Test device and method for simulating the deformation of foundation pit and adjacent buildings under combined reinforcement

Abstract

The present invention discloses a test device for simulating the deformation of a foundation pit and an adjacent building under combined reinforcement, which includes a box body, a foundation pit simulation structure, a building simulation structure, a foundation pit reinforcement simulation system, a constant head simulation system, a precipitation and recharge simulation system, and a monitoring system. The box body is divided into a soil box and water tanks on both sides, and the water tanks are communicated with the soil box; the foundation pit simulation structure includes a diaphragm wall simulation structure buried relatively in the soil box and several internal support members; the building simulation structure is shallowly buried outside the foundation pit simulation structure; the reinforcement simulation system includes a foundation reinforcement part, a retaining wall reinforcement part, and an isolation pile structure; the constant head simulation system conveys water into the water tank through a first water pump, and a switching valve is arranged on the water tank wall to control the water level in the water tank; the precipitation and recharge simulation system injects water or pumps water into a drain pipe inserted in the foundation pit simulation structure through a second water pump; the monitoring system includes earth pressure cells, water pressure cells, strain gauges, displacement gauges, observation pipes, and liquid level gauges.

Description

Technical Field

[0001] The present invention relates to the technical field of building foundation engineering, and particularly relates to a test device and method for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement. Background Art

[0002] Coastal subway foundation pits are usually located in densely built-up areas of cities, and there are a large number of buildings in the surrounding adjacent areas. Some of the buildings are of long standing and have relatively poor structural stability. Therefore, during the construction of the foundation pit, the change of the foundation conditions is likely to cause disturbance to the building structure, bringing potential safety hazards to the buildings. Moreover, the construction area of the foundation pit is in a coastal environment, with a large water content in the soil layer and the soil type being mostly soft soil, which is very unfavorable for controlling the deformation of adjacent buildings.

[0003] The deformation control of foundation pit engineering is very strict. The horizontal displacement of the diaphragm wall, surface settlement, building settlement and inclination control are all the key points of foundation pit engineering deformation control. At present, researchers use a variety of foundation pit reinforcement methods to control the deformation of the foundation pit, including the widely used foundation reinforcement and diaphragm wall reinforcement, as well as the relatively less used isolation pile reinforcement. Most actual foundation pit projects use a certain method for reinforcement. This single reinforcement mode is not only difficult to achieve all-round reinforcement of the foundation pit, but also, if an ideal reinforcement effect is to be achieved, the cost investment is relatively high.

[0004] The combined reinforcement method organically combines the above three reinforcement methods to reinforce the engineering object more pertinently and comprehensively, so as to achieve a more ideal foundation pit deformation control effect. However, there is very little research on the deformation control of the combined reinforcement method at present, which makes the combined reinforcement construction of the foundation pit in actual projects lack sufficient theoretical support and mostly rely on construction experience to complete. Therefore, the present invention proposes a simulation test device and method to study the deformation of the foundation pit under the combined action of foundation reinforcement, retaining wall reinforcement and isolation pile reinforcement, so as to help establish a combined reinforcement method that can not only ensure the safety of foundation pit construction but also reduce the construction cost, and provide strong theoretical guidance for the on-site foundation pit reinforcement construction. Summary of the Invention

[0005] The main technical problem to be solved by the present invention is to provide a test device that can accurately simulate and feedback the stress and deformation conditions of the foundation pit and adjacent buildings under combined reinforcement during the processes of dewatering, recharging and excavation, and then provide strong theoretical guidance for the on-site foundation pit reinforcement construction.

[0006] To solve the above technical problems, the present invention provides a test device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement, including a box body, a foundation pit simulation structure, a building simulation structure, a foundation pit reinforcement simulation system, a constant head simulation system, a dewatering and recharging simulation system and a monitoring system;

[0007] The internal space of the box body is partitioned into a soil box and water tanks on both sides of the soil box; the soil box is filled with soil mass; the water tanks are communicated with the soil box through a number of water passing holes;

[0008] The foundation pit simulation structure includes diaphragm wall simulation structures and a number of internal bracing members; at least two diaphragm wall simulation structures are vertically embedded in the soil mass within the soil box and are arranged oppositely; when the soil mass between the diaphragm wall simulation structures is excavated during the test, the number of internal bracing members vertically support between the diaphragm wall simulation structures;

[0009] The building simulation structure is arranged outside the foundation pit simulation structure and includes a spatial frame constructed by connecting a number of bars and a bottom plate fixedly connected to the bottom of the spatial frame; the bottom plate is buried in the soil mass within the soil box;

[0010] The reinforcement simulation system includes a foundation reinforcement part, a retaining wall reinforcement part and a secant pile structure; the foundation reinforcement part is arranged inside the foundation pit simulation structure; the retaining wall reinforcement part and the diaphragm wall simulation structure are integrally formed along the thickness direction; the secant pile structure is vertically inserted at intervals in the soil mass between the foundation pit simulation structure and the building simulation structure along the extending direction of the diaphragm wall simulation structure;

