CN109211673B - Water-rich bedrock section inclined shaft freezing well wall stress simulation test system and method - Google Patents
Water-rich bedrock section inclined shaft freezing well wall stress simulation test system and method Download PDFInfo
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Abstract
The invention discloses a water-rich bedrock section inclined shaft freezing well wall stress simulation test system and a method, wherein the system comprises a high-pressure test bed, a pressure loading system, a freezing system and a data acquisition system; the high-pressure test bed comprises a pressure bearing cylinder, an upper end cover and a base; in the pressure loading system, a confining pressure pressurizing hole of a pressure-bearing cylinder injects water into a confining pressure pressurizing cavity to apply confining pressure, an axial pressure pressurizing hole on a backing plate injects water into the axial pressure pressurizing cavity to apply axial pressure, and pressurizing holes of an upper sealing plate and a lower sealing plate inject water into pore surrounding rocks to apply pore water pressure; in the freezing system, a model well wall is used as a freezing liquid circulation channel and is connected with an external cold source through a liquid inlet pipe and a liquid outlet pipe for freezing; in the data acquisition system, the sensors are adhered to the inner wall and the outer wall of the well wall and buried in the rock mass, so that strain, temperature and stress information can be obtained in real time. The method can simulate the influence of pore water pressure on the wall of the inclined shaft in the unfreezing process of the frozen wall of the water-rich bedrock section, and provides support and test guidance for the research and design of the wall of the water-rich bedrock section.
Description
Technical Field
The invention relates to a simulation experiment system for applying confining pressure and pore water pressure to a wall of an inclined shaft, in particular to a system and a method for simulating stress of a freezing wall of the inclined shaft at a water-rich bedrock section, and belongs to the technical field of underground simulation experiment systems.
Background
Along with the development of coal in western regions, the coal mine production capacity of the regions is higher, strata penetrated by well walls of the regions mainly comprise rock strata of chalk series, dwarfism series and the like, the strata are formed later, the strength is low, the water content is high, the strata are easy to be argillized when meeting water, water in a water-bearing layer mainly comprises pore water, slurry is difficult to diffuse during grouting, the grouting effect is poor, and therefore, a freezing method has to be adopted for constructing a foundation stratum with high water content; the inclined shaft exploitation method is an underground exploitation method for exploiting an ore deposit by using an inclined shaft, is suitable for the ore deposit with an ore body inclination angle of 12-15 degrees, and the relative position of the inclined shaft and the ore body is mainly determined by the terrain of an ore area, engineering geology and the occurrence conditions of the ore body. Therefore, the design problem of the freezing well wall of the inclined well at the bedrock section rich in pore water is increasingly concerned, rocks at the bedrock section have certain self-stability, the influence of the action of a ground stress field does not threaten the well wall, the well wall is damaged under the action of the pore water pressure in the unfreezing process of the frozen wall, the conventional simulation test device aiming at the underground well, such as a vertical well high-pressure test bed, is round in simulated well wall shape and cannot realize the freezing and unfreezing working conditions of the stratum, the inclined well wall is of a special-shaped structure, the damage of the well wall at the water-rich bedrock section is mostly caused by the pore water pressure in the unfreezing process of the frozen wall, and a common simulation test system cannot truly simulate the actual stress condition of the freezing well wall of the inclined well, so that reliable reference cannot be provided for the design.
Disclosure of Invention
In order to overcome various defects in the prior art, the invention provides a system and a method for stress simulation test of a freezing well wall of an inclined well at a water-rich bedrock section, which can test the stress deformation law of the inclined well wall in bedrock rich in pore water under the action of pore water pressure in the unfreezing process of the freezing wall, fully know the influence of the pore water pressure in the unfreezing process of the freezing wall on the stress deformation law of the well wall, and provide guidance and reference for the design of the freezing well wall of the inclined well at the water-rich bedrock section.
In order to solve the problems, the invention relates to a stress simulation test system for a freezing well wall of an inclined shaft at a water-rich bedrock section, which comprises a high-pressure test bed, a pressure loading system and a data acquisition system, wherein the high-pressure test bed comprises an upper end cover, a pressure bearing cylinder and a base, the bottom end of the upper end cover is fixed at the upper end of the pressure bearing cylinder through a nut, a screw and a gasket, the upper end of the base is fixed at the lower end of the pressure bearing cylinder through the nut, the screw and the gasket, a model well wall is arranged in the pressure bearing cylinder, test pore surrounding rocks are arranged around the model well wall, a lower sealing plate is arranged between the lower end of the pore surrounding rocks and the upper end of the base, a shaft pressing backing plate and an upper sealing plate are arranged between the upper end of the pore surrounding rocks and the lower end of the upper end cover, the shaft pressing backing plate is arranged at the upper end of the upper sealing plate in a sealing way, the upper sealing, the sealing ring is sealed with the model well wall through an axial sealing ring, the inner diameter of a central hole of the axial pressing base plate is larger than that of central holes of the upper sealing plate and the lower sealing plate, a circle of groove is arranged on one surface, in contact with the axial pressing base plate, of the upper sealing plate along the circumferential direction, and the contact parts of the upper end cover, the axial pressing base plate, the upper sealing plate, the pressure bearing cylinder, the lower sealing plate and the end surface of the base are sealed through radial sealing rings;
the pressure loading system comprises a servo pressurizing and pressure stabilizing system and a high-pressure pipeline, a layer of rubber film is tightly wrapped outside the upper sealing plate, the pore surrounding rock and the lower sealing plate, a surrounding pressure cavity is formed by a cavity between the rubber film and the pressure bearing cylinder, and a surrounding pressure hole is formed in the side wall of the pressure bearing cylinder; an axial pressurizing cavity is formed by a circumferential groove at the upper end of the upper sealing plate and a cavity between the axial pressing base plate, an axial pressurizing hole is formed in the axial pressing base plate, an upper pore water pressure pressurizing hole is formed in the upper sealing plate, a lower pore water pressure pressurizing hole is formed in the lower sealing plate, and the servo pressurizing and pressure stabilizing system is respectively connected with the confining pressure pressurizing hole through a high-pressure pipeline to inject water into the confining pressure pressurizing cavity to apply confining pressure, is connected with the axial pressurizing hole to inject water into the axial pressurizing cavity to apply axial load, and is connected with the pore water pressure pressurizing hole and the lower pore water pressure pressurizing hole to load pore water pressure into pore surrounding rock;
the data acquisition system comprises a sensor group, a data acquisition instrument and a computer, wherein the sensor group is arranged in the model well wall and the pore surrounding rock, the conducting wires of all sensors in the sensor group are connected with the data acquisition instrument, and the data acquisition instrument is connected with the computer.
