CN110646284A - Multi-axis loading and water saturation coupling type rock three-point bending experimental device and method - Google Patents
Multi-axis loading and water saturation coupling type rock three-point bending experimental device and method Download PDFInfo
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- 239000011435 rock Substances 0.000 title claims abstract description 164
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 99
- 238000000034 method Methods 0.000 title claims abstract description 26
- 238000013001 point bending Methods 0.000 title claims description 27
- 230000008878 coupling Effects 0.000 title claims description 10
- 238000010168 coupling process Methods 0.000 title claims description 10
- 238000005859 coupling reaction Methods 0.000 title claims description 10
- 238000007789 sealing Methods 0.000 claims abstract description 20
- 238000012545 processing Methods 0.000 claims abstract description 5
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 5
- 238000006073 displacement reaction Methods 0.000 claims description 47
- 229920001971 elastomer Polymers 0.000 claims description 40
- 238000002474 experimental method Methods 0.000 claims description 13
- 239000012153 distilled water Substances 0.000 claims description 8
- 238000007599 discharging Methods 0.000 claims description 5
- 230000002457 bidirectional effect Effects 0.000 claims description 3
- 238000002347 injection Methods 0.000 claims description 3
- 239000007924 injection Substances 0.000 claims description 3
- 239000000463 material Substances 0.000 description 7
- 230000007547 defect Effects 0.000 description 3
- 239000007769 metal material Substances 0.000 description 3
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- 238000003754 machining Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 238000009412 basement excavation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 230000001808 coupling effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000007656 fracture toughness test Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
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- G01N2203/006—Crack, flaws, fracture or rupture
- G01N2203/0062—Crack or flaws
- G01N2203/0066—Propagation of crack
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Abstract
A pressure chamber of the device is provided with a vertical actuator and two horizontal contraposition actuators, a rock sample is arranged at the inner bottom of the pressure chamber below the vertical actuator through a sample support, two lower support point rollers are symmetrically arranged on the sample support, an upper support point roller is arranged on the vertical actuator, and the upper support point roller is positioned above the middle of the two lower support point rollers. The method comprises the following steps: preparing a rock sample and processing an artificial crack; carrying out water saturation treatment on the sample; placing a water-saturated sample on the lower fulcrum roller, and centering the artificial crack downwards; applying a horizontal clamping force to the sample by two horizontally opposed actuators; sealing the pressure chamber, injecting water and applying water pressure to simulate the underground water-saturated pressure environment; applying a downward pressure to the sample through a vertical actuator; and collecting and storing data. When the underground water saturation pressure environment does not need to be simulated, stress is applied to the water saturation sample only through the three actuators, and the crack propagation process is synchronously observed through a microscope.
Description
Technical Field
The invention belongs to the technical field of rock fracture mechanics experiments, and particularly relates to a multi-axis loading and water saturation coupling type rock three-point bending experimental device and method.
Background
In 1920, British physicist Griffith found that the internal defects of the material determine the strength of the material based on experimental study of the crack generation rule in glass, and the established brittle material fracture theory lays a theoretical foundation for fracture mechanics, and the research range of the fracture mechanics is gradually expanded from metal materials to rock materials.
The biggest difference between rock materials and metal materials is that a large number of natural defects exist in the rock and the rock is composed of multiphase minerals, deep rock mass fracture is caused by external force such as external plate tectonic stress, engineering blasting excavation disturbance stress and the like, and internal defect crack propagation and fracture show fracture from mm level to km level, while rock in the earth crust is in three-dimensional stress (sigma)1≥σ2≥σ3) In the state, the underground water pressure also acts on the rock together sometimes, and the underground rock engineering design is not enough only depending on the rock strength index.
