A foundation pit supporting structure with secondary reinforcement function and a construction method thereof

Abstract

The application discloses a foundation pit supporting structure with secondary reinforcing function, which comprises piles, a crown beam located on the top of the piles, a waist beam located in the middle of the piles, a hollow partition plate, a connecting rod and a grouting pipe, the hollow partition plate is connected with the crown beam and the waist beam through the connecting rod, and the grouting pipe is arranged between the piles and the hollow partition plate; the connecting rod comprises a main rod body, an expansion component, a multistage ribbed rod body, a fetter and a pad, one end of the main rod body is connected with the multistage ribbed rod body, the other end of the main rod body is connected with the expansion component, the multistage ribbed rod body is fixed on the crown beam or the waist beam through the fetter and the pad, and the fetter can move away from the main rod body along the convex ribs of the multistage ribbed rod body after being opened. The application discloses a construction method of the foundation pit supporting structure. Under the action of the connecting rod, the supporting piles, the hollow partition plate and the middle soil body are connected into a whole, the soil body is grouted and reinforced considering the ground subsidence deformation caused by pre-dewatering, and the influence of the foundation pit excavation on the surrounding environment can be controlled.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of foundation pit supporting structure and its construction method, in particular to a foundation pit supporting structure with secondary reinforcement function and its construction method. BACKGROUND

[0002] In recent years, the development and utilization rate of underground space in large and medium-sized cities in China has been increasing, and a large number of foundation pit projects have emerged, and a large part of them are located in complex environment and densely built-up areas. The influence of foundation pit excavation on adjacent existing buildings cannot be underestimated, so the design of foundation pit engineering at this stage is also changing from strength control to deformation control. The influence of foundation pit excavation on the surrounding environment mainly comes from earth excavation and site dewatering, because the problem of optimizing the design scheme of foundation pit supporting structure to reduce the influence of foundation pit excavation on adjacent existing buildings needs to be solved urgently.

[0003] A foundation pit supporting structure and a foundation pit construction method are disclosed in Chinese patent No. CN201911096305.6. The top end of the support plate is horizontally penetrated by a slot, and the slot is inserted and fixed with a connecting rod wedged into the side wall of the foundation pit. The end of the connecting rod inserted into the side wall of the foundation pit is vertically penetrated and provided with a connecting port, and at the same time, the support pile vertically wedged into the side wall of the foundation pit from the ground penetrates through the connecting port and is commonly inserted with the connecting rod in the same vertical plane. The support pile anchors the connecting rod, thereby fixing the support plate tightly against the side wall of the foundation pit and supporting and protecting the side wall of the foundation pit. However, the problem is that on the one hand, each support pile works independently and cannot cooperatively bear external force, and on the other hand, the supporting structure cannot block the flow of underground water, and the influence of pit bottom uplift and ground subsidence caused by dewatering cannot be effectively controlled.

[0004] A foundation pit supporting structure and a foundation pit are disclosed in Chinese patent No. CN202110484803.9. The inclined pile is fixedly inserted into the bottom of the foundation pit, and the straight pile is fixedly inserted into the top of the slope of the foundation pit. The end of the straight pile protruding from the top of the slope of the foundation pit is fixedly connected with the cross beam on the inclined pile, thereby being fixed with the inclined pile 1 to achieve the effect of supporting and protecting the side wall of the foundation pit to prevent landslide. However, the problem is that on the one hand, the supporting structure needs to construct two concrete piles, which results in high economic cost, and on the other hand, for deep and large foundation pits, the arrangement of inclined piles may be limited by the site, and the deformation of the supporting structure in the middle and lower parts of the foundation pit cannot be inhibited.

[0005] In general, the existing foundation pit supporting structure can limit the deformation of the foundation pit to a certain extent, but cannot effectively limit the various deformation influences caused by site dewatering, or is not suitable for the positions commonly appearing in today's foundation pit engineering, and is not suitable for the scale of today's foundation pit. SUMMARY

[0006] The present application aims at providing a foundation pit supporting structure with secondary reinforcement function, which can effectively control the deformation of foundation pit, reduce the inclination and settlement of adjacent existing buildings and reduce the engineering risk.

