CN109916730B - Two-dimensional dynamic and static combined loading analog simulation test method - Google Patents
Two-dimensional dynamic and static combined loading analog simulation test method Download PDFInfo
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- CN109916730B CN109916730B CN201910282368.4A CN201910282368A CN109916730B CN 109916730 B CN109916730 B CN 109916730B CN 201910282368 A CN201910282368 A CN 201910282368A CN 109916730 B CN109916730 B CN 109916730B
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Abstract
The invention discloses a two-dimensional dynamic and static combined loading similar simulation test method, which selects one of coal dust, similar materials, coal dust and similar materials as a test material, utilizes a two-dimensional combined stress induction protruding simulation test device to firstly carry out static loading, then carry out dynamic loading and data acquisition. The loading of multiple stress waves of the coal rock mass can be realized, the traditional drop hammer and Hopkinson bar two dynamic load applying modes are compared, the impact load applying test method is more flexible, the stress conditions are more various, and a two-dimensional dynamic and static combined loading induction coal and gas outburst test is simulated more truly.
Description
Technical Field
The invention relates to a similar simulation test method for researching stress distribution of coal rock mass under dynamic and static combined loading conditions.
Background
The similar model test refers to a physical test, and related data are acquired and design defects are checked by performing corresponding tests on a scaled-down or equal-ratio model. The method is characterized in that a test structure (or a component) which is made of similar materials in proper proportion and is similar to a prototype is loaded in proportion, and a model is stressed to perform a structural test of the actual work of the prototype structure. The test object is a test representative which is copied according to a certain scale by imitating a prototype (actual structure) and has all or part of the characteristics of the actual structure. An important experimental research method for carrying out experimental research by using a model similar to a prototype and applying the research result to the prototype is widely applied to various subject fields. Its main advantage is: the main test parameters can be controlled without being limited and influenced by environmental conditions; the test parameters can be changed conveniently to carry out the comparison test; the economy is good.
With the continuous improvement of the mining depth and strength of a mine, mine dynamic disaster accidents related to coal and rock instability and damage become more serious day by day, rock burst and coal and gas outburst occurrence frequency, strength and damage degree have obvious rising trends along with the increase of mining depth and the rise of gas pressure, and a considerable part of deep well disasters show the phenomena that the rock burst and the coal and gas outburst exist simultaneously and are mutually coupled, namely deep well composite dynamic disasters. Therefore, the research on the outburst occurrence mechanism of the coal containing gas under the action of complex stress is necessary.
The dynamic load applying mode of the existing coal and gas outburst simulation test method and the matching device thereof is two types of drop hammer and Hopkinson bar, the existing coal and gas outburst simulation test method has a good impact load simulation effect, but the existing coal and gas outburst simulation test method cannot realize the loading of various stress waves of coal rock mass, and cannot meet the research of inducing coal and gas outburst under various dynamic load conditions.
Disclosure of Invention
The invention aims to provide a test device which has a large model size and can simulate two-dimensional dynamic and static combination loading induction coal and gas outburst, and can better simulate the mechanical characteristics of a coal rock mass under a complex stress condition.
Therefore, the technical scheme adopted by the invention is as follows: a two-dimensional combined stress induction protrusion simulation test device comprises a counterforce frame and a test piece box, wherein the counterforce frame is a closed fixed frame structure surrounded by a left upright post, a right upright post, an upper cross beam and a lower cross beam, the left side and the right side of the counterforce frame are respectively provided with a support frame, the counterforce frame can turn over by 90 degrees around the installation axis of the counterforce frame under the driving of a speed reduction motor, a servo hydraulic oil cylinder with a downward pressure head is installed on the upper cross beam, a servo hydraulic oil cylinder with a rightward pressure head is installed on the left upright post, support blocks are respectively installed on the right upright post and the lower cross beam, and the servo hydraulic oil cylinder and the support; each pressure head is provided with a piston which penetrates through the test piece box and is used for being connected with a pressure plate in the test piece box;
the test piece case includes box and case lid, and the built-in gas filling pipeline in box bottom below to evenly aerify to the box through the foam metal layer of laying at the bottom half, outstanding mouth and sensor wiring hole have still been seted up on the lateral wall of box, pressure relief device is installed outward to the outstanding mouth, the downthehole sensor crossover sub that installs of sensor wiring.
The simulation test device preferably further comprises a control console, a hydraulic station and a single-rail electric hoist; a pressure sensor, a temperature sensor and a pore pressure sensor are arranged in the test piece box and used for measuring the coal rock stress, the temperature of a coal sample and the propagation rule and attenuation characteristic of gas pressure in the protruding process; the control console controls the servo controller through a computer to realize the loading and regulation of various stress waves and collect and record data of a sensor arranged in the test piece box in the test process; the hydraulic station provides power for a hydraulic oil cylinder on the counter-force frame; the monorail electric hoist is arranged above the counter-force frame and used for hoisting a heavy object; the front end of the protrusion opening is provided with a high-speed camera for realizing visualization of the whole protrusion process, and is matched with an acoustic emission device for researching the acoustic emission phenomenon development law in the coal and gas protrusion process.
