Automatic control system and method for rock mass in-situ direct shear test

Abstract

The invention provides an automatic control system and method for a rock mass in-situ direct shear test. The automatic control system comprises a test piece normal loading unit, a test piece horizontal loading unit, a test piece normal data acquisition and pressure control unit, a test piece horizontal data acquisition and pressure control unit and a main control terminal. According to the automatic control system and method for the rock mass in-situ direct shear test, test equipment such as the main control terminal, the electronic dial indicator, the oil pressure sensor and the electric oil pressure pump is used; according to a clear peak strength estimation standard formula, an encryption discrimination standard before the horizontal shear stress reaches the peak strength, an actual peak strength quantitative discrimination formula of the horizontal stress in the test process and boundary conditions, and according to specific execution steps of an automatic program, an automatic control flow of the rock mass in-situ direct shear test is realized; tedious personnel labor is saved, and the test efficiency and the test automation degree are improved.

Description

Technical Field

[0001] The invention is applicable to the technical fields of engineering geology in-situ measurement such as hydropower, water conservancy, transportation, geological disaster prevention and control, and mining, and specifically relates to an automatic control system and method for in-situ direct shear test of rock mass. Background Art

[0002] Engineering geological survey and design require the acquisition of rock shear strength parameters in the engineering area. On-site in-situ rock shear test is the most direct, accurate and closest to actual working conditions method to obtain rock shear strength parameters.

[0003] In traditional in-situ direct shear tests on rock, test personnel control the hydraulic oil pump and jack to apply normal stress and horizontal shear stress to the specimen, and special test personnel read the normal stress, horizontal shear stress and displacement values. Since the tests are generally carried out in exploration tunnels, the damp, dusty and silty environment of the tunnels and the poor lighting facilities all affect the reliability and accuracy of the results of in-situ direct shear tests on rock. Summary of the invention

[0004] In view of the defects in the prior art, the present invention provides an automatic control system and method for an in-situ direct shear test of rock mass, which can effectively solve the above problems.

[0005] The technical solution adopted by the present invention is as follows:

[0006] The present invention provides an automatic control system for an in-situ direct shear test of a rock mass, comprising a specimen normal loading unit (1), a specimen horizontal loading unit (2), a specimen normal data acquisition and pressure control unit (3), a specimen horizontal data acquisition and pressure control unit (4) and a main control terminal (5);

[0007] The specimen normal loading unit (1) is arranged between the top surface of the rock specimen (6) and the upper mortar (7) directly above it, and is used to apply normal stress to the top surface of the rock specimen (6);

[0008] The specimen horizontal loading unit (2) is arranged between the side wall of the rock specimen (6) and the side mortar (8) on the side thereof, and is used to apply horizontal stress to the side wall of the rock specimen (6);

[0009] The specimen normal data acquisition and pressure control unit (3) is connected to the specimen normal loading unit (1) and is used to control the specimen normal loading unit (1) to apply a normal stress value to the top surface of the rock specimen (6), and to acquire the normal stress value and the normal displacement of the rock specimen (6);

[0010] The specimen horizontal data acquisition and pressure control unit (4) is connected to the specimen horizontal loading unit (2) and is used to control the specimen horizontal loading unit (2) to apply a horizontal stress value of the horizontal stress to the side wall of the rock specimen (6), and to collect the horizontal stress value and the horizontal displacement of the rock specimen (6);

[0011] The main control terminal (5) is connected to the specimen normal data acquisition and pressure control unit (3) and the specimen horizontal data acquisition and pressure control unit (4) respectively, and is used to obtain the normal stress value, the horizontal stress value, the normal displacement of the rock specimen (6) and the horizontal displacement of the rock specimen (6) in real time during the in-situ direct shear test of the rock mass, and to control the pressure control units in the specimen normal data acquisition and pressure control unit (3) and the specimen horizontal data acquisition and pressure control unit (4).

[0012] Preferably, the specimen normal loading unit (1) comprises a roller row (1-1), a first steel pad (1-2), a first hydraulic jack (1-3) and a force transmission column (1-4);

[0013] Between the top surface of the rock specimen (6) and the upper mortar (7) directly above it, the roller row (1-1), the first steel pad (1-2), the first hydraulic jack (1-3) and the force transfer column (1-4) are arranged in sequence from bottom to top, and the bottom of the force transfer column (1-4) is snap-connected with the top surface of the first hydraulic jack (1-3), so that the top of the force transfer column (1-4) is in close contact with the upper mortar (7).

[0014] Preferably, the top surface of the rock specimen (6), the roller row (1-1), the first steel pad (1-2), the first hydraulic jack (1-3) and the force transmission column (1-4) are coaxially arranged; and the cross-sections of the roller row (1-1) and the first steel pad (1-2) are the same, smaller than the top surface of the rock specimen (6) and larger than the cross-section of the first hydraulic jack (1-3).

[0015] Preferably, the specimen normal data acquisition and pressure control unit (3) comprises a first electric oil pump (3-1), a first oil pressure sensor (3-2), a first DC battery pack (3-3), an oil inlet and return pipe (3-4) of the first electric oil pump, an oil inlet and return nozzle (3-5) of the first electric oil pump, and a normal displacement acquisition device (3-6);

[0016] The oil inlet and return pipe (3-4) of the first electric oil pump (3-1) is connected to the oil inlet and return nozzle (3-5) of the first electric oil pump of the first hydraulic jack (1-3), and is used to control the normal stress value applied by the first hydraulic jack (1-3);

[0017] The first oil pressure sensor (3-2) is used to collect the normal stress value in real time;

[0018] The first DC battery pack (3-3) is used to supply power to the first electric oil pump (3-1);

[0019] The normal displacement acquisition device (3-6) is used to acquire the normal displacement of the rock mass specimen (6) in real time.

[0020] Preferably, the specimen horizontal loading unit (2) comprises a second steel pad (2-1), a thrust steel pad (2-2) and a second hydraulic jack (2-3);

[0021] The second hydraulic jack (2-3) is arranged horizontally, and its axis and the bottom surface of the rock specimen (6) are located in the same horizontal plane; the base of the second hydraulic jack (2-3) is against the side mortar (8), and the thrust steel pad (2-2) and the second steel pad (2-1) are arranged in sequence between the output end of the second hydraulic jack (2-3) and the side wall of the rock specimen (6).

[0022] Preferably, the second steel backing plate (2-1) is attached to the side wall of the rock specimen (6) and has the same height as the side wall of the rock specimen (6), so as to completely cover the side wall of the rock specimen (6);

[0023] The height of the thrust steel pad (2-2) is lower than the height of the second steel pad (2-1), and the bottom surface of the thrust steel pad (2-2) and the bottom surface of the rock mass specimen (6) are located on the same horizontal plane;

[0024] Therefore, the output end of the second hydraulic jack (2-3), the thrust steel pad (2-2) and the second steel pad (2-1) are in a stepped form with gradually increasing top surface heights.