The rock failure experiment mainly comprises static loading failure, rheological failure, dynamic impact failure and the like, wherein the failures are related to internal crack density and crack expansion rate, rock fracture mechanics research is a basic direction of rock engineering design, the traditional rock material fracture toughness test technology always refers to a metal material fracture toughness testing device and method, in short, a sample is placed on two supporting points with a certain distance, downward load is applied to the sample above the middle point of the two supporting points, three-point bending occurs when 3 contact points of the sample form two equal moments, and the sample is subjected to tensile fracture at the middle point. However, the existing three-point bending experiments are all completed under the one-dimensional stress condition, the three-dimensional stress state of the underground rock and the coupling effect of underground water are not considered at all, and the fracture toughness experiment result of the rock material is obtained under the one-dimensional condition, so that the fracture toughness experiment result has limitation in explaining the three-dimensional fracture mechanism of the underground rock.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a multi-axis loading and water saturation coupling type rock three-point bending experimental device and method, which can effectively simulate the coupling state of a rock and underground water under three-dimensional stress, carry out a three-point bending experiment in the state, ensure that the experimental result is more real and reliable, not only can provide experimental data explanation for rock mass fracture instability in the deep tunnel engineering, deep shale gas development engineering and deep metal mine exploitation processes, but also can provide explanation basis for earthquake induction reasons.
In order to achieve the purpose, the invention adopts the following technical scheme: a multi-axis loading and water saturation coupling type rock three-point bending experimental device comprises a pressure chamber, a first actuator, a second actuator, a third actuator and a sample support; the first actuator is vertically arranged at the top of the pressure chamber, the sample support is vertically and fixedly arranged at the bottom of the inner side of the pressure chamber right below the first actuator, and the second actuator and the third actuator are horizontally and symmetrically arranged at the left side and the right side of the pressure chamber; a lower fulcrum roller limiting table is fixedly arranged at the top end of the sample support, a plurality of lower fulcrum roller limiting grooves are formed in the upper surface of the lower fulcrum roller limiting table, the plurality of lower fulcrum roller limiting grooves are distributed in parallel at equal intervals, a first lower fulcrum roller and a second lower fulcrum roller are symmetrically arranged in the lower fulcrum roller limiting grooves, and a rock sample is placed on the first lower fulcrum roller and the second lower fulcrum roller; a first force transducer is fixedly arranged at the end part of a piston rod of the first actuator, a first pressure-bearing cushion block is fixedly connected to the bottom end of the first force transducer, an upper fulcrum roller limiting groove is formed in the lower surface of the first pressure-bearing cushion block, an upper fulcrum roller is arranged in the upper fulcrum roller limiting groove and is in abutting contact with a rock sample, and the upper fulcrum roller is positioned right above the middle point of the first lower fulcrum roller and the second lower fulcrum roller; a second force transducer is fixedly arranged at the end part of a piston rod of the second actuator, a second pressure-bearing cushion block is fixedly connected to the side surface of the second force transducer, a first rubber pad is fixedly connected to the side surface of the second pressure-bearing cushion block, and the first rubber pad is abutted against and contacted with a rock sample; a third force transducer is fixedly arranged at the end part of a piston rod of the third actuator, a third pressure-bearing cushion block is fixedly connected to the side surface of the third force transducer, a second rubber pad is fixedly connected to the side surface of the third pressure-bearing cushion block, and the second rubber pad is abutted and contacted with a rock sample; the bottom of the pressure chamber is provided with a water inlet and outlet, and the top of the pressure chamber is provided with a gas inlet and outlet.
Both sides all are equipped with sealing door around the pressure chamber, all install transparent observation window on every sealing door, and sealing door adopts whole detachable structure.
