CN115436191A - Test method for researching shear mechanical properties of rock structural surface by combining photoelastic test - Google Patents
Test method for researching shear mechanical properties of rock structural surface by combining photoelastic test Download PDFInfo
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- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N2203/0025—Shearing
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Abstract
The invention provides a test method for researching the shearing mechanical property of a rock structural surface by combining a photoelastic test. The test method comprises the following steps: 1, adjusting a direct shear apparatus, and installing a sample; 2. adjusting the position of the shearing box, and performing test preparation work; 3. presetting target parameters and selecting a loading mode; 4. applying load, and collecting test images and data; 5. after the test is finished, the direct shear apparatus is reset, and data are stored; 6. and (5) image and data analysis work. The test method can be used for observing the changes of the stress field and the strain field of the test sample in the test process in real time according to various collected test data such as a stress optical diagram, load, displacement and the like and by combining preset target parameter values, drawing corresponding load-displacement curves and analyzing the influence of different loading conditions on the shearing mechanical property and the deformation characteristic of the rock structural plane.
Description
Technical Field
The invention relates to a test method for researching the shear mechanical property of a rock structural surface by combining a photoelastic test, belonging to the technical field of rock mechanical engineering.
Background
Under the action of long geology, the rock mass is cut by structural planes such as joints, faults, cracks and the like, and the mechanical behavior of the rock mass is controlled by the structural planes with extremely high discontinuity, criss-cross and complex cause. In actual engineering practice, shear deformation of a rock mass structural plane is a common failure mode in rock mass engineering, and the shear deformation can cause instability of a rock mass structure and induce geological disasters such as earthquake, rock burst and the like. Therefore, the research on the shearing mechanical property of the rock mass structural plane is beneficial to disclosing the destabilization mechanism and the damage mechanism of the fractured rock mass, and has very important significance on the whole process of design, construction, operation and maintenance of rock mass engineering.
At present, a plurality of technical means for observing the stress state of the rock joint exist, wherein the photoelastic test method can be used for visually simulating and researching the stress field change inside the rock joint and observing the shear deformation characteristic of the rock mass structural plane in real time, and has stronger superiority. Normally, a photoelastic test is performed on a photoelastic test platform, and the photoelastic test platform is formed by combining a whole set of devices, wherein the devices comprise a laser, a polarizer (1/4 wave plate), a loading device, an analyzer (1/4 wave plate), a camera and the like, but when the photoelastic test is performed, due to the limitation of the conditions such as the test device or a field and the like, most of the currently common test methods are performed under the condition of constant force, namely, under the condition that the test device keeps constant normal load and shear load, the shear mechanical property of a rock mass structural plane is researched and observed, and the influences of loading rate and deformation rate are not considered. However, this method has strong limitation, and is only suitable for simulating the destructive deformation process of the anchored rock body slope and deep engineering rock body when the structural plane is under the action of static load. For engineering rock masses in different environments, the stress environments of the engineering rock masses are different, and further, when a structural plane is damaged and deformed, the normal loading condition and the shearing loading condition are various, for example, for surrounding rock masses, anchoring rock mass side slopes and the like of deep chambers, because the rock mass after the chambers are excavated has an empty surface, under the action of ground stress, the initial shearing deformation of the rock structural plane can be generated, so that the shearing of the structural plane and the normal direction can be simultaneously subjected to the action of dynamic load, and in the dynamic change process, the dynamic normal direction and the shearing loading condition are adopted under the condition to be more in line with the engineering practice.
According to the situation, in the process of shear failure deformation of the rock mass structural plane, the normal and shear stresses are not kept static and unchanged, and the loading rate and the deformation rate of normal and shear loads are in dynamic change. When the shear mechanical properties of a rock mass structural plane are tested and researched in a laboratory at present, the considered loading condition is single, and the test is not designed completely according to the actual engineering condition. Therefore, there is inevitably a certain limitation in the application of the research results.
Disclosure of Invention
The invention aims to solve the technical problem that the dynamic damage deformation characteristic of a rock structural plane cannot be researched and observed by the conventional test method, and provides a test method for researching the shear mechanical characteristic of the rock structural plane by combining a photoelastic test. According to the problem to be researched, the proper loading rate and deformation rate are selected, and different stress environments of the engineering rock mass structural surface can be well simulated, so that a test basis is provided for researching the shearing mechanical property and the deformation property of the rock mass structural surface under the action of static load or dynamic load.
