Rock strength in-situ testing method based on drill hole wall penetration method

Abstract

The invention discloses a rock strength in-situ testing method based on a drill hole wall penetration method. The method comprises the following steps: S1, connecting a hydraulic power system with a data acquisition system; s2, connecting a hydraulic power system with the probe assembly; s3, connecting the front end of the push rod with the rear end of the probe assembly; s4, a push rod is controlled to push the probe assembly into the drill hole; and S5, a hydraulic power system is started, power is transmitted to the probe assembly, a pressing head of the probe assembly extends in the radial direction of the drill hole to abut against the hole wall, and the uniaxial compressive strength of the surrounding rock is tested through a data acquisition system. The test data can better reflect the in-situ rock strength. The device can measure the rock strength of different drill holes, different depths and different point positions, so that the distribution condition of the roadway rock strength is obtained, the measurement result is closer to the field rock mass, the measurement process is simple and convenient, the problems occurring in the sampling process and the like are avoided, the measurement efficiency is greatly improved, the measurement cost is reduced, and the device has good popularization value.

Description

Technical Field

[0001] The invention belongs to the technical field of rock strength testing, and in particular relates to an in-situ rock strength testing method based on a borehole wall penetration method. Background Art

[0002] Rock strength testing is widely used and important in engineering contexts. It provides a scientific basis for engineering design, construction and maintenance, ensures the safety, stability and durability of various engineering structures, and is an indispensable key link in geotechnical engineering and mining engineering. The existing rock strength testing methods are divided into laboratory tests and in-situ tests. The laboratory test method is to first drill the core underground, then transport it to the laboratory and process it into test pieces for rock mechanical parameter determination. This method has the following limitations: (1) Difficulty in obtaining cores. When the surrounding rock is relatively soft and broken, it is difficult to obtain a complete core. Most rock masses contain weak surfaces or weak interlayers. Especially in coal-bearing strata, rocks with very low strength, such as claystone, carbonaceous shale, coal, etc., are often encountered, which are not easy to prepare into rock specimens.

[0003] (2) The necessary preparation process of rock samples is rather cumbersome and the cost of laboratory testing is high.

[0004] (3) There may be some differences from the on-site conditions. The rock characteristic indicators obtained in the laboratory are relatively complete and do not contain obvious weak surfaces in the off-site environment. They are easily affected by sampling conditions and specimen preparation, which may destroy the original state of the surrounding rock, affect its strength and stability, and are inconsistent with the actual on-site conditions.

[0005] (4) When designing tunnel support, it is necessary to have a detailed understanding of the layer thickness, rock strength, and structural surface distribution of the rock strata above the tunnel roof and within a certain range on both sides. This will provide a basis for determining the anchor length, strength, spacing, and layout. The amount of information obtained from some laboratory tests is relatively limited and often difficult to meet the design needs.

[0006] The existing in-situ tests include sonic detection, borehole drilling, impact hammer and borehole penetration. The sonic detection method is greatly affected by the surrounding environment and the internal structure of the coal and rock mass, and the test accuracy is not high; when the borehole drilling method is used to measure the strength of the coal mass, when the coal mass strength is very small or the coal and rock mass is fully broken before being drilled, the thrust and torque of the drill bit when cutting this part of the coal mass will become smaller, resulting in deviations in the final measured results; the impact hammer method is suitable for measuring the surface strength of the rock mass, and is currently mainly used for concrete testing. In mining projects, a detailed understanding of the physical and mechanical properties of the rock mass is required, so this method is rarely used in mining projects; the existing borehole penetration method test device is large in size and cannot be applied to small drilling conditions. Summary of the invention

[0007] The purpose of the present invention is to provide an in-situ rock strength testing method based on the borehole wall probing method, which is suitable for small boreholes, easy to operate and has high test data accuracy. This method extends a probe assembly into the rock mass to be tested to drill a hole or directly utilizes pressure relief and drilling in an engineering borehole, and pressurizes the borehole wall for in-situ rapid testing; and by integrating data such as displacement, pressure and test depth, a real-time displacement-pressure curve can be drawn during the acquisition process, so as to understand the rock strength testing process in more detail.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solution: an in-situ rock strength testing method based on a borehole wall penetration method comprises the following steps: S1. Connect the hydraulic power system to the data acquisition system; S2, connecting the hydraulic power system to the probe assembly; S3, connecting the front end of the push rod to the rear end of the probe assembly; S4, operate the push rod to push the probe assembly into the borehole; S5. Start the hydraulic power system and transmit power to the probe assembly. The pressure head of the probe assembly extends in the radial direction of the borehole to press against the hole wall. The depth of the pressure head entering the borehole, the flow rate and pressure parameters of the hydraulic oil are collected in real time through the data acquisition system. Finally, the critical (maximum) pressure Pm (critical load) of the rock wall is tested and converted into the uniaxial compressive strength of the surrounding rock through calculation.

