CN107101896B - Gravel medium mesoscopic structure evolution experimental device and method under osmotic pressure sudden change - Google Patents
Gravel medium mesoscopic structure evolution experimental device and method under osmotic pressure sudden change Download PDFInfo
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- CN107101896B CN107101896B CN201710428282.9A CN201710428282A CN107101896B CN 107101896 B CN107101896 B CN 107101896B CN 201710428282 A CN201710428282 A CN 201710428282A CN 107101896 B CN107101896 B CN 107101896B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
- G01N3/12—Pressure testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
- G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/003—Generation of the force
- G01N2203/0042—Pneumatic or hydraulic means
- G01N2203/0048—Hydraulic means
Abstract
The invention discloses a gravel medium microscopical structure evolution experimental device and a method under osmotic pressure sudden change, which comprises a bearing device, an osmotic pressure sudden change device, a single-shaft loading system and a measurement and control system, wherein the bearing device comprises a base, a right upright post, a left upright post and a top beam, the left upright post and the right upright post are fixed on the base, and the top beam is sleeved on the left upright post and the right upright post through connecting holes and is fixed through a first nut and a second nut; bear and be equipped with first biography briquetting and second in the device and pass the briquetting, be equipped with the inlet opening on the first biography briquetting, the lower extreme of inlet opening is equipped with first dish and the first dynamic water pressure sensor of permeating water, is equipped with the apopore on the second biography briquetting, and the upper end of apopore is equipped with the second and permeates water dish and the second dynamic water pressure sensor. The condition of osmotic pressure sudden change can be realized in the laboratory, the change condition of the microscopic structure of the gravel medium under the condition can be observed, the evolution rule of the microscopic structure of the gravel medium and the pore pressure change rule under the osmotic pressure sudden change are finally obtained, and theoretical support is provided for the subsequent engineering practice.
Description
Technical Field
The invention relates to a rock mesoscopic structure evolution experimental device and method, in particular to a gravel medium mesoscopic structure evolution experimental device and method under osmotic pressure mutation.
Background
Gravel layers are ubiquitous in coal-based strata in western mining areas (such as Shaanxi, ningxia, inner Mongolia, xinjiang, etc.) in China. The overall strength and stability of the gravel layer roadway under the water-force coupling effect are low due to the adverse effects of various factors such as poor diagenetic effect of the gravel layer, low cementation degree, large particle difference, strong water-rich property and the like. The disturbance influence of frequent and unscheduled mine excavation engineering activities on a surrounding rock seepage field is very obvious, so that the pressure and the state of the flow field are suddenly changed, and a geotechnical medium microscopic structure is changed and damaged, so that sudden nonlinear large-deformation disasters such as roof collapse, collapse and the like are frequently generated during the excavation and service of a gravel layer roadway, and great threats are caused to mine construction and safety production. Therefore, the microscopic structure evolution process of the surrounding rock of the water-rich gravel layer roadway under the conditions of osmotic pressure mutation and hydraulic coupling becomes the key point for researching the damage instability mechanism of the surrounding rock.
One of the intuitive and effective ways to study the evolution process of the microscopic structure of the gravel medium under the osmotic pressure mutation is an indoor experiment, but the related experimental instruments and equipment at present have various defects, so that the experimental study cannot be successfully carried out. The main performance is as follows: firstly, the osmotic pressure that experimental apparatus applyed is generally for invariable flood peak, variable head or inject into and decide water pressure, and can't realize in the controllable improvement in the twinkling of an eye of normal seepage flow experimentation intermediate pressure, can't simulate the pressure condition of flow field change. And secondly, the evolution process of the mesoscopic structure under the hydraulic coupling effect of the gravel medium cannot be visually observed in real time by adopting the traditional pressure chamber structure and monitoring means. And thirdly, the monitoring effect of the short-time change of the water pressure at the two ends of the gravel sample is not ideal, the sensitivity of a sensing device is low, and the short-time continuous capturing capacity of the pressure value is insufficient. Therefore, the existing instrument and equipment have technical problems in the aspects of osmotic pressure sudden change loading, microscopic structure real-time observation and the like, and therefore experimental research on the evolution process of the microscopic structure of the gravel medium under the osmotic pressure sudden change is seriously influenced.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a gravel medium mesoscopic structure evolution experimental device and method under the osmotic pressure mutation, which can realize the condition of the osmotic pressure mutation in a laboratory, observe the change condition of the gravel medium mesoscopic structure under the condition, finally obtain the evolution rule and the pore pressure change rule of the gravel medium mesoscopic structure under the osmotic pressure mutation and provide theoretical support for subsequent engineering practice.
