Anchor rod equipment for testing ground stress of underground chamber and experimental method

Abstract

The invention relates to the technical field of ground stress testing, in particular to anchor rod equipment for testing ground stress of an underground chamber, an anchoring body is arranged at the bottom of an anchor hole, and anchoring surfaces are arranged on two opposite sides of the anchoring body so as to directionally extrude surrounding rock outside the chamber through the anchoring surfaces to obtain anchoring stress of the chamber in a set direction; the two ends of the anchor rod are connected with the anchoring body and the load piece through threaded connection structures correspondingly. The loading part is arranged at the hole opening of the anchor hole, the drawing device and the stress meter are arranged between the loading part and the hole opening of the anchor hole, the anchoring faces are arranged on the two sides of the anchoring body, the interaction between the anchor rod and the surrounding rock when the anchor rod is drawn in the rock mass is converted into different drawing forces, and then the ground stress of the surrounding rock of the chamber in a certain direction can be obtained. Therefore, the ground stress direction and size of the surrounding rock of the underground chamber are tested.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ground stress testing, and particularly relates to an anchor rod equipment for testing ground stress of an underground chamber and an experimental method. BACKGROUND

[0002] Due to tectonic stress, the ground stress in mountainous areas is usually three-dimensional. Understanding the direction and size of the ground stress is of great significance for mining resources, tunnel excavation, and construction of underground space such as hydropower stations. The current ground stress testing methods include the air core inclusion method combining field and laboratory, the elastic recovery method taking core for indoor experiment, and the hydraulic fracturing test method, which have the disadvantages of high cost, poor timeliness, complicated process, and high cost.

[0003] Therefore, it is necessary to provide an improved technical solution for the above-mentioned deficiencies of the prior art. SUMMARY

[0004] The present application aims to overcome the deficiencies in the prior art, and provides an anchor rod equipment for testing ground stress of an underground chamber and an experimental method.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions: An anchor rod equipment for testing ground stress of an underground chamber, comprising: An anchoring body, which is arranged at the bottom of an anchor hole, and two anchoring surfaces are arranged on the opposite sides of the anchoring body to directionally extrude the surrounding rock of the chamber through the anchoring surfaces to obtain anchoring stress in a set direction of the chamber; An anchor rod, the two ends of which are connected to the anchoring body and a load piece through a threaded connection structure; The load piece is arranged at the opening of the anchor hole, and a pulling device and a stress meter are arranged between the load piece and the opening of the anchor hole.

[0006] Preferably, the anchor rod is provided with at least one disc corresponding to the inner diameter of the anchor hole.

[0007] Preferably, the anchoring body is in a block or plate structure, and the two anchoring surfaces are respectively arranged on the two sides of the sidewall of the anchoring body corresponding to the anchor hole. The other two sides of the anchoring body are parallel flat surfaces.

[0008] Preferably, the circumscribed circle of the small end of the anchoring body is matched with the cross section of the anchor rod, and the circumscribed circle of the large end of the anchoring body is matched with the hole diameter of the anchor hole.

[0009] Preferably, the inclination angle of the anchoring surface is 2°-30°.

[0010] Preferably, the threaded connection structure comprises a threaded hole and a threaded stud, the threaded hole is arranged at each end of the anchor rod, and the threaded stud is arranged on the anchor body and the load piece respectively.

[0011] An experimental method for testing the ground stress of a underground chamber, the experiment is carried out by using any of the anchor rods, and comprises the following steps: Step S1, a plurality of anchor holes are arranged at a predetermined position in the chamber, the anchor body, the anchor rod and the load piece are assembled and inserted into the anchor hole, and the anchoring surface is installed in the anchor hole along a set direction; Step S2, slurry or resin material is injected into the anchor hole for filling, a pulling device and a stress meter are installed, and then pulling is carried out, the anchor body is damaged to the cofferdam outside the anchor hole and the filling material through the pulling knot; Step S3, parameters of the stress meter are collected during the pulling process, and a force-displacement curve is drawn; The angle of the anchor body is adjusted, and the three-dimensional ground stress distribution of the surrounding rock of the chamber is obtained in combination with the direction of the anchoring surface; Step S4, a plurality of groups of ground stress tests are carried out in the laboratory by changing the confining pressure, the three-dimensional ground stress distribution of the surrounding rock of the chamber measured on site is compared with the ground stress data measured in the laboratory, and the experimental data group consistent with the tensile curve of the on-site test is selected by comparison, so as to obtain the ground stress level of the on-site mine.