[0011] The constant head simulation system includes a first water pump, a switching valve and a number of first water pipes; the first water pump transports water into the water tank through the first water pipe; the switching valve is arranged on the side wall of the water tank for controlling the water level in the water tank;

[0012] The dewatering and recharge simulation system includes a number of dewatering pipes, a second water pump and a number of second water pipes; the number of dewatering pipes are inserted at intervals in the soil mass inside the foundation pit simulation structure; a number of seepage holes are arranged at intervals on the pipe wall of the dewatering pipe; one end of the second water pipe is connected to the second water pump and the other end extends into the bottom of the dewatering pipe;

[0013] The monitoring system includes: earth pressure cells and water pressure cells for measuring the earth pressure and water pressure on both sides of the diaphragm wall simulation structure respectively; strain gauges for measuring the horizontal displacement of the diaphragm wall simulation structure; displacement gauges for measuring the surface settlement of the soil mass and the horizontal displacement and settlement of the building simulation structure; observation pipes with holes opened on the pipe wall and vertically inserted in the soil mass on both sides of the foundation pit simulation structure; liquid level gauges inserted in the dewatering pipes for measuring the water level in the soil mass.

[0014] In a preferred embodiment, the soil box and the water tanks are partitioned by a drawable partition board; the inner walls of the box body are oppositely provided with vertical fixing grooves for limit cooperation with the partition board in the horizontal direction; the water passing holes are arranged at intervals on the partition board.

[0015] In a preferred embodiment, the diaphragm wall simulation structure is arranged along the width direction of the box body.

[0016] In a preferred embodiment, the second water pump is provided with a mode knob and a rate knob; the mode knob is used to switch the working mode and control the second water pump to pump water or inject water into the downcomer, and the rate knob is used to control the power of the second water pump for pumping water or injecting water.

[0017] In a preferred embodiment, the base reinforcement part uses reinforced soil; the materials of the reinforced soil include sand and P.S.A 32 slag Portland cement.

[0018] In a preferred embodiment, the retaining wall reinforcement part uses P.S.A 32 slag Portland cement.

[0019] In a preferred embodiment, the earth pressure cells and water pressure cells are arranged at intervals along the depth direction on both sides of the diaphragm wall simulation structure; the earth pressure cells and water pressure cells located inside the diaphragm wall simulation structure are arranged below the base reinforcement part.

[0020] In a preferred embodiment, the arrangement positions of the strain gauges include: being arranged at intervals along the depth direction on the inner and outer sides of the diaphragm wall simulation structure; being arranged at intervals along the depth direction on the inner and outer sides of the isolation pile structure; being arranged at intervals along the height direction on the side of the building simulation structure close to the foundation pit simulation structure.

[0021] In a preferred embodiment, the arrangement positions of the displacement gauges include: the surface of the soil outside the foundation pit simulation structure, and being arranged at intervals along the vertical direction of the diaphragm wall simulation structure; being arranged at intervals along the height direction of the building simulation structure; the top of the building simulation structure, and at least one is arranged on each of the side close to the foundation pit simulation structure and the side far from the foundation pit simulation structure.

[0022] The present invention also provides a test method for simulating the deformation of a foundation pit and an adjacent building under combined reinforcement. Based on the test device for simulating the deformation of a foundation pit and an adjacent building under combined reinforcement described above, the method includes the following steps:

[0023] Step 1: Fill the soil box with test soil in layers by the sand-falling method; during the soil filling process, bury the foundation pit simulation structure with the retaining wall reinforcement part, earth pressure cells, water pressure cells, and strain gauges installed, as well as the isolation pile structure, downcomer, and observation pipe at the designated positions; when the soil height reaches the base position, lay the base reinforcement part in the foundation pit simulation structure, and then continue to fill the soil;

[0024] Step 2: After burying the soil mass to a height close to the top of the box body, open the switch valve on the side wall of the water tank, and then use the first water pump to add water into the water tank, so that the water slowly seeps into the soil box through the water passing holes; after the soil mass in the soil box is filled with water, let it stand for 24 hours; fill the soil mass in the area where settlement occurs after the standing ends.

[0025] Step 3: Bury the building structure equipped with displacement gauges in the soil mass, and install the displacement gauges on the surface of the soil mass.

[0026] Step 4: Turn on the second water pump, and pump water from the soil mass through the water discharge pipe to simulate the dewatering process of the foundation pit; when the water level drops to the first depth from the top of the soil mass, reduce the pumping rate of the second water pump to control the water level to remain unchanged, and let it stand for 12 hours; during the pumping and standing processes, through the monitoring system, measure the hydraulic, soil force information and deformation data around the foundation pit simulation structure and the building simulation structure.

