Ground stress testing method based on sound wave velocity

Abstract

The invention belongs to the technical field of geological exploration equipment, and provides a ground stress test method based on acoustic wave velocities, which comprises the following steps: arranging a vertical hole and two horizontal holes in the same section of a test hole, and respectively testing the acoustic wave velocities of the vertical hole and the two horizontal holes; testing sound wave velocities at different distances from the bottom of the vertical hole to the bottoms of the two horizontal holes to the hole opening direction, testing sound wave velocities at different distances from the bottoms of the two horizontal holes to the bottom of the vertical hole to the hole opening direction, and establishing a matrix calculation equation according to a relation formula of the sound wave velocities and the ground stress; calculating results of the horizontal stress, the vertical stress and the shear stress at the test section are obtained through a matrix solving method; and according to the obtained horizontal stress, vertical stress and shear stress, calculating the magnitude and the direction of the principal stress on the section by adopting an elastic mechanical formula. According to the method, the crustal stress in rock engineering can be indirectly measured, the operation is simple, and the calculation process does not need excessive theoretical assumptions.

Description

Technical Field

[0001] The present invention belongs to the technical field of geological exploration equipment, and more specifically, relates to a method for measuring in-situ stress based on acoustic wave velocity. Background Art

[0002] The methods for measuring in-situ stress are mainly divided into two categories: direct measurement methods and indirect measurement methods. The direct measurement methods include the stress relief method, the hydraulic fracturing method, the acoustic emission method, etc., while the indirect measurement methods include the differential strain analysis method, the differential strain curve analysis method, the inelastic strain recovery method, etc. Among them, the stress relief method is based on elastic theory and calculates the in-situ stress by monitoring the elastic deformation of the rock mass. This method is applicable to the construction stage and can measure the three-dimensional in-situ stress of the rock mass at a single point in a single borehole, but has high requirements for borehole quality; the hydraulic fracturing method injects high-pressure water into the borehole to break the rock and records the critical pressure value to calculate the in-situ stress. The advantages are simple operation, short test period, and no need for known rock elastic parameters. The disadvantages are strict requirements for borehole location and inability to provide three-dimensional in-situ stress information; the acoustic emission method is based on the Kaiser effect of the rock during repeated loading and determines the three-dimensional in-situ stress state by measuring the strain recovery amounts in different directions on the surface of the core. The advantages are that it can provide three-dimensional in-situ stress information and is applicable to the tunnel exploration stage. The disadvantages are high experimental conditions requirements and complex data processing.

[0003] In recent years, with the progress of technology, the indirect measurement method has gradually become the mainstream. The indirect measurement method records indirect physical quantities related to stress (such as rock mass deformation, density, permeability, resistivity, etc.) and then calculates the in-situ stress value through formulas or experience. This method has the advantages of non-contact, non-destructive, fast, accurate, etc., and is applicable to various geological conditions and engineering requirements. Summary of the Invention

[0004] In order to solve the problems existing in the existing in-situ stress measurement methods, the purpose of the present invention is to provide an indirect in-situ stress measurement method based on acoustic wave velocity, which can indirectly measure the in-situ stress in rock engineering, with simple operation and no need for excessive theoretical assumptions in the calculation process.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for measuring in-situ stress based on acoustic wave velocity, comprising the following steps:

[0007] Step 1, arrange a vertical hole and two horizontal holes in the same cross-section of the test tunnel;

[0008] Step 2, respectively measure the acoustic wave velocities of the vertical hole and the two horizontal holes;

[0009] Step 3: Test the acoustic wave velocities at different distances from the bottom of the vertical hole to the bottom and the orifice of the two horizontal holes; and test the acoustic wave velocities at different distances from the bottom of the two horizontal holes to the bottom and the orifice of the vertical hole.

[0010] Step 4: According to the relationship formula between the acoustic wave velocity and the in-situ stress, establish a matrix calculation equation, and obtain the calculation results of the horizontal stress, vertical stress, and shear stress at the test section through the matrix solution method.

[0011] Step 5: According to the obtained horizontal stress, vertical stress, and shear stress, calculate the magnitude and direction of the principal stress on this section using the elastic mechanics formula.