In order to achieve the purpose, the invention adopts the technical scheme that: a gravel medium microscopic structure evolution experimental device under osmotic pressure sudden change comprises a bearing device, an osmotic pressure sudden change device, a single-shaft loading system and a measurement and control system, wherein the bearing device comprises a base, a right upright post, a left upright post and a top beam, the left upright post and the right upright post are fixed on the base, and the top beam is sleeved on the left upright post and the right upright post through connecting holes and is respectively fixed through a first nut and a second nut;
a first pressure transmission block and a second pressure transmission block are arranged in the bearing device, a water inlet is formed in the first pressure transmission block, a first permeable disc and a first dynamic water pressure sensor are arranged at the lower end of the water inlet, a water outlet is formed in the second pressure transmission block, a second permeable disc and a second dynamic water pressure sensor are arranged at the upper end of the water outlet, the lower end of the water outlet is connected with a water pool through a pipeline, and a second valve and a flowmeter are arranged on the pipeline between the water outlet and the water pool;
the osmotic pressure mutation device comprises a cross rod, a left supporting leg, a right supporting leg, a releaser, a guide shaft, a cylinder barrel and an impact block, wherein the lower ends of the left supporting leg and the right supporting leg are fixed on the cylinder barrel, the upper ends of the left supporting leg and the right supporting leg are respectively provided with a U-shaped fork structure, the side part of the cylinder barrel is provided with a water supply port and an overflow port, the position of the water supply port is higher than that of the overflow port, the bottom of the cylinder barrel is communicated with one end of a water accumulator, the other end of the water accumulator is communicated with a water inlet hole of a first transmission block through a pipeline, a first valve is arranged on the pipeline between the water accumulator and the water inlet hole, the cross rod is fixed at the upper end of the guide shaft, the impact block is slidably sleeved on the guide shaft, the lower end of the guide shaft is provided with a stop head, the length of the cross rod is larger than the linear distance between the left supporting leg and the right supporting leg, the releaser comprises a positioning screw, a movable body, a rotating seat, a rotating arm and a rotating shaft, the movable body is sleeved on the right supporting leg and is fixed through the positioning screw, the rotating seat is fixed at one side of the rotating seat, the rotating shaft is fixed at one side of the bifurcated structure, the rotating seat is arranged on the rotating seat, the rotating shaft is arranged in the bifurcated structure;
the single-shaft loading system comprises an oil source, a loading cylinder, an energy accumulator, a first reversing valve, a second reversing valve, a pressure gauge and a magnetic displacement sensor, wherein the loading cylinder is embedded in the base, the magnetic displacement sensor is arranged on the loading cylinder, an oil inlet and an oil outlet of the loading cylinder are divided into two oil paths to be connected with the oil source, the energy accumulator is connected to one of the oil paths between the loading cylinder and the oil source, the pressure gauge and the second reversing valve are both arranged on the same oil path as the energy accumulator, and the first reversing valve is arranged on the other oil path;
the measurement and control system comprises a control device, a lifting platform, a high-speed camera and a microscopic observation device, wherein the high-speed camera and the microscopic observation device are arranged on the lifting platform, and the control device is connected with the high-speed camera, a magnetic displacement sensor, a pressure gauge, a first dynamic water pressure sensor, a second dynamic water pressure sensor and an oil source.
And the device further comprises a protective door, wherein the protective door is arranged on the side part of the bearing device, and a transparent observation window is arranged on the protective door.
Further, still include trigger device, trigger device is by trigger knob, reset shaft and spring, and the reset shaft cover has the spring and supports in the roating seat, the one end of reset shaft stretches out the roating seat and supports the swinging boom, is equipped with spacing tooth on the reset shaft, is equipped with the spacing groove that corresponds with spacing tooth in the roating seat, and the tip at the reset shaft is fixed to the trigger knob.