[0007] The foundation pit supporting structure with secondary reinforcement function comprises pile rows, crown beams located at the top of the pile rows, waist beams located at the middle of the pile rows, hollow partitions, connecting rods and grouting pipes, the hollow partitions are connected with the crown beams and the waist beams through the connecting rods, and the grouting pipes are arranged between the pile rows and the hollow partitions.

[0008] Further, the hollow partition is provided with a filter screen towards the surface of the foundation pit, the hollow partition is provided with water filtering holes and fixing holes for fixing the expansion members, and a water pump and a water pumping pipe are arranged in the hollow partition, the water pump is used to pump the water in the hollow partition to the ground surface through the water pumping pipe. The water pump is located 0.5-1.0 m below the bottom of the foundation pit. The fixing holes are arranged in one-to-one correspondence with the positions of the connecting rods, so that the connecting rods can pass through and be fixed. The water filtering holes have a smaller diameter than the fixing holes and are much more than the fixing holes. Under the filtering effect of the filter screen, the water in the middle soil seeps into the hollow partition and is pumped out through the water pumping pipe by the water pump.

[0009] Further, the bottom of the hollow partition is in the shape of a tapered tip, so as to block the flow of underground water inside and outside the hollow partition.

[0010] Further, the connection between the main rod body and the hollow partition is arranged in a triangular shape on the plane, so as to be stable in structure.

[0011] Further, the main rod body is connected by a plurality of unit bodies with negative Poisson's ratio structure, and the cross-sectional form is a regular hexagon. When the soil on the side of the foundation pit is laterally unloaded and the stress of the soil is released, the additional stress generated can be absorbed to reduce the possible deformation. The unit with negative Poisson's ratio structure has good compression and tension performance and is not easily damaged when the soil has lateral displacement.

[0012] Further, the expansion member comprises a push-pull rod, an expansion plate, a sliding rail and a linkage rod, the push-pull rod is connected with the main rod body, the expansion plate is provided with the sliding rail for sliding of the linkage rod, and the expansion plate is slidably connected with two ends of the linkage rod respectively. The expansion member further comprises a pivot, the expansion plate is rotatably connected with the two ends of the linkage rod through the pivot, the expansion plate is rotatably connected with the push-pull rod through the pivot, and the expansion plates are hingedly connected with each other through the pivot.

[0013] Further, the shack comprises a shack plate, a special-shaped socket, a snap ring, a self-locking rod, a self-locking rail and a square socket, the square socket, the snap ring for clamping the convex ribs of the multi-stage ribbed rod body and the special-shaped socket matched with the self-locking rod are arranged on the shack plate, and the shack plate is fixed or opened after being inserted into each other through the self-locking rod and the special-shaped socket. The protruding part of the special-shaped socket is in the opposite direction of the protruding position of the self-locking rod in the working state, so that the shack is locked and is not easy to be disassembled without human intervention.

[0014] Further, the grouting pipe comprises a plastic inner pipe, a rigid outer pipe and an expansion boosting rod. The end of the plastic inner pipe is provided with a grouting port, and the outer pipe is provided with a grouting pipe extending outward and embeddedly connected with the plastic inner pipe. The plastic inner pipe is expanded under the action of the expansion boosting rod, so that the grouting pipe is pushed out of the opening of the rigid outer pipe, and the plastic inner pipe is plastically deformed. The bottom of the rigid outer pipe is tapered, and the pipe body is provided with n openings corresponding to the number and positions of the grouting pipes of the plastic inner pipe. The diameter of the expansion boosting rod is greater than the inner diameter of the plastic inner pipe and smaller than the inner diameter of the rigid outer pipe. The plastic inner pipe is plastically deformed under the action of the expansion boosting rod, and the grouting pipes are all extruded to the outside of the rigid outer pipe, thereby facilitating grouting.

[0015] Further, the number of layers of the connecting rods corresponds to the number of crown beams and waist beams, and the positions of the connecting rods also correspond to the crown beams and the waist beams. The connection between the connecting rod and the side of the pile row is realized through a pad, a shack and a multi-stage ribbed rod body, and the connection between the connecting rod and the hollow partition plate is realized through an expansion member. The maximum width of the expansion member in a non-working state is smaller than the diameter of the fixing hole reserved on the hollow partition plate. The expansion member can be expanded and clamped in the hollow partition plate under the action of pulling force through the rotation and outward pushing of the linkage rod, and the expanded expansion member is in a triangular shape, thereby realizing stable structure.

