CN216899889U - Model test device for simulating continuous damage of pile-anchor support foundation pit caused by anchor rod failure - Google Patents

Abstract

The utility model discloses a model test device for simulating continuous damage of a pile anchor supporting foundation pit caused by failure of an anchor rod, which comprises a rectangular model box, wherein a sand body is scattered in the model box, a simulation foundation pit is dug in the sand body, one side of the simulation foundation pit is provided with a containment structure, the containment structure is provided with a soil pressure monitoring device and a strain gauge, an anchor rod is connected to a crown beam, the anchor rod is made of steel stranded wires, penetrates through the rear side wall of the model box and is fixedly connected with a hollow bolt which is vertically arranged above the anchor rod by bypassing a fixed pulley, the hollow bolt is fixed at the top of the rear side wall of the model box, a tension meter is connected to a rod section of the anchor rod, which is positioned outside the model box, a guide rail support is arranged outside the model box, and a sanding trolley is arranged on the guide rail support. The method adopts a similar principle to simulate the continuous damage of the pile-anchor supporting foundation pit caused by the local anchor rod failure, and is convenient for exploring the load transfer rule when the continuous damage of the pile-anchor supporting foundation pit caused by the local anchor rod failure is caused.

Description

Model test device for simulating the continuous failure of the pile-anchor support foundation pit caused by the failure of the bolt

technical field

The utility model relates to a test device in foundation pit engineering, in particular to a model for simulating the failure of partial anchor rods in the support foundation pit and exploring the load transfer law when the local anchor rods of the foundation pit fail in the study of the anchor rod support system. test device.

Background technique

As a common foundation pit support system, bolt support is mostly used in large-scale engineering, complex surrounding environment, and irregular foundation pit shapes. In the bolt-supported foundation pit, the rational use of the bolt can effectively control the soil deformation, reduce the internal force of the enclosure structure, reduce the engineering cost and improve the construction efficiency. However, in actual projects, foundation pit collapse accidents caused by improper bolt design and construction also occur from time to time. For example, in Cologne, Japan, Zhengzhou, Nanning and other places, there have been foundation pit collapse accidents caused by local bolt failure. , causing huge property damage.

In recent years, many scholars have analyzed a large number of bolt engineering examples or accident cases. For example, the International Federation for Prestressing (FIP) conducted a statistical analysis on 35 bolt support engineering cases. Among them, there is a risk of failure of the bolt in many projects, and even some projects have caused structural collapse due to the failure of the bolt.

However, the current research methods of foundation pit stability are only limited to the two-dimensional case, the critical state where the foundation pit is about to be destroyed. The theory of continuous collapse prevention in foundation pit engineering. In addition, the current research on continuous failure of deep foundation pits is mainly aimed at cantilever pile row, ring beam horizontal support structure system and inner support pile row pile support system. For the support form, the mechanism and process of continuous failure caused by local failure and the control of the overall safety of the foundation pit need to be studied urgently. Therefore, it is necessary to provide a model test device and method for simulating the continuous failure of the pile-anchor support foundation pit caused by partial anchor failure, so as to reveal the load transfer mechanism of the continuous failure caused by the local anchor failure which is still lacking at this stage.

Utility model content

The utility model provides a model test device for simulating the continuous failure of a pile-anchor support foundation pit caused by failure of an anchor rod in order to solve the technical problems existing in the known technology.

The technical scheme adopted by the utility model to solve the technical problems existing in the known technology is: a model test device for simulating the failure of the anchor rod to cause the continuous failure of the pile-anchor support foundation pit, including a rectangular model box, inside the model box A sand body is sprinkled, and a simulated foundation pit is dug in the sand body. The simulated foundation pit is located on the front side of the model box, three sides are adjacent to the side walls of the model box, and one side is provided with an enclosure structure. Earth pressure monitoring equipment is installed on the enclosure structure, the enclosure structure includes support piles and crown beams, and strain gauges are pasted on the inner sides of the support piles and the crown beams. A leak-proof film is bonded between the two adjacent supporting piles; the crown beam is supported by the corbels, the two are fixedly connected, and the corbels are fixed on the inner top of the corresponding supporting piles. An anchor rod is connected to the crown beam, and the anchor rod is made of steel strands. The hollow bolt is connected, the hollow bolt is connected to the support plate, the support plate is fixed to the top of the rear side wall of the model box, and a tension force is connected to the rod section of the anchor rod located outside the model box The fixed pulley is installed on the outside of the rear side wall of the model box, and the left side wall or the right side wall of the model box is made of tempered glass plate; A guide rail is laid on the guide rail bracket, the guide rail spans the top of the model box, and a sand spreading trolley is arranged on the guide rail. The sand spreading trolley consists of an axle system and a sand bucket with a sand spreading valve. Composition; the sand spreading trolley is equipped with a sand transporting grab.

