A field rock structural plane shearing test system and test method

Abstract

The present application relates to the field of rock mass structure plane mechanical test technology, and particularly relates to a field rock structure plane shearing test system and a test method, comprising a horizontally arranged test platform, a concrete encapsulating shell wrapped on a rock sample, a normal load loading system for applying a normal load on the top surface of the concrete encapsulating shell, a shearing load loading system for applying a shearing load on the side surface of the concrete encapsulating shell, and a data test acquisition system for measuring normal pressure, normal displacement and tangential displacement, wherein the normal load loading system and the shearing load loading system are both arranged on the test platform. The present application applies normal pressure and tangential pressure through the normal load loading system and the shearing load loading system respectively, and obtains relevant displacement parameters through the data test acquisition system with higher precision, so as to quantitatively evaluate and analyze the strength characteristics of the structure plane, and solve the problems of large occupation and low reliability existing in the traditional test method.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of in-situ rock mass structural plane mechanics test, in particular to an in-situ rock structural plane shearing test system and a test method. BACKGROUND

[0002] Because of the large number of discontinuous structural planes such as bedding, joints and fissures intersecting longitudinally and transversely in natural rock mass, complex rock mass characteristics are formed, and the determination of the mechanical parameters thereof is an important basis for the design of geotechnical engineering. The shear strength of rock-soil mass is one of the most important mechanical parameters in geotechnical engineering mechanics, and is related to many fields such as railway transportation, water conservancy and hydropower, urban construction and national defense construction. Therefore, obtaining the shear strength of rock mass structural plane is a key link for evaluating the stability of engineering rock mass and providing guidance for excavation and support of geotechnical engineering.

[0003] At present, the methods for rock mass shearing test are divided into indoor and in-situ methods. The indoor shearing test is a method for obtaining the shear strength parameters by using indoor shearing test equipment after transporting the rock mass sample obtained in-situ to the laboratory; and the in-situ rock mass shearing test is a method for obtaining the shear strength parameters of rock mass by processing the sample in-situ and loading in the normal and tangential directions.

[0004] Generally, the equipment used in the indoor shearing test includes upper and lower shearing boxes, a certain normal load is applied to the top of the shearing box in which the sample is placed, the shearing box is pushed to make the sample sheared to failure, and thus the strength parameters of rock mass are obtained. This method is simple, fast and easy to control the boundary conditions, but the physical and mechanical state of the sample is disturbed during sampling, transportation and test, and the sample size is small, so it is difficult to restore the real state of rock mass in-situ. The in-situ shearing test is carried out in the rock mass in-situ, and the vertical pressure is applied to the top plate through the force transmission column connected to the jack, which requires the test to be carried out in the chamber; in the open environment, the pressure on the test piece is generally applied by stacking and pressing through the cross beam and the jack. Although the test of large-size sample in-situ can reduce the influence of size effect and truly reflect the shear strength characteristics of rock mass, it still has the following shortcomings:

[0005] (1) The traditional in-situ pressure plate test method has a single way of providing counterforce, requires a large test site, the test equipment is bulky, the preparation process is complex, the cost is high, and the test period is long.

[0006] (2) The existing equipment has low degree of automation control, and the loading system is operated manually and the displacement is read manually, which leads to low accuracy and reliability of the obtained shear strength parameters of rock mass.

[0007] (3) Current in-situ shear test adopts rear edge excavation face as horizontal load reaction support, when high normal pressure acts, the rear edge support body is easy to be damaged in advance, resulting in test failure.

[0008] Therefore, it is of great significance to design a test system and a test method for accurately determining the shear strength parameters of the in-situ rock mass structure surface. SUMMARY

[0009] The present application aims to provide a shear test system and a test method for in-situ rock mass structure surface, which can at least solve some defects in the prior art.

[0010] To achieve the above-mentioned object, the technical scheme of the present application is a shear test system for in-situ rock mass structure surface, comprising a test platform arranged horizontally, a concrete envelope shell wrapped on a rock mass sample, a normal load loading system for applying a normal load on the top surface of the concrete envelope shell, a shear load loading system for applying a shear load on the side surface of the concrete envelope shell, and a data test acquisition system for measuring normal pressure, normal displacement and tangential displacement, wherein the normal load loading system and the shear load loading system are arranged on the test platform.

[0011] Further, the top surface of the rock mass sample is approximately parallel to the rock mass structure surface to be measured, the top surface of the concrete envelope shell is parallel to the rock mass structure surface to be measured, and the bottom surface of the concrete envelope shell is parallel to the rock mass structure surface to be measured and has a certain distance.

