阅读说明：本技术 一种煤矿巷道岩体累积性损伤的声波法测试系统 (Sound wave method test system for accumulative damage of coal mine tunnel rock mass ) 是由 黎明镜 徐华生 荣传新 陈自由 徐火祥 江维中 余岩 于 2021-09-29 设计创作，主要内容包括：本发明煤矿巷道岩体累积性损伤的声波法测试系统,包括竖向开设在巷道顶板的三个钻孔,三个钻孔成等边三角形布置,在每个钻孔布设测试单元；所述测试单元包括测杆、封孔组件、第一声波换能器、第二声波换能器；自所述测杆底部向顶部依次固定封孔组件、第二声波换能器；所述第一声波换能器与封孔组件固定,第二声波换能器位于测杆顶部；所述测杆为中空结构,所述第一声波换能器和第二声波换能器的数据线从测杆中空结构穿出。设计了煤矿巷道顶部岩体累积性损伤声波法测试的布孔结构,既能实现单孔平透折射波法测试,又能实现多孔穿透直达波法测试,可检测出顶部岩体在不同方向上的裂隙损伤扩展差异性,从而针对性地设计支护方案。(The invention relates to a sonic method testing system for cumulative damage of a coal mine tunnel rock mass, which comprises three drill holes vertically arranged on a tunnel top plate, wherein the three drill holes are arranged in an equilateral triangle, and a testing unit is arranged in each drill hole; the test unit comprises a measuring rod, a hole sealing assembly, a first acoustic wave transducer and a second acoustic wave transducer; the hole sealing assembly and the second sound wave transducer are fixed from the bottom to the top of the measuring rod in sequence; the first acoustic wave transducer is fixed with the hole sealing assembly, and the second acoustic wave transducer is positioned at the top of the measuring rod; the measuring rod is of a hollow structure, and the data lines of the first acoustic wave transducer and the second acoustic wave transducer penetrate out of the hollow structure of the measuring rod. The hole distribution structure for testing the accumulative damage of the rock mass at the top of the coal mine tunnel by the sound wave method is designed, so that the single-hole flat transmitted refracted wave method test and the multi-hole transmitted direct wave method test can be realized, and the crack damage expansion differences of the top rock mass in different directions can be detected, thereby pertinently designing the supporting scheme.)

1. The acoustic wave method testing system for the accumulative damage of the rock mass of the coal mine roadway is characterized by comprising three drill holes (1) vertically arranged on a roadway top plate, wherein the three drill holes (1) are arranged in an equilateral triangle, and a testing unit is arranged in each drill hole (1);

the test unit comprises a measuring rod (6), a hole sealing assembly, a first acoustic wave transducer (8) and a second acoustic wave transducer (5); a hole sealing assembly and a second sound wave transducer (5) are fixed in sequence from the bottom to the top of the measuring rod (6); the first acoustic wave transducer (8) is fixed with the hole sealing assembly, and the second acoustic wave transducer (5) is positioned at the top of the measuring rod (6);

the measuring rod (6) is of a hollow structure, and data wires of the first acoustic wave transducer (8) and the second acoustic wave transducer (5) penetrate out of the hollow structure of the measuring rod (6);

the testing steps are as follows:

(1) following the heading face the 1#, 2# boreholes (1) shown in figure 2 of the roadway roof;

(2) the testing units are respectively installed on the 1# and 2# drilling holes (1), and single-hole flat transmission refraction wave method tests are respectively carried out on the 1# and 2# drilling holes; at the moment, the first acoustic wave transducer (8) and the second acoustic wave transducer (5) in each borehole (1) are used as a transmitter and a receiving respectively;

(3) carrying out cross-hole wave arrival method tests on the 1# and 2# holes, and simultaneously changing the positions of second sound wave transducers (5) in 2 drill holes (1) to enable the second sound wave transducers to be at the same level; two second acoustic transducers (5), one transmitter and one receiver; the two first acoustic wave transducers (8) are in a dormant state;

(4) after the tunnel finishes one new blasting excavation, when the footage meets the distance between holes larger than 1# and 2#, the 3# drilling hole (1) is drilled in the alignment position, the 3# drilling hole (1) is firstly tested by a single-hole penetration refraction wave method, and then the 1# -3 #, 2# -3 #, 1# -2 # cross-hole direct wave tests are respectively carried out; the method is as described in step (3);

(5) according to the change characteristics of the sound velocity, establishing the rock mass damage degree C₁And a rate of decrease in sound speed;

in the formula (1), E is the modulus of elasticity of the rock mass before blasting, v₀The acoustic velocity of the rock mass before blasting is shown as v, and the acoustic velocity of the rock mass after blasting is shown as v, so that the change condition of rock mass damage can be obtained through the rock mass acoustic wave test according to the formula.