The middle and upper part of the front side wall of the model box is formed by splicing steel strips with the same length as the wall.

All the steel strips are of equal width.

A gap is left between the two ends of the crown beam and the side wall of the model box.

Both the support pile and the crown beam are made of rigid PVC rectangular hollow tubes.

The guide rails are arranged along the length direction of the model box.

The advantages and positive effects of the utility model are as follows: the similar principle is adopted to simulate the continuous failure of the pile-anchor support foundation pit caused by the failure of the local anchor rod, so as to facilitate the exploration of the load transfer law when the local anchor rod failure causes the continuous failure of the pile-anchor support foundation pit . The utility model has the advantages of small volume, reasonable structure, convenient test, good reliability, good applicability to pile-anchor support foundation pits of various sizes, simple structure and low cost.

Description of drawings

Figure 1 is a schematic structural diagram of the utility model.

In the picture: 1-model box; 2-rail bracket; 3-sand spreading trolley; 4-sand grab bucket; 5-support pile; 6-anchor rod; 7-crown beam; 8-tension gauge; 9-hollow Bolts; 10-fixed pulley; 11-axle system; 12-sand valve; 13-sand bucket; 14-steel strip; 15-corbel.

Detailed ways

In order to further understand the content of the invention, features and effects of the present utility model, the following embodiments are exemplified and described in detail as follows in conjunction with the accompanying drawings:

Please refer to FIG. 1, a model test device for simulating the failure of the anchor rod to cause the continuous failure of the pile-anchor support foundation pit, including a rectangular model box 1, in which a sand body is sprinkled, and the sand body is dug into the sand and soil body. There is a simulated foundation pit, the simulated foundation pit is located on the front side of the model box 1, three sides are adjacent to the side walls of the model box 1, and one side is provided with an enclosure structure.

Earth pressure monitoring equipment is installed on the enclosure structure. The enclosure structure includes support piles 5 and crown beams 7. Strain gauges are pasted on the inner sides of the support piles 5 and the crown beams 7. A leak-proof film is bonded between the two said supporting piles 5, which can prevent the sand outside the simulated foundation pit from leaking out of the pile joints.

The crown beam 7 is supported by the corbel 15, and the two are fixedly connected. The corbel 15 is fixed on the inner top of the corresponding support pile 5. The corbel 15 can be made of plexiglass and is bonded to the support with strong glue. On the guard post 5. The length of the crown beam is slightly shorter than the width of the model box to ensure that there are gaps between the two ends of the crown beam and the side wall of the model box to avoid friction affecting the load transfer of the support system. The crown beam is drilled according to the arrangement of the bolts to meet the requirements of bolt anchoring.

An anchor rod 6 is connected to the crown beam 7, and the anchor rod 6 is made of steel strands. The hollow bolts 9 located above and vertically arranged are fixed, and the hollow bolts 9 are connected to the support plate, and the support plate is fixed to the top of the rear side wall of the model box 1, and the anchor rod 6 is located at the top of the back wall of the model box 1. A tension gauge 8 is connected to the rod section outside the model box 1 , and the fixed pulley 10 is installed on the outside of the rear side wall of the model box 1 . During the test, the hollow bolt 9 can be rotated to raise or lower, so as to stretch or relax the anchor rod 6 to generate prestress or relax the axial force of the anchor rod. The tension gauge 8 can monitor the axial force of the bolt in real time and apply the prestress of the bolt accurately.

The middle and upper part of the front side wall of the model box 1 is formed by splicing steel strips 14 of equal wall length, and all the steel strips 14 have the same width. The assembled structure is used to facilitate the excavation of the foundation pit, and the steel strips 14 can be removed one by one during the excavation of the foundation pit.

The left or right side wall of the model box 1 is made of tempered glass plate, and the deformation of soil and structure can be observed during the test. , to ensure model box stiffness.

A guide rail bracket 2 is arranged on the outside of the model box 1, a guide rail is laid on the guide rail bracket 2, the guide rail spans the top of the model box 1, and a sand spreading trolley 3 is arranged on the guide rail. The sand spreading trolley 3 is composed of an axle system 11 and a sand bucket 13 with a sand spreading valve 12 .

The sand spreading trolley 12 is equipped with a sand transporting grab 4, which can transport sand from the sand storage tank to the sand bucket 13.

