CN109900563B - Surface Shear Test Method for Oversized Anchorage Structures - Google Patents

Abstract

A shear test method for an oversized anchoring structure surface comprises the following steps: (1) manufacturing a plurality of anchor rod-containing cement-based samples according to the indoor sample similarity ratio principle, wherein the samples are cubes containing bosses, the bosses on the side edges are respectively rectangular, and the rectangular bosses are square; (2) inserting an anchor rod in the sample preparation process, and arranging a high-temperature and high-pressure resistant multifunctional fiber grating sensor; (3) combining the samples into a plurality of sample blocks with series sizes; (4) preparing a shear test loading module matched with a series of oversized samples; (5) judging the stress condition of the boss by utilizing the monitored stress, strain, displacement and acoustic emission information; (6) and (5) repeating the steps (1) to (5) to design the shearing test of the oversized anchoring structure surface containing the triangular lug bosses. The invention improves the matching, rationality and scientificity of test results, solves the problem of difficult installation of oversized samples and reduces the potential safety hazard in the shearing test process.

Description

Surface Shear Test Method for Oversized Anchorage Structures

technical field

The invention belongs to the technical field of indoor physical and mechanical tests, and in particular relates to a shear test method for super-large-scale anchoring structures.

Background technique

Rock slope is closely related to human living environment and geological engineering activities, and is one of the most basic and extremely important natural geological environments. With the rapid population growth and the over-exploitation of land resources, the slope problem has become one of the three major global geological disasters (sources) alongside earthquakes and volcanoes. In the process of human development, it is always in conflict, influence and coordination with it, and then achieves interdependence. Some rock slopes become permanent "artificial natural signs" after going through the process of unstable state to stable state. , integrated into the geological environment. With the large-scale construction of national infrastructure and the active promotion of the strategy of developing the western region, the high and steep slopes in the fields of water conservancy and hydropower engineering, railway engineering, highway engineering and other fields are increasing day by day, resulting in the problem of slope rock mass stability. It is one of the most common, economical and effective methods in the reinforcement and support treatment of high slopes. Rock mass anchoring is an important branch in the field of geotechnical engineering, and the study of rock mass anchoring performance is the key to the success or failure of rock mass anchoring technology. Rock mass anchoring refers to the use of anchor rods, prestressed anchor rods and anchor cables to improve the stress state of the rock mass to mobilize and improve the rock mass itself in order to prevent and control geological disasters such as landslides, surface subsidence, and roadway collapse. measures of strength and self-stabilization. For large-scale open-pit mine rock slopes, the instability mode is basically shear slip along the structural plane, so the shear load on the anchoring structural plane cannot be ignored. At present, some scholars have carried out single-joint or double-joint direct shear tests using large-scale concrete or rock specimens (structural surface dimensions ranging between 30cm×30cm and 30cm×80cm) and high-strength steel bars (diameter 8-40mm). In the test, the influence of the surface size effect of the anchoring structure is ignored. Some scholars have proposed a full-scale shear test. The length of the structural surface reaches several meters or even tens of meters, the number of bolts required reaches tens of bolts, and the shear force reaches thousands of tons. It belongs to the super-large shear test. There is often a large stress concentration at the force, causing the diameter of the sample to be crushed. Therefore, a new shear test design is needed from the aspect of specimen force.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the above-mentioned prior art, the present invention provides an oversized anchoring structure surface shear test method, which can avoid local damage caused by stress concentration at the end of an oversized sample, and can ensure that the anchor rod is subjected to synergistic force, improving the The test results are matched, rational and scientific, and at the same time, it can solve the difficulty of installing super-large samples, and reduce the safety hazard in the shear test process. The preparation process of cement-based samples is simple, easy to use, low in cost, and suitable for It can provide a scientific basis for the design of super-large-scale experiments.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A shear test method for an oversized anchor structure surface, comprising the following steps:

(1) According to the principle of indoor sample similarity ratio, make multiple cement-based samples with anchor rods. The samples are cubes with bosses, and the side bosses are rectangles. The side length of the samples is 4l, and 0.4m≤l ≤0.8m, the rectangular boss is square, the side length is 0.5l, and the spacing is l;

(2) In the process of sample preparation, the anchor rod is inserted, and the whole length is bonded and anchored, and the high temperature and high pressure multi-functional fiber grating sensor is arranged at the same time. The distance between the structure surface and the boss is 0.1m, and the distance between other positions is 0.2m;

(3) Combine the samples into a series of multi-block samples, the number of blocks in the shearing direction is n, 2≤n≤10, the number of blocks in the width direction is 2, and the number of blocks in the height direction is 2 The number of bodies is 2;

(4) According to the national standard (GBT 1591-2018), select low-alloy high-strength steel to prepare shear test loading modules that match the series of super-large samples;

(5) Assemble the multi-block sample and the shear test module, and perform the shear test on the large-scale direct shear instrument platform, arrange the acoustic emission probe on the surface of the module, and use the monitored stress, strain, displacement and sound. Emission information to judge the force of the boss;

(6) Repeat steps (1)-(5) to carry out the shear test design of the super-large anchorage structure with triangular bosses, wherein the triangular bosses are equilateral triangles with a side length of 0.8l.

Further, in the step (1), various composite materials such as magnesia ash can be added to the cement base to improve its strength.

Still further, in the step (2), the diameter of the anchor rod is 10-40 mm, and the anchoring diameter is twice the diameter of the anchor rod.

Further, in the step (3), if it is monitored that the boss is deformed or cracked seriously, it is necessary to increase the size of the boss and increase the strength at the same time.