[0009] The hydraulic power system includes a hydraulic hand pump and an automatic hose reel. A hose is wound around the automatic hose reel. Two high-pressure oil pipes are arranged inside the hose. One end of the two high-pressure oil pipes are respectively connected to the two interfaces of the hydraulic hand pump, and one end of the two high-pressure oil pipes are respectively connected to the probe assembly.

[0010] The data acquisition system includes a data recorder, a signal receiver, a flow meter, a pressure sensor and a meter counter. The flow meter and the pressure sensor are connected to one of the high-pressure oil pipes. The meter counter is installed at the outlet of the automatic hose reel. The hose bypasses the meter counter. The output ends of the flow meter, the pressure sensor and the meter counter are all connected to the input end of the signal receiver, and the output ends of the signal receiver are all connected to the input end of the data recorder.

[0011] The probe assembly includes an outer sleeve, a curved guide head is provided at the front end of the outer sleeve, a pressure conversion mechanism and a hydraulic cylinder are provided in the outer sleeve from front to back in sequence, a piston is slidably provided in the cylinder body of the hydraulic cylinder, the piston divides the inner cavity of the cylinder body into a front oil chamber and a rear oil chamber, the front end of the piston is connected to a piston rod extending forward from the front end of the cylinder body, the rear end of the cylinder body is connected to an extension oil inlet pipe joint connected to the rear oil chamber, the front end of the cylinder body is connected to a return oil inlet pipe parallel to the cylinder body, a fixing cover that is snapped and threadedly connected to the rear port of the outer sleeve is installed on the extension oil inlet pipe joint, a locking nut that compresses the front end surface of the fixing cover is threadedly connected to the extension oil inlet pipe joint, the return oil inlet pipe passes forward through the fixing cover and is connected to the return oil inlet pipe joint, the extension oil inlet pipe joint is connected to a high-pressure oil pipe installed with a flow meter and a pressure sensor, and the return oil inlet pipe joint is connected to another high-pressure oil pipe; a threaded hole that is threadedly connected to the front end of the push rod is provided on the fixing cover.

[0012] The pressure conversion mechanism includes a cylindrical block coaxially arranged with the outer sleeve, a radial hole is opened in the cylindrical block along the radial direction, a stud is coaxially arranged in the radial hole, the outer circle of the stud is threadedly connected with an internal threaded sleeve, the outer circles at both ends of the internal threaded sleeve are rotatably connected with the inner circle of the radial hole through two bearings, the outer circle of the internal threaded sleeve is an external gear structure between the two bearings, an axial hole penetrating the radial hole is opened in the cylindrical block along the front-to-back direction, a rack meshing with the external gear structure is penetrated in the axial hole, the cross section of the rack is semicircular, and a gear is fixed at the rear end of the rack A circular guide plate is slidably connected to the inner circle of the outer sleeve, and the front end of the piston rod is hinged to the rear end of the circular guide plate. An internal threaded hole is threadedly opened at one end of the stud along the length direction, and the internal thread of the internal threaded hole is connected to the pressure head. A through hole corresponding to the pressure head is opened on the outer sleeve, and a rectangular hole is opened at the other end of the stud along the length direction. A rotation-limiting guide strip extending into the rectangular hole is provided on the cylindrical block, and a dust-proof gasket and a spring retaining ring are provided at one end of the inner circle of the radial hole adjacent to the pressure head. An internal threaded hole connected to the outer sleeve by screws is opened on the outer circle of the cylindrical block on one side adjacent to the rotation-limiting guide strip.

[0013] The step S1 of connecting the hydraulic power system with the data acquisition system specifically includes: installing a flow meter and a pressure sensor on a high-pressure oil pipe, and using a data cable to connect the flow meter, the pressure sensor and the meter to a signal receiver respectively.

[0014] In step S2, the hydraulic power system is connected to the probe assembly in the following specific steps: two high-pressure oil pipes are connected to the extension oil inlet pipe joint and the return oil inlet pipe joint respectively after bypassing the meter.

[0015] In step S3, the front end of the push rod is connected to the rear end of the probe assembly by extending the front end of the push rod into and threading it into the threaded hole on the fixing cover.

[0016] The specific process of step S4 is: extend the probe assembly into the borehole, align the rear end of the outer sleeve with the borehole, set the drilling depth to zero on the data recorder, and then operate the push rod to slowly push the probe assembly into the borehole. The hose drives the meter installed on the automatic hose reel to rotate. The angle encoder on the meter recorder records the number of revolutions and angles of the meter wheel. Combined with the circumference of the meter wheel, the depth of the probe assembly into the borehole can be obtained.