The invention adopts the following technical scheme for solving the technical problems:
a test method for researching the shearing mechanical property of a rock structural surface by combining a photoelastic test is based on a photoelastic test platform and a direct shear apparatus, and the direct shear apparatus comprises: base unit, loading unit, data acquisition unit, the control unit and cut the box:
the base unit is arranged at the bottom of the direct shear apparatus and used for bearing and supporting the weight of the whole direct shear apparatus, and comprises a bottom supporting plate and a first height adjusting mechanism connected between the bottom of the bottom supporting plate and the ground, a first linear guide rail moving pair is connected between the bottom of the bottom supporting plate and a photoelastic test platform, the position of the direct shear apparatus on the photoelastic test platform is adjusted through the first linear guide rail moving pair, and the height of the direct shear apparatus is adjusted through the first height adjusting mechanism, so that light paths can be sequentially aligned during photoelastic test to form continuity;
the loading unit is arranged on the upper side of the base unit and comprises a rigid frame, and a normal loading device, a shearing loading device and a supporting device which are arranged on the rigid frame, wherein the normal loading device and the shearing loading device are servo electric cylinders, the servo electric cylinder of the normal loading device is arranged at the top of the rigid frame, and the servo electric cylinder of the shearing loading device is arranged on the left side of the rigid frame;
the supporting device is used for supporting the shear box in the test process and comprises a first supporting device arranged on the right side of the rigid frame and a second supporting device arranged at the bottom of the rigid frame;
a vertical sliding groove is formed in the right side of the rigid frame, and the first supporting device is fastened on the vertical sliding groove through screws;
the second supporting device and the normal loading device are on the same straight line and are connected to the bottom of the rigid frame through a second height adjusting mechanism;
the data monitoring and collecting unit is arranged in the loading unit and used for monitoring and collecting test data in the test process, and comprises a normal pressure sensor, a tangential pressure sensor, a normal displacement sensor and a tangential displacement sensor;
the signal input end of the control unit is connected with the data monitoring and acquiring unit, and the signal output end of the control unit is connected with the loading unit;
the shearing box is used for placing a test sample and comprises an upper shearing box and a lower shearing box which have the same geometric dimension, and the front surface and the rear surface of the shearing box are not provided with shielding plates, so that a light source can pass through the sample and the continuity of a light path is ensured; grooves matched with the size of the sample are formed in the inner wall of the upper shearing box and the inner wall of the lower shearing box, and the sample is placed into the shearing boxes along the grooves and is tightly fixed;
the method comprises the following steps:
the method comprises the following steps: after the direct shear apparatus is electrified and started, the working lengths of the normal servo electric cylinder and the shearing servo electric cylinder are adjusted to the shortest state, the base unit is adjusted to be parallel to the bottom of the rigid frame, the direct shear apparatus is adjusted to the proper height and position, the prepared photoelastic test sample is placed into a shearing box to be fixed, and then the upper shearing box and the lower shearing box are respectively installed on the first top plate and the second top plate;
step two: adjusting the positions of the shearing box and the top plate to enable the center of the upper end face of the upper shearing box and the center of the driving end of the normal servo electric cylinder to be on the same straight line, enabling the center of the left side face of the lower shearing box and the center of the driving end of the shearing servo electric cylinder to be in the same horizontal position and keeping the initial state of the joint plane to be consistent;
step three: presetting target parameters by a control unit to select different loading modes, wherein the target parameters comprise: normal direction and shearing target load value, loading rate and deformation rate, controlling the normal direction servo electric cylinder and the shearing servo electric cylinder to respectively pre-load until the driving end of the servo electric cylinder is just completely contacted with the end face of the shearing box, keeping the shearing box stable, fixing the upper shearing box along the normal direction and the shearing direction at the moment, and having no displacement, fixing the lower shearing box along the normal direction of the joint face, only freely moving along the shearing direction, but not allowing the displacement along the normal direction of the joint face;
step four: if the loading mode is the static loading mode, controlling the normal electric cylinder and the shearing electric cylinder to apply normal load and shearing load to the sample at constant loading rate and constant deformation rate respectively and keeping the normal load and the shearing load static and constant; if the dynamic loading mode is adopted, after the normal load and the shearing load reach the target value, the normal electric cylinder or the shearing electric cylinder is continuously controlled to load the sample according to the preset loading rate and deformation rate, the test is ended until the normal or shearing displacement reaches a certain value, the control unit collects data of the sensor in the test process and processes the data into a corresponding curve, and meanwhile, a high-speed camera is used for shooting and recording pictures of sample change in the whole loading process in real time;
step five: after loading is finished, the loading device is reset, the load in the shearing direction is unloaded firstly, the normal load is fixed, so that the shearing direction is prevented from suddenly deforming when the normal load is unloaded, and the normal load is unloaded after the shearing loading device is not in contact with the shearing box; finally, taking down the shearing box, dismantling and cleaning the sample, and then carrying out the next group of tests;
step six: and after the test is finished, simulating and analyzing the shear mechanical property and the deformation characteristic of the rock mass structural plane according to the photoelastic test principle based on the image and various data acquired in the test process.