Furthermore, in order to reduce the friction force between the pore surrounding rock and the contact interfaces of the upper sealing plate and the lower sealing plate, a lubricating layer with three oil films and two films is arranged at the contact interfaces of the pore surrounding rock and the upper sealing plate and the lower sealing plate, and the lubricating layer comprises a layer of molybdenum disulfide lubricating grease, a layer of polytetrafluoroethylene film, a layer of molybdenum disulfide lubricating grease, a layer of polytetrafluoroethylene film and a layer of molybdenum disulfide lubricating grease which are sequentially and uniformly laid from the lower sealing plate to the surrounding rock interface or from the upper sealing plate to the surrounding rock interface;
in order to improve the transmission speed of pore water pressure and improve the loading uniformity, a layer of permeable cloth is laid between the lubricating layer and the pore surrounding rock interface, and the pore water pressure holes in the upper sealing plate and the lower sealing plate penetrate through the lubricating layer and extend into the permeable cloth, so that water is ensured to be injected from the pore water pressure pressurizing holes, and the water is rapidly diffused in the permeable cloth and is uniformly transmitted into the pore surrounding rock.
The test system further comprises a freezing system, the freezing system comprises a low-temperature refrigerator and a freezing liquid circulation channel, the upper end of the model well wall is connected with the liquid outlet pipe, the lower end of the model well wall is connected with the liquid inlet pipe, the freezing liquid circulation channel is formed by the model well wall, the inner cavity between the liquid inlet pipe and the liquid outlet pipe, and the inlet of the liquid inlet pipe and the outlet of the liquid outlet pipe are respectively connected with the low-temperature refrigerator.
And (3) introducing low-temperature freezing liquid into the freezing liquid circulation channel through a low-temperature refrigerator to simulate the freezing process of the stratum, wherein the upper end and the lower end of the model well wall are provided with sealing grooves for being connected with a liquid inlet pipe and a liquid outlet pipe in a sealing manner.
Furthermore, the sensor group comprises a plurality of strain sensors and a plurality of temperature sensors which are adhered to the inner wall and the outer wall of the model well wall, and a temperature sensor and a soil pressure gauge which are buried in pore surrounding rocks, wherein the lead of the temperature sensor and the lead of the soil pressure gauge in the pore surrounding rocks, the lead of the strain sensor and the lead of the temperature sensor which are adhered to the outer wall of the model well wall are respectively led out to the data acquisition instrument through lead holes which are formed in the lower sealing plate; and a lead of the strain sensor and a lead of the temperature sensor which are adhered to the inner wall of the model well wall are respectively led out to a data acquisition instrument through a circular flange joint arranged on the outer wall of the liquid outlet pipe.
And a lead groove which has extremely small width and depth and is communicated with the top end of the model well wall is axially formed on the outer wall of the model well wall at a position close to the contact interface between the upper sealing plate and the pore surrounding rock. The groove is filled with the sealant, so that the lead of the optical fiber type small sensing device can be led out, the surface of the sensor needs to be polished smoothly after the sealant is cured, the sensor is smoothly transited to the surface of the well wall, and the sealing performance of the test bed is not affected.
In order to avoid the sharp hard object existing in the pore surrounding rock from scratching the rubber membrane, a layer of oxygen resin series cementing agent is evenly smeared on the contact interface of the outer surface of the pore surrounding rock and the rubber membrane. The outer surface of the pore surrounding rock is cleaned before smearing, after the epoxy resin cementing agent is cured, the surface of the epoxy resin cementing agent is treated to be smooth and flat, and a rubber film is sleeved after a layer of plastic film is wrapped.
Furthermore, the liquid inlet pipe and the liquid outlet pipe are made of low-temperature-resistant flexible materials and are fixed through a sealing clamping groove II in the wall of the model well. The low-temperature-resistant flexible material can be latex, rubber and the like.
The upper end face of the upper sealing plate is close to the model well wall and the lower end face of the lower sealing plate is close to the model well wall, a plurality of rings of copper coil pipes are arranged along the circumferential direction, and the copper coil pipes are connected with a low-temperature refrigerator in the unfreezing process of the frozen well wall.
In order to prevent water from entering the contact interface between the model well wall and the pore surrounding rock along the contact interface between the pore surrounding rock and the upper sealing plate and the contact interface between the pore surrounding rock and the lower sealing plate during thawing and influence simulation experiment results, copper coil pipes at the upper end and the lower end are connected into a cryogenic refrigerator, so that the thawing speed of the top end and the bottom end of the pore surrounding rock is lower than that of the middle layer.
In order to ensure the sealing fixation of the rubber sleeve, sealing clamping grooves I are formed in the outer diameter end faces of the axial compression base plate, the upper sealing plate and the lower sealing plate.
In order to further improve the heat insulation performance of the system, the outer side of the whole stress simulation test bed is wrapped with a heat insulation cotton material for heat insulation treatment.
A simulation test method for the stress of the freezing well wall of an inclined well at a water-rich bedrock section comprises the following steps,
firstly, assembling a simulation test bed, and specifically comprising the following steps:
a, manufacturing a model well wall, and then sticking a plurality of strain sensors and temperature sensors on the inner wall and the outer wall of the model well wall and protecting the strain sensors and the temperature sensors;
b, fixing a copper coil pipe at a preset position of a lower sealing plate, fixing the lower sealing plate on a base through a tensioning screw and a tensioning flange, and enabling the central line of the lower sealing plate to coincide with the base;
c, connecting the liquid inlet pipe with the bottom end of the model well wall through a sealing clamping groove II, inserting the bottom end of the model well wall into the lower sealing plate, sealing the liquid inlet pipe and the lower sealing plate through an axial sealing ring, leading the liquid inlet pipe out from the bottom end of the base, ensuring the centering and the verticality of the model well wall through a horizontal ruler and a verticality tester, and recording the distance between the model well wall and the outer diameter boundary line of the lower sealing plate in each direction by using the horizontal ruler;
d, fixing the lower end of the pressure-bearing cylinder at the upper end of the base through a nut, a screw and a gasket, and sealing the contact part between the two through a radial sealing ring;
e, penetrating the upper sealing plate through the wall of the model well, then hoisting the upper end cover, fixing the lower end of the upper end cover at the upper end of the pressure bearing cylinder through a nut, a screw and a gasket, and fixing the upper sealing plate on the upper end cover through a tensioning screw, a tensioning flange, a hexagon nut and a plain washer to finish the assembly of the test bed;
and step two, carrying out hydrostatic pressure test, and specifically comprising the following steps:
a, connecting each sensor into a data acquisition instrument, connecting confining pressure pressurization holes into a servo pressurization and pressure stabilization system through a high-pressure pipeline, closing the rest pressurization holes, and injecting water into a test space; through hydrostatic pressure test, the tightness of the test bed is tested, whether sensors on the inner wall and the outer wall of the model well wall are damaged or not is detected, and the initial stress and the assembly stress of the model well wall are eliminated;