[0025] Preferably, the specimen horizontal data acquisition and pressure control unit (4) comprises a second electric oil pump (4-1), a second oil pressure sensor (4-2), a second DC battery pack (4-3), an oil inlet and return pipe (4-4) of the second electric oil pump, an oil inlet and return nozzle (4-5) of the second electric oil pump, and a horizontal displacement acquisition device (4-6);

[0026] The oil inlet and return pipe (4-4) of the second electric oil pump (4-1) is connected to the oil inlet and return nozzle (4-5) of the second electric oil pump of the second hydraulic jack (2-3), and is used to control the horizontal stress value applied by the second hydraulic jack (2-3);

[0027] The second oil pressure sensor (4-2) is used to collect the horizontal stress value in real time;

[0028] The second DC battery pack (4-3) is used to supply power to the second electric oil pump (4-1);

[0029] The horizontal displacement acquisition device (4-6) is used to acquire the horizontal displacement of the rock mass specimen (6) in real time.

[0030] The present invention also provides a method for an automatic control system of a rock mass in-situ direct shear test, comprising the following steps:

[0031] Step S1, equipment installation and measurement system status confirmation;

[0032] Step S2, preparation before the test: selecting the test type, including rock mass in-situ direct shear test and rock mass in-situ direct shear test friction test;

[0033] Step S3, input key parameters: In this test, the constant normal stress value σ applied to the specimen yu , specimen shear area, shear angle normal and shear direction jack output coefficient; using formula (1), the estimated value of horizontal shear stress peak τ is obtained max :

[0034] τ max = kσ yu (1)

[0035] Where: k is the estimated coefficient, which is determined according to the test type; if it is an in-situ direct shear test on rock mass, k is 1.5; if it is an in-situ direct shear test friction test on rock mass, k is 1;

[0036] Step S4, confirm key parameters and start the test;

[0037] Step S5, according to the set key parameters, the specimen normal loading unit (1) is controlled to apply a constant normal stress to the top surface of the rock specimen (6), and the normal stress value is σ yu ;

[0038] Step S6, judging whether the normal stress is stable. When the normal stress is stable, executing step S7;

[0039] Step S7, controlling the specimen horizontal loading unit (2) so as to apply horizontal shear stress to the side wall of the rock specimen (6), and the specific control method for applying the horizontal shear stress is:

[0040] Step S7.1, using formula (2), according to the estimated value of the horizontal shear stress peak τ max The horizontal shear stress is applied step by step and judged to be stable. At the same time, the horizontal shear stress and shear displacement are collected in real time, and the horizontal shear stress-shear displacement curve is generated in real time.

[0041]

[0042] Where: τ n is the nth level shear stress; τ n-1 is the n-1th level horizontal shear stress; n is the level number, starting from 1 and increasing. When n = 1, τ n-1 =τ0=0;Δτ n is the difference between the nth and n-1th level horizontal shear stress;

[0043] Step S7.2, in the process of applying horizontal shear stress step by step in the manner of step S7.1, it is determined in real time whether the shear displacement increment of this stage reaches 1.5 times the shear displacement increment of the previous stage, that is, whether formula (3) is established:

[0044] Δs n =1.5Δs n-1 (3)

[0045] in:

[0046] Δs n is the nth level shear displacement increment, that is, the current level shear displacement increment; Δs n-1 is the n-1th level shear displacement increment, that is, the previous level shear displacement increment;

[0047] If formula (3) is not true, continue to execute step S7.1; if formula (3) is true, execute step S7.3;

[0048] Step S7.3, starting from applying horizontal shear stress at the n+1th level, the level difference is halved, that is, a new level difference is obtained according to formula (4), and then horizontal shear stress is applied step by step with the new level difference and stability is determined;

[0049]

[0050] Where: τ n+1 is the n+1th level horizontal shear stress; Δτ n+1 is the difference between the horizontal shear stress of level n+1 and level n, and is the new difference;

[0051] Step S7.4, in the process of applying horizontal shear stress step by step with a new step difference, if the shear displacement increment of the current stage increases again to 1.5 times the shear displacement increment of the previous stage before reaching the horizontal shear peak stress determined in step S8, the horizontal shear stress increment applied at the next stage is further halved compared with the horizontal shear stress increment applied at the current stage, until the horizontal shear stress increment is less than 0.1Mpa, and step S7.5 is executed;

[0052] The formula is:

[0053] When Δs n+m =1.5Δs n+m-1 When

[0054] in:

[0055] Δs n+m is the shear displacement increment of the n+mth level;

[0056] Δs n+m-1 is the shear displacement increment of the n+m-1th level;

[0057] Δτ n+m+1 is the horizontal shear stress increment of level n+m+1;

[0058] Δτ n+m is the horizontal shear stress increment of the n+mth level;

[0059] τ n+m+1 is the horizontal shear stress of level n+m+1;

[0060] τ n+m is the horizontal shear stress of the n+mth level;

[0061] Step S7.5, assuming that the n+xth level shear stress increment Δτ n+x <0.1Mpa, then the n+x+1th level horizontal shear stress increment Δτ n+x+1 =0.1Mpa, therefore, the n+x+1th level horizontal shear stress τ n+x+1 =τ n+x +0.1MPa, where τ n+x is the n+xth level horizontal shear stress; then with a step difference of 0.1Mpa, that is, the new step difference is 0.1Mpa at this time, the horizontal shear stress is applied step by step with the new step difference until the horizontal shear peak stress determined in step S8 appears;

[0062] Step S8, in the process of applying horizontal shear stress in the manner of step S7, the horizontal shear peak stress determination standard is:

[0063] (1) If the specimen belongs to the type of rock mass that undergoes brittle shear failure: the horizontal shear stress of this level is lower than the horizontal shear stress of the previous level, the horizontal shear stress of the previous level is higher than the horizontal shear stress of the previous level, and the value of the decrease in the horizontal shear stress of this level is 2 times or more of the value of the increase in the horizontal shear stress of the previous level, then the horizontal shear stress of the previous level is determined to be the peak horizontal shear stress;

[0064] (2) If the specimen belongs to the type of rock mass that undergoes plastic shear failure: within any 60 s interval, the horizontal shear stress fluctuates within a certain range, and the fluctuation range is ±0.05 MPa. The average value of the horizontal shear stress during this period is determined as the horizontal shear peak stress;

[0065] (3) If the specimens subjected to direct shear test do not belong to the rock mass type that undergoes brittle shear failure or plastic shear failure, when the total horizontal shear displacement reaches 15 mm, the average value of the five levels of shear data before and after the maximum horizontal shear stress within 15 mm is taken as the horizontal shear peak stress;

[0066] Step S9, after obtaining the horizontal shear peak stress through step S8, the horizontal shear stress is applied in subsequent tests with shear displacement control, and the horizontal shear stress shear displacement data is recorded every time the shear displacement increases by 0.50 mm until the total shear displacement exceeds 35 mm, and the test is terminated.