[0012] Further, the normal load loading system comprises a roller row, a normal load transmission steel plate, and a reaction loading device for applying a normal load on the normal load transmission steel plate, wherein the roller row is fixed on the bottom surface of the normal load transmission steel plate and is in contact with the top surface of the concrete envelope shell.

[0013] As an embodiment, the reaction loading device comprises a plurality of bored piles arranged around the concrete envelope shell, the bottom of the bored pile is embedded below the test platform, and the top of the bored pile is provided with a force transmission column; the normal load transmission steel plate is provided with a fixing hole corresponding to the position of the force transmission column, and the force transmission column penetrates through the corresponding fixing hole and is fixed to the normal load transmission steel plate by a bolt.

[0014] As another embodiment, the reaction loading device comprises a plurality of anchor rods arranged around the concrete envelope shell, the bottom of the anchor rod is embedded below the test platform, and the normal load transmission steel plate is provided with a fixing hole corresponding to the position of the anchor rod, and the top of the anchor rod penetrates through the corresponding fixing hole and is fixed to the normal load transmission steel plate by an anchor device.

[0015] Further, two sides of the normal load loading system are provided with a retaining system, the retaining system comprises a lateral support steel plate, a retaining main beam and a retaining secondary beam, one side of the top of the lateral support steel plate is closely combined with the normal load transmission steel plate, the other side of the top of the lateral support steel plate is connected with the top of the retaining main beam, the retaining main beam is obliquely arranged and the retaining main beam and the lateral support steel plate are connected through a plurality of retaining secondary beams, the bottom of the retaining main beam and the bottom of the lateral support steel plate are embedded below the test platform respectively.

[0016] Further, the shear load loading system comprises a shear load hydraulic jack, a tangential load transmission rigid plate, a jack support and a jack lateral support device; the jack support is arranged on the test platform, the fixed end of the shear load hydraulic jack is connected with the jack lateral support device and supported on the jack support, and the movable end of the shear load hydraulic jack is abutted on the side of the concrete envelope through the tangential load transmission rigid plate.

[0017] Further, the data test acquisition system comprises a data processing terminal, a normal distance measuring device for measuring normal displacement, a tangential distance measuring device for measuring tangential displacement and a normal pressure measuring device for measuring normal pressure; the normal distance measuring device, the tangential distance measuring device and the normal pressure measuring device are connected with the data processing terminal through data transmission wires respectively.

[0018] The application further provides a field rock structural plane shear test method, comprising the following steps:

[0019] S1, selecting a rock mass sample and determining a rock mass structural plane to be measured and a rock mass sample range involved, leveling a site around the rock mass sample to be measured, removing loose rocks on a surface layer of the rock mass sample to be measured, cutting and separating the rock mass around the rock mass sample to be measured and removing dregs;

[0020] S2, constructing the shear test system described above;

[0021] S3, applying a normal load in stages, immediately reading a normal displacement through the data test acquisition system after loading of each stage of normal load, and reading the normal displacement again after 5 minutes, taking a difference between the normal displacement read continuously for two times less than 0.01mm as a normal load stability standard, and applying a shear load after the normal load is stable;

[0022] S4, when the shear load is applied, the shear load is loaded every 5 minutes, the shear displacement and shear force data should be measured by the data test collection system before and after the shear load is applied, and the shear displacement and shear force should be measured densely before the peak value; After the rock structure surface is sheared, the load can be continued to be applied until the shear load value tends to be stable;

[0023] S5, according to the formula, the normal stress σ and shear force τ acting on the rock mass structure surface are calculated, the relationship curve between the shear force τ and the shear displacement and the normal displacement under different normal stress σ is drawn, and the peak shear stress and residual shear stress under different normal stress σ are calculated;

[0024] S6, the relationship curve between the normal stress σ and the corresponding peak shear stress and residual shear stress is drawn, and the corresponding shear strength parameters c and φ are calculated according to the Mohr-Coulomb expression.

[0025] Further, the calculation formula of the normal stress σ and the shear force τ in step S5 is as follows:

[0026] When the rock mass structure surface is horizontal,

[0027] N 总 =4N σ +N α (1-1)

[0028]

[0029]

[0030] Q=Q 推力 -Q 摩擦 (1-4)

[0031] In the formula, σ is the normal stress (MPa) acting on the rock mass structure surface;

[0032] τ is the shear stress (MPa) acting on the rock mass structure surface;

[0033] N 总 is the total normal load (N) acting on the rock mass structure surface;

[0034] N σ is the anchoring force (N) provided by the normal load loading system;

[0035] N α is the other load (N) in the normal direction;

[0036] Q is the total shear load (N) acting on the rock mass structure surface;

[0037] Q 推力 is the thrust (N) provided by the shear load loading system;

[0038] Q 摩擦 the friction force (N) between the normal load loading system and the concrete envelope shell when the normal stress is σ;

[0039] A—the area (m 2 ) of the rock mass structure surface;

[0040] When the rock mass structure surface is located on a gentle slope,

[0041] N 总 ′=4N σ +N α cos α (1-5)

[0042]

[0043] In the formula, α is the included angle (°) between the rock structure surface and the horizontal plane; the shear force τ received by the rock mass structure surface is calculated by formula 1-3.

