Mechanical property testing device and experimental method for anchor rod cable-steel belt combined structure

Abstract

The invention discloses a mechanical property testing device and an experimental method.The testing device comprises two rectangular cage type steel frames which are arranged in parallel in a spaced mode, the upper portions of the two steel frames are connected through a distance rod, the middle portions of the two steel frames are connected through a steel belt, and frame cross beams are arranged in the middle portions of the steel frames; a concrete block is placed in the upper-layer space, a prefabricated drill hole is formed in the center of the concrete block, an anchor rod cable is arranged in the drill hole in a penetrating mode, the upper end of the anchor rod cable is exposed out of the drill hole, an upper supporting plate, a center penetrating type pressure sensor and a lock are sequentially installed on the anchor rod cable, and the lower end of the anchor rod cable is exposed out of the drill hole; and the steel belt, the lower supporting plate and the lockset are sequentially mounted on the anchor rod cable. The testing device can accurately simulate the stress state of the steel belt in a roadway (tunnel) support, the mechanical property of the steel belt can be obtained under the condition that basic parameters of the anchor rod cable are regulated and controlled, parameter matching of the anchor rod cable and the steel belt is achieved, the effect of mutual cooperative work is achieved, and the mechanical properties of the anchor rod cable and the steel belt are exerted.

Description

Technical Field

[0001] The invention relates to an anchor / cable-steel belt combined structure testing technology, and in particular to a mechanical property testing device and an experimental method for an anchor cable-steel belt combined structure, and belongs to the field of lane (tunnel) surrounding rock support structure testing. Background Art

[0002] The excavation and unloading of rock mass in underground engineering causes the surrounding rock to expand and deform toward the tunnel space under the action of complex ground stress, forming a broken zone. The support of the broken surrounding rock on the tunnel surface is an important measure to ensure the safety of tunnel use. With the continuous increase in mining depth and scope, the stress of tunnel surrounding rock is getting greater and greater, the surrounding rock conditions are becoming more and more complex, and the difficulty of tunnel support has increased significantly. At present, anchor support technology is widely used in the field of tunnel surrounding rock support, and has become one of the effective ways to solve the difficulties in supporting the surrounding rock of deep tunnels.

[0003] With the continuous advancement of anchor support technology, the use of composite components such as steel belts and steel joists in conjunction with high-strength, high-preload anchor cables to form a high-preload strong anchor support system can significantly improve the support effect of lanes (tunnels). Composite components such as steel belts and steel joists cooperate with metal mesh and anchor cable support structures to achieve the overall support of the broken surrounding rock surface of the lane (tunnel) from "points" to "lines" and then to "surfaces", which is an important guarantee for ensuring the stability of the surrounding rock of the lane. Among them, steel belts or steel joists are important components of the "lines" in the system and play an extremely important role. First, the steel belt and steel support beam can transfer and diffuse the high prestress of the anchor cable to a wider range along the longitudinal and transverse directions of the surrounding rock surface, thereby improving the active support range of the high prestressed anchor support system; secondly, the steel belt and steel support beam can improve the strength and rigidity of the metal mesh surface protection. The metal mesh is a flexible passive surface protection component with low bending stiffness. The steel belt and steel support beam increase the bending stiffness of the steel mesh, improve the metal mesh surface protection ability, and reduce the deformation of the surrounding rock surface; at the same time, the steel belt can reduce the stress concentration in the stress-bearing area of ​​the tray at the tail of the anchor to a certain extent, which is beneficial to the application of prestress of the anchor cable and reduces the loss of prestress; finally, the steel belt and steel support beam can connect multiple groups of anchor systems in series, and together with the surface protection metal mesh, form a joint support system to form an overall support of "point-line-surface" for the surrounding rock, dividing the surrounding rock surface into several smaller support grids, each of which is independent of each other. Even if one of the grids fails, it will not affect the integrity of the entire support system. Therefore, it can be seen that composite components such as steel belts and steel support beams play a key role in the tunnel surrounding rock anchoring support system, and their mechanical properties are crucial to the tunnel surrounding rock support design.

