In-hole rock mass in-situ testing device and testing method thereof

Abstract

The invention relates to an in-hole rock mass in-situ testing device and a testing method thereof, and belongs to the technical field of rock mass testing. The testing device comprises a measuring rod, hole wall fixing devices, a hole wall loading device, a conveying rod and a control system, the hole wall fixing devices are arranged at the two ends of the measuring rod respectively, the hole wall loading device is arranged in the middle of the measuring rod, one end of the measuring rod is connected with the conveying rod, and the hole wall fixing devices and the hole wall loading device are both connected with the control system. According to the invention, multi-measuring-point rock mass testing around the periphery of the hole at a certain position in the drill hole can be realized, and different stress states of the rock mass around the hole can be evaluated through the difference of the press-in characteristics of the double probes under multi-angle testing, so that the mechanical characteristics of the rock mass under different stress states can be identified.

Description

Technical Field

[0001] The invention relates to an in-hole rock mass in-situ testing device and a testing method thereof, belonging to the technical field of rock mass testing. Background Art

[0002] Reasonable acquisition of the in-situ mechanical properties of rock mass is an important prerequisite for analyzing rock mass engineering problems. The method of evaluating rock mass properties based on in-situ testing in boreholes has the characteristics of convenient operation and strong applicability, and has broad application prospects. The important advantage of in-situ testing in boreholes is that it can reflect the mechanical state of the rock mass under the actual ground stress state. For the rock mass on the borehole wall, it is under in-situ ground stress conditions. Due to the different magnitudes of ground stress in various directions, the constraint stress state of the rock mass within 360° around the borehole wall at the same position is different (distributed continuously from small to large with a period of 90°). The difference in stress distribution around the hole of the rock mass stress state will have an important impact on the test results (the higher the constraint stress of the rock mass, the greater its load-breaking strength).

[0003] When testing the characteristics of the borehole rock mass, the direction of the rock mass ground stress should be clarified, and then the differences in the stress states of the rock mass at different measuring points should be clarified. This is an important prerequisite for the rational analysis of the characteristics of the rock mass. However, the existing in-hole rock mass testing technology, such as the in-situ testing method and device for rock strength in a borehole disclosed in the Chinese patent document CN117147310A, does not take into account the impact of the different in-situ stresses around the hole on the test results. In addition, when the existing testing device is loading in the hole, the other side of the hole wall needs to provide a supporting reaction force. This reaction force directly acts on the hole around the measuring point, which will change the stress state of the rock mass on the hole wall, bringing further impact to the test results. The supporting reaction force of the testing device will also cause the deformation of the rock mass on the hole wall, bringing errors to the displacement measurement in the test. How to eliminate the impact of the supporting reaction force of the testing device on the test results is an important issue that should be considered to improve the test accuracy. For this reason, the present invention is proposed. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an in-hole rock mass in-situ testing device, which can realize the rock mass testing at multiple measuring points around the hole at a certain position in the borehole, and evaluate the difference in stress state of the rock mass around the hole through the difference in the pressure characteristics of the dual probes under multi-angle testing, and then identify the mechanical properties of the rock mass under different stress states;

[0005] At the same time, it can avoid the support reaction force acting directly on the hole wall when loading in the hole, and can effectively reduce the influence of the support reaction force on the stress state of the rock mass near the measuring point during the test. The reverse displacement of the support end can also be accurately tested, so as to correct the displacement recorded by the displacement sensor of the device to ensure that the real rock mass pressure displacement can be obtained (the total displacement of the probe extended minus the displacement of the support end is the real displacement of the probe pressed into the rock mass), so as to more accurately realize the test and evaluation of the mechanical properties of the rock mass under different stress states.

[0006] The present invention also provides a testing method for the in-hole rock mass in-situ testing device.

[0007] The technical solution of the present invention is as follows:

[0008] An in-hole rock mass in-situ testing device comprises a measuring rod, a hole wall fixing device, a hole wall loading device, a conveying rod and a control system, wherein the hole wall fixing devices are respectively arranged at both ends of the measuring rod, the hole wall loading device is arranged in the middle of the measuring rod, one end of the measuring rod is connected to the conveying rod, and the hole wall fixing device and the hole wall loading device are both connected to the control system.

[0009] Preferably according to the present invention, the hole wall fixing device includes a fixing block, a contact support and a hydraulic rod A. The fixing block is a hollow annular block. The inner ring of the fixing block is fixed to the measuring rod through a bearing. Arc-shaped contact supports are evenly distributed on the outer ring of the fixing block through the hydraulic rod A.