[0044] Compared with the prior art, the present application has the following beneficial effects:

[0045] (1) The present application applies the normal load to the rock mass sample through the normal load loading system, applies the tangential load to the rock mass sample through the shear load loading system, and quickly and accurately obtains the relevant pressure and displacement parameters through the higher-precision data test acquisition system during the application of the normal load and the tangential load, so that the shear strength characteristics of the structure surface can be quantitatively evaluated and analyzed, the accuracy and reliability of the obtained rock mass shear strength parameters are improved, the test system integrates loading and shearing, the test equipment is simple, easy to operate, the test period is short, and the required test site is small.

[0046] (2) The test method of the present application has clear ideas, is easy to operate, and has strong repeatability, different reaction force loading devices can be selected according to the actual situation on site, and the relevant displacement parameters are obtained through the higher-precision laser ranging method, so that the strength characteristics of the structure surface can be quantitatively evaluated and analyzed, which has strong on-site operability, makes up for the defects of the current rock structure surface shear test method, solves the problems of large occupation and low reliability existing in the traditional test method, and can qualitatively and quantitatively evaluate the strength characteristics of the key rock structure surface, which has guiding significance for rock and soil engineering design and scheme optimization. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below only show some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0048] Figure 1 The structural schematic diagram of the in-situ rock structural plane shear test system provided by the embodiment of the present application (the pile foundation provides the counterforce);

[0049] Figure 2 The structural schematic diagram of the in-situ rock structural plane shear test system provided by the embodiment of the present application (the anchor rod provides the counterforce);

[0050] Figure 3 The bottom view of the normal load transmission steel plate provided by the embodiment of the present application;

[0051] In the figure: 1.1, the force transmission column; 1.2, the anchor rod; 2.1, the first bolt; 2.2, the anchorage device; 3.1, the pressure gauge; 3.2, the anchor cable gauge; 4.1, the second bolt; 4.2, the lateral support steel plate; 5.1, the nest groove; 5.2, the support main beam; 6.1, the cast-in-place pile; 6.2, the support secondary beam; 7.1, the pile body; 7.2, the anchor rod fixed end; 8, the roller shaft row; 9, the concrete envelope shell; 10, the rock mass sample; 11.1, the normal laser range finder; 11.2, the tangential laser range finder; 12.1, the normal range-finding positioning cursor; 12.2, the tangential range-finding positioning cursor; 13, the shear load hydraulic jack; 14, the tangential load transmission steel plate; 15, the hydraulic oil pump; 16, the jack support; 17, the jack support steel plate; 18, the jack lateral support; 19, the support secondary beam; 20, the support main beam; 21, the data transmission wire; 22, the normal load transmission steel plate; 23, the data processing terminal; 24, the fixed hole. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments only show some of the embodiments of the present application, and for those skilled in the art, all other embodiments obtained without creative labor on the basis of these drawings also belong to the scope of protection of the present application.

[0053] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0054] The terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features; in the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0055] Embodiment one

[0056] As shown in the Figures 1-2 The present embodiment provides a field rock structural plane shear test system, which comprises a test platform arranged horizontally, a concrete enclosing shell 9 wrapped around a rock sample 10, a normal load loading system for applying a normal load to the top surface of the concrete enclosing shell 9, a shear load loading system for applying a shear load to the side surface of the concrete enclosing shell 9, and a data test acquisition system for measuring normal pressure, normal displacement and tangential displacement, wherein the normal load loading system and the shear load loading system are arranged on the test platform.

[0057] The rock sample 10 and the rock mass below the test platform are integrated, the rock structure surface to be measured of the rock sample 10 is on the same plane as the test platform or has a slope of less than 15°, and the concrete enclosing shell 9 is wrapped from the bottom of the rock sample 10 to the top surface. The present embodiment applies a normal load to the rock sample 10 through the normal load loading system, applies a tangential load to the rock sample 10 through the shear load loading system, and measures the normal pressure, normal displacement and tangential displacement through the data test acquisition system during the application of the normal load and the tangential load, thereby quickly and accurately obtaining the shear strength parameters of the field rock structural plane, improving the accuracy and reliability of the obtained rock shear strength parameters, and the test system integrates loading and shearing, the test equipment is simple, easy to operate, the test period is short, and the required test site is small.