[0017] The specific process of step S5 is: first, fill the hydraulic pipeline and the cavity in the hydraulic oil cylinder with hydraulic oil without leaving any bubbles; operate the hydraulic hand pump to press the hydraulic oil into the rear oil chamber of the cylinder body through the extension oil inlet pipe joint, and at the same time, the hydraulic oil in the front oil chamber of the cylinder body flows back to the hydraulic hand pump through the return oil inlet pipe, and the hydraulic oil forms a circulation loop, the piston moves from back to front in the cylinder body, the piston rod extends upward, the piston rod drives the rack to move forward, and the external gear structure meshing with the rack rotates, driving the internal threaded sleeve to rotate synchronously, and the stud threadedly connected to the internal threaded sleeve cannot rotate due to the restriction of the rotation limiting guide strip , so that the stud moves along the length direction, and the pressure head at the outer end of the stud extends out of the through hole on the outer sleeve. The flow meter records the hydraulic oil flow in this process, which is converted into the extension displacement of the pressure head after calculation. After the pressure head extends, it contacts the borehole wall. The hydraulic manual pump is continuously controlled to increase the pressure at a uniform speed until the rock is broken under the action of the pressure head. At this time, the pressure value transmitted by the pressure sensor is seen to drop suddenly on the screen of the data recorder. Through this phenomenon, it is judged that the maximum pressure measured by the pressure sensor is the critical (maximum) pressure Pm (critical load) of the rock wall. Through calculation, the rock strength at this point is obtained; Then operate the hydraulic hand pump to return oil from the rear oil chamber of the cylinder body and allow oil to flow into the front oil chamber of the cylinder body, so that the pressure head retracts into the outer sleeve, and rotates the push rod to drive the entire probe assembly to rotate an angle. According to the above operation process, multiple points of the same depth of the borehole are tested. For the contact points of the pressure head at the same depth, the average value of the rock strength of multiple contact points is converted as the uniaxial compressive strength of the rock at that level; Then, the hydraulic hand pump is operated to return oil from the rear oil chamber of the cylinder and allow oil to enter the front oil chamber of the cylinder, so that the pressure head retracts into the outer sleeve. The push rod is operated to move the entire probe assembly deeper or out along the borehole to measure the uniaxial compressive strength of rocks at different depths.

[0018] Using the above technical solution, the working principle of the in-situ rock strength test of the present invention is as follows: drill a hole in the rock mass that needs to be tested or directly use an engineering hole for pressure relief and drilling, and use the probe assembly to pressurize the borehole wall for testing. Under the action of the hydraulic oil, the hydraulic cylinder pushes the piston rod to extend, and the rack moves with the piston rod, driving the internal threaded sleeve with an external gear structure to rotate. The outer circle of the stud is threadedly connected to the internal threaded sleeve. Since the stud is constrained from rotating by the rotation-limiting guide strip, the screw can only move in the radial direction of the borehole. The screw drives the spherical pressure head to extend outward and contact the hole wall. It continues to be pressurized at an appropriate speed through the hydraulic pump, and the volume of hydraulic oil passing through the flowmeter is measured to convert the displacement of the pressure head extension. Combined with the hydraulic oil pressure collected by the pressure sensor, a pressure-displacement curve is generated (such as Figure 1 ). When the borehole rock wall breaks under the action of the pressure head, the pressure collected by the pressure sensor will suddenly drop. Figure 1 The peak point D1 before the decline in the critical (maximum) pressure P is recorded. m (critical load) and displacement of the indenter, thus obtaining the strength data of the rock. Through laboratory testing of a large number of coal-bearing rocks, P m The relationship between the rock compressive strength or elastic modulus can indirectly obtain the rock compressive strength value tested in situ. Figure 2 is the uniaxial compressive strength of rock R c —Critical load P m Relationship diagram, Figure 3 It is a relationship diagram of elastic modulus E-displacement pressure slope k in the elastic deformation stage. After each test, the data recorder will record the critical oil pressure value, pressure head displacement value and rock strength. Combined with the test position of the pressure head read from the angle encoder on the meter (the depth in the borehole), a set of data can be generated, namely the rock strength at a certain depth of the borehole and the pressure-displacement curve during the test. After a point test is completed, the rock strength of different depths of the same borehole, different points at the same depth, and different boreholes can be tested in situ to determine the changes in the strength of each section of the rock formation in the borehole. By increasing the density of measuring points, the contact surface between rock formations, the range of fracture zones, etc. can also be determined.

[0019] The present invention has significant improvements as follows: (1) The test equipment is lightweight, the probe assembly has a small diameter (<50 mm), and is applicable to a wide range of conditions. It can be taken directly to the site for in-situ testing. No sampling is required during the test process, which can avoid the impact of the sampling process on the properties of the rock and ensure the original state of the rock.

