Foundation pit support structure model measuring device and measuring method

Abstract

The invention discloses a foundation pit support structure model measuring device and method, and the device comprises a model box which is provided with an opening at the upper end and is filled with sandy soil; the vertical enclosure plate is vertically arranged at one end of the model box and divides the model box into a test area and an excavation area; the multiple layers of steel supports are horizontally arranged in the excavation area; and the displacement testing mechanism is arranged in the excavation area and is used for processing the deformation quantity of the vertical enclosure plates at different height positions. Compared with a traditional pre-embedded displacement sensor measurement method, the model measurement device which is simple in structure and high in operability does not occupy the volume of soil around a foundation pit, the influence on a model test is smaller, the accuracy of the model test is improved, meanwhile, the horizontal displacement of the enclosure plate can be directly adjusted, and the measurement accuracy is improved. Different from a traditional measurement mode that a strain gauge is attached to the vertical enclosure plate to carry out internal force back calculation, the accuracy is improved, and therefore the horizontal displacement of the vertical enclosure plate is reasonably and accurately measured.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit retaining construction, and in particular to a foundation pit retaining structure model measuring device and a measuring method. Background Art

[0002] With the rapid development of economy, underground space has been vigorously developed in recent years, especially the number of deep and large foundation pits has been increasing. While promoting urban development, it also brings many hidden dangers, such as foundation pit collapse, pit bottom uplift and other accidents.

[0003] As the foundation pit is excavated step by step, the soil in the foundation pit is gradually unloaded, which causes a soil pressure difference inside and outside the foundation pit, resulting in horizontal displacement of the vertical retaining structure, which further affects the deformation and stability of the foundation pit. Therefore, the horizontal displacement of the vertical retaining structure is one of the major risk sources causing deformation and instability of the foundation pit.

[0004] However, due to the poor economy of field tests and the non-repeatability of test results, most scholars can only conduct relevant research through theoretical analysis, model experiments, and numerical analysis. However, in the process of conducting model tests, most scholars find it difficult to reasonably and accurately measure the horizontal displacement of the enclosure structure, which affects the accuracy of the test and needs to be improved. Summary of the invention

[0005] In view of the deficiencies in the prior art, an object of the present invention is to provide a foundation pit retaining structure model measuring device, which can reasonably and accurately measure the horizontal displacement of the retaining structure.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: a foundation pit retaining structure model measurement device and measurement method, comprising: The model box is opened at the top and filled with sand; A vertical enclosure plate is vertically arranged at one end of the model box and divides the model box into a test area and an excavation area; Multi-layer steel supports are horizontally arranged in the excavation area and support the vertical enclosure panels; The displacement testing mechanism is arranged in the excavation area and is used to process the deformation of the vertical retaining plates at different height positions.

[0007] In a preferred example, the present invention can be further configured as follows: the displacement testing mechanism includes a guide rail, a slider, a bracket and a laser displacement sensor, the guide rail vertically leans against the inner wall of the excavation area, the slider is vertically slidably connected to the guide rail, the bracket is horizontally arranged on the slider, and the laser displacement sensor is arranged at the front end of the bracket and close to the vertical guard plate.

[0008] In a preferred example, the present invention can be further configured as follows: the outer wall of the model box is provided with a strong magnet for adsorbing the vertical enclosure plate.

[0009] In a preferred example, the present invention can be further configured as follows: the steel support includes an inner tube, an outer tube, a two-way nut and an axial force sensor, the two-way nut is threadedly connected between the inner tube and the outer tube, and the axial force sensor is arranged on the outer tube and abuts against the vertical guard plate.

[0010] In a preferred example, the present invention can be further configured as follows: a gasket is provided at the end of the inner tube, and the gasket is bonded to the inner wall of the model box by glue.

[0011] In a preferred example, the present invention can be further configured as follows: a holder for embedding the axial force sensor is bonded to the side wall of the vertical enclosure plate.