[0027] Step 5: Excavate the soil mass inside the foundation pit simulation structure; the excavation should be carried out layer by layer from top to bottom, and it is necessary to let it stand for 2 hours for each excavated layer; during the excavation process, the diaphragm wall simulation structure should be laterally supported by the internal support members; when the excavation reaches the second depth from the top of the soil mass, stop the excavation and let it stand for 12 hours; the second depth is not lower than the first depth; similarly, during the excavation and standing processes, through the monitoring system, measure the hydraulic, soil force information and deformation data around the foundation pit simulation structure and the building simulation structure.

[0028] Step 6: Turn on the second water pump, and inject water into the soil mass through the water discharge pipe to simulate the recharging process of the foundation pit; when the water level rises to the top of the soil mass, turn off the second water pump; similarly, during the water injection process, through the monitoring system, measure the hydraulic, soil force information and deformation data around the foundation pit simulation structure and the building simulation structure.

[0029] In Steps 5 to 6, the first water pump and the switch valve are kept in the open state.

[0030] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0031] The test device provided by the present invention simulates the base reinforcement, retaining wall reinforcement and isolation pile reinforcement methods simply, is easy to operate, and has simulation accuracy relying on the data support of geotechnical tests. Based on this device, it is easy for researchers to control the single variable of a single reinforcement method and conduct a control test to explore the reinforcement effects of the above reinforcement methods alone or in combination, provide reliable theoretical support for on-site construction, and propose a reinforcement method that takes into account both construction safety and cost reduction and efficiency improvement.

[0032] The test method provided by the present invention simulates the deformation and settlement conditions of the foundation pit and adjacent buildings during the whole process of foundation pit dewatering, excavation and recharging in a single test. The working conditions are comprehensively simulated, close to the actual project, and have high scientificity and reference value.

[0033] The spacing and size relationship of each simulation structure of the test device provided by the present invention conform to the engineering reality. At the same time, the device adopts an intelligent peristaltic pump to simulate the constant water head and the seepage water pressure of dewatering and recharging of the engineering soil body by flexibly and accurately controlling the water injection mode and water injection power. Therefore, the device has high simulation accuracy.

[0034] The test device provided by the present invention is provided with nearly a hundred monitoring units. The monitoring points are closely arranged, and the setting positions are comprehensive and reasonable. The deformation and displacement of simulation structures such as foundation pits, buildings and soil bodies can be accurately captured, making the test data have high rigor and reliability.

[0035] (1) The method is simulated in a simple way, and the basic reinforcement parameters are determined by combining laboratory geotechnical tests. The reinforcement effects of each reinforcement method are clarified through tests, the advantages of each reinforcement method can be determined, and then the problem that the on-site foundation pit reinforcement overly relies on construction experience can be solved, and a combined reinforcement method that can ensure construction safety and reduce costs can be proposed;

[0036] (2) The foundation pit dewatering (recharging) construction is accurately simulated through model tests. The foundation pit dewatering and recharging are realized through an intelligent peristaltic pump, and the dewatering and recharging rates can be accurately controlled. The influence of dewatering and recharging on the deformation of the foundation pit itself and the deformation of the building can be systematically understood, providing a reference for the on-site foundation pit dewatering and recharging construction;

[0037] (3) Through the two-side water tanks and the large intelligent peristaltic pump, the constant water level boundary condition near the foundation pit is realized. The water level is ensured to be stable at the initial water level through the water faucets reserved on the water tanks, and the water level change situation is accurately reflected through the scale bars on the water tanks;

[0038] (4) The building model is made by connecting and combining wooden strips and wooden boards. The wooden boards can simulate the building foundation, and the wooden strips simulate the building structure. Loads can be applied on the wooden strips to simulate the deformation effects of the building under different weights. Moreover, displacement meters, dial indicators and other monitoring instruments are easily installed on the building model to ensure the accurate test of the displacement and settlement of the building structure, providing guidance for the on-site building protection;

[0039] (5) Factors such as foundation pit dewatering, foundation pit recharging, foundation pit excavation, and building load are comprehensively considered, and the water level, surface settlement, building settlement, horizontal displacement of the diaphragm wall, horizontal displacement of the building, water and soil pressure, etc. can be accurately monitored. The whole process of on-site foundation pit construction can be accurately simulated, providing guidance for foundation pit deformation control. Description of the Drawings

[0040] Figure 1 Schematic three-dimensional view of the test device described in the embodiments of the present invention;

[0041] Figure 2 Schematic view of the connection between the first angle steel and the front plate described in the embodiments of the present invention;

[0042] Figure 3 Elevation view of the foundation pit reinforcement simulation system described in the embodiments of the present invention;

[0043] Figure 4 Elevation view of the precipitation and recharge simulation system described in the embodiments of the present invention;

[0044] Figure 5 Plan layout of the monitoring system described in the embodiments of the present invention;

[0045] Figure 6 Elevation layout of the monitoring system described in the embodiments of the present invention.