Further, the control device is a microcomputer.
Furthermore, scales are arranged on the guide shaft.
An experimental method of a gravel medium mesoscopic structure evolution experimental device under osmotic pressure mutation comprises the following specific steps:
A. fastening the prepared gravel sample by using a lantern ring, then installing a second water permeable disc and a second dynamic water pressure sensor at the lower end of the gravel sample, sealing the gravel sample with the upper end of a second pressure transmission block by using a high-elastic sealing ring, installing a first water permeable disc and a first dynamic water pressure sensor at the upper end of the gravel sample, and sealing the gravel sample with the lower end of a first pressure transmission block by using the high-elastic sealing ring to form a test assembly;
B. contacting the lower end of the test assembly with the upper end of the loading cylinder, contacting the upper end of the test assembly with the top beam, and limiting the top beam through a first nut and a second nut;
C. after the osmotic pressure mutation device, the single-shaft loading system and the measurement and control system are connected, the whole device connection process is completed;
D. opening the first valve and the second valve to supply water into the cylinder barrel through the water supply port until the water level in the cylinder barrel reaches the position of the overflow port, observing whether water leaks from each joint on the whole pipeline, if so, carrying out secondary sealing on the corresponding position, if not, finishing the detection of the sealing performance of the whole water supply pipeline, and closing the first valve and the second valve;
E. enabling the single-shaft loading system to start working, enabling the loading cylinder to apply pressure to the gravel sample through the second pressure transmission block, controlling the loading rate of the pressure and the set maximum pressure value through the magnetic displacement sensor and the pressure meter by the control device in the pressure applying process, and maintaining the pressure after the pressure reaches the set maximum pressure value; performing a constant head penetration test, opening the first valve and the second valve, allowing water in the cylinder barrel to flow into the gravel sample from a water inlet of the first pressure transmission block through a pipeline in a constant water flow manner, allowing the gravel sample to flow out of a water outlet of the second pressure transmission block and enter a water pool through a flowmeter, and obtaining penetration parameters of the gravel medium under the axial pressure according to a penetration law after the flowmeter is stabilized;
F. after water flow is stably permeated, the impact block is arranged at the end part of the rotating arm, the rotating arm is driven by the rotating shaft to rotate downwards by opening the trigger device, at the moment, the impact block falls to the cylinder barrel along the guide shaft to impact the water in the cylinder barrel, so that the osmotic water pressure is instantly changed from low pressure to high pressure, the change condition of the water pressure value in the water permeable disc is detected in real time by the first dynamic water pressure sensor and the second dynamic water pressure sensor and is transmitted to the control device, and meanwhile, the high-speed camera records the change image of the gravel sample in real time by the microscopic observation device and transmits the change image to the control device;
G. after the experiment is finished, closing the water supply port and the first valve, closing the second valve when no water flows into the water pool, unloading the gravel sample through the measurement and control system and the single-shaft loading system, finally opening the protective door to take out the gravel sample, and closing the oil source and the measurement and control system;
H. analyzing and drawing a curve graph through the acquired microscopic structure image of the gravel sample, the water pressure data and the loaded pressure value of the sample, and finally obtaining the evolution rule of the microscopic structure of the gravel medium and the pore pressure change rule under the osmotic pressure mutation.