A multi-axis loading and water saturation coupled rock three-point bending experimental method adopts the multi-axis loading and water saturation coupled rock three-point bending experimental device, and comprises the following steps:
the method comprises the following steps: preparing a rock sample, and inwards processing an artificial crack at the middle position of one surface of the rock sample; meanwhile, an LVDT displacement sensor is vertically arranged between the first pressure bearing cushion block and the sample support;
step two: immersing the rock sample with the artificial crack in distilled water until the rock sample reaches a water saturation state;
step three: sending the rock sample in a water saturation state into a pressure chamber, placing the rock sample on a first lower fulcrum roller and a second lower fulcrum roller, and enabling an artificial crack to face downwards and to be located in the middle of the first lower fulcrum roller and the second lower fulcrum roller;
step four: the piston rods of the second actuator and the third actuator are driven to synchronously extend in a displacement control mode until the first rubber pad and the second rubber pad are abutted and contacted with the side surface of the rock sample, so that the rock sample is centered and clamped, and then the piston rods of the second actuator and the third actuator are driven in a force control mode to apply horizontal clamping force to the rock sample;
step five: installing a sealing door on the pressure chamber, completing the sealing of the pressure chamber, communicating a water inlet and outlet with a water supply source, injecting water into the pressure chamber, discharging air in the pressure chamber through a water inlet and outlet in the water injection process, when water flows out from the water inlet and outlet, indicating that the water in the pressure chamber is filled, closing the water inlet and outlet, and finally completing the water pressure application in the pressure chamber to simulate the underground water-saturated pressure environment;
step six: a piston rod of a first actuator is driven to extend downwards in a displacement control mode until an upper supporting point roller is abutted and contacted with the upper surface of the rock sample, and then the piston rod of the first actuator applies downward force to the rock sample in the displacement control mode;
step seven: observing a stress-displacement curve in a computer, continuously loading for a period of time after the stress-displacement curve reaches a peak value, stopping loading, and storing the acquired experimental data;
step eight: firstly, a piston rod of a first actuator is driven to move upwards in a displacement control mode, so that an upper supporting point roller is separated from the upper surface of a rock sample, and unloading of downward pressure is completed; then piston rods of the second actuator and the third actuator are driven to synchronously retract in a displacement control mode, so that the first rubber pad and the second rubber pad are separated from the side surface of the rock sample, and the unloading of the horizontal clamping force is completed;
step nine: unloading the water pressure in the pressure chamber, opening the closed air inlet and outlet, and finally discharging all the water in the pressure chamber through the water inlet and outlet;
step ten: the sealing door is detached from the pressure chamber, the rock sample is taken out, and the crack expansion condition on the rock sample is observed; meanwhile, the acquired data are analyzed and calculated, and the fracture toughness and the tensile strength of the rock sample are obtained.
A multi-axis loading and water saturation coupled rock three-point bending experimental method adopts the multi-axis loading and water saturation coupled rock three-point bending experimental device, and when an underground water saturation pressure environment does not need to be simulated, the method comprises the following steps:
the method comprises the following steps: preparing a rock sample, and inwards processing an artificial crack at the middle position of one surface of the rock sample; meanwhile, an LVDT displacement sensor is vertically arranged between the first pressure bearing cushion block and the sample support;
step two: immersing the rock sample with the artificial crack in distilled water until the rock sample reaches a water saturation state;
step three: sending the rock sample in a water saturation state into a pressure chamber, placing the rock sample on a first lower fulcrum roller and a second lower fulcrum roller, and enabling the artificial crack to face downwards and to be located in the middle of the first lower fulcrum roller and the second lower fulcrum roller;
step four: the piston rods of the second actuator and the third actuator are driven to synchronously extend in a displacement control mode until the first rubber pad and the second rubber pad are abutted and contacted with the side surface of the rock sample, so that the rock sample is centered and clamped, and then the piston rods of the second actuator and the third actuator are driven in a force control mode to apply horizontal clamping force to the rock sample;
step five: a super-depth-of-field three-dimensional microscope is arranged in front of a rock sample, the super-depth-of-field three-dimensional microscope is directly and fixedly connected to a pressure chamber through a microscope support, and a horizontal bidirectional sliding table is arranged between the microscope support and the super-depth-of-field three-dimensional microscope; moving the super-depth-of-field three-dimensional microscope to enable a lens of the super-depth-of-field three-dimensional microscope to be opposite to the artificial crack of the rock sample;
step six: a piston rod of a first actuator is driven to extend downwards in a low-speed displacement control mode until an upper supporting point roller is abutted and contacted with the upper surface of the rock sample, then the piston rod of the first actuator applies downward pressure to the rock sample in a displacement control mode, and data measured by an LVDT displacement sensor is recorded; meanwhile, synchronously observing the microscopic expansion process of the artificial crack of the rock sample through a super-depth-of-field three-dimensional microscope;
step seven: firstly, a piston rod of a first actuator is driven to move upwards in a displacement control mode, so that an upper supporting point roller is separated from the upper surface of a rock sample, and unloading of downward pressure is completed; then piston rods of the second actuator and the third actuator are driven to synchronously retract in a displacement control mode, so that the first rubber pad and the second rubber pad are separated from the side surface of the rock sample, and the unloading of the horizontal clamping force is completed; and finally, taking down the rock sample.