[0046] The labels in the figure are: 1 - box body, 11 - front plate, 12 - steel plate, 13 - first angle steel, 14 - partition board, 15 - fixing groove, 16 - threaded fastener, 2 - foundation pit simulation structure (foundation pit structure), 21 - diaphragm wall simulation structure (diaphragm wall structure), 22 - internal support member, 3 - building simulation structure (building structure), 31 - wooden strip, 32 - wooden board, 4 - foundation pit reinforcement simulation system, 41 - base reinforcement part, 42 - retaining wall reinforcement part, 43 - isolation pile structure, 5 - constant head simulation system, 51 - large intelligent peristaltic pump, 52 - first water bucket, 53 - faucet, 54 - first water pipe, 6 - precipitation and recharge simulation system, 61 - precipitation pipe, 62 - small intelligent peristaltic pump, 63 - second water bucket, 64 - second water pipe, 71 - earth pressure cell, 72 - water pressure cell, 73 - strain gauge, 74 - displacement meter, 75 - observation pipe, 76 - liquid level gauge, 8 - soil box, 9 - water tank. Detailed implementation manners

[0047] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0048] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0049] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "installed / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0050] like Figures 1 to 6 As shown, an embodiment of the present invention provides a test device for simulating the deformation of a foundation pit and adjacent buildings under joint reinforcement, and a test method based on the device. The device includes a box 1, a foundation pit simulation structure 2, a building simulation structure, a foundation pit reinforcement simulation system 4, a constant head simulation system 5, a precipitation recharge simulation system 6 and a monitoring system. The following text, in conjunction with the diagram, describes in detail the specific structure of each of the above components, as well as their connection relationship or spatial position relationship. Since some components differ greatly from the simulated real objects in terms of size, material and other features, without affecting understanding, in order to avoid cumbersome sentences, this specification also briefly describes the foundation pit simulation structure 2 and the building simulation structure as "foundation pit structure 2" and "building structure 3" respectively.

[0051] like Figure 1 As shown, the box body 1 is in the shape of a cuboid, and the spatial dimensions are 4.1m long × 0.7m wide × 1.2m high. The box body 1 is sealed and enclosed by 5 plates, and the top is open. Except for the front plate 11 which is an acrylic plate with a length of 4.1m and a height of 1.2m, the other 4 plates are 5mm thick steel plates 12. The steel plates 12 are connected by welding. The front plate 11 is sealed to the adjacent steel plates 12 by a first angle steel 13 and a threaded fastener 16. One limb of the first angle steel 13 is sealed to the steel plate 12 by welding, bolting, etc. As shown Figure 2As shown, the other limb of the first angle steel 13 is closely attached to the front plate 11 and is hermetically connected by a number of groups of threaded fasteners 16 spaced in the length direction. It should be understood that the first angle steel 13 can also be integrally formed with the steel plate 12 or obtained by bending the edge of the steel plate 12. To further improve the sealing performance, sealant is applied at the joints of the above components. As shown in the figure, the internal space of the box body 1 is divided into three partitions in the length direction by two vertically arranged partitions 14. The partition in the middle is the soil box 8 with a length of 3.1 m, which contains soil to simulate the underground soil layer. The two partitions on both sides are water tanks 9 with a length of 0.5 m, which contain water at a certain height to simulate a constant water head. Further, a scale is provided on the side wall of the water tank 9 to facilitate observing the water level change in the water tank 9. The partition 14 is 10 mm thick and its height is not lower than that of the box body 1. A number of water holes are spaced in the plane of the partition 14 so that the water in the water tank 9 can seep into the soil box 8. The diameter of the water hole is 10 mm and the clear distance is 10 mm. To prevent the soil particles in the soil box 8 from entering the water tank 9, the partition 14 is covered with a filter screen. At the joints of the partition 14 with the rear steel plate 12 and the front plate 11, a fixing groove 15 with a width of 10 mm is provided. The two sides of the partition 14 are inserted into the fixing groove 15 to stably separate the water bodies and soil bodies on both sides. The fixing groove 15 is constructed by two relatively arranged second angle steels. Since the sealing performance requirement for the fixing groove 15 of this device is not high, the second angle steel and the steel plate 12, the front plate 11 can be connected by means of bolt connection, riveting or structural adhesive bonding. In particular, the second angle steel and the steel plate 12 can also be connected by welding.

[0052] As Figure 1 shown, the foundation pit simulation structure 2 is arranged in the soil box 8 and includes an underground diaphragm wall simulation structure 21 and an internal support member 22. For the sake of simplified description, the "diaphragm wall structure 21" mentioned below also refers to the diaphragm wall simulation structure 21. The two diaphragm wall structures 21 are arranged opposite to each other with a spacing of 40 cm. The diaphragm wall structure 21 adopts an acrylic plate with a width of 70 cm, a height of 50 cm and a thickness of 8 mm, which is vertically buried in the soil box 8 and its top is flush with the soil body. It can be easily seen from the component dimensions that in this embodiment, the diaphragm wall structure 21 extends along the width direction of the box body 1. The internal support member 22 adopts an organic glass tube with a length of 40 mm, a diameter of 10 mm and a wall thickness of 2 mm, which is vertically supported between the two diaphragm wall structures 21 to simulate the lateral support system after the foundation pit excavation.