The first height adjusting mechanism comprises a foot cup and a supporting column, and the supporting column is installed on the foot cup through a first screw rod on the foot cup.
The rigid frame is provided with the strengthening rib in the inside and outside, vibration and shake appear in the staight scissors appearance when preventing to carry out photoelastic test loading, guarantee test platform's stability.
The driving end of the servo electric cylinder is connected with a floating joint, so that the servo electric cylinder is fully contacted with the shearing box during loading, and the load applied by the electric cylinder is completely transmitted to a sample.
Speed reducers are arranged on the servo electric cylinder of the normal loading device and the servo electric cylinder of the shearing loading device
The first supporting device comprises a screw, a first ejector rod and a first top plate; the first ejector rod is arranged on the right side of the rigid frame through a screw, and the top end of the first ejector rod is connected with the first top plate;
the second supporting device comprises a second screw rod, a second top plate and a sliding groove guide rail, the second top plate is installed on the low-resistance sliding groove guide rail, and the low-resistance sliding groove guide rail is fixed at the bottom of the rigid frame through the four second screw rods with adjustable heights.
A first sliding rail is arranged on the right side surface of the upper shearing box, a first sliding groove is formed in the first top plate, and the upper shearing box is mounted on the first sliding groove of the first top plate through the first sliding rail;
the bottom surface of the lower shearing box is provided with a second slide rail, a second slide groove is formed in the second top plate, and the lower shearing box is installed on the second slide groove of the second top plate through the second slide rail.
The shot image refers to a stress photoplethysmogram for photoelastic test analysis, and the collected test data comprises normal load, normal displacement, shear load and shear displacement;
the static loading mode refers to that the normal direction and the shearing load applied to the test sample are kept unchanged until the test is finished after the target value is reached;
the dynamic loading mode is divided into three conditions, namely a static normal-dynamic shearing loading mode, a dynamic normal-static shearing loading mode and a dynamic normal-dynamic shearing loading mode.
According to the shot and recorded stress optical diagram and the normal load, normal displacement, shearing load and shearing displacement data of the sample structural plane, the stress field and the strain field of the sample are calculated according to the photoelastic test principle, a normal load-normal displacement curve, a normal displacement-shearing displacement curve and a shearing load-shearing displacement curve are drawn, and the shearing mechanical property and the deformation characteristic of the rock structural plane are obtained through analysis.
Compared with the prior art, the technical scheme adopted by the invention has the following technical effects:
according to the photoelastic test principle, the test method can accurately analyze the shear mechanical property and deformation characteristic of the rock mass structural plane under different loading conditions based on the direct shear apparatus which is designed and developed by self, and ensures the accuracy and stability of the photoelastic test.
And secondly, by utilizing a control system of the direct shear apparatus, different loading rates and deformation rates can be set to realize rock mass structural plane shear tests in different loading modes, such as a static loading shear test and a dynamic loading shear test. .
Thirdly, the test method presets loading target parameters (normal and shearing target load values, loading rate and deformation rate) through controlling matched control software, further considers the shearing damage of the rock structure surface under different loading modes (static loading mode or dynamic loading mode), can reproduce the shearing damage process of the engineering rock mass more truly, is simple and easy to operate, and can provide a test basis for the research of the shearing mechanical property and the deformation characteristic of the rock structure surface.
Drawings
FIG. 1 is a flow chart of the test method;
FIG. 2 is a front view of the direct shear apparatus;
FIG. 3 is a schematic overall view of a photoelastic test platform;
FIG. 4 is a detail view of the shear box of the staight scissors apparatus;
FIG. 5 is a block diagram of the control principle of the direct shear apparatus;
fig. 6 is a control software interface diagram of the direct shear apparatus.
