CN113914327A

CN113914327A - Construction method for foundation pit enclosure and earth excavation

Info

Publication number: CN113914327A
Application number: CN202111311088.5A
Authority: CN
Inventors: 鲍佳佳; 段海涛; 莫国军; 刘启龙; 马根宝
Original assignee: Zhejiang Qiaoxing Construction Group Co ltd
Current assignee: Zhejiang Qiaoxing Construction Group Co ltd
Priority date: 2021-11-08
Filing date: 2021-11-08
Publication date: 2022-01-11
Also published as: WO2023077552A1

Abstract

A construction method for foundation pit enclosure and earthwork excavation comprises the following steps: designing a construction drawing and reviewing the drawing, preparing a construction site, arranging a support enclosure, arranging a drainage measure, excavating earthwork, pouring a cushion layer, a bottom plate and a force transmission belt, removing the support, completing the construction of a basement structure, backfilling earthwork, and grouting after pile pulling; compared with the prior art, when the enclosure construction quality is emphasized, reasonable and reliable foundation reinforcement measures in a pit are adopted, accumulated water in the foundation pit is timely taken out, the foundation pit has better stability in the whole pit digging process, the excavation is segmented and layered from top to bottom and is sequentially carried out, the slope is reasonably controlled, the cutting slope foot is prevented from preventing and treating the instability of the slope, and better safety is realized.

Description

Construction method for foundation pit enclosure and earth excavation

Technical Field

The invention relates to the technical field of foundation pit construction, in particular to a construction method for foundation pit enclosure and earthwork excavation.

Background

In the process of excavation of a foundation pit, in order to prevent or reduce collapse of the foundation pit, a building enclosure structure is usually manufactured around the foundation pit, Larsen steel plate piles are common foundation pit building enclosure materials, a plurality of Larsen steel plates are driven into a soil layer to carry out building enclosure of the edge of the foundation pit, the Larsen steel plate piles form a closed shape on the peripheral wall of the foundation pit, and two adjacent Larsen steel plate piles are mutually spliced and matched.

With the development of urban construction, the utilization of underground space becomes more and more important, and the excavation and the enclosure of a deep foundation pit also become the most important. Because the Larsen steel sheet pile has certain flexibility, the pure foundation pit enclosure structure of the Larsen steel sheet pile cannot meet the strength requirement of foundation pit support, and the Larsen steel sheet pile can be bent or even damaged.

The PC method is carried out under the above requirements of construction conditions. The PC construction method is the combination of a steel pipe pile and a Larsen steel plate pile, and has stronger supporting strength and stability. Cutting off the connecting pieces on two sides of the Larsen steel sheet pile, welding the connecting pieces on two sides of the steel pipe pile to form lock catches, sequentially driving the steel pipe pile and the Larsen steel sheet pile into a soil layer, and simultaneously enabling the lock catches on the steel pipe pile to be in inserting fit with the connecting pieces on the Larsen steel sheet pile.

Chinese patent No. CN108612111A discloses a steel pipe pile, a foundation pit enclosure structure and a construction method of the foundation pit enclosure structure, wherein the method comprises the following steps: s1, driving the steel pipe pile into a soil layer; the steel pipe pile comprises a pile body and two lock catches, and the two lock catches are positioned on the same diameter of the section of the steel pipe pile; a flushing pipe is additionally arranged on the lock catch; high-pressure water is flushed into the soil layer through the flushing pipe in the process of driving the steel pipe pile into the soil layer; s2, aligning the connecting piece of the Larsen steel sheet pile with the lock catch in an inserting mode, and driving the Larsen steel sheet pile into a soil layer; the depth of the Larsen steel sheet pile entering the soil layer is smaller than that of the steel pipe pile entering the soil layer; s3, sequentially driving a steel pipe pile and 1-2 Larsen steel plate piles to form closed enclosure units according to the method, wherein the end parts of the enclosure units are connected with each other to form a foundation pit enclosure structure.