Compared with the prior art, the invention adopts a mode of combining the bearing device, the osmotic pressure mutation device, the single-shaft loading system and the measurement and control system, carries out single-shaft pressure loading on the gravel sample through the single-shaft loading system, then can carry out the osmotic experiment of the constant head, and further enables the water pressure to instantaneously mutate through the osmotic pressure mutation device, thereby realizing the condition of the osmotic pressure mutation in a laboratory, observing the change condition of the mesoscopic structure of the gravel medium through the measurement and control system under the condition, finally obtaining the evolution rule of the mesoscopic structure of the gravel medium and the pore pressure change rule under the osmotic pressure mutation, and providing theoretical support for the subsequent engineering practice.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic view of a gravel sample installation of the present invention;
FIG. 3 is a front view of the osmotically abrupt change device of the present invention;
FIG. 4 is a right side view of FIG. 3;
FIG. 5 isbase:Sub>A cross-sectional view A-A of FIG. 3;
FIG. 6 is a front view of the rotary base and the trigger device of the present invention;
FIG. 7 is a left side sectional view of FIG. 6;
in the figure: 1. a carrying device; 11. a base; 12. a right upright post; 13. a left upright post; 14. a top beam; 15. a first nut; 16. a second nut; 17. a protective door; 18. a transparent viewing window; 2. a osmotically abrupt change device; 21. a cross bar; 22. a left leg; 23. a right leg; 24. a releaser; 25. a guide shaft; 26. a cylinder barrel; 27. a water supply port; 28. an overflow port; 29. an impact block; 3. a single axis loading system; 31. a source of oil; 32. a loading cylinder; 33. an accumulator; 34. a first direction changing valve; 35. a second directional control valve; 36. a pressure gauge; 37. a magnetic displacement sensor; 41. a first transfer block; 42. a water inlet hole; 43. a first water permeable disc; 44. a first dynamic water pressure sensor; 45. a high-elastic sealing ring; 46. a collar; 47. a gravel sample; 48. a second water permeable disc; 49. a second dynamic water pressure sensor; 50. a second pressure transfer block; 51. a water outlet hole; 52. a water reservoir; 53. a first valve; 54. a second valve; 55. a flow meter; 56. a water pool; 6. a measurement and control system; 61. a control device; 62. a lifting platform; 63. a high-speed camera; 64. a microscopic observation device; 241. positioning a screw rod; 242. a movable body; 243. a rotating base; 244. a rotating arm; 245. a rotating shaft; 246. a trigger device; 246-1, a trigger knob; 246-2, a reset shaft; 246-3, a spring; 246-4, limit teeth; 251. calibration; 252. and (5) stopping the head.
Detailed Description
The present invention will be further described below.
As shown in the figure, the experimental device for evolution of the microscopic structure of the gravel medium under the condition of the sudden change of the osmotic pressure comprises a bearing device 1, a sudden change of the osmotic pressure device 2, a single-shaft loading system 3 and a measurement and control system 6, wherein the bearing device 1 comprises a base 11, a right upright post 12, a left upright post 13 and a top beam 14, the left upright post 13 and the right upright post 12 are both fixed on the base 11, and the top beam 14 is sleeved on the left upright post 13 and the right upright post 12 through connecting holes and is respectively fixed through a first nut 15 and a second nut 16;
a first pressure transmission block 41 and a second pressure transmission block 50 are arranged in the bearing device 1, a water inlet 42 is arranged on the first pressure transmission block 41, a first permeable disc 43 and a first dynamic water pressure sensor 44 are arranged at the lower end of the water inlet 42, a water outlet 51 is arranged on the second pressure transmission block 50, a second permeable disc 48 and a second dynamic water pressure sensor 49 are arranged at the upper end of the water outlet 51, the lower end of the water outlet 51 is connected with a water pool 56 through a pipeline, and a second valve 54 and a flowmeter 55 are arranged on the pipeline between the water outlet 51 and the water pool 56;