[0016] Further, when the deformation is large, the entire supporting structure can be secondarily reinforced through pulling out of the connecting rod and with the aid of the shack with simple operation, thereby realizing greater safety reserve of the supporting structure. In addition, after the foundation pit project is completed, the expansion member can be reset by disassembling the shack and pushing in the connecting rod, thereby realizing recycling of the supporting structure.

[0017] The construction method of the foundation pit supporting structure with secondary reinforcement function comprises the following steps:

[0018] Step one, positioning and opening holes on the hollow partition, fixing the filter screen towards the foundation pit surface, and welding each component of the connecting rod into one body;

[0019] Step two, construction of piles, corbel, hollow partition and grouting pipe;

[0020] Step three, construction of the first level connecting rod, through positioning drilling, arranging the connecting rod, when the expansion member at the end of the connecting rod enters the inside of the hollow partition, through exerting outward pulling force on the multi-level ribbed rod body at the slope surface, the expansion member is opened, the expansion plate is clamped on the inner wall of the hollow partition, and the clamp is operated, under the joint action of the multi-level ribbed rod body and the pad, the connection of the connecting rod with the supporting pile structure and the hollow partition is realized;

[0021] Step four, start pumping, and monitor the lateral displacement of the piles and the hollow partition and the settlement deformation of the upper part of the soil in both, when the settlement deformation exceeds 3mm or the lateral displacement reaches 3mm, stop pumping and use the grouting pipe to pressurize grouting, to reinforce the shallow soil;

[0022] Step five, when the grouting body is initially set, the foundation pit dewatering well and the hollow partition start pumping at the same time, and excavate layer by layer, after each excavation to the next excavation surface and over-excavation of 0.5m, construct the waist beam and the second, third, …, n level connecting rod, until the excavation to the pit bottom, at this time, the groundwater level drawdown is guaranteed to be 0.5m below the pit bottom;

[0023] Step six: when the displacement of the foundation pit monitoring increases, the clamp can be opened, the connecting rod is pulled out, the clamp fixes the next level rib, and the secondary reinforcement is realized;

[0024] Step seven: when the foundation pit project is completed, the clamp can be opened, the connecting rod is pushed into the foundation pit, and the expansion member is recycled.

[0025] Working principle: the lower part of the hollow partition is tapered, which should be ensured to be driven into the deep foundation rock during construction, so as to block the flow of underground water inside and outside the partition. In addition, the filter screen is arranged towards the foundation pit side of the partition, and the filter hole is arranged on the partition side towards the foundation pit, which is used to filter the water in the soil back into the hollow partition. Thirdly, the water pump and the pumping pipe connected with the water pump are arranged inside the hollow partition, the water pump is located 0.5m-1.0m below the excavation surface of the foundation pit, which can pump out the water back into the partition, realizing the purpose of pre-dewatering.

[0026] The pile row, the corbel and the waist beam are connected through a conventional mode, the connecting rod connects the pile row structure and the hollow partition plate structure, the connection between the connecting rod and the pile row structure is realized through a pad, a shackles and a multi-stage ribbed rod body, the pad can realize multi-angle operation of the connecting rod, the clamping ring arranged on the shackles can clamp the outer convex rib of the multi-stage ribbed rod body, further through the butt joint of the shackles, the self-locking rod is inserted according to the hole form, and then is rotated by 180 degrees along the self-locking rail in the counterclockwise direction, so that the connection between the connecting rod and the pile row structure is realized, and since the protruding part of the self-locking rod after connection faces downward, the self-rotation disengagement cannot be caused; the connection between the connecting rod and the hollow partition plate is realized through the opening of the expansion member, the outward pulling force is applied to the connecting rod, and then the linkage rod is rotated under the action of the push-pull rod, so that the expansion plate is opened, and the opened expansion member is in a triangular structure

[0027] The grouting pipe is mainly composed of a plastic inner pipe, a rigid outer pipe and an expansion boosting rod, the bottom of the rigid outer pipe is in a taper shape, the surface of the rigid outer pipe is provided with a plurality of openings, the plastic inner pipe is provided with a plurality of grouting pipes and one grouting port, the number, arrangement form and position of the grouting pipes are consistent with the openings on the surface of the rigid outer pipe, in a non-working state, the plastic inner pipe is attached to the surface of the rigid outer pipe, and then the expansion boosting rod is inserted into the plastic inner pipe to expand the plastic inner pipe, so that the grouting pipes are extruded to the outside of the rigid outer pipe, since the plastic inner pipe has been deformed plastically at this time, the grouting pipes are still on the outside after the expansion boosting rod is pulled out, and further, the soil body can be reinforced by grouting into the plastic inner pipe.