The invention has the beneficial effects that:
the multi-axis loading and water saturation coupling type rock three-point bending experimental device and method can effectively simulate the coupling state of the rock and underground water under three-dimensional stress, and carry out three-point bending experiment under the state, so that the experimental result is more real and reliable, experimental data explanation can be provided for rock mass fracture instability in deep tunnel engineering, deep shale gas development engineering and deep metal mine exploitation processes, and explanation basis can be provided for earthquake induction reasons.
Drawings
FIG. 1 is a front view of a multi-axis loading and water saturation coupled rock three-point bending experimental device according to the present invention;
FIG. 2 is a side view of a multi-axis loading and water saturation coupled rock three-point bending experimental device according to the present invention;
in the figure, 1-pressure chamber, 2-first actuator, 3-second actuator, 4-third actuator, 5-sample support, 6-lower fulcrum roller limit table, 7-lower fulcrum roller limit groove, 8-first lower fulcrum roller, 9-second lower fulcrum roller, 10-rock sample, 11-first force transducer, 12-first pressure bearing cushion block, 13-upper fulcrum roller limit groove, 14-upper fulcrum roller, 15-second force transducer, 16-second pressure bearing cushion block, 17-first rubber pad, 18-third force transducer, 19-third pressure bearing cushion block, 20-second rubber pad, 21-water inlet and outlet, 22-air inlet and outlet, 23-sealing door, 24-artificial crack, 25-LVDT displacement transducer, 26-super depth of field three-dimensional microscope, 27-microscope support, and 28-horizontal two-way sliding table.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
As shown in fig. 1 and 2, the multi-axis loading and water saturation coupling type rock three-point bending experimental device comprises a pressure chamber 1, a first actuator 2, a second actuator 3, a third actuator 4 and a sample support 5; the first actuator 2 is vertically arranged at the top of the pressure chamber 1, the sample support 5 is vertically and fixedly arranged at the bottom of the inner side of the pressure chamber 1 right below the first actuator 2, and the second actuator 3 and the third actuator 4 are horizontally and symmetrically arranged at the left side and the right side of the pressure chamber 1; a lower fulcrum roller limiting table 6 is fixedly arranged at the top end of the sample support 5, a plurality of lower fulcrum roller limiting grooves 7 are formed in the upper surface of the lower fulcrum roller limiting table 6, the lower fulcrum roller limiting grooves 7 are distributed in parallel at equal intervals, a first lower fulcrum roller 8 and a second lower fulcrum roller 9 are symmetrically arranged in the lower fulcrum roller limiting grooves 7, and a rock sample 10 is arranged on the first lower fulcrum roller 8 and the second lower fulcrum roller 9; a first force measuring sensor 11 is fixedly arranged at the end part of a piston rod of the first actuator 2, a first pressure bearing cushion block 12 is fixedly connected to the bottom end of the first force measuring sensor 11, an upper fulcrum roller limiting groove 13 is formed in the lower surface of the first pressure bearing cushion block 12, an upper fulcrum roller 14 is arranged in the upper fulcrum roller limiting groove 13, the upper fulcrum roller 14 is in abutting contact with the rock sample 10, and the upper fulcrum roller 14 is positioned right above the middle point of the first lower fulcrum roller 8 and the second lower fulcrum roller 9; a second force measuring sensor 15 is fixedly arranged at the end part of a piston rod of the second actuator 3, a second pressure-bearing cushion block 16 is fixedly connected to the side surface of the second force measuring sensor 15, a first rubber pad 17 is fixedly connected to the side surface of the second pressure-bearing cushion block 16, and the first rubber pad 17 is abutted against and contacted with the rock sample 10; a third force measuring sensor 18 is fixedly arranged at the end part of a piston rod of the third actuator 4, a third pressure-bearing cushion block 19 is fixedly connected to the side surface of the third force measuring sensor 18, a second rubber pad 20 is fixedly connected to the side surface of the third pressure-bearing cushion block 19, and the second rubber pad 20 is in abutting contact with the rock sample 10; the bottom of the pressure chamber 1 is provided with a water inlet and outlet 21, and the top of the pressure chamber 1 is provided with a water inlet and outlet 22.
