CN109932248B - Test system for simulating chamber face excavation transient unloading under different ground stress conditions - Google Patents
Test system for simulating chamber face excavation transient unloading under different ground stress conditions Download PDFInfo
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- CN109932248B CN109932248B CN201910101784.XA CN201910101784A CN109932248B CN 109932248 B CN109932248 B CN 109932248B CN 201910101784 A CN201910101784 A CN 201910101784A CN 109932248 B CN109932248 B CN 109932248B
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Abstract
The invention relates to a test system for simulating chamber face excavation transient unloading under different stress conditions; the method can simulate the excavation transient unloading process of the tunnel face of the underground chamber, complete the transient unloading of the surrounding rock with different excavation surface shapes under different stress conditions and different unloading rates, and simultaneously record the whole process of the whole-field displacement change of the surrounding rock of the underground chamber. The test system comprises an in-situ stress simulation device, a transient unloading device and a surrounding rock full-field displacement monitoring device; the in-situ stress simulation device consists of an earth stress loading device and a chamber surrounding rock model, wherein four loading surfaces in the chamber surrounding rock model are in direct contact with four hydraulic heads of the earth stress loading device, and the earth stress loading device and the chamber surrounding rock model are matched for use and are placed on the same plane vertical to the horizontal plane; respectively placing a transient unloading device and a surrounding rock full-field displacement monitoring device in the front and back directions of the plane; the test can indirectly solve the problem that the displacement of surrounding rock can not be measured at the moment of excavation unloading by a drilling and blasting method in actual engineering.
Description
Technical Field
The invention particularly relates to an underground chamber excavation transient unloading simulation test system based on rock dynamics, and belongs to the field of geotechnical engineering model test devices.
Background
Limited by topography, a large number of engineering buildings in China are deeply buried in underground surrounding rocks, the surrounding rocks have higher ground stress and complex geological structures, and sudden unloading in the excavation process can often induce high-degree nonlinear behaviors such as large extrusion deformation, rheology, zonal fracture and the like of the surrounding rocks, so that engineering geological disasters such as instability and collapse, cracking, rock burst and the like of the surrounding rocks are caused, and a severe challenge is brought to the safety of engineering. The deep engineering construction in China mainly adopts a drilling and blasting method for construction, and an excavation surface is suddenly unloaded under the action of blasting vibration. On one hand, the transient excavation process is easy to cause stress dynamic unloading of surrounding rocks, so that cracks in the surrounding pressure structure are initiated, expanded and communicated, and a surrounding rock damage area is formed; on the other hand, due to the reasons of large buried depth of the rock mass, high ground stress, complex geological structure, frequent engineering disturbance and the like, the internal micro-fracture of the rock mass in the damaged area can continue to expand and penetrate even cause instability damage under the action of subsequent high stress and dynamic and static loads such as blasting operation, mine earthquake or fault activation and the like, so that the overall structure is subjected to catastrophe instability, and strong rock engineering dynamic disasters such as rock explosion and the like are induced.
At present, a plurality of scholars in China study the excavation stability of underground chambers in a numerical simulation and theoretical calculation mode, but cannot visually know the transient displacement and deformation conditions of chamber surrounding rocks under the condition of sudden unloading of an excavation surface, so that an indoor physical model test needs to be carried out to study the mechanical behavior of the chamber surrounding rocks under the action of transient unloading of excavation. The existing model test of underground chambers mainly considers the stability after forming the chambers, but cannot reflect the influence of unloading process and unloading conditions on surrounding rocks of the chambers. The invention relates to an underground chamber structure surface excavation transient unloading loosening simulation test system invented by Wuhan theory university, which only considers the unloading of a rock mass structure surface and cannot reflect the stability of the whole chamber globally and intuitively. And unloading control is realized through electromagnetism, but electromagnetism needs a period of time to charge before reaching the target magnetic force, so the transient unloading process cannot be well reflected.
