Servo foundation pit test device and use method thereof

Abstract

The invention discloses a servo foundation pit test device and a use method thereof, and belongs to the field of foundation pit excavation model tests. The device comprises a model box for simulating a foundation pit and a support frame for carrying a simulation inner support, the model box comprises a box body, an enclosure wall is arranged in the box body through a detachable temporary fixator, a sliding baffle and a fixed baffle are arranged on one side of the box body, and the sliding baffle is fixed through an elastic gear; the supporting frame is provided with a plurality of layers of embedded guide rails, corresponding servo electric cylinders and embedded sliding blocks, and the embedded sliding blocks are provided with a plurality of supports. Two groups of upper fixed pulleys and lower fixed pulleys are respectively arranged at two ends of the support frame, and a steel wire rope is arranged on each group of pulleys and is used for adjusting the height of the embedded guide rail. According to the invention, the servo jack in the foundation pit is simulated as the support frame carrying the servo electric cylinder, the carried servo electric cylinder can accurately control the support axial force and the horizontal deformation of the enclosure wall, and the test device is suitable for foundation pit model tests of different support arrangement modes.

Description

Technical Field

[0001] This invention relates to the field of foundation pit excavation model testing, specifically to a servo foundation pit testing device and its usage method. Background Technology

[0002] In recent years, servo support systems have been increasingly widely used in deep foundation pit projects with strict environmental protection requirements due to their ability to dynamically adjust axial force according to excavation depth and thus actively control the displacement of the foundation pit retaining structure. Therefore, studying the impact of servo systems on foundation pits is of great significance.

[0003] The deformation characteristics of the foundation pit retaining structure are closely related to factors such as the support arrangement, the axial force settings of each support layer, and the excavation conditions. It is particularly important to note that the active earth pressure behind the retaining structure is not the ultimate earth pressure in the traditional sense; its magnitude changes with the wall deformation caused by the foundation pit excavation and the adjustment of the axial force of each servo support layer. However, due to the high cost of this support system in actual engineering projects, and for safety reasons, it is usually difficult to conduct experimental studies on the impact of dynamic axial force adjustment on the deformation and stress of the retaining structure under different support combination designs on site.

[0004] To thoroughly investigate the deformation law of the retaining structure during the excavation of servo-supported foundation pits, the mutual influence between the axial force settings of each layer of servo supports, and the coordinated deformation mechanism between the retaining structure and the non-ultimate earth pressure behind the wall, it is urgent to develop a servo-supported foundation pit model test device to solve the above-mentioned key technical problems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a servo foundation pit testing device and its usage method.

[0006] The objective of this invention is achieved through the following technical solution: a servo foundation pit testing device, comprising: a model box and a support frame; The model box includes a box body, and a pair of detachable temporary fasteners are provided inside the box body. A protective wall is provided through the detachable temporary fasteners. A sliding baffle and a fixed baffle are provided on one side of the box body. The sliding baffle is fixed by a tensioning gear. The support frame includes a base with several layers of embedded guide rails. Each embedded guide rail contains a servo electric cylinder and an embedded slider. The push rod of the servo electric cylinder is fixedly connected to one side of the embedded slider. The other side of the embedded slider has several support rods. The embedded guide rails have several partition plates, and the embedded slider can be inserted into any two adjacent partition plates. Two sets of pulleys are provided at each end of the base. Each set of pulleys includes an upper fixed pulley and a lower fixed pulley, and each set of pulleys has a steel wire rope. One end of the steel wire rope is fixedly connected to the embedded guide rail, and the other end is connected to the lower fixed pulley. The steel wire rope passes through the upper fixed pulley. By controlling the length of the steel wire rope, the height of the embedded guide rail on the support frame is adjusted.

[0007] Furthermore, the sliding baffle is disposed on the sliding groove of the housing, and a lubricant is applied between the sliding baffle and the sliding groove.

[0008] Furthermore, the sliding baffle is a multi-segment spliced ​​type.

[0009] Furthermore, the support frame includes a ground fixing device for fixing the support frame to the ground.

[0010] Furthermore, the push rod of the servo electric cylinder is connected to the embedded slider side via a connecting block.

[0011] Furthermore, the steel wire rope is provided with buckles at both ends.

[0012] Furthermore, the embedded guide rail is equipped with level bubbles at both ends to determine whether the installation height of the wire rope ensures that the installation is level.

[0013] Furthermore, the surface of the support rod is provided with strain gauges and temperature compensation gauges.