Both sides all are equipped with sealing door 23 around the pressure chamber 1, all install transparent viewing window on every sealing door 23, and sealing door 23 adopts whole detachable structure.
In this embodiment, the rock sample 10 is a rectangular parallelepiped structure, the size of the rock sample 10 is 100mm × 50mm × 25mm, and the sizes of the first rubber pad 17 and the second rubber pad 20 are 25mm × 25mm × 4 mm.
A multi-axis loading and water saturation coupled rock three-point bending experimental method adopts the multi-axis loading and water saturation coupled rock three-point bending experimental device, and comprises the following steps:
the method comprises the following steps: preparing a rock sample 10, and machining an artificial crack 24 inwards at the middle position of one surface with the length multiplied by the width (100mm multiplied by 50mm) of the rock sample 10; meanwhile, an LVDT displacement sensor 25 is vertically arranged between the first pressure bearing cushion block 12 and the sample support 5; in this embodiment, the width of the artificial crack 24 is 1mm, and the depth of the artificial crack 24 is 25 mm;
step two: immersing the rock sample 10 with the artificial crack 24 in distilled water until the rock sample 10 reaches a water saturation state; in order to ensure the water saturation effect of the rock sample 10, distilled water can be placed in a closed container, and the rock sample 10 is properly pressurized in the soaking process;
step three: sending the rock sample 10 in a water saturation state into the pressure chamber 1 and placing the rock sample on the first lower fulcrum roller 8 and the second lower fulcrum roller 9, so that the artificial crack 24 faces downwards and is positioned in the middle of the first lower fulcrum roller 8 and the second lower fulcrum roller 9;
step four: the piston rods of the second actuator 3 and the third actuator 4 are driven to synchronously extend in a displacement control mode until the first rubber pad 17 and the second rubber pad 20 are abutted and contacted with the side surface of the rock sample 10 to complete centering and clamping of the rock sample 10, and then the piston rods of the second actuator 3 and the third actuator 4 are driven in a force control mode to apply horizontal clamping force to the rock sample 10; in this example, the horizontal clamping force applied was 1 kN;
step five: installing a sealing door 23 back on the pressure chamber 1 to finish the sealing of the pressure chamber 1, then connecting the water inlet and outlet 21 with a water supply source, injecting water into the pressure chamber 1, in the water injection process, discharging air in the pressure chamber 1 through the air inlet and outlet 22, when water flows out from the air inlet and outlet 22, indicating that the water in the pressure chamber 1 is filled, closing the air inlet and outlet 22 at the moment, and finally finishing the water pressure application in the pressure chamber 1 to simulate the underground saturated water pressure environment; in this embodiment, the water pressure in the pressure chamber 1 is 5 MPa;
step six: driving a piston rod of a first actuator 2 to extend downwards in a displacement control mode until an upper supporting point roller 14 is abutted and contacted with the upper surface of the rock sample 10, and enabling the piston rod of the first actuator 2 to apply downward pressure to the rock sample 10 in a force control mode; in this embodiment, the displacement control speed of the piston rod of the first actuator 2 is 10mm/min, and the force control speed of the piston rod of the first actuator 2 is 50N/mim;
step seven: observing a stress-displacement curve in a computer, continuously loading for a period of time after the stress-displacement curve reaches a peak value, stopping loading, and storing the acquired experimental data;
step eight: firstly, a piston rod of a first actuator 2 is driven to move upwards in a displacement control mode, so that an upper supporting point roller 14 is separated from the upper surface of a rock sample 10, and unloading of the lower pressure is completed; then, piston rods of the second actuator 3 and the third actuator 4 are driven to synchronously retract in a displacement control mode, so that the first rubber pad 17 and the second rubber pad 20 are separated from the side surface of the rock sample 10, and the unloading of the horizontal clamping force is completed;
step nine: firstly, the water pressure in the pressure chamber 1 is unloaded, then the closed air inlet and outlet 22 is opened, and finally the water in the pressure chamber 1 is completely discharged through the water inlet and outlet 21;
step ten: the sealing door 23 is detached from the pressure chamber 1, the rock sample 10 is taken out, and the crack expansion condition on the rock sample 10 is observed; meanwhile, the acquired data are analyzed and calculated to obtain the fracture toughness and tensile strength of the rock sample 10.