Disclosure of Invention
Aiming at the complexity and importance of the transient unloading of the underground chamber excavation, the invention provides a test system capable of simulating the transient unloading of the underground chamber excavation face under different stress conditions. The system can simulate the excavation transient unloading process of the tunnel face of the underground chamber, can complete the transient unloading of the surrounding rocks with different excavation surface shapes under different stress conditions and different unloading rates, and can record the whole process of the whole displacement change of the surrounding rocks of the underground chamber at the same time. The test can indirectly solve the problem that the displacement of surrounding rock at the moment of excavation unloading by a drilling and blasting method in actual engineering cannot be measured.
The invention provides a test system capable of realizing excavation transient unloading of underground chamber faces under different stress conditions, which aims to realize a test system for testing full-section displacement of underground chamber faces with different stress and different shapes of excavation faces under an excavation transient unloading working condition.
The technical scheme of the invention is as follows:
a test system for simulating the transient unloading of chamber face excavation under different stress conditions comprises an in-situ stress simulation device, a transient unloading device and a surrounding rock full-field displacement monitoring device; the in-situ stress simulation device consists of an earth stress loading device and a chamber surrounding rock model, the chamber surrounding rock model clamps four loading surfaces of the surrounding rock model by using the earth stress loading device and applies loads, and the chamber surrounding rock model is acted by plane stress; the ground stress loading device and the chamber surrounding rock model are matched for use and are placed on the same plane vertical to the horizontal plane; and the transient unloading device and the surrounding rock full-field displacement monitoring device are respectively arranged in the front direction and the rear direction of the plane.
The chamber surrounding rock model is a polygonal plate-shaped rock material, and a hole consistent with the plug body is formed in the center of the chamber surrounding rock model; the ground stress loading device is used for applying loads to four loading surfaces of the underground chamber surrounding rock model and simulating a real ground stress environment of the underground chamber surrounding rock under a test chamber condition; the plug body in the transient unloading device keeps sliding fit with the hole of the surrounding rock model of the underground chamber, the plug body can fill the hole and work with the surrounding rock model of the underground chamber when the ground stress loading device applies ground stress, the plug body bears the ground stress transmitted from the hole of the surrounding rock model of the underground chamber, and the real ground stress environment of the in-situ surrounding rock before the underground chamber is excavated is simulated; then, high-pressure gas in the gas tank is controlled to enter the launching sleeve through a valve, the high-pressure gas drives an impact block in the launching sleeve to move in the direction far away from the plug body and impact a flange, and the flange is connected with the plug body through an unloading rod, so that the plug body is quickly pulled out of a hole of the chamber surrounding rock model to simulate the sudden unloading process of in-situ surrounding rock; the impact speed of the impact block is controlled by changing the pressure of high-pressure gas in the gas tank, so that the plug body is pulled out of the hole at different speeds, and different unloading rates in actual engineering are simulated; the surrounding rock full-field displacement monitoring system is used for monitoring the change information of the displacement field of a plane of a free surface of the surrounding rock model of the underground chamber after transient unloading so as to accurately obtain the deformation response relation of the surrounding rock of the underground chamber to the sudden unloading action under the condition of a test chamber.
In the test system, the stress loading device is four hydraulic heads, the four hydraulic heads apply loads to four loading surfaces of the underground chamber surrounding rock model to simulate ground stress, and the stress loading path is accurately controlled, is connected with the data analysis device and is matched with the data analysis device and used for measuring and recording the stress of the four loading surfaces of the model; and the other two free surfaces of the chamber surrounding rock model are respectively provided with a transient unloading device and a surrounding rock full-field displacement monitoring device.
In the test system, the areas of the four loading surfaces of the underground chamber surrounding rock model are slightly smaller than the areas of the contact surfaces of the ground stress loading devices, so that the model material can be completely loaded during loading.
The invention relates to a transient unloading device for simulating excavation of a tunnel face of a chamber under different stress conditions, which comprises a test platform, a baffle and a supporting device, wherein the baffle is connected with the supporting device through a bolt, and the baffle is connected with the supporting device and then installed at one end of the test platform, which is close to a surrounding rock model of the chamber; the baffle and the supporting device are provided with round holes with the same diameter as that of the unloading rod for the unloading rod to pass through; a support is arranged on the test platform; the function of the support is to support the launching sleeve and the unloading rod; the closed end of the launching sleeve is provided with a round hole with the diameter same as that of the unloading rod for the unloading rod to pass through, and the round hole is sealed to prevent air leakage; a valve connected with a gas tank is arranged on the launching sleeve, the gas tank is connected with an air compressor, an impact block is arranged in the sleeve, and a round hole with the same diameter as that of the unloading rod is arranged in the middle of the impact block and is used for the unloading rod to pass through; the unloading rod is connected with the plug body at one end close to the chamber surrounding rock model, and is fixed with the flange at the other end through threads; and a compressive strain gauge is adhered to the unloading rod and is connected with a dynamic strain gauge which is connected with an oscilloscope.