[0004] The mechanical properties of composite components such as steel strips and steel support beams depend on the basic parameters of anchor cables (prestress, support plate type, spacing, etc.). Independent design or poor combination of the two will lead to shear breakage of the anchor tail, suction of the support plate into the steel strip, tearing of the steel strip along the hole, excessive deformation of the steel strip, and other types of damage, which pose a great threat to the safe operation and maintenance of the lane (tunnel). The existing testing technology is relatively mature for tests such as anchor cable pull-out, shear performance, and mechanical parameters of steel strips, but there are relatively few mechanical property test analyses and test devices for anchor / cable-steel strip composite structures. The existing testing technology cannot truly reflect the stress state of the steel strip in the surrounding rock support of the lane (tunnel), and cannot realize the sensitivity experiment of the influence of the basic parameters of the anchor / cable on the mechanical properties of the steel strip. Summary of the invention

[0005] In view of the above situation, in order to provide parameter basis for refined design of surrounding rock support of roadway (tunnel), the present invention provides a mechanical performance testing device and experimental method for an anchor rod / cable-steel belt combined structure.

[0006] The technical solution of the present invention is as follows: A mechanical property testing device for an anchor cable-steel belt combined structure comprises an experimental system, wherein the experimental system comprises two parallel and spaced rectangular cage steel frames, the upper parts of the two steel frames are connected by a distance rod, the middle parts of the two steel frames are connected by a steel belt, a steel frame crossbeam is arranged in the middle of the steel frame, the crossbeam divides the interior of the steel frame into an upper and lower space, a concrete block is placed in the upper space, a prefabricated drilled hole penetrating up and down is arranged in the center of the concrete block in the vertical direction, an anchor cable is penetrated in the drilled hole, the upper end of the anchor cable is exposed from the drilled hole, an upper support plate, a through-type pressure sensor and a lock are sequentially installed on the anchor cable, and the upper support plate contacts the top surface of the concrete block; the lower end of the anchor cable is exposed from the drilled hole, and the steel belt, the lower support plate and the lock are sequentially installed on the anchor cable, and the steel belt contacts the bottom surface of the concrete block.

[0007] Furthermore, each of the steel frames includes four steel frame columns, the two steel frame columns located on the inner side of the steel frame are called inner columns, and the height of the inner columns is higher than the top surface of the steel frame; a plurality of holes are opened at equal distances on the distance rod, and the shape of the holes matches the horizontal cross-section of the inner columns, and the two ends of the distance rod are respectively mounted on the top ends of the inner columns of the two steel frames through the holes, and the upper parts of the two steel frames are connected by two distance rods parallel to each other and spaced apart.

[0008] Furthermore, the testing device also includes a loading system, which includes a reaction frame, and a jack system is arranged on the crossbeam of the reaction frame, the output shaft end of the jack system is vertically downward, and an arc-shaped loading plate is hinged at the output shaft end of the jack system, and the arc-shaped loading plate is located directly above the steel belt.

[0009] Furthermore, a steering wheel is installed at the bottom of the steel frame.

[0010] Furthermore, an angle steel is fixedly arranged on the inner side of the middle cross beam of the steel frame, and the concrete block is placed on the angle steel.

[0011] Before the test, it is necessary to prefabricate concrete blocks that match the upper space of the cage steel frame. Anchor holes are prefabricated in the middle of the concrete blocks. After reaching the test strength, they are hoisted into the upper space of the cage steel frame. The bottom of the concrete block is placed on the support formed by the straightened angle edge of the middle angle steel.

[0012] According to the design requirements of the experimental parameters, two distance rods are used, and holes with different spacings on the distance rods are selected, and they are respectively inserted into the columns protruding from the top-level crossbeams. This method is used to connect the two cage-type steel frames longitudinally.