More preferably, the reduction motor is mounted on a support frame on the right side of the reaction frame, and the left and right sides of the reaction frame are respectively mounted through bearings; the lower parts of the two support frames are welded on the same base to form a U-shaped frame.
Preferably, the servo hydraulic cylinders comprise hydraulic cylinders and servo controllers, the hydraulic cylinders are fixed on the reaction frame through long bolts and clamping plates, displacement sensors and stress sensors are further mounted on pressure heads of the hydraulic cylinders, the upper cross beam is provided with three servo hydraulic cylinders, the left upright post is provided with one servo hydraulic cylinder, two servo hydraulic cylinders are used for static load loading, two servo hydraulic cylinders are used for dynamic load loading, and each servo controller can be matched with any hydraulic cylinder.
Preferably, the front side baffle and the rear side baffle of the reaction frame are provided with side baffles, so that the overall stability of the reaction frame in the test process is ensured, and the deformation of the test piece box along the normal direction of the two-dimensional stress action surface is limited.
Further preferably, the upper left corner in the box is provided with the headspace, and when being equipped with the test piece in the box, the cushion has been laid to the upper left corner position department of test piece, the upper end of vertical clamp plate, the left end of the horizontal clamp plate of leftmost is pressed on the cushion jointly, prevents that the clamp plate from impressing the piece on the test piece in the headspace when moving.
Preferably, the side wall of the box body and the top of the box cover are respectively provided with a hanging ring, the box cover is also provided with an exhaust hole, and the inlet and the exhaust hole of the gas filling pipeline are respectively sealed by plugs. Hoisting the box body and the box cover through the hoisting ring, and specially using the box body and the box cover for the test piece box with larger model size.
Preferably, the gas filling pipeline is composed of an L-shaped hole arranged in the box body and criss-cross grid net pipes which are arranged below the foam metal layer and communicated with the L-shaped hole, and the tops of the grid net pipes are provided with notches. The novel gas filling pipeline structure is adopted, and gas filled through the L-shaped holes is uniformly dispersed through the criss-cross grid net pipes with the notches at the tops, is sent out through the notches and is sent into the box body through the foam metal layer, so that uniform and stable gas filling to a test piece in the box body is further ensured.
Meanwhile, the invention also provides a two-dimensional dynamic and static combined loading analog simulation test method, which can better simulate the mechanical properties of the coal rock mass under the complex stress condition.
A two-dimensional dynamic and static combined loading similar simulation test method is characterized by comprising the following steps:
(1) the selection of the test materials is divided into the following three cases and one of the three cases is selected:
(a) coal powder: all the coal powder is loaded in the test piece box, and stress characteristics of the coal bed under various stress conditions are researched;
breaking and screening a coal sample required by the test; loading the screened coal powder into a test piece box, and simultaneously embedding a stress sensor; pressing and molding the coal powder in the test piece box in a molding machine according to certain pressure; covering the test piece box for later use;
(b) similar materials: the test piece box is completely loaded with single-layer or multi-layer similar materials, and stress characteristics of a rock mass or multi-layer rock mass under various stress conditions are researched;
calculating the required mass of each layer of similar material according to the geometric similarity ratio, the stress similarity ratio and the mass similarity ratio; uniformly mixing river sand, cement and gypsum according to a certain proportion, adding a proper amount of water, further uniformly stirring, pouring into a test piece box layer by layer, and simultaneously embedding a stress sensor until all rock stratum similar materials are filled into the test piece box; pressing and molding similar materials in the test piece box in a molding machine according to certain pressure; covering the test piece box for later use;
(c) similar materials and coal dust: adding similar materials and coal powder into the test piece box at the same time, and carrying out stress characteristic research on the coal seam with the top and bottom plates under various stress conditions;
calculating the mass required by the similar materials of the bottom plate and the top plate according to the geometric similarity ratio, the stress similarity ratio and the mass similarity ratio; uniformly mixing river sand, cement and gypsum according to the required proportion of similar materials of the bottom plate, adding a proper amount of water, further uniformly stirring, and pouring into a test piece box; breaking and screening a coal sample required by the test; after the similar material of the bottom plate is completely and naturally dried, the screened coal powder is loaded into a test piece box, and a stress sensor is simultaneously embedded and tamped; uniformly mixing river sand, cement and gypsum according to the proportion required by similar materials of the roof plate, adding a proper amount of water, further uniformly stirring, and pouring into a test piece box; covering the test piece box for later use;
(2) the servo hydraulic oil cylinder is retracted, the reaction frame is turned over by 90 degrees and is horizontally arranged, so that the test piece box is conveniently placed into a preset position of the reaction frame;
(3) after the reaction frame is horizontally arranged, the upper beam of the reaction frame is removed;
(4) turning the test piece box by 90 degrees, wherein the test piece box corresponds to a hydraulic oil cylinder arranged on the counter-force frame in position;
(5) hoisting the test piece box through the single-rail electric hoist, and placing the test piece box at a preset position in the counter-force frame;
(6) installing the upper cross beam dismantled in the step (3), and reversely overturning the reaction frame by 90 degrees to enable the reaction frame and the test piece box to be restored together;
(7) contacting the pressure head with the test piece box, checking whether the connection line of the sensor is normal, and preparing to carry out a test;
(8) and carrying out a two-dimensional dynamic and static combined loading similar simulation test and acquiring data.