[0014] The present invention also provides a method for using a servo foundation pit testing device, comprising: During the adjustment phase, the sliding baffle of the model box is raised to the top and fixed with the tension gear; the retaining wall is fixed to the test setting position using the detachable temporary fixing device, the soil is laid and compacted, and the model box is installed after the soil is fully laid. Adjust the height of the embedded guide rail using a steel wire rope until the test setting height is reached; During the test phase, loosen the tension gear, lower the sliding baffle to the test height, adjust the tension gear to fix it, dig out the soil in the pit in the model box, and for the first support, place an additional baffle with a protrusion that can lock itself on top, and then arrange the connection support between the additional baffle and the retaining wall, which can withstand compression and tension. Except for the first support, after the soil in the pit in the model box is excavated, the embedded slider is pushed out by the servo electric cylinder to make the support rod contact the retaining wall.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention can change the support spacing by installing partition plates inside the guide rail, adjust the height of the upper and lower supports by steel wire ropes, and control the deformation of the retaining wall by adjusting the axial force and displacement of the supports with high precision through servo electric cylinders, thereby better simulating the actual scenario. Through servo electric cylinders, directional rails, and connecting devices, the loading and unloading of the current total axial force can be uniformly controlled in real time, or the system can be switched to displacement control mode, thereby controlling the support extension and retraction displacement, and thus controlling the horizontal displacement of the retaining structure at the set position. By using the axial force sensors of each support and the displacement sensors of the electric servo cylinders, the displacement of each support when it contacts the retaining structure can be determined, and the axial force of each support can be monitored in real time, thereby generating independent data images for each support. Modification of one side of the model box can better define the excavation height. A trolley and track can be arranged on the outside of the model box retaining wall excavation to simulate the traffic load that may exist in the actual construction site. This invention patent can realize the entire process of foundation pit excavation, and provides a reliable indoor experimental method for theoretical research on solving the coherence of axial forces of upper and lower supports and the changes in soil pressure when adjusting axial forces to control the displacement of the retaining structure in real time. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the device of the present invention; Figure 2 This is a schematic diagram of the model box of the present invention; Figure 3 This is a schematic diagram of the support frame of the present invention; In the diagram: 1-Box body; 2-Removable temporary fixture; 3-Enclosure wall; 4-Sliding baffle; 5-Tightening gear; 6-Fixed baffle; 7a-Upper fixed pulley; 7b-Lower fixed pulley; 8-Wire rope; 9-Support rod; 10-Embedded guide rail; 11-Divider plate; 12-Servo electric cylinder; 13-Embedded slider. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of this application.

[0019] In the description of this application, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. The terms "connected," "linked," and "set up" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a direct connection or an indirect connection through intermediate components; a wired connection, a radio connection, or a wireless communication signal connection. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0020] like Figure 1 As shown, this embodiment of the invention provides a servo foundation pit test device, wherein the geometric dimensions of the model box satisfy the geometric similarity ratio corresponding to the actual foundation pit project, and includes: a model box and a support frame.

[0021] like Figure 2 As shown, the model box includes a box body 1. Inside the box body 1, there is a pair of detachable temporary fasteners 2. A protective wall 3 is provided through the detachable temporary fasteners 2. A sliding baffle 4 and a fixed baffle 6 are provided on one side of the box body 1. The sliding baffle 4 is located above the fixed baffle 6. The sliding baffle 4 is located on the sliding groove of the box body 1. Lubricant is applied between the sliding baffle 4 and the sliding groove. The sliding baffle 4 is fixed by a tension gear 5. The tension gear 5 is installed outside the sliding baffle 4 and its height should be below the sliding baffle 4. The length of the protruding screw is controlled by rotating the tension gear 5 to lock the sliding baffle 4. The extension length in one direction should not cause the sliding baffle 4 to disengage from the sliding groove.

[0022] Preferably, the sliding baffle 4 is a multi-segment splicing type, and the splicing interface cross section can be set as a triangle or other type to prevent soil leakage inside the model box.

[0023] like Figure 3As shown, the support frame includes a support base, on which several layers of embedded guide rails 10 are provided. A servo electric cylinder 12 and an embedded slider 13 are provided within each embedded guide rail 10. The push rod of the servo electric cylinder 12 is fixedly connected to one side of the embedded slider 13. Several support rods 9 are provided on the other side of the embedded slider 13. Several partition plates 11 are provided on the embedded guide rails 10, and the embedded slider 13 can be inserted into any two adjacent partition plates 11. Two sets of pulleys 7 are provided at both ends of the support base. Each set of pulleys 7 includes an upper fixed pulley 7a and a lower fixed pulley 7b, and a steel wire rope 8 is provided on each set of pulleys 7. One end of the steel wire rope 8 is fixedly connected to the embedded guide rail 10, and the other end is connected to the lower fixed pulley 7b. The height of the embedded guide rail 10 on the support frame is adjusted by controlling the length of the steel wire rope 8 through the upper fixed pulley 7a.

[0024] Preferably, the support frame includes a ground fixing device for fixing the support frame to the ground.

[0025] Preferably, the embedded guide rail 10 is provided with level bubble at both ends to determine whether the wire rope 8 is installed horizontally when it is installed at a set height.

[0026] Preferably, the deformation monitoring of the retaining wall 3 can be carried out using digital imaging technology. By taking pictures with a camera, placing targets on the retaining wall 3, and combining particle image velocity analysis, the horizontal deformation of the retaining wall 3 can be obtained, and verified by combining it with a laser displacement sensor.

[0027] Preferably, a flexible inclinometer can be installed on the outside of the retaining wall 3 to measure the deep horizontal displacement of the soil.

[0028] Preferably, for earth pressure, miniature earth pressure boxes can be arranged on the outside of the retaining wall 3.