[0013] Insert the anchor rod or anchor cable matching the steel belt to be tested into the anchoring drill hole of the concrete block respectively, insert the notch opened on the steel belt to be tested into the anchor rod or anchor cable rod body from the lower space of the cage steel frame, and install the support plate and nut or lock one by one. Install the support plate, through-core pressure sensor and nut or lock one by one on the upper part of the concrete block and lock it. According to the experimental parameters, the anchor rod or anchor cable can be prestressed in advance by using a torque wrench or anchor cable tensioning machine and then locked. Push the installed experimental system into the loading system, start the jack through the computer control system, pressurize the steel belt through the arc loading plate and collect relevant data in real time, so as to test the bearing capacity of the anchor rod / cable-steel belt combination structure.

[0014] During the test, the through-type pressure sensor can be used to obtain real-time data on the axial force of the anchor cable, and the feedback information obtained by the sensor of the jack system can be used to obtain information such as the bearing capacity and displacement of the steel belt, as well as the anchor / cable and steel belt failure type and the coupling relationship of mechanical parameters. The test device can also be used to test the mechanical properties and failure forms of the anchor / cable-steel belt combination structure under different spans, eccentricities, steel belt types, anchor / cable prestressing and other factors, which can provide parameter basis for the refined design of surrounding rock support of lanes (tunnels), which is conducive to ensuring the safe operation and maintenance of lanes (tunnels).

[0015] Beneficial effects: The test device can accurately simulate the stress state of the steel belt in the roadway (tunnel) support, and can obtain the mechanical properties of the steel belt under the control of the basic parameters of the anchor cable (prestress, support plate type, spacing, etc.), realize the matching of anchor cable and steel belt parameters, achieve the effect of mutual cooperation, and give full play to their respective mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a stereoscopic diagram of the mechanical properties experimental system of the anchor cable-steel belt combined structure of the present invention.

[0017] Figure 2 It is a partial front view of the mechanical properties experimental device of the anchor cable-steel belt combined structure of the present invention.

[0018] Figure 3 This is the AA cross-sectional view of the mechanical properties experimental device of the anchor cable-steel belt combined structure of the present invention.

[0019] Figure 4 It is a three-dimensional diagram of the cage-type steel frame in the experimental device of the present invention.

[0020] Figure 5 Schematic diagram of the concrete block in the experimental device of the present invention.

[0021] Figure 6 Schematic diagram of the distance rod in the experimental device of the present invention.

[0022] Figure 7 Schematic diagram of the steel strip under test in the experimental device of the present invention.

[0023] In the figure: 1-reaction frame column; 2-reaction frame beam; 3-through-type pressure sensor; 4-support plate; 5-spacer; 6-concrete block; 7-arc loading plate; 8-hydraulic jack; 9-cage steel frame; 10-measured steel belt; 11-anchor cable lock; 12-anchor cable; 13-steering wheel; 14-steel frame column; 15-steel frame beam; 16-angle steel; 17-prefabricated drilled hole; 18-square hole; 19-slot. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings.

[0025] A mechanical properties testing device for an anchor cable-steel belt combined structure, the basic components of which include a loading system and an experimental system, such as Figure 1 shown.

[0026] The loading system is composed of a reaction frame column 1, a reaction frame beam 2, an arc-shaped loading plate 7, a hydraulic jack 8, a computer control system, etc. The reaction frame column 1 and the reaction frame beam 2 are welded from high-strength steel plates, and they are connected to each other with high-strength bolts to form a portal reaction frame in the loading system; the bottom of the hydraulic jack 8 is fixed to the middle position of the reaction frame beam 2 by an extended bolt; in order to accurately simulate the load type of the steel belt, the loading plate is set to be arc-shaped, and the arc-shaped loading plate 7 and the top of the jack 8 are hingedly connected to each other by pins. The reaction frame column 1, the reaction frame beam 2, the hydraulic jack 8, the arc-shaped loading plate 7, etc. are connected to each other and cooperate with other monitoring sensors to assemble into an experimental loading system, which is controlled by a computer and can realize the control of loading mode, loading speed, etc., and can obtain the loading reaction force value and displacement value, etc.

