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

Abstract

The invention discloses a test device for simulating deformation of a foundation pit and an adjacent building under combined reinforcement. The test device comprises a box body, a foundation pit simulation structure, a building simulation structure, a foundation pit reinforcement simulation system, a constant head simulation system, a rainfall recharge simulation system and a monitoring system. The box body is divided into a soil box and water tanks on the two sides, and the water tanks communicate with the soil box. The foundation pit simulation structure comprises an underground diaphragm wall simulation structure which is relatively buried in the soil box and a plurality of inner supporting pieces; the building simulation structure is shallowly buried on the outer side of the foundation pit simulation structure; the reinforcing simulation system comprises a base reinforcing part, a retaining wall reinforcing part and an isolation pile structure; the constant head simulation system conveys water into a water tank through a first water pump, and a switch valve is arranged on the wall of the water tank to control the water level in the water tank; the precipitation recharge simulation system injects or pumps water into or out of a precipitation pipe inserted in the foundation pit simulation structure through a second water pump; the monitoring system comprises a soil pressure box, a water pressure box, a strain gauge, a displacement meter, an observation pipe and a liquid level meter.

Description

Technical Field

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

[0002] Coastal subway foundation pits are usually located in densely built areas of cities, with a large number of buildings in the surrounding areas. Some of the buildings are very old and have relatively poor structural stability. Therefore, during the foundation pit construction process, changes in foundation conditions are likely to disturb the building structure and bring safety hazards to the building. In addition, the foundation pit construction area is located in a coastal environment, the soil layer has a high water content and the soil type is mostly soft soil, which is very unfavorable for the deformation control of adjacent buildings.

[0003] The deformation control of foundation pit engineering is very strict. The horizontal displacement of ground-anchored walls, surface settlement, building settlement and tilt control are all the key points of deformation control of foundation pit engineering. At present, researchers use a variety of foundation pit reinforcement methods to control foundation pit deformation, including the widely used base reinforcement and trench wall reinforcement, and 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 you want to achieve the ideal reinforcement effect, the cost investment is relatively high.

[0004] The combined reinforcement method organically combines the above three reinforcement methods to reinforce the engineering object in a more targeted and comprehensive manner, so as to achieve a more ideal foundation pit deformation control effect. However, there is currently very little research on deformation control of the combined reinforcement method, which means that in actual projects, the combined reinforcement construction of foundation pits lacks sufficient theoretical support and is mostly completed by relying on construction experience. Therefore, the present invention proposes a simulation test device and method to study the deformation of the foundation pit under the combined action of base reinforcement, wall reinforcement, and isolation pile reinforcement, so as to help establish a combined reinforcement method that can both ensure the safety of foundation pit construction and reduce construction costs, and provide strong theoretical guidance for 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 precipitation, recharge and excavation conditions under combined reinforcement, thereby providing strong theoretical guidance for on-site foundation pit reinforcement construction.

[0006] In order 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 joint reinforcement, including a box, a foundation pit simulation structure, a building simulation structure, a foundation pit reinforcement simulation system, a constant water head simulation system, a precipitation recharge simulation system and a monitoring system;

[0007] 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 tank and the soil box are connected through a plurality of water holes;

[0008] The foundation pit simulation structure includes a ground-connected wall simulation structure and a plurality of inner support members; at least two ground-connected wall simulation structures are vertically buried in the soil in the soil box and arranged opposite to each other; when the soil between the ground-connected wall simulation structures is excavated during the test, the plurality of inner support members are vertically supported between the ground-connected wall simulation structures;

[0009] The building simulation structure is arranged outside the foundation pit simulation structure, and includes a space frame formed by connecting a plurality of rods, and a bottom plate fixed to the bottom of the space frame; the bottom plate is buried in the soil in the soil box;