b, after the hydrostatic pressure test is finished, removing the upper end cover and the upper sealing plate for draining, and removing the pressure bearing cylinder after draining;
step three, manufacturing the pore surrounding rock, which comprises the following specific steps:
a, performing lubrication treatment of three oil films and two films on a contact interface of a lower sealing plate and a pore surrounding rock, specifically, uniformly smearing a layer of molybdenum disulfide lubricating grease on the upper end of the lower sealing plate, paving a layer of polytetrafluoroethylene film on the molybdenum disulfide lubricating grease, paving a layer of molybdenum disulfide lubricating grease on the polytetrafluoroethylene film, and paving a layer of permeable cloth on the molybdenum disulfide lubricating grease;
b, installing a pore surrounding rock template, pouring pore surrounding rock in a layered mode, leading the temperature sensor and the soil pressure meter through a lead hole, sealing, and placing the temperature sensor and the soil pressure meter at a pre-buried point; the pore surrounding rock is compacted by a rammer until the design height is reached, one layer is loosely laid after the design height is reached, the test bed is compacted when being assembled, the compaction process needs to ensure the uniformity between layers and the uniformity of different parts of the same layer, meanwhile, the protection of a test element and a transmission line needs to be paid attention to in the compaction process, a leveling rod is used for centering and correcting the model well wall in each layer, the model well wall is prevented from deflecting in the compaction process, the reserved height at the top needs to be reasonable, the reserved height is too small, nuts and screws are difficult to fasten, the sealing of a test space cannot be realized, the reserved height is too large, an axial compression base plate is separated from an upper end cover, and the sealing cannot be realized;
c, lubricating an interface of the upper sealing plate in contact with the pore surrounding rock by using three oil films, paving a layer of permeable cloth between the lubricating layer and the top of the pore surrounding rock, placing the upper sealing plate on the lubricating layer, placing the axial compression backing plate on the upper part of the upper sealing plate, and maintaining the pore surrounding rock, wherein a maintenance shed needs to be built when the weather is cold, so that the temperature and the humidity for maintaining the pore surrounding rock are ensured;
and step four, saturating the pore surrounding rock under a pressure state, and specifically comprises the following steps:
a, after pore surrounding rock is formed, detaching a pore surrounding rock template, cleaning and brushing oil on the detached template, uniformly coating an epoxy resin series cementing agent outside the pore surrounding rock, after the epoxy resin series cementing agent is hardened, performing smooth and flat treatment on the surface, sleeving a rubber film, and sealing and fixing the rubber film through a shaft pressing base plate, an upper sealing plate and a sealing clamping groove I outside a lower sealing plate;
b, sequentially fixing the bottom end of the pressure-bearing cylinder at the upper end of the base, and fixing the bottom end of the upper end cover at the top end of the pressure-bearing cylinder to complete the assembly of the test bed;
c, respectively connecting a servo pressurizing and pressure stabilizing system into a confining pressure pressurizing hole and a lower pore water pressure pressurizing hole through a high-pressure pipeline, connecting the upper pore water pressure pressurizing hole with a vacuum pipeline, a drying tower, a vacuum vessel and a vacuum pump, injecting water through the confining pressure pressurizing hole to apply confining pressure, injecting water through the lower pore water pressure pressurizing hole to apply pore water pressure after the confining pressure is stable, simultaneously opening the upper pore water pressure pressurizing hole, vacuumizing through a vacuum pump, saturating pore surrounding rock under a pressure state, and keeping the pore water pressure to be smaller than the confining pressure all the time in a loading process; after the upper pore water pressure pressurizing hole stably discharges water, closing the upper pore water pressure pressurizing hole, and if the pore water pressure in the pore surrounding rock is kept stable, considering that the pore surrounding rock is saturated;
d, unloading the pore water pressure to 0MPa and closing the lower pore water pressure pressurizing hole after the saturation is finished, unloading the confining pressure to 0MPa after the pore water pressure is unloaded, and closing the confining pressure pressurizing hole;
fifthly, performing a simulation test on the effect of pore water pressure on the well wall in the unfreezing process of the frozen wall, and specifically performing the following steps:
a, after each pressure is unloaded, connecting a liquid outlet pipe with the top end of a model well wall through a sealing clamping groove II, leading out a sensor lead on the inner wall of the model well wall through a circular flange joint, and sealing; installing a freezing system, and respectively connecting the liquid inlet pipe and the liquid outlet pipe with the low-temperature refrigerator, making heat preservation measures and starting freezing;
b, after freezing is finished, opening a confining pressure pressurizing hole and a lower pore water pressure pressurizing hole, respectively connecting the upper pore water pressure pressurizing hole and the axial pressure pressurizing hole into a servo pressurizing and pressure stabilizing system, starting stage pressurization, monitoring the change law of a stress field and a temperature field of the model well wall and the pore surrounding rock in the unfreezing process, ensuring that the confining pressure is always greater than the axial pressure and the pore water pressure in the stage pressurization process, connecting a copper coil pipe into a low-temperature refrigerator in the unfreezing process, ensuring that the unfreezing speed of the top end and the bottom end of the pore surrounding rock is slower than that of the middle layer, and preventing water from entering the contact interface of the model well wall and the pore surrounding rock along the contact interface of the pore surrounding rock and the upper sealing plate and the lower sealing plate during unfreezing and directly acting on the model well wall.
The simulation method can realize the simulation of the stress deformation law of the inclined shaft wall under the action of the pore water pressure in the unfreezing process of the basement rock frozen wall rich in pore water, fully know the influence of the pore water pressure on the stress deformation law of the inclined shaft wall in the unfreezing process of the frozen wall, further provide guidance for the design of the inclined shaft frozen wall, and is particularly suitable for the design research of the inclined shaft frozen wall of the basement rock stratum rich in pore water.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1;
FIG. 3 is an enlarged view of the point A in FIG. 1;
FIG. 4 is an enlarged view of the point B in FIG. 1;
FIG. 5 is an enlarged view of FIG. 1 at C;
in the figure: 1. the sealing device comprises an upper end cover, 2. a pressure bearing cylinder, 3. a base, 4. a gasket, 5. a nut, 6. a screw, 7. a shaft pressing backing plate, 8. an upper sealing plate, 9. a lower sealing plate, 10. a tensioning screw, 11. a tensioning flange, 12. a flat gasket, 13. a hexagon nut, 14. a liquid inlet pipe, 15. a liquid outlet pipe, 16. a circular flange joint, 17. a copper coil pipe, 18. a model well wall, 19. a pore surrounding rock, 20. an epoxy resin series cementing agent, 21. a rubber film, 22. molybdenum disulfide lubricating grease, 23. a polytetrafluoroethylene film, 24. a water permeable cloth, 25. a surrounding pressure hole, 26. a surrounding pressure cavity, 27. a hanging ring hole, 28. a shaft pressure hole, 29. a shaft pressure cavity, 30. an upper pore hydraulic pressure hole, 31. a lower pore hydraulic pressure hole, 32. a lead hole, 33. a sealing clamping groove I, 34. a lead groove, 35. a sealing clamping groove II, 36. an axial sealing ring, 37. and a radial sealing ring.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments.