As a preferred preference of the two-dimensional dynamic and static combined loading similar simulation test method, in the step (8), static loading is performed first, then dynamic loading and data acquisition are performed, wherein the vertical direction is the Z direction, the left-right direction is the X direction, and the front-back direction is the Y direction;
static load loading:
(a) loading a kilonewtons in the Z direction and the X direction at the same time, wherein a is a natural number;
(b) keeping the load for t minutes, wherein t is a natural number;
(c) loading the vertical pressure in the Z direction and the horizontal pressure in the X direction to 2a kilonewtons simultaneously;
(d) repeating the steps (a) - (c) until the bidirectional loading pressure reaches a preset value, wherein in the steps (a) - (d), the loading speed is constant;
dynamic load loading and data acquisition:
(a) applying a horizontal dynamic load in the X direction, wherein the step of applying the horizontal dynamic load comprises setting dynamic load amplitude; setting dynamic load frequency; setting dynamic load cycle times; starting to apply dynamic load and observing recorded data;
(b) applying vertical dynamic load in the Z direction, including setting dynamic load amplitude; setting dynamic load frequency; setting dynamic load cycle times; starting to apply dynamic load and observing recorded data;
(c) applying horizontal dynamic load in the X direction and applying vertical dynamic load in the Z direction, wherein the dynamic load amplitude is set; setting dynamic load frequency; setting dynamic load cycle times; starting to apply dynamic load and observing recorded data;
in the steps (a) to (c), the dynamic load data acquisition system acquires stress and displacement data at the pressure head, and the stress sensor embedded in the test piece box in advance acquires stress data inside the coal rock mass.
The invention has the beneficial effects that: the traditional two dynamic load applying modes of a drop hammer and a Hopkinson bar are abandoned, a load loading mechanism consisting of a servo hydraulic oil cylinder, a piston and a pressing plate is adopted to load a horizontal load and a vertical load, each pressing head can apply the load independently or synchronously, the test method for applying the impact load is more flexible, the stress conditions are more various, the loading of various stress waves of the coal-rock body can be realized, and the stress characteristics of the coal-rock body under more working conditions can be researched; the counter-force frame with the 90-degree overturning function is convenient for mounting a test piece with a larger size; the built-in gas filling pipeline and the foam metal layer at the bottom of the box body are combined, so that the box body can be uniformly and stably inflated, and a two-dimensional dynamic and static combined loading induction coal and gas outburst test can be simulated more truly.
Drawings
FIG. 1 is a schematic structural diagram of a two-dimensional combined stress-induced protrusion simulation test device.
Fig. 2 is a schematic view showing the mounting of the reaction force frame and the specimen box.
Fig. 3 is a schematic view of the structure of the test piece case.
Fig. 4 is a top view of fig. 3.
Fig. 5 is a left side view of fig. 3.
Fig. 6 is a partial cross-sectional view of a mesh tube of the grid.
Fig. 7 is a schematic view of the construction of the transducer adapter.
Fig. 8 is a schematic structural view of the pressure relief device.
Fig. 9 is a schematic structural view of a pressure-bearing clamp of the pressure relief device.
FIG. 10 is a schematic view of a coal seam test piece with roof and floor.
Detailed Description
The invention will be further illustrated by the following examples in conjunction with the accompanying drawings:
referring to fig. 1-6, a two-dimensional combined stress-induced protrusion simulation test device mainly comprises a reaction frame a, a test piece box B, a single-rail electric hoist 20, a control console 21 and a hydraulic station 22.
The reaction frame a is a closed fixed frame structure surrounded by a left column 12, a right column 13, an upper beam 14, and a lower beam 15. The left side and the right side of the reaction frame A are respectively provided with a support frame 16, and the lower parts of the two support frames 16 are preferably welded on the same base 19 to form a U-shaped frame, so that the integral strength is improved, and the installation is convenient.
