A shearing creep test device and test method capable of controlling water state of rock structural plane

Abstract

The application provides a shearing creep test device and test method for controlling water content of rock structural plane, which comprises a direct shear apparatus, a water immersion device, an air filling device and a shearing box. The direct shear apparatus comprises a loading frame, a loading device and a sliding device. The shearing box comprises an upper shearing box and a lower shearing box. The upper shearing box has a first notch, and the lower shearing box has a second notch. The rock sample with structural plane comprises an upper disc rock, a lower disc rock and a structural plane. The upper disc rock is placed in the first notch, and the lower disc rock is placed in the second notch. The lower shearing box is placed on the sliding device. The upper disc rock and the upper shearing box are placed on the lower disc rock, and the structural planes of the upper disc rock and the lower disc rock are aligned and contacted. The water immersion device is arranged on the lower shearing box, and the air filling device is connected to the upper shearing box. The loading device applies a normal load to the upper shearing box and a lateral load to the lower shearing box. The application can be applied to the research on the shearing mechanical properties and shearing creep properties of the rock structural plane under different water contents.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rock mechanics property testing, in particular, relates to a shear creep test device capable of controlling water content of rock structural plane and a test method. BACKGROUND

[0002] There are a large number of faults, joints and weak interlayers in engineering rock mass. These structural planes are weak parts of rock mass engineering, and their mechanical properties have an important influence on the stability of rock mass. In the case of continuous rainfall or continuous rise of groundwater level, the invasion of water will increase the bulk density of rock mass, weaken the friction and cohesion between particles inside the rock, and the chemical corrosion of water will have irreversible effects on the strength and damage and fracture mechanism of the rock. When the rock in the rock mass is hard or has low water absorption, rainfall or groundwater mainly seeps into the interior of the rock mass through the structural plane, and under the action of water-rock, the structural plane will gradually cause surface damage and roughness deterioration. The weakening degree of the structural plane caused by different water contents of the structural plane is different, and generally the greater the water content of the structural plane, the greater the weakening degree of the structural plane. The deterioration of the structural plane will promote the shear creep deformation, increase the creep rate, and reduce the long-term strength of the structural plane, until shear slip instability occurs. Therefore, in order to more accurately predict and control the stability of rock mass containing hard structural plane, it is necessary to study the shear creep properties of rock hard structural plane under different water contents. However, most of the current rock shear creep equipment can only conduct shear creep test of rock structural plane under dry or completely immersed conditions, and cannot control the water content of rock structural plane. Although some scholars have slowed down the water loss of rock structural plane by controlling the temperature and humidity of the laboratory, it is still difficult to maintain the rock structural plane at a certain water content for a long time. Therefore, it is necessary to develop a shear creep test device capable of controlling the water content of rock structural plane. SUMMARY

[0003] According to the above technical problems, a shear creep test device capable of controlling the water content of rock structural plane and a test method are provided. The present application mainly controls the water content of the structural plane by immersing and locally pressurizing the structural plane, and realizes the shear test and shear creep test of the structural plane under different water contents.

[0004] The technical means adopted by the present application are as follows:

[0005] A shear creep test device capable of controlling the water content of rock structural plane, comprising: a direct shear apparatus, a water immersion device, an air inflation device and a shear box, the direct shear apparatus comprising a loading frame and a loading device and a sliding device mounted on the loading frame;

[0006] The shear box is used for containing a structural plane-containing rock sample, comprising an upper shear box and a lower shear box arranged at intervals, one side of the upper shear box is provided with a first notch, one side of the lower shear box is provided with a second notch, and the first notch and the second notch are oppositely arranged.

[0007] The structural plane-containing rock sample comprises an upper disc rock, a lower disc rock and a structural plane, the upper disc rock is placed in the first notch of the upper shear box, the lower disc rock is placed in the second notch of the lower shear box, the lower shear box is placed on the sliding device, the upper disc rock and the upper shear box are placed on the lower disc rock, the surface of the upper disc rock in contact with the lower disc rock is the structural plane, the structural planes of the upper disc rock and the lower disc rock are in contact in alignment, the structural plane is located in the gap interval between the upper shear box and the lower shear box, and the total height of the upper disc rock and the lower disc rock is greater than the total height of the inner cavities of the upper shear box and the lower shear box.

[0008] The water immersion device is arranged on the lower shear box and is used for immersing the structural plane.

[0009] The air filling device is connected to the upper shear box and is used for filling air into the structural plane.

[0010] The loading device is used for applying a normal load to the top of the upper shear box and applying a lateral load to one side of the lower shear box.

[0011] Further, the direct shear apparatus further comprises a loading platform and a loading control system, the loading platform is a concrete filling platform and is arranged below the loading frame, and the loading control system is arranged outside the loading frame.