[0029] This invention also provides a method for using a servo foundation pit testing device, including: During the preparation phase, the support frame with the support rod 9 is positioned so that the side facing the model box is directly opposite, leaving enough space for the length of the support rod 9. The sliding baffle 4 of the model box is raised to the top and secured with the tensioning gear 5. The retaining wall 3 is fixed to the test position using the detachable temporary fixing device 2. Soil is layered and compacted inside the model box, and the model box is installed after the soil is fully filled.

[0030] After installation, the embedded guide rail 10, which includes the partition plate 11, servo electric cylinder 12, and embedded slider 13, is installed into the support frame. The embedded guide rail 10 is then fixed at the height set in the test plan by steel wire rope 8 in conjunction with the upper fixed pulley 7a and the lower fixed pulley 7b.

[0031] During the test phase, loosen the tension gear 5, lower the sliding baffle 4 to the test plan height, tighten the tension gear 5, and excavate the soil in the pit within the model box. Considering that in actual engineering, the first support is usually a reinforced concrete support, to simulate real working conditions, for the first support, place an additional baffle with a protrusion that can lock itself in place on top, and then arrange the connecting support between the additional baffle and the retaining wall 3. The arrangement can be simplified according to the actual working conditions. The first support should be able to withstand compression and tension. Since the arrangement methods differ for different foundation pits, it is not shown in the figure.

[0032] Except for the first support, after the soil in the pit in the model box is excavated, the embedded slider 13 is pushed out by the servo electric cylinder 12 to bring the support rod 9 into contact with the retaining wall 3. If the size ratio of the model box meets the requirements and the adjacent embedded guide rails 10 do not conflict, this test device can simulate not only the excavation stage, but also the support replacement stage.

[0033] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only.

[0034] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A servo foundation pit testing device, characterized in that, include: Model box and support frame; The model box includes a box body (1), and a pair of detachable temporary fixers (2) are provided inside the box body (1). A protective wall (3) is provided through the detachable temporary fixers (2). A sliding baffle (4) and a fixed baffle (6) are provided on one side of the box body (1). The sliding baffle (4) is fixed by a tension gear (5). The support frame includes a support base, on which several layers of embedded guide rails (10) are provided. A servo electric cylinder (12) and an embedded slider (13) are provided within each embedded guide rail (10). The push rod of the servo electric cylinder (12) is fixedly connected to one side of the embedded slider (13). Several support rods (9) are provided on the other side of the embedded slider (13). Several partition plates (11) are provided on the embedded guide rails (10). The embedded slider (13) can accommodate any two adjacent partition plates. In the partition plate (11); two sets of pulleys (7) are provided at both ends of the support. Each set of pulleys (7) includes an upper fixed pulley (7a) and a lower fixed pulley (7b). Each set of pulleys (7) is provided with a steel wire rope (8). One end of the steel wire rope (8) is fixedly connected to the embedded guide rail (10), and the other end is connected to the lower fixed pulley (7b). The steel wire rope (8) passes through the upper fixed pulley (7a). By controlling the length of the steel wire rope (8), the height of the embedded guide rail (10) on the support frame is adjusted.

2. The apparatus according to claim 1, characterized in that, The sliding baffle (4) is located on the sliding groove of the housing (1), and a lubricant is applied between the sliding baffle (4) and the sliding groove.

3. The apparatus according to claim 1, characterized in that, The sliding baffle (4) is a multi-segment splicing type.

4. The apparatus according to claim 1, characterized in that, The support frame includes a ground fixing device for fixing the support frame to the ground.

5. The apparatus according to claim 1, characterized in that, The push rod of the servo electric cylinder (12) is connected to one side of the embedded slider (13) via a connecting block.

6. The apparatus according to claim 1, characterized in that, The steel wire rope (8) has buckles at both ends.

7. The apparatus according to claim 1, characterized in that, The embedded guide rail (10) has level bubbles at both ends to determine whether the installation height of the wire rope (8) is guaranteed to be horizontal.

8. The apparatus according to claim 1, characterized in that, The surface of the support rod (9) is provided with strain gauges and temperature compensation gauges.

9. A method of using the device according to any one of claims 1-8, characterized in that, include: During the adjustment phase, the sliding baffle (4) of the model box is raised to the top and fixed by the tensioning gear (5); Use the detachable temporary fixing device (2) to fix the retaining wall (3) to the position set for the test, spread soil and compact it, and after the soil is fully spread, the model box is installed. Adjust the height of the embedded guide rail (10) by using the steel wire rope (8) until the test setting height is reached; During the test phase, loosen the tension gear (5), lower the sliding baffle (4) to the test height and then adjust the tension gear (5) to fix it. Dig out the soil in the pit in the model box. For the first support, place an additional baffle with a protrusion on top, and then arrange the connection support between the additional baffle and the retaining wall (3). It can be subjected to compression and tension. Except for the first support, after the soil in the pit in the model box is excavated, the embedded slider (13) is pushed out by the servo electric cylinder (12) to make the support rod (9) contact the retaining wall (3).

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