[0010] The reinforcement simulation system comprises a base reinforcement part, a retaining wall reinforcement part and an isolation pile structure; the base reinforcement part is arranged inside the foundation pit simulation structure; the retaining wall reinforcement part and the ground-connected wall simulation structure are integrally formed along the thickness direction; the isolation pile structure is inserted into the soil between the foundation pit simulation structure and the building simulation structure at intervals and vertically along the extension direction of the ground-connected wall simulation structure;

[0011] The constant water head simulation system comprises a first water pump, a switch valve and a plurality of first water pipes; the first water pump delivers water into the water tank through the first water pipes; the switch valve is arranged on the side wall of the water tank and is used to control the water level in the water tank;

[0012] The precipitation recharge simulation system comprises a plurality of precipitation pipes, a second water pump and a plurality of second water pipes; the plurality of precipitation pipes are inserted into the soil inside the foundation pit simulation structure at intervals; the precipitation pipes are provided with a plurality of seepage holes at intervals on the pipe wall; one end of the second water pipe is connected to the second water pump, and the other end extends into the bottom of the precipitation pipe;

[0013] The monitoring system includes: an earth pressure box and a water pressure box, which are respectively used to measure the earth pressure and water pressure on both sides of the ground-connected simulated wall structure; a strain gauge, which is used to measure the horizontal displacement of the ground-connected simulated wall structure; a displacement meter, which is used to measure the surface settlement of the soil and the horizontal displacement and settlement of the building simulation structure; an observation pipe, which has a hole in the pipe wall and is vertically inserted in the soil on both sides of the foundation pit structure; and a liquid level meter, which is inserted in the downcomer pipe and is used to measure the water level in the soil.

[0014] In a preferred embodiment, the soil box and the water tank are separated by a removable partition; the inner wall of the box body is relatively provided with vertical fixing grooves to limit the position with the partition in the horizontal direction; the water holes are arranged at intervals on the partition.

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

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

[0017] In a preferred embodiment, the base reinforcement portion is made of reinforced soil; the material of the reinforced soil includes sand and PSA32 grade slag silicate cement.

[0018] In a preferred embodiment, the wall reinforcement part adopts PSA32 grade slag silicate cement.

[0019] In a preferred embodiment, the earth pressure box and the water pressure box are arranged at intervals on both sides of the ground-connected wall simulation structure along the depth direction; the earth pressure box and the water pressure box located on the inner side of the ground-connected wall simulation structure are arranged below the base reinforcement part.

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

[0021] In a preferred embodiment, the displacement meter arrangement positions include: the soil surface outside the foundation pit simulation structure, and arranged at intervals along the vertical direction of the ground-anchored wall simulation structure; 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 side close to the foundation pit simulation structure and on the side away from the foundation pit simulation structure.

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

[0023] Step 1: Use the falling sand method to fill the test soil into the soil box in layers; during the filling process, the foundation pit simulation structure with the wall reinforcement part, the earth pressure box, the water pressure box, the strain gauge, the isolation pile structure, the downpipe, and the observation pipe are buried at the designated position; when the soil height reaches the base position, the base reinforcement part needs to be laid in the foundation pit simulation structure, and then the filling continues;

[0024] Step 2: After the soil is buried to a height close to the top of the box, the switch valve on the side wall of the water tank is opened, and then water is added to the water tank using the first water pump, so that the water slowly seeps into the soil box from the water hole; after the soil in the soil box is filled with water, it is left to stand for 24 hours; and the area where settlement occurs after the standing is completed is filled with soil;

[0025] Step 3: bury the building structure with the displacement meter installed in the soil, and install the displacement meter on the surface of the soil.