[0012] The loading device comprises a vertical actuator, a first horizontal actuator, a second horizontal actuator and a slide rail, each actuator is fixed to the loading frame and connected to the loading control system, wherein the vertical actuator is fixed above the loading frame and is used for applying a normal load to the top of the upper shear box, the first horizontal actuator is fixed to one side of the loading frame and is used for contacting one side of the upper shear box, and the second horizontal actuator is fixed to the other side of the loading frame and is used for applying a lateral load to one side of the lower shear box.

[0013] The sliding device comprises a slide rail, the slide rail is fixed to the loading platform and connected to the loading frame, and the lower shear box is placed on the slide rail.

[0014] Further, a plurality of semispherical grooves are uniformly arranged at the bottom of the lower shear box, a steel ball is arranged in each groove, the steel ball is connected to the slide rail in cooperation, and lubricating oil is coated on the surface of each groove at the bottom of the lower shear box and the steel ball.

[0015] Further, the air charging device comprises a high-pressure air pipe and an air pump, a plurality of air inlets are uniformly arranged on the front and back of the top of the upper shear box along the direction of the rock width, the air inlets are connected with the first slot of the upper shear box, one side of the high-pressure air pipe is connected with the air inlets, and the other side of the high-pressure air pipe extends to the outside of the loading frame and is connected with the air pump; a plurality of structural plane air inlets are arranged on the upper disc rock according to the distribution positions of the air inlets, one side of the plurality of structural plane air inlets is connected with the plurality of air inlets, and the other side of the plurality of structural plane air inlets is connected with the structural plane.

[0016] Further, three air inlets are uniformly arranged on the front of the top of the upper shear box along the direction of the rock width, two air inlets are arranged on the back of the top of the upper shear box along the direction of the rock width, and the five air inlets are respectively connected with the first slot of the upper shear box, and the outlets of the five air inlets are uniformly distributed along two diagonal lines on the upper shear box.

[0017] The air inlets are provided with threads, and the end of the high-pressure air pipe is provided with a threaded metal pipe which is screwed into the air inlet by threads.

[0018] Further, the water immersion device comprises a glass jar, a water pipe and a water pump, the glass jar is placed on the outer wall above the lower shear box, an opening is arranged in the middle of the bottom of the glass jar, the opening is aligned with the second slot of the lower shear box, the lower disc rock is placed in the opening and the second slot of the lower shear box, the upper part of the lower disc rock is located in the glass jar, and the length and width of the opening are equal to the length and width of the lower disc rock.

[0019] The bottom of the glass jar is provided with a water inlet, the water inlet is connected with the water pump through the water pipe, and the water inlet is used for injecting water into the glass jar, and the injected water is higher than the structural plane.

[0020] Further, the small gap between the edge of the opening and the second slot of the lower shear box and the lower disc rock is sealed by glass glue, the inner size of the glass jar is greater than that of the upper shear box, and the distance between the inner wall of the glass jar and the upper shear box is greater than the shear creep displacement of the structural plane rock sample.

[0021] Further, the structural plane rock sample is a cubic sample with equal side length, and the structural plane is located at the position of 1 / 2 height of the cubic sample and has an angle of 0° with the horizontal plane.

[0022] Further, the four sides of the structural plane rock sample between the gaps of the upper shear box and the lower shear box are smeared with glass glue.

[0023] The application also provides a test method of the shear creep test device capable of controlling the water state of the rock structural plane, and the test method comprises the following steps:

[0024] Step one, make the rock sample containing structural plane, the structural plane is located at the position of 1 / 2 height of the sample, the angle with the horizontal plane is 0°, drill 1-5 structural plane air inlet holes on the upper disc rock according to the distribution position of the air inlet holes of the upper shear box, place the prepared rock sample containing structural plane in the drying box and dry to constant weight;

[0025] Step two, place the first notch of the upper shear box and the second notch of the lower shear box upwards on the workbench, place the upper disc rock in the first notch of the upper shear box, and place the lower disc rock in the second notch of the lower shear box, put the opening at the bottom of the glass jar over the lower disc rock, and place the glass jar on the outer wall of the second notch of the lower shear box;

[0026] Step three, use glass glue to seal the small gap between the edge of the opening at the bottom of the glass jar and the edge of the second notch of the lower shear box and the rock sample containing structural plane, to prevent water from seeping into the shear box, and smear a layer of glass glue on the four sides of the rock sample containing structural plane between the notch edges of the upper shear box and the lower shear box, to prevent water from seeping into the rock sample containing structural plane from the sides of the rock sample containing structural plane, and place the glued shear box and rock sample containing structural plane together in the constant temperature curing box for curing;

[0027] Step four, after the glass glue dries and solidifies, combine the upper disc rock and the lower disc rock according to the profile of the rock structural plane, place the shear box on the loading position on the slide rail, connect one end of the high-pressure air pipe to the air pump, twist the other end of the high-pressure air pipe into the air inlet hole of the upper shear box corresponding to the desired drying position of the rock sample containing structural plane, connect one end of the water pipe to the water pump, and connect the other end of the water pipe to the water inlet of the glass jar;