In the figure: 1 is a foot cup, 2 is a support column, 3 is a bottom support plate, 4 is a rigid frame, 5 is a screw, 6 is a first ejector rod, 7 is a first top plate, 8 is a normal pressure sensor, 9 is a normal floating joint, 10 is a normal servo electric cylinder, 11 is a normal displacement sensor, 12 is a shear displacement sensor, 13 is a shear servo electric cylinder, 14 is a shear floating joint, 15 is a shear pressure sensor, 16 is a triangular plate, 17 is a second lead screw, 18 is a second top plate, 19 is a low-resistance sliding groove guide rail, 20 is a lower shear box, 21 is an upper shear box, 22 is a sliding block, 23 is a reinforcing rib, 24 is a computer, 25 is an amplifying circuit, 26 is a signal processing circuit, 27 is control software, 28 is a display screen, 29 is a mouse and a keyboard.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
As shown in fig. 1, fig. 2, fig. 3, fig. 4, fig. 5, and fig. 6, the present invention provides a test method for researching the shear mechanical properties of a rock structural surface in combination with a photoelastic test, based on a photoelastic test platform, a direct shear apparatus capable of researching the shear mechanical properties of a rock joint in combination with a photoelastic test is installed on the photoelastic test platform, and the test method includes a base unit, a loading unit, a data monitoring and collecting unit, a control unit, and a shear box. The loading unit is located base unit upper portion, and the weight of whole direct shear appearance is supported to the base unit, and data monitoring and acquisition unit installs inside the loading unit, and the operation of direct shear appearance is controlled to the control unit.
The base unit comprises a first height adjustment mechanism and a bottom support plate 3. The first height adjusting mechanism is composed of four foot cups 1 and four supporting columns 2. The support column 2 is installed on the foot cup 1 through the first lead screw on the foot cup, and the bottom support plate 3 is installed on four support columns 2 through the bolt, realizes the adjustment of base height through rotating the foot cup lead screw to guaranteed that this staight scissors appearance can all carry out the photoelastic test under the condition of not co-altitude, also supported the staight scissors appearance and fix subaerial. Be connected with first linear guide rail sliding pair between bottom sprag board bottom and the photoelastic test platform, through first linear guide rail sliding pair adjusts the position of direct shear appearance on photoelastic test platform, adjusts through first height-adjustable mechanism the height of direct shear appearance for the light path can aim at in proper order when carrying out the photoelastic test, forms the continuity, and the material all adopts the stainless steel, and the biggest bearing can reach 200kg, as shown in fig. 2, 3.
The loading unit comprises a normal loading device, a shearing loading device and a supporting device. The highest loading rate and the highest deformation rate of the loading unit can respectively reach 5KN/s and 100mm/s, the highest loading load can reach 10KN, and the maximum test space can reach 100mm (normal direction) × 200mm (tangential direction). The normal loading device and the shearing loading device are both composed of a servo electric cylinder and a floating joint, and a speed reducer is mounted on the servo electric cylinder to ensure that the electric cylinder can realize stable stepless speed regulation. The supporting device is divided into a first supporting device positioned on the right side of the rigid frame and a second supporting device positioned at the bottom of the rigid frame, the first supporting device is composed of a screw 5, a first ejector rod 6 and a first top plate 7 from right to left, and the second supporting device is composed of a second top plate 18, a chute guide rail 19 and four second screw rods 17 from top to bottom.
The rigid frame 4 is made of multi-layer stainless steel materials, the inner side of the rigid frame is provided with the set square 16, and reinforcing ribs 23 are arranged on the inner side and the outer side of the rigid frame for reinforcement, so that the rigid frame is guaranteed not to deform in the test loading process, and the direct shear apparatus is prevented from vibrating or shaking to influence the test result. The normal loading device and the shearing loading device are respectively arranged at the top and the left side of the rigid frame 4, the floating joint is arranged on the servo electric cylinder, the full contact with the shearing box is ensured during loading, and then the load applied by the electric cylinder is completely transferred to the sample. The top plate 7 of the first supporting device is mounted on a first top rod 6, the first top rod is fixed on the right side of the rigid frame 4 through a screw 5, and the first top rod 6 is a telescopic rod.
The second supporting device and the normal loading device are in the same straight line, the second top plate 18 is installed on the low-resistance chute guide rail 19 and is fixed at the bottom of the rigid frame 4 through four second screw rods 17 with adjustable heights, so that the shearing box can horizontally slide left and right in the tangential direction, and the influence of friction force on the test is avoided to the greatest extent. The length and the position of the first supporting device and the second supporting device can be adjusted, so that the light source can completely penetrate through the sample, and the continuity of the light path and the stability of the test are guaranteed. The first top plate 7 and the second top plate 18 are provided with sliding grooves which are matched with the sliding rails on the right side surface of the upper shearing box 21 and the bottom surface of the lower shearing box 20, so that the shearing boxes are limited to slide along a specific direction during testing, as shown in fig. 2 and 3.
