| CPC G01N 15/0826 (2013.01) [G01B 7/24 (2013.01); G01N 15/0806 (2013.01); G01N 2015/0015 (2013.01)] | 1 Claim |
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1. A test system for measuring gas permeation parameters of an ultra-low permeability medium in multi-field and multi-phase coupling conditions, which comprises a triaxial permeation chamber, a deformation monitoring apparatus, a temperature sensing control apparatus, a volume/pressure controller, a bias stress loading apparatus, a gas injection apparatus, an outlet buffer container, and an ultra-low permeation flow monitoring apparatus;
a test process of the test system comprises: first applying temperature and triaxial stress control to a rock-soil mass sample; then using the gas injection apparatus to inject high-pressure gas into the rock-soil mass sample; the high-pressure gas permeates the rock-soil mass sample and enters the outlet buffer container and the ultra-low permeation flow monitoring apparatus to acquire the gas permeation flow; in the test process, the deformation monitoring apparatus measures the local absolute deformation of the rock-soil mass sample; full-process monitoring of the gas permeation of an ultra-low permeability medium in multi-field and multi-phase coupling conditions is thereby implemented, enabling acquisition of gas permeation features and macroscopic deformation features;
the triaxial permeation chamber is the main part of the test system, it comprises a housing and an inner cavity; the housing of the triaxial permeation chamber comprises base, top cover, and side ring, all are made of stainless steel; the base and the side ring are connected tightly by several bolts in horizontal; the joints between the base and the side ring, the top cover and the side ring are sealed with several O-rings; the base is provided with an air inlet, an air outlet, and a water supply hole; the top cover is provided with an exhaust hole, a thermal probe hole, and a bearing shaft hole; the inner cavity of the triaxial permeation chamber is provided with several triaxial chamber pillars, rock-soil mass sample, upper metal cylinders and lower metal cylinders; the inner cavity of the triaxial permeation chamber could be filled with liquid;
the triaxial chamber pillars are vertically connected between the base and the top cover, and are equidistant along the circumference of the base to support and fix the base and the top cover;
the rock-soil mass sample is the tested material and is installed between the upper metal cylinder and the lower metal cylinder; the cross-sectional dimensions of the upper metal cylinder and the lower metal cylinder are the same as the rock-soil mass sample; in test, high-strength emulsion film is used to wrap the upper metal cylinder, the lower metal cylinder, and the rock-soil mass sample to make the three closely contact without separation; the upper metal cylinder and the lower metal cylinder are provided with air vents; the bottom end of the air vent of the upper metal cylinder and the top end of the lower metal cylinder connects with the rock-soil mass sample directly;
the top end of the air vent of the upper metal cylinder connects the top end of the air outlet of the base by conduit; the bottom end of the air vent of the lower metal cylinders connects the top end of the air inlet of the base;
the deformation monitoring apparatus is installed in the inner cavity of the triaxial permeation chamber, and comprises several eddy current sensors, deformation monitoring frames, and metal pads; the eddy current sensors are fixed on the deformation monitoring frames, and are equidistant spaced around the rock-soil mass sample along the height and circumference of the rock-soil mass sample; the deformation monitoring frames are equidistant spaced along the circumference of the rock-soil mass sample; the metal pads are adhered to the outer surface of the high-strength emulsion film which wraps the rock-soil mass sample, and are equidistant spaced along the height and circumference of the rock-soil mass sample; each of the metal pads is directly opposite to the probe of a respective eddy current sensor and keeps a certain distance; the eddy current sensor accurately measures static and dynamic relative displacement between the metal pad and the probe, and calculates a local absolute deformation of the rock-soil mass sample in permeation process from the real time relative displacement;
the temperature sensing control apparatus is installed outside the housing of the triaxial permeation chamber, it comprises a heater, a temperature controller, a thermal probe; the heater is wrapped outside the side ring of the triaxial permeation chamber. By heating the side ring made of stainless steel, the heat is transmitted to the liquid filled in the inner cavity of the triaxial permeation chamber; the temperature controller connects with the heater through wire, it could automatic control the on-off of the heater power supply according to the temperature setting value and the measured temperature of the liquid filled in the inner cavity of the triaxial permeation chamber; a thermal probe extends its probe into the liquid filled in the inner cavity of the triaxial permeation chamber through the thermal probe hole to measure the temperature of the liquid; then the real-time measured temperature data is transmitted to the temperature controller through the wire; the heater, the temperature controller, and the thermal probe together form a closed-loop control device, it can accurately control the temperature of the tested rock-soil mass sample during the permeability test;
the volume/pressure controller is connected to the water supply hole of the triaxial permeation chamber through a conduit; for an assembled triaxial permeation chamber, when the vent is open, the volume/pressure controller could inject or discharge liquid into the inner cavity of the triaxial permeation chamber, when the vent is closed, pressure can be applied to the liquid in the triaxial permeation chamber to exert confining pressure on the rock-soil mass sample;