[0058] Further, the top surface of the rock sample 10 is approximately parallel to the rock structure surface to be measured of the rock sample 10, and the four sides of the rock sample 10 are trimmed flat; the concrete enclosing shell 9 should have sufficient rigidity and strength, and be tightly combined with the rock sample 10 to be measured, the top surface of the concrete enclosing shell 9 is parallel to the rock structure surface to be measured, and the bottom surface of the concrete enclosing shell 9 is parallel to the rock structure surface to be measured with a certain distance, which should be not less than 20 cm.

[0059] As shown in Figure 1 and Figure 2 , the normal load loading system is used to provide stable and continuous normal load during the test, which includes the roller row 8, the normal load transmission steel plate 22 and the counterforce loading device for applying normal load to the normal load transmission steel plate 22, the roller row 8 is fixed on the bottom surface of the normal load transmission steel plate 22 and is in contact with the top surface of the concrete enclosing shell 9, so that the normal force is uniform. Wherein, the normal load transmission steel plate 22 and the roller row 8 are both made of metal material, the size of the roller row 8 should be larger than the size of the top surface of the concrete enclosing shell 9, the size of the normal load transmission steel plate 22 should be not less than 0.5 m x 0.5 m x 0.2 m and slightly larger than the size of the roller row 8, and the four corners of the normal load transmission steel plate 22 are reserved with fixed holes 24 through up and down. Optimally, the bottom surface of the normal load transmission steel plate 22 is provided with a mounting groove, and the roller row 8 is arranged in the mounting groove, as shown in Figure 3 , the roller row 8 includes a plurality of rollers arranged in parallel and equidistantly, and the shaft bodies at both ends of the roller are rotatably installed in the normal load transmission steel plate 22 through bearings.

[0060] The present embodiment can apply normal load to the rock to be measured through the following two counterforce loading devices according to the actual situation on site. As an embodiment, as shown in Figure 1 , the counterforce loading device includes four bored piles 6.1 arranged outside the four corners of the concrete enclosing shell 9, the bored piles 6.1 are used to provide counterforce, the bottom of the bored piles 6.1 is embedded below the test platform to a certain depth, the top of the bored piles 6.1 is reserved with a nest groove 5.1 for facilitating the embedding of the force transmission column 1.1, the bottom of the force transmission column 1.1 is placed in the nest groove 5.1 and connected by pouring concrete; the normal load transmission steel plate 22 is reserved with fixed holes 24 at positions corresponding to the force transmission column 1.1, the top of the force transmission column 1.1 penetrates through the corresponding fixed holes 24, the force transmission column 1.1 is fixed with a first bolt 2.1 and a second bolt 4.1, and the first bolt 2.1 and the second bolt 4.1 are respectively located above and below the normal load transmission steel plate 22 to fix the normal load transmission steel plate 22 and the force transmission column 1.1. Wherein, the force transmission column 1.1 is preferably made of metal material with high bending strength. As another embodiment, as shown in Figure 2As shown, the reaction loading device includes four anchor rods 1.2 disposed on the outer sides of the four corners of the concrete encapsulation shell 9. The anchor rods 1.2 can be made of threaded steel and are used to provide reaction force. Their bottoms are embedded to a certain depth below the test platform and filled with anchoring agent to fix the bottom of the anchor rods 1.2. Fixing holes 24 are reserved on the normal load transmission steel plate 22 at the positions corresponding to the anchor rods 1.2. The top of the anchor rods 1.2 passes through the corresponding fixing holes 24 and is fixed to the normal load transmission steel plate 22 and the anchor rods 1.2 by anchors 2.2.

[0061] When the normal load loading system adopts Figure 2 In the structure shown, a support system is provided on both sides of the normal load loading system to fix the normal load loading system and prevent it from lateral displacement. The support system includes a lateral support steel plate 4.2, a main support beam 5.2, and secondary support beams 6.2. One side of the top of the lateral support steel plate 4.2 abuts against the normal load transmission steel plate 22, and the other side of the top of the lateral support steel plate 4.2 is connected to the top of the main support beam 5.2. The main support beam 5.2 is inclined and is connected to the lateral support steel plate 4.2 by several secondary support beams 6.2. The bottom of the main support beam 5.2 and the bottom of the lateral support steel plate 4.2 are respectively embedded into the test platform at a certain depth.