The test bed is provided with a slide way for adjusting the position of the support.
The unloading rod penetrates through the impact block and the sleeve, and an inner circle part at one end of the unloading rod is provided with a round hole with threads and fixed with the plug body; the other end of the unloading rod is fixed with the flange through threads.
The baffle is fixed on the test platform through a connecting clamp and is in contact with the surrounding rock model of the underground chamber; the center of the baffle plate is provided with a round hole with the same diameter as the unloading rod for the unloading rod and the plug body to pass through.
The supporting device is designed to be in a straw hat shape, one end of the supporting device is fixed on the baffle through a bolt, and a round hole with the same diameter as the unloading rod is reserved at one end of the supporting device and is used for the unloading rod to pass through for keeping the unloading rod horizontal.
One end of the plug body is processed into the shape of a tunnel face of the chamber model, the end is designed into a cone with the gradient of 1 degree, and the outer part of the other end is carved with threads to be connected with the end of the unloading rod.
The concrete description is as follows:
a test system for simulating the transient unloading of chamber face excavation under different ground stress conditions is characterized by comprising an in-situ stress simulation device II, a transient unloading device III and a surrounding rock full-field displacement monitoring device I (shown in figure 1). The in-situ stress simulation device II consists of an earth stress loading device 1 and a chamber surrounding rock model 2, wherein the earth stress loading device 1 comprises four hydraulic heads controlled by a control system. The device has the function of applying plane stress to the underground chamber surrounding rock model 2 to simulate the real ground stress environment of the underground chamber; the underground chamber surrounding rock model 2 is made of polygonal rock material plates, and a hole is formed in the center of the underground chamber surrounding rock model and used for simulating underground chamber surrounding rocks. The surrounding rock full-field displacement monitoring device I comprises a high-speed camera shooting acquisition system and is used for monitoring the displacement field change information of the free surface (vertical to the ground stress applying plane) of the surrounding rock model of the underground chamber after transient unloading. The plug body 3 in the transient unloading device III is consistent with the size of the hole in the chamber surrounding rock model 2 and is matched with the hole, and the plug body 3 can be pulled out of the hole instantly during testing. The device has the function of simulating sudden unloading in the underground chamber excavation construction process.
The transient unloading device III is characterized in that a baffle 5, a supporting device 6, an unloading rod 4, a plug body 3, a support 18, a launching sleeve 8, an impact block 7 and a flange 9 are sequentially arranged on a test platform 17. Wherein, the supporting device 6 and the baffle 5 are fixed into a whole through a bolt 16 and then are arranged on a test platform 17. The plug body 3 and the flange 9 are respectively connected with two ends of the unloading rod 4, wherein the inner part of the plug body 3 and the outer side of the unloading rod 4 are provided with threads which are matched with each other, the plug body 3 and the unloading rod 4 are connected and fixed through the threads, and the plug body 3 is close to one end of the chamber surrounding rock model 2; the flange 9 is fixedly connected with the unloading rod 4 through a bolt 16, and the flange 9 is positioned at the other end of the unloading rod 4. Between the plug body 3 and the flange 9 there are arranged a launching sleeve 8 and an impact block 7, through which the unloading rod 4 passes and is free to move axially. A support 18 fixed on the test platform 17 provides support for the launching sleeve 8 and the unloading rod 4.