2. The sonic testing system for the cumulative damage to the coal mine roadway rock mass as claimed in claim 1, wherein the hole sealing assembly comprises a sleeve (11), a jacking nut (10) and a rubber ring (9); the sleeve (11) is sleeved on the measuring rod and is in damping sliding fit with the measuring rod; the jacking nut (10) is sleeved on the sleeve (11) and fixed with the sleeve (11), and the first acoustic wave transducer (8) is fixed on the sleeve; the rubber ring (9) is sleeved on the upper limit of the sleeve (11) and is positioned between the jacking nut (10) and the first acoustic wave transducer (8); one end of the rubber ring (9) facing the first acoustic wave transducer (8) is fixed, and the other end of the rubber ring can slide up and down; the rubber ring (9) is provided with a middle expansion section, and the jacking nut (10) moves up and down to drive the expansion section to arch or retract.

3. The sonic testing system for cumulative damage to coal mine roadway rock mass of claim 2 wherein the rubber ring (9) includes a multi-section intermediate expansion section.

4. The acoustic wave method testing system for the accumulative damage of the coal mine roadway rock mass according to any one of claims 1 to 3, wherein scales are arranged on the outer wall of the measuring rod (6).

5. The acoustic wave method testing system for the accumulative damage of the coal mine roadway rock mass according to any one of claims 1 to 3, wherein the measuring rod (6) is formed by detachably connecting a plurality of short rods.

6. The acoustic wave method testing system for the accumulative damage of the coal mine roadway rock mass according to any one of claims 1 to 3, wherein the sleeve (11) is provided with a water inlet and a water outlet, the water inlet is positioned outside the drill hole, and the water outlet is positioned in the drill hole.

7. The acoustic wave method testing device for coal mine roadway rock mass accumulative damage according to any one of claims 1 to 3, characterized in that accumulative damage C is calculated along with the result of testing after 6 th to 8 th footage of roadway driving blasting₁。

8. The acoustic wave method testing system for the accumulative damage of the coal mine roadway rock mass according to any one of claims 1 to 3, which is characterized by further comprising a water supply mechanism, an information acquisition module and a calculation module; the water injection mechanism injects water into the drilled hole; the information acquisition module is used for acquiring reporting transducer signals and sending the signals to the calculation module, and the calculation module performs rock mass sound velocity calculation according to the received signals.

Technical Field

The invention relates to the technical field of coal mine roadway engineering support, in particular to a sound wave method testing system for accumulative damage of coal mine roadway rock mass.

Background

A large number of microscopic and macroscopic cracks exist in the rock mass, the cracks are randomly distributed and independently exist in the rock mass, and the strength of the rock in the local range is obviously reduced; the existence of the cracks causes the mechanical properties such as the strength, the elastic modulus and the like of the rock to be anisotropic. When the external force is large enough, the cracks in the rock body are activated, and extension and expansion are generated. The coal mine roadway excavation is a gradual process, because of the special environment of the underground coal mine, the construction is still mostly carried out by adopting a mining method (drilling blasting), and after the drilling blasting excavation is carried out for a section, the supporting is carried out, and the process is carried out repeatedly until the roadway construction is finished. Under the action of explosive load, a great number of micro cracks are formed, expanded and penetrated in the rock, so that the macroscopic mechanical property of the rock is deteriorated, and finally the rock is failed or destroyed, and the process is a continuous damage evolution accumulation process. Under the action of continuous or repeated blasting dynamic load, the damage degree and the damage range are continuously accumulated, increased and enlarged due to irreversibility of damage. When the blasting damage degree of the rock mass is accumulated to the damage threshold value, dynamic instability damage is generated, and finally the safety, the supporting and reinforcing cost of the roadway are directly or indirectly influenced.