The disclosed foundation pit support structure is constructed in a mode of a PC construction method, and the problems of water leakage easily caused by perpendicularity deviation, pile top elevation deviation, and the like easily occur in the construction process of the PC construction method, so that certain potential safety hazards exist.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a construction method for foundation pit enclosure and earth excavation, which is safe, reliable, efficient and stable in structure.

In order to achieve the purpose, the invention adopts the following technical scheme: a construction method for foundation pit enclosure and earthwork excavation comprises the following steps:

and A, designing a construction drawing and reviewing the drawing, designing the drawing of the area needing to be dug on the spot, and auditing the designed drawing.

And B: preparing a construction site, leveling the site and the designed elevation, arranging the construction site and a site road, and arranging a site access, a vehicle cleaning point, site hardening, a site drainage point, a reinforcement cage processing platform and a reinforcement stock yard.

And step C, arranging a support enclosure, combining the piles and the concrete section steel by adopting a PC construction method, and comprising a surrounding support system, pit internal reinforcement, a corner support structure, a symmetrical structure and a stand column structure.

Step D: and arranging drainage measures, drainage ditches and water collecting wells, and arranging a pipe well gravity flow dewatering well in the foundation pit.

Step E: and carrying out earth excavation, wherein the earth excavation construction process sequentially comprises side slope excavation, side slope protection and poking treatment, capping beam and inner support construction, construction and transportation channel building, segmented excavation of the earth excavation to the bottom of the cushion layer, residual slope protection treatment, manual soil repair of a foundation pit and a groove and sporadic slope treatment.

And F, pouring the cushion layer, the bottom plate and the force transmission belt, pouring the pit bottom cushion layer to the slope toe of the foundation pit, and constructing the force transmission belt simultaneously when pouring and tamping concrete of the foundation bottom plate.

Step G: and (4) dismantling the supports, and dismantling the corner brace structure, the symmetrical structure and the pit internal reinforcement in sequence.

Step H: and D, completing construction of the basement structure, taking the bottom plate in the step F as a basement bottom plate, and setting a basement outer wall and a basement top plate according to the drawing.

Step I: backfilling earthwork, and backfilling and compacting the space between the outer wall and the surrounding support system by using plain soil after the top plate of the basement is constructed; backfilling earthwork or stacking sand bags at the bottom of the foundation pit, performing grouting operation at the bottom of the pit, and externally adding a staggered pipe in the pit and grouting for reinforcement;

step J: the PC method is used for pile pulling operation by adopting a vibration hammer pile pulling mode.

Step K: grouting after pile pulling, backfilling the holes existing after pile pulling, and adopting clay or gravel and compacting and grouting simultaneously.

As a preferred scheme of the invention, a gallery is arranged at the entrance in the step B, and the gallery is reinforced with foundation soil by adopting prestressed concrete pipe piles.

And B, setting a slope placing surface in the process of leveling the field, wherein the construction of the slope placing surface sequentially comprises positioning and paying off, slope digging outside, slope trimming, steel bar anchoring, steel wire net hanging, spraying a first layer of concrete surface protection, laying a steel bar net piece, spraying a second layer of concrete surface protection and maintaining.

As a preferable embodiment of the present invention, the PC construction method composite pile in step C includes steel pipe piles and larsen steel plates connected between adjacent steel pipe piles, a crown beam is disposed at the top of each steel pipe pile, and a bottom mold is disposed between the crown beam and the steel pipe pile.

As a preferable scheme of the present invention, the excavation of the earthwork to the bottom of the bedding layer in the step E includes a first excavation and a second excavation, and the structural strength of the surrounding support system needs to reach 80% before the first excavation.

As a preferred scheme of the present invention, in the earth excavation process in step E, the foundation pit is divided into the corresponding area a and the corresponding area B, and excavation construction is performed on the area a and the area B at the same time.