The data monitoring and acquisition unit comprises a normal pressure sensor 8, a normal displacement sensor 11, a shearing pressure sensor 15, a shearing displacement sensor 11 and a signal processing circuit 26 which are connected with a computer. The pressure sensor is arranged on the floating joint, and can monitor and collect the load applied to the sample in real time. The displacement sensors are respectively arranged on the servo electric cylinders, and can monitor and collect the deformation displacement of the sample in real time, as shown in figures 2 and 3.
The control unit comprises a computer 24, an amplification circuit 25, a signal processing circuit 26, control software 27 and a display 28. Data collected by the sensor is processed by the signal processing circuit 26 and then transmitted to the control software 27 through the amplifying circuit 25, one end of the computer 24 is connected with the control software 27, and the other end of the computer is connected with the loading unit. The display screen 28 will display a self-designed matching control software interface 27, and different loading modes, namely static loading mode and dynamic loading mode, can be realized by setting the normal and shearing target load values, loading rate and deformation rate of target parameters in the test through the control software. The data and the target parameters acquired by the sensors are acquired as output signals and stored in the computer 24, and the output signals are processed by the computer 24 and then serve as input signals of a servo loading mechanism to form closed-loop control of the direct shear apparatus. The display 28 displays the loading rate, deformation rate, displacement and load, as well as the load-time curve and the displacement-time curve in real time. The control software 27 is later upgraded to meet new loading pattern or parameter requirements as shown in figures 5 and 6.
The shear box is used for placing photoelastic samples and comprises an upper shear box 21 and a lower shear box 20 which are the same in geometric dimension, and the front surface and the rear surface of the shear box are not provided with shielding plates, so that the deformation damage process of the joint samples is shot and recorded by a high-speed camera. The inner walls of the upper shearing box and the lower shearing box are provided with grooves, and a sample is placed into the shearing box along the grooves and is tightly fixed, so that the sample cannot slip or dislocate in the test process. The right side surface of the upper cutting box 21 and the bottom surface of the lower cutting box 20 are provided with slide rails which are matched with the slide grooves of the first top plate 7 and the second top plate 18 respectively. Ensuring that the upper shear box 21 is free to move normal to the joint plane but cannot be displaced in the shear direction; the lower shear box 20 is free to move in the shear direction but cannot be displaced in the normal direction of the joint plane, ensuring that the test is performed stably, as shown in figures 2, 3 and 4.
The embodiments of the invention are shown below:
example 1
The test method for researching the shear mechanical property of the rock mass structural plane in the static loading mode comprises the following steps:
the method comprises the following steps: after the direct shear apparatus is started by plugging electricity, the working lengths of the normal servo electric cylinder and the shearing servo electric cylinder are adjusted to be in the shortest state, the base unit is adjusted to be parallel and level with the bottom of the rigid frame, the direct shear apparatus is adjusted to be at a proper height and position, the prepared photoelastic test sample is placed into a shearing box to be fixed, and then the upper shearing box and the lower shearing box are respectively installed on the first top plate and the second top plate;
step two: adjusting the positions of the shearing box and the top plate to enable the center of the upper end face of the upper shearing box and the center of the driving end of the normal servo electric cylinder to be on the same straight line, enabling the center of the left side face of the lower shearing box and the center of the driving end of the shearing servo electric cylinder to be in the same horizontal position and keeping the initial state of the joint face to be consistent;
step three: presetting target parameters through a control unit, wherein the target parameters comprise: normal direction and shearing target load value, loading rate and deformation rate, controlling the normal direction servo electric cylinder and the shearing servo electric cylinder to respectively pre-load until the driving end of the servo electric cylinder is just completely contacted with the end face of the shearing box, keeping the shearing box stable, fixing the upper shearing box along the normal direction and the shearing direction at the moment, and having no displacement, fixing the lower shearing box along the normal direction of the joint face, only freely moving along the shearing direction, but not allowing the displacement along the normal direction of the joint face;
step four: controlling a normal electric cylinder and a shearing electric cylinder to apply normal load and shearing load to a sample at constant loading rate and constant deformation rate respectively, keeping the normal load and the shearing load static and constant until a preset time is reached, finishing the test, acquiring data of a sensor in the test process by a control unit, processing the data into a corresponding curve, and simultaneously shooting and recording a picture of the change of the sample in the whole loading process in real time by using a high-speed camera;
step five: after loading is finished, the loading device is reset, the load in the shearing direction is unloaded firstly, the normal load is fixed, so that the shearing direction is prevented from suddenly deforming when the normal load is unloaded, and the normal load is unloaded after the shearing loading device is not in contact with the shearing box; finally, taking down the shearing box, dismantling and cleaning the sample, and then carrying out the next group of tests;
step six: and after the test is finished, simulating and analyzing the shear mechanical property and the deformation characteristic of the rock mass structural plane according to the photoelastic test principle based on the image and various data acquired in the test process.