[0020] (2) It is suitable for the needs of underground working environment. The density of measuring points can be adjusted according to the on-site conditions to test the strength of surrounding rock in a large area of ​​tunnels, which can better reflect the actual situation on site.

[0021] (3) The test can be carried out continuously, and a large area of ​​the test can be performed on multiple points in the borehole.

[0022] (4) The test method is fast and economical. It reduces the process and cost of drilling holes and taking cores downhole and then bringing them back to the laboratory for uniaxial compression testing, thus shortening the test cycle.

[0023] (5) It can be used to measure the surrounding rock strength under different lithologies, different water contents, different confining pressures and water pressures.

[0024] (6) Ability to test data at different depths and points in one borehole; (7) The measured results, including the drilling depth, the strength of the rock wall at that depth, and the ejection displacement of the indenter, can be displayed in real time on the display screen of the data recorder. The measured data can also be stored, recorded, exported, replayed, and classified for management.

[0025] (8) By analyzing the rock strength of different boreholes and different depths, the rock properties of the tunnel roof can be estimated, which can help the tunnel support design. This device can measure different boreholes, different depths, and different points at the same depth, greatly improving the measurement efficiency of the tunnel surrounding rock strength and saving manpower and material costs. The device is easy to install and operate, with low learning costs and economical and efficient.

[0026] In summary, the present invention realizes the in-situ measurement of the surrounding rock strength of underground tunnels, and can perform rapid in-situ testing of the surrounding rock in real time and accurately without affecting normal construction and with almost zero damage to the surrounding rock of the excavated tunnel. A variety of physical and mechanical parameters in their original state can be obtained at the construction site and without disturbing or substantially disturbing the rock formation, providing a reliable quantitative basis for tunnel support design. It can meet the needs of the underground working environment and conduct tests in boreholes larger than 42 mm. The test device has a simple structure and is easy to operate, and the test data can better reflect the in-situ rock strength. It can measure the rock strength of different boreholes, different depths, and different points, so as to obtain the distribution of the rock strength of the tunnel, and the measurement results are relatively close to the on-site rock mass. The measurement process is simple and convenient, avoiding problems in the sampling process, etc., greatly improving the measurement efficiency, reducing the measurement cost, and having a good promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 yes Figure 1 Exploded view of the probe assembly; Figure 3 yes Figure 2 Left side view of the medium pressure conversion mechanism; Figure 4 yes Figure 3 Middle AA section view; Figure 5 It is an exploded diagram of the pressure conversion mechanism; Figure 6 Schematic diagram of the structure of the hydraulic cylinder; Figure 7 is a schematic diagram of the probe assembly during in-situ testing in a borehole; Figure 8 yes Figure 7 Enlarged view of middle part I; Fig. 9 It is the pressure-displacement curve diagram of the in-situ test process; Fig.10 is the uniaxial compressive strength of rock R c —Critical load P m Relationship diagram; Fig.11 It is a relationship diagram between rock elastic modulus E and displacement pressure slope k in the elastic deformation stage. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and examples.

[0029] like Figure 1-Figure 8 As shown, the rock strength in-situ testing method based on the borehole wall penetration method of the present invention comprises the following steps: S1. Connect the hydraulic power system to the data acquisition system; S2, connecting the hydraulic power system to the probe assembly 2; S3, connecting the front end of the push rod 1 to the rear end of the probe assembly 2; S4, operating the push rod 1 to push the probe assembly 2 into the borehole 3; S5. Start the hydraulic power system and transmit power to the probe assembly 2. The pressure head of the probe assembly 2 extends in the radial direction of the borehole 3 to press against the hole wall. The depth of the pressure head entering the borehole 3, the flow rate and pressure parameters of the hydraulic oil are collected in real time through the data acquisition system. Finally, the critical (maximum) pressure Pm (critical load) of the rock wall is tested and converted into the uniaxial compressive strength of the surrounding rock through calculation.

[0030] The hydraulic power system includes a hydraulic manual pump 4 and an automatic hose reel 5. A hose 6 is wound around the automatic hose reel 5. Two high-pressure oil pipes 7 are arranged inside the hose 6. One end of the two high-pressure oil pipes 7 are respectively connected to the two interfaces of the hydraulic manual pump 4, and one end of the two high-pressure oil pipes 7 are respectively connected to the probe assembly 2.