[0028] Step five, control the vertical actuator to apply pre-tightening force to the top surface of the upper shear box through the loading control system, open the air pump, adjust the air pressure to the predetermined value, inflate the structural plane, open the water pump to inject water into the glass jar, and the water level is higher than the structural plane;

[0029] Step six, after the water completely wets the structural plane, use the water pump to pump out the water in the glass jar, close the water pump and the air pump, control the vertical actuator to lift up through the loading control system, remove the upper shear box and the upper disc rock, take a photo to record the wet and dry state of the structural plane, calculate the wetted area of the structural plane, the water content of the structural plane is the ratio of the wetted area of the structural plane to the total area of the structural plane, reset the upper shear box and the upper disc rock, and repeat step five;

[0030] Step seven, the first horizontal actuator and the right side of the upper shear box are in contact by loading control system, the vertical actuator is operated to apply a normal load to the top surface of the upper shear box to a set value, the second horizontal actuator is operated to apply a transverse shear load to the left side of the lower shear box to a set value, until the sample occurs shear creep failure or reaches the preset creep time, the water level in the glass cylinder is always kept above the structural plane during the test, and the loading control system collects load and displacement data in real time during the test.

[0031] Compared with the prior art, the present application has the following advantages:

[0032] The shear creep test device for controlling the water state of the rock structural plane provided by the present application controls the water content position and water content rate of the rock structural plane by water immersion and air pressure, realizes the shear test and shear creep test of the rock structural plane under different water states, solves the problem that it is difficult to control the water state of the structural plane during the shear creep test, and can be applied to the research on the shear mechanical properties and shear creep properties of the rock structural plane under different water states.

[0033] Based on the above reasons, the present application can be widely popularized in the field of rock mechanical property testing. DETAILED DESCRIPTION

[0034] 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 in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0035] Figure 1 It is a schematic diagram of the overall structure of the embodiment of the present application.

[0036] Figure 2 It is a local enlarged view of the shear box of the embodiment of the present application.

[0037] Figure 3 It is a connection diagram of the upper shear box, the air inlet hole and the high-pressure air pipe of the embodiment of the present application.

[0038] Figure 4 It is a front view of the shear box of the embodiment of the present application.

[0039] Figure 5 It is a left view of the shear box of the embodiment of the present application.

[0040] Figure 6 It is a top view of the shear box of the embodiment of the present application.

[0041] Figure 7 It is an example diagram of the rock containing the structural plane of the embodiment of the present application.

[0042] Figure 8 Fig. 1 is a schematic view of the glass cylinder. Figure 7

[0043] Figure 9 Fig. 2 is a schematic view of the glass cylinder.

[0044] Figure 10 Fig. 3 is a schematic view of the control of the water content of the rock structural plane.

[0045] Figure 11 Fig. 4 is a simplified schematic view of the glass cylinder. Figure 10

[0046] Figure 12 Fig. 5 is a schematic view of the increase of the inflation air pressure to Fig. 6 is a schematic view of the glass cylinder.

[0047] In the figure: 1, loading frame; 2, vertical actuator; 31, first horizontal actuator; 32, second horizontal actuator; 4, slide rail; 5, concrete filling platform; 6, shear box; 61, upper shear box; 62, lower shear box; 63, air inlet hole; 7, structural plane containing rock sample; 71, upper disc rock; 72, lower disc rock; 73, structural plane; 74, structural plane air inlet hole; 8, glass cylinder; 81, water inlet; 82, opening; 9, steel ball; 10, high-pressure air pipe; 11, water pipe; 12, loading control system; 13, air pump; 14, water pump. DETAILED DESCRIPTION

[0048] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The technical solutions in the embodiments of the present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0049] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0050] ​​​It is to be understood that the terms so far as the word "comprise" and / or "comprising", or "include" and / or "including" when used in this specification is / are used to express the inclusion of one or more steps, operations, elements, and / or components, but these articles do not exclude the other steps, operations, elements, and / or components.

[0051] The relative arrangement of parts and steps, numerical expressions, and numerical values set forth in the examples are not intended to limit the scope of the application unless specifically so stated. It is also to be understood that the dimensions of the various parts shown in the drawings are not necessarily to scale, and that for purposes of convenience and clarity in understanding the present application, common terms have been used for like components throughout. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail, but are to be considered as part of the description. In all examples shown and discussed herein, any specific values are to be interpreted as merely exemplary and not as a limitation on the scope of the exemplary embodiments. Thus, other examples of the exemplary embodiments can have different values. It is to be noted that like reference numerals and letters refer to like items in the drawings, and once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0052] In the description of the present application, it is to be understood that the orientation or positional relationships indicated by orientation words such as "front, back, upper, lower, left, right", "transverse, vertical, perpendicular, horizontal", and "top, bottom" are generally based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Without the opposite indication, these orientation words do not indicate and imply that the devices or elements referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the scope of protection of the present application: the orientation words "inner, outer" refer to the inner and outer relative to the outline of each component itself.