the osmotic pressure mutation device 2 comprises a cross rod 21, a left leg 22, a right leg 23, a releaser 24, a guide shaft 25, a cylinder barrel 26 and an impact block 29, wherein the lower ends of the left leg 22 and the right leg 23 are fixed on the cylinder barrel 26, the upper ends of the left leg 22 and the right leg 23 are respectively provided with a U-shaped fork structure, the side part of the cylinder barrel 26 is provided with a water supply port 27 and an overflow port 28, the water supply port 27 is higher than the overflow port 28, the bottom of the cylinder barrel 26 is communicated with one end of a water reservoir 52, the other end of the water reservoir 52 is communicated with a water inlet 42 of a first transmission block 41 through a pipeline, a first valve 53 is arranged on the pipeline between the water reservoir 52 and the water inlet 42, the cross rod 21 is fixed on the upper end of the guide shaft 25, the impact block 29 is slidingly sleeved on the guide shaft 25, the lower end of the guide shaft 25 is provided with a stop head 252, the length of the cross rod 21 is greater than the linear distance between the left leg 22 and the right leg 23, the releaser 24 comprises a positioning screw rod 241, a movable body 242, a rotating arm 243, a rotating arm base 243, a rotating arm 244 and a rotating shaft 244, the other end of the rotating body is sleeved on the right leg 23, the movable body is fixed on the rotating arm 245, the rotating shaft 244, the rotating arm is connected with the rotating arm 244 through a rotating shaft 244, and the rotating shaft 244, the rotating arm 244, the rotating shaft 245, and the rotating shaft 244 is connected with the rotating shaft 245;
the single-shaft loading system 3 comprises an oil source 31, a loading cylinder 32, an energy accumulator 33, a first reversing valve 34, a second reversing valve 35, a pressure gauge 36 and a magnetic displacement sensor 37, wherein the loading cylinder 32 is embedded in the base 11, the magnetic displacement sensor 37 is arranged on the loading cylinder 32, an oil inlet and an oil outlet of the loading cylinder 32 are connected with the oil source 31 through two oil paths, the energy accumulator 33 is connected with one oil path between the loading cylinder 32 and the oil source 31, the pressure gauge 36 and the second reversing valve 35 are both arranged on the same oil path as the energy accumulator 33, and the first reversing valve 34 is arranged on the other oil path;
the measurement and control system 6 comprises a control device 61, a lifting platform 62, a high-speed camera 63 and a microscopic observation device 64, wherein the high-speed camera 63 and the microscopic observation device 64 are arranged on the lifting platform 62, and the control device 61 is connected with the high-speed camera 63, the magnetic displacement sensor 37, the pressure gauge 36, the first dynamic water pressure sensor 44, the second dynamic water pressure sensor 49 and the oil source 31.
Further, the device also comprises a protective door 17, wherein the protective door 17 is arranged on the side part of the bearing device 1, and a transparent observation window 18 is arranged on the protective door 17. The arrangement of the protective door 17 can prevent particles from being sputtered to the outside after the gravel sample 47 is broken in the experimental process, and further influences the surrounding environment.
Further, the device comprises a trigger device, the trigger device comprises a trigger knob 246-1, a reset shaft 246-2 and a spring 246-3, the spring 246-3 is sleeved on the reset shaft 246-2 and supported in the rotating seat 243, one end of the reset shaft 246-2 extends out of the rotating seat 243 and supports the rotating arm 244, a limit tooth 246-4 is arranged on the reset shaft 246-2, a limit groove corresponding to the limit tooth 246-4 is arranged in the rotating seat 243, and the trigger knob 246-1 is fixed at the end of the reset shaft 246-2. When the trigger device is not used, one end of the reset shaft 246-2 extends out of the rotating seat 243 and supports the rotating arm 244, the spring 246-3 is in a compressed state, and the reset shaft 246-2 is in a static state because the limit tooth 246-4 is in a buckling state with the limit groove of the rotating seat 243; when the trigger knob 246-1 is rotated, the limit tooth 246-4 is in a non-lock state with the limit groove of the rotating seat 243 through rotation, and then receives the reset elastic force of the spring 246-3, the reset shaft 246-2 moves into the rotating seat 243 quickly, so that the reset shaft 246-2 enters the rotating seat 243 integrally, at this time, the rotating arm 244, without the support of the reset shaft 246-2, rotates downward around the rotating shaft 245 under the action of gravity, so that the impact block 29 located on the rotating arm 244 falls down along the guide shaft 25.
Further, the control device 61 is a microcomputer.
Further, the guide shaft 25 is provided with a scale 251. The scale 251 can quickly determine the falling distance of the impact block 29, thereby facilitating the calculation of the impact speed of the subsequent impact block 29 after falling.