[0031] The data acquisition system includes a data recorder 8, a signal receiver 9, a flow meter 10, a pressure sensor 11 and a meter counter 12. The flow meter 10 and the pressure sensor 11 are connected to one of the high-pressure oil pipes 7. The meter counter 12 is installed at the outlet of the automatic hose reel 5. The hose 6 bypasses the meter counter 12. The output ends of the flow meter 10, the pressure sensor 11 and the meter counter 12 are all connected to the input end of the signal receiver 9, and the output ends of the signal receiver 9 are all connected to the input end of the data recorder 8.

[0032] The probe assembly 2 includes an outer sleeve 13, a curved guide head 14 is provided at the front end of the outer sleeve 13, a pressure conversion mechanism 15 and a hydraulic cylinder 16 are provided in the outer sleeve 13 from front to back, a piston 17 is slidably provided in the cylinder body of the hydraulic cylinder 16, and the piston 17 divides the inner cavity of the cylinder body into a front oil chamber and a rear oil chamber, a piston rod 19 extending forward from the front end of the cylinder body 18 is connected to the front end of the piston 17, a reach oil inlet pipe joint 20 connected to the rear oil chamber is connected to the rear end of the cylinder body 18, and a return oil inlet pipe 21 parallel to the cylinder body 18 is connected to the front end of the cylinder body 18. The oil pipe joint 20 is equipped with a fixing cover 22 which is snapped and threadedly connected to the rear port of the outer sleeve 13; the extension oil inlet pipe joint 20 is threadedly connected with a locking nut 23 which compresses the front end surface of the fixing cover 22; the return oil inlet pipe 21 passes forward through the fixing cover 22 and is connected with a return oil inlet pipe joint 24; the extension oil inlet pipe joint 20 is connected to a high-pressure oil pipe 7 on which a flow meter 10 and a pressure sensor 11 are installed, and the return oil inlet pipe joint 24 is connected to another high-pressure oil pipe 7; the fixing cover 22 is provided with a threaded hole which is threadedly connected to the front end of the push rod 1.

[0033] The pressure conversion mechanism 15 includes a cylindrical block 25 coaxially arranged with the outer sleeve 13, a radial hole 26 is opened inside the cylindrical block 25 in the radial direction, a stud 27 is coaxially arranged inside the radial hole 26, the outer circle of the stud 27 is threadedly connected with an internal threaded sleeve 28, the outer circles at both ends of the internal threaded sleeve 28 are rotatably connected with the inner circle of the radial hole 26 through two bearings 29, the outer circle of the internal threaded sleeve 28 is an external gear structure 30 between the two bearings 29, the cylindrical block 25 is opened with an axial hole 31 penetrating the radial hole 26 in the front-to-back direction, a rack 32 meshing with the external gear structure 30 is penetrated in the axial hole 31, the cross section of the rack 32 is semicircular, and the rear end of the rack 32 is fixed A circular guide plate 33 is provided that is slidably connected to the inner circle of the outer sleeve 13, the front end of the piston rod 19 is hinged to the rear end of the circular guide plate 33, one end of the stud 27 is threadedly opened with an internal threaded hole along the length direction, and the internal threaded hole is threadedly connected to the above-mentioned pressure head 34, the outer sleeve 13 is provided with a through hole corresponding to the pressure head 34, the other end of the stud 27 is provided with a rectangular hole along the length direction, the cylindrical block is provided with a rotation-limiting guide strip 35 extending into the rectangular hole, the inner circle of the radial hole 26 is provided with a dustproof gasket 36 and a spring retaining ring 37 at one end adjacent to the pressure head 34, and the outer circle of the cylindrical block 25 is provided with an internal threaded hole 39 connected to the outer sleeve 13 by a screw 38 on one side adjacent to the rotation-limiting guide strip 35.

[0034] The step S1 of connecting the hydraulic power system with the data acquisition system is as follows: the flow meter 10 and the pressure sensor 11 are installed on a high-pressure oil pipe 7, and the flow meter 10, the pressure sensor 11 and the meter 12 are respectively connected to the signal receiver 9 using data cables.

[0035] In step S2, the hydraulic power system is connected to the probe assembly 2 in the following specific steps: the two high-pressure oil pipes 7 are connected to the extension oil inlet pipe joint 20 and the return oil inlet pipe joint 24 respectively after bypassing the meter 12.

[0036] In step S3 , the front end of the push rod 1 is connected to the rear end of the probe assembly 2 by extending the front end of the push rod 1 into the threaded hole on the fixing cover 22 and threading the threaded hole.

[0037] The specific process of step S4 is: extend the probe assembly 2 into the opening of the borehole 3, align the rear end of the outer sleeve 13 with the opening, set the depth of the borehole 3 to zero on the data recorder 8, and then operate the push rod 1 to slowly push the probe assembly 2 into the borehole 3, the hose 6 drives the meter 12 installed on the automatic hose reel 5 to rotate, and the angle encoder on the meter 12 records the number of revolutions and angles of the meter wheel. Combined with the circumference of the meter wheel, the depth of the probe assembly 2 into the borehole 3 can be obtained.