Example 2
The test method for researching the shear mechanical properties of the rock mass structural plane in the dynamic normal-dynamic shear loading mode comprises the following steps:
the method comprises the following steps: after the direct shear apparatus is started by plugging electricity, the working lengths of the normal servo electric cylinder and the shearing servo electric cylinder are adjusted to be in the shortest state, the base unit is adjusted to be parallel and level with the bottom of the rigid frame, the direct shear apparatus is adjusted to be at a proper height and position, the prepared photoelastic test sample is placed into a shearing box to be fixed, and then the upper shearing box and the lower shearing box are respectively installed on the first top plate and the second top plate;
step two: adjusting the positions of the shearing box and the top plate to enable the center of the upper end face of the upper shearing box and the center of the driving end of the normal servo electric cylinder to be on the same straight line, enabling the center of the left side face of the lower shearing box and the center of the driving end of the shearing servo electric cylinder to be in the same horizontal position and keeping the initial state of the joint face to be consistent;
step three: presetting target parameters through a control unit, wherein the target parameters comprise: normal direction and shearing target load value, loading rate and deformation rate, controlling the normal direction servo electric cylinder and the shearing servo electric cylinder to respectively pre-load until the driving end of the servo electric cylinder is just completely contacted with the end face of the shearing box, keeping the shearing box stable, fixing the upper shearing box along the normal direction and the shearing direction at the moment, and having no displacement, fixing the lower shearing box along the normal direction of the joint face, only freely moving along the shearing direction, but not allowing the displacement along the normal direction of the joint face;
step four: after controlling the normal electric cylinder and the shearing electric cylinder to apply normal load and shearing load to the sample at constant loading rate and constant deformation rate respectively to reach a target value, continuously controlling the normal electric cylinder and the shearing electric cylinder to load the sample according to preset loading rate and preset deformation rate until the normal displacement and the shearing displacement reach a certain value, ending the test, acquiring data of a sensor in the test process by a control unit, processing the data into a corresponding curve, and simultaneously shooting and recording pictures of the change of the sample in the whole loading process in real time by using a high-speed camera;
step five: after loading is finished, the loading device is reset, the load in the shearing direction is unloaded firstly, the normal load is fixed, so that the shearing direction is prevented from suddenly deforming when the normal load is unloaded, and the normal load is unloaded after the shearing loading device is not in contact with the shearing box; and finally, taking down the shearing box, dismantling and cleaning the sample, and then carrying out the next group of tests.
Step six: and after the test is finished, simulating and analyzing the shear mechanical property and the deformation characteristic of the rock mass structural plane according to the photoelastic test principle based on the image and various data acquired in the test process.
Example 3
The test method for researching the shear mechanical property of the rock mass structural plane in the static normal-dynamic shear loading mode comprises the following steps:
based on the embodiment 2, after the normal load and the shear load are applied to the sample at constant loading rate and deformation rate respectively by the normal loading device and the shear loading device of the direct shear apparatus in the fourth step, the normal loading device keeps the load target value unchanged, and the shear loading device is only required to continuously load the sample at the preset loading rate and deformation rate.
Example 4
The test method for researching the shear mechanical properties of the rock mass structural plane in the dynamic normal-static shear loading mode comprises the following steps:
based on the embodiment 2, in the fourth step, after the normal load and the shear load are applied to the sample at constant loading rate and deformation rate respectively by the normal loading device and the shear loading device of the direct shear apparatus to reach the target value, the shear loading device keeps the target value of the load, and the normal loading device is only required to continuously load the sample at the preset loading rate and deformation rate.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The above embodiments are only for illustrating the technical idea of the present invention, and the technical idea of the present invention is not limited thereto, and any modifications made on the basis of the technical solution according to the technical idea of the present invention fall within the protective scope of the present invention. While the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.