[0062] In the above embodiment, the shear load loading system comprises a shear load hydraulic jack 13, a tangential load transmission rigid plate, a jack support 16 and a jack lateral support device; the jack support 16 is arranged on the test platform, the fixed end of the shear load hydraulic jack 13 is connected with the jack lateral support device and supported on the jack support 16, and the movable end of the shear load hydraulic jack 13 is abutted on the side of the concrete enveloping shell 9 through the tangential load transmission rigid plate. In this embodiment, the shear load hydraulic jack 13 provides a continuous and stable tangential load for the rock sample 10, and the hydraulic oil pump 15 is used as the power source of the shear load hydraulic jack 13. Meanwhile, the shear load hydraulic jack 13 is provided with a pressure gauge, which can display the tangential load value applied by the shear load hydraulic jack 13 to the rock sample 10 in real time. Optimally, the jack lateral support device comprises a jack lateral support 18, a main support beam 20 and a secondary support beam 19. The jack lateral support 18 is arranged outside the jack support steel plate 17 and is used to fix the jack support steel plate 17 so as not to produce lateral displacement. The bottom of the jack lateral support 18 is embedded below the test platform by a certain depth. The main support beam 20 and the secondary support beam 19 are arranged outside the jack lateral support 18 and are used to support the jack lateral support 18. The main support beam 20 is arranged obliquely. The top end of the main support beam 20 is connected with the top of the jack lateral support 18, and the bottom end of the main support beam 20 is embedded below the test platform by a certain depth. The main support beam 20 and the jack lateral support 18 are supported by the secondary support beams 19 arranged transversely.

[0063] In the above embodiment, the data test collection system comprises a data processing terminal 23, a normal distance measuring device for measuring normal displacement, a tangential distance measuring device for measuring tangential displacement and a normal pressure measuring device for measuring normal pressure. The normal distance measuring device, the tangential distance measuring device and the normal pressure measuring device are respectively connected with the data processing terminal 23 through data transmission wires 21. In this embodiment, the normal distance measuring device comprises a normal laser range finder 11.1 for recording the normal displacement in the test process and a normal distance measuring positioning cursor 12.1 for facilitating the measurement and positioning of the normal laser range finder 11.1. The normal distance measuring device has two installation modes. As shown in Figure 1 As shown in FIG. 6, in the first installation mode, the normal laser range finder 11.1 is arranged on the bottom surface of the concrete enveloping shell 9, the normal distance measuring positioning cursor 12.1 is arranged on the test platform, and the axial direction of the normal distance measuring positioning cursor 12.1 is consistent with the axial direction of the normal laser range finder 11.1. Figure 2As shown, the second installation mode is that the normal laser range finder 11.1 is arranged on the bottom surface of the normal load transmission steel plate 22 and located outside the roller shaft row 8, and the normal range-finding positioning cursor 12.1 is arranged on the test platform and the axial direction of the normal range-finding positioning cursor 12.1 is consistent with the axial direction of the normal laser range finder 11.1.

[0064] Specifically, the tangential range-finding device includes a tangential laser range finder 11.2 and a tangential range-finding positioning cursor 12.2, regardless of whether the normal load loading system adopts Figure 1 As shown, the installation mode is also Figure 2 As shown, the installation mode is also Specifically, the normal pressure measuring device is a pressure gauge 3.1 or an anchor cable gauge 3.2, which is used to record the normal pressure; when the normal load loading system adopts Figure 1 As shown, the normal pressure measuring device adopts the pressure gauge 3.1, which is arranged in the groove on the top surface of the normal load transmission steel plate 22 and is in close contact with the bolt above it; when the normal load loading system adopts Figure 2 As shown, the normal pressure measuring device adopts the anchor cable gauge 3.2, which is arranged in the groove on the top surface of the normal load transmission steel plate 22 and is in close contact with the anchor 2.2 above it. The recorded data of the normal laser range finder 11.1, the tangential laser range finder 11.2 and the pressure gauge 3.1 or the anchor cable gauge 3.2 are transmitted to the data processing terminal 23 through the data transmission wire 21, and the data processing terminal 23 processes the received pressure, displacement and other data.

[0065] Embodiment Two

[0066] As shown in the drawings, Figure 1 The embodiment provides a field rock structural plane shearing test method, which comprises the following steps:

[0067] S1, experimental preparation

[0068] A rock sample 10 is selected, the size of the selected rock sample 10 is less than 0.3m*0.3m*0.3m, the rock structural plane to be measured and the range of the rock sample 10 involved are determined, the site around the rock sample 10 to be measured is leveled, the loose rocks on the surface of the rock sample 10 to be measured are removed, the rock around the rock sample 10 to be measured is cut off and separated, and the scum formed by processing is cleaned.

