A true triaxial testing equipment

Abstract

The present invention discloses a true triaxial testing device, which relates to the field of mechanical testing equipment. The device comprises: a conventional triaxial testing machine, internally provided with a pressurized test bench; the pressurized test bench comprises a base, a pressure head, a confining pressure chamber, and an internal pressure chamber, the internal and confining pressure chambers being respectively connected to an oil pressure loading mechanism and both filled with hydraulic oil; lateral pressure plates are connected to opposite sides of a specimen, the lateral pressure plates being connected to the internal pressure chamber via a force transmission mechanism; the intermediate principal stress of the specimen is applied via the lateral pressure plates, the minimum principal stress of the specimen is applied via the hydraulic oil in the confining pressure chamber, and the maximum principal stress of the specimen is applied via the pressure head. This testing device replaces the true triaxial testing machine by applying loads that can be adjusted and monitored in real time to the three axes of a cubic specimen, significantly reducing the equipment requirements for true triaxial testing and enabling the generation of highly authentic test results and data.

Description

Technical Field

[0001] The present invention relates to the field of mechanical testing equipment, in particular to a true triaxial testing equipment. Background Art

[0002] With the development of deep underground engineering, the research on the mechanical properties of surrounding rock has become more demanding. The mechanical response of rock materials under true triaxial conditions needs to be studied in depth to provide a basis for studying their deformation and failure characteristics, revealing fracture mechanisms, developing mechanical theories, and guiding engineering design and construction. To study the mechanical properties of rock materials under true triaxial conditions, true triaxial equipment has been developed and manufactured. However, true triaxial equipment is not only expensive and bulky, but also has significant structural differences from existing conventional triaxial testing equipment. The supporting equipment needs to be reconfigured, making the existing equipment unable to be fully utilized. Conventional triaxial testing machines (such as MTS pressure servo testing machines) have relatively mature control systems, servo systems, and measurement systems, but they cannot complete true triaxial testing and have therefore not been widely used by major research institutions. Summary of the Invention

[0003] The present invention provides a true triaxial testing device, which is used to expand a conventional triaxial testing machine into a device with the functions of a true triaxial testing machine.

[0004] A true triaxial testing device includes a conventional triaxial testing machine with a pressurized test bench provided inside the conventional triaxial testing machine;

[0005] The pressure test bench includes a base for placing the sample, a pressure head for applying the maximum principal stress to the sample, and a confined pressure chamber for applying lateral pressure to the sample. The confined pressure chamber is provided with an internal pressure chamber, which is connected to the oil pressure loading mechanism respectively and is filled with hydraulic oil.

[0006] The two opposite sides of the specimen are connected with lateral pressure plates, which are connected to the internal pressure chamber through a force transmission mechanism. The intermediate principal stress of the specimen is applied through the lateral pressure plates; the minimum principal stress of the specimen is applied through the hydraulic oil in the confining pressure chamber.

[0007] The pressurized test bench is also connected to a data collector and a servo control mechanism, and the data collector and the servo control mechanism are connected to the control system through a data transmission line.

[0008] The beneficial effects of adopting the above technical solution are as follows: the true triaxial testing equipment of the present invention improves the pressurized test bench of the conventional triaxial testing machine on the basis of the conventional triaxial testing machine and cooperates with the existing data acquisition device, oil pressure loading mechanism, servo control mechanism and control system to simulate the true triaxial testing machine, and performs a true triaxial loading test on the sample. The maximum principal stress direction of the sample is applied by the pressure head, the minimum principal stress of the sample is applied by the hydraulic oil in the confining pressure chamber, and the intermediate principal stress of the sample is applied by the force transmission mechanism of the inner pressure chamber through the lateral pressure plate. The principal stresses in all directions can be monitored and adjusted in real time. Through this equipment, a conventional triaxial testing machine can be transformed into a device with the functions of a true triaxial testing machine, which can not only save the cost of the test equipment, but also make full use of the existing equipment.