As shown in figures 1 and 2, the water-rich bedrock section inclined shaft freezing well wall stress simulation test system comprises a high-pressure test bed, a pressure loading system and a data acquisition system, wherein the high-pressure test bed comprises an upper end cover 1, a pressure bearing cylinder 2 and a base 3, the bottom end of the upper end cover 1 is fixed at the upper end of the pressure bearing cylinder 2 through a nut 5, a screw 6 and a gasket 4, the upper end of the base 3 is fixed at the lower end of the pressure bearing cylinder 2 through the nut 5, the screw 6 and the gasket 4, a model well wall 18 is arranged in the pressure bearing cylinder 2, pore surrounding rocks 19 for test are arranged around the model well wall 18, a lower sealing plate 9 is arranged between the lower end of the pore surrounding rocks 19 and the upper end of the base 3, a shaft pressure backing plate 7 and an upper sealing plate 8 are arranged between the upper end of the pore surrounding rocks 19 and the lower end of the upper end cover 1, the shaft pressure backing plate 7 is sealed at the upper end of the upper sealing plate 8, and the lower sealing, the central holes of the upper sealing plate 8 and the lower sealing plate 9 are equal to the outer diameter of the model well wall 18, and the upper sealing plate and the lower sealing plate are sealed with the model well wall 18 through an axial sealing ring 36, the inner diameter of the central hole of the axial pressing backing plate 7 is larger than the inner diameters of the central holes of the upper sealing plate 8 and the lower sealing plate 9, one surface of the upper sealing plate 8, which is contacted with the axial pressing backing plate 7, is provided with a circle of groove along the circumferential direction, and the contact parts of the end surfaces between the upper end cover 1, the axial pressing backing plate 7, the upper sealing plate 8, the pressure bearing cylinder 2, the lower sealing plate;
the pressure loading system comprises a servo pressurizing and pressure stabilizing system and a high-pressure pipeline, a layer of rubber film 21 is tightly wrapped outside the upper sealing plate 8, the pore surrounding rock 19 and the lower sealing plate 9, a confining pressure pressurizing cavity 26 is formed by a cavity between the rubber film 21 and the pressure-bearing cylinder 2, and a confining pressure pressurizing hole 25 is formed in the side wall of the pressure-bearing cylinder 2; an axial pressurizing cavity 29 is formed by a circumferential groove at the upper end of the upper sealing plate 8 and a cavity between the axial pressing backing plate 7, an axial pressurizing hole 28 is formed in the axial pressing backing plate 7, an upper pore water pressure pressurizing hole 30 is formed in the upper sealing plate 8, a lower pore water pressure pressurizing hole 31 is formed in the lower sealing plate 9, and a servo pressurizing and pressure stabilizing system is respectively connected with the confining pressure pressurizing hole 25 through a high-pressure pipeline to inject water into the confining pressure pressurizing cavity 26 to apply confining pressure, is connected with the axial pressurizing hole 28 to inject water into the axial pressurizing cavity to apply axial load, and is connected with the upper pore water pressure pressurizing hole 30 and the lower pore water pressure pressurizing hole 31 to load pore water pressure into the pore surrounding rock;
the data acquisition system comprises a sensor group, a data acquisition instrument and a computer, wherein the sensor group is arranged in the model well wall 18 and the pore surrounding rock 19, the conducting wires of all sensors in the sensor group are connected with the data acquisition instrument, and the data acquisition instrument is connected with the computer.
As shown in fig. 3, in order to reduce the friction force between the pore surrounding rock 19 and the contact interface between the pore surrounding rock and the upper sealing plate 8 and the lower sealing plate 9, a lubricating layer of "three oil and two films" is arranged at the contact interface between the pore surrounding rock and the upper sealing plate and the lower sealing plate, and the lubricating layer comprises a layer of molybdenum disulfide lubricating grease 22, a layer of polytetrafluoroethylene film 23, a layer of molybdenum disulfide lubricating grease 22, a layer of polytetrafluoroethylene film 23 and a layer of molybdenum disulfide lubricating grease 22 which are uniformly laid in sequence from the lower sealing plate to the surrounding rock interface or from the upper sealing plate to the surrounding rock interface;
in order to improve the transmission speed of pore water pressure and improve the uniformity of loading, a layer of permeable cloth 24 is laid between the lubricating layer and the pore surrounding rock interface, and pore water pressure holes in the upper sealing plate 8 and the lower sealing plate 9 penetrate through the lubricating layer and extend into the permeable cloth, so that water is ensured to be injected from the pore water pressure pressurizing holes, and is rapidly diffused in the permeable cloth and uniformly transmitted into the pore surrounding rock.
The test system further comprises a freezing system, the freezing system comprises a low-temperature refrigerator and a freezing liquid circulation channel, the upper end of the model well wall 18 is connected with the liquid outlet pipe 15, the lower end of the model well wall is connected with the liquid inlet pipe 14, an inner cavity among the model well wall 18, the liquid inlet pipe 14 and the liquid outlet pipe 15 forms the freezing liquid circulation channel, and an inlet of the liquid inlet pipe 14 and an outlet of the liquid outlet pipe 15 are respectively connected with the low-temperature refrigerator.
And (3) introducing low-temperature freezing liquid into the freezing liquid circulation channel through a low-temperature refrigerator to simulate the freezing process of the stratum, wherein the upper end and the lower end of the model well wall are provided with sealing grooves for being connected with a liquid inlet pipe and a liquid outlet pipe in a sealing manner.
Further, the sensor group comprises a plurality of strain sensors and a plurality of temperature sensors which are adhered to the inner wall and the outer wall of the model well wall 18, as well as a temperature sensor and a soil pressure gauge which are buried in the pore surrounding rock 19, wherein the lead of the temperature sensor and the lead of the soil pressure gauge in the pore surrounding rock 19, the lead of the strain sensor and the lead of the temperature sensor which are adhered to the outer wall of the model well wall are respectively led out to the data acquisition instrument through lead holes 32 which are formed in the lower sealing plate 9; the lead of the strain sensor and the lead of the temperature sensor which are adhered to the inner wall of the model well wall 18 are respectively led out to a data acquisition instrument through a circular flange joint 16 arranged on the outer wall of the liquid outlet pipe 15.
As shown in fig. 5, a wire guiding groove 34 with extremely small width and depth is axially arranged on the outer wall of the model well wall 18 near the contact interface between the upper sealing plate and the surrounding rocks of the pores, and the wire guiding groove is communicated to the top end of the model well wall. The groove is filled with the sealant, so that the lead of the optical fiber type fine sensing device can be led out to the data acquisition instrument, the surface of the sensor needs to be polished smoothly after the sealant is cured, the sensor is smoothly transited to the surface of the well wall, and the sealing performance of the test bed is not affected. The position, the width and the depth of the lead groove arranged on the outer wall of the model well wall are set on the principle that the stress of the well wall is not influenced, and the position of the lead groove is required to avoid the stress control key point of the model well wall and the position near the key point.
As shown in FIG. 4, in order to avoid the rubber membrane from being scratched by the sharp and hard objects in the pore surrounding rock, a layer of the epoxy resin binder 20 or the road asphalt with high penetration is uniformly coated on the interface between the outer surface of the pore surrounding rock 19 and the rubber membrane 21. Before smearing, the outer surface of the pore surrounding rock 19 is cleaned, after the epoxy resin series cementing agent 20 is cured, the surface of the epoxy resin series cementing agent is treated to be smooth and flat, and a rubber film 21 is sleeved after a layer of plastic film is wrapped.