A multi-axis loading and water saturation coupled rock three-point bending experimental method adopts the multi-axis loading and water saturation coupled rock three-point bending experimental device, and when an underground water saturation pressure environment does not need to be simulated, the method comprises the following steps:
the method comprises the following steps: preparing a rock sample 10, and machining an artificial crack 24 inwards at the middle position of one surface with the length multiplied by the width (100mm multiplied by 50mm) of the rock sample 10; meanwhile, an LVDT displacement sensor 25 is vertically arranged between the first pressure bearing cushion block 12 and the sample support 5; in this embodiment, the width of the artificial crack 24 is 1mm, and the depth of the artificial crack 24 is 25 mm;
step two: immersing the rock sample 10 with the artificial crack 24 in distilled water until the rock sample 10 reaches a water saturation state; in order to ensure the water saturation effect of the rock sample 10, distilled water can be placed in a closed container, and the rock sample 10 is properly pressurized in the soaking process;
step three: sending the rock sample 10 in a water saturation state into the pressure chamber 1 and placing the rock sample on the first lower fulcrum roller 8 and the second lower fulcrum roller 9, so that the artificial crack 24 faces downwards and is positioned in the middle of the first lower fulcrum roller 8 and the second lower fulcrum roller 9;
step four: the piston rods of the second actuator 3 and the third actuator 4 are driven to synchronously extend in a displacement control mode until the first rubber pad 17 and the second rubber pad 20 are abutted and contacted with the side surface of the rock sample 10 to complete centering and clamping of the rock sample 10, and then the piston rods of the second actuator 3 and the third actuator 4 are driven in a force control mode to apply horizontal clamping force to the rock sample 10; in this example, the horizontal clamping force applied was 1 kN;
step five: a super-depth-of-field three-dimensional microscope 26 is arranged in front of the rock sample 10, the super-depth-of-field three-dimensional microscope 26 is directly and fixedly connected to the pressure chamber 1 through a microscope support 27, and a horizontal bidirectional sliding table 28 is arranged between the microscope support 27 and the super-depth-of-field three-dimensional microscope 26; moving the ultra-depth-of-field three-dimensional microscope 26 to enable the lens of the ultra-depth-of-field three-dimensional microscope 26 to be opposite to the artificial crack 24 of the rock sample 10;
step six: the piston rod of the first actuator 2 is driven to extend downwards by adopting a low-speed displacement control mode until the upper supporting point roller 14 is abutted and contacted with the upper surface of the rock sample 10, the piston rod of the first actuator 2 applies downward pressure to the rock sample 10 by adopting a displacement control mode, and the data measured by the LVDT displacement sensor 25 is recorded; meanwhile, the microscopic expansion process of the artificial crack 24 of the rock sample 10 is synchronously observed through the super-depth-of-field three-dimensional microscope 26; in this embodiment, the displacement control speed of the piston rod of the first actuator 2 is 1mm/min, and the force control speed of the piston rod of the first actuator 2 is 50N/mim;
step seven: firstly, a piston rod of a first actuator 2 is driven to move upwards in a displacement control mode, so that an upper supporting point roller 14 is separated from the upper surface of a rock sample 10, and unloading of the lower pressure is completed; then, piston rods of the second actuator 3 and the third actuator 4 are driven to synchronously retract in a displacement control mode, so that the first rubber pad 17 and the second rubber pad 20 are separated from the side surface of the rock sample 10, and the unloading of the horizontal clamping force is completed; finally the rock sample 10 is removed.