[0009] Furthermore, the above-mentioned confined pressure chamber is a closed space formed by the confined pressure chamber side wall and the confined pressure chamber upper cover. The base is provided with a confined pressure chamber oil inlet hole that passes through the interior of the confined pressure chamber, and the confined pressure chamber upper cover is provided with a confined pressure chamber oil outlet hole and a wire outlet hole. The confined pressure chamber oil outlet hole is connected to the oil return pipe on the upper cover plate.

[0010] The beneficial effects of adopting the above technical solution are as follows: the confining pressure chamber is a closed space and is connected to the hydraulic oil delivery pipeline. Hydraulic oil is injected into the confining pressure chamber to increase pressure, and the hydraulic oil is discharged to remove the load. The hydraulic oil can evenly apply pressure to the side of the sample, avoiding uneven load on the pressure surface of the sample.

[0011] Furthermore, the side wall of the confined pressure chamber is sealedly connected to the base, an upper cover plate is provided on the outer side of the upper cover of the confined pressure chamber, and the upper cover plate, the upper cover of the confined pressure chamber and the base are connected as a whole through a pull rod.

[0012] Furthermore, the above-mentioned internal pressure chamber is a closed space formed by the internal pressure chamber wall and the internal pressure chamber side cover, and the two are sealed by a connecting screw; the internal pressure chamber wall is provided with an internal pressure chamber oil inlet hole, an internal pressure chamber oil return hole and an internal pressure chamber wire outlet hole, the internal pressure chamber oil inlet hole is connected to the internal pressure chamber oil inlet pipe, and the internal pressure chamber oil return hole is connected to the internal pressure chamber oil return pipe.

[0013] Furthermore, the above-mentioned force transmission mechanism includes a lateral force transmission shaft and a piston, one end of the lateral force transmission shaft is connected to the lateral pressure plate, and the other end is connected to the piston; a lateral force transmission shaft sleeve is arranged between the lateral force transmission shaft and the wall of the inner pressure chamber, and a piston return spring is sleeved on the lateral force transmission shaft, one end of the piston return spring is in contact with the wall surface of the piston, and the other end is in contact with the axial surface of the lateral force transmission shaft sleeve.

[0014] The beneficial effects of adopting the above technical solution are as follows: the internal pressure chamber is a closed space, hydraulic oil is injected into the internal pressure chamber, the pressurized hydraulic oil transmits the pressure to the piston, and the piston then transmits the pressure to the lateral force transmission shaft, applying lateral pressure to the sample through the lateral pressure plate.

[0015] Furthermore, a displacement transmission rod and a displacement sensor are installed inside the inner pressure chamber wall, and the displacement sensor is installed on the sensor fixing seat; one end of the displacement transmission rod is connected to the piston, and the other end is connected to the displacement sensor.

[0016] The beneficial effects of adopting the above technical solution are as follows: the displacement sensor and the displacement conduction rod can cooperate to monitor the lateral pressure applied to the sample in real time during the test, so as to obtain accurate data.

[0017] Furthermore, a sensor sealing cover is provided between the internal pressure chamber and the space for installing the displacement sensor, and a sensor wire outlet hole is provided on the sensor sealing cover.

[0018] Furthermore, a pressure head sleeve is provided between the pressure head and the upper cover of the confining pressure chamber, and a pressure head return spring is connected to the pressure head, and the other end of the pressure head return spring is connected to the inner wall of the upper cover of the confining pressure chamber.

[0019] Furthermore, the internal pressure chambers are symmetrically arranged on both sides of the specimen, and the two opposite internal pressure chamber walls are connected by a lateral force transmission rod.

[0020] Furthermore, the oil pressure loading mechanism is connected to the confining pressure chamber and the internal pressure chamber through oil inlet and outlet pipelines.

[0021] The present invention has the following beneficial effects:

[0022] (1) This test equipment is improved based on the existing conventional triaxial testing machine. It uses hydraulic loading mechanism, data acquisition device, servo control mechanism and other devices to simulate the working mode of the true triaxial testing machine. By applying loads that can be adjusted and monitored in real time to the three axes of the cubic specimen instead of the true triaxial testing machine, the equipment requirements for the true triaxial test are greatly reduced. Making full use of existing equipment not only saves the cost of test equipment, but also makes it easier for more scientific research personnel to conduct experiments.