[0053] As Figure 1As shown, the building simulation structure is obtained by cementing a number of wooden strips 31 and a wooden board 32. The number of wooden strips 31 are vertically connected to each other to form a space frame for simulating the beam-column system of a building. The wooden board 32 is fixedly connected to the bottom of the space frame and buried in the soil in the soil box 8 to simulate the foundation of the building. It should be understood that the rod strips are embodied as the wooden strips 31 in this embodiment, and the bottom plate is embodied as the wooden board 32. The building simulation structure is close to the foundation pit simulation structure 2, and the clear distance from the latter is 10 cm to accurately monitor the displacement and settlement of the building simulation structure 3 when the adjacent foundation pit is excavated or the water level changes.

[0054] As Figure 3 shown, the foundation pit reinforcement simulation system 4 simulates the existing combined reinforcement method in foundation pit engineering by reinforcing the foundation pit simulation structure 2 vertically, laterally, and in multiple directions of the adjacent soil, including the base reinforcement part 41, the retaining wall reinforcement part 42, and the isolation pile structure 43. The base reinforcement part 41 uses a kind of reinforced soil, which is obtained by mixing sand and P.S.A 32-grade slag Portland cement with water. When the foundation pit simulation structure 2 is installed and the filling continues, the reinforced soil is pre-buried in the inner side of the foundation pit simulation structure 2 according to a specified thickness of 10 cm, and a part is reserved for geotechnical tests to test its basic properties. The retaining wall reinforcement part 42 is integrally molded by combining the diaphragm wall structure 21 with a certain thickness of P.S.A 32-grade slag Portland cement and wrapped with a plastic film to simulate the reinforced diaphragm wall. The isolation pile structure 43 is simulated by organic glass tubes, which are inserted vertically and at intervals in the soil between the foundation pit simulation structure 2 and the building simulation structure along the extension direction of the diaphragm wall structure 21. The simulation methods of the above three reinforcement methods are simple, easy to operate, and rely on the data support of geotechnical tests, and the simulation accuracy is not lacking. Based on this simulation method, the device can conduct a control test by separately changing the simulation parameters of a certain reinforcement part such as size, material, etc., so as to explore the reinforcement effect of a certain reinforcement method and provide reliable theoretical support for on-site construction.

[0055] As Figure 1As shown, the constant head simulation system 5 works in cooperation with the water tanks 9 on both sides of the box body 1, and includes a large intelligent peristaltic pump 51, a first water bucket 52, a faucet 53 and several first water pipes 54. The large intelligent peristaltic pump 51 is connected to the first water bucket 52 through one of the first water pipes 54, and pumps water into the water tank 9 through another first water pipe 54. The water tank 9 is provided with a round hole at a height of 1.1 m to install the faucet 53. When the constant head simulation system 5 is working, the faucet 53 is in an open state all the time, so that the water level in the water tank 9 is always not higher than 1.1 m. Setting the upper water level limit is not only to prevent water from overflowing, but also to control the water pressure of the water seeping into the soil in the water tank 9. Preferably, a first water pipe 54 can be used to introduce the water flowing out of the faucet 53 into the first water bucket 52 to realize the recycling of water.

[0056] As Figure 1 , Figure 5 shown, the precipitation recharge simulation system 6 includes several drain pipes 61, a small intelligent peristaltic pump 62, a second water bucket 63 and a second water pipe 64. First of all, it should be understood that the so-called "precipitation" refers to the foundation pit dewatering project, which is to lower the water level in the foundation pit through open ditches or drain pipes 61, rather than atmospheric precipitation and rainwater infiltration. In this embodiment, 4 groups of the drain pipes 61 are symmetrically and spacedly inserted into the soil in the foundation pit simulation structure 2. The drain pipes 61 are simulated by PVC pipes with a diameter of 20 mm, a wall thickness of 4 mm and a length of 56 cm. Necessarily, a plurality of seepage holes are arranged at intervals on the PVC pipe, and the outside of the PVC pipe is wrapped with a filter screen. The small intelligent peristaltic pump 62 is externally connected with two second water pipes 64, one of which extends into the bottom of the drain pipe 61, and the other is connected to the second water bucket 63. The small intelligent peristaltic pump 62 is provided with a mode knob and a rate knob. The mode knob is used to switch the working mode and control the water pump to pump water or inject water into the drain pipe 61, and the rate knob is used to control the power during pumping or injecting water. When the small intelligent peristaltic pump 62 pumps water from the drain pipe 61 at a rate exceeding the constant head, it simulates the foundation pit dewatering process; when the small intelligent peristaltic pump 62 injects water into the drain pipe 61, it simulates the recharge process.

