Thermal-stress-pore pressure coupled electromagnetic loading triaxial Hopkinson bar system and test method

A thermal-stress-pore pressure coupled electromagnetic loading triaxial Hopkinson bar system, comprising:

• a support platform, a left axial pressure loading and fixing baffle, a left axial pressure loading cylinder, a left axial pressure loading piston, a left electromagnetic pulse generator, a left electromagnetic pulse generator support, connecting rods, a left stress wave loading bar, a stress wave loading bar support, resistance strain gauges, a right axial pressure loading and fixing baffle, a right axial pressure loading cylinder, a right axial pressure loading piston, a right electromagnetic pulse generator, a right electromagnetic pulse generator support, a right stress wave loading bar, a confining-pressure loading cylinder enclosure, a confining-pressure loading cylinder, a threaded rod, a confining-pressure loading cylinder oil inlet, a confining-pressure loading cylinder air outlet, a sealing plug of the confining-pressure loading cylinder air outlet, a confining pressure oil pressure gauge, a left pore pressure pipe, a right pore pressure pipe, an external power outlet of a thermal system, an intelligent thermal control thermocouple and thermal sensor, a rubber sleeve, and a test specimen;
• the system centers on the test specimen, and is arranged symmetrically;
• the left axial pressure loading and fixing baffle and the right axial pressure loading and fixing baffle are fixed at a left end and a right end of the support platform, respectively;
• a central mounting hole and peripheral mounting holes are disposed in centers of and on peripheries of the left axial pressure loading and fixing baffle and the right axial pressure loading and fixing baffle, respectively;
• the left axial pressure loading cylinder and the right axial pressure loading cylinder respectively penetrate through the central mounting hole of each of the left axial pressure loading and fixing baffle and the right axial pressure loading and fixing baffle, and are welded therewith to form an overall structure;
• in addition, the left axial pressure loading and fixing baffle and the right axial pressure loading and fixing baffle are connected into a hole by the connecting rods through the peripheral mounting holes on the peripheries thereof, and form an overall frame system together with the support platform;
• the left electromagnetic pulse generator is supported by the left electromagnetic pulse generator support, and is placed on the support platform, wherein a left end of the left electromagnetic pulse generator is freely attached to a right end of the left axial pressure loading piston, such that a static axial pressure provided by the left axial pressure loading cylinder is transferred to the left electromagnetic pulse generator by means of the left axial pressure loading piston;
• the left stress wave loading bar is supported by the stress wave loading bar support, and is placed on the support platform, wherein a left end of the left stress wave loading bar is freely attached to a right end of the left electromagnetic pulse generator;
• on one hand, the static axial pressure transferred to the left electromagnetic pulse generator is further transferred to the left stress wave loading bar, and finally applies to the test specimen;
• on the other hand, an incident stress wave generated by the left electromagnetic pulse generator is inputted into the left stress wave loading bar, and then propagates along an axial direction thereof until applying a dynamic load from left to right to the test specimen;
• the right electromagnetic pulse generator is supported by the right electromagnetic pulse generator support, and is placed on the support platform, wherein a right end of the right electromagnetic pulse generator is freely attached to a left end of the right axial pressure loading piston, such that a static axial pressure provided by the right axial pressure loading cylinder is transferred to the right electromagnetic pulse generator by means of the right axial pressure loading piston;
• the right stress wave loading bar is supported by the stress wave loading bar support, and is placed on the support platform, wherein a right end of the right stress wave loading bar is freely attached to a left end of the right electromagnetic pulse generator;
• on one hand, the static axial pressure transferred to the right electromagnetic pulse generator is further transferred to the right stress wave loading bar, and finally applies to the test specimen;
• on the other hand, an incident stress wave generated by the right electromagnetic pulse generator is inputted into the right stress wave loading bar, and then propagates along the axial direction thereof until applying a dynamic load from right to left to the test specimen;
• the resistance strain gauges are pasted on the left stress wave loading bar and the right stress wave loading bar, respectively;
• the system further comprises a confining-pressure loading apparatus which comprises the confining-pressure loading cylinder enclosure, the confining-pressure loading cylinder, the threaded rod, the confining-pressure loading cylinder oil inlet, the confining-pressure loading cylinder air outlet, the sealing plug of the confining-pressure loading cylinder air outlet, and the confining pressure oil pressure gauge, wherein central mounting hole and peripheral mounting holes are disposed in a center of and on a periphery of the confining-pressure loading cylinder enclosure respectively, which are used to extend the left stress wave loading bar and the right stress wave loading bar through the central mounting hole into an interior of the confining pressure loading cylinder to contact the test specimen;
• the threaded rods penetrate through the peripheral mounting holes of the confining-pressure loading cylinder enclosure, such that the confining-pressure loading cylinder enclosure and the confining-pressure loading cylinder are connected to form an overall structure, and are placed on the support platform;
• in addition, the confining-pressure loading cylinder oil inlet and the confining-pressure loading cylinder air outlet are disposed at an upper part and a lower part of the central mounting hole of a right enclosure of the confining-pressure loading cylinder enclosure, respectively;
• the confining-pressure loading cylinder oil inlet and the confining-pressure loading cylinder air outlet form an intercommunication loop of the confining-pressure loading apparatus;
• the intercommunication loop is used to pump hydraulic oil into the confining-pressure loading cylinder to apply a circumferential static confining pressure to the test specimen wrapped in the rubber sleeve;
• the sealing plug of the confining-pressure loading cylinder air outlet is disposed on an outer side of the confining-pressure loading cylinder air outlet;
• and the static confining pressure is displayed on the confining pressure oil pressure gauge;
• the system further comprises a thermal control apparatus;
• the thermal control apparatus comprises the external power outlet of a thermal system and the intelligent thermal control thermocouple and thermal sensor, and is used to heat the test specimen and maintain a temperature at a preset value;
• during heating, a control system controls the intelligent thermal control thermocouple and thermal sensor to raise a temperature of the hydraulic oil pumped into the confining-pressure loading cylinder at a temperature rise rate set according to test requirement, and transfers heat to the test specimen wrapped in the rubber sleeve;
• the control system controls the thermocouple, and sets a temperature rise rate and a temperature range;
• then, the intelligent thermal control thermocouple and thermal sensor feeds back a real time temperature to a display system, ensuring to heat to a preset temperature;
• after heating to the preset temperature, a rock dynamics test is conducted, achieving in-situ heating the test specimen to a specified temperature.