The launching sleeve 8 is internally provided with an impact block 7, one end of the launching sleeve 8 is closed, and the other end of the launching sleeve 8 is open, and the impact block 7 is dumbbell-shaped, and the outer diameter of the impact block is slightly smaller than the inner diameter of the launching sleeve 8, so that the impact block can freely slide in the launching sleeve 8. Round holes with the same diameter as that of the unloading rod 4 are formed in the center positions of the impact block 7 and the closed end of the launching sleeve 8, the unloading rod 4 can penetrate through the round holes, a sealing device is arranged between the round holes in the closed end of the launching sleeve 8 and the unloading rod 4, the sealing device is used for sealing a gap between the round holes in the closed end of the launching sleeve 8 and the unloading rod 4 to enable the gap to be airtight, and meanwhile, the movement of the unloading rod 4 along the axial direction of the unloading rod 4 is not limited; a valve 13 connected to a gas tank 14 is connected to the launch sleeve 8, and the gas tank 14 is connected to an air compressor 15 and can provide a stable pressure gas source for the launch sleeve 8. The above-mentioned parts are all supported by means of a support 18, the function of the support 18 being to support the above-mentioned parts so that they work coaxially. The support 18 is placed on the test platform 17 to ensure that the components are placed stably.
One end of the test platform 17 is provided with a supporting device 6, and the center of the supporting device 6 is also provided with a hole with the same shape and size as the plug body 3 so as to ensure that the plug body 3 and the unloading rod 4 can freely pass through the supporting device 6 to move. The supporting device 6 is fixedly connected with the baffle 5 through a bolt 16, and the same hole as the center of the supporting device 6 is also arranged at the center of the baffle 5 for the free movement of the plug body 3 and the unloading rod 4. A compressive strain gauge 10 is adhered to the unloading rod 4, the compressive strain gauge 10 is connected with a dynamic strain gauge 11, the dynamic strain gauge 11 is connected with an oscilloscope 12, and the compressive strain gauge, the dynamic strain gauge and the oscilloscope are used together to collect stress waves generated by impact on the unloading rod 4. Three views of the transient unloading apparatus are shown in fig. 3-5.
The supporting device 6 is designed to be in a straw hat shape, one end of the supporting device is fixed on the baffle 5 through a bolt, and a round hole with the same diameter as that of the unloading rod 4 is reserved at one end of the supporting device for the unloading rod 4 to pass through and is used for keeping the unloading rod 4 horizontal. The baffle 5 is fixed on the test platform 17 through a connecting clamp, and the baffle 5 is in contact with the surrounding rock model 2 of the underground chamber; a round hole with the same diameter as the unloading rod 4 is reserved in the center of the baffle 5 to ensure that the unloading rod 4 and the plug body 3 can freely pass through. The supporting device 6 and the baffle 5 can ensure that when the plug body 3 is pulled out of the central hole of the underground chamber surrounding rock model 2 by the unloading rod 4, the model is kept stable and is not damaged by pulling, thereby influencing the experimental result.
The test platform 17 is provided with a slide way for adjusting the position of the support 18.
One end of the plug body 3 is processed into the shape of a tunnel model palm surface and can be circular or horseshoe-shaped, the end is designed into a cone with the gradient of 1 degree, and the outer part of the other end is carved with threads to be connected with the end of the unloading rod 4. Fig. 6 is a sectional view of the connection of the chamber surrounding rock model 2 and the transient unloading device iii.
The device I for monitoring the displacement of the whole surrounding rock field comprises a high-speed camera, and the device I and the computer are connected and used for measuring, recording and storing the displacement change of the whole surrounding rock field in the whole process. The high-speed camera shooting acquisition system can be connected with the dynamic strain gauge 11, and triggers the high-speed camera to measure and record the redistribution condition of the stress of the surrounding rock at the moment of unloading through a trigger signal.
The four hydraulic heads of the ground stress loading device 1 can apply loads to the non-free boundaries (a, b, c and d) (shown in figure 7) of the underground chamber surrounding rock model 2 to simulate in-situ ground stress, and a control system can realize accurate control on a loading stress path. The device is connected with a data analysis device and is used for measuring and recording the stress of four loading surfaces of the model.
The underground chamber surrounding rock model 2 clamps four loading surfaces (namely non-free boundaries a, b, c and d, shown in figure 7) of the model by using four hydraulic heads of the ground stress loading device 1 and applies load, and the underground chamber surrounding rock model 2 is acted by plane stress; and a transient unloading device III and a surrounding rock full-field displacement monitoring device I are respectively arranged in the directions of the other two free surfaces (A, B, shown in figure 7) of the underground chamber surrounding rock model 2.