[0010] Preferably, according to the present invention, the hole wall loading device includes a loading block, a loading probe and a hydraulic rod B. The loading block is a hollow annular block. The inner ring of the loading block is fixed to the measuring rod. Two loading probes are arranged in the loading block through the hydraulic rod B.

[0011] According to a further preferred embodiment of the present invention, the two loading probes are arranged at 90°.

[0012] Preferably according to the present invention, a displacement sensor is provided in the loading block on one side of the loading probe.

[0013] Preferably, according to the present invention, two strain gauges are respectively arranged on the measuring rods on the upper and lower sides of the hole wall loading device, and the strain gauges are located on the back side of the loading probe, that is, the two strain gauges on the upper side of the hole wall loading device are located on the back sides of the two loading probes, and one strain gauge corresponds to the back side of one loading probe, and the two strain gauges on the lower side of the hole wall loading device are similarly arranged.

[0014] Preferably according to the present invention, hydraulic rod A and hydraulic rod B are connected with a hydraulic transmission system via a flexible hydraulic pipe, and the flexible hydraulic pipe adopts a design of spiraling outside the measuring rod and combining with an internal structure to avoid interference with the rotation of the measuring rod.

[0015] Preferably according to the present invention, the displacement sensor, the strain gauge and the loading probe are all connected to a control system via a data acquisition line.

[0016] The testing method of the above-mentioned in-hole rock mass in-situ testing device comprises the following steps:

[0017] (1) Drill a hole inside the underground rock mass, use a delivery rod to send the test device into the hole to the depth to be tested, extend the hydraulic rod A, extend the contact support, and make the contact support contact and press against the inner wall of the rock mass;

[0018] (2) After tightening, read the strain values ​​of the four strain gauges on the measuring rod. When all readings are 0, it indicates that the measuring rod has been centered. Otherwise, unload the contact support and re-center it.

[0019] (3) The hydraulic rod B is extended and loaded to control the two loading probes in the hole wall loading device to be pressed into the hole wall rock mass at the same time. The displacement sensor records the displacement of the two loading probes. During the pressing process of the loading probes, the reading of the strain gauge on the measuring rod is monitored, and the deformation displacement of the measuring rod in the two opposite directions of the pressing is inverted, that is, the reverse deformation of the support end during the loading process, and the true displacement of the two loading probes is calculated;

[0020] (4) Read the real-time pressure data of the loading probe, draw the relationship curve between the pressing load and the real pressing displacement of the two loading probes during the pressing process, calculate the ratio of the pressing load peak value of the curve to the corresponding real pressing displacement, and obtain the loading stiffness K of the loading probe;

[0021] (5) Unload the pressure to make the loading probe retract and separate from the hole wall, rotate the measuring rod, and repeat steps (2)-(4) after rotating it for a certain angle to obtain the loading stiffness K at multiple angles. Calculate and draw the relationship curve between the difference in loading stiffness and the rotation angle θ of the two loading probe compression curves at different angles. Considering that the constraint stress of the hole wall rock mass reaches the maximum and minimum values ​​in the two principal stress directions, when the two probes are parallel to the two principal stress directions, the difference in the test results is the largest. Therefore, the rotation angle θ corresponding to the maximum value of the loading stiffness difference is the principal stress direction of the ground stress.

[0022] (6) When the loading angle corresponding to the principal stress direction is tested, the loading stiffness of the two loading probes is extracted. The strength characteristics of the rock mass are evaluated based on the loading stiffness of the two loading probes. The larger value is the rock mass strength corresponding to the high constraint stress, and the smaller value is the rock mass strength corresponding to the low constraint stress.

[0023] According to a preferred embodiment of the present invention, in step (3), the inversion calculation process of the deformation displacement of the measuring rod in two opposite directions of pressing is:

[0024]

[0025] Where: δ2 is the deformation displacement of the measuring rod in the opposite direction of pressing, ε is the strain value recorded by the strain gauge, l is the length of the measuring rod, r is the radius of the measuring rod, and k is the calibration coefficient.

[0026] Before the device is put into use, the precise bending deformation of the measuring rod is obtained in the laboratory by loading the measuring rod (applying a concentrated load at the position of the loading probe). The value of the parameter k is verified by comparing it with the value calculated by formula (1).

[0027] Preferably, according to the present invention, in step (3), two loading probes are set as loading probe a and loading probe b, and the real displacement calculation process of the two loading probes is:

[0028]

[0029] Where: and are the extension displacements of loading probe a and loading probe b recorded by the displacement sensor respectively;

[0030] and are the deformation displacements of the measuring rod in the opposite directions of the loading probe a and the loading probe b calculated by formula (1);

[0031] δ a and δ b are the true displacements of loading probe a and loading probe b respectively.