The embodiments are not intended to limit the scope of the present invention, and all equivalent implementations or modifications without departing from the scope of the present invention are intended to be included in the scope of the present invention.
Claims (4)
1. The utility model provides a multiaxis loading and full water coupling formula rock three-point bending experimental apparatus which characterized in that: the device comprises a pressure chamber, a first actuator, a second actuator, a third actuator and a sample support; the first actuator is vertically arranged at the top of the pressure chamber, the sample support is vertically and fixedly arranged at the bottom of the inner side of the pressure chamber right below the first actuator, and the second actuator and the third actuator are horizontally and symmetrically arranged at the left side and the right side of the pressure chamber; a lower fulcrum roller limiting table is fixedly arranged at the top end of the sample support, a plurality of lower fulcrum roller limiting grooves are formed in the upper surface of the lower fulcrum roller limiting table, the plurality of lower fulcrum roller limiting grooves are distributed in parallel at equal intervals, a first lower fulcrum roller and a second lower fulcrum roller are symmetrically arranged in the lower fulcrum roller limiting grooves, and a rock sample is placed on the first lower fulcrum roller and the second lower fulcrum roller; a first force transducer is fixedly arranged at the end part of a piston rod of the first actuator, a first pressure-bearing cushion block is fixedly connected to the bottom end of the first force transducer, an upper fulcrum roller limiting groove is formed in the lower surface of the first pressure-bearing cushion block, an upper fulcrum roller is arranged in the upper fulcrum roller limiting groove and is in abutting contact with a rock sample, and the upper fulcrum roller is positioned right above the middle point of the first lower fulcrum roller and the second lower fulcrum roller; a second force transducer is fixedly arranged at the end part of a piston rod of the second actuator, a second pressure-bearing cushion block is fixedly connected to the side surface of the second force transducer, a first rubber pad is fixedly connected to the side surface of the second pressure-bearing cushion block, and the first rubber pad is abutted against and contacted with a rock sample; a third force transducer is fixedly arranged at the end part of a piston rod of the third actuator, a third pressure-bearing cushion block is fixedly connected to the side surface of the third force transducer, a second rubber pad is fixedly connected to the side surface of the third pressure-bearing cushion block, and the second rubber pad is abutted and contacted with a rock sample; the bottom of the pressure chamber is provided with a water inlet and outlet, and the top of the pressure chamber is provided with a gas inlet and outlet.
2. The multi-axial loading and water saturation coupled rock three-point bending experimental device as claimed in claim 1, wherein: both sides all are equipped with sealing door around the pressure chamber, all install transparent observation window on every sealing door, and sealing door adopts whole detachable structure.
3. A multi-axis loading and water saturation coupled rock three-point bending experimental method adopts the multi-axis loading and water saturation coupled rock three-point bending experimental device of claim 1, and is characterized by comprising the following steps:
the method comprises the following steps: preparing a rock sample, and inwards processing an artificial crack at the middle position of one surface of the rock sample; meanwhile, an LVDT displacement sensor is vertically arranged between the first pressure bearing cushion block and the sample support;
step two: immersing the rock sample with the artificial crack in distilled water until the rock sample reaches a water saturation state;
step three: sending the rock sample in a water saturation state into a pressure chamber, placing the rock sample on a first lower fulcrum roller and a second lower fulcrum roller, and enabling an artificial crack to face downwards and to be located in the middle of the first lower fulcrum roller and the second lower fulcrum roller;
step four: the piston rods of the second actuator and the third actuator are driven to synchronously extend in a displacement control mode until the first rubber pad and the second rubber pad are abutted and contacted with the side surface of the rock sample, so that the rock sample is centered and clamped, and then the piston rods of the second actuator and the third actuator are driven in a force control mode to apply horizontal clamping force to the rock sample;
step five: installing a sealing door on the pressure chamber, completing the sealing of the pressure chamber, communicating a water inlet and outlet with a water supply source, injecting water into the pressure chamber, discharging air in the pressure chamber through a water inlet and outlet in the water injection process, when water flows out from the water inlet and outlet, indicating that the water in the pressure chamber is filled, closing the water inlet and outlet, and finally completing the water pressure application in the pressure chamber to simulate the underground water-saturated pressure environment;