[0053] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0054] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0055] This invention provides a shear creep testing device that can control the water content of rock structural surfaces, such as... Figures 1-9 As shown, the system includes a shear box 6, a glass cylinder 8, a direct shear apparatus, an air pump 13, a water pump 14, a water pipe 11, and a high-pressure air pipe 10. The direct shear apparatus includes a loading control system 12, a loading frame 1, a vertical actuator 2, a horizontal actuator, a slide rail 4, and a concrete filling platform 5. The concrete filling platform 5 is located below the loading frame 1, and the loading control system 12 is located outside the loading frame 1. The horizontal actuator includes a first horizontal actuator 31 and a second horizontal actuator 32. The vertical actuator 2 and the horizontal actuator are fixed to the loading frame 1 and connected to the loading control system 12. The vertical actuator 2 is fixed above the loading frame 1 and can use existing actuators to apply a normal load to the top of the upper shear box 61. The first horizontal actuator 31 is fixed to the right side of the loading frame 1 and can use existing actuators to achieve contact with the right side of the upper shear box 61. The second horizontal actuator 32 is fixed to the left side of the loading frame 1 and can use existing actuators to apply a lateral load to the left side of the lower shear box 62. The loading control system 12 can adopt an existing control system to operate the vertical actuator 2, the first horizontal actuator 31, and the second horizontal actuator 32. It also has a data acquisition function, collecting load and displacement data during the test. The slide rail 4 is fixed to the concrete filling platform 5 and connected to the right side of the loading frame 1, with the lower shear box 62 placed on the slide rail 4. This invention can be applied to the study of shear mechanical properties and shear creep properties of rock structural surfaces under different water content states.

[0056] The shear box 6 comprises an upper shear box 61 and a lower shear box 62, both of which are open and oppositely arranged to form a cavity for accommodating the rock sample 7 with structural plane. The opening is a first slot on one side of the upper shear box 61 and a second slot on one side of the lower shear box 62. The rock sample 7 with structural plane is a cube sample with equal side length, and the structural plane 73 is located at the position of 1 / 2 height of the cube sample with an angle of 0° with the horizontal plane. The rock sample 7 with structural plane is divided into an upper disc rock 71 and a lower disc rock 72 by the structural plane 73, the upper disc rock 71 is placed in the first slot of the upper shear box 61, and the lower disc rock 72 is placed in the second slot of the lower shear box 62. The water absorption rates of the upper disc rock 71 and the lower disc rock 72 are both low and can be ignored. The total height of the upper disc rock 71 and the lower disc rock 72 is greater than the total height of the cavities in the upper shear box 61 and the lower shear box 62. The lower shear box 62 is placed on the slide rail 4, the upper disc rock 71 and the upper shear box 61 are placed on the lower disc rock 72, the surface of the upper disc rock 71 in contact with the lower disc rock 72 is the structural plane 73, the structural planes 73 of the two rocks are aligned and contacted, and the structural plane 73 of the rock is located in the gap between the upper shear box 61 and the lower shear box 62. Three air inlet holes 63 are uniformly arranged on the front surface of the top of the upper shear box 61 in the direction of rock width, and two air inlet holes 63 are arranged on the back surface of the top of the upper shear box 61. The five air inlet holes 63 of the upper shear box 61 respectively lead into the opening of the upper shear box 61 and are uniformly distributed along two diagonal lines in the opening of the upper shear box 61. One to five structural plane air inlet holes 74 can be punched on the upper disc rock 71 according to the distribution position of the air inlet holes 63 in the opening of the upper shear box 61. One side of the structural plane air inlet hole 74 is communicated with the air inlet hole 63, and the other side is communicated with the structural plane 73. A plurality of semispherical grooves are uniformly arranged on the bottom of the lower shear box 62, and a steel ball 9 is arranged in the groove. The lower shear box 62 can be placed on the slide rail 4 of the direct shear instrument, and the steel ball 9 is connected with the slide rail 4 in cooperation. The surface of the steel ball 9 and the groove on the bottom of the lower shear box 62 are coated with lubricating oil. The direct shear instrument can apply a normal load on the top of the upper shear box 61 and a lateral load on the left side of the lower shear box 62.

[0057] An opening 82 is provided in the middle of the bottom of the glass jar 8, and the length and width of the opening 82 of the glass jar 8 are equal to the length and width of the lower disc rock 72 of the structural plane rock sample 7. A water inlet 81 is provided on the right side of the bottom of the glass jar 8, and the water inlet 81 is connected with the water pump 14 (placed outside the loading frame 1) through the water pipe 11, for injecting water into the glass jar 8, and the injected water is higher than the structural plane 73. The glass jar 8 can be placed on the outer wall above the lower shear box 62, so that the opening 82 of the glass jar is aligned with the opening of the lower shear box 62, the lower disc rock 72 is placed in the opening 82 and the opening of the lower shear box 62, and the upper part of the lower disc rock 72 is located in the glass jar 8. The air pump 13 is placed outside the loading frame 1, and the air pump 13 can be connected with the air inlet hole 63 at the top of the upper shear box 61 through the high-pressure air pipe 10. A thread is provided in the air inlet hole 63 of the upper shear box 61, and a threaded metal pipe can be installed at the end of the high-pressure air pipe 10, and the threaded metal pipe can be screwed into the air inlet hole 63 of the upper shear box 61 by using the thread.