As a preferred scheme of the invention, a main excavated road and a secondary excavated road are respectively arranged in an area A and an area B according to the excavation direction and the excavated road arrangement, the secondary excavated road is a branch road communicated with the main excavated road, the secondary excavated road is transported to the main excavated road, the secondary excavated road is excavated back towards the central main excavated road, and finally the main excavated road is excavated while retreating and excavating, the road is excavated, and the excavation is carried out in an inclined layered excavation mode, wherein the step shape is from low to high.

As a preferred scheme of the invention, concrete spraying slope protection is adopted in the step E slope protection treatment.

As a preferable scheme of the present invention, the cushion layer in the step F is a concrete cushion layer or a wood pattern.

As a preferred scheme of the invention, in the process of foundation pit excavation and basement construction, the enclosure structure and the surrounding environment are comprehensively monitored and constructed in an informationized way, and the monitoring contents comprise: observing horizontal displacement and settlement of the top of the enclosure wall; observing the lateral deformation of the deep layer of the enclosure wall and the lateral displacement of the deep soil body; observing the supporting axial force; observing horizontal displacement and settlement of the underground pipeline; observing horizontal position, settlement and crack of an adjacent building (structure); and (4) pit and external surface settlement and road crack observation.

Compared with the prior art, the invention has the beneficial effects that: when the enclosure construction quality is emphasized, reasonable and reliable foundation reinforcement measures in the pit are adopted, accumulated water in the foundation pit is timely removed, the foundation pit has better stability in the whole pit digging process, excavation is conducted in a segmented and layered mode from top to bottom in sequence, the slope is reasonably controlled, the cutting slope toe is prevented from preventing and treating slope instability, and better safety is achieved.

Drawings

FIG. 1 is a schematic flow diagram of the present invention;

FIG. 2 is a schematic view showing the installation of a combination pile of a PC construction method and a concrete section steel combination;

FIG. 3 is a view of an earth-excavated road of a foundation pit;

FIG. 4 is a schematic diagram of the division of the foundation pit;

FIG. 5 is a schematic illustration of an earth excavation;

fig. 6 is a front view of a PC construction method composite pile;

FIG. 7 is a cross-sectional view taken along the plane a-a in FIG. 6;

reference numerals: the system comprises a peripheral supporting system 1, a corner support structure 2, a symmetrical structure 3, an in-pit reinforcement 4, a main excavated road 5, a secondary excavated road 6, a first earthwork excavation 7, a second earthwork excavation 8, a drainage ditch 9, a pipe well artesian precipitation well 10, a steel pipe pile 11, a crown beam 12 and a Larsen steel plate 13.

Detailed Description

The following describes embodiments of the present invention in detail with reference to the accompanying drawings.

As shown in fig. 1 to 7, a construction method for foundation pit bracing and earth excavation includes the following steps:

The exit is equipped with the plank road, and the plank road adopts prestressed concrete tubular pile to consolidate the foundation soil, and the access & exit sets up in the relative both sides of foundation ditch, for preventing that a large amount of vehicles frequently come in and go out to damage town road and pipeline around, lays the C20 concrete and lays the steel sheet protection of thickness about 200mm at the gate to set up sign and billboard etc. at the access & exit, guarantee that vehicle personnel pass in and out the peace.

And a circular channel road is arranged at the edge of the foundation pit, the construction road in the site passes through the heavy lane poured with concrete, a drainage ditch is arranged at the roadside, smooth drainage in the site is ensured, and the reinforcing cage processing platform and the reinforcing steel bar stock yard are poured with 200-thick C20 concrete for hardening.

The method comprises the steps of arranging a slope-laying surface in the process of leveling a field, wherein the construction of the slope-laying surface sequentially comprises positioning and paying off, slope outside digging, slope trimming, steel bar anchoring, steel wire net hanging, spraying a first layer of concrete surface protection, laying a steel bar net piece, spraying a second layer of concrete surface protection and maintaining.

When the foundation pit digs soil, the slope surface is mechanically trimmed by the slope-laying part, after the soil is dug, the surface soil is manually shoveled by a shovel, measurement and lofting are carried out before construction, the construction is controlled by a sample plate and is often verified, so that the line type is ensured to be smooth and appropriate, the slope surface is smooth, and the allowable deviation of the flatness is +/-20 mm.