step six: a piston rod of a first actuator is driven to extend downwards in a displacement control mode until an upper supporting point roller is abutted and contacted with the upper surface of the rock sample, and then the piston rod of the first actuator applies downward force to the rock sample in the displacement control mode;
step seven: observing a stress-displacement curve in a computer, continuously loading for a period of time after the stress-displacement curve reaches a peak value, stopping loading, and storing the acquired experimental data;
step eight: firstly, a piston rod of a first actuator is driven to move upwards in a displacement control mode, so that an upper supporting point roller is separated from the upper surface of a rock sample, and unloading of downward pressure is completed; then piston rods of the second actuator and the third actuator are driven to synchronously retract in a displacement control mode, so that the first rubber pad and the second rubber pad are separated from the side surface of the rock sample, and the unloading of the horizontal clamping force is completed;
step nine: unloading the water pressure in the pressure chamber, opening the closed air inlet and outlet, and finally discharging all the water in the pressure chamber through the water inlet and outlet;
step ten: the sealing door is detached from the pressure chamber, the rock sample is taken out, and the crack expansion condition on the rock sample is observed; meanwhile, the acquired data are analyzed and calculated, and the fracture toughness and the tensile strength of the rock sample are obtained.
4. A multi-axis loading and water saturation coupled rock three-point bending experimental method adopts the multi-axis loading and water saturation coupled rock three-point bending experimental device of claim 1, and is characterized by comprising the following steps of:
the method comprises the following steps: preparing a rock sample, and inwards processing an artificial crack at the middle position of one surface of the rock sample; meanwhile, an LVDT displacement sensor is vertically arranged between the first pressure bearing cushion block and the sample support;
step two: immersing the rock sample with the artificial crack in distilled water until the rock sample reaches a water saturation state;
step three: sending the rock sample in a water saturation state into a pressure chamber, placing the rock sample on a first lower fulcrum roller and a second lower fulcrum roller, and enabling the artificial crack to face downwards and to be located in the middle of the first lower fulcrum roller and the second lower fulcrum roller;
step four: the piston rods of the second actuator and the third actuator are driven to synchronously extend in a displacement control mode until the first rubber pad and the second rubber pad are abutted and contacted with the side surface of the rock sample, so that the rock sample is centered and clamped, and then the piston rods of the second actuator and the third actuator are driven in a force control mode to apply horizontal clamping force to the rock sample;
step five: a super-depth-of-field three-dimensional microscope is arranged in front of a rock sample, the super-depth-of-field three-dimensional microscope is directly and fixedly connected to a pressure chamber through a microscope support, and a horizontal bidirectional sliding table is arranged between the microscope support and the super-depth-of-field three-dimensional microscope; moving the super-depth-of-field three-dimensional microscope to enable a lens of the super-depth-of-field three-dimensional microscope to be opposite to the artificial crack of the rock sample;
step six: a piston rod of a first actuator is driven to extend downwards in a low-speed displacement control mode until an upper supporting point roller is abutted and contacted with the upper surface of the rock sample, then the piston rod of the first actuator applies downward pressure to the rock sample in a displacement control mode, and data measured by an LVDT displacement sensor is recorded; meanwhile, synchronously observing the microscopic expansion process of the artificial crack of the rock sample through a super-depth-of-field three-dimensional microscope;
step seven: firstly, a piston rod of a first actuator is driven to move upwards in a displacement control mode, so that an upper supporting point roller is separated from the upper surface of a rock sample, and unloading of downward pressure is completed; then piston rods of the second actuator and the third actuator are driven to synchronously retract in a displacement control mode, so that the first rubber pad and the second rubber pad are separated from the side surface of the rock sample, and the unloading of the horizontal clamping force is completed; and finally, taking down the rock sample.
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