[0028] Since the hollow partition plate is arranged in the rock before the foundation pit is excavated, and pre-dewatering is carried out, further, in order to inhibit the lateral displacement of the hollow steel plate caused by the settlement of the middle soil body due to the pre-dewatering, the middle soil body is grouted through the grouting pipe, the strength of the middle soil body is increased, the strength of the new supporting system formed is greater, the stability is stronger, the influence on the adjacent existing building (structure) is smaller, the working face of the foundation pit excavation can be ensured to be not limited, and the construction is facilitated.

[0029] Secondary reinforcement + recovery:

[0030] When the lateral displacement of the enclosure structure is too large, the shackles can be opened by rotating the self-locking rod, the connecting rod can be pulled out, the shackles can be clamped on the outer convex rib of the lower stage of the multi-stage ribbed rod body, the secondary reinforcement can be realized, and the above operation can be operated multiple times according to the specific conditions. And since the unit and the cross section of the negative Poisson's ratio structure are designed in a hexagonal shape, the connecting rod has certain energy absorption efficiency and tensile performance, and is not easy to be damaged and failed in the whole supporting process. In addition, when the foundation pit engineering is completed, the shackles can be disassembled, the connecting rod can be pushed in, the expansion member can be reset, the connecting rod can be recovered, and the shackles can also be recovered.

[0031] Advantages: compared with the prior art, the present application has the following obvious characteristics:

[0032] 1、In the action of connecting rod, the supporting pile, hollow partition and the middle soil body are connected as a whole, and the influence of surface settlement deformation caused by pre-dewatering is considered, and the upper soil body is grouted and reinforced, so that the supporting structure form of the present application can achieve good effect in controlling the influence of foundation pit excavation on the surrounding environment, and is especially suitable for projects with strict deformation requirements;

[0033] 2、When the foundation pit is excavated, the soil bodies on both sides are laterally unloaded, and the stress is released, at this time the soil body unit shows that the vertical principal stress does not change, the horizontal principal stress decreases, and is in a vertical compression state, the main rod body cross section is a regular hexagonal structure, which can effectively achieve the function of small deformation energy absorption;

[0034] 3、With the continuous excavation of foundation pit engineering, the lateral displacement of the enclosure structure and the surface settlement will increase, the pit side moves towards the pit, the main rod body is a plurality of negative Poisson's ratio units, which has good tensile and compressive properties and is not easy to be damaged, and when the deformation of the foundation pit is large, the secondary reinforcement of the foundation pit supporting structure can be realized through the outer pull connecting rod, and the stability is further improved;

[0035] 4、The construction of the connecting rod of the foundation pit is simple and convenient, and the expansion of the component can be easily realized, that is, the recycling of the supporting structure can be easily realized, in addition, in the connection of the connecting rod and the corbel or the waist beam, the fixture can be easily realized to fix and disassemble the connecting rod, and due to the special structure of the insertion hole, the fixture will not open itself, and there is enough safety guarantee;

[0036] 5、Since no additional internal support and other forms of supporting structure that need to occupy the internal space of the foundation pit are needed, and the form of the present application is suitable for deep foundation pit, therefore, during the excavation stage of the foundation pit, the excavation surface is completely unrestricted, and has the construction advantage of deep foundation pit. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a sectional view of the present application;

[0038] Figure 2 is a sectional view of the present application during grouting;

[0039] Figure 3 is a plan view of the hollow partition 4 of the present application;

[0040] Figure 4 is a connection schematic diagram of the connecting rod 5 of the present application;

[0041] Figure 5 is a structure schematic diagram of the connecting rod 5 of the present application;

[0042] Figure 6 is a perspective view of the main rod body 51 of the present application;

[0043] Figure 7 is a first working state diagram of the expansion member 52 of the present application;