[0012] Optionally, arranging a vertical hole and two horizontal holes in the same section of the test tunnel includes: opening a test tunnel at the location where the in-situ stress needs to be tested, drilling a vertical hole upward from the crown of the test tunnel, and drilling a horizontal hole into the surrounding rock on both sides of the side wall of the test tunnel. The three holes should be arranged in the same section.

[0013] Optionally, acoustic wave testing is performed using an acoustic wave instrument. The main probe of the acoustic wave instrument should be capable of both transmitting and receiving acoustic wave signals. In addition to the main probe, the acoustic wave instrument can also be connected to an auxiliary probe that can receive acoustic wave signals.

[0014] Optionally, the separately testing of the acoustic wave velocities of the vertical hole and the two horizontal holes includes:

[0015] Connect the auxiliary probe to the acoustic wave instrument, and perform acoustic wave testing in one vertical hole and two horizontal holes respectively. During the testing process, insert the main probe into the bottom of the drill hole, and place the auxiliary probe at the orifice to measure the acoustic wave velocities V 11 、V 22 、V 33 。

[0016] Optionally, the testing of the acoustic wave velocities at different distances from the bottom of the vertical hole to the bottom and the orifice of the two horizontal holes; and the testing of the acoustic wave velocities at different distances from the bottom of the two horizontal holes to the bottom and the orifice of the vertical hole includes:

[0017] Step 3.1: Remove the auxiliary probe from the acoustic wave instrument, insert the main probe of one acoustic wave instrument into the bottom of the vertical hole, and insert the main probe of another acoustic wave instrument into the bottom of one of the horizontal holes. When starting the acoustic wave testing, first, the main probe in the vertical hole emits an acoustic wave signal, and the main probe in the horizontal hole receives the acoustic wave signal, and record the acoustic wave velocity as V 12-1 . Then, the main probe in the horizontal hole emits an acoustic wave signal, and the main probe in the vertical hole receives the acoustic wave signal, and record the acoustic wave velocity as V 21-1 ;

[0018] Step 3.2: Move the main probe in one of the horizontal holes 1.0 m to 2.0 m towards the hole opening for acoustic wave testing, and record the acoustic wave velocity V of this test respectively. 12-2 and V 21-2 ; Then move the main probe in one of the horizontal holes the same distance towards the hole opening, repeat the acoustic wave testing work, and record the acoustic wave velocity V of this test respectively. 12-3 and V 21-3 ;

[0019] Step 3.3: Take out the main probe in one of the horizontal holes, extend it to the bottom of the other horizontal hole, and let the main probe in the vertical hole emit acoustic wave signals, and the main probe in the other horizontal hole receive the acoustic wave signals, and record the acoustic wave velocity as V 13-1 , then let the main probe in the other horizontal hole emit acoustic wave signals, and the main probe in the vertical hole receive the acoustic wave signals, and record the acoustic wave velocity as V 31-1 ; Move the main probe in the other horizontal hole the same distance towards the hole opening, repeat the acoustic wave testing operation in step (e), and record the acoustic wave velocities V 13-2 , V 31-2 and V 13-3 , V 31-3 ;

[0020] Step 3.4: Extend the main probe of one acoustic wave instrument to the bottom of one of the horizontal holes, extend the main probe of the other acoustic wave instrument to the bottom of the vertical hole, move the main probe in the vertical hole 1.0 m to 2.0 m towards the hole opening, repeat the acoustic wave testing operation in step (e), and record the acoustic wave velocities V 21-b , V 12-b and V 21-c , V 12-c ; Extend the main probe of one acoustic wave instrument to the bottom of the other horizontal hole, extend the main probe of the other acoustic wave instrument to the bottom of the vertical hole, move the main probe in the vertical hole 1.0 m to 2.0 m towards the hole opening, repeat the acoustic wave testing operation in step (e), and record the acoustic wave velocities V 31-b , V 13-b and V 31-c , V 13-c .