The reaction frame A can be overturned by 90 degrees around the installation axis of the reaction frame A under the driving of the speed reducing motor 24, the reaction frame A is rotated by 90 degrees to a horizontal position before the test, the sample is loaded, and the reaction frame A is rotated to a vertical position when the test is started, so that the test operation is convenient. The reduction motor 24 is mounted on the support frame 16 on the right side of the reaction frame a, and the left and right sides of the reaction frame a are respectively mounted through bearings, so that flexible overturning is realized.
The upper cross beam 14 is provided with a servo hydraulic oil cylinder 17 with a pressure head 3 facing downwards, the left upright post 12 is provided with a servo hydraulic oil cylinder 17 with a pressure head 3 facing rightwards, the right upright post 13 and the lower cross beam 15 are respectively provided with a supporting block 18, and the servo hydraulic oil cylinder 17 and the supporting block 18 jointly clamp the test piece box B in the reaction frame A.
The servo hydraulic cylinder 17 is mainly composed of a hydraulic cylinder 17a and a servo controller 17b, and the servo controller 17b is preferably installed directly above the cylinder body of the hydraulic cylinder 17 a. Each hydraulic cylinder 17a is fixed to the reaction frame a by a long bolt and a holding plate 23. A displacement sensor and a stress sensor (not shown) are also mounted on the ram 3 of the hydraulic cylinder 17 a. The servo hydraulic oil cylinder 17 controls the pressure head 3, and three loading modes of static load, dynamic load and dynamic and static combined loading can be transmitted. The servo controller 17b is connected to the console 21 through a data line, and realizes accurate control of the loading mode, size, and time.
Preferably, the upper cross beam 14 is provided with three servo hydraulic cylinders 17, the left upright post 12 is provided with one servo hydraulic cylinder 17, two servo hydraulic cylinders 17 are used for static load loading, two servo hydraulic cylinders 17 are used for dynamic load loading, and each servo controller 17b can be matched with any hydraulic cylinder 17 a.
Each ram 3 is provided with a piston 4 passing through the test piece box B for connection to a pressure plate 5 in the test piece box B. The size of the pressure head 3 is preferably consistent for the same test piece box, so that the model selection is convenient. Three pressing plates 5 corresponding to the upper cross beam 14 are sequentially arranged left and right and are in close contact, so that uniform pressurization in the vertical direction is ensured. When the size of the test piece box is fixed, the number of the pressure heads in two directions is determined after the size of the pressure head 3 is selected and determined; however, the number of rams may be selected differently depending on the desired pressure.
And a pressure sensor, a temperature sensor and a pore pressure sensor are arranged in the test piece box B and used for measuring the coal rock stress, the temperature of the coal sample and the propagation rule and attenuation characteristic of the gas pressure in the protruding process. The console 21 controls the servo controller 17b through a computer to realize the loading and regulation of various stress waves, and collects and records data of the sensor arranged in the test piece box A in the test process.
The hydraulic rams are connected to a hydraulic station 22 which provides power to the hydraulic rams 17a on the reaction frame a. Because the weight of the coal sample reaches several tons and the weight of other parts is also larger, the single-rail electric hoist 20 is arranged above the reaction frame A for hoisting and installing the test piece box or hoisting other heavy objects for the convenience of installation. The high-speed camera is arranged at the front end of the outburst port and used for recording the dynamic process of coal and gas outburst, realizing visualization of the whole outburst process and matching with the acoustic emission device to be used for researching the acoustic emission phenomenon development rule in the coal and gas outburst process.
Side baffles (not shown in the figure) are arranged on the front side and the rear side of the reaction frame A to ensure the overall stability of the reaction frame A in the test process and limit the normal deformation of the test piece box B along the two-dimensional stress action surface.
The test piece box B consists of a box body 1 and a box cover 2. A gas filling pipeline 7 is arranged in the lower part of the bottom of the box body 1, and the foam metal layer 6 laid on the bottom of the box body 1 is used for uniformly filling gas into the box body 1. The side wall of the box body 1 is also provided with a protrusion port 1a and a sensor wiring hole 1b, a pressure relief device 8 is arranged outside the protrusion port 1a, and a sensor adapter 9 is arranged in the sensor wiring hole 1 b. Preferably, the pressure relief device 8 is provided on the right side wall of the case 1, and the sensor joint 9 is provided on any one of the front, rear, and right side walls of the case 1 so as to be offset from the hydraulic cylinder 17a on the left side wall.
A reserved space 1c is arranged at the upper left corner in the box body 1 to ensure that all the pressing plates 5 move smoothly. Cushion 10 has been laid to the upper left corner position department of test piece, and when being equipped with the test piece in box 1, vertical clamp plate 5's upper end, the left end of leftmost horizontal clamp plate 5 is pressed on cushion 10 jointly, can prevent to impress the piece on the test piece during 5 movements of clamp plate into headspace 1 c.