Compared with the prior art, the present invention can avoid local damage caused by stress concentration at the end of the super-sized sample, and can ensure the coordinating force of the anchor rod, improve the matching, rationality and scientificity of the test results, and at the same time. It can solve the installation difficulty of super-sized samples and reduce the safety hazard in the shear test process. The preparation process of cement-based samples is simple, easy to use, low in cost, and has a wide range of applications, which provides a scientific basis for the design of super-sized tests.

Description of drawings

Fig. 1 is the design diagram of the shear test of the rectangular boss anchoring structure surface sample of the present invention; wherein, (a) a single sample; (b) a multi-block composite sample; (c) a shear loading module.

Fig. 2 is a design diagram of shear test of the triangular boss anchoring structure surface sample of the present invention; wherein, (a) a single sample; (b) a multi-block composite sample; (c) a shear loading module.

Detailed ways

The present invention will be further described below.

As shown in Figure 1, a shear test method for super-large-scale anchoring structures includes the following steps:

(1) According to the principle of indoor sample similarity ratio, multiple cement-based samples with anchor rods were made. The samples are cubes with bosses. The specific dimensions are shown in Figure 1(a). The side bosses are rectangles. The side length of the sample is 4l, 0.4m≤l≤0.8m, the rectangular boss is square, the side length is 0.5l, and the spacing is l;

(2) In the process of sample preparation, the anchor rod is inserted, and the whole length is bonded and anchored, and the high temperature and high pressure multi-functional fiber grating sensor is arranged at the same time. The distance between the structure surface and the boss is 0.1m, and the distance between other positions is 0.2m;

(3) Combine the samples into a series of multi-block samples, as shown in Figure 1(b), the number of blocks in the shearing direction is n, 2≤n≤10, the number of blocks in the width direction is 2, and the number of blocks in the height direction is 2;

(4) According to the national standard (GBT 1591-2018), select low-alloy high-strength steel to prepare shear test loading modules that match the series of super-large samples;

(5) Assemble the multi-block sample and the shear test module, and perform the shear test on the large-scale direct shear instrument platform, arrange the acoustic emission probe on the surface of the module, and use the monitored stress, strain, displacement and sound. Judging the force of the boss by launching and other information;

(6) Repeat steps (1)-(5) to carry out the shear test design of the super-large anchoring structure with triangular bosses, wherein the triangular bosses are equilateral triangles with a side length of 0.8l, corresponding to Fig. 2 ( a), 2(b), 2(c).

Further, in the step (1), various composite materials such as magnesia ash can be added to the cement base to improve its strength.

In the step (2), the diameter of the anchor rod is 10-40 mm, and the anchoring diameter is twice the diameter of the anchor rod.

In the step (3), if it is monitored that the boss is deformed or cracked seriously, it is necessary to increase the size of the boss and increase the strength at the same time.

The solution of this embodiment can avoid local damage caused by stress concentration at the end of the super-sized sample, and can ensure the co-stressing of the anchor rod, improve the matching, rationality and scientificity of the test results, and at the same time can solve the problem of super-large size The installation of the sample is difficult, which reduces the safety hazard in the shear test process. The cement-based sample has a simple preparation process, is convenient to use, has a low cost, and has a wide range of applications, providing a scientific basis for the design of super-large-scale tests.

Claims (4)

1. A shear test method for an oversized anchoring structure surface is characterized by comprising the following steps:

(1) manufacturing a plurality of anchor rod-containing cement-based samples according to the indoor sample similarity ratio principle, wherein the samples are cubes containing bosses, the bosses on the side edges are respectively rectangular, the side length of each sample is 4l, l is more than or equal to 0.4m and less than or equal to 0.8m, the rectangular bosses are squares, the side length is 0.5l, and the distance is l;

(2) inserting an anchor rod in the sample preparation process to form full-length bonding type anchoring, and arranging a high-temperature and high-pressure resistant multifunctional fiber grating sensor, wherein the space between the structural surface and the position near the boss is 0.1m, and the spaces between other positions are 0.2 m;

(3) combining the samples into a series of size multi-block samples, wherein the number of blocks in the shearing direction is n, n is more than or equal to 2 and less than or equal to 10, the number of blocks in the width direction is 2, and the number of blocks in the height direction is 2;

(4) selecting low-alloy high-strength steel according to the national standard GBT 1591-2018, and preparing a shear test loading module matched with the series oversized samples;

(5) assembling a plurality of body samples and a shear test module, carrying out a shear test on a large-size direct shear apparatus platform, arranging an acoustic emission probe on the surface of the module, and judging the stress condition of a boss by utilizing the monitored stress, strain, displacement and acoustic emission information;

(6) and (5) repeating the steps (1) to (5) to design the shearing test of the oversized anchoring structure surface containing the triangular boss, wherein the triangular boss is an equilateral triangle, and the side length is 0.8 l.

2. The method for shear testing of oversized anchor structure surface as claimed in claim 1, wherein in step (1), a plurality of composite materials can be added to the cement base to improve the strength.

3. The method for shear testing of oversized anchor structure surface as claimed in claim 1 or 2, wherein in step (2), the diameter of the anchor rod is 10-40 mm, and the anchoring diameter is 2 times of the diameter of the anchor rod.

4. The method for shear testing of oversized anchor structure surface as claimed in claim 1 or 2, wherein in step (3), if deformation or severe rupture of the boss is detected, the size of the boss needs to be increased, and the strength needs to be increased.

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