[0026] Step 4: Turn on the second water pump and pump water from the soil through the downcomer to simulate the precipitation 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 process, measure the hydraulic, geomechanical information and deformation data around the foundation pit simulation structure and the building simulation structure through the monitoring system;

[0027] Step 5: excavate the soil inside the foundation pit simulation structure; the excavation should be carried out in layers from top to bottom, and each excavated layer should be left to stand for 2 hours; during the excavation process, the inner support member should be used to laterally support the ground-connected wall simulation structure; when the excavation reaches the second depth from the top of the soil, stop the excavation and leave it to stand for 12 hours; the second depth is not lower than the first depth; similarly, during the excavation and standing process, the hydraulic, geotechnical information and deformation data around the foundation pit simulation structure and the building simulation structure are measured by the monitoring system;

[0028] Step 6: Turn on the second water pump and inject water into the soil through the downcomer to simulate the recharging 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, geomechanical information and deformation data around the foundation pit simulation structure and the building simulation structure through the monitoring system;

[0029] In step 5 to step 7, the first water pump and the switch valve are kept in an 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 is simple and easy to operate in simulating base reinforcement, wall reinforcement and isolation pile reinforcement, and has simulation accuracy based on the data support of geotechnical tests. Based on this device, researchers can easily control a single variable of a single reinforcement method and conduct control tests 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 construction safety and reduces costs and increases efficiency.

[0032] The test method provided by the present invention simulates the deformation and settlement of the foundation pit and adjacent buildings during the entire process of foundation pit dewatering, excavation and recharging in a single test. The working condition simulation is comprehensive, close to the real project, and has 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 actual engineering practice. At the same time, the device adopts an intelligent peristaltic pump to simulate the constant water head of the engineering soil and the seepage water pressure of precipitation and recharge by flexibly and accurately controlling the water injection mode and water injection power. Therefore, the device has a high simulation accuracy.

[0034] The test device provided by the present invention is provided with nearly one hundred monitoring units, the monitoring points are closely arranged, and the setting positions are comprehensive and reasonable, which can accurately capture the deformation and displacement of simulated structures such as foundation pits, buildings, and soil, so that the test data has high rigor and reliability.

[0035] (1) The method uses a simple method to simulate and determine the basic reinforcement parameters in combination with laboratory geotechnical tests. The reinforcement effect of each reinforcement method is clarified through the test method, and the advantages of each reinforcement method can be determined, thereby solving the problem that on-site foundation pit reinforcement relies too much on construction experience, and proposing a combined reinforcement method that ensures construction safety and reduces costs;

[0036] (2) Accurately simulate the foundation pit dewatering (recharge) construction through model tests, realize foundation pit dewatering and recharge through intelligent peristaltic pumps, and accurately control the dewatering and recharge rates. Systematically understand the impact of dewatering and recharge on the deformation of the foundation pit itself and the deformation of the building, and provide a reference for on-site foundation pit dewatering and recharge construction;

[0037] (3) The water tanks on both sides and the large intelligent peristaltic pump are used to achieve the constant water level boundary condition near the foundation pit. The faucets reserved on the water tanks are used to ensure that the water level is stable at the initial water level, and the scale bars on the water tanks accurately reflect the water level changes.

[0038] (4) By connecting and combining wooden strips and planks, a building model is made. The planks can simulate the building foundation, and the wooden strips can simulate the building structure. Loads can be applied to the wooden strips to simulate the deformation effect of the building under different weights. The building model is easy to install monitoring instruments such as displacement meters and dial indicators to ensure accurate testing of building structure displacement and settlement, providing guidance for on-site building protection;

[0039] (5) Comprehensively consider factors such as foundation pit dewatering, foundation pit recharging, foundation pit excavation, and building load, and can accurately monitor water level, surface settlement, building settlement, horizontal displacement of ground-anchored walls, horizontal displacement of buildings, water, and soil pressure, etc. It can accurately simulate the entire process of on-site foundation pit construction and provide guidance for foundation pit deformation control. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a three-dimensional schematic diagram of the test device described in an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the first angle steel being connected to the front plate in an embodiment of the present invention;

[0042] Figure 3 is a schematic elevation diagram of a foundation pit reinforcement simulation system according to an embodiment of the present invention;

[0043] Figure 4 It is a schematic elevation diagram of the precipitation recharge simulation system described in an embodiment of the present invention;

[0044] Figure 5 is a plan view of the monitoring system described in an embodiment of the present invention;

[0045] Figure 6 It is a elevational layout diagram of the monitoring system described in an embodiment of the present invention.