Further, the liquid inlet pipe 14 and the liquid outlet pipe 15 are made of low-temperature-resistant flexible materials and are fixed through a sealing clamping groove II35 on the wall of the model well. The low-temperature-resistant flexible material can be silica gel, rubber and the like.
And a plurality of circles of copper coil pipes 17 are arranged on the upper end surface of the upper sealing plate 8 and close to the model well wall 18 and on the lower end surface of the lower sealing plate 9 and close to the model well wall 18 in the circumferential direction, and the copper coil pipes 17 are connected with a cryogenic refrigerator in the unfreezing process of the frozen well wall.
In order to prevent water from entering the contact interface between the model well wall 18 and the pore surrounding rock 19 along the contact interface between the pore surrounding rock 19 and the upper sealing plate 8 and the contact interface between the pore surrounding rock 9 during thawing and influence the simulation experiment result, the copper coil pipes 17 at the upper end and the lower end are connected into the cryogenic refrigerator, so that the thawing speed of the top end and the bottom end of the pore surrounding rock 19 is lower than that of the middle layer.
In order to ensure the sealing fixation of the rubber sleeve 21, sealing grooves I33 are arranged on the outer diameter end faces of the shaft pressing base plate 7, the upper sealing plate 8 and the lower sealing plate 9.
In order to further improve the heat insulation performance of the system, the outer side of the whole stress simulation test bed is wrapped with a heat insulation cotton material for heat insulation treatment.
A simulation test method for the stress of the freezing well wall of an inclined well at a water-rich bedrock section comprises the following steps,
firstly, assembling a simulation test bed, and specifically comprising the following steps:
a, manufacturing a model well wall 18, and then sticking a plurality of strain sensors and temperature sensors on the inner wall and the outer wall of the model well wall 18 and protecting the strain sensors and the temperature sensors;
b, fixing a copper coil 17 at a preset position of a lower sealing plate 9, fixing the lower sealing plate 9 on a base 3 through a tensioning screw 10 and a tensioning flange 11, and enabling the central line of the lower sealing plate 9 to coincide with the base 3;
c, connecting the liquid inlet pipe 14 with the bottom end of the model well wall 18 through a sealing clamping groove II35, inserting the bottom end of the model well wall 18 into the lower sealing plate 9, sealing the bottom end of the model well wall 18 and the lower sealing plate by an axial sealing ring 36, leading the liquid inlet pipe out from the bottom end of the base 3, ensuring the centering and the verticality of the model well wall 18 through a horizontal ruler and a verticality determinator, and recording the distance between the model well wall 18 and the outer diameter boundary line of the lower sealing plate 9 in each direction by the horizontal ruler;
d, fixing the lower end of the pressure bearing cylinder 2 at the upper end of the base 3 through a nut 5, a screw 6 and a gasket 4, and sealing the contact part between the two through a radial sealing ring 37;
e, enabling the upper sealing plate 8 to penetrate through a model well wall 18, then hoisting the upper end cover 1, fixing the lower end of the upper end cover 1 at the upper end of the pressure bearing cylinder 2 through the nut 5, the screw 6 and the gasket 4, and fixing the upper sealing plate on the upper end cover 1 through the tensioning screw 10, the tensioning flange 11, the hexagon nut 12 and the flat washer 13 to complete the assembly of the test bed;
and step two, carrying out hydrostatic pressure test, and specifically comprising the following steps:
a, connecting each sensor into a data acquisition instrument, connecting a confining pressure pressurizing hole 25 into a servo pressurizing and pressure stabilizing system through a high-pressure pipeline, closing the rest pressurizing holes and injecting water into a test space; through hydrostatic pressure test, the tightness of the test bed is tested, whether the sensors on the inner wall and the outer wall of the model well wall 18 are damaged or not is detected, and the initial stress and the assembly stress of the model well wall 18 are eliminated;
b, after the hydrostatic pressure test is finished, removing the upper end cover 1 and the upper sealing plate 8 for drainage, and removing the pressure bearing cylinder 2 after drainage is finished;
step three, manufacturing the pore surrounding rock 19, which comprises the following specific steps:
a, performing lubrication treatment of three oil films and two films on a contact interface of a lower sealing plate 9 and a pore surrounding rock 19, specifically, uniformly coating a layer of molybdenum disulfide lubricating grease 22 on the upper end of the lower sealing plate 9, laying a layer of polytetrafluoroethylene film 23 on the molybdenum disulfide lubricating grease 22, laying a layer of molybdenum disulfide lubricating grease 22 on the polytetrafluoroethylene film 23, and laying a layer of water-permeable cloth 24 on the molybdenum disulfide lubricating grease 22;
b, installing a pore surrounding rock 19 template, pouring the pore surrounding rock 19 in a layered mode, introducing a temperature sensor and a soil pressure meter through a lead hole 32, sealing, and placing the temperature sensor and the soil pressure meter at a pre-buried point; the pore surrounding rock 19 is compacted by a rammer until the design height is reached, one layer is loosely laid after the design height is reached, the test bed is compacted when being assembled, the compaction process ensures the uniformity between layers and the uniformity of different parts of the same layer, meanwhile, the protection of a test element and a transmission line is required in the compaction process, a leveling rod is required for centering and correcting the model well wall 18 in each layer, the model well wall 18 is prevented from deflecting in the compaction process, the reserved height at the top is reasonable, the reserved height is too small, the nut 5 and the screw 6 are difficult to fasten, the sealing of a test space cannot be realized, the reserved height is too large, the axial pressure base plate 7 is separated from the upper end cover 1, and the sealing cannot be realized;
considering the problem that the axial deformation of the pore surrounding rock in the axial loading process causes the separation and sealing failure of the axial pressure base plate 7 and the upper sealing plate 8, firstly, the reserved height is slightly smaller when the pore surrounding rock is poured, and maintenance is carried out under the condition of high axial load; when two exert the load, the confining pressure and the crisscross addition of axial load, exert the confining pressure earlier, under the effect of confining pressure, hole country rock can the axial extension, upwards, the lower extreme warp, the upper and lower sealing plate at both ends can restrict hole country rock and warp, treat to exert the axial load again after the confining pressure is stable, if three under high axial load effect, the separation of axle pressure backing plate and last sealing plate, sealed inefficacy, the uninstallation this moment, open the test bench, tear upper end cover and axle pressure backing plate down promptly, lay the plastic pad of one deck thickness at axle pressure backing plate and last sealing plate contact interface, put axle pressure backing plate on the plastic pad again, be fixed in the upper end cover on the pressure-bearing section of thick bamboo, the test bench of assembling, solve the axial seal inefficacy problem.