At present, a special method for testing the cumulative damage of the coal mine tunnel blasting is not clear, and the current test mainly uses a sound wave method to test the reflected wave speed of the rock mass to reflect the development condition of the internal cracks of the rock mass. After the roadway is excavated, the original rock is disturbed by blasting, new cracks can be generated on the rock body of the cave wall, the original cracks can be extended or expanded, the internal stress of the rock body is reduced, and the corresponding wave velocity is also reduced. From the cave wall to the depth, the stress of the rock body is redistributed, the circumferential stress of the tunnel is increased, the stress concentration and the crack compaction are generated, and the wave velocity increasing area is usually represented; and then the rock body is an original rock area towards the deep position, the rock body is not disturbed, the wave velocity is basically unchanged and is close to the wave velocity of the complete rock mass. The single-hole method is a single-hole flat-transmission refraction wave method, wherein 2 acoustic wave transducers are placed in a drill hole, one acoustic wave transducer is used for transmitting signals, the other acoustic wave transducer is used for receiving signals, and the wave velocity of rock strata at different depths is tested through the change of the distance between the two acoustic wave transducers. The cross-hole method is characterized in that 2 parallel drill holes are arranged, 1 transducer is arranged in each of the two drill holes, the wave velocity of a rock body between the two transducers is tested, and the cross-hole method is a penetrating direct wave method. On the test principle, the cross-hole direct wave method has higher test precision than the single-hole flat transmission refraction wave method.

At present, the coal mine tunnel surrounding rock sound wave method test mainly adopts a single-hole flat transmission refraction wave method test, and the cross-hole method test and the hole distribution structure thereof have various reports in the fresh application of coal mines. From the analysis of the stress mechanism of the roadway, the influence of the blasting disturbance effect is realized, the surrounding rock separation layer crack at the top of the roadway is the most developed, the crack expansion and the accumulative damage are three-dimensional variables, and the damage effect of the rock mass in different directions is difficult to reflect by the conventional single-hole sound wave method test and the double-hole direct wave method test. In addition, the acoustic wave method needs to fill water in the drill hole for coupling test, and tests the top drill vertical hole, so that water sealing is difficult, and poor and inaccurate coupling effect is caused.

For example, the application number 202110005083.3 discloses a surrounding rock loosening ring testing method, which adopts a field testing and indoor testing method to analyze the influence of tunnel construction disturbance on surrounding rocks and quantitatively determine the size and the damage degree of the surrounding rock loosening ring. And (3) measuring the wave velocity of the surrounding rock on site by adopting a sound wave meter, and representing the wave velocity evolution law of the surrounding rock with different damage degrees through an indoor circulating loading and unloading test. The field wave velocity test scheme adopts a single-hole test method to measure the sound wave transmission velocity of rock masses at different depths. The rock damage is described by reducing the rigidity of the rock, so that the wave velocity of the rock and the evolution rule of surrounding rock parameters under different damage degrees are determined. And comparing the wave velocity of the rock mass obtained by field test with a wave velocity evolution curve along with damage determined by an indoor test, and providing a reference basis for the design of the surrounding rock support. The method is good in practicability, not only can provide the range of the loose circle of the surrounding rock excavation, but also can quantitatively evaluate the quality of the rock mass of the loose circle. The testing method adopts a single-hole method, and has the problem of low testing precision.

Disclosure of Invention

The invention aims to solve the technical problem of how to provide a coal mine roadway rock mass accumulative damage sonic method testing system which is high in precision and flexible in testing method.

The invention solves the technical problems through the following technical means:

the acoustic wave method test system for the accumulative damage of the rock mass of the coal mine tunnel comprises three drill holes (1) vertically arranged on a tunnel top plate, wherein the three drill holes (1) are arranged in an equilateral triangle, and a test unit is arranged in each drill hole (1);

the test unit comprises a measuring rod (6), a hole sealing assembly, a first acoustic wave transducer (8) and a second acoustic wave transducer (5); a hole sealing assembly and a second sound wave transducer (5) are fixed in sequence from the bottom to the top of the measuring rod (6); the first acoustic wave transducer (8) is fixed with the hole sealing assembly, and the second acoustic wave transducer (5) is positioned at the top of the measuring rod (6);

the measuring rod (6) is of a hollow structure, and data wires of the first acoustic wave transducer (8) and the second acoustic wave transducer (5) penetrate out of the hollow structure of the measuring rod (6);

the testing steps are as follows:

(1) following the heading face the 1#, 2# boreholes (1) shown in figure 2 of the roadway roof;

(2) the testing units are respectively installed on the 1# and 2# drilling holes (1), and single-hole flat transmission refraction wave method tests are respectively carried out on the 1# and 2# drilling holes; at the moment, the first acoustic wave transducer (8) and the second acoustic wave transducer (5) in each borehole (1) are used as a transmitter and a receiving respectively;