[0021] Optionally, the establishment of a matrix calculation equation according to the relationship formula between acoustic wave velocity and in-situ stress, and obtaining the calculation results of horizontal stress, vertical stress and shear stress at the test section through matrix solution methods includes:

[0022] Obtain the stress of the rock mass in different directions according to the relationship formula between acoustic wave velocity and in-situ stress;

[0023] The change in sound velocity is expressed by the following formula:

[0024]

[0025] Where: V s is the longitudinal wave velocity under stress σ; V0 is the longitudinal wave velocity in the stress-free state; k is the proportionality constant; σ is the stress of the rock mass material;

[0026] V 12-1 、V 12-2 、V 12-3 are the acoustic wave velocities propagating in three directions from the bottom of the vertical hole to one of the horizontal holes, and the proportionality constant k 12 is the inherent property of the rock mass at that location, and is basically equal to k 21 . The stresses σ 12-1 、σ 12-2 、σ 12-3 and the angles β 12-1 、β 12-2 、β 12-3 with the horizontal direction. According to the elastic mechanics formula:

[0027]

[0028] Where: σ is the normal stress on a certain inclined plane, and the inclined plane is perpendicular to the test directions of V 12-1 、V 12-2 、V 12-3 respectively; σ x and σ y are the stresses in the horizontal and vertical directions respectively; τ is the shear stress; β is the angle between the inclined plane and the horizontal plane, which is equal to the angle between the test directions of V 12-1 、V 12-2 、V 12-3 and the vertical direction;

[0029] By combining Equation (1) and Equation (2), substituting V 12-1 、V 12-2 、V 12-3 into V s in Equation (1) respectively, substituting V 11 into V0 in Equation (1), substituting σ 12-1 、σ 12-2 、σ 12-3 into σ in Equation (2) respectively, and substituting β 12-1 、β 12-2 、β 12-3 into β in Equation (2), the first set of equations is established:

[0030]

[0031] Similarly, according to the acoustic wave velocity test results of the acoustic waves propagating in three directions from the bottom of the vertical hole to another horizontal hole, establish the second system of equations:

[0032]

[0033] Similarly, according to the acoustic wave velocity test results of the acoustic waves propagating in three directions from the bottom of one horizontal hole to the vertical hole, establish the third system of equations:

[0034]

[0035] Similarly, according to the acoustic wave velocity test results of the acoustic waves propagating in three directions from the bottom of the other horizontal hole to the vertical hole, establish the fourth system of equations:

[0036]

[0037] According to these four systems of equations, establish a matrix calculation equation, and obtain the calculation results of the horizontal stress, vertical stress and shear stress at the test section through the matrix solution method.

[0038] Furthermore, the rock mass quality of the test part should be basically consistent without obvious differences.

[0039] Furthermore, the hole diameters of the vertical hole and the horizontal holes need to meet the requirements of borehole acoustic wave testing, and the hole depths need to meet the requirements of in-situ stress testing.

[0040] Furthermore, the two horizontal holes are on the same horizontal plane and are symmetrically distributed along the vertical hole.

[0041] Preferably, the distance that the main probe moves each time when measuring the acoustic wave from the bottom of the hole to the hole mouth direction is 2.0 m.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] 1. The in-situ stress testing method provided by the present invention is mainly carried out by a borehole acoustic wave instrument, and the corresponding borehole acoustic wave testing is a rock mass quality evaluation test method with convenient and fast operation, and reliable test principle and interpretation method. Therefore, the in-situ stress testing method based on the borehole acoustic wave instrument itself has good reliability.

[0044] 2. The in-situ stress testing provided by the present invention can be carried out synchronously with the borehole acoustic wave testing, which can save the engineering test cost; at the same time, the acoustic wave testing results are rich, and the acoustic wave testing results in the adjacent test directions can be mutually verified, which can greatly improve the accuracy and rationality of the test results.

[0045] 3. The acoustic wave velocity test in a certain direction is conducted twice, which can improve the accuracy of the test results and reduce the impact of acoustic wave test errors on the calculation of ground stress. According to the test data in different directions, a set of equations can be established for solution, so that some physical quantities that require field tests to determine can be solved by simultaneous equations, thereby greatly improving the accuracy of ground stress calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0047] Figure 1 A schematic diagram of a method for testing ground stress using an acoustic wave instrument provided in one embodiment of the present invention;

[0048] Figure 2 A schematic diagram of a sound wave velocity test direction provided by an embodiment of the present invention;

[0049] Figure 3 A schematic diagram of calculation of formula (2) provided in one embodiment of the present invention;

[0050] Figure 4 A schematic diagram of the calculation of the equations (3) and (4) provided in one embodiment of the present invention;

[0051] Figure 5 A schematic diagram of the calculation of the equation groups (5) and (6) provided in one embodiment of the present invention.