[0046] The markings in the figure are: 1-box, 11-front plate, 12-steel plate, 13-first angle steel, 14-partition plate, 15-fixing groove, 16-threaded fastener, 2-foundation pit simulation structure (foundation pit structure), 21-ground-connected wall simulation structure (ground-connected wall structure), 22-inner support, 3-building simulation structure (building structure), 31-wooden strips, 32-wooden boards, 4-foundation pit reinforcement simulation system, 41-base reinforcement part, 42-wall reinforcement part , 43-isolation pile structure, 5-constant water 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-soil pressure box, 72-water pressure box, 73-strain gauge, 74-displacement meter, 75-observation tube, 76-liquid level meter, 8-soil box, 9-water tank. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection 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 Figure 1 to Figure 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 tightly fitted with the front plate 11, and is sealed and connected by several groups of threaded fasteners 16 arranged at intervals 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 steel plate 12 at the edge. In order to further improve the sealing performance, sealant is applied to the connection 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 located in the middle is a soil box 8 with a length of 3.1m, which is filled with soil to simulate the underground soil layer. The two partitions located on both sides are water tanks 9 with a length of 0.5m, which are filled with water of a certain height to simulate the constant head. Furthermore, a scale is provided on the side wall of the water tank 9 to facilitate the observation of the water level change in the water tank 9. The partition 14 is 10mm thick and the height is not lower than the box body 1. The partition 14 is provided with a plurality of water holes at intervals in the plate surface so that the water in the water tank 9 can penetrate into the soil box 8. The diameter of the water hole is 10 mm and the net distance is 10 mm. In order to prevent the soil particles in the soil box 8 from entering the water tank 9, the partition 14 is covered with a filter. At the junction of the partition 14, 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 block the water and soil on both sides. The fixing groove 15 is constructed by two second angle steels arranged opposite to each other. Since the device does not have high requirements on the sealing of the fixing groove 15, the second angle steel can be connected to the steel plate 12 and the front plate 11 by bolt connection, riveting or structural adhesive bonding. In particular, the second angle steel can also be connected to the steel plate 12 by welding.

[0052] like Figure 1 As shown, the foundation pit simulation structure 2 is arranged in the soil box 8, including an underground ground-connected wall simulation structure 21 and an internal support member 22. To simplify the description, the "ground-connected wall structure 21" described below also refers to the ground-connected wall simulation structure 21. The two ground-connected wall structures 21 are arranged opposite to each other with an interval of 40 cm. The ground-connected 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. It is not difficult to see from the size of the components that in this embodiment, the ground-connected wall structure 21 extends along the width direction of the box body 1. The internal support member 22 adopts a plexiglass 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 ground-connected wall structures 21 to simulate the lateral support system after the foundation pit is excavated.