Before the steel wire is hung on the net, firstly, reinforcing steel bars with phi 14 are inserted into the slope along the direction vertical to the slope, the distance between the reinforcing steel bars is 1500mm, the length is 1000mm, the reinforcing steel bars used for laying the reinforcing steel bar net are bidirectional meshes, the connection between the transverse reinforcing steel bars and the connection between the reinforcing steel bar meshes of all construction sections are welded, the reinforcing steel bars are laid along the slope, the reinforcing steel bars are pressed below the locking devices and are welded with the locking reinforcing steel bars into a whole, the reinforcing steel bar net on the side wall extends to the ground surface, and the length of the reinforcing steel bar net is not less than 0.3 m.

The spraying operation is carried out in sections and sections sequentially, the spraying sequence in the same section is from top to bottom, when in spraying, a spray head is vertical to a sprayed surface, the distance is 0.6-1.0m, the mark of sprayed concrete is C20, the spraying thickness is 8cm, the spraying is carried out twice, the thickness of each spraying is 4cm, and the surface of the concrete is kept flat and glossy without dry spots and slip flow after spraying.

During the process of digging a slope, firstly checking the stability of the slope, then removing loose soil and dangerous soil in the slope, and after mechanical excavation, finishing the slope to flatten the slope, removing dust on the slope, ensuring a protective layer when hanging a steel wire mesh, in order to prevent the soil from disintegrating, immediately hanging a net and spraying concrete after the construction of a steel reinforcement framework is finished, in order to control the thickness of the concrete, reinforcing steel bars with the length of 200mm phi 8@3000 x 3000mm can be nailed in the slope before spraying the concrete to be used as a mark for controlling the protective thickness of the concrete, after the mark of the steel reinforcement protective layer is installed, washing the slope with tap water, wetting the surface of the soil layer, and well bonding the concrete and the soil layer together.

And step C, arranging a support enclosure, combining the combined pile and the concrete section steel by adopting a PC construction method, and comprising a surrounding support system 1, a pit internal reinforcement 4, a corner support structure 2, a symmetrical structure 3 and a stand column structure.

The combined pile of the PC construction method comprises steel pipe piles 11 and Larsen steel plates 13 connected between the adjacent steel pipe piles 11, a top beam 12 is arranged at the top of each steel pipe pile 11, a bottom die is arranged between each top beam 12 and each steel pipe pile 11, longitudinal steel bars fixed in a welded mode are arranged in each top beam 12, the bottom die can be a concrete cushion or a wood die, bearing capacity of foundation soil under support must be guaranteed to prevent settlement and cracks of 5mm after concrete is poured, when the concrete cushion is used as the bottom die, isolation measures (such as oil felts and the like are adopted for isolation), and the concrete is removed in time when soil is excavated.

And excavating a guide ditch according to the axis of the steel pipe pile 11, arranging positioning section steel on the edge of the ditch, and marking the insertion positions of the steel pipe pile 11 and the Larsen steel plate 13 on the positioning section steel.

The steel pipe pile 11 adopts a spiral welded pipe, a crane with a vibration hammer is adopted for driving in construction, the flatness and the verticality are ensured, the deviation of the verticality is not greater than 1/250, the plane deviation is 50mm, the sinking speed of the steel pipe pile 11 is required to be controlled well, the sinking speed of the steel pipe pile is generally 1m/min, the distortion phenomenon is not allowed to occur in the construction process of the steel pipe pile 11, if a joint exists on a steel pipe, the bending resistance, the shearing resistance and the tensile strength of the joint are ensured, the joint is required to be located below an excavation surface by 3m, the joints of two adjacent steel pipe piles are required to be staggered by more than 1m, if an underground obstacle is encountered in the construction process of the steel pipe pile 11, the underground obstacle is removed in advance, then high-quality clay is used for compaction, and then the sinking construction of the steel pipe pile is carried out again.