[0052] Explanation of the reference numerals: 1 - test hole; 2 - vertical hole (hole No. 1); 3 - horizontal holes (hole No. 2, hole No. 3); 4 - main probe; 5 - auxiliary probe. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all of the embodiments. The components of the embodiment of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0054] It should be noted that like reference numerals and letters refer to like items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0055] In the description of the present invention, it should also be noted that in this text, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] The following will describe in detail some embodiments of the present invention with reference to the drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0057] A method for testing in-situ stress based on acoustic wave velocity includes the following steps:

[0058] (a) This test is preferably carried out in test tunnel 1. At the location where in-situ stress testing is required (the rock mass quality of the testing location should be basically the same without obvious differences), a vertical hole 2 (hole No. 1) is drilled upward from the crown of the test tunnel, and horizontal holes 3 (hole No. 2 and hole No. 3) are drilled into the surrounding rock on both sides of the side wall of the test tunnel. The diameters of the vertical hole 2 and the horizontal holes 3 should meet the requirements of borehole acoustic testing, and the hole depths should meet the requirements of in-situ stress testing. The three holes should be arranged in the same cross-section, and the two horizontal holes 3 are on the same horizontal plane and symmetrically distributed along the vertical hole 2; as Figure 1 shown;

[0059] (b) The main probe 4 of the borehole acoustic instrument for acoustic testing should have the function of both transmitting and receiving acoustic wave signals at the same time. In addition to the main probe, the acoustic instrument can also be connected with an auxiliary probe 5 that can receive acoustic wave signals;

[0060] (c) Initial value test: Connect the auxiliary probe 4 to the acoustic instrument, and conduct acoustic testing in one vertical hole 2 and two horizontal holes 3 respectively. During the testing process, insert the main probe 4 into the bottom of the borehole, and place the auxiliary probe 5 at the hole mouth, and measure the acoustic wave velocities V 11 、V 22 、V 33 of the vertical hole and the horizontal holes respectively, as Figure 1 shown;

[0061] (d) Second-stage test (fix hole No. 1 and move holes No. 2 and No. 3): Remove the auxiliary probe from the sonic detector. Insert the main probe of one sonic detector into the bottom of hole No. 1 and the main probe of the other sonic detector into the bottom of hole No. 2. When starting the sonic test, first let the main probe in hole No. 1 emit sonic signals, and the main probe in hole No. 2 receive the sonic signals. Record the sonic wave velocity as V 12-1 , as Figure 2 shown. Then let the main probe in hole No. 2 emit sonic signals, and the main probe in hole No. 1 receive the sonic signals. Record the sonic wave velocity as V 21-1 ;

[0062] (e) Move the main probe in hole No. 2 1.0 or 1.5 or 2.0 m towards the hole opening direction for sonic test work. Record the sonic wave velocities V 12-2 and V 21-2 of this test respectively. Then move the main probe in hole No. 2 the same distance towards the hole opening direction and repeat the sonic test work. Record the sonic wave velocities V 12-3 and V 21-3 of this test respectively;

[0063] (f) Take out the main probe in hole No. 2, insert it into the bottom of hole No. 3, and let the main probe in hole No. 1 emit sonic signals, and the main probe in hole No. 3 receive the sonic signals. Record the sonic wave velocity as V 13-1 , then let the main probe in hole No. 3 emit sonic signals, and the main probe in hole No. 1 receive the sonic signals. Record the sonic wave velocity as V 31-1 ; Move the main probe in hole No. 3 the same distance (1.0 or 1.5 or 2.0 m, consistent with the moving distance in step (e)) towards the hole opening direction and repeat the sonic test operation in step (e). Record the sonic wave velocities V 13-2 and V 31-2 and V 13-3 and V 31-3 of this test respectively;