The areas of the non-free boundaries (a, b, c and d) of the chamber surrounding rock model 2 are slightly smaller than the contact surface area of the ground stress loading device 1, so that the model material can be completely loaded during loading.
Preferably, the unloading bar 4 is made of nickel-chromium steel material, and has a length of 600mm and a diameter of 20 mm.
Preferably, the baffle 5 has a thickness of 10mm and a length and a width of 150mm, respectively.
Preferably, the chamber surrounding rock model 2 has a square boundary with a length variable of 300mm to 500mm, isosceles triangles with a side length of 20mm to 30mm are cut at four corners respectively, the diameter of a central circular hole is 10mm in the direction close to the monitoring system, the slope of the end close to the unloading device is increased to 1 degree, and the end is attached to the surface of an unloading rod, wherein the shape of the chamber can be changed according to the actual engineering condition.
Preferably, the working pressure of the gas tank 14 is 0.5-20 MPa.
Preferably, the strain gauge 10 is a precision standard 1000 Ω resistor, the attaching position is at 1/3 on the end of the unloading rod near the plug, and the strain gauge test adopts the wheatstone bridge test principle.
All the devices are installed and configured according to the method, four non-free boundaries in the underground chamber surrounding rock model 2 are in direct contact with four hydraulic heads of the ground stress loading device 1, and the four non-free boundaries and the four hydraulic heads are matched for use and are placed on the same plane vertical to the ground. Respectively placing a transient unloading device III and a surrounding rock full-field displacement monitoring device I in the front direction and the rear direction (A, B) of the plane;
the chamber surrounding rock model is a polygonal rock material plate with a hole in the center; the ground stress loading device is used for applying load to the non-free boundary of the underground chamber surrounding rock model and simulating the real ground stress environment of the underground chamber surrounding rock under the condition of a test chamber; the plug body in the transient unloading device keeps sliding fit with the hole of the surrounding rock model of the chamber, the plug body can fill the hole and cooperate with the surrounding rock model of the chamber when the ground stress loading device applies the ground stress, and the plug body bears the ground stress transmitted from the hole of the surrounding rock model of the chamber, therebySimulating a real ground stress environment of in-situ surrounding rock before underground chamber excavation; then, high-pressure gas in the gas tank is controlled by a valve to enter the launching sleeve, the high-pressure gas drives the impact block in the launching sleeve to move towards the direction far away from the plug body and impact the flange to generate impact and carrier epsilon i (e) Loading wave epsilon i The plug body is spread along the unloading rod to the plug body direction, the flange is connected with the plug body through the unloading rod, the plug body is quickly pulled out from a hole of the chamber surrounding rock model to simulate the sudden unloading process of the in-situ surrounding rock, and a loading wave epsilon spread along the unloading rod i Reflecting at the plug body to produce a reflected wave epsilon r (f) As shown in fig. 2. The impact speed of the impact block is controlled by changing the high-pressure gas pressure of the gas tank, so that the plug body is pulled out of the hole at different speeds, and different unloading rates in the actual engineering are simulated; the surrounding rock full-field displacement monitoring system is used for monitoring the displacement field change information of a plane of a free surface (vertical to a ground stress applying plane) of the surrounding rock model of the underground chamber after transient unloading so as to accurately obtain the deformation response relation of the surrounding rock of the underground chamber to the sudden unloading action under the condition of a test chamber.