[0012] In a preferred example, the present invention can be further configured as follows: the model box includes a steel frame, a steel plate and an acrylic transparent plate, the steel plate is arranged on the front and rear sides of the steel frame, and the acrylic transparent plate is arranged on the left and right ends of the steel frame and aligned with the excavation area.

[0013] In view of the deficiencies in the prior art, another object of the present invention is to provide a method for measuring a foundation pit retaining structure model, which can reasonably and accurately measure the horizontal displacement of the retaining structure.

[0014] The above technical objectives of the present invention are achieved through the following technical solutions: A method for measuring a foundation pit retaining structure model, comprising the following steps: S1, preparation work, prepare digital display micrometer, laser displacement sensor, axial force sensor, strain gauge, earth pressure box and auxiliary tools, and test and pre-calibrate various measuring instruments, and then stick strain gauges and earth pressure boxes on the vertical enclosure plates according to the designed measuring point positions; S2, filling of sand and placement of embedded parts. Before filling, wipe the model box clean. In order to eliminate the influence of boundary effect as much as possible, evenly apply a layer of vaseline on the inner wall of the model box, and then fill the sand in layers, 100mm per layer, and tamp it with a heavy hammer to ensure that the soil layer is dense and uniform as much as possible. When the filling is 310mm away from the bottom of the model box, the vertical retaining plate is vertically inserted into the model box, and then a strong magnet is installed on the outer wall of the model box to achieve the adsorption and fixation of the vertical retaining plate, and always ensure that the vertical retaining plate and the bottom of the model box are always vertical. The gap between the vertical retaining plate and the model box is sealed with a sand stop film, and a certain expansion space is reserved. Then continue to fill the sand. When the filling is 835mm away from the bottom of the model box, place the tunnel simulation pipe ring, and then continue to fill the sand. When the filling is 1200mm, 1300mm and 1400mm, embed the settlement rod respectively. After the sand is filled, the corresponding digital micrometer is measured according to the measurement point position arrangement; S3, connect the data acquisition instrument, connect the leads of the soil pressure box, axial force sensor and strain gauge to the data acquisition instrument, and debug the data acquisition system. When the sand and soil are left to stand for 24 hours and the data acquisition instrument readings do not change, the foundation pit can be excavated; S4, foundation pit excavation. Before excavation, the data acquisition system is checked again and cleared. Each excavated layer is left to stand for 3 hours to ensure that stable data is collected. The specific excavation process is as follows; First, excavate the surface sand and soil, dig 3cm, to facilitate the erection of the first steel support; Complete the first layer of soil excavation: excavate to 17cm, corresponding to an actual depth of 4.25m, and set up the second steel support; Complete the second layer of soil excavation: excavate to 34cm, corresponding to an actual depth of 8.5m, and set up the third steel support; Complete the third layer of soil excavation: excavate to 51cm, corresponding to an actual depth of 12.75m, and set up the fourth steel support; Complete the excavation of the fourth soil layer: excavation to 68cm, corresponding to an actual depth of 17m; After the foundation pit excavation was completed and left to stand for 24 hours, the horizontal displacement value of the vertical retaining plate was measured using a displacement testing mechanism to determine the elongation length of the three layers of steel support below, in preparation for the next servo loading.

[0015] In summary, the present invention has the following beneficial effects: 1. By setting up a model measurement device with a simple structure and strong operability, compared with the traditional embedded displacement sensor measurement method, it does not occupy the volume of the soil around the foundation pit, and has less impact on the model test, thereby improving the accuracy of the model test. At the same time, the horizontal displacement of the vertical retaining plate can be directly measured, which is different from the traditional measurement method of attaching strain gauges on the vertical retaining plate to perform internal force back calculation, thereby improving the accuracy, thereby reasonably and accurately measuring the horizontal displacement of the vertical retaining plate; 2. By setting up a displacement test mechanism with freely adjustable position, the horizontal displacement of the vertical enclosure plate at different depths can be measured, and the horizontal displacement of each position of the vertical enclosure plate can be measured more flexibly and comprehensively, thereby improving the accuracy and authority of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of Example 1; Figure 2 is a schematic diagram of the positional relationship of the vertical enclosure plate, steel support and displacement testing mechanism of Example 1; Figure 3 is a schematic structural diagram of the steel support of Example 1; Figure 4 It is a structural schematic diagram of the displacement testing mechanism of Example 1.