The side wall of the box body 1 and the top of the box cover 2 are respectively provided with a hanging ring 11, the box cover 2 is also provided with an exhaust hole 2a, and the inlet of the gas filling pipeline 7 and the exhaust hole 2a are respectively sealed by plugs. After the test is finished, the vent hole 2a is opened to exhaust, and then the disassembly can be carried out, so that the safety of the operation is ensured.
The gas filling pipeline 7 consists of an L-shaped hole 7a arranged in the box body 1 and a criss-cross grid mesh pipe 7b which is arranged below the foam metal layer 6 and communicated with the L-shaped hole 7a, and the top of the grid mesh pipe 7b is provided with a notch 7 c.
The box body 1 and the box cover 2 are connected through bolts, and a sealing ring is arranged at the interface. A sealed cavity surrounded by the box body 1 and the box cover 2 is used for laying a test piece of a coal and gas outburst simulation test, such as coal powder or similar materials. Preferably, the test piece box is 100cm long by 40cm wide by 40cm high.
Referring to fig. 1, 2 and 7, in order to obtain data related to coal and gas outburst under various stress conditions, various sensors embedded in the test piece box B are connected to a control console 21 outside the test piece box through sensor connection holes 1B on the side wall of the box body 1. In order to ensure that the gas pressure in the test piece box is constant in the test process, the sensor wiring hole 1b is preferably plugged by the sensor adapter 9, and a sensor wire is led out to connect the sensor with the control console 21 while the gas pressure is ensured by plugging. The sensor adapter 9 consists of a T-shaped circular truncated cone main body 9-1, a gasket 9-2, a sealing ring 9-3, a lead wire 9-4 and an insulated lead tube 9-5.
The T-shaped circular truncated cone main body 9-1 is matched with a T-shaped sensor wiring hole 1b formed in the side wall of the test piece box, and the T-shaped circular truncated cone main body 9-1 can be inserted into the T-shaped sensor wiring hole 1b from inside to outside. The T-shaped round table main body 9-1 comprises a small round table and a large round table, and a gasket 9-2 and a sealing ring 9-3 are sleeved on the small round table. After installation, the gasket 9-2 and the sealing ring 9-3 are pressed in the T-shaped sensor wiring hole 1b by the step surface of the T-shaped circular truncated cone main body 9-1.
The middle part of the T-shaped round table main body 9-1 is provided with at least two through pipe holes. The number of the pipe holes is preferably four, but not limited to four, and all the pipe holes are uniformly distributed around the center of the T-shaped round platform main body 9-1 in a circumferential mode according to the requirement.
An insulating lead tube 9-5 is inserted in each tube hole, the insulating lead tube 9-5 and the tube holes are fixed by adopting viscose glue, and two ends of the insulating lead tube 9-5 extend out of the tube holes. A lead wire 9-4 is inserted in each insulated lead tube 9-5, the lead wire 9-4 and the insulated lead tube 9-5 are fixed by adopting viscose glue, and both ends of the lead wire 9-4 extend out of the insulated lead tube 9-5. The conducting wire 9-4 is preferably a copper wire.
The inner end of the lead 9-4 is used for being connected with a connecting wire of a sensor in the test piece box, and the outer end of the lead 9-4 is used for being connected with a control console 21 outside the test piece box. Preferably, the inner end of the lead 9-4 is connected with the connecting wire of the sensor in the test piece box by welding.
The sensor wiring hole on the test piece box is effectively sealed through the T-shaped circular truncated cone main body, the gasket and the sealing ring, so that the integral air tightness of the test piece box is ensured, the installation is convenient, and the connection is stable; because the sensor wiring hole of test piece case also is the step form, in the test process, when test piece case internal pressure was greater than external atmospheric pressure, an outside effort was applyed to sensor crossover sub to internal pressure, and the sealing washer will further closely knit the test piece box, and the binding face in the sensor wiring hole of "T" shape round platform main part and test piece case increases, makes whole bearing capacity promote, and the leakproofness reinforcing promotes the pressurize performance of test piece case.