[0053] like Figure 1As shown, the building simulation structure is obtained by gluing a plurality of wooden strips 31 and a wooden board 32. The plurality of wooden strips 31 are connected vertically to each other to form a space frame for simulating the beam-column system of the building. The wooden board 32 is fixed 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 rods are the wooden strips 31 in this embodiment, and the bottom plate is the wooden board 32. The building simulation structure is close to the foundation pit simulation structure 2, with a net distance of 10 cm from the latter, so as 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] like Figure 3 As 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 and laterally, as well as the adjacent soil in multiple directions, including a base reinforcement part 41, a wall reinforcement part 42 and an isolation pile structure 43. The base reinforcement part 41 uses a reinforced soil, which is obtained by mixing sand and PSA32 grade slag silicate cement with water. When the foundation pit simulation structure 2 is installed and the soil is continued to be filled, the reinforced soil is pre-buried into the inner side of the foundation pit simulation structure 2 according to a specified thickness of 10 cm, and a part is retained for geotechnical testing to test its basic properties. The wall reinforcement part 42 is formed by integrally molding the ground-connected wall structure 21 with a certain thickness of PSA32 grade slag silicate cement, and wrapping it with a plastic film to simulate the reinforced ground-connected wall. The isolation pile structure 43 is simulated by a plexiglass tube, and is inserted into the soil between the foundation pit simulation structure 2 and the building simulation structure at intervals and vertically along the extension direction of the ground-connected wall structure 21. The simulation methods of the above three reinforcement methods are simple and easy to operate, and rely on the data support of geotechnical tests, and are not lacking in simulation accuracy. Based on this simulation method, the device can conduct control tests by 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] like Figure 1As shown, the constant water head simulation system 5 cooperates with the water tanks 9 on both sides of the box body 1 to work, including a large intelligent peristaltic pump 51, a first water bucket 52, a faucet 53 and a plurality of 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 circular hole at a height of 1.1m to install the faucet 53. When the constant water head simulation system 5 is working, the faucet 53 is in a normally open state, so that the water level in the water tank 9 is always not higher than 1.1m. The upper limit of the water level is set not only to prevent water from overflowing, but also to control the water pressure of the water in the water tank 9 penetrating into the soil. 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 achieve water recycling.

[0056] like Figure 1 , Figure 5 As shown, the precipitation recharge simulation system 6 includes a number of precipitation 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 precipitation project, which is to lower the water level in the foundation pit through an open ditch or a precipitation pipe 61, rather than atmospheric precipitation and rainwater infiltration. In this embodiment, the four groups of precipitation pipes 61 are symmetrically and spaced apart in the soil in the foundation pit simulation structure 2. The precipitation pipe 61 is simulated using a PVC pipe 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 a filter screen is wrapped around the outside of the PVC pipe. The small intelligent peristaltic pump 62 is externally connected to two second water pipes 64, one of which extends into the bottom of the precipitation 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 pump to pump or inject water into the downcomer 61. The rate knob is used to control the power during pumping or injecting water. When the small intelligent peristaltic pump 62 pumps water into the downcomer 61 at a rate exceeding the normal head, the foundation pit dewatering process is simulated; when the small intelligent peristaltic pump 62 injects water into the downcomer 61, the recharging process is simulated.

[0057] It should be understood that, in this embodiment, the first water pump adopts the large intelligent peristaltic pump 51, the second water pump adopts the small intelligent peristaltic pump 62, the switch valve adopts the faucet 53, and the external water source is respectively materialized as the water contained in the first water bucket 52 or the second water bucket 63.