[0017] Figure numerals: 1. Model box; 11. Steel frame; 12. Steel plate; 13. Acrylic transparent plate; 2. Vertical enclosure plate; 21. Test area; 22. Excavation area; 3. Steel support; 31. Inner tube; 32. Outer tube; 33. Two-way nut; 34. Axial force sensor; 35. Gasket; 36. Holder; 4. Displacement test mechanism; 41. Guide rail; 42. Slider; 43. Bracket; 44. Laser displacement sensor; 5. Strong magnet. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0019] Embodiment 1: like Figure 1 , Figure 2 As shown, a foundation pit retaining structure model measurement device includes a model box 1, a vertical retaining plate 2, a multi-layer steel support 3 and a displacement testing mechanism 4.

[0020] like Figure 1 As shown, the model box 1 adopts an upper open box structure with a size of 2500mm*2000mm*1500mm, and is filled with dry sand. The model box 1 includes a steel frame 11, a steel plate 12 and an acrylic transparent plate 13. The steel plate 12 is arranged on the front and rear sides of the steel frame 11, and the acrylic transparent plate 13 is arranged on the left and right ends of the steel frame 11 for easy experimental observation.

[0021] like Figure 1 As shown, the vertical enclosure plate 2 is vertically arranged at one end of the model box 1 to simulate the retaining wall structure in actual construction. The vertical enclosure plate 2 is 5 mm thick according to the bending stiffness equivalent principle, and the model box 1 is divided into a test area 21 and an excavation area 22. The outer wall of the model box 1 is provided with a strong magnet 5 for adsorbing the vertical enclosure plate 2, so as to realize the rapid and firm fixation of the vertical enclosure plate 2.

[0022] like Figure 1 , Figure 2 As shown, multiple layers of steel supports 3 are horizontally arranged in the excavation area 22, and support the vertical enclosure panels 2. The steel supports 3 are arranged in four layers, and each layer has six steel supports arranged at equal intervals.

[0023] like Figure 1 , Figure 3 As shown, the steel support 3 includes an inner tube 31, an outer tube 32, a two-way nut 33 and an axial force sensor 34, and the two-way nut 33 is threadedly connected between the inner tube 31 and the outer tube 32. A gasket 35 is provided at the end of the inner tube 31, and the gasket 35 is bonded to the inner wall of the model box 1 by glue.

[0024] like Figure 1 , Figure 3 As shown, the axial force sensor 34 is arranged on the outer tube 32 and is used to press against the vertical enclosure plate 2. The side wall of the vertical enclosure plate 2 is pasted with a holder 36 for the axial force sensor 34 to be embedded. On the one hand, it can fix the steel support 3, and on the other hand, it can prevent the axial force sensor 34 from rotating, thereby effectively achieving the purpose of extending the steel support 3 through rotation.

[0025] like Figure 2 , Figure 4 As shown, the displacement testing mechanism 4 is arranged in the excavation area 22 and is used to process the deformation of the vertical enclosure plate 2 at different height positions. The displacement testing mechanism 4 includes a guide rail 41, a slider 42, a bracket 43 and a laser displacement sensor 44.

[0026] like Figure 2 , Figure 4 As shown, the guide rail 41 is vertically leaning against the inner wall of the excavation area 22, the slider 42 is vertically slidably connected to the guide rail 41, the bracket 43 is horizontally arranged on the slider 42, and the laser displacement sensor 44 is arranged at the front end of the bracket 43 and close to the vertical guard plate 2.