[0044] Figure 8 is a second working state diagram of the expansion member 52 of the present application;

[0045] Figure 9 is a structural diagram of the fetter 54 of the present application;

[0046] Figure 10 is a perspective view of the self-locking rod 534 of the present application;

[0047] Figure 11 is a sectional view of the special-shaped jack 532 of the present application;

[0048] Figure 12 is a sectional view of the grouting pipe 6 of the present application;

[0049] Figure 13 is a sectional view of the grouting pipe 6 of the present application; DETAILED DESCRIPTION

[0050] As Figures 1-2 , the foundation pit supporting structure with secondary reinforcement function comprises a row pile 1, a crown beam 2, a waist beam 3, a hollow partition plate 4, a connecting rod 5 and a grouting pipe 6. The crown beam 2 is arranged on the top of the row pile 1, and the waist beam 3 is arranged in the middle of the row pile 1. The hollow partition plate 4 is connected with the crown beam 2 and the waist beam 3 through the connecting rod 5, and the connecting rod 5 is arranged in parallel. The grouting pipe 6 is arranged between the row pile 1 and the hollow partition plate 4. When there is an existing building (structure) 7 around the foundation pit to be built, the supporting structure of the embodiment is used for foundation pit supporting, which can greatly reduce the influence of the foundation pit construction on the surrounding environment. The hollow partition plate 4 is arranged between the row pile 1 and the existing building (structure) 7, and needs to be punched into the deep rock layer of the foundation soil to cut off the flow of underground water inside and outside the hollow partition plate 4. In addition, a filter screen 41 is arranged on the side of the hollow partition plate 4 facing the foundation pit, which is used to filter out soil particles, so that the water in the soil is inversely infiltrated into the hollow partition plate 4. The water pump 45 and the water suction pipe 44 are arranged inside the hollow partition plate 4. Under the filtering action of the filter screen 41, the water in the middle soil seeps into the hollow partition plate 4, and then is discharged through the water pump 45 and the water suction pipe 44. The position of the water pump 45 is 0.5m-1.0m below the bottom of the foundation pit. The connecting rod 5 connects the row pile wall structure, the hollow partition plate 4 and the middle soil body into one, forming a stable foundation pit supporting structure. The connecting rod 5 is fixedly connected with the crown beam 2 and the waist beam 3 on the row pile 1 through the pad 55 and the fetter 54. The bottom of the hollow partition plate 4 is in the shape of a tapered tip.

[0051] As Figure 3The plate body of the hollow partition plate 4 towards the side of the foundation pit has multiple openings, including water filtering holes 42 and fixing holes 43. The underground water is filtered by the filter screen 41 and then seeps into the hollow partition plate 4 through the water filtering holes. The fixing holes 43 correspond to the connecting rods 5 one by one, so that the connecting rods 5 can pass through and be fixed. The diameter of the water filtering holes 42 is smaller than that of the fixing holes 43, and the number of the water filtering holes 42 is much more than that of the fixing holes 43.

[0052] As Figure 4 The connecting rod 5 is connected to the crown beam 2, the waist beam 3 and the hollow partition plate 4 in a triangular shape in the plane. One end of the connecting rod 5 is fixed to the crown beam 2 or the waist beam 3, and the other end is clamped and fixed in the hollow partition plate 4 by means of the expansion member 52.

[0053] As Figures 5-6 The connecting rod 5 mainly includes a main rod body 51, an expansion member 52 and a multi-stage ribbed rod body 53. The main rod body 51 is connected by multiple units with negative Poisson's ratio structure, and the cross-sectional shape is a regular hexagon. The bottom is welded to the expansion member 52, and the end is welded to the multi-stage ribbed rod body 53. The multi-stage ribbed rod body 53 is provided with multiple convex ribs on the surface.