[0012] Preferably, in step S3, anchor holes are arranged at the bottom of the chamber, and the z-axis and y-axis ground stress tests of the chamber are carried out by adjusting the angle of the anchor body; Anchor holes are arranged at the side of the chamber, and the x-axis and y-axis ground stress tests of the chamber are carried out by adjusting the angle of the anchor body; The three-dimensional ground stress distribution of the surrounding rock of the chamber is obtained in combination with the stress data of the bottom of the chamber and the side of the chamber.

[0013] Preferably, in step S4, the experimental equipment is used for the ground stress test, and the experimental equipment comprises: A H-shaped main frame, the H-shaped main frame is internally provided with a counterforce frame, one side of the counterforce frame is provided with a rock sample, the rock sample is provided with an anchor hole corresponding to the anchor rod equipment, and the anchor rod equipment is arranged in the anchor hole and passes through the counterforce frame; A confining pressure mechanism, which is arranged between the H-shaped main frame and the rock sample; A stretching mechanism, which is located on the side of the H-shaped main frame away from the rock sample and extends into the H-shaped main frame to be detachably connected with the anchor rod equipment.

[0014] Preferably, the confining pressure mechanism comprises two loading oil cylinders, and the two loading oil cylinders are respectively located on the two sides of the two anchoring surfaces of the anchor rod equipment.

[0015] Beneficial effects: the present technology proposes a two-dimensional anchor rod, anchor surfaces are arranged on both sides of the anchoring body, the interaction between the anchor rod and the surrounding rock during pulling in the rock mass is converted into different pulling forces, and then the ground stress of the surrounding rock of the chamber in a certain direction can be obtained, so that the direction and size of the ground stress of the underground chamber surrounding rock are tested. BRIEF DESCRIPTION OF DRAWINGS

[0016] The drawings accompanying the specification of this application serve to provide further understanding of the present application, the illustrative embodiments of the present application and the description thereof serve to explain the present application, and do not constitute undue limitations on the present application. Among them: Figure 1 The structure diagram of the anchor rod equipment in the specific embodiment provided by the present application; Figure 2 The structure diagram of the anchoring member in the specific embodiment provided by the present application; Figure 3 The structure diagram of the test equipment in the specific embodiment provided by the present application; Figure 4 The anchor hole schematic diagram for testing ground stress in the specific embodiment provided by the present application.

[0017] In the drawings: 1, anchoring body; 2, anchor rod; 3, load member; 4, rock sample; 5, filling material; 6, force transmission plate; 7, stretching mechanism; 8, hui-shaped main frame; 9, stretching screw; 10, holding mechanism; 11, counterforce frame; 12, loading oil cylinder; 1-1, anchor surface; 1-2, stud; 2-1, screw hole; 2-2, disc; DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in the present application belong to the scope of protection of the present application.

[0019] In the description of the present application, the orientations or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application, and do not require the present application to be constructed and operated in a specific orientation, therefore, it cannot be understood as a limitation on the present application. The terms "connected", "connected" used in the present application should be understood in a broad sense, for example, it can be fixed connection, or detachable connection; it can be directly connected, or indirectly connected through intermediate components, and those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0021] like Figures 1-4 As shown, an anchor bolt 2 device for testing the ground stress of an underground cavern includes an anchor body 1, an anchor bolt 2, a pull-out device, and a stress gauge. The anchor body 1 is placed at the bottom of the anchor hole. Anchoring surfaces are provided on opposite sides of the anchor body 1. The anchoring surfaces are flat surfaces. In this application, anchoring surfaces are provided on both sides of the anchor body 1 to form a two-dimensional anchoring structure. The anchoring surfaces are used to obtain the direction and magnitude of the ground stress in the surrounding rock of the cavern. When the anchor bolt 2 is pulled out, the anchoring surfaces 1-1 directionally compress the surrounding rock outside the cavern, thereby obtaining the anchoring stress in the set direction of the cavern through the tensile force. The anchor rod 2 is connected to the anchor body 1 and the load member 3 at both ends by a threaded connection structure. The anchor rod 2 is a metal rod. The load member 3 is located at the opening of the anchor hole. The load member 3 includes a rod part and a disc-shaped structure. The rod part is connected to the anchor rod 2 by a threaded connection structure. The disc-shaped structure is placed on the outer wall of the anchor hole, and the diameter of the disc-shaped structure is larger than that of the rod part. A pull-out device and a stress gauge are provided between the disc-shaped structure and the opening of the anchor hole.