[0027] When conducting the test, the vertical retaining plate 2 is first placed vertically in the model box 1, and then the vertical retaining plate 2 is adsorbed and fixed by a strong magnet 5, and then sand is filled into the model box 1 so that the sand fills the test area 21 and the excavation area 22 on both sides of the vertical retaining plate 2.

[0028] Then fix the topmost steel support 3 first. During the installation of the steel support 3, first place the right end of the assembled steel support 3 rod into the position of the gasket 35 on the inner wall of the model box 1, and then gently insert the left end of the steel support 3 into the seat 36 on the vertical enclosure plate 2, and finally rotate the two-way nut 33 to extend the steel support 3 so that the two ends of the steel support 3 are completely in contact with the inner wall of the model box 1 and the inner wall of the vertical enclosure plate 2.

[0029] In the actual installation process, the axial force sensor 34 does not need to be installed on the topmost steel support 3. It is only necessary to support the model box 1 and the vertical retaining plate 2. Then, the foundation pit is excavated in multiple layers along the depth direction in the excavation area 22. The excavated foundation pit sand is divided into four layers in total.

[0030] The first layer of soil was excavated to 17 cm, corresponding to an actual depth of 4.25 m, and the second support was erected.

[0031] The second layer of soil was excavated to 34cm, corresponding to an actual depth of 8.5m, and the third support was erected.

[0032] The third layer of soil was excavated to 51cm, corresponding to an actual depth of 12.75m, and the fourth support was erected.

[0033] The fourth layer of soil was excavated to 68cm, corresponding to an actual depth of 17m.

[0034] After waiting for the excavation of the foundation pit to be completed and standing for 24 hours, the guide rail 41 is vertically leaned against the inner wall of the model box 1, and the slider 42 is pushed to slide vertically to 17 cm, 34 cm, 51 cm and 68 cm. Then, the light of the laser displacement sensor 44 is shone on the measuring point of the vertical retaining plate 2 to measure the initial position value ai of the vertical retaining plate 2. After the test simulation of the foundation pit excavation is completed, the position value 𝑏i of the vertical retaining plate 2 is measured by this method, and 𝑏i-ai is the horizontal displacement of the vertical retaining plate 2 when the excavation is completed.

[0035] And after the horizontal displacement value of the vertical guard plate 2 is measured by the laser displacement sensor 44, the elongation length of the steel support 3 can be determined to prepare for the next servo loading. After the steel support 3 is servo loaded, the position value ci of the vertical guard plate 2 after servo loading can also be measured. Then ci-bi can be used to obtain the horizontal displacement change value of the vertical guard plate 2 under the action of the servo. During excavation, the displacement testing mechanism 4 can be removed at any time without interfering with the excavation process.

[0036] Therefore, by setting up a model measurement device with a simple structure and strong operability, compared with the traditional embedded displacement sensor measurement method, it is possible not to occupy the volume of the soil around the foundation pit, and to have less impact on the model test, thereby improving the accuracy of the model test.

[0037] At the same time, the horizontal displacement of the vertical enclosure plate 2 can be directly measured, which is different from the traditional measurement method of attaching strain gauges on the vertical enclosure plate 2 to back-calculate the internal force, thereby improving the accuracy, thereby reasonably and accurately measuring the horizontal displacement of the vertical enclosure plate 2.

[0038] By setting a displacement testing mechanism 4 whose position can be freely adjusted, the horizontal displacement of the vertical enclosure plate 2 at different depths can be measured, and the horizontal displacement of each position of the vertical enclosure plate 2 can be measured more flexibly and comprehensively, thereby improving the accuracy and authority of the test.