Referring to the figures 1, 2, 8 and 9, the pressure relief device 8 comprises a left support 8-1, a right support 8-2, a pressure-bearing clamp 8-3, a bolt and nut assembly 8-4, a sealing ring 8-5, a first rupture disk 8-6, a second rupture disk 8-7 and a pressure sensor 8-8. The pressure-bearing clamp holder 8-3 is positioned between the left support 8-1 and the right support 8-2 and is tightly locked and installed outside the protruding opening 1a of the test piece box through bolt and nut assemblies 8-4 which are uniformly distributed on the circumference. The pressure-bearing clamp 8-3 adopts a left-middle-right three-section type assembly structure, and the middle parts of each section of the left support 8-1, the right support 8-2 and the pressure-bearing clamp 8-3 are respectively provided with an air flow through hole which is opposite to the protrusion opening 1 a. A first rupture disk 8-6 is clamped and installed between the left section and the middle section of the pressure-bearing clamper 8-3, a second rupture disk 8-7 is clamped and installed between the middle section and the right section of the pressure-bearing clamper 8-3, the inner sides of the first rupture disk 8-6 and the second rupture disk 8-7 are respectively provided with a pressure sensor 8-8, the side wall of the middle section of the pressure-bearing clamper 8-3 is provided with an air charging hole 8-3a, the air flow in the test piece box can enter a closed space surrounded by the left support 8-1, the left section of the pressure-bearing clamper 8-3 and the first rupture disk 8-6 through the protrusion 1a, the gas in the gas charging hole 8-3a can enter a closed space surrounded by the middle section of the pressure-bearing clamper 8-3, the right section of the pressure-bearing clamper 8-3, the first rupture disk 8-6 and the second rupture disk 8-7.
The pressure-bearing clamp holder 8-3 also comprises at least two fixing pieces 8-3b, the left end and the right end of each fixing piece 8-3b are respectively fixed on the outer walls of the left section and the right section of the pressure-bearing clamp holder 8-3 through locking screws 8-3c, and the quick assembly of the left section, the middle section and the right section is realized. A sealing ring 8-5 is arranged between the left support 8-1 and the left section of the pressure-bearing clamper 8-3.
The pressure relief device is a controllable rapid pressure relief device, in the test process, the test piece box is pressurized, the booster pump pressurizes the pressure-bearing clamp through the inflation hole, the pressure is kept lower than the pressure of the test piece box and lower than the blasting pressure of the first and second blasting pieces, one part of the pressure borne by the first blasting piece at the end connected with the test piece box is balanced by the pressure in the pressure-bearing clamp, and the first blasting piece cannot be damaged; the second rupture disk at the air contact end can not be ruptured because the pressure is lower than the bursting pressure; the pressure in the pressure-bearing clamp holder is accurately measured and displayed by a pressure sensor; when the pressure sensor monitors that the pressure reaches a preset value and a coal and gas outburst test is to be carried out, the booster pump continues to pressurize the pressure-bearing clamp holder through the air charging hole until the second rupture disk in contact with air is firstly exploded, and then the coal and gas outburst simulation process is caused due to the fact that the air pressure in the test piece box is unbalanced with the air pressure in the pressure-bearing clamp holder.
The working principle is as follows: when the pressure in the pressure-bearing clamp holder is greater than the blasting pressure, the pressure borne by the first blasting sheet at one end connected with the test piece box cannot reach the blasting pressure, and the first blasting sheet cannot be damaged; the second rupture disk at the air contact end is firstly destroyed, the pressure in the pressure-bearing clamp holder is instantaneously released, the first rupture disk at the end connected with the test piece box has no balance pressure, the pressure in the test piece box is far greater than the explosion pressure, and the first rupture disk is instantaneously exploded, so that the artificial control of the explosion time is realized.
The pressure relief device can realize quick and automatic pressure relief of the protrusion opening, avoid the influence of too slow opening of the protrusion opening on protrusion energy, and simulate the coal and gas protrusion process more truly; the blasting time is artificially controlled, the blasting time is not influenced by the pressure in the test piece box, the outburst tests under different pressures can be carried out, and the outburst pressure can be controlled.
A two-dimensional dynamic and static combined loading similar simulation test method comprises the following steps:
(1) the selection of the test materials is divided into the following three cases and one of the three cases is selected:
(a) coal powder: all the coal powder is loaded in the test piece box, and stress characteristics of the coal bed under various stress conditions are researched;
breaking and screening a coal sample required by the test; loading the screened coal powder into a test piece box, and simultaneously embedding a stress sensor; pressing and molding the coal powder in the test piece box in a molding machine according to certain pressure; covering the test piece box for later use;
(b) similar materials: the test piece box is completely loaded with single-layer or multi-layer similar materials, and stress characteristics of a rock mass or multi-layer rock mass under various stress conditions are researched;
calculating the required mass of each layer of similar material according to the geometric similarity ratio, the stress similarity ratio and the mass similarity ratio; uniformly mixing river sand, cement and gypsum according to a certain proportion, adding a proper amount of water, further uniformly stirring, pouring into a test piece box layer by layer, and simultaneously embedding a stress sensor until all rock stratum similar materials are filled into the test piece box; pressing and molding similar materials in the test piece box in a molding machine according to certain pressure; covering the test piece box for later use;
(c) similar materials and coal dust: adding similar materials and coal powder into the test piece box at the same time, and carrying out stress characteristic research on the coal seam with the top and bottom plates under various stress conditions;
calculating the mass required by the similar materials of the bottom plate and the top plate according to the geometric similarity ratio, the stress similarity ratio and the mass similarity ratio; uniformly mixing river sand, cement and gypsum according to the required proportion of similar materials of the bottom plate, adding a proper amount of water, further uniformly stirring, and pouring into a test piece box; breaking and screening a coal sample required by the test; after the similar material of the bottom plate is completely and naturally dried, the screened coal powder is loaded into a test piece box, and a stress sensor is simultaneously embedded and tamped; uniformly mixing river sand, cement and gypsum according to the proportion required by similar materials of the roof plate, adding a proper amount of water, further uniformly stirring, and pouring into a test piece box; covering the test piece box for later use; as shown in fig. 10, the test piece has a top and bottom sheet of similar material 25 with a coal seam 26 in the middle.