[0064] (g) Third-stage test (fix holes No. 2 and No. 3 and move hole No. 1): Insert the main probe of one sonic detector into the bottom of hole No. 2 and the main probe of the other sonic detector into the bottom of hole No. 1. Move the main probe in hole No. 1 1.0 or 1.5 or 2.0 m (consistent with the moving distance in step (e)) towards the hole opening direction and repeat the sonic test operation in step (e). Record the sonic wave velocities V 21-b , V 12-b and V 21-c , V 12-cInsert the main probe of one sonic instrument into the bottom of Hole No. 3, and insert the main probe of another sonic instrument into the bottom of Hole No. 1. Move the main probe in Hole No. 1 towards the hole mouth by 1.0 or 1.5 or 2.0 m (consistent with the moving distance in step (e)), repeat the sonic testing operation in step (e), and record the sonic wave velocities V 31-b 、V 13-b and V 31-c 、V 13-c ;

[0065] (h) The sonic wave velocities V 11 、V 22 、V 33 are the test results from the bottom to the hole mouth, corresponding to the sonic information of the rock mass on the hole wall. Due to the release of drilling stress in the rock mass on the hole wall, its stored stress is basically zero. Compared with other sonic test results, it can be considered that the difference between the two results is due to the test path and the stored stress. According to the relationship formula between sonic wave velocity and in-situ stress, the stress of the rock mass in different directions (test paths) can be obtained.

[0066] According to the acoustoelastic theory, the propagation speed of sound waves in materials is closely related to the stress state of the rock mass material. Specifically, the change in sound speed can be expressed by the following formula:

[0067]

[0068] where: V s is the longitudinal wave sound speed under stress σ; V0 is the longitudinal wave sound speed in the stress-free state; k is the proportionality constant; σ is the stress of the rock mass material.

[0069] V 12-1 、V 12-2 、V 12-3 are the sonic wave velocities propagating from three positions (directions) at the bottom of Hole No. 1 towards Hole No. 2. The proportionality constant k 12 is the inherent property of the rock mass at that location and can be considered to be basically equal to k 21 (i.e., from the bottom of Hole No. 2 towards Hole No. 1). Similarly, k 13 is also basically equal to k 31 . As shown in Figure 3 、 Figure 4 , the stresses σ 12-1 、σ 12-2 、σ 12-3 in these three directions and the angles β 12-1 、β 12-2 、β 12-3 with the horizontal direction, according to the formulas of elasticity theory, there are:

[0070]

[0071] Where: σ is the normal stress on a certain inclined plane, and the inclined planes are respectively related to V 12-1 、V 12-2 、V 12-3 Test direction vertical; σ x and σ y are the stresses in the horizontal and vertical directions respectively; τ is the shear stress; β is the angle between the inclined plane and the horizontal plane, which is equal to V 12-1 、V 12-2 、V 12-3 The angle between the test direction and the vertical direction.

[0072] Combining equations (1) and (2), V 12-1 、V 12-2 、V 12-3 Substitute V into formula (1) s , V 11 Substituting V0 into equation (1), we can get 12-1 , σ 12-2 , σ 12-3 Substitute σ, β into formula (2) respectively 12-1 , β 12-2 , β 12-3 Substituting β into equation (2), we can establish the first set of equations:

[0073]

[0074] At this point, the relationship between wave velocity and horizontal stress, vertical stress and shear stress at the test section can be preliminarily established.

[0075] Similarly, according to the test results of the acoustic wave velocity propagating from the bottom of hole 1 to the three positions (directions) of hole 3, the second set of equations can be established:

[0076]

[0077] Similar, such as Figure 5 As shown in the figure, according to the test results of the acoustic wave velocity propagating from the bottom of hole 2 to the three positions (directions) of hole 1, the third set of equations can be established:

[0078]

[0079] Similarly, according to the test results of the acoustic wave velocity propagating from the bottom of hole 3 to the three positions (directions) of hole 1, the fourth set of equations can be established as follows:

[0080]

[0081] According to these four equations, the matrix calculation equation is established. The calculation results of horizontal stress, vertical stress and shear stress at the test section can be obtained by matrix solution method. At the same time, since 12 equations are combined to solve 5 unknown quantities (k12 , k 13 , σ x , σ y and τ), the redundant equations can be used to check the rationality of the results, thereby improving the accuracy of the calculation results.

[0082] (i) Based on the horizontal stress, vertical stress, and shear stress obtained on the test section of the test tunnel, the magnitudes and directions of the principal stresses on this section can be calculated using the formulas of elastic mechanics.