[0058] like Figure 5 , Figure 6As shown, the monitoring system is installed at multiple locations of the foundation pit simulation structure 2, the building simulation structure and the soil body to collect hydraulic and geomechanical information and deformation data of the foundation pit simulation structure 2 and the building simulation structure. The monitoring system includes an earth pressure box 71, a water pressure box 72, a strain gauge 73, a displacement meter 74, an observation tube 75 and a liquid level gauge 76. The earth pressure box 71, the water pressure box 72, the displacement meter 74 and the strain gauge 73 are all connected to a data acquisition and analysis system. There are a total of 12 earth pressure boxes 71, which are used to measure the soil pressure changes at the foundation pit simulation structure 2. The specific installation position is: arranged at intervals along the depth direction on the central axis of the ground-connected wall structure 21, and for each ground-connected wall structure 21, 4 earth pressure boxes 71 are arranged along the full height on the outside, and 2 earth pressure boxes 71 are arranged on the inside under the reinforced soil. The outside refers to the side facing away from the inner support 22, and the inside refers to the side facing the inner support 22, the same below. There are 12 water pressure boxes 72 in total, which are used to measure the water pressure changes at the foundation pit simulation structure 2. Similar to the installation position of the soil pressure box 71, the water pressure boxes 72 are also arranged at intervals along the depth direction on the central axis of the ground-connected wall structure 21, and 2 and 4 are respectively set on the inner side and outer side of each ground-connected wall structure 21. There are 40 strain gauges 73 in total, which are used to measure the horizontal displacement and strain of part of the simulation structure. Specifically, 16 strain gauges 73 are arranged at intervals along the depth direction on the central axis of the ground-connected wall structure 21, 8 on the inner side and 8 on the outer side; 16 strain gauges 73 are arranged at intervals along the depth direction on the middle isolation pile structure 43, 8 on the inner side and 8 on the outer side; 8 strain gauges 73 are arranged at intervals along the height direction on the middle wooden strip 31 on the side of the building simulation structure close to the foundation pit structure 2, 4 on the inner side and 4 on the outer side. There are 20 displacement meters 74 in total, which are used to measure the surface settlement of the soil, the horizontal displacement and settlement of the building simulation structure. The specific installation positions are: 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 close to the foundation pit structure 2 and away from the foundation pit structure 2. The material and structure of the observation pipe 75 are similar to those of the downpipe 61. It adopts a 60cm long PVC pipe, and is also wrapped with a filter after opening a hole in the pipe wall. There are 10 observation pipes 75 in total, and the installation position is similar to the installation position of the displacement meter 74 in the soil: vertically inserted into the soil on both sides of the foundation pit structure 2, and arranged at intervals of 15cm on the symmetry axis of the foundation pit structure 2 along the length direction of the box body 1. The opening design of the observation pipe 75 makes the water level inside it flush with the water level of the soil.The liquid level meter 76 is inserted in the downcomer 61, and the water level change of the soil in the soil box 8 can be monitored by intermittently measuring the water level in the downcomer 61. Combining the above monitoring instruments, the monitoring data of the monitoring system include: the horizontal displacement of the ground-connected wall structure 21 in the foundation pit structure 2, the soil pressure and water pressure on both sides; the horizontal displacement and settlement of the building simulation structure; the surface settlement of the heavy soil in the soil box 8 and the water level.

[0059] Based on the device, a test method for simulating the deformation of the foundation pit and adjacent buildings under joint reinforcement is introduced. Figure 1 As shown, the method comprises the following steps:

[0060] Step 1: Use the falling sand method to fill the test sand into the soil box 8 in layers, with each layer of 10 cm, and each layer of sand needs to be consolidated and compacted in sequence. During the filling process, the foundation pit structure 2 that has been reinforced and installed with the soil pressure box 71, water pressure box 72, and strain gauge 73, as well as the isolation pile structure 43, downpipe 61, and observation pipe 75 are buried in the position 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 is continued.

[0061] Step 2: After the soil is buried to a height of 1.1m, open the tap 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 penetrates into the soil box 8 from the water 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 the standing still, the soil may settle, and the settled area is filled with soil to keep the soil height at 1.1m.

[0062] Step 3: According to the positional relationship described above, the building structure 3 with the displacement meter 74 installed is shallowly buried in the soil, and the displacement meter 74 is installed 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, and pump water from the soil through the four downpipes 61 to simulate the precipitation 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 small intelligent peristaltic pump 62 to control the water level to remain unchanged, and the precipitation simulation process is completed. In this embodiment, the first depth is 38 cm. Let the device stand for 12 hours to allow the soil settlement to reach a stable state. During the simulated precipitation and standing process, the hydraulic, geotechnical information and deformation data around the foundation pit structure 2 and the building structure 3 are measured through the monitoring system.

[0064] Step 5: Excavate the soil in the foundation pit structure 2, that is, the area between the two ground-connected wall structures 21. The excavation should be carried out from top to bottom, with one layer excavated every 9 cm, and each layer should be left to stand for 2 hours. During the excavation process, the internal support members 22 should be used to provide lateral support to the two ground-connected wall structures 21. Stop excavation when the excavation reaches the second depth from the top of the soil, and leave it to stand for 12 hours. In this embodiment, the second depth is 36 cm. Similarly, during the simulated excavation and standing process, the hydraulic, geotechnical information and deformation data around the foundation pit structure 2 and the building structure 3 are measured through the monitoring system.