An experimental method of a gravel medium mesoscopic structure evolution experimental device under osmotic pressure mutation comprises the following specific steps:
A. fastening a prepared gravel sample 47 by using a lantern ring 46, then installing a second water permeable disc 48 and a second dynamic water pressure sensor 49 at the lower end of the gravel sample, sealing the gravel sample with the upper end of a second pressure transmission block 50 through a high-elastic sealing ring 45, installing a first water permeable disc 43 and a first dynamic water pressure sensor 44 at the upper end of the gravel sample 47, and sealing the gravel sample with the lower end of a first pressure transmission block 41 through the high-elastic sealing ring 45 to form a test assembly;
B. contacting the lower end of the test assembly with the upper end of the loading cylinder 32, contacting the upper end of the test assembly with the top beam 14, and limiting the top beam 14 by the top beam 14 through a first nut 15 and a second nut 16;
C. after the osmotic pressure mutation device 2, the single-shaft loading system 3 and the measurement and control system 6 are connected, the whole device connection process is completed;
D. opening the first valve 53 and the second valve 54 to supply water into the cylinder 26 through the water supply port 27 until the water level in the cylinder 26 reaches the position of the overflow port 28, observing whether water leaks from each joint on the whole pipeline, if so, carrying out secondary sealing on the corresponding position, if not, finishing the detection of the sealing performance of the whole water supply pipeline, and closing the first valve 53 and the second valve 54;
E. the single-shaft loading system 3 starts to work, the loading cylinder 32 applies pressure to the gravel sample 47 through the second pressure transmission block 50, the control device 61 controls the loading rate of the pressure and the set maximum pressure value through the magnetic displacement sensor 37 and the pressure gauge 36 in the pressure applying process, and pressure maintaining is carried out after the set maximum pressure value is reached; at the moment, a constant head penetration test is carried out, after the first valve 53 and the second valve 54 are opened, water in the cylinder barrel 26 flows into the grit sample 47 from the water inlet 42 of the first pressure transmission block 41 through a pipeline in a constant water flow manner, flows out of the grit sample 47 from the water outlet 51 of the second pressure transmission block 50, enters the water tank 56 through the flowmeter 55, and after the flowmeter 55 is stabilized, the penetration parameter of the grit medium under the axial pressure can be obtained according to the penetration law;
F. after water flow is stably permeated, the impact block 29 is placed on the end part of the rotating arm 244, the trigger device 246 is opened to enable the rotating shaft 245 to drive the rotating arm 244 to rotate downwards, at the moment, the impact block 29 falls to the cylinder 26 along the guide shaft 25 to impact water in the cylinder 26, so that the osmotic water pressure is instantly changed from low pressure to high pressure, the change condition of the water pressure value in the water permeable disc is detected in real time through the first dynamic water pressure sensor 44 and the second dynamic water pressure sensor 49 and is transmitted to the control device 61, and meanwhile, the high-speed camera 63 records the change image of the sample 47 in real time through the microscopic observation device 64 and transmits the change image to the gravel control device 61;
G. after the experiment is finished, the water supply port 27 and the first valve 53 are closed, the second valve 54 is closed when no water flows into the water pool, the gravel sample 47 is unloaded through the measurement and control system 6 and the single-shaft loading system 3, finally the protection door 17 is opened to take out the gravel sample 47, and the oil source 31 and the measurement and control system 6 are closed;
H. if water is used as the slightly compressible medium, the impact pressure is
In the formula, P d Is the impact pressure; v is the speed of the impact block before contacting water; rho w ，c w The density of water and the propagation speed of the shock wave in the water respectively; rho s 、c s The density of the impact block and the propagation speed of the impact wave in the impact block medium are respectively; analogously also may be taken>
Therefore, the total osmotic pressure at the time of an osmotic pressure jump is P w ＝γ w h+P d In the formula, gamma w Is a container of waterWeighing; h is the vertical distance from the liquid level in the cylinder barrel to the top surface of the gravel sample; analyzing and drawing a curve graph through the acquired image of the microscopic structure of the gravel sample 47, the water pressure data and the loaded pressure value of the sample, and finally obtaining the evolution rule of the microscopic structure of the gravel medium and the pore pressure change rule under the osmotic pressure mutation. />
Claims (4)
1. The device is characterized by comprising a bearing device (1), an osmotic pressure mutation device (2), a single-shaft loading system (3), a measurement and control system (6), a protective door (17) and a trigger device, wherein the bearing device (1) comprises a base (11), a right upright post (12), a left upright post (13) and a top beam (14), the left upright post (13) and the right upright post (12) are both fixed on the base (11), and the top beam (14) is sleeved on the left upright post (13) and the right upright post (12) through connecting holes and is respectively fixed through a first nut (15) and a second nut (16);