[0032] Preferably, according to the present invention, in step (4), the calculation formula of the loading stiffness K is:

[0033]

[0034] Where: P max is the peak value of the indentation load, δ max is the actual indentation displacement corresponding to the indentation load peak.

[0035] Preferably, according to the present invention, in step (5), the loading stiffness difference calculation formula is:

[0036] |ΔK|=K a -K b (5)

[0037] In the formula, K a and K b are the loading stiffness of loading probe a and loading probe b calculated using formula (4) respectively.

[0038] The beneficial effects of the present invention are:

[0039] 1. The present invention can realize the rock mass property test at multiple measuring points around a certain position in the borehole, and evaluate the difference in the stress state of the rock mass around the hole by the difference in the pressing characteristics of the double loading probe under multi-angle testing, so as to identify the mechanical properties of the rock mass under different stress states;

[0040] 2. The present invention can prevent the support reaction force from directly acting on the hole wall when loading in the hole, and can effectively reduce the influence of the support reaction force on the stress state of the rock mass near the measuring point during the test, ensuring that the test results can better reflect the in-situ stress state of the rock mass on the hole wall.

[0041] 3. The present invention can realize accurate testing of the reverse displacement of the support end, so that the probe displacement recorded by the device displacement sensor can be corrected to ensure that the real rock mass intrusion displacement can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a structural schematic diagram of the present invention;

[0043] Figure 2 It is a schematic diagram of the structure of the hole wall fixing device of the present invention;

[0044] Figure 3 It is a schematic diagram of the structure of the hole wall loading device of the present invention;

[0045] Figure 4 It is a schematic diagram of the cross-sectional structure of the hole wall loading device of the present invention;

[0046] Figure 5 Schematic diagram of multi-angle loading of the hole wall of the present invention, wherein a and b represent the positions of the two loading probes before rotation, and a' and b' represent the positions of the two loading probes after rotation;

[0047] Figure 6 is a curve diagram showing the relationship between the difference in the hole circumference loading stiffness and the rotation angle θ of the present invention;

[0048] Among them: 1. Measuring rod; 2. Hole wall fixing device; 3. Hole wall loading device; 4. Loading probe; 5. Contact support; 6. Displacement sensor; 7. Conveying rod; 8. Bearing; 9. Strain gauge; 10. Flexible hydraulic pipe; 11. Hydraulic transmission system; 12. Control system; 13. Data acquisition line; 14. Fixing block; 15. Loading block. DETAILED DESCRIPTION

[0049] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings, but is not limited thereto.

[0050] Embodiment 1:

[0051] like Figure 1-Figure 5As shown, this embodiment provides an in-situ testing device for rock mass in a hole, comprising a measuring rod 1, a hole wall fixing device 2, a hole wall loading device 3, a conveying rod 7 and a control system 12, wherein the hole wall fixing devices 2 are respectively provided at both ends of the measuring rod 1, the hole wall loading device 3 is provided in the middle of the measuring rod 1, one end of the measuring rod 1 is connected to the conveying rod 7, and the hole wall fixing device 2 and the hole wall loading device 3 are both connected to the control system 12.

[0052] The hole wall fixing device 2 includes a fixing block 14, a contact support 5 and a hydraulic rod A. The fixing block 14 is a hollow annular block. The inner ring of the fixing block 14 is fixed to the measuring rod 1 through a bearing 8. The outer ring of the fixing block 14 is evenly distributed with arc-shaped contact supports 5 through the hydraulic rod A.

[0053] The hole wall loading device 3 includes a loading block 15, a loading probe 4 and a hydraulic rod B. The loading block 15 is a hollow ring block. The inner ring of the loading block 15 is fixed to the measuring rod 1. Two loading probes 4 are arranged in the loading block through the hydraulic rod B. The two loading probes 4 are arranged at 90 degrees.

[0054] A displacement sensor 6 is disposed in the loading block 15 on one side of the loading probe 4 .

[0055] Two strain gauges 9 are respectively arranged on the measuring rod 1 on the upper and lower sides of the hole wall loading device 3. The strain gauges 9 are located on the back side of the loading probe 4, that is, the two strain gauges 9 on the upper side of the hole wall loading device 3 are located on the back side of the two loading probes 4. The two loading probes are set as loading probe a and loading probe b, one strain gauge corresponds to the back side of loading probe a, and the other strain gauge corresponds to the back side of loading probe b. The two strain gauges 9 on the lower side of the hole wall loading device are arranged in the same way.