[0022] In this embodiment, the pulling device can be a through-hole jack, and the stress gauge is located between the disc-shaped structure and the pulling device to obtain the corresponding pulling force.

[0023] The anchor rod 2 is provided with at least one disc 2-2 corresponding to the inner diameter of the anchor hole. The disc 2-2 cooperates with the anchor body 1 to keep the anchor body 1 in a centered state, ensuring the quality of anchoring and ground stress testing.

[0024] Furthermore, the anchor body 1 is a two-dimensional structure that forms anchorage only on both sides, thereby allowing the angles of the two anchoring surfaces 1-1 to be adjusted according to actual needs. This enables the testing of ground stress at different angles of the anchor hole, thus obtaining the ground stress in different directions of the chamber. Specifically, the anchor body 1 is a block or plate-like structure, with the two anchoring surfaces 1-1 located on both sides of the sidewall of the corresponding anchor hole of the anchor body 1. The other two sides of the anchor body 1 are parallel flat surfaces, ensuring that during pull-out, the pull-out resistance is mainly formed by the anchoring surfaces 1-1 on both sides, thereby obtaining the corresponding ground stress.

[0025] The circumcircle of the small end of the anchor body 1 is adapted to the cross-section of the anchor rod 2, and the circumcircle of the large end of the anchor body 1 is adapted to the diameter of the anchor hole. The inclination angle of the anchoring surface 1-1 is 2°-30°, preferably 15°.

[0026] The threaded connection structure includes studs 1-2 and threaded holes 2-1. Threaded holes 2-1 are provided at both ends of the anchor rod 2. Corresponding studs 1-2 are provided on the anchor body 1 and the load member 3. The studs 1-2 are integrally formed with the corresponding anchor body 1 and the load member 3 to ensure the stability of the anchor rod 2 during the pull-out process.

[0027] In an optional embodiment, the anchor bolt 2 of this application can be tested on the surrounding rock in the chamber and on the rock sample 4 in the laboratory, respectively. The tensile rate of the anchor bolt 2 in the field should be consistent with the tensile rate used during laboratory calibration. The anchor body 1 is a consumable item and should be replaced before significant deformation occurs to avoid affecting the measurement accuracy.

[0028] Specifically, an experimental method for testing the in-situ stress in underground caverns is provided, comprising the following steps: Step S1: Multiple anchor holes are set at preset positions inside the chamber. Specifically, anchor holes need to be set at the bottom and side walls of the chamber. The depth of the anchor holes is adapted to the anchor rod 2. After assembling the anchor body 1, anchor rod 2 and load member 3, they are inserted into the anchor holes, and the anchoring surface 1-1 is installed in the anchor hole along the set direction. Specifically, the direction of the anchoring surface 1-1 of the anchor body 1 is the direction of the ground stress of the chamber tested in this application.

[0029] In step S2, grout or resin material is injected into the anchor hole as filling material 5, and the anchor rod 2 for in-situ stress testing is fixedly installed in the anchor hole. After installing the pull-out device and stress gauge, pull-out is performed. Through pull-out, the anchor body 1 destroys the cofferdam and filling material 5 outside the anchor hole. Utilizing the interaction between the anchor rod 2 and the surrounding rock when pulled out in the rock mass, different pull-out forces are generated, and thus the in-situ stress of the surrounding rock in a certain direction of the chamber can be obtained.

[0030] Step S3: Start the pulling device. The pulling device applies force between the load member 3 and the orifice, thereby causing the anchor body 1 to expand and destroy the surrounding grout and surrounding rock. During the pulling process, the parameters of the stress gauge are collected, and the force and displacement change curves are plotted. The confining pressure is reflected in the force and displacement curves of the anchor 2 pulling equipment test.

[0031] In this embodiment, anchor holes are drilled at the bottom of the chamber, and the stress on the z-axis and y-axis of the chamber is tested by adjusting the angle of the anchor body 1; anchor holes are drilled on the side of the chamber, and the stress on the x-axis and y-axis of the chamber is tested by adjusting the angle of the anchor body 1.