[0054] As Figures 7-8 The expansion member 52 includes a push-pull rod 521, an expansion plate 522, a sliding rail 523, a linkage rod 524 and multiple pivots 525. In the non-working state, the maximum width of the expansion member 52 is smaller than the diameter of the fixing hole 43 reserved on the hollow partition plate 4, so as to facilitate installation and positioning. By applying a pulling force to the connecting rod 5, the push-pull rod 521 drives the linkage rod 524 to move under the action of the pivots 525. Since the sliding rail 523 in the form of a circular arc is embedded in the expansion plate 522, the movement of the linkage rod 524 can push away the expansion plate 522. At this time, the expansion member 52 is in the working state, and the expansion plate 522 is clamped on the inner wall of the hollow partition plate 4, realizing fixed connection. When the foundation pit construction is completed, a pushing force can be applied to the connecting rod 5 to push the linkage rod 524 forward, so that the expansion member 52 returns from the working state to the non-working state, thereby realizing the recycling of the structure. The expansion member 52 is made of rigid material, the thickness of the expansion plate 522 is more than 8 mm, and the depth of the sliding rail 523 is 0.4-0.6 times the thickness of the expansion plate 522.

[0055] As Figures 9-11The shackles 54 include shackles 541, special-shaped insertion holes 542, clamping rings 543, self-locking rods 544, self-locking rails 545, and square insertion holes 546. Two shackles 541 can be combined into one through the reserved square insertion holes 546. The outer convex ribs on the multi-stage ribbed rod body 53 are clamped on the clamping rings 543. The self-locking rods 544 are inserted into the special-shaped insertion holes 542. After the self-locking rods 544 are rotated counterclockwise by 180° with the help of the self-locking rails 545 reserved at the bottom of the special-shaped insertion holes 542, the shackles 541 are locked. Because of the corresponding relationship between the direction of the outer protruding part of the self-locking rod 544 and the direction of the protruding part of the special-shaped insertion hole 542, when the shackles 541 are locked, the direction of the outer protruding part of the self-locking rod 544 is downward, and the self-locking rod 544 cannot be pulled out directly. Because the direction is downward, it is completely opposite to the direction of the protruding part of the special-shaped insertion hole 542, so the shackles 54 cannot be separated automatically without human operation. The operation is simple, and the structure is safe and reliable. When secondary reinforcement is needed, the self-locking rod 544 is rotated and pulled out, and the outer pulling rod 5 is pulled out, so that the next outer convex rib on the multi-stage ribbed rod body 543 is clamped on the clamping ring 543 of the shackles 54. The shackles 54 are assembled again to realize secondary reinforcement, and the supporting structure has more reserved space in safety.

[0056] As Figures 12-13 The diameter of the grouting pipe 6 is 12 mm, which includes a plastic inner pipe 61, a rigid outer pipe 62, and an expansion boosting rod 63. The bottom of the rigid outer pipe 62 is tapered, which can facilitate insertion into the soil. A plurality of openings are arranged on the wall of the rigid outer pipe 62. The plastic inner pipe 61 is attached to the inner wall of the rigid outer pipe 62. The plastic inner pipe 61 includes one grouting port 612 and a plurality of slurry outlets 611 which are the same as the number of the rigid outer pipe 62 and have opposite positions and arrangements. The diameter of the expansion boosting rod 63 should be larger than the inner diameter of the plastic inner pipe 61 and smaller than the inner diameter of the rigid outer pipe 62. When the expansion boosting rod 63 is pushed into the plastic inner pipe 61, the plastic inner pipe 61 will deform plastically due to the difference in diameter. After the expansion boosting rod 63 is pulled out, only a small part of the elastic deformation of the plastic inner pipe 61 will recover, but the slurry outlets 611 will still be in the pushed-out state. At this time, by pressing the grouting port 612, the slurry can flow into the soil through the slurry outlets 611, achieving the reinforcement of the surrounding soil. The rigid outer pipe 62 is preferably made of steel or other materials with high rigidity, which facilitates the insertion of the grouting pipe into the soil. The material of the plastic inner pipe 61 is preferably rubber or other plastic materials, which can still work normally without damage even after a large deformation. The diameter of the plastic inner pipe 61 in the non-pushed-out state is 8-10 mm, which ensures that the slurry outlets of the plastic inner pipe 61 can be located outside the rigid outer pipe 62.