[0069] S2, construction of a shearing test system

[0070] (1) Construction concrete envelope shell 9

[0071] Pour construction concrete envelope shell 9 around and on top of the rock mass sample 10 to be tested, and process it into a square structure. The top surface should be parallel to the rock mass structure surface to be tested, and the bottom surface should be parallel to the top surface and have a certain distance from the rock mass structure surface to be tested. The distance should not be less than 20 cm. After curing the concrete for a period of time, remove the mold to form the concrete envelope shell 9.

[0072] According to the requirements of normal displacement and tangential displacement measurement, normal distance measuring and positioning cursors 12.1 are arranged on one side of the concrete envelope shell 9 near the shear load hydraulic jack 13, and tangential distance measuring and positioning cursors 12.2 are arranged on both sides of the bottom surface of the rock mass to be tested.

[0073] (2) Installation of normal load loading system

[0074] Place the normal load transmission steel plate 22 with the bottom surface bearing the roller shaft row 8 above the top of the concrete envelope shell 9. The roller shaft row 8 should be in close contact with the top surface of the concrete envelope shell 9 to ensure that the central axis of the normal load transmission steel plate 22 is consistent with the central axis of the concrete envelope shell 9.

[0075] When the reaction force loading device adopts the structure shown in Figure 2 When the reaction force loading device adopts the structure shown in

[0076] When the reaction force loading device adopts the structure shown in Figures 1-3 When the reaction force loading device adopts the structure shown in

[0077] S23, installation of shear load loading system

[0078] A shear load transmission steel plate is pasted on the shear load stress surface of the concrete encapsulation shell 9 with cement slurry, the bottom of the shear load transmission steel plate should be kept a distance from the ground and be perpendicular to the rock mass structure surface to be measured; then the jack support 16, the shear load hydraulic jack 13, the jack support steel plate 17 and the jack lateral support 18 are installed in sequence outside the shear load transmission steel plate, the jack support steel plate 17 is parallel to the shear load transmission steel plate;

[0079] When the shear load loading system is installed, the shear force application center line should be parallel to the rock mass structure surface to be measured, and the distance from the rock mass structure surface to be measured should be not greater than 5% of the shear direction rock mass sample 10.

[0080] S24, installation of support system

[0081] When the reaction force loading device adopts the structure form as shown in Figure 1 , it is necessary to install a support system for fixing the normal load transmission steel plate 22, tightly bond the lateral support steel plate 4.2 with the normal load transmission steel plate 22, weld the top of the support main beam 5.2 on the lateral support steel plate 4.2, and tilt the support main beam 5.2 and sequentially weld two to three support secondary beams 6.2 between the support main beam 5.2 and the lateral support steel plate 4.2 to connect the support main beam 5.2 and the lateral support steel plate 4.2; wherein the bottom of the lateral support steel plate 4.2, the main beam and the secondary beam should be embedded into the ground surface to a certain depth.

[0082] S25, installation of data test collection system

[0083] The normal distance measuring device and the tangential distance measuring device can be installed in the manner as shown in Figure 2 or Figure 2 Figure 1 Figure 2 , or the appropriate installation position is selected in combination with the actual situation on site, and the laser range finder should be fixedly installed at a certain height.

[0084] All test equipment and data processing terminals 23 should pay attention to waterproof and humidity, and the ranging positioning cursors and the laser range finder should be strictly oriented, respectively perpendicular or parallel to the rock structure surface to be measured, and the initial reading should be adjusted appropriately.

[0085] S3, experimental loading

[0086] 1) The resultant force of the normal load and the shear load should pass through the shear surface center;

[0087] 2) The normal load is applied in stages, and the staging index is determined according to the on-site rock properties and the reaction force providing mode; when the normal load is applied in stages, the normal displacement is measured immediately after each stage of normal load is applied through the normal laser range finder 11.1, and the normal displacement is measured again after 5 minutes, so that the difference between the two continuous normal displacement measurements is less than 0.01mm as the normal load stability standard, and the shear load is applied after the normal load is stable;

[0088] 3) Apply shear load, load shear load every 5 minutes, before and after the application of shear load should be through the tangential laser range finder 11.2 read tangential displacement and through the shear load hydraulic jack 13 built-in pressure gauge to read shear force data, before the peak should be measured tangential displacement and shear force, read data greater than 15 groups; rock structure surface is cut off after can continue to load, until the shear load value tends to be stable;

[0089] S4, data arrangement

[0090] According to the following formula to calculate the normal stress and shear stress:

[0091] a, when the rock mass structure surface is horizontal,

[0092] N 总 = 4N σ +N α (1-1)

[0093]

[0094]

[0095] Q = Q 推力 -Q 摩擦 (1-4)

[0096] In the formula, σ—normal stress acting on the rock mass structure surface (MPa);