[0032] By adjusting the angle of anchor body 1 and combining it with the direction of anchor surface 1-1, the three-dimensional geostress distribution of the surrounding rock of the chamber is obtained. By combining the stress data of the bottom and sides of the chamber, the three-dimensional geostress distribution of the surrounding rock of the chamber is obtained.

[0033] Specifically, the direction of in-situ stress during testing is as follows: Figure 3As shown, by drilling a hole h-1 on the side of the chamber and using the anchor rod 2 in this technology to measure the in-situ stress, and adjusting the direction of the anchor body 1, the in-situ stress along the vertical z-axis and the axial y-axis of the chamber can be obtained. Drilling a hole v-1 at the bottom of the chamber allows for the acquisition of the in-situ stress along the x-axis and y-axis. Combining these two sets of data, the three-dimensional in-situ stress distribution of the surrounding rock of the chamber can be obtained.

[0034] Step S4: In the laboratory, multiple sets of in-situ stress tests are conducted by changing the confining pressure. Before calibrating the in-situ stress level, a rock mass with similar mechanical parameters to the mine's surrounding rock is prepared as rock sample 4. Mortar, gypsum, and other materials are mixed to ensure that its elastic modulus, Poisson's ratio, compressive strength, and tensile strength are consistent with the surrounding rock at the site. This sample is then fabricated into a cubic specimen with a pre-drilled borehole. To maintain consistency with the field conditions, anchor rods 2 for in-situ stress testing are placed in the borehole. Experimental data are obtained through tensioning in the laboratory. The three-dimensional in-situ stress distribution of the surrounding rock in the chamber is compared with the in-situ stress data. The experimental data set consistent with the tensile curve from the field test is selected to determine the in-situ mine stress level.

[0035] In this embodiment, the experimental instrument is used to conduct experiments with different rock parameters, different anchor bolt 2 sizes, and different confining pressures, which can provide a basic database for the method of using anchor bolt 2 to test the ground stress level.

[0036] Furthermore, step S4 requires a test device for numerical calibration, which is used to test the ground stress. The test device includes a U-shaped main frame 8, a confining pressure mechanism, and a tensioning mechanism 7. The U-shaped main frame 8 is welded from square steel, I-beams, or channel steel. A reaction frame 11 is provided inside the U-shaped main frame 8. A rock sample 4 is provided on one side of the reaction frame 11, and the rock sample 4 abuts against the reaction frame 11. The rock sample 4 has anchor holes corresponding to the anchor rod 2. After the anchor rod 2 is installed in the anchor hole, it passes through the reaction frame 11. The confining pressure mechanism is set between the U-shaped main frame 8 and the rock sample 4 to simulate the surrounding rock pressure. The tensioning mechanism 7 is located on the side of the U-shaped main frame 8 away from the rock sample 4, and extends into the U-shaped main frame 8 and is detachably connected to the anchor rod 2. Tensioning is then performed through the tensioning mechanism 7, which can be a hydraulic cylinder.

[0037] The confining pressure mechanism includes two loading cylinders 12, which are located on both sides of the two anchoring surfaces 1-1 corresponding to the anchor bolt 2. Depending on the actual needs, a loading cylinder 12 can also be added to the end of the rock sample 4 away from the reaction frame 11, so that the surrounding rock in the device is under a more realistic mining stress state. A force transmission plate 6 is provided between the loading cylinder 12 and the rock sample 4.

[0038] In this embodiment, the tensioning mechanism 7 is provided with a tensioning screw 9 at its end. The tensioning screw 9 is threadedly connected to a clamping mechanism 10. The clamping mechanism 10 is a cover-shaped structure corresponding to the disc-shaped mechanism at the end of the load member 3. The middle part of the cover is hollow corresponding to the rod part. The clamping mechanism 10 is threadedly connected to the end of the tensioning screw 9 to form a connection.