The Larsen steel plate 13 is constructed by adopting small grooves and tongues to achieve a water stop effect, the steel pipe piles 11 and the Larsen steel plates 13 are alternatively sunk when the piles are sunk to ensure the overlapping quality of the grooves and the tongues of the steel pipe piles 11 and the Larsen steel plates 13, the pile sinking speed of the steel pipe piles 11 is uniformly controlled to be generally 1m/min, measures are adopted to ensure the verticality of the piles in the sinking process, the horizontal deviation is less than or equal to 10mm, and the elevation deviation is not more than 100 mm.

And (4) pit internal reinforcement: adopting a double-shaft cement mixing pile to reinforce the pit bottom, wherein the cement mixing amount is 18 percent, the empty mixing part is 6 percent, and the position of the reinforcement 4 in the pit is used for passive soil body reinforcement

The angle brace structure 2: and arranging a reinforced concrete support and a prestressed section steel combined support at the corner of the foundation pit, wherein the reinforced concrete support and the prestressed section steel combined support are connected with two adjacent side edges of the foundation pit.

The symmetrical structure 3 is a prestressed section steel combined support and is used for connecting two side edges in the width direction of the foundation pit.

The upright post structure is H-shaped steel, vertical arrangement is carried out according to actual needs, the horizontal deviation of the upright post structure is not larger than 50, the allowable deviation of the pile diameter is +/-50, the filling coefficient is not smaller than 1.10, the thickness of sediment at the bottom of a hole is not larger than 50, the upright post structure is uninterruptedly completed at one time, the time interval from the completion of hole forming to the concrete pouring is not larger than 24 hours, the upper part of the upright post structure adopts a lattice-type # -shaped steel framework, the batten plate and the angle steel are welded in a girth mode, and the height of an unindicated welding seam is not smaller than 8 mm.

The installation of the column structure follows the principle of firstly main components and then secondary components, and is preferably carried out according to the sequence of the purlin, the column, the support bracket, the joist, the triangular force transmission piece and the profile steel support, so that a closed stress system is formed as soon as possible and prestress is applied.

Step D: arranging drainage measures, namely arranging drainage ditches 9 and water collecting wells, and arranging pipe well gravity-flow dewatering wells 10 in the foundation pit;

step E: and carrying out earthwork excavation, dividing the pit foundation, wherein the earthwork excavation construction process sequentially comprises side slope excavation 6, slope protection and stirring treatment, capping beam and inner support construction, construction transportation channel construction, earthwork excavation subsection excavation to the bottom of the bedding layer, residual slope protection treatment, manual soil repair of a foundation pit and a groove and sporadic slope treatment.

The excavation of the earthwork to the bottom of the cushion layer in sections comprises a first earthwork excavation 7 and a second earthwork excavation 8, and the structural strength of the surrounding support system 1 needs to reach 80% before the first earthwork excavation 7.

The first earthwork excavation 7 comprises a first layer earthwork excavation and a second layer earthwork excavation, wherein the first layer earthwork: excavating to an absolute elevation of 2.00m by an absolute elevation of 3.50m, wherein the excavating depth is 1.50m, and the second layer of earthwork: and excavating at an absolute elevation of 2.00m to an absolute elevation of 0.500m, wherein the excavation depth is 1.5 m.

When the foundation pit side slope earthwork around excavates to the second floor, put the slope top around the foundation pit and set up steel pipe and add the interim fender that encloses of safety net formula to hang striking safety warning mark, after the bank protection construction is accomplished, adopt the brick to build 300X 400 escape canal along the foundation pit round at putting the slope top, interior plastering with 20 thick cement mortar, and the segmentation sets up the sump pit.