Claims (9)
1. A test method for researching the shearing mechanical property of a rock structural surface by combining a photoelastic test is based on a photoelastic test platform and a direct shear apparatus, and the direct shear apparatus comprises: base unit, loading unit, data acquisition unit, the control unit and shearing box:
the base unit is arranged at the bottom of the direct shear apparatus and used for bearing and supporting the weight of the whole direct shear apparatus, and comprises a bottom supporting plate and a first height adjusting mechanism connected between the bottom of the bottom supporting plate and the ground, a first linear guide rail moving pair is connected between the bottom of the bottom supporting plate and the photoelastic test platform, the position of the direct shear apparatus on the photoelastic test platform is adjusted through the first linear guide rail moving pair, the height of the direct shear apparatus is adjusted through the first height adjusting mechanism, so that light paths can be sequentially aligned during photoelastic test, and continuity is formed;
the loading unit is arranged on the upper side of the base unit and comprises a rigid frame, and a normal loading device, a shearing loading device and a supporting device which are arranged on the rigid frame, wherein the normal loading device and the shearing loading device are servo electric cylinders, the servo electric cylinder of the normal loading device is arranged at the top of the rigid frame, and the servo electric cylinder of the shearing loading device is arranged on the left side of the rigid frame;
the supporting device is used for supporting the shear box in the test process and comprises a first supporting device arranged on the right side of the rigid frame and a second supporting device arranged at the bottom of the rigid frame;
a vertical sliding groove is formed in the right side of the rigid frame, and the first supporting device is fastened on the vertical sliding groove through a screw;
the second supporting device and the normal loading device are on the same straight line and are connected to the bottom of the rigid frame through a second height adjusting mechanism;
the data monitoring and collecting unit is arranged in the loading unit, is used for monitoring and collecting test data in the test process, and comprises a normal pressure sensor, a tangential pressure sensor, a normal displacement sensor and a tangential displacement sensor;
the signal input end of the control unit is connected with the data monitoring and acquiring unit, and the signal output end of the control unit is connected with the loading unit;
the shearing box is used for placing a test sample and comprises an upper shearing box and a lower shearing box which have the same geometric dimension, and the front surface and the rear surface of the shearing box are not provided with shielding plates, so that a light source can pass through the sample and the continuity of a light path is ensured; grooves matched with the size of the sample are formed in the inner wall of the upper shearing box and the inner wall of the lower shearing box, and the sample is placed into the shearing boxes along the grooves and is tightly fixed;
the method is characterized by comprising the following steps:
the method comprises the following steps: after the direct shear apparatus is started by plugging electricity, the working lengths of the normal servo electric cylinder and the shearing servo electric cylinder are adjusted to be in the shortest state, the base unit is adjusted to be parallel and level with the bottom of the rigid frame, the direct shear apparatus is adjusted to be at a proper height and position, the prepared photoelastic test sample is placed into a shearing box to be fixed, and then the upper shearing box and the lower shearing box are respectively installed on the first top plate and the second top plate;
step two: adjusting the positions of the shearing box and the top plate to enable the center of the upper end face of the upper shearing box and the center of the driving end of the normal servo electric cylinder to be on the same straight line, enabling the center of the left side face of the lower shearing box and the center of the driving end of the shearing servo electric cylinder to be in the same horizontal position and keeping the initial state of the joint face to be consistent;
step three: presetting target parameters by a control unit to select different loading modes, wherein the target parameters comprise: normal direction and shearing target load value, loading rate and deformation rate, controlling the normal direction servo electric cylinder and the shearing servo electric cylinder to respectively pre-load until the driving end of the servo electric cylinder is just completely contacted with the end face of the shearing box, keeping the shearing box stable, fixing the upper shearing box along the normal direction and the shearing direction at the moment, and having no displacement, fixing the lower shearing box along the normal direction of the joint face, only freely moving along the shearing direction, but not allowing the displacement along the normal direction of the joint face;
step four: if the loading mode is a static loading mode, controlling the normal electric cylinder and the shearing electric cylinder to apply normal load and shearing load to the sample at constant loading rate and deformation rate respectively and keeping the normal load and the shearing load static and constant after the normal load and the shearing load are applied to the sample to a target value; if the dynamic loading mode is adopted, after the normal load and the shearing load reach the target value, the normal electric cylinder or the shearing electric cylinder is continuously controlled to load the sample according to the preset loading rate and deformation rate, the test is ended until the normal or shearing displacement reaches a certain value, the control unit collects data of the sensor in the test process and processes the data into a corresponding curve, and meanwhile, a high-speed camera is used for shooting and recording pictures of sample change in the whole loading process in real time;
step five: after loading is finished, the loading device is reset, the load in the shearing direction is unloaded firstly, the normal load is not moved, so that the shearing direction is prevented from suddenly deforming when the normal load is unloaded, and the normal load is unloaded after the shearing loading device is not contacted with the shearing box; finally, taking down the shearing box, dismantling and cleaning the sample, and then carrying out the next group of tests;
step six: and after the test is finished, simulating and analyzing the shear mechanical property and the deformation characteristic of the rock mass structural plane according to the photoelastic test principle based on the image and various data acquired in the test process.