[0097] τ—shear stress acting on the rock mass structure surface (MPa);

[0098] N 总 —total normal load acting on the rock mass structure surface (N);

[0099] N σ —anchoring force provided by the reaction force loading device (N);

[0100] N α —other normal loads (N), including normal load transmission steel plate 22, roller shaft row 8 and other normal loads, that is, the gravity of normal load transmission steel plate 22, roller shaft row 8 and other devices;

[0101] Q—total shear load acting on the rock mass structure surface (N);

[0102] Q 推力 —pushing force provided by the shear load loading system (N);

[0103] Q 摩擦— the friction force (N) between the normal load loading system and the concrete envelope 9 when the normal stress is σ; the value can be obtained by the following method: a concrete plate with the same length and width as the concrete envelope 9 and with a thickness of 10 cm is placed between the roller shafts 8 of the same type on the upper and lower sides, and the concrete plate is pushed by a hydraulic jack; when the concrete plate is pushed, half of the pushing force provided by the hydraulic jack is Q 摩擦 ;

[0104] A— the area (m 2 ) of the rock mass structure surface;

[0105] b、when the rock mass structure surface is located on a gentle slope (generally, the slope should be gentler than 15°),

[0106] N 总 ′=4N σ +N α cos α (1-5)

[0107]

[0108] In the formula, α— the angle (°) between the rock structure surface and the horizontal plane;

[0109] When the structure surface has a certain angle with the horizontal plane, the same test system as when the structure surface is horizontal is used, the normal load loading system and the normal load applied thereby are perpendicular to the structure surface to be measured, and the shear load loading system and the shear load applied thereby are parallel to the structure surface to be measured.

[0110] The shear force τ received by the rock mass structure surface is calculated by formula 1-3.

[0111] S5、Data processing

[0112] 1) Given the normal stress σ1, draw the relationship curve between the shear stress τ1 and the tangential displacement and the normal displacement under the normal stress, and determine the peak shear stress τ 11 and the residual shear stress τ 21 under the normal stress σ1 according to the relationship curve.

[0113] 2) Repeat step 1) to obtain the peak shear stress τ 12 and the residual shear stress τ 22 under the normal stress σ2, the peak shear stress τ 13 and the residual shear stress τ 23 under the normal stress σ3, the peak shear stress τ 14 and the residual shear stress τ 24 ……, and obtain not less than 4 groups of shear stress data corresponding to the normal stress;

[0114] 3) draw the curve of normal stress σ and its corresponding peak shear stress and residual shear stress, and determine the corresponding shear strength parameters: cohesion c, internal friction angle

[0115] 4) make the test records of normal load, shear load, normal displacement, tangential displacement, test date, sample number, rock name and other test records, and arrange the corresponding test results.

[0116] The test method of the embodiment has clear ideas, is easy to operate, has strong repeatability, and has simple test equipment. Different reaction force loading devices can be selected according to the actual situation on site, and the method has strong on-site operability. As a new exploration and attempt, the method makes up for the defects of the current on-site rock structure surface shear test method, solves the problems of large occupation and low reliability existing in the traditional test method, can qualitatively and quantitatively evaluate the strength characteristics of the key rock structure surface, and has guiding significance for the design and scheme optimization of geotechnical engineering.