The second earthwork excavation 8 comprises a first layer earthwork excavation, a second layer earthwork excavation and a third layer earthwork excavation, wherein the first layer earthwork is: excavating the soil with the absolute elevation of 0.50m to the absolute elevation of-1.100 m, wherein the excavation depth is 1.60m, and the second layer of earthwork: excavating at an absolute elevation of-1.100 m to an absolute elevation of-1.500 m, wherein the excavation depth is 0.40m, and excavating at a third layer of earthwork: and excavating at an absolute elevation of-1.500 m to an absolute elevation of-2.60 m, wherein the excavation depth is 1.10 m.

The elevator shaft position adopts 1 60-type excavator to excavate at one time; the position of the bearing platform and the ground beam is excavated by a large excavator, the small excavator or the manual trimming is combined, and the scattered earthwork is cleaned: and (4) adopting a small excavator and manpower to pile up scattered earthwork, and lifting and conveying the scattered earthwork to the outside of the pit in a tower crane matching manner.

In the earthwork excavation process, a foundation pit is divided into a corresponding area A and a corresponding area B, excavation construction is carried out on the area A and the area B at the same time, a main excavated road 5 and a secondary excavated road 6 are respectively arranged in the area A and the area B according to the excavation direction and the excavated road arrangement, the secondary excavated road 6 is a branch road communicated with the main excavated road 5, the secondary excavated road 6 is transported to the main excavated road 5, the secondary excavated road 6 is excavated towards the central main excavated road 5, finally, the main excavated road 5 is excavated while retreating, roads are excavated, excavation is carried out in an inclined layered excavation mode, the slopes are stepped from low to high, and concrete spraying slope protection is adopted in slope protection treatment.

And F, pouring a cushion layer, a bottom plate and a force transmission belt, wherein the cushion layer at the bottom of the pit is poured to the slope toe of the foundation pit, and the force transmission belt is constructed at the same time when the concrete of the foundation bottom plate is poured and tamped, and the cushion layer is a concrete cushion layer or a wood mold.

The cushion layer is dug and tamped, the cushion layer is poured within 8 hours after the soil is dug to the designed elevation, the cushion layer is arranged to the edge of the fender post, and the maximum exposed area of the bottom of the cushion-free pit is not larger than 200 m.

And (3) positioning the earthwork excavation to the elevation of the first earthwork excavation 7, chiseling and trimming, performing cushion layer construction, reinforcing steel bar installation and template installation on the layer, performing concealed acceptance, pouring concrete and maintaining to reach the design strength of more than 80%, and performing second earthwork excavation 8.

Step G: and (4) dismantling the support, namely dismantling the corner brace structure 2, the symmetrical structure 3 and the in-pit reinforcement 4 in sequence.

The support is dismantled by using an internal support beam as a running channel of a gun platform machine, the dismantling is carried out by combining the gun platform machine with manual concrete chiseling, the dismantling is started from the corner support structure 2, then the symmetrical structure 3 is dismantled, and the dismantling is carried out from the corner of the foundation pit and gradually carried out towards the inside of the foundation pit; in order to prevent the support beam from suddenly collapsing to cause damage to the structure, the basement floor slab is formed by densely paving two layers of bamboo scaffold boards, dismantling and sectionally dismantling the two layers of bamboo scaffold boards, dividing the concrete support beam into 2-3 m concrete sections, hoisting and loading the concrete section by a tower crane, and transporting the concrete section out of a foundation pit.

Step I: backfilling earthwork, and backfilling and compacting the space between the outer wall and the surrounding support system 1 by using plain soil in time after the top plate of the basement is constructed; and backfilling earthwork or stacking sand bags at the bottom of the foundation pit, performing grouting operation at the bottom of the pit, and externally adding a staggered pipe in the pit and grouting for reinforcement.

Step J: the PC method is used for recovering the combined pile and adopts a vibration hammer pile pulling mode to carry out pile pulling operation.

And cutting off the supporting steel bars welded on the steel pipe pile 11, and after the supporting steel bars are trimmed and leveled (the base metal of the steel pipe pile cannot be damaged when the steel bars are cut off), returning sand or filling soil, and making the working surface for pulling out the steel pipe pile out, so that the steel pipe pile 11 can be pulled out.