c, lubricating an interface of the upper sealing plate 8 in contact with the pore surrounding rock 19 by using three oil films, paving a layer of permeable cloth between the lubricating layer and the top of the pore surrounding rock 19, placing the upper sealing plate 8 on the lubricating layer, placing the axial compression base plate 7 on the upper part of the upper sealing plate 8, and maintaining the pore surrounding rock 19, wherein a maintenance shed needs to be built when the weather is cold to ensure the temperature and humidity for maintaining the pore surrounding rock 19;
and step four, saturating the pore surrounding rock under a pressure state, and specifically comprises the following steps:
a, after the pore surrounding rock 19 is formed, detaching a pore surrounding rock template, cleaning the detached template, brushing oil, uniformly coating an epoxy resin series cementing agent 20 outside the pore surrounding rock 19, after the epoxy resin series cementing agent 20 is hardened, performing smooth and flat treatment on the surface, sleeving a rubber film 21, and sealing and fixing the rubber film through a sealing clamping groove I33 outside a shaft pressing base plate 7, an upper sealing plate 8 and a lower sealing plate 9;
b, sequentially fixing the bottom end of the pressure bearing cylinder 2 to the upper end of the base 3, and fixing the bottom end of the upper end cover 1 to the top end of the pressure bearing cylinder 2 to finish the assembly of the test bed;
c, respectively connecting a servo pressurizing and pressure stabilizing system into a confining pressure pressurizing hole 25 and a lower pore water pressure pressurizing hole 31 through a high-pressure pipeline, connecting an upper pore water pressure pressurizing hole 30 with a vacuum pipeline, a drying tower, a vacuum vessel and a vacuum pump, injecting water through the confining pressure pressurizing hole 25 to apply confining pressure, injecting water through the lower pore water pressure pressurizing hole 31 to apply pore water pressure after the confining pressure is stable, simultaneously opening the upper pore water pressure pressurizing hole 30, vacuumizing through the vacuum pump, saturating the pore surrounding rock 19 under a pressure state, and keeping the pore water pressure to be smaller than the confining pressure all the time in the loading process; after the upper pore water pressure pressurizing hole 30 stably discharges water, closing the upper pore water pressure pressurizing hole 30, and if the pore water pressure in the pore surrounding rock 19 is kept stable, considering that the pore surrounding rock 19 is saturated;
d, unloading the pore water pressure to 0MPa and closing the lower pore water pressure pressurizing hole 31 after the saturation is finished, unloading the confining pressure to 0MPa after the pore water pressure is unloaded, and closing the confining pressure pressurizing hole 25;
fifthly, performing a simulation test on the effect of pore water pressure on the well wall in the unfreezing process of the frozen wall, and specifically performing the following steps:
a, after each pressure is unloaded, connecting the liquid outlet pipe 15 with the top end of the model well wall 18 through a sealing clamping groove II35, leading out a sensor lead on the inner wall of the model well wall 18 through a circular flange joint 16 and sealing; installing a freezing system, respectively connecting the liquid inlet pipe 14 and the liquid outlet pipe 15 with a low-temperature refrigerator, making heat preservation measures and starting freezing;
b, after freezing is finished, opening a confining pressure pressurizing hole 25 and a lower pore water pressure pressurizing hole 31, respectively connecting an upper pore water pressure pressurizing hole 30 and an axial pressure pressurizing hole 28 into a servo pressurizing and pressure stabilizing system, starting stage pressurization, monitoring the change law of a stress field and a temperature field of the model well wall 18 and the pore surrounding rock 19 in the unfreezing process, ensuring that the confining pressure is always greater than the axial pressure and the pore water pressure in the stage pressurization, connecting a copper coil into a cryogenic refrigerator in the unfreezing process, ensuring that the unfreezing speed of the top end and the bottom end of the pore surrounding rock 19 is slower than that of the middle layer, and preventing water from entering a contact interface of the model well wall 18 and the pore surrounding rock 19 along the contact interface of the pore surrounding rock 19 and the upper sealing plate 8 and the lower sealing plate 9 in the unfreezing process and directly acting on the model well wall 18.
Claims (9)
1. A water-rich bedrock section inclined shaft freezing well wall stress simulation test system comprises a high-pressure test bed, a pressure loading system and a data acquisition system, wherein the high-pressure test bed comprises an upper end cover (1), a pressure-bearing cylinder (2) and a base (3), the bottom end of the upper end cover (1) is fixed at the upper end of the pressure-bearing cylinder (2) through a nut (5), a screw rod (6) and a gasket (4), the upper end of the base (3) is fixed at the lower end of the pressure-bearing cylinder (2) through the nut (5), the screw rod (6) and the gasket (4), the water-rich bedrock section inclined shaft freezing well wall stress simulation test system is characterized in that a model well wall (18) is arranged in the pressure-bearing cylinder (2), pore surrounding rocks (19) for tests are arranged on the periphery of the model well wall (18), a lower sealing plate (9) is arranged between the lower end of the pore surrounding rocks (19) and the upper end of the base (3), a shaft pressure backing plate (7) and an, the axial compression backing plate (7) is hermetically arranged at the upper end of the upper sealing plate (8), the axial compression backing plate (7), the upper sealing plate (8) and the lower sealing plate (9) are both central perforated plates, the central holes of the upper sealing plate (8) and the lower sealing plate (9) are equal to the outer diameter of the model well wall (18), and are sealed with the model well wall (18) through axial sealing rings (36), the inner diameter of the central hole of the axial compression backing plate (7) is larger than the inner diameters of the central holes of the upper sealing plate (8) and the lower sealing plate (9), one surface of the upper sealing plate (8) in contact with the axial compression backing plate (7) is provided with a circle of grooves along the circumferential direction, and the end face contact parts between the upper end cover (1), the axial compression backing plate (7), the upper sealing plate (8), the pressure-bearing cylinder (2), the lower sealing plate (9) and the base (3) are;
the pressure loading system comprises a servo pressurizing and pressure stabilizing system and a high-pressure pipeline, a layer of rubber film (21) is tightly wrapped outside the upper sealing plate (8), the pore surrounding rock (19) and the lower sealing plate (9), a surrounding pressure cavity (26) is formed by a cavity between the rubber film (21) and the pressure bearing cylinder (2), and a surrounding pressure hole (25) is formed in the side wall of the pressure bearing cylinder (2); an axial pressurizing cavity (29) is formed by a circumferential groove at the upper end of the upper sealing plate (8) and a cavity between the axial pressing base plate (7), an axial pressurizing hole (28) is formed in the axial pressing base plate (7), an upper pore water pressure pressurizing hole (30) is formed in the upper sealing plate (8), a lower pore water pressure pressurizing hole (31) is formed in the lower sealing plate (9), the servo pressurizing and pressure stabilizing system is respectively connected with the confining pressure pressurizing hole (25) through a high-pressure pipeline to inject water into the confining pressure pressurizing cavity (26) to apply confining pressure, is connected with the axial pressurizing hole (28) to inject water into the axial pressurizing cavity to apply axial load, and is connected with the upper pore water pressure pressurizing hole (30) and the lower pore water pressure pressurizing hole (31) to load pore water pressure into the pore surrounding rock (19);
the data acquisition system comprises a sensor group, a data acquisition instrument and a computer, wherein the sensor group is arranged in a model well wall (18) and a pore surrounding rock (19), a lead of each sensor in the sensor group is connected with the data acquisition instrument, and the data acquisition instrument is connected with the computer;
a lubricating layer of three oil films and two films is arranged at the contact interface of the pore surrounding rock and the upper sealing plate and the lower sealing plate, and the lubricating layer comprises a layer of molybdenum disulfide lubricating grease (22), a layer of polytetrafluoroethylene film (23), a layer of molybdenum disulfide lubricating grease (22), a layer of polytetrafluoroethylene film (23) and a layer of molybdenum disulfide lubricating grease (22), which are uniformly laid in sequence from the lower sealing plate to the surrounding rock interface or from the upper sealing plate to the surrounding rock interface;
one layer of permeable cloth (24) is laid between the lubricating layer and the pore surrounding rock interface, and pore water pressure holes in the upper sealing plate (8) and the lower sealing plate (9) penetrate through the lubricating layer and extend into the permeable cloth, so that water is ensured to be injected from the pore water pressure pressurizing holes, and the water is rapidly diffused in the permeable cloth and is uniformly transferred to enter the pore surrounding rock.