[0057] It should be understood that in this embodiment, the first water pump uses the large intelligent peristaltic pump 51, the second water pump uses the small intelligent peristaltic pump 62, the on-off valve uses the faucet 53, and the external water source is specifically embodied as the water contained in the first water bucket 52 or the second water bucket 63.

[0058] As Figure 5 , Figure 6As shown, the monitoring system is installed at multiple positions of the foundation pit simulation structure 2, the building simulation structure, and the soil mass to collect hydraulic and soil force information and deformation data of the foundation pit simulation structure 2 and the building simulation structure. The monitoring system includes soil pressure cells 71, water pressure cells 72, strain gauges 73, displacement gauges 74, observation pipes 75, and liquid level gauges 76. The soil pressure cells 71, water pressure cells 72, displacement gauges 74, and strain gauges 73 are all connected to a data acquisition and analysis system. There are a total of 12 soil pressure cells 71, which are used to measure the change of soil pressure at the foundation pit simulation structure 2. Their specific installation positions are as follows: they are arranged at intervals along the depth direction on the central axis of the diaphragm wall structure 21, and for each diaphragm wall structure 21, 4 soil pressure cells 71 are arranged along the full height on the outer side, and 2 soil pressure cells 71 are arranged below the reinforced soil on the inner side. The outer side refers to the side facing away from the internal support 22, and the inner side refers to the side facing the internal support 22. The same applies hereinafter. There are a total of 12 water pressure cells 72, which are used to measure the change of water pressure at the foundation pit simulation structure 2. Similar to the installation position of the soil pressure cells 71, the water pressure cells 72 are also arranged at intervals along the depth direction on the central axis of the diaphragm wall structure 21, and 2 and 4 water pressure cells 72 are respectively arranged on the inner and outer sides of each diaphragm wall structure 21. There are a total of 40 strain gauges 73, which are used to measure the horizontal displacement and strain of some simulation structures. Specifically, 16 strain gauges 73 are arranged at intervals along the depth direction on the central axis of the diaphragm wall structure 21, 8 on each of the inner and outer sides; 16 strain gauges 73 are arranged at intervals along the depth direction on the middlemost isolation pile structure 43, 8 on each of the inner and outer sides; 8 strain gauges 73 are arranged at intervals along the height direction on the middlemost wooden strip 31 on the side of the building simulation structure close to the foundation pit structure 2, 4 on each of the inner and outer sides. There are a total of 20 displacement gauges 74, which are used to measure the settlement of the soil surface, the horizontal displacement and settlement of the building simulation structure. Their specific installation positions are as follows: 7 are arranged on the soil surface on both sides of the foundation pit structure 2, and are arranged at intervals on the symmetry axis of the foundation pit structure 2 along the length direction of the box body 1; 4 are arranged at intervals in the height direction of the building simulation structure; 2 are arranged on the top of the building simulation structure, and are respectively located at the midpoints of the wooden strips 31 on the side close to the foundation pit structure 2 and the side far from the foundation pit structure 2. The material and structure of the observation pipe 75 are similar to those of the dewatering pipe 61. It uses a 60 cm long PVC pipe, and after opening holes in the pipe wall, it is wrapped with a filter screen. There are a total of 10 observation pipes 75, and their installation positions are similar to those of the displacement gauges 74 in the soil mass: they are vertically inserted into the soil on both sides of the foundation pit structure 2, and are arranged at intervals on the symmetry axis of the foundation pit structure 2 along the length direction of the box body 1 at an interval of 15 cm. The opening design of the observation pipe 75 makes the water level inside it flush with the water level of the soil mass.The liquid level gauge 76 is inserted into the downcomer 61. By intermittently measuring the water level in the downcomer 61, the change in the water level of the soil in the soil box 8 can be monitored. Considering all the above monitoring instruments, the monitoring data of the monitoring system includes: the horizontal displacement of the diaphragm wall structure 21 in the foundation pit structure 2, the earth pressure and water pressure borne on both sides; the horizontal displacement and settlement of the building simulation structure; the surface settlement and water level height of the soil in the soil box 8.

[0059] Based on the above device, an experimental method for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement is introduced. As Figure 1 shown, the method includes the following steps:

[0060] Step 1: Use the sand-falling method to fill the soil box 8 with test sand in layers, 10 cm for each layer. And each layer of sand needs to be consolidated and compacted in turn during the filling process. During the filling process, the foundation pit structure 2 that has been reinforced and installed with earth pressure cells 71, water pressure cells 72, and strain gauges 73, as well as the isolation pile structure 43, downcomer 61, and observation pipe 75 are buried in the positions described above. In particular, when the height of the sand reaches the base position, the reinforced soil needs to be laid in the foundation pit structure 2, and then the filling continues.

[0061] Step 2: After the soil is buried to a height of 1.1 m, open the faucet 53 on the side wall of the water tank 9, and then use the large intelligent peristaltic pump 51 to add water to the water tank 9, so that the water slowly seeps into the soil box 8 through the water passing holes on the partition 14 to saturate and consolidate the soil. After the soil in the soil box 8 is filled with water, let it stand for 24 hours. After standing, the soil may settle. Fill the settlement area with soil to keep the soil height at 1.1 m.