[0038] The specific process of step S5 is as follows: first, the hydraulic pipeline and the cavity in the hydraulic oil cylinder 16 are filled with hydraulic oil without leaving any bubbles; the hydraulic manual pump 4 is operated to press the hydraulic oil into the rear oil chamber of the cylinder body 18 through the extension oil inlet pipe joint 20, and at the same time, the hydraulic oil in the front oil chamber of the cylinder body 18 flows back to the hydraulic manual pump 4 through the return oil inlet pipe 21, and the hydraulic oil forms a circulation loop, the piston 17 moves from the back to the front in the cylinder body 18, the piston rod 19 extends upward, and the piston rod 19 drives the rack 32 to move forward, and the external gear structure 30 meshing with the rack 32 rotates, driving the internal threaded sleeve 28 to rotate synchronously, and the stud 27 threadedly connected to the internal threaded sleeve 28 is limited by the rotation limiting guide strip 35. The control cannot rotate, so that the stud 27 moves along the length direction, and the pressure head 34 at the outer end of the stud 27 extends out of the through hole on the outer sleeve 13. The flow meter 10 records the hydraulic oil flow rate in this process, which is converted into the extension displacement of the pressure head 34 after calculation. After the pressure head 34 extends, it contacts the wall of the borehole 3, and the hydraulic manual pump 4 is continuously controlled to pressurize at a uniform speed until the rock is broken under the action of the pressure head 34. At this time, the pressure value transmitted by the pressure sensor 11 is seen on the screen of the data recorder 8. The phenomenon of a sudden drop in the pressure value is seen on the screen of the data recorder 8. Through this phenomenon, it is judged that the maximum pressure measured by the pressure sensor 11 is the critical (maximum) pressure Pm (critical load) of the rock wall. Through calculation, the rock strength at this point is obtained; Then, the hydraulic hand pump 4 is operated to return oil from the rear oil chamber of the cylinder 18 and allow oil to flow into the front oil chamber of the cylinder 18, so that the pressure head 34 is retracted into the outer sleeve 13, and the push rod 1 is rotated to drive the entire probe assembly 2 to rotate by an angle. According to the above operation process, multiple points of the same depth of the borehole 3 are tested. For the contact points of the pressure head 34 at the same depth, the average value of the rock strength of the multiple contact points is converted as the uniaxial compressive strength of the rock at that level; Then, the hydraulic hand pump 4 is operated to return oil from the rear oil chamber of the cylinder 18 and allow oil to flow into the front oil chamber of the cylinder 18, so that the pressure head 34 is retracted into the outer sleeve 13. The push rod 1 is operated to further deepen or pull the entire probe assembly 2 along the borehole 3 to measure the uniaxial compressive strength of rocks at different depths.

[0039] In summary, the working principle of the in-situ rock strength test of the present invention is summarized as follows: drill a hole 3 in the rock mass to be tested or directly use an engineering hole for pressure relief and drilling, and use the probe assembly 2 to pressurize the wall of the hole 3 for testing. Under the action of the hydraulic oil, the hydraulic cylinder 16 pushes the piston rod 19 to extend, and the rack 32 moves with the piston rod 19, driving the internal threaded sleeve 28 with the external gear structure 30 to rotate. The outer circle of the stud 27 is threadedly connected to the internal threaded sleeve 28. Since the stud 27 is constrained from rotating by the rotation-limiting guide strip 35, the screw can only move in the radial direction of the borehole 3. The screw drives the spherical pressure head 34 to extend outward and contact the hole wall. It continues to be pressurized at an appropriate speed through the hydraulic pump, and the volume of hydraulic oil passing through the flowmeter 10 is measured to convert the displacement of the pressure head 34. Combined with the hydraulic oil pressure collected by the pressure sensor 11, a pressure-displacement curve is generated (such as Fig. 9 ). When the rock wall of the borehole 3 is broken under the action of the pressure head 34, the pressure collected by the pressure sensor 11 will suddenly drop, that is, Fig. 9 The peak point D1 before the decline in the critical (maximum) pressure P is recorded. m (critical load) and the displacement of the pressure head 34, thereby obtaining the strength data of the rock. Through laboratory testing of a large number of coal-bearing rocks, P m The relationship between the rock compressive strength or elastic modulus can indirectly obtain the rock compressive strength value tested in situ. Fig.10 is the uniaxial compressive strength of rock R c —Critical load P m The relationship diagram, Fig.11It is a relationship diagram of elastic modulus E-displacement pressure slope k in the elastic deformation stage. After each test, the data recorder 8 will record the critical oil pressure value, the displacement value of the pressure head 34 and the strength of the rock. Combined with the test position of the pressure head 34 read from the angle encoder on the meter 12 (the depth in the borehole 3), a set of data can be generated, namely the rock strength at a certain depth of the borehole 3 and the pressure-displacement curve during the test. After a point test is completed, the rock strength of different depths of the same borehole 3, different points at the same depth, and different boreholes 3 can be tested in situ to determine the changes in the strength of each section of the rock formation in the borehole 3. By increasing the density of the measuring points, the contact surface between the rock formations, the range of the fracture zone, etc. can also be determined.