[0058] The small gap between the opening 82 of the bottom of the glass jar 8 and the edge of the opening of the shear box 6 and the structural plane rock sample 7 is sealed by glass glue, the inner size of the glass jar 8 is larger than the upper shear box 61, the glass jar 8 can be surrounded outside the upper shear box 61, and the distance between the inner wall of the glass jar 8 and the upper shear box 61 is much larger than the shear creep displacement of the structural plane rock sample 7. A layer of glass glue is applied to the four sides of the rock sample between the gaps of the upper shear box 61 and the lower shear box 62.

[0059] The method for using the above-mentioned shear creep test device capable of controlling the water content of the rock structural plane includes the following test steps:

[0060] Step one, make the structural plane rock sample 7, the structural plane 73 is located at the position of 1 / 2 height of the sample, and the angle with the horizontal plane is 0°, 1-5 structural plane air inlet holes 74 are drilled on the upper disc rock 71 according to the distribution position of the air inlet hole 63 of the upper shear box 61, and the number and specific position of the drilled holes can be determined according to the required water content of the rock structural plane 73 in the test. For example, if the shear creep characteristics of the structural plane rock sample 7 in the dry middle and the water-containing surrounding of the structural plane 73 are required in the test, only a hole needs to be drilled at the center of the top of the upper disc rock 71. Then, the prepared rock sample is placed in a drying box, and the temperature is set to 105℃, and the sample is baked to constant weight;

[0061] Step two, place the upper shear box 61 and the lower shear box 62 with the openings upward on the workbench, place the upper disc rock 71 in the opening of the upper shear box 61, and place the lower disc rock 72 in the opening of the lower shear box 62, then put the opening 82 of the bottom of the glass jar 8 over the lower disc rock 72, and place the glass jar 8 on the outer wall of the opening of the lower shear box 62;

[0062] Step three, use glass glue to seal the small gap between the edge of the opening 82 of the glass jar 8 and the edge of the open shear box 6 and the structural plane containing rock sample 7, to prevent water from seeping into the shear box 6, and to smear a layer of glass glue on the upper part of the four sides of the rock sample above the open edge of the upper shear box 61 and the lower shear box 62, to prevent water from seeping into the rock sample from the side of the structural plane containing rock sample 7, and then place the glued shear box 6 and the structural plane containing rock sample 7 in the constant temperature curing box for curing;

[0063] Step four, after the glass glue is dried and solidified, the upper disc rock 71 and the lower disc rock 72 are combined according to the profile of the rock structural plane 73, and the shear box 6 is placed on the loading position of the direct shear instrument slide rail 4, one end of the high-pressure air pipe 10 is connected to the air pump 13, the other end is screwed into the air inlet hole 63 of the upper shear box 61 corresponding to the required drying position of the structural plane containing rock sample 7, and then one end of the water pipe 11 is connected to the water pump 14, and the other end is connected to the water inlet 81 of the glass jar 8.

[0064] Step five, control the vertical actuator 2 to apply a pre-tightening force to the top surface of the upper shear box 61 through the loading control system 12, turn on the air pump 13, adjust the air pressure to a predetermined value, and inflate the rock structural plane 73, in the process of inflation, the gas enters the pores and cracks of the rock structural plane 73 under the action of pressure, occupying the space that water can originally enter, if the air pressure is increased, the displacement effect will be enhanced, thereby reducing the area of the structural plane that can be infiltrated by water; then turn on the water pump 14 to inject water into the glass jar 8, and the water level is above the structural plane 73 by a certain height;

[0065] Step six, after the water completely infiltrates the structural plane 73, use the water pump 14 to pump out the water in the glass jar 8, turn off the water pump 14 and the air pump 13, control the vertical actuator 2 to lift to a certain height through the loading control system 12, remove the upper shear box 61 and the upper disc rock 71, take a photo to record the wet and dry state of the structural plane 73, calculate the infiltration area of the structural plane 73, and the water content of the structural plane 73 can be represented by the ratio of the infiltration area of the structural plane 73 to the total area of the structural plane 73, reset the upper shear box 61 and the upper disc rock 71, and repeat step five;

[0066] Step seven, control the first horizontal actuator 31 to contact the right side of the upper shear box 61 through the loading control system 12, control the vertical actuator 2 to apply a normal load to the top surface of the upper shear box 61 to a set value, and then control the second horizontal actuator 32 to apply a transverse shear load to the left side of the lower shear box 62 to a set value, until the sample is sheared and crept to failure or reaches a preset creep time, the water level in the glass jar 8 is always above the rock structural plane 73 during the test, and the loading control system 12 can collect load and displacement data in real time during the test.