(3) carrying out cross-hole wave arrival method tests on the 1# and 2# holes, and simultaneously changing the positions of second sound wave transducers (5) in 2 drill holes (1) to enable the second sound wave transducers to be at the same level; two second acoustic transducers (5), one transmitter and one receiver; the two first acoustic wave transducers (8) are in a dormant state;

(4) after the tunnel finishes one new blasting excavation, when the footage meets the distance between holes larger than 1# and 2#, the 3# drilling hole (1) is drilled in the alignment position, the 3# drilling hole (1) is firstly tested by a single-hole penetration refraction wave method, and then the 1# -3 #, 2# -3 #, 1# -2 # cross-hole direct wave tests are respectively carried out; the method is as described in step (3);

(5) according to the change characteristics of the sound velocity, establishing the rock mass damage degree C₁And a rate of decrease in sound speed;

in the formula (1), E is the modulus of elasticity of the rock mass before blasting, v⁰The acoustic velocity of the rock mass before blasting is shown as v, and the acoustic velocity of the rock mass after blasting is shown as v, so that the change condition of rock mass damage can be obtained through the rock mass acoustic wave test according to the formula.

The test system for the roadway surrounding rock disturbance cumulative damage sound wave method provided by the invention can realize the test of a single-hole flat transmission refraction wave method and the test of a multi-hole transmission direct wave method through practice tests. The crack damage expansion difference of the top rock mass in different directions can be detected, and therefore a supporting scheme is designed in a targeted mode. The equilateral triangle drilling design is convenient for the calculation of the wave velocity between every two drilling holes.

Further, the hole sealing assembly comprises a sleeve (11), a jacking nut (10) and a rubber ring (9); the jacking nut (10) is sleeved on the sleeve (11) and is in threaded fit with the sleeve (11), and the rubber ring (9) is sleeved on the measuring rod (6) and is located between the jacking nut (10) and the first acoustic wave transducer (8) at the upper limit; one end of the rubber ring (9) facing the first acoustic wave transducer (8) is fixed, and the other end of the rubber ring can slide up and down; the rubber ring (9) is provided with a middle expansion section, and the jacking nut (10) moves up and down to drive the expansion section to arch or retract. A water inlet (11) and a water outlet are formed in the sleeve (11), the water inlet (11) is located below the sealing unit, and the water outlet is located between the first sound wave transducer (8) and the second sound wave transducer (5).

Further, the rubber ring (9) comprises a plurality of middle expansion sections.

Furthermore, the first sound wave transducer (8) and the second sound wave transducer (5) are both circular tube transducers and are sleeved and fixed on the measuring rod (6).

Furthermore, the measuring rod (6) is formed by detachably connecting a plurality of short rods, and the position of the second sound wave transducer (5) in the drill hole can be controlled.

Further, the cumulative damage C is calculated according to the test result after 6 th to 8 th footage of the tunneling blasting₁。

Furthermore, the test system also comprises a water supply mechanism, an information acquisition module and a calculation module; the water injection mechanism is communicated with the water inlet; the information acquisition module is used for acquiring signals of the acoustic wave transducer and sending the signals to the calculation module, and the calculation module performs rock mass sound velocity calculation according to the received signals.

The invention has the advantages that:

the hole distribution structure for testing the cumulative damage of the rock mass at the top of the coal mine tunnel by the sound wave method is designed, so that the single-hole flat transmission refraction wave method test can be realized, the repeated test between every two rock masses can be realized, the sound velocity of the rock mass in the whole three hole areas is comprehensively fed back, and the development condition of rock mass cracks is further reflected. The differences of the test results between every two three drilling holes can reflect the fracture damage differences of the top rock body in different directions, so that a supporting scheme is designed in a targeted manner.

Based on the provided top vertical drilling sound wave method test hole distribution structure, a string type hole sealing structure composed of high-elasticity rubber is designed, and on the premise of meeting the test water sealing, repeated hole sealing among 3 holes can be realized to carry out sound wave method test.

The hole distribution structure tested by the tunnel surrounding rock disturbance cumulative damage sound wave method can realize the test by a single-hole flat penetration refraction wave method and the test by a multi-hole penetration direct wave method through practice and inspection. The crack damage expansion difference of the top rock mass in different directions can be detected, and therefore a supporting scheme is designed in a targeted mode.