The forced vibration generated by the vibration hammer disturbs the soil quality, destroys the cohesive force of the soil around the steel pipe pile 11 to overcome the pile pulling resistance, and pulls out the steel pipe pile 11 by the action of additional lifting force.

For the closed steel sheet pile wall, the pile pulling starting point is more than 5 piles away from the corner piles. The pile pulling starting point can be determined according to the conditions during pile sinking, and a jump pulling method can be used if necessary, and the pile pulling sequence is preferably opposite to that during pile driving.

When the pile is pulled out, the sheet pile locking opening can be vibrated by a vibration hammer to reduce the adhesion of soil, and then the pile is pulled out while vibrating. For the sheet pile which is difficult to be pulled out, the sheet pile can be firstly vibrated down by 100-300mm by a diesel hammer and then alternatively vibrated by the vibration hammer, in order to timely backfill the soil hole after the pile is pulled out, when the sheet pile is pulled to be slightly higher than the base bottom plate, the pulling is suspended, the sheet pile is vibrated for a few minutes by the perturbation hammer, and the soil hole is filled to the greatest extent.

The filling coefficient of the concrete to be grouted is more than 1.05, the grouting pressure is controlled to be about 0.3-0.5 MPa, and the required maintaining time is more than 3 min.

In the foundation ditch excavation and the basement work progress, to envelope and surrounding environment comprehensive monitoring, the information-based construction, monitoring content includes: observing horizontal displacement and settlement of the top of the enclosure wall; observing the lateral deformation of the deep layer of the enclosure wall and the lateral displacement of the deep soil body; observing the supporting axial force; observing horizontal displacement and settlement of the underground pipeline; observing horizontal position, settlement and crack of an adjacent building (structure); and (4) pit and external surface settlement and road crack observation.

The vehicle cleaning points are arranged at the positions of the inlet and the outlet, the water passing grooves are arranged at the positions of the vehicle cleaning points, the sedimentation tank is arranged beside the vehicle cleaning point flushing tank and is communicated with the drainage ditch 9, the sedimentation tank is used for on-site sedimentation and drainage, impurities in the sedimentation tank are precipitated and then discharged into a municipal pipe network, a water source in the sedimentation tank can be used when the vehicle is cleaned, and the water source and the water saving tank are used in a combined mode, so that the water is saved and the environment is protected.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention; thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Although the reference numerals in the figures are used more here: the method comprises the following steps of a peripheral supporting system 1, a corner support structure 2, a symmetrical structure 3, in-pit reinforcement 4, a main excavated road 5, a secondary excavated road 6, a first earthwork excavation 7, a second earthwork excavation 8, a drainage ditch 9, a pipe well artesian precipitation well 10, a steel pipe pile 11, a crown beam 12, a Larsen steel plate 13 and the like, but the possibility of using other terms is not excluded. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed as being without limitation to any additional limitations that may be imposed by the spirit of the present invention.

Claims

1. A construction method for foundation pit enclosure and earth excavation is characterized by comprising the following steps:

step A, designing a construction drawing and reviewing the drawing, designing the drawing of a region needing to be dug on site, and reviewing the designed drawing;

and B: preparing a construction site, leveling the site and the designed elevation, arranging the construction site and a site road, and arranging a site access, a vehicle cleaning point, site hardening, a site drainage point, a reinforcement cage processing platform and a reinforcement stock yard;

step C, arranging a support enclosure, combining the pile and the concrete section steel by adopting a PC construction method, and comprising a surrounding support system (1), a pit internal reinforcement (4), a corner support structure (2), a symmetrical structure (3) and a stand column structure;

step D: arranging drainage measures, arranging drainage ditches (9) and water collecting wells, and arranging a pipe well gravity-flow dewatering well (10) in the foundation pit;

step E: carrying out earthwork excavation, dividing a pit foundation, wherein the earthwork excavation construction process sequentially comprises side slope excavation (6), side slope protection and stirring treatment, capping beam and inner support construction, construction transportation channel construction, earthwork excavation subsection excavation to the bottom of a bedding layer, residual side slope protection treatment, manual soil repair of a foundation pit and a groove and sporadic side slope treatment;