[0023] (2) The test equipment uses hydraulic oil instead of the loading plate that is in direct contact with the specimen. When the load is removed from the specimen, it can effectively prevent the loading plate from easily transferring the stored elastic energy to the specimen, causing distortion of the specimen data or even test failure. Therefore, using this test equipment to simulate a true triaxial testing machine can obtain highly authentic test results and data.

[0024] (3) This test equipment is reliable, easy to maintain, adaptable to specimens of various sizes, easy to operate, and low in cost, which is conducive to expanding its scope of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the overall structural diagram of the test equipment of the present invention;

[0026] Figure 2This is a front view schematic diagram of the internal structure of the pressurized test bench of the present invention;

[0027] Figure 3 for Figure 2 Schematic diagram of the AA section structure;

[0028] Figure 4 It is a side view schematic diagram of the internal structure of the pressurized test bench of the present invention;

[0029] Figure 5 It is a partial enlarged view of the connection structure at the piston in the present invention.

[0030] In the figure: 1-pressure test bench; 11-pressure head; 111-pressure head return spring; 112-pressure head sleeve; 12-lateral pressure plate; 13-inner pressure chamber; 131-inner pressure chamber wall; 1311-inner pressure chamber oil inlet hole; 1312-inner pressure chamber oil return hole; 1313-displacement transmission rod; 1314-displacement sensor; 1315-sensor fixing seat; 1316-sensor outlet hole; 1317-sensor sealing cover; 132-inner pressure chamber side cover; 133-inner pressure chamber oil inlet pipe; 134-inner pressure chamber oil return pipe; 135-inner pressure chamber outlet hole; 1 36-Lateral force transmission rod; 137-Connecting screw; 14-Lateral force transmission shaft; 141-Piston; 142-Lateral force transmission shaft sleeve; 143-Piston return spring; 15-Confining pressure chamber; 151-Confining pressure chamber side wall; 152-Confining pressure chamber upper cover; 153-Confining pressure chamber oil inlet hole; 16-Upper cover plate; 161-Oil return pipe; 162-Outlet hole; 17-Base; 18-Pull rod; 2-Conventional triaxial testing machine; 3-Hydraulic loading mechanism; 31-Oil inlet and outlet pipelines; 4-Control system; 41-Data transmission line; 5-Data acquisition device; 6-Servo control mechanism; 7-Specimen. DETAILED DESCRIPTION

[0031] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0032] refer to Figure 1 and Figure 2The present invention provides a true triaxial test equipment, comprising: a conventional triaxial testing machine 2, an oil pressure loading mechanism 3, a control system 4, a data acquisition device 5, and a servo control mechanism 6; a cubic specimen 7 is placed on the pressurized test bench 1 of the conventional triaxial testing machine 2, and the specimen 7 is entirely located in a confined pressure chamber 15, wherein an internal pressure chamber 13 is provided inside the confined pressure chamber 15, and both the confined pressure chamber 15 and the internal pressure chamber 13 are sealed spaces filled with hydraulic oil, and lateral pressure is applied to the specimen 7 by pressurized hydraulic oil to simulate the intermediate principal stress and the maximum principal stress. To test the minimum principal stress, a pressure head 11 is installed on the top of specimen 7, which applies the maximum principal stress to specimen 7. A hydraulic loading mechanism 3 provides pressurized hydraulic oil to the confining pressure chamber 15 and the internal pressure chamber 13 and can record the oil pressure in real time. A common hydraulic loading mechanism 3 is the MTS815 model, which can provide a loading pressure within the range of 140 MPa. The hydraulic loading mechanism 3 is connected to inlet and outlet oil pipelines 31, which communicate with the confining pressure chamber 15 and the internal pressure chamber 13, facilitating the filling and withdrawal of hydraulic oil. The pressurized test bench 1 is equipped with components such as displacement sensors 1314. These sensors are connected to the data acquisition unit 5 and the servo control unit 6 via data transmission lines 41. The data acquisition unit 5 and the servo control unit 6 are then connected to the control system 4, providing rapid feedback of test data to the control system 4, facilitating adjustment of the loading pressure of specimen 7.