the bias stress loading apparatus comprises beam, weighing sensor, bearing shaft, bearing, operating platform, load speed controller, vertical shaft, and columns; two columns are vertically fixed on the operating platform for fixing and supporting; the beam is fixed on the column; the vertical shaft is fixed in the middle of the beam; the weighing sensor is fixed at the bottom end of the vertical shaft to measure the axial load; the bearing shaft passes through the bearing shaft hole of the top cover of the triaxial permeation chamber; the top of the bearing shaft connects to the weighing sensor, the bottom end of it is connected to the top of the upper metal cylinder, and it is used to transfer axial load from bottom to top;
the bearing is arranged on the inner wall of the bearing shaft hole of the top cover and is in contact with the side wall of the bearing shaft; the triaxial permeation chamber can rise or fall under the condition that the absolute position of the bearing shaft is fixed;
the main part of the load speed controller is installed inside the operating platform, and the top extends out of the operating platform and contacts with the base of the triaxial permeation chamber to lift or lower the triaxial permeation chamber; because the absolute position of the bearing shaft in top is fixed, raising or lowering the triaxial permeation chamber can realize apply or remove axial compression load on the rock-soil mass sample;
the gas injection apparatus comprises infinite volume controller, booster pump, gas buffer vessel, and pneumatic hydraulic convertor; the infinite volume controller is connected to the hydraulic end of the pneumatic hydraulic convertor through a conduit; the liquid in the infinite volume controller could be input to the hydraulic end of the pneumatic hydraulic convertor in the form of constant volume, pressure and rate;
the booster pump uses compressed air as the power source, which can pressurize helium and send it to the gas buffer vessel through a conduit;
one end of the gas buffer vessel is connected to the booster pump through the conduit, and the other end is connected to pneumatic end of the pneumatic hydraulic convertor through a conduit; the gas buffer vessel buffers the high-pressure gas sent by the booster pump and then sent to the pneumatic end of the pneumatic hydraulic convertor;
the pneumatic hydraulic convertor is made of high-strength stainless steel; the hydraulic end of the pneumatic hydraulic convertor is connected to the infinite volume controller through a conduit, and the pneumatic end is connected to the gas buffer vessel through a conduit; a piston is used internally to isolate the pneumatic end from the hydraulic end;
hydraulic pressure is input into the pneumatic hydraulic convertor through the infinite volume controller; the hydraulic pressure is converted into pneumatic pressure with constant volume, pressure, and rate through the piston in the pneumatic hydraulic convertor, and then the high-pressure gas in the pneumatic pressure end of the pneumatic hydraulic convertor is input into the air inlet of the triaxial permeation chamber through the conduit, so that the high-pressure gas is injected into the rock-soil mass sample;
the ultra-low permeation flow monitoring apparatus comprises four gas flow meters, single-chip microcomputer, four relays and four electromagnetic valves;
the gas from the outlet of the outlet buffer container flows into four branch conduits; the four gas flow meters are installed on four branch conduits respectively to measure the gas flow of the conduit; the four gas flow meters have different ranges;
the gas flow meters connect to the single-chip microcomputer with wires, and the digital flow signal is output to the single-chip microcomputer; the four electromagnetic valves are respectively installed on the four branch conduits to control the on-off of gas on the branch conduit;
the four relays connect to the four electromagnetic valves respectively with wire; the relays connect to the single-chip microcomputer; the single-chip microcomputer controls the on-off of the four relays respectively, so as to control the on-off of the four electromagnetic valves;
the single chip microcomputer reads the measured flow data of the four gas flow meters, automatically select the branch conduit of the optimal range flow meter according to the real-time measured flow data, and control the on-off of the four relays to control the on-off of the four electromagnetic valves automatically, so that the gas flow in the branch conduit of the optimal range flow meter is on while the gas flow in other branch conduits is off;
the gas flowmeter, single-chip microcomputer, four relays and four electromagnetic valves work together to realize the automatic switching of each branch conduit and continuously and automatically monitor the gas flow of the air outlet of the triaxial permeation chamber;
the bias stress loading apparatus pushes the base upward through the load speed controller to apply axial load; the loading mode could be stress control and displacement control; it could continuously load and unload;
one end of the outlet buffer container is connected to the air outlet of the triaxial permeation chamber through a conduit, and the other end is connected to the ultra-low permeation flow monitoring apparatus through a conduit; the gas from the air outlet of the triaxial permeation chamber is buffered in the outlet buffer container, and the flow of it is measured by the ultra-low permeation flow monitoring apparatus;
the bottom of the outlet buffer container is also provided with a safety valve and an exhaust valve, which can automatically relieve the pressure when the pressure in the outlet buffer container exceeds the upper limit pressure of the safety valve to ensure safety; the exhaust valve is used to manually discharge the gas in the outlet buffer container after the test.
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