[0067] The automatic control system and method for in-situ direct shear test of rock mass provided by the present invention have the following advantages:

[0068] The present invention provides an automatic control system and method for an in-situ direct shear test of a rock mass. By using a main control terminal, an electronic dial indicator, an oil pressure sensor, an electric oil pressure pump and other test equipment, according to a clear peak strength estimation standard formula, an encrypted judgment standard before the horizontal shear stress reaches the peak strength, a quantitative judgment formula for the actual peak strength of the horizontal stress during the test and boundary conditions, and in accordance with the specific execution steps of the automatic program, an automatic control process of the in-situ direct shear test of the rock mass is realized, tedious labor is eliminated, and the test efficiency and the degree of automation of the test are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 The overall diagram of the automatic control system for the in-situ direct shear test of rock mass provided by the present invention;

[0070] Figure 2 A schematic diagram of the installation positions of the normal electronic dial gauge and the horizontal electronic dial gauge provided by the present invention;

[0071] Figure 3 A flow chart of the automatic control method for in-situ direct shear test of rock mass provided by the present invention;

[0072] Figure 4 A schematic diagram of the stress-strain relationship of a specimen that undergoes brittle shear failure in the automatic control method for in-situ direct shear testing of rock mass provided by the present invention;

[0073] Figure 5 A schematic diagram of the stress-strain relationship of a specimen undergoing plastic shearing in the automatic control method for in-situ direct shear test of rock mass provided by the present invention.

[0074] in:

[0075] Specimen normal loading unit 1; specimen horizontal loading unit 2; specimen normal data acquisition and pressure control unit 3; specimen horizontal data acquisition and pressure control unit 4; main control terminal 5; rock specimen 6; upper mortar 7; side mortar 8; reinforced concrete protective shell 9; displacement measurement mark 10; force diagram 11;

[0076] Roller row 1-1; first steel pad 1-2; first hydraulic jack 1-3; force transmission column 1-4; second steel pad 2-1; thrust steel pad 2-2; second hydraulic jack 2-3; first electric oil pump 3-1; first oil pressure sensor 3-2; first DC battery pack 3-3; oil inlet and return pipes 3-4 of the first electric oil pump; oil inlet and return nozzles 3-5 of the first electric oil pump; normal displacement acquisition device 3-6; second electric oil pump 4-1; second oil pressure sensor 4-2; second DC battery pack 4-3; oil inlet and return pipes 4-4 of the second electric oil pump; oil inlet and return nozzles 4-5 of the second electric oil pump; horizontal displacement acquisition device 4-6;

[0077] The first normal electronic percentage meter A1; the second normal electronic percentage meter A2; the third normal electronic percentage meter A3; the fourth normal electronic percentage meter A4; the first horizontal electronic percentage meter B1; the second horizontal electronic percentage meter B2; the third horizontal electronic percentage meter B3; the fourth horizontal electronic percentage meter B4. DETAILED DESCRIPTION

[0078] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0079] In the description of the present invention, it is necessary to understand that the orientations or positional relationships indicated by terms such as "upper end", "lower end", "outside", "two ends", "middle" and "bottom" are orientations or positional relationships based on the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or device referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0080] In the present invention, unless otherwise clearly specified and limited, the terms "layout", "installation", "equipped with", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0081] The present invention discloses an automatic control system and method for in-situ direct shear test of rock mass, which clarifies the specific parameters and functions of the automatic control test equipment for in-situ direct shear test of rock mass, quantifies the standard formula for estimating the peak strength of horizontal shear stress, provides the encrypted judgment standard before the horizontal shear stress reaches the peak strength, proposes the quantitative judgment formula and boundary conditions for the actual peak strength of the horizontal shear stress during the test, lists the specific execution steps of the automatic program in detail, and provides a complete automatic control process and full-process method for in-situ direct shear test of rock mass. The present invention is applicable to the in-situ measurement technology fields of hydropower, water conservancy, transportation, geological disaster prevention and control, mining and other engineering geological survey sites, especially in-situ direct shear test of rock mass at the engineering geological survey site.

[0082] The automated control process and method proposed in the present invention solve the problems of large number of personnel, low efficiency, and large human influence factors, such as the need for test personnel to apply normal stress and horizontal shear stress to the test piece through a hydraulic oil pump and a jack in the traditional in-situ direct shear test of rock mass, the need for a dedicated person to monitor the normal stress pressure gauge during the shearing process, and the need for 4 to 6 test personnel to read and record the normal, horizontal stress values ​​and displacement values ​​at all times.

[0083] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0084] The present invention provides an automatic control system and method for in-situ direct shear test of rock mass, quantifies the peak estimation formula of horizontal shear stress, provides the encrypted judgment standard before the horizontal shear stress reaches the peak strength, proposes the actual peak strength quantitative judgment formula and boundary conditions of the horizontal shear stress during the test, lists the specific execution steps of the automatic program in detail, and provides a complete automatic control process and full test process method of in-situ direct shear test of rock mass. By adopting the automatic control system and method for in-situ direct shear test of rock mass provided by the present invention, through the communication between the main control terminal 5 and the specimen normal data acquisition and pressure control unit 3 and the specimen horizontal data acquisition and pressure control unit 4, the in-situ direct shear test of rock mass can be carried out efficiently and accurately, and the reliability and accuracy of the in-situ direct shear test of rock mass can be improved.

[0085] The detailed technical scheme of the present invention is as follows:

[0086] See also Figure 1 and Figure 2 The present invention provides an automatic control system for in-situ direct shear test of rock mass, including a specimen normal loading unit 1, a specimen horizontal loading unit 2, a specimen normal data acquisition and pressure control unit 3, a specimen horizontal data acquisition and pressure control unit 4 and a main control terminal 5;

[0087] The specimen normal loading unit 1 is arranged between the top surface of the rock specimen 6 and the upper mortar 7 directly above it, and is used to apply normal stress to the top surface of the rock specimen 6;

[0088] The specimen horizontal loading unit 2 is arranged between the side wall of the rock specimen 6 and the side mortar 8 on the side thereof, and is used to apply horizontal stress to the side wall of the rock specimen 6;

[0089] The specimen normal data acquisition and pressure control unit 3 is connected to the specimen normal loading unit 1, and is used to control the specimen normal loading unit 1 to apply the normal stress value of the normal stress to the top surface of the rock specimen 6, and to collect the normal stress value and the normal displacement of the rock specimen 6;

[0090] The specimen horizontal data acquisition and pressure control unit 4 is connected to the specimen horizontal loading unit 2, and is used to control the specimen horizontal loading unit 2 to apply horizontal stress to the side wall of the rock specimen 6, and to collect the horizontal stress value and the horizontal displacement of the rock specimen 6;

[0091] The main control terminal 5 is connected to the specimen normal data acquisition and pressure control unit 3 and the specimen horizontal data acquisition and pressure control unit 4 respectively, and is used to obtain the normal stress value, horizontal stress value, normal displacement of the rock specimen 6 and horizontal displacement of the rock specimen 6 in the in-situ direct shear test of the rock mass in real time, and control the pressure control units in the specimen normal data acquisition and pressure control unit 3 and the specimen horizontal data acquisition and pressure control unit 4.