[0033] refer to Figures 2 to 4 The pressure test bench 1 includes a base 17 for placing the sample 7, an internal pressure chamber 13 symmetrically arranged on both sides of the sample 7, and a confining pressure chamber 15 on the outer side;

[0034] The confined pressure chamber 15 is filled with hydraulic oil. The two sides of the sample 7 are in direct contact with the hydraulic oil. The pressurized hydraulic oil exerts pressure on the two sides of the sample 7 to simulate the minimum principal stress. The confined pressure chamber 15 is a closed space formed by a circular confined pressure chamber side wall 151 and a confined pressure chamber cover 152. The bottom end of the confined pressure chamber side wall 151 is sealed to the base 17 through a sealing ring. The confined pressure chamber cover 152 and the confined pressure chamber side wall 151 are cast as one piece. The outer wall of the confined pressure chamber cover 152 is The upper cover plate 16 is provided. Both the upper cover plate 16 and the confining pressure chamber upper cover 152 are provided with a confining pressure chamber oil outlet and a wire outlet 162. The oil outlet on the upper cover plate 16 is connected to an oil return pipe 161, which communicates with the interior of the confining pressure chamber 15 through the oil outlet on the confining pressure chamber upper cover 152 for recovering the hydraulic oil therein. The wire outlet 162 on the upper cover plate 16 is connected to the wire outlet 162 on the confining pressure chamber upper cover 152 for laying data acquisition lines for sensors and other components. The base 17 is provided with a confining pressure chamber oil inlet 153 extending through the interior of the confining pressure chamber 15 and an internal pressure chamber oil inlet pipe 133 connected to the interior of the internal pressure chamber 13. The confining pressure chamber oil inlet 153 and the internal pressure chamber oil inlet pipe 133 are respectively connected to the oil inlet and outlet pipelines 31 on the hydraulic loading mechanism 3. The upper cover plate 16, the upper cover of the confining pressure chamber 152 and the base 17 are connected as a whole through a tie rod 18. The tie rod 18 passes through the sides of the upper cover plate 16, the upper cover of the confining pressure chamber 152 and the base 17 from top to bottom. The tie rod 18 is a threaded rod, which is easy to disassemble and convenient for multiple tests.

[0035] The two opposite sides of the specimen 7 are connected with lateral pressure plates 12, which are connected to the internal pressure chamber 13 through a force transmission mechanism. The hydraulic oil in the internal pressure chamber 13 transmits the pressure to the force transmission mechanism and then acts on the lateral pressure plates 12. The lateral pressure plates 12 apply intermediate principal stress to the specimen 7.

[0036] The internal pressure chamber 13 is a closed space formed by the internal pressure chamber wall 131 and the internal pressure chamber side cover 132, and the two are sealed together by a connecting screw 137; the cross-section of the internal pressure chamber wall 131 is a U-shaped structure, on which are provided an internal pressure chamber oil inlet hole 1311, an internal pressure chamber oil return hole 1312 and an internal pressure chamber line outlet hole 135; the internal pressure chamber oil inlet hole 1311 is connected to the internal pressure chamber oil inlet pipe 133, and the internal pressure chamber oil return hole 1312 is connected to the internal pressure chamber oil return pipe 134.

[0037] The force transmission mechanism includes a lateral force transmission shaft 14 and a piston 141. One end of the lateral force transmission shaft 14 is connected to the lateral pressure plate 12, and the other end is connected to the piston 141; a lateral force transmission shaft sleeve 142 is arranged between the lateral force transmission shaft 14 and the inner pressure chamber wall 131, and a piston return spring 143 is sleeved on the lateral force transmission shaft 14, one end of the piston return spring 143 abuts against the wall surface of the piston 141, and the other end abuts against the axial surface of the lateral force transmission shaft sleeve 142. When the pressurized hydraulic oil inside the inner pressure chamber 13 transmits the pressure to the lateral pressure plate 12 through the piston 141 and the lateral force transmission shaft 14, the piston 141 will move toward the side of the sample 7. After the pressure is unloaded, the piston 141 returns to its initial position under the elastic force of the piston return spring 143, which is convenient for the next loading. Moreover, during the loading process, the piston return spring 143 will not affect the pressure loaded on the sample 7.