(2) The servo hydraulic oil cylinder is retracted, the reaction frame is turned over by 90 degrees and is horizontally arranged, so that the test piece box is conveniently placed into a preset position of the reaction frame;
(3) after the reaction frame is horizontally arranged, the upper beam of the reaction frame is removed;
(4) turning the test piece box by 90 degrees, wherein the test piece box corresponds to a hydraulic oil cylinder arranged on the counter-force frame in position;
(5) hoisting the test piece box through the single-rail electric hoist, and placing the test piece box at a preset position in the counter-force frame;
(6) installing the upper cross beam dismantled in the step (3), and reversely overturning the reaction frame by 90 degrees to enable the reaction frame and the test piece box to be restored together;
(7) contacting the pressure head with the test piece box, checking whether the connection line of the sensor is normal, and preparing to carry out a test;
(8) and carrying out a two-dimensional dynamic and static combined loading similar simulation test and acquiring data.
In the step (8), static load loading is firstly carried out, then dynamic load loading and data acquisition are carried out, the up-down direction is the Z direction, the left-right direction is the X direction, and the front-back direction is the Y direction;
static load loading:
(a) loading a kilonewtons in the Z direction and the X direction at the same time, wherein a is a natural number;
(b) keeping the load for t minutes, wherein t is a natural number;
(c) loading the vertical pressure in the Z direction and the horizontal pressure in the X direction to 2a kilonewtons simultaneously;
(d) repeating the steps (a) - (c) until the bidirectional loading pressure reaches a preset value, wherein in the steps (a) - (d), the loading speed is constant;
dynamic load loading and data acquisition:
(a) applying a horizontal dynamic load in the X direction, wherein the step of applying the horizontal dynamic load comprises setting dynamic load amplitude; setting dynamic load frequency; setting dynamic load cycle times; starting to apply dynamic load and observing recorded data;
(b) applying vertical dynamic load in the Z direction, including setting dynamic load amplitude; setting dynamic load frequency; setting dynamic load cycle times; starting to apply dynamic load and observing recorded data;
(c) applying horizontal dynamic load in the X direction and applying vertical dynamic load in the Z direction, wherein the dynamic load amplitude is set; setting dynamic load frequency; setting dynamic load cycle times; starting to apply dynamic load and observing recorded data;
in the steps (a) to (c), the dynamic load data acquisition system acquires stress and displacement data at the pressure head, and the stress sensor embedded in the test piece box in advance acquires stress data inside the coal rock mass.
Preferably, the maximum load of static load loading is 5-500 kN; the dynamic load frequency range is 0.01 Hz-10 Hz.