[0027] The experimental system consists of a through-type pressure sensor 3, a support plate 4, a distance rod 5, a concrete block 6, a cage steel frame 9, a steel belt to be tested 10, an anchor cable lock 11, an anchor cable 12, a steering wheel 13, etc. The specific structure is as follows: Figures 2 to 7 The through-type pressure sensor is electrically connected to the computer control system.

[0028] In order to accurately simulate the working state of a single-span anchor / cable-steel belt combined structure, several square steel tubes are welded together to form a rectangular cage steel frame 9, of which four relatively long square steel tubes are steel frame columns 14, and short square steel tubes are welded together in the horizontal direction at the bottom, middle and top as steel frame crossbeams 15 to form a cage steel frame 9 with two spaces above and below. Among them, steering wheels 13 are respectively installed under the four steel frame columns at the bottom of the cage steel frame to facilitate the movement of the steel frame; right-angle angle steels 16 are welded on the inner tube wall of the square steel tube crossbeam 15 at two relative positions in the middle of the cage steel frame, and one right-angle side of the angle steel fits the tube wall, and the other right-angle side extends into the steel frame to form a support. The top surface of the horizontal right-angled side of the angle steel forming the support must be flush with the bottom surface of the middle crossbeam to ensure that the steel belt installed at the bottom of the concrete block is level and not affected by the crossbeam; the two cage-type steel frame columns (inner columns) along the direction of the welded angle steel 16 protrude from the top surface of the steel frame crossbeam by about 10 cm and are used to connect the distance rods 5. The top surfaces of the remaining steel frame columns are flush with the top surface of the upper crossbeam of the steel frame.

[0029] The distance rod 5 is made of a full-length high-strength square steel tube, and its cross-sectional size is larger than the square steel tube used in the cage-type steel frame. According to experimental requirements, square holes 18 are opened at equal distances along the length direction of the distance rod 5. The size of the holes matches the cross-sectional area of ​​the square steel tube of the cage-type steel frame column, so that the steel frame column 14 protruding from the crossbeam can penetrate the square holes 18 on the distance rod 5.

[0030] During the experiment, the two cage-type steel frames are connected by using the square holes opened on the distance rod 5. The spacing of the square holes 18 is used to adjust the spacing of the anchor cables, so that the bearing capacity test of the steel belt under different anchor cable spacings can be realized. In addition, the distance rod 5 can balance the reaction force generated on the top of the steel frame during the loading experiment, so as to maintain the stability of the operation of the entire experimental device.

[0031] Insert the anchor rod or anchor cable 12 matching the steel belt 10 to be tested into the anchor hole of the concrete block 6 respectively, insert the anchor rod or anchor cable rod body 12 through the notch 19 opened on the steel belt 10 to be tested from the lower space of the cage steel frame 9, and install the support plate 4 and the nut or lock 11 one by one. Install the support plate 4, the through-type pressure sensor 3 and the nut or lock 11 one by one on the upper part of the concrete block, and lock them. According to the experimental parameter requirements, the anchor rod or anchor cable can be prestressed in advance with a torque wrench or an anchor cable tensioning machine and then locked. Push the installed experimental device into the experimental loading system to test the bearing capacity of the anchor rod / cable-steel belt combination structure.

[0032] During the test, the information fed back by the sensors can be used to obtain data such as the bearing capacity of the steel belt, the displacement of the steel belt, and the axial force of the anchor cable, and the coupling relationship between the anchor / cable and steel belt failure types and mechanical parameters. The experimental device can also be used to test the mechanical properties and failure forms of the anchor / cable-steel belt combination structure under different spans, eccentricities, steel belt types, anchor / cable prestressing and other factors, which can provide parameter basis for the refined design of surrounding rock support for lanes (tunnels), which is conducive to ensuring the safe operation and maintenance of lanes (tunnels).