[0040] The above embodiments illustrate the basic principles and features of the present invention, but the above only illustrates the preferred embodiments of the present invention and is not limited to the embodiments. Under the inspiration of this patent, a person skilled in the art can make many forms of deformation and improvement without departing from the scope of protection of the present invention and the claims, which are all within the protection scope of the present invention. Therefore, the patent and protection scope of the present invention shall be subject to the attached claims.

Claims

1. The in-situ rock strength testing method based on the borehole wall penetration method is characterized by: The following steps are involved: S1. Connect the hydraulic power system to the data acquisition system; S2, connecting the hydraulic power system to the probe assembly; S3, connecting the front end of the push rod to the rear end of the probe assembly; S4, operate the push rod to push the probe assembly into the borehole; S5. Start the hydraulic power system and transmit power to the probe assembly. The pressure head of the probe assembly extends in the radial direction of the borehole to press against the hole wall. The depth of the pressure head entering the borehole, the flow rate and pressure parameters of the hydraulic oil are collected in real time through the data acquisition system. Finally, the critical (maximum) pressure Pm (critical load) of the rock wall is tested and converted into the uniaxial compressive strength of the surrounding rock through calculation.

2. The in-situ rock strength testing method based on the borehole penetration method according to claim 1 is characterized in that: The hydraulic power system includes a hydraulic hand pump and an automatic hose reel. A hose is wound around the automatic hose reel. Two high-pressure oil pipes are arranged inside the hose. One end of the two high-pressure oil pipes are respectively connected to the two interfaces of the hydraulic hand pump, and one end of the two high-pressure oil pipes are respectively connected to the probe assembly.

3. The in-situ rock strength testing method based on the borehole penetration method according to claim 2 is characterized in that: The data acquisition system includes a data recorder, a signal receiver, a flow meter, a pressure sensor and a meter counter. The flow meter and the pressure sensor are connected to one of the high-pressure oil pipes. The meter counter is installed at the outlet of the automatic hose reel. The hose bypasses the meter counter. The output ends of the flow meter, the pressure sensor and the meter counter are all connected to the input end of the signal receiver, and the output ends of the signal receiver are all connected to the input end of the data recorder.

4. The in-situ rock strength testing method based on the borehole penetration method according to claim 3 is characterized in that: The probe assembly includes an outer sleeve, a curved guide head is provided at the front end of the outer sleeve, a pressure conversion mechanism and a hydraulic cylinder are provided in the outer sleeve from front to back in sequence, a piston is slidably provided in the cylinder body of the hydraulic cylinder, the piston divides the inner cavity of the cylinder body into a front oil chamber and a rear oil chamber, the front end of the piston is connected to a piston rod extending forward from the front end of the cylinder body, the rear end of the cylinder body is connected to an extension oil inlet pipe joint connected to the rear oil chamber, the front end of the cylinder body is connected to a return oil inlet pipe parallel to the cylinder body, a fixing cover that is snapped and threadedly connected to the rear port of the outer sleeve is installed on the extension oil inlet pipe joint, a locking nut that compresses the front end surface of the fixing cover is threadedly connected to the extension oil inlet pipe joint, the return oil inlet pipe passes forward through the fixing cover and is connected to the return oil inlet pipe joint, the extension oil inlet pipe joint is connected to a high-pressure oil pipe installed with a flow meter and a pressure sensor, and the return oil inlet pipe joint is connected to another high-pressure oil pipe; a threaded hole that is threadedly connected to the front end of the push rod is provided on the fixing cover.