[0092] As a preferred embodiment, the specimen normal loading unit 1 includes a roller row 1-1, a first steel pad 1-2, a first hydraulic jack 1-3 and a force transmission column 1-4;

[0093] Between the top surface of the rock specimen 6 and the upper mortar 7 directly above it, the roller row 1-1, the first steel pad 1-2, the first hydraulic jack 1-3 and the force transmission column 1-4 are arranged in sequence from bottom to top, and the bottom of the force transmission column 1-4 is connected with the top surface of the first hydraulic jack 1-3 by clamping, so that the top of the force transmission column 1-4 and the upper mortar 7 are in close contact. As a preferred embodiment, the top surface of the rock specimen 6, the roller row 1-1, the first steel pad 1-2, the first hydraulic jack 1-3 and the force transmission column 1-4 are arranged coaxially; and the cross-sections of the roller row 1-1 and the first steel pad 1-2 are the same, smaller than the top surface of the rock specimen 6, and larger than the cross-section of the first hydraulic jack 1-3. With this structure, the normal stress of the first hydraulic jack 1-3 can be more effectively transmitted to the top surface of the rock specimen 6.

[0094] As a preferred embodiment, the specimen normal data acquisition and pressure control unit 3 includes a first electric oil pump 3-1, a first oil pressure sensor 3-2, a first DC battery pack 3-3, an oil inlet and return pipe 3-4 of the first electric oil pump, an oil inlet and return nozzle 3-5 of the first electric oil pump, and a normal displacement acquisition device 3-6;

[0095] The first electric oil pump inlet and return oil pipe 3-4 of the first electric oil pump 3-1 is connected to the first electric oil pump inlet and return oil nozzle 3-5 of the first hydraulic jack 1-3, and is used to control the normal stress value applied by the first hydraulic jack 1-3;

[0096] The first oil pressure sensor 3-2 is used to collect the normal stress value in real time; the first DC battery pack 3-3 is used to supply power to the first electric oil pump 3-1; the normal displacement collection device 3-6 is used to collect the normal displacement of the rock specimen 6 in real time.

[0097] As a preferred embodiment, the specimen horizontal loading unit 2 includes a second steel pad 2-1, a thrust steel pad 2-2 and a second hydraulic jack 2-3;

[0098] The second hydraulic jack 2-3 is arranged horizontally, and its axis and the bottom surface of the rock specimen 6 are located in the same horizontal plane; the base of the second hydraulic jack 2-3 is against the side mortar 8, and the thrust steel plate 2-2 and the second steel plate 2-1 are arranged in sequence between the output end of the second hydraulic jack 2-3 and the side wall of the rock specimen 6.

[0099] As a preferred embodiment, the second steel plate 2-1 is attached to the side wall of the rock specimen 6, with the same height as the side wall of the rock specimen 6, and completely covers the side wall of the rock specimen 6;

[0100] The height of the thrust steel pad 2-2 is lower than that of the second steel pad 2-1, and the bottom surface of the thrust steel pad 2-2 and the bottom surface of the rock specimen 6 are located at the same horizontal plane;

[0101] Therefore, the output end of the second hydraulic jack 2-3, the thrust steel pad 2-2 and the second steel pad 2-1 are in a stepped form with gradually increasing top surface heights. With this structure, the horizontal stress of the second hydraulic jack 2-3 can be more effectively transferred to the side wall of the rock specimen 6.

[0102] As a preferred embodiment, the specimen horizontal data acquisition and pressure control unit 4 includes a second electric oil pump 4-1, a second oil pressure sensor 4-2, a second DC battery pack 4-3, an oil inlet and return pipe 4-4 of the second electric oil pump, an oil inlet and return nozzle 4-5 of the second electric oil pump, and a horizontal displacement acquisition device 4-6;

[0103] The oil inlet and return pipe 4-4 of the second electric oil pump 4-1 is connected to the oil inlet and return nozzle 4-5 of the second electric oil pump of the second hydraulic jack 2-3, and is used to control the horizontal stress value applied by the second hydraulic jack 2-3;

[0104] The second oil pressure sensor 4-2 is used for collecting horizontal stress values ​​in real time; the second DC battery pack 4-3 is used for supplying power to the second electric oil pump 4-1; the horizontal displacement collection device 4-6 is used for collecting horizontal displacement of the rock specimen 6 in real time.

[0105] The present invention provides an automatic control system for in-situ direct shear test of rock mass, the key equipment of which includes a main control terminal 5, an electronic dial indicator, an oil pressure sensor, an electric oil pump, etc., wherein:

[0106] The main control terminal 5 should be shockproof, drop-proof and fall-proof, with a protection level of IP65, a battery life of not less than 24h under normal working conditions, a screen size of not less than 7 inches, an internal storage of ≥3G+32G, and carry WIFI and 4G modules;

[0107] Electronic dial indicator, range 0~50mm, graduation value 0.01mm, accuracy ≤0.1%FS, return error ±0.01mm, protection grade IP67, continuous endurance time under working condition>24 hours, with wireless transmission and automatic connection after disconnection function, its power should be displayed with icon or percentage, when the power is insufficient during the test, there must be sound or light prompting insufficient power, the performance of the meter should be stable and reliable; in the present invention, if Figure 2 As shown, there are four normal electronic percentage indicators and four horizontal electronic percentage indicators, namely: the first normal electronic percentage indicator A1; the second normal electronic percentage indicator A2; the third normal electronic percentage indicator A3; the fourth normal electronic percentage indicator A4; the first horizontal electronic percentage indicator B1; the second horizontal electronic percentage indicator B2; the third horizontal electronic percentage indicator B3; and the fourth horizontal electronic percentage indicator B4.

[0108] Oil pressure sensor, anti-vibration, range 0-60MPa, oil pressure sensor accuracy 0.2, graduation value should not be greater than 0.1MPa, protection level IP65;

[0109] The electric oil pump should be DC driven, with a rated output pressure of 0 to 60 MPa and a rated flow rate of 0.1 to 1 L / min. During the pressurization process, uniform pressurization should be ensured, and the pressurization rate should not be too fast. "Pressure inertia" is not allowed, that is, the pressure surges and exceeds the set value due to the excessively fast pressurization rate.