[0062] Step 3: Shallowly bury the building structure 3 installed with displacement gauges 74 in the soil according to the position relationship described above, and install the displacement gauges 74 on the surface of the soil.

[0063] Step 4: Turn on the pumping mode of the small intelligent peristaltic pump 62 and adjust the pumping rate to pump water from the soil through the 4 downcomers 61 to simulate the dewatering process of the foundation pit. When the water level drops to a position at the first depth from the top of the soil, reduce the pumping rate of the small intelligent peristaltic pump 62 to keep the water level unchanged. At this time, the dewatering simulation process is completed. In this embodiment, the first depth is 38 cm. Let the device stand for 12 hours to make the soil settlement reach a stable state. During the simulation of dewatering and standing, through the monitoring system, measure the hydraulic, soil force information and deformation data around the foundation pit structure 2 and the building structure 3.

[0064] Step 5: Excavate the soil within the foundation pit structure 2, i.e., the area between the two diaphragm wall structures 21. The excavation should be carried out from top to bottom, with a layer being excavated every 9 cm, and each excavated layer needs to be left static for 2 hours. During the excavation process, the inner support member 22 should be used to provide lateral support to the two diaphragm wall structures 21. Stop the excavation when reaching the second depth from the top of the soil, and leave it static for 12 hours. In this embodiment, the second depth is 36 cm. Similarly, during the simulated excavation and static process, through the monitoring system, the hydraulic, soil force information, and deformation data around the foundation pit structure 2 and the building structure 3 are measured.

[0065] Step 6: Turn on the water injection mode of the small intelligent peristaltic pump 62, and inject water into the soil through the 4 downcomers 61 to simulate the recharge process of the foundation pit. When the water level rises to the top of the soil, turn off the small intelligent peristaltic pump 62, and at this time the recharge simulation process is completed. Similarly, during the simulated recharge process, through the monitoring system, the hydraulic, soil force information, and deformation data around the foundation pit structure 2 and the building structure 3 are measured.

[0066] Thus far, the simulation test is completed. After the test, take out the soil from the box body 1, and at the same time take out and properly place the instruments such as the foundation pit structure 2, the building structure 3, the downcomer 61, and the monitoring components for the next test.

[0067] It should be noted that in Steps 5 to 6, the large intelligent peristaltic pump 51 and the faucet 53 are kept in the on state. During the test process, the earth pressure cell 71, the water pressure cell 72, the strain gauge 73, and the displacement gauge 74 are all automatically collected through the acquisition system, and the water level in the soil is manually measured every 5 minutes by the liquid level gauge 76.

[0068] The above is only a preferred specific embodiment of the present invention, and does not limit the patent scope of the present invention. Any technical equivalent transformation made using the content of the specification of the present invention shall fall within the protection scope of the present invention.

Claims

1. An experimental device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement, characterized in that: It includes a box body, a foundation pit simulation structure, a building simulation structure, a foundation pit reinforcement simulation system, a constant head simulation system, a precipitation and recharge simulation system, and a monitoring system; The internal space of the box body is divided into a soil box and water tanks on both sides of the soil box; the soil box is filled with soil; the water tanks are communicated with the soil box through a number of water passing holes; The foundation pit simulation structure includes a diaphragm wall simulation structure and a number of internal supports; at least two diaphragm wall simulation structures are vertically buried in the soil in the soil box and are arranged oppositely; when the soil between the diaphragm wall simulation structures is excavated during the test, the number of internal supports vertically support between the diaphragm wall simulation structures; The building simulation structure is arranged outside the foundation pit simulation structure, including a space frame constructed by connecting a number of bars, and a bottom plate fixedly connected to the bottom of the space frame; the bottom plate is buried in the soil in the soil box; The reinforcement simulation system includes a foundation reinforcement part, a retaining wall reinforcement part, and a cut-off pile structure; the foundation reinforcement part is arranged inside the foundation pit simulation structure; the retaining wall reinforcement part is integrally formed with the diaphragm wall simulation structure along the thickness direction; the cut-off pile structure is vertically inserted at intervals in the soil between the foundation pit simulation structure and the building simulation structure along the extension direction of the diaphragm wall simulation structure; The constant head simulation system includes a first water pump, a switch valve, and a number of first water pipes; the first water pump transports water into the water tank through the first water pipe; the switch valve is arranged on the side wall of the water tank for controlling the water level in the water tank; The precipitation and recharge simulation system includes a number of drain pipes, a second water pump, and a number of second water pipes; the number of drain pipes are vertically inserted at intervals in the soil inside the foundation pit simulation structure; a number of seepage holes are arranged at intervals on the pipe wall of the drain pipe; one end of the second water pipe is connected to the second water pump, and the other end extends into the bottom of the drain pipe; The monitoring system includes: earth pressure cells and water pressure cells, which are respectively used to measure the earth pressure and water pressure on both sides of the diaphragm wall simulation structure; strain gauges, which are used to measure the horizontal displacement and strain of each simulation structure; displacement gauges, which are used to measure the surface settlement of the soil and the horizontal displacement and settlement of the building simulation structure; observation pipes, with holes opened on the pipe wall, and vertically inserted in the soil on both sides of the foundation pit simulation structure; liquid level gauges, inserted in the drain pipes, for measuring the water level in the soil.