a first pressure transmission block (41) and a second pressure transmission block (50) are arranged in the bearing device (1), a water inlet hole (42) is formed in the first pressure transmission block (41), a first permeable disc (43) and a first dynamic water pressure sensor (44) are arranged at the lower end of the water inlet hole (42), a water outlet hole (51) is formed in the second pressure transmission block (50), a second permeable disc (48) and a second dynamic water pressure sensor (49) are arranged at the upper end of the water outlet hole (51), the lower end of the water outlet hole (51) is connected with a water pool (56) through a pipeline, and a second valve (54) and a flow meter (55) are arranged on the pipeline between the water outlet hole (51) and the water pool (56); the protective door (17) is arranged on the side part of the bearing device (1), and a transparent observation window (18) is arranged on the protective door (17);
the seepage pressure mutation device (2) comprises a cross rod (21), a left support leg (22), a right support leg (23), a releaser (24), a guide shaft (25), a cylinder barrel (26) and an impact block (29), the lower ends of the left support leg (22) and the right support leg (23) are fixed on the cylinder barrel (26), the upper ends of the left support leg (22) and the right support leg (23) are respectively provided with a U-shaped fork structure, the side part of the cylinder barrel (26) is provided with a water supply port (27) and an overflow port (28), the position of the water supply port (27) is higher than that of the overflow port (28), the bottom of the cylinder barrel (26) is communicated with one end of the water accumulator (52), the other end of the water accumulator (52) is communicated with a water inlet hole (42) of a first transmission block (41) through a pipeline, a first valve (53) is arranged on the pipeline between the water accumulator (52) and the water inlet hole (42), the cross rod (21) is fixed at the upper end of the guide shaft (25), the impact block (29) is slidably sleeved on the guide shaft (25), the lower end of the guide shaft (25) is provided with a section (252), the length of the support leg (21) is greater than that of the linear positioning screw (22) and the length of the release block (242), and the linear positioning seat (242), and the length of the linear guide shaft (21) are greater than that of the linear guide shaft (22), and the linear guide shaft (242), and the linear guide block (23), and the linear guide shaft (242), and the linear guide block (21), and the linear guide shaft (242), and the linear guide shaft (21) are arranged between the linear guide block (242), and the linear guide block (21) respectively, the movable body (242) is sleeved on the right supporting leg (23) and fixed through a positioning screw rod (241), the rotating seat (243) is fixed on one side of the movable body (242), the rotating shaft (245) is arranged on the rotating seat (243), one end of the rotating arm (244) is movably connected with the rotating seat (243) through the rotating shaft (245), the other end of the rotating arm (244) is of a branched structure, and the guide shaft (25) is located in the branched structure;
the single-shaft loading system (3) comprises an oil source (31), a loading cylinder (32), an energy accumulator (33), a first reversing valve (34), a second reversing valve (35), a pressure gauge (36) and a magnetic displacement sensor (37), wherein the loading cylinder (32) is embedded in a base (11), the magnetic displacement sensor (37) is arranged on the loading cylinder (32), an oil inlet and an oil outlet of the loading cylinder (32) are divided into two oil paths to be connected with the oil source (31), the energy accumulator (33) is connected to one of the oil paths between the loading cylinder (32) and the oil source (31), the pressure gauge (36) and the second reversing valve (35) are both arranged on the same oil path as the energy accumulator (33), and the first reversing valve (34) is arranged on the other oil path;
the measurement and control system (6) comprises a control device (61), a lifting table (62), a high-speed camera (63) and a microscopic observation device (64), wherein the high-speed camera (63) and the microscopic observation device (64) are arranged on the lifting table (62), and the control device (61) is connected with the high-speed camera (63), the magnetic displacement sensor (37), the pressure gauge (36), the first dynamic water pressure sensor (44), the second dynamic water pressure sensor (49) and the oil source (31);
the triggering device is composed of a triggering knob (246-1), a resetting shaft (246-2) and a spring (246-3), wherein the resetting shaft (246-2) is sleeved with the spring (246-3) and supported in the rotating seat (243), one end of the resetting shaft (246-2) extends out of the rotating seat (243) and supports the rotating arm (244), the resetting shaft (246-2) is provided with limiting teeth (246-4), limiting grooves corresponding to the limiting teeth (246-4) are formed in the rotating seat (243), and the triggering knob (246-1) is fixed at the end part of the resetting shaft (246-2).