2. The water-rich bedrock section inclined shaft freezing well wall stress simulation test system according to claim 1, characterized in that the test system further comprises a freezing system, the freezing system comprises a cryogenic refrigerator and a freezing liquid circulation channel, the upper end of the model well wall (18) is connected with a liquid outlet pipe (15), the lower end of the model well wall is connected with a liquid inlet pipe (14), the freezing liquid circulation channel is formed by an inner cavity among the model well wall (18), the liquid inlet pipe (14) and the liquid outlet pipe (15), and an inlet of the liquid inlet pipe (14) and an outlet of the liquid outlet pipe (15) are respectively connected with the cryogenic refrigerator.
3. The system for simulating the stress of the freezing well wall of the inclined shaft at the water-rich bedrock section according to the claim 2, wherein the sensor group comprises a plurality of strain sensors and a plurality of temperature sensors which are adhered to the inner wall and the outer wall of the model well wall (18), and a temperature sensor and a soil pressure gauge which are buried in pore surrounding rock (19), wherein a lead of the temperature sensor and a lead of the soil pressure gauge in the pore surrounding rock (19) and a lead of the strain sensor and a lead of the temperature sensor which are adhered to the outer wall of the model well wall are respectively led out to the data acquisition instrument through lead holes (32) formed in the lower sealing plate (9); the lead of the strain sensor and the lead of the temperature sensor which are adhered to the inner wall of the model well wall (18) are respectively led out to a data acquisition instrument through a circular flange joint (16) arranged on the outer wall of the liquid outlet pipe (15).
4. The system for simulating the freezing well wall stress of the inclined shaft at the water-rich bedrock section according to the claim 3, characterized in that a lead groove (34) which has extremely small width and depth and is communicated with the top end of the model well wall is axially arranged at the position of the outer wall of the model well wall (18) close to the contact interface of the upper sealing plate and the pore surrounding rock.
5. The system for simulating the stress of the freezing well wall of the inclined shaft at the water-rich bedrock section according to claim 4, wherein a layer of epoxy resin series cementing agent (20) or high-penetration road asphalt is uniformly coated on the contact interface between the outer surface of the pore surrounding rock (19) and the rubber film (21); in order to prevent the epoxy resin series cementing agent (20) or the asphalt from being stuck with the rubber film (21), a plastic film is wrapped on the outer surface of the asphalt layer.
6. The water-rich bedrock section inclined shaft freezing well wall stress simulation test system according to claim 5, characterized in that the liquid inlet pipe (14) and the liquid outlet pipe (15) are made of low temperature resistant flexible materials and fixed through a sealing clamping groove II (35) on the model well wall.
7. The water-rich bedrock section inclined shaft freezing well wall stress simulation test system according to any one of claims 1 to 6, characterized in that a plurality of circles of copper coil pipes (17) are arranged on the upper end surface of the upper sealing plate (8) and close to the model well wall (18) and on the lower end surface of the lower sealing plate (9) and close to the model well wall (18) along the circumferential direction, and in the process of unfreezing the freezing well wall, the copper coil pipes (17) are connected with a cryogenic refrigerator.
8. The water-rich bedrock section inclined shaft freezing well wall stress simulation test system according to claim 7, characterized in that the outer diameter end faces of the axial compression backing plate (7), the upper sealing plate (8) and the lower sealing plate (9) are respectively provided with a sealing clamping groove I (33); the outer side of the whole stress simulation test bed is wrapped with a heat insulation cotton material for heat insulation treatment.
9. A simulation test method for the stress of a freezing well wall of an inclined well at a water-rich bedrock section is characterized by comprising the following steps,
firstly, assembling a simulation test bed, and specifically comprising the following steps:
a, manufacturing a model well wall (18), and then sticking a plurality of strain sensors and temperature sensors on the inner wall and the outer wall of the model well wall (18) and protecting;
b, fixing a copper coil (17) at a preset position of a lower sealing plate (9), fixing the lower sealing plate (9) on a base (3) through a tensioning screw (10) and a tensioning flange (11), and enabling the central line of the lower sealing plate (9) to coincide with the base (3);
c, connecting the liquid inlet pipe (14) with the bottom end of the model well wall (18) through a sealing clamping groove II (35), inserting the bottom end of the model well wall (18) into the lower sealing plate (9), sealing the bottom end of the model well wall and the lower sealing plate through an axial sealing ring (36), leading the liquid inlet pipe out from the bottom end of the base (3), ensuring the model well wall (18) to be centered and vertical through a horizontal ruler and a verticality determinator, and recording the distance between the model well wall (18) and the outer diameter boundary line of the lower sealing plate (9) in each direction through the horizontal ruler;
d, fixing the lower end of the pressure bearing cylinder (2) at the upper end of the base (3) through a nut (5), a screw rod (6) and a gasket (4), and sealing the contact part between the two through a radial sealing ring (37);
e, enabling an upper sealing plate (8) to penetrate through a model well wall (18), then hoisting an upper end cover (1), fixing the lower end of the upper end cover (1) at the upper end of a pressure bearing cylinder (2) through a nut (5), a screw rod (6) and a gasket (4), and fixing the upper sealing plate on the upper end cover (1) through a tensioning screw rod (10), a tensioning flange (11), a hexagon nut (12) and a plain washer (13) to finish the assembly of the test bed;
and step two, carrying out hydrostatic pressure test, and specifically comprising the following steps:
a, connecting each sensor into a data acquisition instrument, connecting confining pressure pressurizing holes (25) into a servo pressurizing and pressure stabilizing system through a high-pressure pipeline, closing the rest pressurizing holes and injecting water into a test space; through hydrostatic pressure test, the tightness of the test bed is tested, whether sensors on the inner wall and the outer wall of the model well wall (18) are damaged or not is detected, and the initial stress and the assembly stress of the model well wall (18) are eliminated;
b, after the hydrostatic pressure test is finished, removing the upper end cover (1) and the upper sealing plate (8) for drainage, and removing the pressure bearing cylinder (2) after drainage is finished;
thirdly, manufacturing the pore surrounding rock (19), which comprises the following specific steps:
a, performing lubrication treatment of three oil films on a contact interface of a lower sealing plate (9) and pore surrounding rock (19), specifically, uniformly coating a layer of molybdenum disulfide lubricating grease (22) on the upper end of the lower sealing plate (9), laying a layer of polytetrafluoroethylene film (23) on the molybdenum disulfide lubricating grease (22), laying a layer of molybdenum disulfide lubricating grease (22) on the polytetrafluoroethylene film (23), and laying a layer of permeable cloth (24) on the molybdenum disulfide lubricating grease (22);