step F, pouring a cushion layer, a bottom plate and a force transmission belt, pouring the cushion layer at the bottom of the pit to the slope toe of the foundation pit, and constructing the force transmission belt simultaneously when pouring and tamping concrete of the foundation bottom plate;

step G: dismantling the support, namely dismantling the corner brace structure (2), the symmetrical structure (3) and the in-pit reinforcement (4) in sequence;

step H: finishing the construction of the basement structure, taking the bottom plate in the step F as a basement bottom plate, and setting a basement outer wall and a basement top plate according to a drawing;

step I: backfilling earthwork, and backfilling and compacting between the outer wall and the surrounding support system (1) by using plain soil in time after the top plate of the basement is constructed; backfilling earthwork or stacking sand bags at the bottom of the foundation pit, performing grouting operation at the bottom of the pit, and externally adding a staggered pipe in the pit and grouting for reinforcement;

step J: recovering the combined pile in the PC method, and performing pile pulling operation in a vibration hammer pile pulling mode;

2. The construction method for foundation pit bracing and earthwork excavation according to claim 1, wherein a plank road is arranged at the entrance and exit in the step B, and the plank road is reinforced with foundation soil by prestressed concrete pipe piles.

3. The method of claim 2, wherein the step B comprises a slope-laying surface during the process of leveling the ground, and the construction of the slope-laying surface sequentially comprises positioning and line laying, slope outside excavation, slope trimming, steel bar anchoring, steel wire netting, spraying of the first concrete facing, steel bar mesh laying, spraying of the second concrete facing and maintenance.

4. The construction method for foundation pit bracing and earth excavation according to claim 1, wherein the PC construction method combined pile in the step C comprises steel pipe piles (11) and Larsen steel plates (13) connected between adjacent steel pipe piles (11), a top beam (12) is arranged at the top of each steel pipe pile (11), and a bottom die is arranged between each top beam (12) and each steel pipe pile (11).

5. The construction method for foundation pit bracing and earth excavation according to claim 1, wherein the excavation of the earth excavation section by section to the bottom of the bedding layer in the step E comprises a first excavation (7) and a second excavation (8), and the structural strength of the surrounding supporting system (1) is required to reach 80% before the first excavation (7).

6. The method of claim 5, wherein in the earth excavation process of the step E, the foundation pit is divided into a corresponding area A and a corresponding area B, and excavation is performed on the area A and the area B at the same time.

7. The method for constructing foundation pit enclosure and earthwork excavation according to claim 6, wherein a main excavated road (5) and a sub-excavated road (6) are respectively provided in the area A and the area B according to an excavation direction and an excavation road arrangement, the sub-excavated road (6) is a branch road communicated with the main excavated road (5), the sub-excavated road (6) is transported to the main excavated road (5), the sub-excavated road (6) is excavated back to the central main excavated road (5), and finally the main excavated road (5) is excavated while being retreated, and the roads are excavated and excavated in a form of oblique layered excavation from low to high in a step shape.

8. The method of claim 7, wherein the step E is performed by concrete spraying for slope protection.

9. The construction method for foundation pit bracing and earthwork excavation according to claim 1, wherein the cushion layer in the step F is a concrete cushion layer or a wood formwork.

10. The construction method of a foundation pit enclosure and earthwork excavation according to claim 1, wherein during the foundation pit excavation and basement construction, the enclosure and the surrounding environment are monitored comprehensively, and the construction is performed informationized, and the monitoring contents include: observing horizontal displacement and settlement of the top of the enclosure wall; observing the lateral deformation of the deep layer of the enclosure wall and the lateral displacement of the deep soil body; observing the supporting axial force; observing horizontal displacement and settlement of the underground pipeline; observing horizontal position, settlement and crack of an adjacent building (structure); and (4) pit and external surface settlement and road crack observation.