Drawings

FIG. 1 is a schematic diagram of an overall structure of a test system combined with a roadway according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a test system for detecting an inclined crack or fault in an embodiment of the invention;

FIG. 3 is a schematic diagram of a drilling and testing unit in the testing system according to an embodiment of the present invention;

FIG. 4 is a schematic top view of a drill hole in the testing system according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The embodiment provides a sound wave method testing arrangement of colliery tunnel rock mass accumulative damage, including the cloth hole structure, as shown in fig. 1, fig. 2 this cloth hole structure comprises three drilling 1, drilling 1 all is located the tunnel roof, and drilling 1 structure is seen from tunnel top plan view, is equilateral triangle shape, and 3 mutual gathering sound wave between drilling 1 pierces through data, realizes striding the hole test, synthesizes the damage of the triangular prism within range rock mass of reflection the cross-section shown in fig. 4. The connecting lines of the 3 drill holes 1 need to avoid the anchor rod 4 and the anchor cable 3 as much as possible, and the test error is reduced.

Fixing a test unit in each borehole 1, wherein the test unit comprises a measuring rod 6, a hole sealing assembly, a first acoustic wave transducer 8 and a second acoustic wave transducer 5 as shown in fig. 3; a hole sealing component and a second sound wave transducer 5 are sequentially arranged from the bottom to the top of the measuring rod 6; the first acoustic wave transducer 8 is fixed on the hole sealing assembly, and the second acoustic wave transducer 5 is positioned at the top of the measuring rod 6.

The measuring rod 6 is of a hollow structure, and the data wire 12 of the first acoustic wave transducer 8 and the second acoustic wave transducer 5 penetrates out of the hollow structure of the measuring rod 6 and is in communication connection with an external signal acquisition module.

In this embodiment, the hole sealing assembly includes a sleeve 11, a jacking nut 10, and a rubber ring 9; the sleeve 11 is provided with a water inlet and a water outlet, the water inlet is positioned outside the drill hole, and the water outlet is positioned in the drill hole. Water can be injected into the drill hole conveniently by forming a water injection channel (not shown) on the wall of the casing 11.

The 11 covers of sleeve pipe are established with the measuring staff damping sliding fit on the measuring staff, the measuring staff 6 of twitching in the testing process of being convenient for adjusts the height of second sound transducer 5, and damping cooperation can realize sealing to a certain extent simultaneously, places water and flows out from between measuring staff 6 and sleeve 11. The damping matching structure is the prior art and is not detailed; the jacking nut 10 is sleeved on the sleeve 11 and is in threaded fit with the sleeve 11, the first acoustic wave transducer 8 is fixed on the sleeve, and the rubber ring 9 is sleeved on the upper limit of the sleeve 11 and is positioned between the jacking nut 10 and the first acoustic wave transducer 8; one end of the rubber ring 9 facing the first acoustic wave transducer 8 is fixed, and the other end can slide up and down; the rubber ring 9 is provided with a middle expansion section, the jacking nut 10 moves up and down to drive the expansion section to arch or retract, and after the expansion section is arched, the expansion section can be tightly abutted to the inner wall of the drill hole 1 to play a hole sealing role. This embodiment rubber circle 9 is high-elastic rubber circle 9, expands the section in the middle of the multistage, can guarantee the hole sealing effect.

In this embodiment, the first sonic transducer 8 and the second sonic transducer 5 are tubular transducers, and are respectively sleeved and fixed on the sleeve 11 and the measuring rod 6. The specific fixing mode is the prior art and is not detailed here.

In order to satisfy the depth adjustment of the second acoustic transducer 5, the measuring rod 6 of the present embodiment has a telescopic structure. For example, a plurality of segments, each 1m long, which can be connected by a threaded joint 7. With the measuring rod 6 formed by a multi-segment screw connection, each time the depth of the second acoustic transducer 5 is adjusted, the test device needs to be pulled out of the casing 11. The outer wall of the measuring rod is provided with scales, and the measuring rod is provided with scales with the precision of millimeter level.

The embodiment also discloses a water supply mechanism, an information acquisition module and a calculation module; the water injection mechanism is communicated with the water inlet 11; the information acquisition module is used for acquiring and declaring signals of the transducer and sending the signals to the calculation module, and the calculation module performs sound velocity calculation according to the received signals.