[0038] refer to Figure 5 , a sealed space is provided in the inner pressure chamber wall 131 near the piston 141, and the sealed space is used to install a displacement transmission rod 1313 and a displacement sensor 1314. The displacement sensor 1314 is installed on a sensor fixing seat 1315 in the sealed space, and one end of the displacement transmission rod 1313 is connected to the piston 141, and the other end is connected to the displacement sensor 1314, which is used to detect the displacement of the piston 141 under the pressure of the hydraulic oil, so as to facilitate the calculation of the magnitude of the intermediate principal stress applied to the sample 7; a sensor sealing cover 1317 is provided between the inner pressure chamber 13 and the space for installing the displacement sensor 1314, and a sealing ring is padded between the sensor sealing cover 1317 and the inner pressure chamber wall 131 for sealing connection, and a sensor wire outlet hole 1316 is provided on the sensor sealing cover 1317 for laying the data transmission line of the sensor, and the sensor wire outlet hole 1316 is also sealed and connected to the data transmission line to prevent hydraulic oil from entering the displacement sensor 1314.

[0039] The internal pressure chamber 13 includes two symmetrically arranged on both sides of the sample 7. The two opposite internal pressure chamber walls 131 are connected as a whole through a lateral force transmission rod 136 to balance the reaction force of the sample 7 on the internal pressure chamber 13.

[0040] The pressure head 11 is arranged on the upper surface of the sample 7. The bottom area of ​​the pressure head 11 is larger than the upper surface of the sample 7. A pressure head sleeve 112 is provided between the pressure head 11 and the upper cover 152 of the confining pressure chamber to ensure that the pressure head 11 is loaded on the vertical axis each time, and a pressure head reset spring 111 is connected to the pressure head 11. The other end of the pressure head reset spring 111 is connected to the inner wall of the upper cover 152 of the confining pressure chamber. When the loading of the pressure head 11 is completed, it can be reset by the pressure head reset spring 111 to carry out the next loading test; the pressure head sleeve 112 is fixed on the upper cover 16, and an O-ring is provided between the pressure head 11 and the upper cover 16.

[0041] The oil pressure inside the confining pressure chamber 15 and the internal pressure chamber 13 can be measured by the pressure sensor on the oil pressure loading mechanism 3, and the pressure on the lateral pressure plate 12 can be calculated based on the oil pressure in the internal pressure chamber 13 and the displacement size of the piston 141; based on the real-time collected data, three-dimensional loads can be conveniently applied and the confining pressure of the sample 7 can be adjusted in real time.

[0042] The above description is merely a preferred embodiment of the present invention and does not represent all possible forms of the present invention. The scope of protection of the present invention is not limited to such specific descriptions and embodiments. Based on the technical teachings disclosed by the present invention, various other modifications and improvements that do not depart from the essence of the present invention may be made, such as increasing or decreasing the number of pressure chambers, changing the pressure chamber form, applying tensile stress to the specimen, and changing the power source of the pressure chamber (using a motor, electromagnetic loading, etc.). Such modifications and improvements remain within the scope of protection of the present invention.