[0067] In the present application, the relationship between the infiltration area and the air pressure is:

[0068] (1) In the rock structure plane, there are microstructures such as pores and cracks, which are the main channels for water infiltration and diffusion in the structure plane. When the structure plane is inflated, the gas will enter the pores and cracks. Inject water into the glass jar, let the water cover the structure plane to a certain height, and the water will flow into the structure plane along the water guide channel formed by the pores and cracks. According to the principle of fluid mechanics, the flow of water in the pores follows Darcy's law, which satisfies equation (1):

[0069] (1)

[0070] where Q is the seepage flow rate, Q is the permeability coefficient, K is the seepage cross-sectional area, A is the hydraulic slope, that is, the water head loss per unit length along the seepage direction. i

[0071] After injecting water, the glass jar, the structure plane water guide channel, the water, and the gas together constitute a fluid system, as shown in Figures 10-12 At this time, the gas pressure in the pores of the structure plane is equal to the pressure input by the external air pump. The existence of gas pressure in the pores will reduce the hydraulic slope and hinder the seepage of water. When the gas pressure in the pores increases, the hydraulic slope will decrease, and the seepage resistance of water in the pores will increase. When the gas pressure in the pores increases to a certain value, it is difficult for water to further diffuse in the structure plane, thereby reducing the wetting area. The above analysis shows that when the gas pressure is large enough, a dry area will be formed in the wet structure plane.

[0072] Further simplifying Figure 10 to Figure 11 , according to the principle of connected vessels and Pascal's law, without considering the influence of the structure plane on the water head loss, Figure 11 the system in equation (2) satisfies:

[0073] (2)

[0074] where is the density of water, is the standard atmospheric pressure, is the acceleration of gravity, is the vertical distance from the liquid surface in the glass jar to the structure plane, is the inflation pressure. When the inflation pressure increases to , as shown in Figure 12 , the system satisfies equation (3):

[0075] (3)

[0076] where is the density of water, ​P0 is the standard atmospheric pressure, g is the acceleration of gravity, h is the vertical distance from the liquid surface in the glass cylinder to the structure surface, P is the gas pressure.

[0077] Comparing equation (2) with equation (3), since > , so > , that is, the water level in the glass cylinder rises, and because the total volume of water in the system remains unchanged, the volume of water in the water guide channel decreases, that is, the volume of the gas increases > , which indicates that the increase in gas pressure increases the radius of the dry area, thereby increasing the area of the dry area of the structure surface and reducing the area of the wet area of the structure surface.

[0078] In addition, the shape, size, spatial distribution, and other characteristics of the water guide channel in the structure surface are highly random, which results in different resistances of each water guide channel. When the input pressure of the gas pump is increased, the gas tends to flow preferentially to the channel with the smallest resistance. As the gas pressure continuously increases, the gas in the channel with the smallest resistance reaches the edge of the structure surface first when the pressure reaches a certain value. At this time, if the pressure continues to be increased, the area of the dry area is difficult to further expand. Therefore, only by increasing the pressure within a specific pressure range can the area of the dry area be expanded. If the required dry area of the structure surface cannot be obtained by increasing the pressure, the required dry area of the structure surface can be obtained by inflating multiple inflation holes.

[0079] (2) From a microscopic perspective, the rock structure surface has many small pores, and water can infiltrate these pores through capillary action and other methods when there is no gas pressure. However, when the gas pressure increases, the filling and pressure effect of the gas on the pores change the pressure balance in the pores, making it difficult for water to enter some of the pores, thereby reducing the wet area of the structure surface.

[0080] After the structure surface is inflated and watered according to the method of the present application, the stability of the structure surface wetting is maintained, mainly based on the following aspects:

[0081] (1) The test device and test method are mainly used for the shear creep study of low-permeability rocks containing hard structure surfaces. For such rocks, the diffusion of water in the rock matrix can be ignored in the time scale of the laboratory shear creep, and only the seepage and diffusion of water in the pores or cracks of the rock structure surface are considered. The gas pressure formed during the inflation process forms a relatively stable pressure field in the pores and cracks of the structure surface. When the water level in the glass cylinder does not change, this pressure field hinders the flow of water, making the distribution of water in the structure surface relatively fixed.

[0082] (2) In the rock structure surface shear creep test, the structure surface creep rate is extremely low. According to previous research, the rock structure surface creep rate in the stable creep stage is usually not more than 10 -4 s -1 , and the final displacement is usually not more than 5 mm. In view of such small creep rate and creep displacement, the change of structure surface water content caused by the relative displacement of the upper and lower disc rocks can be basically ignored.