2. The experimental device for evolution of fine structure of gravel medium under osmotic pressure sudden change as claimed in claim 1, wherein said control device (61) is a microcomputer.
3. The experimental apparatus for the evolution of the microstructure of a gravel medium under an osmotic pressure sudden change is characterized in that a scale (251) is arranged on the guide shaft (25).
4. The experimental method for the experimental device for the evolution of the microstructure of the gravel medium under the osmotic pressure sudden change is characterized by comprising the following specific steps:
A. fastening the prepared gravel sample (47) by using a lantern ring (46), then installing a second water permeable disc (48) and a second dynamic water pressure sensor (49) at the lower end of the gravel sample and sealing the gravel sample with the upper end of a second pressure transmission block (50) through a high-elastic sealing ring (45), installing a first water permeable disc (43) and a first dynamic water pressure sensor (44) at the upper end of the gravel sample (47) and sealing the gravel sample with the lower end of a first pressure transmission block (41) through the high-elastic sealing ring (45) to form a test assembly;
B. the lower end of the testing combination body is contacted with the upper end of the loading cylinder (32), the upper end of the testing combination body is contacted with the top beam (14), and the top beam (14) is limited to the top beam (14) through a first nut (15) and a second nut (16);
C. after the osmotic pressure mutation device (2), the uniaxial loading system (3) and the measurement and control system (6) are connected, the whole device connection process is completed;
D. opening the first valve (53) and the second valve (54) to supply water into the cylinder (26) through the water supply port (27) until the water level in the cylinder (26) reaches the position of the overflow port (28), stopping, observing whether water leaks from each joint on the whole pipeline, if so, carrying out secondary sealing on the corresponding position, if not, finishing the detection of the sealing performance of the whole water supply pipeline, and closing the first valve (53) and the second valve (54);
E. enabling the single-shaft loading system (3) to start to work, enabling the loading cylinder (32) to apply pressure to the gravel sample (47) through the second pressure transmission block (50), controlling the loading rate of the pressure and the set maximum pressure value through the magnetic displacement sensor (37) and the pressure gauge (36) by the control device (61) in the pressure applying process, and maintaining the pressure after the set maximum pressure value is reached; at the moment, a constant water head penetration test is carried out, after a first valve (53) and a second valve (54) are opened, water in a cylinder (26) flows into a gravel sample (47) from a water inlet (42) of a first pressure transfer block (41) through a pipeline in a constant water flow mode, flows out of the gravel sample (47) from a water outlet (51) of a second pressure transfer block (50), enters a water pool (56) through a flowmeter (55), and when the flowmeter (55) is stabilized, penetration parameters of gravel media under the axial pressure can be obtained according to a penetration law;
F. after water flow is stably permeated, the impact block (29) is arranged on the end part of the rotating arm (244), the trigger device (246) is opened to enable the rotating shaft (245) to drive the rotating arm (244) to rotate downwards, at the moment, the impact block (29) falls to the cylinder barrel (26) along the guide shaft (25) to impact water in the cylinder barrel (26), so that the osmotic water pressure is instantly suddenly changed from low pressure to high pressure, the water pressure change condition in the water permeable disk is detected in real time through the first dynamic water pressure sensor (44) and the second dynamic water pressure sensor (49) and is transmitted to the control device (61), and meanwhile, the high-speed camera (63) records the change image of the gravel sample (47) in real time through the microscopic observation device (64) and transmits the change image to the control device (61);
G. after the experiment is finished, the water supply port (27) and the first valve (53) are closed, the second valve (54) is closed when no water flows into the water pool, the gravel sample (47) is unloaded through the measurement and control system (6) and the single-shaft loading system (3), finally, the protective door (17) is opened to take out the gravel sample (47), and the oil source (31) and the measurement and control system (6) are closed;
H. analyzing and drawing a curve graph through the acquired microscopic structure image of the gravel sample (47), water pressure data and the loaded pressure value of the sample, and finally obtaining the evolution rule of the microscopic structure of the gravel medium and the pore pressure change rule under the osmotic pressure mutation.
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