Claims

1. A true triaxial testing device, comprising a conventional triaxial testing machine (2), characterized in that: The conventional triaxial testing machine (2) is provided with a pressurized test bench (1) therein; The pressurized test bench (1) comprises a base (17) for placing a specimen (7), a pressure head (11) for applying a maximum principal stress to the specimen (7), and a confining pressure chamber (15) for applying a minimum principal stress to the specimen (7), wherein an internal pressure chamber (13) is provided inside the confining pressure chamber (15), and the internal pressure chamber (13) and the confining pressure chamber (15) are respectively connected to the oil pressure loading mechanism (3), and the internal pressure chamber (13) and the confining pressure chamber (15) are both filled with hydraulic oil; Two opposite sides of the sample (7) are connected with lateral pressure plates (12), and the lateral pressure plates (12) are connected to the internal pressure chamber (13) through a force transmission mechanism. The intermediate principal stress of the sample (7) is applied through the lateral pressure plates (12); the minimum principal stress of the sample (7) is applied through the hydraulic oil in the confining pressure chamber (15); The pressurized test bench (1) is also connected to a data collector (5) and a servo control mechanism (6), and the data collector (5) and the servo control mechanism (6) are connected to the control system (4) via a data transmission line (41); The confined pressure chamber (15) is formed into a closed space by a confined pressure chamber side wall (151) and a confined pressure chamber upper cover (152); the base (17) is provided with a confined pressure chamber oil inlet (153) penetrating into the confined pressure chamber (15); the confined pressure chamber upper cover (152) is provided with a confined pressure chamber oil outlet and a line outlet (162); the confined pressure chamber oil outlet is communicated with an oil return pipe (161) on the upper cover (16); The inner pressure chamber (13) is formed into a closed space by an inner pressure chamber wall (131) and an inner pressure chamber side cover (132), and the two are sealed and connected by a connecting screw (137); the inner pressure chamber wall (131) is provided with an inner pressure chamber oil inlet hole (1311), an inner pressure chamber oil return hole (1312) and an inner pressure chamber outlet hole (135); the inner pressure chamber oil inlet hole (1311) is connected to an inner pressure chamber oil inlet pipe (133), and the inner pressure chamber oil return hole (1312) is connected to an inner pressure chamber oil return pipe (134); The force transmission mechanism includes a lateral force transmission shaft (14) and a piston (141), one end of the lateral force transmission shaft (14) is connected to the lateral pressure plate (12), and the other end is connected to the piston (141); a lateral force transmission shaft sleeve (142) is provided between the lateral force transmission shaft (14) and the inner pressure chamber wall (131), and a piston return spring (143) is sleeved on the lateral force transmission shaft (14), one end of the piston return spring (143) is in contact with the wall surface of the piston (141), and the other end is in contact with the axial surface of the lateral force transmission shaft sleeve (142).

2. The true triaxial testing equipment according to claim 1, characterized in that: The side wall (151) of the confining pressure chamber is sealedly connected to the base (17); an upper cover plate (16) is provided on the outer side of the confining pressure chamber upper cover (152); and the upper cover plate (16), the confining pressure chamber upper cover (152) and the base (17) are connected as a whole via a pull rod (18).

3. The true triaxial testing equipment according to claim 1, characterized in that: A displacement transmission rod (1313) and a displacement sensor (1314) are installed inside the inner pressure chamber wall (131), and the displacement sensor (1314) is installed on a sensor fixing seat (1315); one end of the displacement transmission rod (1313) is connected to the piston (141), and the other end is connected to the displacement sensor (1314).

4. The true triaxial testing device according to claim 3, characterized in that: A sensor sealing cover (1317) is provided between the internal pressure chamber (13) and the space where the displacement sensor (1314) is installed, and a sensor wire outlet hole (1316) is provided on the sensor sealing cover (1317).

5. The true triaxial testing equipment according to claim 1, characterized in that: A pressure head sleeve (112) is provided between the pressure head (11) and the upper cover (152) of the confining pressure chamber, and a pressure head return spring (111) is connected to the pressure head (11), and the other end of the pressure head return spring (111) is connected to the inner wall of the upper cover (152) of the confining pressure chamber.

6. The true triaxial testing device according to claim 1, characterized in that: The internal pressure chambers (13) are symmetrically arranged on both sides of the specimen (7), and the two opposite internal pressure chambers (13) are connected via a lateral force transmission rod (136).

7. The true triaxial testing device according to any one of claims 1 to 6, characterized in that: The oil pressure loading mechanism (3) is in communication with the confining pressure chamber (15) and the internal pressure chamber (13) via oil inlet and outlet pipelines (31).

Images