[0033] Single span φ The experimental method for testing the mechanical properties of the anchor cable-steel belt combined structure of the present invention is introduced by taking a 17.8 mm anchor cable-steel belt combined structure as an example.

[0034] The experimental method of the present invention is that, in the first step, two concrete test blocks matching the size of the cage steel frame 9 are prefabricated in advance. In the example, the size of the concrete test block 6 is 350mm×350mm×400mm, and a through prefabricated drill hole 17 is set on the central axis of the concrete block. The hole diameter is 28mm, and the design value of the concrete block strength is 30MPa to simulate the tunnel roof rock mass.

[0035] In the second step, the concrete block 6 reaching the designed strength is hoisted into the upper layer of the cage steel frame 9, ensuring that the bottom of the concrete block 6 is placed on the support formed by the welded angle steel 16, and the drilling direction 17 is vertical; the same operation is performed to set up two cage steel frames.

[0036] The third step is to cut two sections of anchor cables with a diameter of 17.8 mm and a length of 800 mm to 1000 mm according to the anchor cable-steel belt combination structure to be tested, in which the span is 1200 mm and the prestress of the anchor cables is 100 kN. Insert the anchor cable rod body 12 into the prefabricated drilled hole 17 in the concrete block 6, and install the support plate 4, the through-type pressure sensor 3, and the lock 11 on the upper surface of the concrete block 6 in sequence. The lock is not locked and serves as a temporary fix. Insert the steel belt 10, the support plate 4 and the anchor cable lock 11 one by one through the steel belt notch 19 on the anchor cable rod body exposed at the bottom of the concrete block 6. In the same way, repeat the same operation on another cage-type steel frame concrete block, and use the notch at the other end of the steel belt to be tested to connect the two anchor cables to form an anchor cable-steel belt combination structure.

[0037] The fourth step is to use the anchor tensioning equipment to tension the anchor cable 12 along the anchor cable rod body extending from the upper part of the concrete block 6, apply 100kN prestress, and lock it with the lock 11; according to the span of the anchor cable-steel belt combined structure, measure the horizontal distance of the protruding column of the cage steel frame, open a square hole 18 on the high-strength distance bar 5, and set multiple square holes 18 at intervals of 300mm along the length direction of the distance bar 5. Use the square holes 18 of the distance bar that match the spacing between the two cage steel frame columns to insert the protruding columns respectively, so that the distance bar 5 stably connects the two cage steel frames 9 and limits the span distance between the two anchor rods.

[0038] The fifth step is to push the experimental device into the loading device so that the arc loading plate 7 faces the steel belt 10 to be tested, load the anchor cable-steel belt combination structure to be tested, and obtain the loading reaction force, steel belt displacement, and anchor cable axial force change value.

[0039] The advantages of the present invention are that by adjusting the distance between the holes on the distance rod 5, the mechanical response of the anchor cable-steel belt combination structure under different span conditions can be achieved; by adjusting the position of the mobile test device, the arc loading plate 7 can load the steel belt 10 under different eccentricities; by applying different anchor cable prestresses through the anchor cable tensioning equipment, the bearing capacity of the steel belt 10 under different anchor cable support plate constraint strengths can be tested.

[0040] The device can accurately simulate the actual stress state of the anchor cable-steel belt combination structure. It has a simple structure and is easy to operate. It can also test the mechanical properties and failure mode of the anchor / cable-steel belt combination structure under conditions of span, eccentricity, steel belt type, anchor / cable prestress and other factors. It can provide parameter basis for the refined design of surrounding rock support of lanes (tunnels), which is beneficial to ensure the safe operation and maintenance of lanes (tunnels).