[0117] The above merely describes preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for in-situ rock structural surface shear test, characterized in that, Includes the following steps: S1. Select rock mass samples and determine the structural plane of the rock mass to be tested and the range of the rock mass samples involved. Level the site around the rock mass samples to be tested, remove loose rocks on the surface of the rock mass samples to be tested, cut and separate the rock mass around the rock mass samples to be tested and remove the slag. S2. Construction shear test system, the shear test system includes a horizontally set test platform, a concrete encapsulation shell wrapped around the rock mass sample, a normal load loading system for applying a normal load to the top surface of the concrete encapsulation shell, a shear load loading system for applying a shear load to the side surface of the concrete encapsulation shell, and a data test and acquisition system for measuring normal pressure, normal displacement and tangential displacement, wherein the normal load loading system and the shear load loading system are both set on the test platform; S3. Apply normal loads in stages, and immediately measure the normal displacement through the data testing and acquisition system after each stage of normal load is applied. Measure the normal displacement again after 5 minutes. The standard for normal load stability is that the difference between two consecutive normal displacement measurements is less than 0.01 mm. Apply shear load only after the normal load has stabilized. S4. When applying shear load, apply shear load once every 5 minutes. Before and after applying shear load, the tangential displacement and shear force data should be read through the data testing and acquisition system. Before the peak value, the measurement of tangential displacement and shear force should be increased. After the rock structure surface is sheared, the load can continue to be applied until the shear load value tends to stabilize. S5. Calculate the normal stress σ and shear force τ acting on the rock mass structure surface according to the formula, plot the relationship curve between shear force τ and tangential displacement and normal displacement under different normal stress σ, and calculate the peak shear stress and residual shear stress under different normal stress σ. S6. Plot the relationship curve between the normal stress σ and its corresponding peak shear stress and residual shear stress, and calculate the corresponding shear strength parameters according to the Mohr-Coulomb expression: cohesion c and internal friction angle φ. The formulas for calculating the normal stress σ and shear force τ in step S5 are as follows: When the rock mass structural plane is horizontal （1-1） （1-2） （1-3） （1-4） In the formula, σ is the normal stress (MPa) acting on the rock mass structural surface. τ—Shear stress (MPa) acting on the rock mass structural surface; N 总 —Total normal load (N) acting on the rock mass structural surface when the rock mass structural surface is horizontal. N σ — Anchoring force (N) provided by the normal load loading system; N α —Other loads in the normal direction (N); Q—Total shear load (N) acting on the rock mass structural surface. Q 推力 —Thrust (N) provided by the shear load loading system; Q 摩擦 —The frictional force (N) between the normal load loading system and the concrete encapsulation shell when the normal stress is σ. A—Area of ​​rock mass structural plane (m²) 2 ); When the rock mass structural plane is located on a gentle slope （1-5） （1-6） In the formula, α—the angle between the rock structure plane and the horizontal plane (°); N 总 —The total normal load (N) acting on the rock mass structural surface when it is located on a gentle slope; the shear force τ received by the rock mass structural surface is calculated using Equation 1-3.

2. The in-situ rock structural surface shear test method as described in claim 1, characterized in that: The top surface of the rock mass sample is approximately parallel to the rock mass structure surface to be tested, the top surface of the concrete encapsulation shell is parallel to the rock mass structure surface to be tested, and the bottom surface of the concrete encapsulation shell is parallel to the rock mass structure surface to be tested but at a certain distance.

3. The in-situ rock structural surface shear test method as described in claim 1, characterized in that: The normal load loading system includes a roller array, a normal load transmission steel plate, and a reaction loading device for applying a normal load to the normal load transmission steel plate. The roller array is fixed to the bottom surface of the normal load transmission steel plate and contacts the top surface of the concrete encapsulation shell.

4. The in-situ rock structural surface shear test method as described in claim 3, characterized in that: The reaction loading device includes several bored piles arranged around the concrete encapsulation shell. The bottom of the bored piles is embedded below the test platform, and a force transmission column is installed on the top of the bored piles. Fixing holes are reserved at the positions of the force transmission columns on the normal load force transmission steel plate. The force transmission columns pass through the corresponding fixing holes and are fixed to the normal load force transmission steel plate by bolts.

5. The in-situ rock structural surface shear test method as described in claim 3, characterized in that: The reaction loading device includes several anchor rods disposed around the concrete encapsulation shell. The bottom of the anchor rods is embedded below the test platform. Fixing holes are reserved at the positions of the anchor rods on the normal load transmission steel plate. The top of the anchor rods passes through the corresponding fixing holes and is fixed to the normal load transmission steel plate through anchors.

6. The in-situ rock structural surface shear test method as described in claim 5, characterized in that: The normal load loading system is equipped with a support system on both sides. The support system includes a lateral support steel plate, a main support beam, and secondary support beams. One side of the top of the lateral support steel plate is in close contact with the normal load transmission steel plate, and the other side of the top of the lateral support steel plate is connected to the top of the main support beam. The main support beam is inclined and is connected to the lateral support steel plate by several secondary support beams. The bottom of the main support beam and the bottom of the lateral support steel plate are respectively embedded below the test platform.

7. The in-situ rock structural surface shear test method as described in claim 1, characterized in that: The shear load loading system includes a shear load hydraulic jack, a tangential load transmission plate, a jack support, and a jack lateral support device. The jack support is mounted on the test platform. The fixed end of the shear load hydraulic jack is connected to the jack lateral support device and supported on the jack support. The movable end of the shear load hydraulic jack abuts against the side of the concrete encapsulation shell through the tangential load transmission plate.

8. The method for in-situ rock structural surface shear test as described in claim 1, characterized in that: The data testing and acquisition system includes a data processing terminal, a normal ranging device for measuring normal displacement, a tangential ranging device for measuring tangential displacement, and a normal pressure measuring device for measuring normal pressure; the normal ranging device, the tangential ranging device, and the normal pressure measuring device are respectively connected to the data processing terminal via data transmission lines.

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