[0057] The construction method of the above-mentioned foundation pit supporting structure considering pre-dewatering and capable of secondary reinforcement and recovery includes the following steps:

[0058] Step one, positioning hole is made on the hollow partition 4, and the filter screen 41 is fixed, and the main rod body 51, the multi-stage ribbed rod body 53 and the expansion member 52 of the connecting rod 5 are welded into one body;

[0059] Step two, construction of pile row 1, crown beam 2, hollow partition 4 and grouting pipe 6;

[0060] Step three, construction of the first stage connecting rod 5, through positioning drilling, the connecting rod 5 is arranged, when the expansion member 52 at the end of the connecting rod 5 enters the inside of the hollow partition 4, through applying outward pulling force to the multi-stage ribbed rod body 53 at the slope, the expansion member 52 is opened, so that the expansion plate 522 is clamped on the inner wall of the hollow partition 4, at the same time, the clamp 54 is operated, under the joint action of the multi-stage ribbed rod body 53 and the pad 55, the connecting rod 5 is connected with the supporting pile structure and the hollow partition 4, and the planar arrangement form is triangular;

[0061] Step four, arrangement of the water pump 45 and the water pumping pipe 44 and start of water pumping, at the same time, the lateral displacement of the pile row 1 and the hollow partition 4 and the settlement deformation of the soil in the upper part of the two are mainly monitored, when the settlement deformation exceeds 3mm or the lateral displacement reaches 3mm, the water pumping is stopped, the plastic inner tube 61 is deformed by means of the expansion boosting rod 63, the grouting pipe 611 is pushed out, after the expansion boosting rod 63 is pulled out, pressure grouting is carried out to the grouting port 612, the grouting pipe 611 is used to flow into the soil, so as to realize the reinforcement of the shallow soil;

[0062] Step five, when the grouting body is initial set, the water pump 45 in the foundation pit dewatering well and the hollow partition 4 starts water pumping at the same time, and the waist beam 3 and the second stage, the third stage, …, the n stage connecting rod 5 are constructed after each excavation to the next excavation surface and over-excavation of 0.5m, until the excavation to the pit bottom, at this time, the groundwater level is ensured to be 0.5m below the pit bottom;

[0063] Step six: during the construction of the foundation pit engineering, when the displacement of the foundation pit monitoring is large, the clamp 54 is opened, the connecting rod 5 is pulled out, the clamp 54 is fixed to the next stage rib, and the secondary reinforcement is realized;

[0064] Step seven: after the completion of the foundation pit engineering, the clamp 54 is opened, the connecting rod 5 is pushed into the pit, the expansion member 52 is recycled, so as to achieve the effect of recycling the supporting member.

Claims

1. A foundation pit support structure with secondary reinforcement function, characterized in that: The utility model relates to a kind of row piles (1), crown beam (2) located at the top of row piles (1), waist beam (3) located in the middle of row piles (1), hollow partition (4), connecting rod (5) and grouting pipe (6), the hollow partition (4) is connected with crown beam (2), waist beam (3) respectively by connecting rod (5), the grouting pipe (6) is arranged between row piles (1) and hollow partition (4);The connecting rod (5) includes main rod body (51), expansion component (52), multistage ribbed rod body (53), fetters (54) and backing plate (55), one end of the main rod body (51) is connected with multistage ribbed rod body (53), the other end is connected with expansion component (52), the multistage ribbed rod body (53) is fixed on crown beam (2) or waist beam (3) by fetters (54), backing plate (55), the fetters (54) can be moved in the direction away from main rod body (51) along the convex rib of multistage ribbed rod body (53) step by step after being opened; The hollow partition (4) is provided with a filter screen (41) facing the foundation pit surface, the hollow partition (4) is provided with a water filtering hole (42) and a fixing hole (43), and the hollow partition (4) is further provided with a water pumping pipe (44) and a water pump (45), wherein the water pump (45) is used to pump water in the hollow partition (4) to the ground surface through the water pumping pipe (44); The bottom of the hollow partition (4) is in the shape of a tapered tip. The main rod body (51) is connected by a plurality of unit bodies with negative Poisson's ratio structure. Water pumping is simultaneously used to monitor the lateral displacement of the row piles (1) and the hollow partition (4) and the settlement deformation of the soil in the upper part of the row piles (1) and the hollow partition (4), and when the settlement deformation exceeds 3 mm or the lateral displacement reaches 3 mm, water pumping is stopped, pressure grouting is performed by means of the grouting pipe (6), and the shallow soil is reinforced.

2. The foundation pit support structure with secondary reinforcement function according to claim 1, characterized in that: The connection between the main rod body (51) and the hollow partition (4) is arranged in a triangular shape on a plane.