[0065] Step 6: Turn on the water injection mode of the small intelligent peristaltic pump 62, and inject water into the soil through the four downcomers 61 to simulate the recharging 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 the recharging simulation process is completed. Similarly, during the process of simulating recharging, the monitoring system is used to measure the hydraulic, geomechanical information and deformation data around the foundation pit structure 2 and the building structure 3.

[0066] After the test, the soil is taken out of the box 1, and the foundation pit structure 2, building structure 3, downpipe 61, monitoring components and other instruments are taken out and properly placed for the next test.

[0067] It should be noted that in steps 5 to 7, the large intelligent peristaltic pump 51 and the faucet 53 are kept in an open state. During the test, the soil pressure box 71, the water pressure box 72, the strain gauge 73, and the displacement meter 74 are all automatically collected by the collection system, and the water level in the soil is manually measured every 5 minutes by the liquid level meter 76.

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

Claims

1. A test device for simulating the deformation of a combined reinforced foundation pit and adjacent buildings, characterized in that: Including box, foundation pit simulation structure, building simulation structure, foundation pit reinforcement simulation system, constant water head simulation system, precipitation recharge simulation system and 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 tank and the soil box are connected through a plurality of water holes; The foundation pit simulation structure includes a ground-connected wall simulation structure and a plurality of inner support members; at least two ground-connected wall simulation structures are vertically buried in the soil in the soil box and arranged opposite to each other; when the soil between the ground-connected wall simulation structures is excavated during the test, the plurality of inner support members are vertically supported between the ground-connected wall simulation structures; The building simulation structure is arranged outside the foundation pit simulation structure, and includes a space frame formed by connecting a plurality of rods, and a bottom plate fixed to the bottom of the space frame; the bottom plate is buried in the soil in the soil box; The reinforcement simulation system comprises a base reinforcement part, a retaining wall reinforcement part and an isolation pile structure; the base reinforcement part is arranged inside the foundation pit simulation structure; the retaining wall reinforcement part and the ground-connected wall simulation structure are integrally formed along the thickness direction; the isolation pile structure is inserted into the soil between the foundation pit simulation structure and the building simulation structure at intervals and vertically along the extension direction of the ground-connected wall simulation structure; The constant water head simulation system comprises a first water pump, a switch valve and a plurality of first water pipes; the first water pump delivers water into the water tank through the first water pipes; the switch valve is arranged on the side wall of the water tank and is used to control the water level in the water tank; The precipitation recharge simulation system comprises a plurality of precipitation pipes, a second water pump and a plurality of second water pipes; the plurality of precipitation pipes are inserted into the soil inside the foundation pit simulation structure at intervals; the precipitation pipes are provided with a plurality of seepage holes at intervals on the pipe wall; one end of the second water pipe is connected to the second water pump, and the other end extends into the bottom of the precipitation pipe; The monitoring system includes: an earth pressure box and a water pressure box, which are respectively used to measure the earth pressure and water pressure on both sides of the ground-connected simulated wall structure; a strain gauge, which is used to measure the horizontal displacement and strain of each simulated structure; a displacement meter, which is used to measure the surface settlement of the soil and the horizontal displacement and settlement of the building simulation structure; an observation pipe, which has a hole in the pipe wall and is vertically inserted in the soil on both sides of the foundation pit structure; and a liquid level meter, which is inserted in the downcomer pipe and is used to measure the water level in the soil.

2. A test device for simulating deformation of a combined reinforced foundation pit and adjacent buildings according to claim 1, characterized in that: The soil box and the water tank are separated by a removable partition; vertical fixing grooves are relatively arranged on the inner wall of the box body to limit the position of the partition along the horizontal direction; and the water holes are arranged at intervals on the partition.

