significance.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (7)

1. A construction method for hammering and pile sinking of precast piles in deep foundation pits in offshore ultra-thick silt areas is characterized by comprising the following steps:

s1, installing an inclinometer and automatic foundation pit detection equipment; the method comprises the following steps:

s101, installing a deep foundation pit supporting pile in an ultra-thick silt area;

s102, installing a static level gauge for automatic observation and an inclination sensor on a crown beam;

s103, installing an axial force meter on the anchor rod, pre-burying an inclinometer pipe, and then pre-excavating earthwork;

s104, observing the influence of the excavation of the upper soil on the lower soil in the process of earth excavation, and carrying out theoretical analysis on the influence of the earth excavation on the pile body stress of the precast pile in the silt layer and the influence of the machine on the pile by detecting the soil movement through an inclinometer so as to guide construction;

s2, constructing stress release holes and stress release grooves;

s3, hammering construction of the precast pile;

s4, monitoring feedback to dynamically adjust the construction sequence and finishing stress release through the stress release groove and the stress release hole; the method comprises the following steps:

s401, performing deformation observation in real time from the beginning of excavation to the completion of precast pile construction by adopting an automatic foundation pit deformation monitoring system;

s402, the automatic foundation pit deformation monitoring system sends data acquired by a sensor to a cloud platform in real time through an intelligent node by utilizing a 4G/5G network to realize instant early warning and alarming, and the monitored data is counted and processed to automatically generate corresponding curves and reports;

s403, timely adjusting the construction sequence and drainage in the stress release hole according to the detection data to ensure the stability of the support structure;

s5, calculating and selecting a proper construction machine tool according to a detection data theory;

s6, cleaning the groove and digging the common pit of the local pit.

2. The construction method for hammering and pile sinking of precast piles in deep foundation pits in offshore ultra-thick silt areas according to claim 1, wherein the construction stress relief holes and stress relief trenches in step S2 are specifically as follows:

s201, leveling mucky soil within a range of 3m around the foundation pit;

s202, stress relief ditch excavation and correction;

s203, draining accumulated water;

s204, positioning a drilling machine;

s205, forming holes, simultaneously installing a PVC plastic pipe and pouring coarse sand around the plastic pipe: when the stress release holes are constructed, the circle construction is carried out in a skip mode of three-in-one punching, holes are sequentially punched in sequence, and the PVC plastic pipe and sand filling treatment are carried out in time after the stress release holes are punched;

s206, shifting the drilling machine;

s207, cleaning the site after construction is finished.

3. The construction method for hammering and pile sinking of precast piles in deep foundation pits in offshore ultra-thick silt areas according to claim 2, wherein the stress relief trench excavation correction in step S202 is specifically as follows:

s20201, arranging stress release holes around the inner side of a garage crown beam, wherein the stress release holes have a diameter of 300mm and a spacing of 1000mm, arranging a PVC plastic pipe with a diameter of 50mm in the middle, filling coarse sand between the PVC plastic pipe and the hole wall, and exposing the PVC plastic pipe for 300mm;

s20202, the stress relief groove was 1m wide and 1.5 m deep.

4. The construction method for hammering and pile sinking of precast piles in deep foundation pit in offshore ultra-thick silt region according to claim 3, wherein the accumulated water removal in step S203 is specifically as follows:

s20301, firstly excavating to a position 50cm lower than a garage cushion layer along the foundation pit edge, paving a circle of stones, and placing a drain pipe with soil to enter a blockage;

s20302, placing the PVC-U corrugated pipe with the hole on the pipe wall along a ditch, and reserving 11 positions for building the water collecting well in the middle;

s20303, finishing the construction of the equal water collecting well, covering a 850mm stone water filtering layer on the PVC-U corrugated pipe, and then backfilling with gravel to-2.61 m;

s20304, placing a water pump in the water collecting pit to pump water, and timely discharging the squeezed water after piling.

5. The construction method for hammering and pile sinking of precast piles in deep foundation pits in offshore ultra-thick silt areas according to claim 4, wherein the construction method for hammering and pile sinking of precast piles in step S3 is specifically as follows:

s301, backfilling gravel soil;

s302, leveling a field;

s303, measuring and lofting;

s304, pile foundation positioning;

s305, pile sinking;

s306, pile sinking is carried out in place;

s307, pile extension or pile cutting;

s308, pile inspection.

6. The construction method for hammering and pile sinking of prefabricated piles in deep foundation pit in offshore ultra-thick silt region according to claim 5, wherein pile sinking in step S305 is specifically as follows:

s30501, hammering and tapping, namely enabling piles to be kept vertical under the inspection of two theodolites, and formally sinking the piles when no abnormality exists;

s30502, when hammering is started, a hammer is suitable for hammering, and the hammer weight is selected according to geological conditions, pile types, structures, density and construction conditions; according to the density of piles, the pile driving sequence adopts symmetrically driving from the middle to two sides or driving from the middle to the periphery;

s30503, hammering pile sinking, wherein a steel wire rope formed by stacking vertical hard wood or coiled wires is used as a hammer pad between the pile cap and the pile hammer, and the thickness of the steel wire rope is 150-200mm.

7. The construction method for hammering and pile sinking of precast piles in deep foundation pits in offshore ultra-thick silt areas according to claim 6, wherein in the step S5, proper construction machines are calculated and selected according to detection data theory, namely pile foundation dumping caused by earth excavation is avoided in the process of dredging a pit, a water pit and a local pit of a reclaimed water treatment station by reversely pushing the precast piles through selected mechanical equipment; the method comprises the following steps:

s501, excavator: a large-sized 300-type backhoe excavator, a 260-type long-arm excavator and a small-sized 60-type excavator are adopted;

when a Xu Gong XE215CA excavator is used in a foundation pit, the total weight of the excavator is 21750kg, the total length is 9565mm, the track wheelbase is 3462mm, the minimum turning radius is 3.5m, and the estimated excavator load is as follows:

s502, an earthmoving vehicle: the earthwork is carried out by adopting front four and rear eight dump trucks, and the total axle weight of the rear wheel double-axle is 600kN; assuming that the wheel distance at the outer side of the automobile is 3.5m from the slope top line of the foundation pit, when the action of the equivalent distributed load of the automobile is calculated, the diffusion angle of the wheel diffusion pressure is 30 degrees, and the diffusion area of the wheel pressure of the rear wheel double bridge is (2.4+2×3.5) × (1.6+2×3.5) = 71.44m ² ；

The equivalent distributed load of the automobile is:

therefore, the minimum turning radius of the 21t excavator is 3.5m, and the equivalent load of the excavator is 6.34kPa; if the wheel distance of the outer side of the earthwork vehicle is 3.5m from the slope top line of the foundation pit, the equivalent load of the vehicle is 8.4kPa; since the automobile and the excavator cannot act on one at the same time, the depth of the embedded rock is L _d =1.5b can meet the requirement; the construction machine comprises a full-load large excavator and an earthmoving vehicle, and is matched with a working steel plate in mucky soil, wherein the size of the working steel plate is 6000 x 2000 x 20mm; paving the pavement with the grain steel plate with the size of 4000-2000-5 mm, so as to meet the requirements;

s503, determining that the construction excavator adopts a large 300-type backhoe excavator, a 260-type long-arm excavator and a small 60-type excavator; the earth transporting vehicle adopts four front and eight rear earth-moving vehicles, and is equipped with a small farm vehicle for emergency matching.