[0083] (3) The small gaps between the glass jar, the shear box and the rock, and the side surface of the rock sample are sealed (such as glass glue sealing). These sealing means effectively prevent the lateral leakage of water and avoid external interference. Through these sealing measures, water can only interact with the rock in a predetermined manner within the structure surface, thereby further improving the stability of the infiltration.

[0084] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A shear creep test apparatus capable of controlling the water content of a rock discontinuity, characterized by, The device comprises a direct shear apparatus, a water immersion device, an air filling device and a shear box (6), wherein the direct shear apparatus comprises a loading frame (1), a loading device and a sliding device mounted on the loading frame (1). The shear box (6) is used for containing a structural plane-containing rock sample (7) and comprises an upper shear box (61) and a lower shear box (62) arranged at intervals, wherein one side of the upper shear box (61) is provided with a first notch, one side of the lower shear box (62) is provided with a second notch, and the first notch and the second notch are oppositely arranged. The structural plane-containing rock sample (7) comprises an upper disc rock (71), a lower disc rock (72) and a structural plane (73), wherein the upper disc rock (71) is placed in the first notch of the upper shear box (61), the lower disc rock (72) is placed in the second notch of the lower shear box (62), the lower shear box (62) is placed on the sliding device, the upper disc rock (71) and the upper shear box (61) are placed on the lower disc rock (72), the surface of the upper disc rock (71) in contact with the lower disc rock (72) is the structural plane (73), the structural planes (73) of the upper disc rock (71) and the lower disc rock (72) are in alignment and contact, the structural plane (73) is located in the gap between the upper shear box (61) and the lower shear box (62), and the total height of the upper disc rock (71) and the lower disc rock (72) is greater than the total height of the inner cavities of the upper shear box (61) and the lower shear box (62). The water immersion device is arranged on the lower shear box (62) and is used for immersing the structural plane (73). The air filling device is connected to the upper shear box (61) and is used for filling air into the structural plane (73). The loading device is used for applying a normal load to the top of the upper shear box (61) and applying a lateral load to one side of the lower shear box (62). The air filling device comprises a high-pressure air pipe (10) and an air pump (13), a plurality of air inlet holes (63) are uniformly arranged on the front and back of the top of the upper shear box (61) along the rock width direction, the air inlet holes (63) are in communication with the first notch of the upper shear box (61), one side of the high-pressure air pipe (10) is connected to the air inlet holes (63), the other side of the high-pressure air pipe (10) extends to the outside of the loading frame (1) and is connected to the air pump (13), a plurality of structural plane air inlet holes (74) are arranged on the upper disc rock (71) according to the distribution positions of the air inlet holes (63), one side of the plurality of structural plane air inlet holes (74) is in communication with the plurality of air inlet holes (63), and the other side of the plurality of structural plane air inlet holes (74) is in communication with the structural plane (73). The direct shear apparatus further comprises a loading platform and a loading control system (12), wherein the loading platform is a concrete filling platform (5) arranged below the loading frame (1), and the loading control system (12) is arranged outside the loading frame (1).

2. The apparatus according to claim 1, wherein ​ The loading device comprises a vertical actuator (2), a first horizontal actuator (31), a second horizontal actuator (32), and a slide rail (4), each of which is fixed to the loading frame (1) and connected with the loading control system (12), wherein the vertical actuator (2) is fixed above the loading frame (1) and used to apply a normal load to the top of the upper shear box (61); the first horizontal actuator (31) is fixed to one side of the loading frame (1) and used to contact one side of the upper shear box (61); and the second horizontal actuator (32) is fixed to the other side of the loading frame (1) and used to apply a lateral load to one side of the lower shear box (62). The slide device comprises the slide rail (4) which is fixed to the loading platform and connected with the loading frame (1); and the lower shear box (62) is placed on the slide rail (4).

3. The apparatus according to claim 2, wherein The bottom of the lower shear box (62) is uniformly provided with a plurality of semispherical grooves, the grooves are provided with steel balls (9), the steel balls (9) are connected with the slide rail (4), and the grooves in the bottom of the lower shear box (62) and the surface of the steel balls (9) are coated with lubricating oil.

4. The apparatus according to claim 1, wherein The top of the upper shear box (61) is uniformly provided with three air inlet holes (63) along the rock width direction in the front, and the back of the top of the upper shear box (61) is provided with two air inlet holes (63) along the rock width direction, the five air inlet holes (63) respectively pass into the first notch of the upper shear box (61), and the outlets of the five air inlet holes (63) are uniformly distributed along two diagonal lines on the upper shear box (61). The air inlet hole (63) is provided with a thread, the end of the high-pressure air pipe (10) is provided with a threaded metal pipe, and the threaded metal pipe is screwed into the air inlet hole (63) by using the thread.