[0110] See also Figure 3 The present invention also provides a method for an automatic control system for an in-situ direct shear test of a rock mass, comprising the following steps:

[0111] Step S1, equipment installation and measurement system status confirmation;

[0112] Test equipment according to Figure 1 Install according to Figure 2 Schematic diagram, eight electronic dial indicators are installed in corresponding positions, four of which measure the displacement in the normal direction (vertical direction) and horizontal shear direction respectively, and assembled and debugged. When applying shear stress, the normal stress applied to the specimen should be kept unchanged. The main control terminal 5 controls the normal stress to a constant value through the first oil pressure sensor 3-2, each normal electronic dial indicator and the first electric oil pump 3-1 in real time. The main control terminal 5 controls the horizontal shear stress through the second oil pressure sensor 4-2, each horizontal electronic dial indicator and the second electric oil pump 4-1 at the same time, that is, the main control terminal 5 can communicate with the specimen normal data acquisition and pressure control unit 3 and the specimen horizontal data acquisition and pressure control unit 4 at the same time to carry out in-situ direct shear test of rock mass.

[0113] Step S2, preparation before the test: selecting the test type, including rock mass in-situ direct shear test and rock mass in-situ direct shear test friction test;

[0114] Step S3, input key parameters:

[0115] Specifically, after debugging the equipment, according to Figure 3 The execution block diagram of the automatic control process starts the test; first enter the project name, flat tunnel, pilot number and other information, then enter the equipment related parameters, including the oil pressure sensor number, rolling friction resistance, jack output coefficient, etc., and then enter the key test parameters including the shear area of ​​the specimen and the applied directional stress.

[0116] Specifically, the key parameters include: In this test, the constant normal stress value σ applied to the specimen yu , specimen shear area, shear angle normal and shear direction jack output coefficient; using formula (1), the program automatically calculates and estimates the estimated value of the horizontal shear stress peak τmax :

[0117] τ max = kσ yu (1)

[0118] Where: k is the estimated coefficient, which is determined according to the test type; if it is an in-situ direct shear test of rock mass, k is generally taken as 1.5; if it is an in-situ direct shear test friction test of rock mass, k is generally taken as 1;

[0119] Therefore, in the present invention, the estimated value of the horizontal shear stress peak is quantified by formula (1).

[0120] Step S4, confirm key parameters and start the test;

[0121] Step S5, according to the set key parameters, the specimen normal loading unit 1 is controlled to apply a constant normal stress to the top surface of the rock specimen 6, and the normal stress value is σ yu ;

[0122] Specifically, when applying horizontal shear stress in the subsequent steps, the normal stress applied to the specimen should be kept unchanged and be a constant value. Specifically, the main control terminal 5 controls the normal stress to be a constant value by real-time pressure increase and unloading through the first oil pressure sensor 3-2, each normal electronic dial indicator and the first electric oil pump 3-1; and the main control terminal 5 simultaneously controls the application of horizontal shear stress through the second oil pressure sensor 4-2, each horizontal electronic dial indicator and the second electric oil pump 4-1, that is, the main control terminal 5 can communicate with the specimen normal data acquisition and pressure control unit 3 and the specimen horizontal data acquisition and pressure control unit 4 at the same time to conduct in-situ direct shear test of rock mass.

[0123] Step S6, judging whether the normal stress is stable. When the normal stress is stable, executing step S7;

[0124] Step S7, the specimen horizontal loading unit 2 is controlled to apply horizontal shear stress to the side wall of the rock specimen 6. The specific control method for applying the horizontal shear stress is:

[0125] Step S7.1, using formula (2), according to the estimated value of the horizontal shear stress peak τ max The horizontal shear stress is applied step by step and judged to be stable. At the same time, the horizontal shear stress and shear displacement are collected in real time, and the horizontal shear stress-shear displacement curve is generated in real time.

[0126]

[0127] Where: τ n is the nth level shear stress; τ n-1is the n-1th level horizontal shear stress; n is the level number, starting from 1 and increasing. When n = 1, τ n-1 =τ0=0;Δτ n is the difference between the nth and n-1th level horizontal shear stress;

[0128] Step S7.2, in the process of applying horizontal shear stress step by step in the manner of step S7.1, it is determined in real time whether the shear displacement increment of this stage reaches 1.5 times the shear displacement increment of the previous stage, that is, whether formula (3) is established:

[0129] Δs n =1.5Δs n-1 (3)

[0130] in:

[0131] Δs n is the nth level shear displacement increment, that is, the current level shear displacement increment; Δs n-1 is the n-1th level shear displacement increment, that is, the previous level shear displacement increment;

[0132] If formula (3) is not true, continue to execute step S7.1; if formula (3) is true, execute step S7.3;

[0133] Step S7.3, starting from applying horizontal shear stress at the n+1th level, the level difference is halved, that is, a new level difference is obtained according to formula (4), and then horizontal shear stress is applied step by step with the new level difference and stability is determined;

[0134]

[0135] Where: τ n+1 is the n+1th level horizontal shear stress; Δτ n+1 is the difference between the horizontal shear stress of level n+1 and level n, and is the new difference;

[0136] Step S7.4, in the process of applying horizontal shear stress step by step with a new step difference, if the shear displacement increment of the current stage increases again to 1.5 times the shear displacement increment of the previous stage before reaching the horizontal shear peak stress determined in step S8, the horizontal shear stress increment applied at the next stage is further halved compared with the horizontal shear stress increment applied at the current stage, until the horizontal shear stress increment is less than 0.1Mpa, and step S7.5 is executed;

[0137] The formula is:

[0138] When Δs n+m =1.5Δs n+m-1 When

[0139] in:

[0140] Δs n+m is the shear displacement increment of the n+mth level;

[0141] Δs n+m-1 is the shear displacement increment of the n+m-1th level;

[0142] Δτ n+m+1 is the horizontal shear stress increment of level n+m+1;

[0143] Δτ n+m is the horizontal shear stress increment of the n+mth level;

[0144] τ n+m+1 is the horizontal shear stress of level n+m+1;

[0145] τ n+m is the horizontal shear stress of the n+mth level;

[0146] Step S7.5, assuming that the n+xth level shear stress increment Δτ n+x <0.1Mpa, then the n+x+1th level horizontal shear stress increment Δτ n+x+1 =0.1Mpa, therefore, the n+x+1th level horizontal shear stress τ n+x+1 =τ n+x +0.1MPa, where τ n+x is the n+xth level horizontal shear stress; then with a step difference of 0.1Mpa, that is, the new step difference is 0.1Mpa at this time, the horizontal shear stress is applied step by step with the new step difference until the horizontal shear peak stress determined in step S8 appears;

[0147] This step S7 is an encrypted judgment standard before the horizontal shear stress reaches the horizontal shear peak strength, which can be summarized as:

[0148] (1) When horizontal shear stress is applied, the estimated value of the peak horizontal shear stress τ max 1 / 10 of the value is used as the step difference, and horizontal shear stress is applied step by step and judged to be stable;

[0149] The formula is:

[0150]

[0151] (2) When the shear displacement increment of this stage is 1.5 times that of the previous stage, the level difference of horizontal shear stress is halved;

[0152] The formula is: When Δs n =1.5Δs n-1 When τ n+1 =τ n +Δτ n+1 ; τ n+2 =τ n+1 +Δτ n+2 ;…;

[0153] (3) If the shear displacement increment of a certain stage increases to 1.5 times of the shear displacement increment of the previous stage before reaching the horizontal shear peak, the horizontal shear stress increment applied by the next stage will be halved compared with the horizontal shear stress increment of the current stage, until the horizontal shear stress increment is less than 0.1 MPa or the horizontal shear peak is reached;

[0154] The formula is:

[0155] When the shear displacement increment Δs of the n+mth level n+m =1.5Δs n+m-1 When , the horizontal shear stress increment of level n+m+1 is The horizontal shear stress τ of the n+m+1th level n+m+1 =τ n+m +Δτ n+m+1 ;

[0156] When the horizontal shear stress increment Δτ of the n+xth level n+x When <0.1Mpa, the horizontal shear stress increment Δτ of level n+x+1 n+x+1 =0.1Mpa, horizontal shear stress τ of level n+x+1 n+x+1 =τ n+x +0.1MPa.

[0157] Step S8, in the process of applying horizontal shear stress in the manner of step S7, the horizontal shear peak stress determination standard is:

[0158] (1) Figure 4 As shown, if the specimen belongs to the type of rock mass that undergoes brittle shear failure: the horizontal shear stress of this level is lower than the horizontal shear stress of the previous level, the horizontal shear stress of the previous level is higher than the horizontal shear stress of the previous level, and the value of the reduction of the horizontal shear stress of this level is 2 times or more of the value of the increase of the horizontal shear stress of the previous level, then the horizontal shear stress of the previous level is determined to be the horizontal shear peak stress;

[0159] The formula is:

[0160] When Δτ s <0,Δτ s-1 >0, and |Δτ s |≥2|Δτ s-1 |, then τ′ max =τ s-1 ;

[0161] Where: Δτ s Represents the difference between the horizontal shear stress of this level and the horizontal shear stress of the upper level;

[0162] Δτ s-1 Represents the difference between the upper level horizontal shear stress and the upper level horizontal shear stress;

[0163] τ s-1 represents the upper level shear stress;

[0164] τ′ mas represents the horizontal shear peak stress;

[0165] (2) Figure 5 As shown, if the specimen belongs to the type of rock mass that undergoes plastic shear failure: within a certain period of time, preferably 60s, the horizontal shear stress fluctuates within a certain range, with a fluctuation range of ±0.05MPa, then the average value of the horizontal shear stress during this period is determined as the horizontal shear peak stress;

[0166] The formula is:

[0167] When T n ≥T n-s +60, τ da =max{τ n-s ,τ n-s+1 ,τ n-s+2 ,...,τ n-1 ,τ n},τ xiao =min{τ n-s ,τ n-S+1 ,τ n-s+2 ,...,τ n-1 ,τ n},τ da -τ xiao ≤0.1MPa, then τ′ max =average{τ n-s ,τ n-s+1 ,τ n-s+2 ,...,τ n-1 ,τ n};

[0168] in:

[0169] For the time period of the nsth level, the n-s+1th level, …, the nth level, T n Represents the time of the nth level, T n-s Represents the time of the ns level, this time period is greater than or equal to 60s; τ n-s ,τ n-s+1 ,τ n-s+2 ,...,τ n-1 ,τ n Represents the horizontal shear stress corresponding to each time period;

[0170] (3) If the specimens subjected to direct shear test are not of the rock mass type that undergoes brittle shear failure or plastic shear failure, that is, if they are neither of the above two types: when the total horizontal shear displacement reaches 15 mm, the average value of the five levels of shear data before and after the maximum horizontal shear stress within 15 mm is taken as the horizontal shear peak stress;

[0171] The formula is:

[0172] When the cumulative horizontal shear displacement S from the 1st level to the kth level k ≥15mm, τ z =max{τ1,τ2,τ3,...,τ k-1 ,τ k}, then τ′ max =average{τ z-2 ,τ z-1 ,τ z ,τ z+1 ,τ z+2}, and 2<z≤k.

[0173] Where: τ z represents the maximum horizontal shear stress from level 1 to level k; therefore, the maximum horizontal shear stress is the horizontal shear stress of level z.

[0174] Step S9, after obtaining the horizontal shear peak stress through step S8, the horizontal shear stress is applied in subsequent tests with shear displacement control, and the horizontal shear stress shear displacement data is recorded every time the shear displacement increases by 0.50 mm until the total shear displacement exceeds 35 mm, and the test is terminated.

[0175] The formula is: When τ′ is obtained max After l+1 =s l +0.5mm; when the accumulated horizontal shear displacement S p ≥35mm, end the test.

[0176] The present invention provides an automatic control method for an in-situ direct shear test of a rock mass. Figure 3 The execution block diagram of the automatic control process of the in-situ direct shear test of rock mass is given in the figure. According to this process, the in-situ direct shear test of rock mass can be automatically completed. The specific process is as follows:

[0177] Step S1, equipment installation and measurement system status confirmation;

[0178] Step S2, preparation before the test: select the test type; input the project name, adit, pilot number and pile number, input the pressure sensor number, rolling friction resistance;

[0179] Step S3, key parameter input: input the shear area of ​​the specimen, the normal direction of the shear angle, the jack output coefficient in the shear direction, and the normal stress value, and automatically calculate and estimate the peak value of the horizontal shear stress;

[0180] Step S4: confirm the parameters and start the test; if the parameters need to be modified, return to step S3.

[0181] Step S5, normal load application: according to the set parameters, apply at level 3, and the process is carried out according to the specification;

[0182] Step S6, judging whether the normal stress is stable; if it is unstable, returning to step S4, popping up a manual adjustment interface, and modifying the normal stress value;

[0183] Step S7, horizontal shear stress application: after the normal stress loading is completed, the horizontal shear stress application interface will pop up with the option of pausing / confirming / modifying parameters. The tester confirms the estimated maximum loading horizontal shear peak stress for 15 seconds and directly enters the horizontal shear stress loading phase without any operation;

[0184] Step S8, applying horizontal shear stress step by step with a step difference of 1 / 10 of the estimated maximum horizontal shear stress value and judging stability, collecting stress and displacement data; generating a data record table stress-displacement curve in real time and being able to slide the screen to view monitoring;

[0185] Step S9, when the horizontal shear displacement increment is 1.5 times that of the previous stage, the horizontal shear stress difference is halved;

[0186] Step S10, applying horizontal shear stress with a new step difference (the new step difference should be greater than 0.1 MPa, otherwise the step difference is 0.1 MPa);

[0187] Step S11, satisfying one of the following three conditions to obtain the horizontal shear peak stress:

[0188] If the horizontal shear stress of this level is lower than the stress of the upper level, and the stress of the upper level is higher than the stress of the upper level, and the value of the stress reduction of this level is 2 times or more of the value of the stress increase of the upper level, then the upper level stress is determined to be the horizontal shear peak stress;

[0189] In any 60s interval, the horizontal shear stress fluctuates within a certain range, and the fluctuation range is ±0.05MPa. The average shear stress in the measuring period is determined as the peak strength stress.