[0056] The hydraulic rod A and the hydraulic rod B are connected to a hydraulic transmission system 11 through a flexible hydraulic pipe 10. The flexible hydraulic pipe adopts a design of spiraling outside the measuring rod and combining with an internal structure to avoid interference with the rotation of the measuring rod.

[0057] The displacement sensor 6 , the strain gauge 9 and the loading probe 4 are all connected to a control system 12 via a data acquisition line 13 .

[0058] The testing method of the above-mentioned in-hole rock mass in-situ testing device comprises the following steps:

[0059] (1) Drill a hole inside the underground rock mass, use the delivery rod 7 to deliver the test device into the hole to the depth to be measured, extend the hydraulic rod A, extend the contact support 5, and make the contact support 5 contact and press against the inner wall of the rock mass;

[0060] (2) After tightening, read the strain values ​​of the four strain gauges 9 on the measuring rod 1. When all the readings are 0, it indicates that the measuring rod 1 has been centered. Otherwise, release the pressure on the contact support 5 and re-center it.

[0061] (3) The hydraulic rod B is extended to load, and the two loading probes 4 in the hole wall loading device 3 are controlled to be pressed into the hole wall rock mass at the same time. The displacement sensor 6 records the displacement of the two loading probes. During the pressing process of the loading probe 4, the reading of the strain gauge 9 on the measuring rod 1 is monitored, and the deformation displacement of the measuring rod 1 in the opposite direction of the two pressing directions is inverted to obtain, that is, the reverse deformation of the support end during the loading process. The calculation process is:

[0062]

[0063] Where: δ2 is the deformation displacement of the measuring rod in the opposite direction of the pressing, ε is the strain value recorded by the strain gauge, l is the length of the measuring rod, r is the radius of the measuring rod, and k is the calibration coefficient;

[0064] Before the device is put into use, the precise bending deformation of the measuring rod is obtained by loading the measuring rod in the laboratory (a concentrated load is applied at the position of the loading probe). The value of the parameter k is checked by comparing it with the value calculated by formula (1).

[0065] The two loading probes 4 are set as loading probe a and loading probe b, and the real displacement calculation process of the two loading probes 4 is:

[0066]

[0067]

[0068] Where: and are the extension displacements of loading probe a and loading probe b recorded by the displacement sensor respectively;

[0069] and are the deformation displacements of the measuring rod in the opposite directions of the loading probe a and the loading probe b calculated by formula (1);

[0070] δ a and δ b are the true displacements of loading probe a and loading probe b respectively;

[0071] (4) Read the real-time pressure data of the loading probe, draw the relationship curve between the pressing load and the actual pressing displacement of the two loading probes during the pressing process, calculate the ratio of the peak value of the curve pressing load to the corresponding actual pressing displacement, and obtain the loading stiffness K of the loading probe:

[0072]

[0073] Where: P max is the peak value of the indentation load, δ max is the actual indentation displacement corresponding to the indentation load peak;

[0074] (5) Unload the pressure to make the loading probe retract and detach from the hole wall. Rotate the measuring rod. Repeat steps (2) to (4) after rotating it to a certain angle to obtain the loading stiffness K at multiple angles. Calculate and plot the relationship between the difference in loading stiffness |ΔK| between the two loading probe compression curves at different angles and the rotation angle θ, as shown in the figure. Figure 6 As shown:

[0075] |ΔK|=K a -K b (5)

[0076] In the formula, K a and K b are the loading stiffness of loading probe a and loading probe b calculated using formula (4) respectively;

[0077] Considering that the restraint stress of the hole wall rock mass reaches the maximum and minimum values ​​in the two principal stress directions, when the two probes are parallel to the two principal stress directions, the difference in the test results is the largest. Therefore, the rotation angle θ corresponding to the maximum value of the difference in loading stiffness is the principal stress direction of the ground stress.

[0078] (6) When the loading angle corresponding to the principal stress direction is tested, the loading stiffness of the two loading probes is extracted. The strength characteristics of the rock mass are evaluated based on the loading stiffness of the two loading probes. The larger value is the rock mass strength corresponding to the high constraint stress, and the smaller value is the rock mass strength corresponding to the low constraint stress.

[0079] The above descriptions are only preferred embodiments of the present invention. It should be pointed out that those skilled in the art can make improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be considered as within the protection scope of the present invention.