3. The test device for simulating the deformation of a combined reinforced foundation pit and adjacent buildings according to claim 1, characterized in that: The ground-connected wall simulation structure is arranged along the width direction of the box body.

4. The test device for simulating deformation of a combined reinforced foundation pit and adjacent buildings according to claim 1, characterized in that: The second water pump is provided with a mode knob and a speed knob; the mode knob is used to switch the working mode and control the second water pump to pump or inject water into the downcomer, and the speed knob is used to control the power of the second water pump to pump or inject water.

5. The test device for simulating deformation of a combined reinforced foundation pit and adjacent buildings according to claim 1, characterized in that: The base reinforcement part adopts reinforced soil; the materials of the reinforced soil include sand and PSA32 grade slag silicate cement.

6. The test device for simulating deformation of a combined reinforced foundation pit and adjacent buildings according to claim 1, characterized in that: The wall reinforcement part adopts PSA32 grade slag silicate cement.

7. The test device for simulating deformation of a combined reinforced foundation pit and adjacent buildings according to claim 1, characterized in that: The soil pressure boxes and water pressure boxes are arranged at intervals on both sides of the ground-connected wall simulation structure along the depth direction; the soil pressure boxes and water pressure boxes located on the inner side of the ground-connected wall simulation structure are arranged below the base reinforcement part.

8. The test device for simulating deformation of a combined reinforced foundation pit and adjacent buildings according to claim 1, characterized in that: The strain gauge arrangement positions include: arranged at intervals along the depth direction on the inner and outer sides of the ground-connected wall simulation structure; arranged at intervals along the depth direction on the inner and outer sides of the isolation pile structure; and arranged at intervals along the height direction on one side of the building simulation structure close to the foundation pit simulation structure.

9. The test device for simulating deformation of a combined reinforced foundation pit and adjacent buildings according to claim 1, characterized in that: The displacement meter arrangement positions include: the soil surface outside the foundation pit simulation structure, and arranged at intervals along the vertical direction of the ground-anchored wall simulation structure; 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 side close to the foundation pit simulation structure and on the side away from the foundation pit simulation structure.

10. A test method for simulating deformation of a foundation pit and adjacent buildings under joint reinforcement, based on a test device for simulating deformation of a foundation pit and adjacent buildings under joint reinforcement as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: Use the falling sand method to fill the test soil into the soil box in layers; During the filling process, the foundation pit simulation structure with the wall reinforcement part, earth pressure box, water pressure box, strain gauge, isolation pile structure, downpipe and observation pipe installed is buried at the designated position; when the soil reaches the base position, the base reinforcement part needs to be laid in the foundation pit simulation structure, and then the filling continues; Step 2: After the soil is buried to a height close to the top of the box, the switch valve on the side wall of the water tank is opened, and then water is added to the water tank using the first water pump, so that the water slowly seeps into the soil box from the water hole; After the soil in the soil box is filled with water, let it stand for 24 hours; fill the area where settlement occurs after the standing time. Step 3: burying the building structure with the displacement meter installed in the soil, and installing the displacement meter on the surface of the soil; Step 4: Turn on the second water pump and pump water from the soil through the downcomer to simulate the precipitation 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 process, measure the hydraulic, geomechanical 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 in layers from top to bottom, and each excavated layer should be left to stand for 2 hours; during the excavation process, the inner support member should be used to laterally support the ground-connected wall simulation structure; when the excavation reaches the second depth from the top of the soil, stop the excavation and leave it to stand for 12 hours; the second depth is not lower than the first depth; similarly, during the excavation and standing process, the hydraulic, geotechnical information and deformation data around the foundation pit simulation structure and the building simulation structure are measured by the monitoring system; Step 6: Turn on the second water pump and inject water into the soil through the downcomer to simulate the recharging 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, geomechanical information and deformation data around the foundation pit simulation structure and the building simulation structure through the monitoring system; In step 5 to step 7, the first water pump and the switch valve are kept in an open state.

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