[0041] In summary, the present invention provides a mechanical performance testing device and experimental method for an anchor / cable-steel belt combined structure, which provides parameter basis for the refined design of surrounding rock support for lanes (tunnels). The testing device includes columns, beams, hydraulic jacks, arc loading plates, concrete blocks, pressure sensors, distance rods, anchors / cables, tested steel belts, etc. The columns, beams, hydraulic jacks, arc loading plates, etc. are connected by bolts and cooperated with other monitoring sensors to assemble into an experimental loading system. In order to simulate the working state of the combined components in the anchor cable support system for the surrounding rock of lanes (tunnels), square steel and angle steel are welded to each other to form two double-layer cage steel frames. Four steering wheels are arranged at the bottom of each cage steel frame for easy movement. Two square steel columns of each cage steel frame are higher than the plane of the upper beam, and the top surfaces of the other two columns are flush with the upper plane. The distance rod is a full-length high-strength square steel tube. Square holes are opened on the distance rod at a certain interval. The size of the square hole is consistent with the cross-sectional size of the cage steel frame column. The square column of the cage steel frame passes through the hole above the distance rod to connect two symmetrically arranged cage steel frames. The prefabricated concrete block with a drilled hole is hoisted into the upper layer of the cage steel frame, and the anchor rod or anchor cable is inserted into the prefabricated concrete drilled hole. The anchor rod / cable-steel belt combination structure is installed on the lower layer of the two cage steel frames respectively. The structural device is moved into the loading system, and the loading system is started so that the arc loading plate loads different positions of the steel belt to test the mechanical properties of the anchor rod / cable-steel belt combination structure. During the test, other sensors can be used to feedback information to obtain data such as the bearing capacity of the steel belt, the displacement of the steel belt, and the axial force of the anchor rod cable, and the failure type and mechanical parameter coupling relationship of the anchor rod / cable and steel belt can be obtained. Through this test device, the mechanical properties and failure forms of the anchor rod / cable-steel belt combination structure under the conditions of span, eccentricity, steel belt type, anchor rod / cable prestress and other factors can also be tested.

Claims

1. A mechanical properties testing device for an anchor cable-steel belt combined structure, characterized in that: The experimental system comprises two parallel and spaced rectangular cage steel frames, the upper parts of the two steel frames are connected by a distance rod, the middle parts of the two steel frames are connected by a steel belt, a steel frame crossbeam is arranged in the middle of the steel frame, the crossbeam divides the interior of the steel frame into an upper and lower space, a concrete block is placed in the upper space, a prefabricated drilled hole is arranged vertically in the center of the concrete block, an anchor cable is passed through the drilled hole, the upper end of the anchor cable is exposed from the drilled hole, an upper support plate, a through-type pressure sensor and a lock are sequentially installed on the anchor cable, and the upper support plate contacts the top surface of the concrete block; the lower end of the anchor cable is exposed from the drilled hole, and the steel belt, the lower support plate and the lock are sequentially installed on the anchor cable, and the steel belt contacts the bottom surface of the concrete block.

2. The mechanical properties testing device of the anchor cable-steel belt combined structure according to claim 1 is characterized in that: Each of the steel frames includes four steel frame columns, two steel frame columns located on the inner side of the steel frame are called inner columns, and the height of the inner columns is higher than the top surface of the steel frame; a plurality of holes are opened at equal distances on the distance rod, and the shape of the holes matches the horizontal cross-section of the inner columns, and the two ends of the distance rod are respectively mounted on the top ends of the inner columns of the two steel frames through the holes, and the upper parts of the two steel frames are connected by two distance rods parallel to each other and spaced apart.

3. The mechanical properties testing device of the anchor cable-steel belt combined structure according to claim 1 is characterized in that: The testing device also includes a loading system, which includes a reaction frame. A jack system is arranged on the crossbeam of the reaction frame. The output shaft end of the jack system is vertically downward. An arc-shaped loading plate is hinged at the end of the output shaft of the jack system, and the arc-shaped loading plate is located directly above the steel belt.

4. The mechanical properties testing device of the anchor cable-steel belt combined structure according to claim 1, characterized in that: A steering wheel is also installed at the bottom of the steel frame.

5. The mechanical properties testing device of the anchor cable-steel belt combined structure according to claim 1, characterized in that: An angle steel is fixedly arranged on the inner side of the middle cross beam of the steel frame, and the concrete block is placed on the angle steel.

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