3. The foundation pit support structure with secondary reinforcement function according to claim 1, characterized in that: The expansion component (52) includes a push-pull rod (521), an expansion plate (522), a sliding rail (523) and a linkage rod (524), the push-pull rod (521) is connected with the main rod body (51), the expansion plate (522) is provided with the sliding rail (523) for sliding of the linkage rod (524), and the expansion plate (522) is slidingly connected with both ends of the linkage rod (524) respectively.

4. The foundation pit support structure with secondary reinforcement function according to claim 3, characterized in that: The expansion component (52) further includes a rotating shaft (525), the expansion plate (522) is rotatably connected with both ends of the linkage rod (524) through the rotating shaft (525), the expansion plate (522) is rotatably connected with the push-pull rod (521) through the rotating shaft (525), and the expansion plate (522) is hingedly connected with each other through the rotating shaft (525).

5. The foundation pit support structure with secondary reinforcement function according to claim 1, characterized in that: The shackles (54) include a shackling plate (541), a special-shaped socket (542), a clamping ring (543), a self-locking rod (544), a self-locking rail (545) and a square socket (546), the square socket (546) is arranged on the shackling plate (541), the clamping ring (543) is arranged for clamping the convex ribs of the multi-stage ribbed rod body (53), the special-shaped socket (542) is matched with the self-locking rod (544), and the shackling plate (541) is inserted into each other and then fixed or opened through the self-locking rod (544) and the special-shaped socket (542).

6. The foundation pit support structure with secondary reinforcement function according to claim 1, characterized in that: The grouting pipe (6) comprises a plastic inner pipe (61), a rigid outer pipe (62) and an expansion boosting rod (63); the end of the plastic inner pipe (61) is provided with a grouting opening (612), and a grouting pipe (611) of the rigid outer pipe (62) is arranged in a surrounding manner and protrudes and is connected with the plastic inner pipe (61); under the action of the expansion boosting rod (63), the grouting pipe (611) is pushed out from the opening of the rigid outer pipe (62), and the plastic inner pipe (61) is plastically deformed.

7. The construction method of the foundation pit support structure with secondary reinforcement function according to any one of claims 1-6, characterized in that, The method comprises the following steps: Step one, positioning and opening holes are performed on the hollow partition plate (4), a filter screen (41) facing a foundation pit surface is fixed, and components of the connecting rod (5) are welded into one body; Step two, construction of the pile (1), the corbel (2), the hollow partition plate (4) and the grouting pipe (6) is performed; Step three, the first-stage connecting rod (5) is constructed, the connecting rod (5) is arranged through positioning and drilling, when the expansion member (52) at the end of the connecting rod (5) enters the hollow partition plate (4), an outward pulling force is applied to the multi-stage ribbed rod body (53) at the slope surface, the expansion member (52) is opened, the expansion plate (522) is clamped on the inner wall of the hollow partition plate (4), and the shackles (54) are operated, the connecting rod (5) is connected with the supporting pile structure and the hollow partition plate (4) under the joint action of the multi-stage ribbed rod body (53) and the backing plate (55); Step four, water is pumped out, the lateral displacement of the pile (1) and the hollow partition plate (4) and the settlement deformation of the upper part of the soil in the pile (1) and the hollow partition plate (4) are monitored, when the settlement deformation exceeds 3mm or the lateral displacement reaches 3mm, the pumping is stopped, and the shallow soil is reinforced through pressure grouting of the grouting pipe (6); Step five, when the grouting body is initially cured, the foundation pit dewatering well and the hollow partition plate (4) start pumping water at the same time, and the excavation is performed layer by layer, after each excavation to the next excavation surface and over-excavation of 0.5m, the corbel (3) and the second-stage, third-stage, …, n-stage connecting rod (5) are constructed, until the excavation reaches the pit bottom, and the underground water level is ensured to be 0.5m below the pit bottom; Step six, when the monitoring displacement of the foundation pit becomes large, the shackles (54) are opened, the connecting rod (5) is pulled out, the shackles (54) fix the next-stage rib, and secondary reinforcement is realized; Step seven, when the foundation pit project is completed, the shackles (54) are opened, the connecting rod (5) is pushed into the foundation pit, and the expansion member (52) is recycled.

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