[0190] When the total horizontal shear displacement reaches 15 mm, the maximum horizontal shear stress within 15 mm and the average value of the five groups of shear data before and after are taken as the horizontal shear peak value;

[0191] Step S12, after obtaining the horizontal shear peak stress, the subsequent test applies the horizontal shear stress by displacement control, and records the stress-displacement data every time the displacement increases by 0.50 mm until the total displacement exceeds 35 mm;

[0192] Step S13, post-test description: take photos of the upper and lower plates of the cut surface, the photos are named according to the test points and can be edited, and the post-test description is divided into upper and lower plates;

[0193] Step S14, the single point test ends.

[0194] Different from the traditional in-situ direct shear test method of rock mass, the test personnel need to load and unload vertical and horizontal stresses, record displacement and stress data, and determine the peak strength of horizontal shear to control the test process. The beneficial effect of the present invention is that by using the main control terminal, electronic dial indicator, oil pressure sensor, electric oil pressure pump and other test equipment, according to the clear peak strength estimation standard formula, the encrypted judgment standard before the horizontal shear stress reaches the peak strength, the actual peak strength quantitative judgment formula and boundary conditions of the horizontal stress during the test, according to the specific execution steps of the automatic program, the automatic control process of the in-situ direct shear test of rock mass is realized, which saves the tedious labor of personnel and improves the test efficiency and the degree of test automation.

[0195] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An automatic control system for in-situ direct shear test of rock mass, characterized in that: It comprises a specimen normal loading unit (1), a specimen horizontal loading unit (2), a specimen normal data acquisition and pressure control unit (3), a specimen horizontal data acquisition and pressure control unit (4) and a main control terminal (5); The specimen normal loading unit (1) is arranged between the top surface of the rock specimen (6) and the upper mortar (7) directly above it, and is used to apply normal stress to the top surface of the rock specimen (6); The specimen horizontal loading unit (2) is arranged between the side wall of the rock specimen (6) and the side mortar (8) on the side thereof, and is used to apply horizontal stress to the side wall of the rock specimen (6); The specimen normal data acquisition and pressure control unit (3) is connected to the specimen normal loading unit (1) and is used to control the specimen normal loading unit (1) to apply a normal stress value to the top surface of the rock specimen (6), and to acquire the normal stress value and the normal displacement of the rock specimen (6); The specimen horizontal data acquisition and pressure control unit (4) is connected to the specimen horizontal loading unit (2) and is used to control the specimen horizontal loading unit (2) to apply a horizontal stress value of the horizontal stress to the side wall of the rock specimen (6), and to collect the horizontal stress value and the horizontal displacement of the rock specimen (6); The main control terminal (5) is connected to the specimen normal data acquisition and pressure control unit (3) and the specimen horizontal data acquisition and pressure control unit (4) respectively, and is used to obtain the normal stress value, the horizontal stress value, the normal displacement of the rock specimen (6) and the horizontal displacement of the rock specimen (6) in real time during the in-situ direct shear test of the rock mass, and to control the pressure control units in the specimen normal data acquisition and pressure control unit (3) and the specimen horizontal data acquisition and pressure control unit (4).

2. The automatic control system for in-situ direct shear test of rock mass according to claim 1, characterized in that: The specimen normal loading unit (1) comprises a roller row (1-1), a first steel pad (1-2), a first hydraulic jack (1-3) and a force transmission column (1-4); Between the top surface of the rock specimen (6) and the upper mortar (7) directly above it, the roller row (1-1), the first steel pad (1-2), the first hydraulic jack (1-3) and the force transfer column (1-4) are arranged in sequence from bottom to top, and the bottom of the force transfer column (1-4) is snap-connected with the top surface of the first hydraulic jack (1-3), so that the top of the force transfer column (1-4) is in close contact with the upper mortar (7).

3. The automatic control system for in-situ direct shear test of rock mass according to claim 2, characterized in that: The top surface of the rock specimen (6), the roller row (1-1), the first steel pad (1-2), the first hydraulic jack (1-3) and the force transmission column (1-4) are coaxially arranged; and the cross-sections of the roller row (1-1) and the first steel pad (1-2) are the same, smaller than the top surface of the rock specimen (6) and larger than the cross-section of the first hydraulic jack (1-3).

4. The automatic control system for in-situ direct shear test of rock mass according to claim 2, characterized in that: The specimen normal data acquisition and pressure control unit (3) comprises a first electric oil pump (3-1), a first oil pressure sensor (3-2), a first DC battery pack (3-3), an oil inlet and return pipe (3-4) of the first electric oil pump, an oil inlet and return nozzle (3-5) of the first electric oil pump, and a normal displacement acquisition device (3-6); The oil inlet and return pipe (3-4) of the first electric oil pump (3-1) is connected to the oil inlet and return nozzle (3-5) of the first electric oil pump of the first hydraulic jack (1-3), and is used to control the normal stress value applied by the first hydraulic jack (1-3); The first oil pressure sensor (3-2) is used to collect the normal stress value in real time; The first DC battery pack (3-3) is used to supply power to the first electric oil pump (3-1); The normal displacement acquisition device (3-6) is used to acquire the normal displacement of the rock mass specimen (6) in real time.

5. The automatic control system for in-situ direct shear test of rock mass according to claim 1, characterized in that: The specimen horizontal loading unit (2) comprises a second steel pad (2-1), a thrust steel pad (2-2) and a second hydraulic jack (2-3); The second hydraulic jack (2-3) is arranged horizontally, and its axis and the bottom surface of the rock specimen (6) are located in the same horizontal plane; the base of the second hydraulic jack (2-3) is against the side mortar (8), and the thrust steel pad (2-2) and the second steel pad (2-1) are arranged in sequence between the output end of the second hydraulic jack (2-3) and the side wall of the rock specimen (6).

6. The automatic control system for in-situ direct shear test of rock mass according to claim 5, characterized in that: The second steel backing plate (2-1) is attached to the side wall of the rock specimen (6) at the same height as the side wall of the rock specimen (6), and completely covers the side wall of the rock specimen (6); The height of the thrust steel pad (2-2) is lower than the height of the second steel pad (2-1), and the bottom surface of the thrust steel pad (2-2) and the bottom surface of the rock mass specimen (6) are located on the same horizontal plane; Therefore, the output end of the second hydraulic jack (2-3), the thrust steel pad (2-2) and the second steel pad (2-1) are in a stepped form with gradually increasing top surface heights.