5. The in-situ rock strength testing method based on the borehole penetration method according to claim 4 is characterized in that: The pressure conversion mechanism includes a cylindrical block coaxially arranged with the outer sleeve, a radial hole is opened in the cylindrical block along the radial direction, a stud is coaxially arranged in the radial hole, the outer circle of the stud is threadedly connected with an internal threaded sleeve, the outer circles at both ends of the internal threaded sleeve are rotatably connected with the inner circle of the radial hole through two bearings, the outer circle of the internal threaded sleeve is an external gear structure between the two bearings, an axial hole penetrating the radial hole is opened in the cylindrical block along the front-to-back direction, a rack meshing with the external gear structure is penetrated in the axial hole, the cross section of the rack is semicircular, and a gear is fixed at the rear end of the rack A circular guide plate is slidably connected to the inner circle of the outer sleeve, and the front end of the piston rod is hinged to the rear end of the circular guide plate. An internal threaded hole is threadedly opened at one end of the stud along the length direction, and the internal thread of the internal threaded hole is connected to the pressure head. A through hole corresponding to the pressure head is opened on the outer sleeve, and a rectangular hole is opened at the other end of the stud along the length direction. A rotation-limiting guide strip extending into the rectangular hole is provided on the cylindrical block, and a dust-proof gasket and a spring retaining ring are provided at one end of the inner circle of the radial hole adjacent to the pressure head. An internal threaded hole connected to the outer sleeve by screws is opened on the outer circle of the cylindrical block on one side adjacent to the rotation-limiting guide strip.

6. The in-situ rock strength testing method based on the borehole penetration method according to claim 5 is characterized in that: The step S1 of connecting the hydraulic power system with the data acquisition system specifically includes: installing a flow meter and a pressure sensor on a high-pressure oil pipe, and using a data cable to connect the flow meter, the pressure sensor and the meter to a signal receiver respectively.

7. The in-situ rock strength testing method based on the borehole penetration method according to claim 5 is characterized in that: In step S2, the hydraulic power system is connected to the probe assembly in the following specific steps: two high-pressure oil pipes are connected to the extension oil inlet pipe joint and the return oil inlet pipe joint respectively after bypassing the meter.

8. The in-situ rock strength testing method based on the borehole penetration method according to claim 5 is characterized in that: In step S3, the front end of the push rod is connected to the rear end of the probe assembly by extending the front end of the push rod into and threading it into the threaded hole on the fixing cover.

9. The in-situ rock strength testing method based on the borehole penetration method according to claim 5 is characterized in that: The specific process of step S4 is: extend the probe assembly into the borehole, align the rear end of the outer sleeve with the borehole, set the drilling depth to zero on the data recorder, and then operate the push rod to slowly push the probe assembly into the borehole. The hose drives the meter installed on the automatic hose reel to rotate. The angle encoder on the meter recorder records the number of revolutions and angles of the meter wheel. Combined with the circumference of the meter wheel, the depth of the probe assembly into the borehole can be obtained.

10. The in-situ rock strength testing method based on the borehole penetration method according to claim 5 is characterized in that: The specific process of step S5 is: first, fill the hydraulic pipeline and the cavity in the hydraulic oil cylinder with hydraulic oil without leaving any bubbles; operate the hydraulic hand pump to press the hydraulic oil into the rear oil chamber of the cylinder body through the extension oil inlet pipe joint, and at the same time, the hydraulic oil in the front oil chamber of the cylinder body flows back to the hydraulic hand pump through the return oil inlet pipe, and the hydraulic oil forms a circulation loop, the piston moves from back to front in the cylinder body, the piston rod extends upward, the piston rod drives the rack to move forward, and the external gear structure meshing with the rack rotates, driving the internal threaded sleeve to rotate synchronously, and the stud threadedly connected to the internal threaded sleeve cannot rotate due to the restriction of the rotation limiting guide strip , so that the stud moves along the length direction, and the pressure head at the outer end of the stud extends out of the through hole on the outer sleeve. The flow meter records the hydraulic oil flow in this process, which is converted into the extension displacement of the pressure head after calculation. After the pressure head extends, it contacts the borehole wall. The hydraulic manual pump is continuously controlled to increase the pressure at a uniform speed until the rock is broken under the action of the pressure head. At this time, the pressure value transmitted by the pressure sensor is seen to drop suddenly on the screen of the data recorder. Through this phenomenon, it is judged that the maximum pressure measured by the pressure sensor is the critical (maximum) pressure Pm (critical load) of the rock wall. Through calculation, the rock strength at this point is obtained; Then operate the hydraulic hand pump to return oil from the rear oil chamber of the cylinder body and allow oil to flow into the front oil chamber of the cylinder body, so that the pressure head retracts into the outer sleeve, and rotates the push rod to drive the entire probe assembly to rotate an angle. According to the above operation process, multiple points of the same depth of the borehole are tested. For the contact points of the pressure head at the same depth, the average value of the rock strength of multiple contact points is converted as the uniaxial compressive strength of the rock at that level; Then, the hydraulic hand pump is operated to return oil from the rear oil chamber of the cylinder and allow oil to enter the front oil chamber of the cylinder, so that the pressure head retracts into the outer sleeve. The push rod is operated to move the entire probe assembly deeper or out along the borehole to measure the uniaxial compressive strength of rocks at different depths.

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