Claims

1. A method for in-situ stress testing based on acoustic wave velocity, characterized in that It includes the following steps: Step 1: Arrange a vertical hole and two horizontal holes in the same cross-section of the test tunnel. Step 2: Measure the acoustic wave velocities of the vertical hole and the two horizontal holes respectively. Step 3: Measure the acoustic wave velocities at different distances from the bottom of the vertical hole to the bottom and the orifice of the two horizontal holes along the direction from the bottom to the orifice of the horizontal holes. And measure the acoustic wave velocities at different distances from the bottom of the two horizontal holes to the bottom and the orifice of the vertical hole along the direction from the bottom to the orifice of the vertical hole. Step 4: According to the relationship formula between acoustic wave velocity and in-situ stress, establish a matrix calculation equation, and obtain the calculation results of the horizontal stress, vertical stress and shear stress at the test cross-section through the matrix solution method. Step 5: According to the obtained horizontal stress, vertical stress and shear stress, use the elastic mechanics formula to calculate the magnitudes and directions of the principal stresses on this cross-section.

2. The in-situ stress testing method based on acoustic wave velocity according to claim 1, characterized in that The arrangement of a vertical hole and two horizontal holes in the same cross-section of the test tunnel includes: Open a test tunnel at the part where in-situ stress measurement is required. Drill a vertical hole upward from the crown of the test tunnel, and drill one horizontal hole into the surrounding rock on each side of the side wall of the test tunnel. The three holes should be arranged in the same cross-section.

3. The method for in-situ stress testing based on acoustic wave velocity according to claim 2, wherein, The acoustic wave test is carried out by an acoustic wave instrument. The main probe of the acoustic wave instrument should have the function of both transmitting and receiving acoustic wave signals at the same time. In addition to the main probe, the acoustic wave instrument can also be connected with auxiliary probes that can receive acoustic wave signals.

4. The in-situ stress testing method based on acoustic wave velocity according to claim 3, characterized in that The measurement of the acoustic wave velocities of the vertical hole and the two horizontal holes respectively includes: Connect the auxiliary probe to the acoustic wave instrument and conduct acoustic wave tests in one vertical hole and two horizontal holes respectively. During the test, insert the main probe into the bottom of the borehole and place the auxiliary probe at the hole mouth to measure the acoustic wave velocities V 11 、V 22 、V 33 。 5. The in-situ stress testing method based on acoustic wave velocity according to claim 4, wherein The measurement of the acoustic wave velocities at different distances from the bottom of the vertical hole to the bottom and the orifice of the two horizontal holes along the direction from the bottom to the orifice of the horizontal holes; And the measurement of the acoustic wave velocities at different distances from the bottom of the two horizontal holes to the bottom and the orifice of the vertical hole along the direction from the bottom to the orifice of the vertical hole includes: Step 3.1: Remove the auxiliary probe from the sonic instrument. Insert the main probe of one sonic instrument into the bottom of the vertical hole, and insert the main probe of the other sonic instrument into the bottom of one of the horizontal holes. When starting the sonic test, first let the main probe in the vertical hole emit sonic signals, and let the main probe in the horizontal hole receive the sonic signals. Record the sonic wave velocity as V 12-1 , and then let the main probe in the horizontal hole emit sonic signals, and let the main probe in the vertical hole receive the sonic signals. Record the sonic wave velocity as V 21-1 ; Step 3.2: Move the main probe in one of the horizontal holes 1.0 m to 2.0 m towards the hole opening for acoustic wave testing work, and record the acoustic wave velocity V of this test respectively 12-2 and V 21-2 ; Then move the main probe in one of the horizontal holes the same distance towards the hole opening, repeat the acoustic wave testing work, and record the acoustic wave velocity V of this test respectively 12-3 and V 21-3 ; Step 3.3: Take out the main probe in one of the horizontal holes, extend it to the bottom of the other horizontal hole, and let the main probe in the vertical hole emit an acoustic wave signal, and the main probe in the other horizontal hole receive the acoustic wave signal, and record the acoustic wave velocity as V 13-1 , then let the main probe in the other horizontal hole emit an acoustic wave signal, and the main probe in the vertical hole receive the acoustic wave signal, and record the acoustic wave velocity as V 31-1 ; Move the main probe in the other horizontal hole the same distance towards the hole mouth direction, repeat the acoustic wave test operation in step (e), and record the acoustic wave velocities V 13-2 , V 31-2 and V 13-3 , V 31-3 respectively; Step 3.4: Insert the main probe of one sonic detector into the bottom of one of the horizontal holes, and insert the main probe of the other sonic detector into the bottom of the vertical hole. Move the main probe in the vertical hole 1.0 m to 2.0 m towards the hole opening, repeat the sonic test operation in step (e), and record the sonic wave velocities V 21-b , V 12-b and V 21-c , V 12-c ; Insert the main probe of one sonic detector into the bottom of the other horizontal hole, and insert the main probe of the other sonic detector into the bottom of the vertical hole. Move the main probe in the vertical hole 1.0 m to 2.0 m towards the hole opening, repeat the sonic test operation in step (e), and record the sonic wave velocities V 31-b , V 13-b and V 31-c , V 13-c .