Since the sand spreading trolley 12 is located on the guide rail bracket 2 and is separated from the model box 1, it can avoid disturbing the model soil during sand spreading. Before sanding by the sand rain method, the anchor rod 6 is pre-placed in the model box according to the design position. One end of the anchor rod is anchored to the crown beam through the gap between the model piles, and the other end is finally anchored to the hollow bolt through the fixed pulley. superior.

In this embodiment, the guide rails are arranged along the length direction of the model box 1 . Both the support piles 5 and the crown beams 7 are made of rigid PVC rectangular hollow tubes.

The above-mentioned device is used to carry out the test, including the following steps:

First, the supporting piles are arranged, and then the earth pressure monitoring equipment is arranged on the envelope structure. The crown beam and anchor rod are pre-placed inside the foundation pit, but the outer end of the anchor rod is not anchored. Then, the sand-carrying grab bucket transports sand from the sand storage tank to the sand bucket, opens the sand-spraying valve, and the sand-spraying trolley moves back and forth along the length of the model box to spread sand by the sand rain method. After sanding, the steel strips of equal width are removed one by one and the foundation pit is excavated. After excavation to a certain depth, the outer end of the anchor rod is anchored to the top of the hollow bolt, and the hollow bolt is screwed up to apply a certain prestress to the anchor rod. , and then continue to excavate the foundation pit to the experimental design depth. Cut the bolts in the order of the test design until the foundation pit collapses continuously.

The utility model can be used to study the continuous failure of the foundation pit caused by the failure of local anchor rods, so as to reveal the load transfer mechanism caused by the failure of the local anchor rods of the pile-anchor support foundation pit.

Although the preferred embodiments of the present utility model have been described above in conjunction with the accompanying drawings, the present utility model is not limited to the above-mentioned specific embodiments, which are only illustrative and not restrictive. Under the inspiration of the present utility model, those of ordinary skill can also make many forms without departing from the scope of protection of the present utility model and the claims, which all belong to the protection scope of the present utility model.

Claims (6)

1. a model test device that simulates the failure of the bolt to cause the continuous damage of the pile-anchor support foundation pit, is characterized in that, comprises a rectangular model box, A sand body is sprinkled in the model box, and a simulated foundation pit is dug in the sand body. The simulated foundation pit is located on the front side of the model box, three sides are adjacent to the side walls of the model box, and one side is provided with An enclosure structure, on which an earth pressure monitoring device is installed, the enclosure structure includes a support pile and a crown beam, and strain gauges are pasted on the inner side of the support pile and the crown beam, and the A leak-proof film is bonded on the inner side of the enclosure structure and between the two adjacent supporting piles; The crown beam is supported by the corbel, the two are fixedly connected, the corbel is fixed on the inner top of the corresponding supporting pile, and an anchor rod is connected to the crown beam, and the anchor rod is made of steel strands. made, the anchor rod passes through the rear side wall of the model box and bypasses the fixed pulley to be fixed with the hollow bolts located above and vertically arranged, the hollow bolts are connected to the support plate, and the support The plate is fixed on the top of the rear side wall of the model box, a tension gauge is connected to the rod section where the anchor rod is located outside the model box, and the fixed pulley is installed on the outside of the rear side wall of the model box, The left side wall or the right side wall of the model box is made of tempered glass plate; A guide rail bracket is provided on the outside of the model box, a guide rail is laid on the guide rail bracket, the guide rail spans the top of the model box, and a sand spreading trolley is arranged on the guide rail, and the sand spreading trolley consists of Axle system and sand bucket with sand-spraying valve; The sand spreading trolley is equipped with a sand transporting grab. 2. The model test device for simulating bolt failure to cause continuous failure of pile-anchor support foundation pit according to claim 1, characterized in that, the middle and upper part of the front side wall of the model box is made of a steel plate with the same length as the wall length. stitched together. 3 . The model test device for simulating the failure of the bolt to cause the continuous failure of the pile-anchor support foundation pit according to claim 2 , wherein the widths of all the steel strips are equal. 4 . 4 . The model test device for simulating bolt failure to cause continuous failure of pile-anchor support foundation pit according to claim 1 , wherein there are gaps between the two ends of the crown beam and the side walls of the model box. 5 . 5. The model test device for simulating bolt failure to cause continuous failure of pile-anchor support foundation pit according to claim 1, wherein the support pile and the crown beam are made of rigid PVC rectangular hollow pipes completed. 6 . The model test device for simulating the failure of bolts to cause continuous failure of pile-anchor support foundation pits according to claim 1 , wherein the guide rails are arranged along the length direction of the model box. 7 .

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