[0039] This application utilizes anchor bolt 2 to test the level and direction of ground stress, which is an economical and rapid method for testing ground stress. The anchor hole setup only requires drilling a small hole of approximately 30 mm. This drilling technology is mature in the underground engineering field and offers the advantage of rapid installation. Furthermore, this technology can be carried out simultaneously with the excavation of underground engineering projects, and the on-site pull-out equipment for anchor bolt 2 has been significantly reduced in size.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. An anchor bolt device for testing ground stress in underground chambers, characterized in that, Comprising: An anchor solid, which is placed at the bottom of the anchor hole. On two opposite sides of the anchor solid, there are anchor surfaces for obtaining the anchor stress in the set direction of the chamber by directionally extruding the surrounding rock outside the chamber through the anchor surfaces; A bolt, with both ends of the bolt connected to the anchor solid and the load member respectively through threaded connection structures; The load member is arranged at the mouth of the anchor hole. Between the load member and the mouth of the anchor hole, there is a pulling device and a stress gauge.

2. The anchor bolt equipment for testing the ground stress of an underground tunnel according to claim 1, characterized in that, There is at least one disc corresponding to the inner diameter of the anchor hole on the bolt.

3. The anchor bolt equipment for testing the ground stress of an underground tunnel according to claim 1, characterized in that, The anchor solid is of a block or plate structure. The two anchor surfaces are respectively located on both sides of the side wall of the anchor hole corresponding to the anchor solid; The other two sides of the anchor solid are parallel flat surfaces.

4. The anchor bolt equipment for testing the ground stress of an underground chamber according to claim 3, characterized in that, The circumcircle of the small end of the anchor solid is adapted to the cross-section of the bolt, and the circumcircle of the large end of the anchor solid is adapted to the aperture of the anchor hole.

5. The anchor bolt equipment for testing the ground stress of an underground chamber according to claim 3, characterized in that, The inclination angle of the anchor surface is 2° - 30°.

6. The anchor bolt equipment for testing the ground stress of an underground tunnel according to claim 1, characterized in that, The threaded connection structure includes studs and threaded holes. Threaded holes are respectively arranged at both ends of the bolt, and corresponding studs are respectively arranged on the anchor solid and the load member.

7. An experimental method for testing the ground stress in an underground cavern, wherein the experiment is conducted using the anchor bolt equipment described in any one of claims 1-6, characterized in that, Including the following steps: Step S1, set multiple anchor holes at the preset positions inside the chamber. Assemble the anchor solid, bolt and load member and insert them into the anchor holes, and install the anchor surfaces in the anchor holes along the set direction; Step S2, inject slurry or resin material into the anchor holes for filling. After installing the pulling device and the stress gauge, conduct pulling. Through the pulling knot, the anchor solid destroys the external cofferdam and filling material of the anchor hole; Step S3, collect the parameters of the stress gauge during the pulling process and draw the force-displacement change curve; Adjust the angle of the anchor solid, and obtain the three-dimensional in-situ stress distribution of the chamber surrounding rock in combination with the direction of the anchor surface; Step S4, conduct multiple groups of in-situ stress tests in the laboratory by changing the confining pressure. Compare the three-dimensional in-situ stress distribution of the chamber surrounding rock measured on-site with the in-situ stress data measured in the laboratory, and select the experimental data group consistent with the tensile curve measured on-site to obtain the in-situ stress level of the on-site mine.

8. The experimental method for testing the in-situ stress of an underground tunnel according to claim 7, characterized in that, In step S3, drill anchor holes at the bottom of the chamber, and conduct the in-situ stress tests of the z-axis and y-axis of the chamber by adjusting the angle of the anchor solid; Drill anchor holes on the side of the chamber, and conduct the in-situ stress tests of the x-axis and y-axis of the chamber by adjusting the angle of the anchor solid; Obtain the three-dimensional in-situ stress distribution of the chamber surrounding rock by combining the stress data at the bottom and on the side of the chamber.

9. The experimental method for testing the in-situ stress of an underground tunnel according to claim 7, characterized in that, In step S4, use experimental equipment to conduct in-situ stress tests. The experimental equipment includes: A square main frame. Inside the square main frame, there is a reaction frame. On one side of the reaction frame, there is a rock sample. There is an anchor hole corresponding to the bolt equipment on the rock sample. After the bolt equipment is inserted into the anchor hole, it passes through the reaction frame; A confining pressure mechanism, which is arranged between the square main frame and the rock sample; A tensile mechanism, which is located on the side of the square main frame away from the rock sample and extends into the square main frame and is detachably connected to the bolt equipment.

10. The experimental method for testing the in-situ stress of an underground tunnel according to claim 9, characterized in that, The confining pressure mechanism includes two loading cylinders, and the two loading cylinders are respectively located on both sides of the bolt equipment corresponding to the two anchor surfaces.

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