The invention provides a test device capable of simulating excavation transient unloading of tunnel surrounding rocks under different stress conditions, which mainly comprises an in-situ stress simulation device, a transient unloading device and a surrounding rock full-field displacement monitoring device; the ground stress loading device in the in-situ stress simulation device is used for loading the surrounding rock model of the underground chamber; the transient unloading device is used for suddenly unloading the surrounding rock model of the underground chamber and comprises an unloading rod, a plug body, a launching sleeve, an impact block, a flange, a baffle plate, a support, a test platform, an oscilloscope and a dynamic strain gauge. The whole transient unloading device is vertical to the surrounding rock model of the chamber and is consistent with the excavation direction of the chamber; the plug body is used for replacing a rock mass to be unloaded on the face, and is connected with the unloading rod through threads. Signals of the added carrier wave and the reflected wave in the unloading rod changing along with time are respectively recorded through a dynamic strain gauge and an oscilloscope, so that the transient unloading rate of the tunnel face is calculated. In the invention, the chamber surrounding rock model can apply external load to the chamber surrounding rock model through the ground stress loading device so as to simulate the initial ground stress environment of the underground chamber in the actual engineering; simulating chamber face transient unloading at different unloading rates by changing the emission speed of the impact block; and the properties of the plug body can be changed to simulate the transient unloading mechanics and deformation behavior of the surrounding rocks of the chambers with different shapes.
Drawings
FIG. 1 is a schematic diagram of a test system according to the present invention.
Fig. 2 is a diagram of the wave system generated by the unloading rod when the impact block collides with the flange.
Fig. 3 is a front view of the transient unloading apparatus of the present invention.
Fig. 4 is a top view of the transient unloading apparatus of the present invention.
Fig. 5 is a side view of the transient unloading apparatus of the present invention.
Fig. 6 is a cross-sectional view of the connection of the chamber surrounding rock model and the transient unloading device.
Fig. 7 is a front view and a side view of a model of the surrounding rock of the chamber.
FIG. 8 is a graph of the unloading force duration during transient unloading of the test device.
Wherein: the device comprises a ground stress loading device 1, a chamber surrounding rock model 2, a plug body (tunnel face rock mass) 3, an unloading rod 4, a baffle plate 5, a supporting device 6, an impact block 7, a launching sleeve 8, a flange 9, a compressive strain gauge 10, a dynamic strain gauge 11, an oscilloscope 12, a valve 13, a gas tank 14, an air compressor 15, a bolt 16, a test platform 17, an impact plus epsilon carrier e i F is the reflected wave ε r . I is a surrounding rock full-field displacement monitoring device, II is an in-situ stress simulation device, and III is a transient unloading device.
Detailed Description
The invention is described in further detail below with reference to the following figures and specific examples:
as shown in fig. 1, the test system for simulating chamber face excavation transient unloading under different stress conditions mainly comprises three parts: the system comprises an in-situ stress simulation device II, a transient unloading device III and a surrounding rock full-field displacement monitoring device I; in the test system, the underground chamber surrounding rock model 2 utilizes the ground stress loading device 1 in the in-situ stress simulation device II to clamp four loading surfaces (a, b, c and d) of the underground chamber surrounding rock model and apply loads, so that the underground chamber surrounding rock model 2 is under the action of plane stress. The holes in the underground chamber surrounding rock model 2 are filled with the plugs 3 in the transient unloading device III, and the ground stress is transmitted to the plugs 3 through the holes; after loading, the plug body 3 and the chamber surrounding rock model 2 work cooperatively to share the ground stress; the other two free surfaces (A, B) of the underground chamber surrounding rock model are respectively provided with a transient unloading device III and a surrounding rock full-field displacement monitoring device I; the chamber surrounding rock model is a polygonal rock material plate, and a hole with the size consistent with that of the plug body 3 is formed in the center of the chamber surrounding rock model and can be in sliding fit with the plug body.