7. The automatic control system for in-situ direct shear test of rock mass according to claim 5, characterized in that: The specimen horizontal data acquisition and pressure control unit (4) comprises a second electric oil pump (4-1), a second oil pressure sensor (4-2), a second DC battery pack (4-3), an oil inlet and return pipe (4-4) of the second electric oil pump, an oil inlet and return nozzle (4-5) of the second electric oil pump, and a horizontal displacement acquisition device (4-6); The oil inlet and return pipe (4-4) of the second electric oil pump (4-1) is connected to the oil inlet and return nozzle (4-5) of the second electric oil pump of the second hydraulic jack (2-3), and is used to control the horizontal stress value applied by the second hydraulic jack (2-3); The second oil pressure sensor (4-2) is used to collect the horizontal stress value in real time; The second DC battery pack (4-3) is used to supply power to the second electric oil pump (4-1); The horizontal displacement acquisition device (4-6) is used to acquire the horizontal displacement of the rock mass specimen (6) in real time.

8. A method for an automatic control system for an in-situ direct shear test of a rock mass according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step S1, equipment installation and measurement system status confirmation; Step S2, preparation before the test: selecting the test type, including rock mass in-situ direct shear test and rock mass in-situ direct shear test friction test; Step S3, input key parameters: In this test, the constant normal stress value σ applied to the specimen yu , shear area of ​​the specimen, shear angle normal and jack output coefficient in the shear direction; Using formula (1), we can get the estimated value of the peak horizontal shear stress τ max : t max =kσ yu (1) Where: k is the estimated coefficient, which is determined according to the test type; if it is an in-situ direct shear test on rock mass, k is 1.5; if it is an in-situ direct shear test friction test on rock mass, k is 1; Step S4, confirm key parameters and start the test; Step S5, according to the set key parameters, the specimen normal loading unit (1) is controlled to apply a constant normal stress to the top surface of the rock specimen (6), and the normal stress value is σ yu ; Step S6, judging whether the normal stress is stable. When the normal stress is stable, executing step S7; Step S7, controlling the specimen horizontal loading unit (2) so as to apply horizontal shear stress to the side wall of the rock specimen (6), and the specific control method for applying the horizontal shear stress is: Step S7.1, using formula (2), according to the estimated value of the horizontal shear stress peak τ max The horizontal shear stress is applied step by step and judged to be stable. At the same time, the horizontal shear stress and shear displacement are collected in real time, and the horizontal shear stress-shear displacement curve is generated in real time. Where: τ n is the nth level shear stress; τ n-1 is the n-1th level horizontal shear stress; n is the level number, starting from 1 and increasing. When n = 1, τ n-1 =τ0=0;Δτ n is the difference between the nth and n-1th level horizontal shear stress; Step S7.2, in the process of applying horizontal shear stress step by step in the manner of step S7.1, it is determined in real time whether the shear displacement increment of this stage reaches 1.5 times the shear displacement increment of the previous stage, that is, whether formula (3) is established: Δs n =1.5Δs n-1 (3) in: Δs n is the nth level shear displacement increment, that is, the current level shear displacement increment; Δs n-1 is the n-1th level shear displacement increment, that is, the previous level shear displacement increment; If formula (3) is not true, continue to execute step S7.1; if formula (3) is true, execute step S7.3; Step S7.3, starting from applying horizontal shear stress at the n+1th level, the level difference is halved, that is, a new level difference is obtained according to formula (4), and then horizontal shear stress is applied step by step with the new level difference and stability is determined; Where: τ n+1 is the n+1th level horizontal shear stress; Δτ n+1 is the difference between the horizontal shear stress of level n+1 and level n, and is the new difference; Step S7.4, in the process of applying horizontal shear stress step by step with a new step difference, if the shear displacement increment of the current stage increases again to 1.5 times the shear displacement increment of the previous stage before reaching the horizontal shear peak stress determined in step S8, the horizontal shear stress increment applied at the next stage is further halved compared with the horizontal shear stress increment applied at the current stage, until the horizontal shear stress increment is less than 0.1Mpa, and step S7.5 is executed; The formula is: When Δs n+m = 1.5Δs n+m-1 then τ n+m+1 = τ n+m + Δτ n+m+1 ; in: Δs n+m is the shear displacement increment of the n+mth level; Δs n+m-1 is the shear displacement increment of the n+m-1th level; Δτ n+m+1 is the horizontal shear stress increment of level n+m+1; Δτ n+m is the horizontal shear stress increment of the n+mth level; τ n+m+1 is the horizontal shear stress of level n+m+1; τ n+m is the horizontal shear stress of the n+mth level; Step S7.5, assuming that the n+xth level shear stress increment Δτ n+x <0.1Mpa, then the n+x+1th level horizontal shear stress increment Δτ n+x+1 =0.1Mpa, therefore, the n+x+1th level horizontal shear stress τ n+x+1 =τ n+x +0.1MPa, where τ n+x is the n+xth level horizontal shear stress; then with a step difference of 0.1Mpa, that is, the new step difference is 0.1Mpa at this time, the horizontal shear stress is applied step by step with the new step difference until the horizontal shear peak stress determined in step S8 appears; Step S8, in the process of applying horizontal shear stress in the manner of step S7, the horizontal shear peak stress determination standard is: (1) If the specimen belongs to the type of rock mass that undergoes brittle shear failure: the horizontal shear stress of this level is lower than the horizontal shear stress of the previous level, the horizontal shear stress of the previous level is higher than the horizontal shear stress of the previous level, and the value of the decrease in the horizontal shear stress of this level is 2 times or more of the value of the increase in the horizontal shear stress of the previous level, then the horizontal shear stress of the previous level is determined to be the peak horizontal shear stress; (2) If the specimen belongs to the type of rock mass that undergoes plastic shear failure: within any 60 s interval, the horizontal shear stress fluctuates within a certain range, and the fluctuation range is ±0.05 MPa. The average value of the horizontal shear stress during this period is determined as the horizontal shear peak stress; (3) If the specimens subjected to direct shear test do not belong to the rock mass type that undergoes brittle shear failure or plastic shear failure, when the total horizontal shear displacement reaches 15 mm, the average value of the five levels of shear data before and after the maximum horizontal shear stress within 15 mm is taken as the horizontal shear peak stress; Step S9, after obtaining the horizontal shear peak stress through step S8, the horizontal shear stress is applied in subsequent tests with shear displacement control, and the horizontal shear stress shear displacement data is recorded every time the shear displacement increases by 0.50 mm until the total shear displacement exceeds 35 mm, and the test is terminated.

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