b, installing a pore surrounding rock (19) template, pouring the pore surrounding rock (19) in a layered mode, introducing a temperature sensor and a soil pressure meter through a lead hole (32), sealing, and placing the temperature sensor and the soil pressure meter at an embedded point; the pore surrounding rock (19) is tamped by a tamping hammer until reaching the design height, one layer is loosely paved after reaching the design height, the test bed is compacted when being assembled, the compaction process ensures the uniformity between layers and the uniformity of different parts of the same layer, meanwhile, the protection of a test element and a transmission line is required to be paid attention to in the tamping process, a leveling rod is required to perform centering correction on the model well wall (18) in each layer, the model well wall (18) is prevented from deflecting in the tamping process, the reserved height at the top is reasonable, the reserved height is too small, the nut (5) and the screw (6) are difficult to fasten, the sealing of a test space cannot be realized, the reserved height is too large, the axial pressure base plate (7) is separated from the upper end cover (1), and the sealing cannot be realized;
c, lubricating an interface of the upper sealing plate (8) in contact with the pore surrounding rock (19) by using three oil films, paving a layer of permeable cloth between the lubricating layer and the top of the pore surrounding rock (19), placing the upper sealing plate (8) on the lubricating layer, placing the axial compression base plate (7) on the upper part of the upper sealing plate (8), and maintaining the pore surrounding rock (19), wherein a maintenance shed needs to be built when the weather is cold, so that the temperature and humidity for maintaining the pore surrounding rock (19) are ensured;
and step four, saturating the pore surrounding rock under a pressure state, and specifically comprises the following steps:
a, after pore surrounding rock (19) is formed, detaching a pore surrounding rock template, cleaning the detached template with oil, uniformly coating an epoxy resin series cementing agent (20) outside the pore surrounding rock (19), after the epoxy resin series cementing agent (20) is hardened, performing smooth and flat treatment on the surface, wrapping a layer of plastic film, sleeving a rubber film (21), and sealing and fixing the plastic film through a sealing clamping groove I (33) outside a shaft pressing base plate (7), an upper sealing plate (8) and a lower sealing plate (9);
b, sequentially fixing the bottom end of the pressure bearing cylinder (2) to the upper end of the base (3), and fixing the bottom end of the upper end cover (1) to the top end of the pressure bearing cylinder (2) to complete the assembly of the test bed;
c, respectively connecting a servo pressurizing and pressure stabilizing system into a confining pressure pressurizing hole (25) and a lower pore water pressure pressurizing hole (31) through a high-pressure pipeline, connecting an upper pore water pressure pressurizing hole (30) with a vacuum pipeline, a drying tower, a vacuum vessel and a vacuum pump, injecting water through the confining pressure pressurizing hole (25) to apply confining pressure, injecting water through the lower pore water pressure pressurizing hole (31) to apply pore water pressure after the confining pressure is stable, simultaneously opening the upper pore water pressure pressurizing hole (30), vacuumizing through the vacuum pump, saturating the pore surrounding rock (19) under a pressure state, and keeping the pore water pressure to be smaller than the confining pressure all the time in a loading process; after the upper pore water pressure pressurizing hole (30) is stable to discharge water, closing the upper pore water pressure pressurizing hole (30), and if the pore water pressure in the pore surrounding rock (19) is stable, considering that the pore surrounding rock (19) is saturated;
d, unloading the pore water pressure to 0MPa and closing the lower pore water pressure pressurizing hole (31) after the saturation is finished, unloading the confining pressure to 0MPa and closing the confining pressure pressurizing hole (25) after the pore water pressure is unloaded;
fifthly, performing a simulation test on the effect of pore water pressure on the well wall in the unfreezing process of the frozen wall, and specifically performing the following steps:
a, after each pressure is unloaded, a liquid outlet pipe (15) is connected with the top end of a model well wall (18) through a sealing clamping groove II (35), and a sensor lead on the inner wall of the model well wall (18) is led out through a circular flange joint (16) and sealed; a freezing system is installed, a liquid inlet pipe (14) and a liquid outlet pipe (15) are respectively connected with a low-temperature refrigerator, heat preservation measures are made, and freezing is started;
b, after freezing is finished, opening a confining pressure pressurizing hole (25) and a lower pore water pressure pressurizing hole (31), respectively connecting an upper pore water pressure pressurizing hole (30) and an axial pressure pressurizing hole (28) into a servo pressurizing and pressure stabilizing system, starting stage pressurization, and monitoring the change rule of the stress field and the temperature field of the model well wall (18) and the pore surrounding rock (19) in the unfreezing process; the confining pressure is guaranteed to be always larger than the axial pressure and the pore water pressure when the grading pressurization is carried out, in the unfreezing process, the copper coil pipe is connected into the low-temperature refrigerator, the unfreezing speed of the top end and the bottom end of the pore surrounding rock (19) is guaranteed to be slower than that of the middle layer, water is prevented from entering the contact interface of the model well wall (18) and the pore surrounding rock (19) along the contact interface of the pore surrounding rock (19) and the upper sealing plate (8) and the lower sealing plate (9) when the unfreezing is carried out, and the water is directly applied to the model well wall (18).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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| CN110441147B (en) * | 2019-08-30 | 2024-06-07 | 湖南科技大学 | Physical simulation device and simulation method for circumferential compression of coal mine vertical shaft wall |
| CN111442979B (en) * | 2020-03-13 | 2022-09-23 | 湖南大学 | Model test system for static expansive force induced cracking soft rock |
| CN111878580A (en) * | 2020-06-16 | 2020-11-03 | 江苏建筑职业技术学院 | Sealing system of test device for simulating high-pore water pressure action on special-shaped structure |
| CN111735846B (en) * | 2020-07-16 | 2023-03-24 | 安徽理工大学 | Device and method for testing heat preservation and cold insulation performance of material under confining pressure |
| CN113565515B (en) * | 2021-07-24 | 2024-03-15 | 郑州大学 | Device and method for testing pore water pressure in freezing method construction of subway communication channel on site |
| CN117388440B (en) * | 2023-10-23 | 2024-07-12 | 中国矿业大学 | Device and method for grouting process test and effect detection between double-layer well walls |
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