2. The test method for researching the shear mechanical property of the rock structural surface by combining the photoelastic test according to claim 1, is characterized in that: the first height adjusting mechanism comprises a foot cup and a supporting column, and the supporting column is installed on the foot cup through a first screw rod on the foot cup.
3. The test method for researching the shear mechanical property of the rock structural plane by combining the photoelastic test according to claim 1, characterized in that: the rigid frame is provided with the strengthening rib in the inside and outside, vibration and shake appear in the staight scissors appearance when preventing to carry out photoelastic test loading, guarantee test platform's stability.
4. The test method for researching the shear mechanical property of the rock structural surface by combining the photoelastic test according to claim 1, is characterized in that: the driving end of the servo electric cylinder is connected with a floating joint, so that the servo electric cylinder is fully contacted with the shearing box during loading, and the load applied by the electric cylinder is completely transmitted to the sample.
5. The test method for researching the shear mechanical property of the rock structural plane by combining the photoelastic test according to claim 1, characterized in that: and speed reducers are arranged on the servo electric cylinder of the normal loading device and the servo electric cylinder of the shearing loading device.
6. The test method for researching the shear mechanical property of the rock structural plane by combining the photoelastic test according to claim 1, characterized in that: the first supporting device comprises a screw, a first ejector rod and a first top plate; the first ejector rod is installed on the right side of the rigid frame through a screw, and the top end of the first ejector rod is connected with the first top plate;
the second supporting device comprises a second screw rod, a second top plate and a chute guide rail, the second top plate is installed on the low-resistance chute guide rail, and the low-resistance chute guide rail is fixed at the bottom of the rigid frame through four second screw rods with adjustable heights.
7. A first sliding rail is arranged on the right side face of the upper shearing box, a first sliding groove is formed in the first top plate, and the upper shearing box is mounted on the first sliding groove of the first top plate through the first sliding rail;
the bottom surface of the lower shearing box is provided with a second slide rail, a second slide groove is formed in the second top plate, and the lower shearing box is installed on the second slide groove of the second top plate through the second slide rail.
8. The test method for researching the shear mechanical property of the rock structural plane by combining the photoelastic test is characterized in that: the shot image refers to a stress photopgram for photoelastic test analysis, and the collected test data comprises normal load, normal displacement, shear load and shear displacement;
the static loading mode refers to that the normal direction and the shearing load applied to the test sample are kept unchanged until the test is finished after the target value is reached;
the dynamic loading mode is divided into three conditions of a static normal-dynamic shearing loading mode, a dynamic normal-static shearing loading mode and a dynamic normal-dynamic shearing loading mode.
9. The test method for researching the shear mechanical property of the rock structural plane by combining the photoelastic test according to claim 1, characterized in that: according to the shot and recorded stress optical diagram and the normal load, normal displacement, shearing load and shearing displacement data of the sample structural plane, the stress field and the strain field of the sample are calculated according to the photoelastic test principle, a normal load-normal displacement curve, a normal displacement-shearing displacement curve and a shearing load-shearing displacement curve are drawn, and the shearing mechanical property and the deformation characteristic of the rock structural plane are obtained through analysis.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116148058A (en) * | 2023-01-04 | 2023-05-23 | 山东科技大学 | Rock mass true triaxial indoor test method based on first unloading and then anchoring |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116148058A (en) * | 2023-01-04 | 2023-05-23 | 山东科技大学 | Rock mass true triaxial indoor test method based on first unloading and then anchoring |
| CN116148058B (en) * | 2023-01-04 | 2024-01-30 | 山东科技大学 | Rock mass true triaxial indoor test method based on first unloading and then anchoring |
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