[0039] Embodiment 2: A method for measuring a foundation pit retaining structure model comprises the following steps: S1, preparation work, prepare digital display micrometer, laser displacement sensor, axial force sensor, strain gauge, earth pressure box and auxiliary tools, and test and pre-calibrate various measuring instruments, and then stick strain gauges and earth pressure boxes on the vertical enclosure plates according to the designed measuring point positions; S2, filling of sand and placement of embedded parts. Before filling, wipe the model box clean. In order to eliminate the influence of boundary effect as much as possible, evenly apply a layer of vaseline on the inner wall of the model box, and then fill the sand in layers, 100mm per layer, and tamp it with a heavy hammer to ensure that the soil layer is dense and uniform as much as possible. When the filling is 310mm away from the bottom of the model box, the vertical retaining plate is vertically inserted into the model box, and then a strong magnet is installed on the outer wall of the model box to achieve the adsorption and fixation of the vertical retaining plate, and always ensure that the vertical retaining plate and the bottom of the model box are always vertical. The gap between the vertical retaining plate and the model box is sealed with a sand stop film, and a certain expansion space is reserved. Then continue to fill the sand. When the filling is 835mm away from the bottom of the model box, place the tunnel simulation pipe ring, and then continue to fill the sand. When the filling is 1200mm, 1300mm and 1400mm, embed the settlement rod respectively. After the sand is filled, the corresponding digital micrometer is measured according to the measurement point position arrangement; S3, connect the data acquisition instrument, connect the leads of the soil pressure box, axial force sensor and strain gauge to the data acquisition instrument, and debug the data acquisition system. When the sand and soil are left to stand for 24 hours and the data acquisition instrument readings do not change, the foundation pit can be excavated; S4, foundation pit excavation. Before excavation, the data acquisition system is checked again and cleared. Each excavated layer is left to stand for 3 hours to ensure that stable data is collected. The specific excavation process is as follows; First, excavate the surface sand and soil, dig 3cm, to facilitate the erection of the first steel support; Complete the first layer of soil excavation: excavate to 17cm, corresponding to an actual depth of 4.25m, and set up the second steel support; Complete the second layer of soil excavation: excavate to 34cm, corresponding to an actual depth of 8.5m, and set up the third steel support; Complete the third layer of soil excavation: excavate to 51cm, corresponding to an actual depth of 12.75m, and set up the fourth steel support; Complete the excavation of the fourth soil layer: excavation to 68cm, corresponding to an actual depth of 17m; After the foundation pit excavation was completed and left to stand for 24 hours, the horizontal displacement value of the vertical retaining plate was measured using a displacement testing mechanism to determine the elongation length of the three layers of steel support below, in preparation for the next servo loading.

[0040] The specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make modifications to the embodiments without any creative contribution as needed. However, such modifications are protected by the patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A foundation pit retaining structure model measurement device, characterized in that: include: The model box (1) is open at the top and filled with sand; A vertical enclosure plate (2) is vertically arranged at one end of the model box (1) and divides the model box (1) into a test area (21) and an excavation area (22); A multi-layer steel support (3) is horizontally arranged in the excavation area (22) and supports the vertical enclosure plate (2); A displacement testing mechanism (4) is arranged in the excavation area (22) and is used to process the deformation of the vertical enclosure plate (2) at different height positions.

2. The foundation pit retaining structure model measuring device according to claim 1, characterized in that: The displacement testing mechanism (4) comprises a guide rail (41), a slider (42), a bracket (43) and a laser displacement sensor (44); the guide rail (41) is vertically supported on the inner wall of the excavation area (22); the slider (42) is vertically slidably connected to the guide rail (41); the bracket (43) is horizontally arranged on the slider (42); and the laser displacement sensor (44) is arranged at the front end of the bracket (43) and close to the vertical enclosure plate (2).

3. The foundation pit retaining structure model measuring device according to claim 1, characterized in that: The outer wall of the model box (1) is provided with a strong magnet (5) for adsorbing the vertical enclosure plate (2).