Claims (4)
1. A two-dimensional dynamic and static combined loading similar simulation test method is characterized by comprising the following steps:
(1) the selection of the test materials is divided into the following three cases and one of the three cases is selected:
(a) coal powder: all the coal powder is loaded in the test piece box, and stress characteristics of the coal bed under various stress conditions are researched;
breaking and screening a coal sample required by the test; loading the screened coal powder into a test piece box, and simultaneously embedding a stress sensor; pressing and molding the coal powder in the test piece box in a molding machine according to certain pressure; covering the test piece box for later use;
(b) similar materials: the test piece box is completely loaded with single-layer or multi-layer similar materials, and stress characteristics of a rock mass or multi-layer rock mass under various stress conditions are researched;
calculating the required mass of each layer of similar material according to the geometric similarity ratio, the stress similarity ratio and the mass similarity ratio; uniformly mixing river sand, cement and gypsum according to a certain proportion, adding a proper amount of water, further uniformly stirring, pouring into a test piece box layer by layer, and simultaneously embedding a stress sensor until all rock stratum similar materials are filled into the test piece box; pressing and molding similar materials in the test piece box in a molding machine according to certain pressure; covering the test piece box for later use;
(c) similar materials and coal dust: adding similar materials and coal powder into the test piece box at the same time, and carrying out stress characteristic research on the coal seam with the top and bottom plates under various stress conditions;
calculating the mass required by the similar materials of the bottom plate and the top plate according to the geometric similarity ratio, the stress similarity ratio and the mass similarity ratio; uniformly mixing river sand, cement and gypsum according to the required proportion of similar materials of the bottom plate, adding a proper amount of water, further uniformly stirring, and pouring into a test piece box; breaking and screening a coal sample required by the test; after the similar material of the bottom plate is completely and naturally dried, the screened coal powder is loaded into a test piece box, and a stress sensor is simultaneously embedded and tamped; uniformly mixing river sand, cement and gypsum according to the proportion required by similar materials of the roof plate, adding a proper amount of water, further uniformly stirring, and pouring into a test piece box; covering the test piece box for later use;
(2) the servo hydraulic oil cylinder is retracted, the reaction frame is turned over by 90 degrees and is horizontally arranged, so that the test piece box is conveniently placed into a preset position of the reaction frame;
(3) after the reaction frame is horizontally arranged, the upper beam of the reaction frame is removed;
(4) turning the test piece box by 90 degrees, wherein the test piece box corresponds to a hydraulic oil cylinder arranged on the counter-force frame in position;
(5) hoisting the test piece box through the single-rail electric hoist, and placing the test piece box at a preset position in the counter-force frame;
(6) installing the upper cross beam dismantled in the step (3), and reversely overturning the reaction frame by 90 degrees to enable the reaction frame and the test piece box to be restored together;
(7) contacting the pressure head with the test piece box, checking whether the connection line of the sensor is normal, and preparing to carry out a test;
(8) carrying out a two-dimensional dynamic and static combined loading similar simulation test and acquiring data;
the reaction frame is a closed fixed frame structure formed by a left upright post, a right upright post, an upper cross beam and a lower cross beam in a surrounding mode, the left side and the right side of the reaction frame are respectively provided with a support frame, the reaction frame can turn over 90 degrees around the installation axis of the reaction frame under the driving of a speed reducing motor, a servo hydraulic oil cylinder with a downward pressure head is installed on the upper cross beam, a servo hydraulic oil cylinder with a rightward pressure head is installed on the left upright post, support blocks are respectively installed on the right upright post and the lower cross beam, and the servo hydraulic oil cylinder and the support blocks jointly clamp a test piece box in; each pressure head is provided with a piston which penetrates through the test piece box and is used for being connected with a pressure plate in the test piece box;
the test piece box comprises a box body and a box cover, wherein a gas filling pipeline is arranged below the bottom of the box body and can uniformly inflate the box body through a foam metal layer laid at the bottom of the box body;
the monorail electric hoist is arranged above the counter-force frame and used for hoisting a heavy object.
2. The two-dimensional dynamic and static combined loading analog simulation test method according to claim 1, wherein in the step (8), static loading is performed first, and then dynamic loading and data acquisition are performed, wherein the up-down direction is a Z direction, the left-right direction is an X direction, and the front-back direction is a Y direction;
static load loading:
(a) loading a kilonewtons in the Z direction and the X direction at the same time, wherein a is a natural number;
(b) keeping the load for t minutes, wherein t is a natural number;
(c) loading the vertical pressure in the Z direction and the horizontal pressure in the X direction to 2a kilonewtons simultaneously;
(d) repeating the steps (a) - (c) until the bidirectional loading pressure reaches a preset value, wherein in the steps (a) - (d), the loading speed is constant;
dynamic load loading and data acquisition:
(a) applying a horizontal dynamic load in the X direction, wherein the step of applying the horizontal dynamic load comprises setting dynamic load amplitude; setting dynamic load frequency; setting dynamic load cycle times; starting to apply dynamic load and observing recorded data;
(b) applying vertical dynamic load in the Z direction, including setting dynamic load amplitude; setting dynamic load frequency; setting dynamic load cycle times; starting to apply dynamic load and observing recorded data;
(c) applying horizontal dynamic load in the X direction and applying vertical dynamic load in the Z direction, wherein the dynamic load amplitude is set; setting dynamic load frequency; setting dynamic load cycle times; starting to apply dynamic load and observing recorded data;
in the steps (a) to (c), the dynamic load data acquisition system acquires stress and displacement data at the pressure head, and the stress sensor embedded in the test piece box in advance acquires stress data inside the coal rock mass.
3. The two-dimensional dynamic and static combined loading similar simulation test method according to claim 2, characterized in that the maximum load of static loading is 5-500 kN.
4. The two-dimensional dynamic and static combined loading analog simulation test method according to claim 2, wherein the dynamic load frequency range is 0.01Hz to 10 Hz.
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