The specific assembling process comprises the steps of firstly adjusting the measuring rod 6 to a set length outside the hole, respectively fixing the first sound transducer 8 and the second sound transducer at corresponding positions of the measuring rod 6, then penetrating the data line out of the measuring rod 6, and then sleeving the rubber ring 9 and the jacking nut 10. Firstly, the rubber ring 9 is in an arch-closing state, the measuring rod 6 together with other components is sent into the drill hole 1 to a proper position, the jacking nut 10 is screwed to extrude the rubber ring 9, at the moment, the rubber ring 9 starts to be compressed, the expansion section of the middle section starts to arch up until the expansion section is tightly abutted against the inner wall of the drill hole 1, and then hole sealing can be achieved. Then the water inlet is connected with a water source, and the signal line is connected with an acquisition module and other external control devices. In the test process, the measuring rod 6 is drawn, the height of the second acoustic wave transducer 5 is adjusted, the distance between the two acoustic wave transducers is read through the scales of the measuring rod, and later-period calculation is facilitated.

Example 2

Based on the foregoing test system, this embodiment provides a test method, including the following steps:

step 1, drilling 1# and 2# holes on a roadway roof in a manner of following the heading face shown in figure 2;

step 2, respectively installing a test unit for the 1# and 2# drilling holes 1, and respectively carrying out single-hole flat transmission refraction wave method tests on the 1# and 2# holes; at this time, the first sonic transducer 8 and the second sonic transducer 5 in each borehole 1 are one transmitter and one receiver;

step 3, carrying out cross-hole wave arrival method testing on the holes 1# and 2# and simultaneously changing the positions of the second sound wave transducers 5 in the 2 drilled holes 1 to enable the positions to be at the same level; two second acoustic transducers 5, one transmitter and one receiver; the two first acoustic wave transducers 8 are in a non-operating state;

step 4, after the tunnel finishes a new blasting excavation, when the footage meets the distance between holes larger than 1# and 2#, finding the position and drilling the 3# drilling hole 1, firstly carrying out a single-hole penetration refraction wave method test on the 3# drilling hole 1, and then respectively carrying out a 1# -3 #, a 2# -3 #, and a 1# -2 # cross-hole direct wave test; the method is as described in step 3;

step 5, establishing rock mass damage degree C according to the change characteristics of sound velocity₁And a rate of decrease in sound speed;

in the formula (1), E is the modulus of elasticity of the rock mass before blasting, v⁰The acoustic velocity of the rock mass before blasting is shown as v, and the acoustic velocity of the rock mass after blasting is shown as v, so that the change condition of rock mass damage can be obtained through the rock mass acoustic wave test according to the formula. Through engineering test practice, the results of the 6 th to 8 th tests are taken to calculate C₁. Is obviously C₁When 0, the rock mass is undisturbed or extremely disturbed. C₁(0 to 0.09) indicates that the blasting damage is extremely small; c₁The value of (0.10 to 0.34) indicates slight blasting damage; c₁(0.35-0.64) indicates moderate blasting damage; c₁(0.65 to 0.90) indicates a strong blast damage; c₁The values (0.91-1) indicate that the blast damage is strong.

Through the setting of 3 drilling, can measure the different wave velocities of different degree of depth. For example, the second sound transducers of the hole # 1 and the hole # 2 emit and receive at the same time, the wave velocity of one side of the triangle is measured, and by analogy, the wave velocity of the other two sides is measured, and when the depths of the second sound transducers are different, the measured wave velocities are different, then the oblique fault as shown in fig. 2 can be measured according to the different wave velocities (two oblique curves in fig. 2 represent the fault or oblique fracture).

Therefore, the core of the method is that the test of a single hole can be realized, the cross-hole test of double holes can be realized, then the test back and forth between every two holes can be realized, the sound velocity of the rock mass in the whole three hole area is comprehensively fed back, and the development condition of rock mass cracks is reflected.

The different depths of the second acoustic wave transducer in the same drill hole are changed, and the first acoustic wave transducer and the second acoustic wave transducer are subjected to transmitting and receiving, so that the single-hole flat transmission refractometry test can be realized.

The second sound wave transducer is placed at different depths at different positions in different drill holes, and the three drill holes transmit and receive sound wave signals mutually, so that cross-hole testing can be realized.

By combining the test results of the single-hole flat transmission refraction wave method and the cross-hole method, the transmission speed of sound waves at different depths of the rock body in the equilateral triangle area formed by the three drill holes can be effectively reflected.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.