4. The foundation pit retaining structure model measuring device according to claim 1, characterized in that: The steel support (3) comprises an inner tube (31), an outer tube (32), a two-way nut (33) and an axial force sensor (34); the two-way nut (33) is threadedly connected between the inner tube (31) and the outer tube (32); the axial force sensor (34) is arranged on the outer tube (32) and contacts the vertical enclosure plate (2).

5. The foundation pit retaining structure model measuring device according to claim 4 is characterized in that: A gasket (35) is provided at the end of the inner tube (31), and the gasket (35) is bonded to the inner wall of the model box (1) by glue.

6. The foundation pit retaining structure model measuring device according to claim 4, characterized in that: A holder (36) for embedding the axial force sensor (34) is bonded to the side wall of the vertical enclosure plate (2).

7. The foundation pit retaining structure model measuring device according to claim 1, characterized in that: The model box (1) comprises a steel frame (11), a steel plate (12) and an acrylic transparent plate (13), wherein the steel plate (12) is arranged at the front and rear sides of the steel frame (11), and the acrylic transparent plate (13) is arranged at the left and right ends of the steel frame (11) and is aligned with the excavation area (22).

8. A method for measuring a foundation pit retaining structure model, using a measuring device as claimed in any one of claims 1 to 7, characterized in that: The steps include: S1, preparation work, prepare digital display micrometer, laser displacement sensor, axial force sensor, strain gauge, earth pressure box and auxiliary tools, and test and pre-calibrate various measuring instruments, and then stick strain gauges and earth pressure boxes on the vertical enclosure plates according to the designed measuring point positions; S2, filling of sand and placement of embedded parts. Before filling, wipe the model box clean. In order to eliminate the influence of boundary effect as much as possible, evenly apply a layer of vaseline on the inner wall of the model box, and then fill the sand in layers, 100mm per layer, and tamp it with a heavy hammer to ensure that the soil layer is dense and uniform as much as possible. When the filling is 310mm away from the bottom of the model box, the vertical retaining plate is vertically inserted into the model box, and then a strong magnet is installed on the outer wall of the model box to achieve the adsorption and fixation of the vertical retaining plate, and always ensure that the vertical retaining plate and the bottom of the model box are always vertical. The gap between the vertical retaining plate and the model box is sealed with a sand stop film, and a certain expansion space is reserved. Then continue to fill the sand. When the filling is 835mm away from the bottom of the model box, place the tunnel simulation pipe ring, and then continue to fill the sand. When the filling is 1200mm, 1300mm and 1400mm, embed the settlement rod respectively. After the sand is filled, the corresponding digital micrometer is measured according to the measurement point position arrangement; S3, connect the data acquisition instrument, connect the leads of the soil pressure box, axial force sensor and strain gauge to the data acquisition instrument, and debug the data acquisition system. When the sand and soil are left to stand for 24 hours and the data acquisition instrument readings do not change, the foundation pit can be excavated; S4, foundation pit excavation. Before excavation, the data acquisition system is checked again and cleared. Each excavated layer is left to stand for 3 hours to ensure that stable data is collected. The specific excavation process is as follows; First, excavate the surface sand and soil, dig 3cm, to facilitate the erection of the first steel support; Complete the first layer of soil excavation: excavate to 17cm, corresponding to an actual depth of 4.25m, and set up the second steel support; Complete the second layer of soil excavation: excavate to 34cm, corresponding to an actual depth of 8.5m, and set up the third steel support; Complete the third layer of soil excavation: excavate to 51cm, corresponding to an actual depth of 12.75m, and set up the fourth steel support; Complete the excavation of the fourth soil layer: excavation to 68cm, corresponding to an actual depth of 17m; After the foundation pit excavation was completed and left to stand for 24 hours, the horizontal displacement value of the vertical retaining plate was measured using a displacement testing mechanism to determine the elongation length of the three layers of steel support below, in preparation for the next servo loading.

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