6. The method for in-situ stress testing based on acoustic wave velocity according to claim 5, wherein The establishment of a matrix calculation equation according to the relationship formula between acoustic wave velocity and in-situ stress, and the obtaining of the calculation results of the horizontal stress, vertical stress and shear stress at the test cross-section through the matrix solution method includes: According to the relationship formula between acoustic wave velocity and in-situ stress, obtain the stresses of the rock mass in different directions. The change in sound velocity is expressed by the following formula: Where: V s is the longitudinal wave velocity under stress σ; V0 is the longitudinal wave velocity in the stress-free state; k is the proportionality constant; σ is the stress of the rock mass material; V 12-1 、V 12-2 、V 12-3 are the sound wave velocities propagating in three directions from the bottom of the vertical hole to one of the horizontal holes, and the proportionality constant k 12 is the inherent property of the rock mass at that location, which is basically equal to k 21 . The stresses σ 12-1 、σ 12-2 、σ 12-3 and the angles β 12-1 、β 12-2 、β 12-3 between these stresses and the horizontal direction. According to the elastic mechanics formula, we have: Where: σ is the normal stress on a certain inclined plane, and the inclined plane is perpendicular to the test directions of V 12-1 , V 12-2 , V 12-3 respectively; σ x and σ y are the horizontal and vertical stresses respectively; τ is the shear stress; β is the angle between the inclined plane and the horizontal plane, equal to the angle between the test directions of V 12-1 , V 12-2 , V 12-3 and the vertical direction respectively; Combining equations (1) and (2), substitute V 12-1 、V 12-2 、V 12-3 into V s in equation (1) respectively, substitute V 11 into V0 in equation (1), substitute σ 12-1 、σ 12-2 、σ 12-3 into σ in equation (2) respectively, and substitute β 12-1 、β 12-2 、β 12-3 into β in equation (2) to establish the first system of equations: Similarly, according to the test results of the acoustic wave velocities propagated in 3 directions from the bottom of the vertical hole to the other horizontal hole, establish the second set of equations: Similarly, according to the test results of the acoustic wave velocities propagated in 3 directions from the bottom of one horizontal hole to the vertical hole, establish the third set of equations: Similarly, according to the test results of the acoustic wave velocities propagated in 3 directions from the bottom of the other horizontal hole to the vertical hole, establish the fourth set of equations: According to these four sets of equations, establish a matrix calculation equation, and obtain the calculation results of the horizontal stress, vertical stress and shear stress at the test cross-section through the matrix solution method.

7. The in-situ stress testing method based on acoustic wave velocity according to claim 2, characterized in that, The rock mass quality at the test part should be basically consistent without obvious differences.

8. The in-situ stress testing method based on acoustic wave velocity according to claim 2, wherein The diameters of the vertical hole and the horizontal holes should meet the requirements of borehole acoustic wave testing, and the hole depths should meet the requirements of in-situ stress testing.

9. The in-situ stress testing method based on acoustic wave velocity according to claim 2, characterized in that The two horizontal holes are on the same horizontal plane and are symmetrically distributed along the vertical hole.

10. The method for in-situ stress testing based on acoustic wave velocity according to claim 5, wherein The distance that the main probe moves each time when measuring the acoustic wave from the bottom of the hole to the orifice direction is 2.0 m.

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