2. The test device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement according to claim 1, characterized in that: The soil box and the water tank are separated by a drawable partition; vertical fixing grooves are relatively arranged on the inner wall of the box body to be in limit fit with the partition along the horizontal direction; the water passing holes are arranged at intervals on the partition; 3. The test device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement according to claim 1, characterized in that: The diaphragm wall simulation structure is arranged along the width direction of the box body.

4. An experimental device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement according to claim 1, characterized in that: The second water pump is provided with a mode knob and a rate knob; the mode knob is used to switch the working mode to control the second water pump to pump water or inject water into the drain pipe, and the rate knob is used to control the pumping or injecting power of the second water pump.

5. An experimental device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement according to claim 1, characterized in that: The foundation reinforcement part uses reinforced soil; the materials of the reinforced soil include sand and P.S.A 32 grade slag Portland cement.

6. The test device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement according to claim 1, characterized in that: The retaining wall reinforcement part uses P.S.A 32 slag Portland cement.

7. An experimental device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement according to claim 1, characterized in that: The earth pressure cells and water pressure cells are arranged at intervals along the depth direction on both sides of the diaphragm wall simulation structure; the earth pressure cells and water pressure cells located inside the diaphragm wall simulation structure are arranged below the base reinforcement part.

8. An experimental device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement according to claim 1, characterized in that: The arrangement positions of the strain gauges include: being arranged at intervals along the depth direction on the inner and outer sides of the diaphragm wall simulation structure; being arranged at intervals along the depth direction on the inner and outer sides of the isolation pile structure; being arranged at intervals along the height direction on the side of the building simulation structure close to the foundation pit simulation structure.

9. An experimental device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement according to claim 1, characterized in that: The arrangement positions of the displacement gauges include: the soil surface outside the foundation pit simulation structure, and being arranged at intervals along the vertical direction of the diaphragm wall simulation structure; being arranged at intervals along the height direction of the building simulation structure; at the top of the building simulation structure, and at least one is arranged on each of the side close to the foundation pit simulation structure and the side far from the foundation pit simulation structure.

10. A test method for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement, based on the test device for simulating the deformation of a foundation pit and adjacent buildings under combined reinforcement according to any one of claims 1 to 9, characterized in that: It includes the following steps: Step 1: Use the sand-rain method to layer-fill the test soil into the soil box. During the soil filling process, bury the foundation pit simulation structure with the retaining wall reinforcement part and the earth pressure cells, water pressure cells, and strain gauges installed, as well as the isolation pile structure, the drain pipe, and the observation pipe at the designated positions; when the soil height reaches the base position, lay the base reinforcement part in the foundation pit simulation structure, and then continue to fill the soil. Step 2: After burying the soil to a height close to the top of the box body, open the on-off valve on the side wall of the water tank, and then use the first water pump to add water into the water tank to make the water slowly seep into the soil box through the water passing holes. After the soil in the soil box is filled with water, let it stand for 24 hours; fill the soil in the area where settlement occurs after the standing ends. Step 3: Bury the building structure with the displacement gauges installed in the soil, and install the displacement gauges on the soil surface. Step 4: Open the second water pump and pump water from the soil through the drain pipe to simulate the dewatering process of the foundation pit; when the water level drops to the first depth from the top of the soil, reduce the pumping rate of the second water pump to control the water level to remain unchanged, and let it stand for 12 hours; during the pumping and standing processes, measure the hydraulic, soil force information and deformation data around the foundation pit simulation structure and the building simulation structure through the monitoring system. Step 5: Excavate the soil inside the foundation pit simulation structure; the excavation should be carried out layer by layer from top to bottom, and each layer needs to be left standing for 2 hours; during the excavation process, use the internal support member to laterally support the diaphragm wall simulation structure; stop the excavation when it reaches the second depth from the top of the soil, and let it stand for 12 hours; the second depth is not lower than the first depth; similarly, during the excavation and standing processes, measure the hydraulic, soil force information and deformation data around the foundation pit simulation structure and the building simulation structure through the monitoring system. Step 6: Turn on the second water pump and inject water into the soil through the downcomer to simulate the recharge process of the foundation pit; when the water level rises to the top of the soil, turn off the second water pump; similarly, during the water injection process, measure the hydraulic, soil force information and deformation data around the foundation pit simulation structure and the building simulation structure through the monitoring system; In Steps 5 to 6, keep the first water pump and the switch valve in the open state.

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