Claims

1. An in-situ testing device for rock mass in a hole, characterized in that: It includes a measuring rod, a hole wall fixing device, a hole wall loading device, a conveying rod and a control system, wherein the hole wall fixing devices are respectively arranged at both ends of the measuring rod, the hole wall loading device is arranged in the middle of the measuring rod, one end of the measuring rod is connected to the conveying rod, and the hole wall fixing device and the hole wall loading device are both connected to the control system; The hole wall fixing device includes a fixing block, a contact support and a hydraulic rod A. The fixing block is a hollow annular block. The inner ring of the fixing block is fixed to the measuring rod through a bearing. The outer ring of the fixing block is evenly provided with arc-shaped contact supports through the hydraulic rod A.

2. The in-hole rock mass in-situ testing device according to claim 1, characterized in that: The hole wall loading device includes a loading block, a loading probe and a hydraulic rod B. The loading block is a hollow ring block. The inner ring of the loading block is fixed to the measuring rod. Two loading probes are arranged in the loading block through the hydraulic rod B.

3. The in-hole rock mass in-situ testing device according to claim 2, characterized in that: The two loading probes are set at 90°.

4. The in-hole rock mass in-situ testing device according to claim 3, characterized in that: A displacement sensor is arranged in the loading block on one side of the loading probe.

5. The in-hole rock mass in-situ testing device according to claim 4, characterized in that: Two strain gauges are respectively arranged on the measuring rods on the upper and lower sides of the hole wall loading device, and the strain gauges are located on the back side of the loading probe.

6. The in-hole rock mass in-situ testing device according to claim 5, characterized in that: The hydraulic rod A and the hydraulic rod B are connected with a hydraulic transmission system through a flexible hydraulic pipe.

7. The testing method of the in-hole rock mass in-situ testing device according to claim 6, characterized in that: Here are the steps: (1) Drill a hole inside the underground rock mass, use a delivery rod to send the test device into the hole to the depth to be tested, extend the hydraulic rod A, extend the contact support, and make the contact support contact and press against the inner wall of the rock mass; (2) After tightening, read the strain values ​​of the four strain gauges on the measuring rod. When all readings are 0, it indicates that the measuring rod has been centered. Otherwise, unload the contact support and re-center it. (3) The hydraulic rod B is extended and loaded to control the two loading probes in the hole wall loading device to be pressed into the hole wall rock mass at the same time. The displacement sensor records the displacement of the two loading probes. During the pressing process of the loading probes, the reading of the strain gauge on the measuring rod is monitored, and the deformation displacement of the measuring rod in the two opposite directions of the pressing is obtained by inversion, and the true displacement of the two loading probes is calculated; (4) Read the real-time pressure data of the loading probe, draw the relationship curve between the pressing load and the real pressing displacement of the two loading probes during the pressing process, calculate the ratio of the pressing load peak value of the curve to the corresponding real pressing displacement, and obtain the loading stiffness K of the loading probe; (5) Unload the pressure to make the loading probe retract and separate from the hole wall, rotate the measuring rod, and repeat steps (2) to (4) after rotating it for a certain angle to obtain the loading stiffness K at multiple angles. Calculate and draw the relationship curve between the difference in loading stiffness and the rotation angle θ of the two loading probe compression curves at different angles. The rotation angle θ corresponding to the maximum value of the loading stiffness difference is the principal stress direction of the ground stress. (6) The loading stiffness of the two loading probes during the loading angle test corresponding to the principal stress direction is extracted, and the strength characteristics of the rock mass are evaluated based on the loading stiffness of the two loading probes.

8. The testing method of the in-hole rock mass in-situ testing device according to claim 7, characterized in that: In step (3), the inversion calculation process of the deformation displacement of the measuring rod in the two opposite directions of compression is: Where: δ2 is the deformation displacement of the measuring rod in the opposite direction of pressing, ε is the strain value recorded by the strain gauge, l is the length of the measuring rod, r is the radius of the measuring rod, and k is the calibration coefficient.

9. The testing method of the in-hole rock mass in-situ testing device according to claim 8, characterized in that: In step (3), two loading probes are set as loading probe a and loading probe b, and the actual displacement calculation process of the two loading probes is: Where: and are the extension displacements of loading probe a and loading probe b recorded by the displacement sensor respectively; and are the deformation displacements of the measuring rod in the opposite directions of the loading probe a and the loading probe b calculated by formula (1); δ a and δ b are the true displacements of loading probe a and loading probe b respectively.

10. The testing method of the in-hole rock mass in-situ testing device according to claim 9, characterized in that: In step (4), the calculation formula of loading stiffness K is: Where: P max is the peak value of the indentation load, δ max is the actual indentation displacement corresponding to the indentation load peak; In step (5), the loading stiffness difference calculation formula is: |ΔK|=K a -K b (5) In the formula, K a and K b are the loading stiffness of loading probe a and loading probe b calculated using formula (4) respectively.

Images