5. The apparatus according to claim 1, wherein The water immersion device comprises a glass jar (8), a water pipe (11), and a water pump (14), the glass jar (8) is placed on the outer wall above the lower shear box (62), the bottom of the glass jar (8) is provided with an opening (82), the opening (82) is aligned with the second notch of the lower shear box (62), the lower disc rock (72) is placed in the opening (82) and the second notch of the lower shear box (62), the upper part of the lower disc rock (72) is located in the glass jar (8), and the length and width of the opening (82) are equal to the length and width of the lower disc rock (72). The bottom of the glass jar (8) is provided with a water inlet (81), the water inlet (81) is connected with the water pump (14) through the water pipe (11) and used to inject water into the glass jar (8), and the injected water covers the structural plane (73).

6. The apparatus according to claim 5, wherein The tiny gap between the edges of the opening (82) and the second notch of the lower shear box (62) and the lower disc rock (72) is sealed by glass glue, the internal size of the glass jar (8) is greater than that of the upper shear box (61), and the distance between the inner wall of the glass jar (8) and the upper shear box (61) is greater than the shear creep displacement of the rock sample (7) with the structural plane.

7. The apparatus according to claim 1, wherein The structural plane containing rock sample (7) is a cube sample with equal side length, and the structural plane (73) is located at the position of 1 / 2 height of the cube sample and has an angle of 0° with the horizontal plane.

8. The apparatus according to claim 1, wherein The four sides of the structural plane containing rock sample (7) between the gaps of the upper shear box (61) and the lower shear box (62) are coated with glass glue.

9. A test method of the shear creep test apparatus capable of controlling the water state of a rock discontinuity according to any one of claims 1 to 8, characterized by, The method comprises the following steps: Step one: make the structural plane containing rock sample (7), the structural plane (73) is located at the position of 1 / 2 height of the sample and has an angle of 0° with the horizontal plane, 1-5 structural plane air inlet holes (74) are drilled on the upper disc rock (71) according to the distribution position of the air inlet holes (63) of the upper shear box (61), and the prepared structural plane containing rock sample (7) is placed in a drying box and baked to constant weight; Step two: place the first notch of the upper shear box (61) and the second notch of the lower shear box (62) upwards on the workbench, place the upper disc rock (71) in the first notch of the upper shear box (61), and place the lower disc rock (72) in the second notch of the lower shear box (62), then put the opening (82) at the bottom of the glass jar (8) over the lower disc rock (72) and place the glass jar (8) on the outer wall of the second notch of the lower shear box (62); Step three: use glass glue to seal the tiny gap between the edge of the opening (82) at the bottom of the glass jar (8) and the edge of the second notch of the lower shear box (62) and the structural plane containing rock sample (7) to prevent water from seeping into the shear box (6), and coat a layer of glass glue on the four sides of the structural plane containing rock sample (7) between the notch edges of the upper shear box (61) and the lower shear box (62) to prevent water from seeping into the structural plane containing rock sample (7) from the sides of the structural plane containing rock sample (7), and place the shear box (6) and the structural plane containing rock sample (7) coated with glue in a constant temperature curing box for curing; Step four: after the glass glue is dried and solidified, combine the upper disc rock (71) and the lower disc rock (72) according to the profile of the rock structural plane (73), place the shear box (6) at the loading position on the slide rail (4), connect one end of the high-pressure air pipe (10) to the air pump (13), twist the other end of the high-pressure air pipe (10) into the air inlet hole (63) of the upper shear box (61) corresponding to the desired drying position of the structural plane containing rock sample (7), connect one end of the water pipe (11) to the water pump (14), and connect the other end of the water pipe (11) to the water inlet (81) of the glass jar (8); Step five: control the vertical actuator (2) to apply a pre-tightening force to the top surface of the upper shear box (61) through the loading control system (12), open the air pump (13), adjust the air pressure to a predetermined value, inflate the structural plane (73), open the water pump (14), inject water into the glass jar (8), and the water level is higher than the structural plane (73). Step six, after the water completely infiltrates the structural plane (73), the water in the glass jar (8) is pumped out by the water pump (14), the water pump (14) and the air pump (13) are closed, the vertical actuator (2) is lifted by the loading control system (12), the upper shear box (61) and the upper disc rock (71) are removed, the wet and dry state of the structural plane (73) is recorded by taking pictures, the infiltration area of the structural plane (73) is calculated, the water content of the structural plane (73) is the ratio of the infiltration area of the structural plane (73) to the total area of the structural plane (73), the upper shear box (61) and the upper disc rock (71) are reset, and step five is repeated; Step seven, the first horizontal actuator (31) is in contact with the right side of the upper shear box (61) by the loading control system (12), the vertical actuator (2) applies a normal load to the top surface of the upper shear box (61) to a set value, the second horizontal actuator (32) applies a lateral shear load to the left side of the lower shear box (62) to a set value, until the sample is sheared and creeped or the preset creep time is reached, the water level in the glass jar (8) is always above the structural plane (73) during the test, and the loading control system (12) collects load and displacement data in real time during the test.

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