The transient unloading device III comprises a plug body 3, a baffle plate 5, a supporting device 6, an unloading rod 4, a support 18, a launching sleeve 8, an impact block 7 and a flange 9. Wherein, the supporting device 6 and the baffle 5 are fixed into a whole through a bolt 16 and then are arranged on a test platform 17. The plug body 3 and the flange 9 are respectively connected with two ends of the unloading rod 4, wherein the inner part of the plug body 3 and the outer side of the unloading rod 4 are provided with threads which are matched with each other, the plug body 3 and the unloading rod 4 are connected and fixed through the threads, and the plug body 3 is close to one end of the chamber surrounding rock model 2; the flange 9 is fixedly connected with the unloading rod 4 through a bolt 16, and the flange 9 is positioned at the other end of the unloading rod 4. Between the plug body 3 and the flange 9 there are arranged a launching sleeve 8 and an impact block 7, through which the unloading rod 4 passes and is free to move axially. A support 18 fixed on the test platform 17 provides support for the launching sleeve 8 and the unloading rod 4. The firing sleeve 8 is closed at one end and open at the other end, and the striking block 7 is freely slidable in the firing sleeve 8. Round holes with the same diameter as that of the unloading rod 4 are formed in the center positions of the impact block 7 and the closed end of the launching sleeve 8, and the unloading rod 4 can penetrate through the round holes, and a sealing device is arranged between the round holes in the closed end of the launching sleeve 8 and the unloading rod 4 and can seal a gap between the round holes in the closed end of the sleeve and the unloading rod 4 to prevent air leakage; a valve 13 connected to a gas tank 14 is connected to the launch sleeve 8, and the gas tank 14 is connected to an air compressor 15 and can provide a stable pressure gas source for the launch sleeve 8. The above-mentioned parts are all supported by means of a support 18, the function of the support 18 being to support the above-mentioned parts so that they work coaxially. The support 18 is placed on the test platform 17 to ensure that the components are placed stably.
One end of the test platform 17 is provided with a supporting device 6, and the center of the supporting device 6 is also provided with a hole with the same shape and size as the plug body 3 so as to ensure that the plug body 3 and the unloading rod 4 can freely pass through the supporting device 6 to move. The supporting device 6 is fixedly connected with the baffle 5 through a bolt 16, and the same hole as the central position of the supporting device 6 is also arranged at the central position of the baffle 5 for the plug body 3 and the unloading rod 4 to move freely. A compressive strain gauge 10 is adhered to the unloading rod 4, the compressive strain gauge 10 is connected with a dynamic strain gauge 11, and the dynamic strain gauge 11 is connected with an oscilloscope 12.
One end of the supporting device 6 is fixed on the baffle 5 through a bolt, and a round hole with the same diameter as the unloading rod 4 is reserved at one end of the supporting device for the unloading rod 4 to pass through. The baffle 5 is fixed on the test platform 17 through a connecting clamp, and the baffle 5 is in contact with the surrounding rock model 2 of the underground chamber; a round hole with the same diameter as the unloading rod 4 is reserved in the center of the baffle 5 to ensure that the unloading rod 4 and the plug body 3 can freely pass through.
After all components of the test system are assembled, four hydraulic heads of the ground stress loading device 1 are controlled to apply ground stress to the underground chamber surrounding rock system 2, and the plug body 3 and the ground stress are cooperatively born; after loading to the specified stress and maintaining stability, the material is kept unchanged. Filling a compressed gas with a certain pressure into a gas tank 14 by using an air compressor 15, opening a valve 13 to fill the compressed gas into the emission sleeve 8, and pushing the impact block 7 to impact the flange 9; the flange 9 drives the unloading rod 4 to move, and the unloading rod 4 transmits unloading tension to the plug body 3 and enables the plug body to be separated from the chamber surrounding rock model 2. In the process, waveforms are collected and recorded by using the compressive strain gauge 10, the dynamic strain gauge 11 and the oscilloscope 12, when high-pressure gas in the gas tank 14 is released instantly, the high-pressure gas pushes the impact block 7 to move in the launching sleeve 8, when the edge of the impact block 7 is contacted with and impacted with the flange 9, the impact block 7 and the flange 9 drive the unloading rod 4 and the plug body 3 to continue to move at the same speed, and therefore the plug body 3 can be pulled out of the hole of the chamber surrounding rock model 2 instantly. A series of tensile loading stress waves epsilon are generated at the connecting end of the unloading rod 4 and the flange 9 at the moment of impact i The train of stress waves propagates in the direction of the unloading rod 4 towards the plug body 3 and forms a reflected wave epsilon at the rod end r (ii) a All the stress waves pass through the compression strain gauge adhered to the unloading rod 4And (5) collecting. A typical waveform in the experiment is shown in figure 8. The waveform is simultaneously used for triggering a surrounding rock full-field displacement monitoring device I, so that image acquisition of the free boundary of the surrounding rock model of the chamber under the action of sudden unloading is realized.
Although the method and manufacturing technique of the present invention have been described in terms of preferred embodiments, it will be apparent to those skilled in the art that the method and manufacturing technique described herein can be modified or re-combined to achieve the final manufacturing technique without departing from the scope, spirit and scope of the invention. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and content of the invention.
Claims (1)
1. A test system for simulating the transient unloading of chamber face excavation under different stress conditions is characterized by comprising an in-situ stress simulation device, a transient unloading device and a surrounding rock full-field displacement monitoring device; the in-situ stress simulation device consists of an earth stress loading device and a surrounding rock model of the underground chamber, the surrounding rock model of the underground chamber clamps four loading surfaces of the surrounding rock model by using the earth stress loading device and applies load, and the surrounding rock model of the underground chamber is under the action of plane stress; the ground stress loading device and the chamber surrounding rock model are matched for use and are placed on the same plane vertical to the horizontal plane, and the transient unloading device and the surrounding rock full-field displacement monitoring device are respectively placed in the front direction and the rear direction of the plane; the chamber surrounding rock model is a polygonal plate-shaped rock material, a hole simulation chamber is arranged in the center of the chamber surrounding rock model, the plug body is in a shape of a chamber model palm face, the end head is designed into a cone with the gradient of 1 degree, and the outer part of the other end of the plug body is carved with threads to be connected with the unloading rod end; the ground stress loading device is used for applying loads to four loading surfaces of the underground chamber surrounding rock model and simulating a real ground stress environment of the underground chamber surrounding rock under a test chamber condition; the transient unloading device comprises a test platform, a baffle and a supporting device, wherein the baffle is connected with the supporting device through a bolt, and the baffle is installed at one end, close to a chamber surrounding rock model, of the test platform after being connected with the supporting device; a valve connected with a gas tank is arranged on the launching sleeve, the gas tank is connected with an air compressor, an impact block is arranged in the sleeve, and a circular hole with the diameter the same as that of the unloading rod is arranged in the middle of the impact block and is used for the unloading rod to pass through; the unloading rod is connected with the plug body at one end close to the surrounding rock model of the chamber, and is fixed with the flange at the other end through threads; the test platform is provided with a slide way for adjusting the position of the support; the unloading rod penetrates through the impact block and the sleeve, and a circular hole with threads is machined in the inner circle part at one end of the unloading rod and is fixed with the plug body; the other end of the unloading rod is fixed with the flange through threads; the baffle is fixed on the test platform through a connecting clamp and is in contact with the surrounding rock model of the underground chamber; a circular hole with the same diameter as the unloading rod is reserved in the center of the baffle plate and can be used for the unloading rod and the plug body to pass through; the supporting device is designed to be in a straw hat shape, one end of the supporting device is fixed on the baffle through a bolt, and a round hole with the same diameter as that of the unloading rod is reserved at one end of the supporting device and is used for the unloading rod to pass through for keeping the unloading rod horizontal; the plug body keeps sliding fit with a hole of the surrounding rock model of the underground chamber, the plug body can fill the hole and work with the surrounding rock model of the underground chamber when the ground stress loading device applies ground stress, the plug body bears the ground stress transmitted from the hole of the surrounding rock model of the underground chamber, and the real ground stress environment of the in-situ surrounding rock before underground chamber excavation is simulated; then, high-pressure gas in the gas tank is controlled by a valve to enter the transmitting sleeve, the high-pressure gas drives an impact block in the transmitting sleeve to move in a direction far away from the plug body and impact a flange to generate tensile waves, the flange is connected with the plug body through an unloading rod, so the tensile waves can be propagated in an unloading device, when the tensile waves are propagated to the plug body, the plug body can be continuously pulled away from mother rock, transient unloading is realized due to the fact that the plug body has taper, a surrounding rock whole-field displacement monitoring system is used for monitoring displacement field change information of a free surface of a surrounding rock model of the chamber after transient unloading, the surrounding rock whole-field displacement monitoring device comprises a high-speed camera, the surrounding rock whole-field displacement monitoring device is connected with a computer and is used for measuring, recording and storing the whole-field displacement change of the surrounding rock, the high-speed camera is triggered to measure and record the stress redistribution condition of the unloading instant surrounding rock through a trigger signal, so as to accurately obtain the deformation response relation of the chamber surrounding rock to the sudden unloading action under the condition of the test chamber.
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