CN115931568A - Rock mass true triaxial test system and method based on' first unloading-then anchoring-then disturbing - Google Patents
Rock mass true triaxial test system and method based on' first unloading-then anchoring-then disturbing Download PDFInfo
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- 238000004873 anchoring Methods 0.000 claims abstract description 98
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A10/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE at coastal zones; at river basins
- Y02A10/23—Dune restoration or creation; Cliff stabilisation
Abstract
The invention discloses a rock mass true triaxial test system and method based on 'first unloading, second anchoring and second disturbing', and relates to the technical field of rock mass mechanics test equipment. Firstly, a drilling device and a fixed rock sample are arranged on a true triaxial experimental device, and sigma is controlled by a displacement control mode of the true triaxial experimental device 1 、σ 2 、σ 3 Loaded to a predetermined stress value by unloading sigma 3 When the load reaches 0, the load-unloading device is used for simulating the excavation unloading process of underground engineering; drilling a rock sample, and anchoring the rock sample under an anchoring working condition after the drilling process is finished; increase of maximum principal stress sigma 1 To near the peak strength of the anchored rock test. Maintaining the maximum principal stress at this time, and applying a point disturbance load sigma to the surface of the sample by a disturbance actuator and a disturbance rod d Until the sample is completely destroyed; the test results were analyzed. The invention truly reproduces the whole stress process of 'first stress, then excavation, then drilling and anchoring, and finally disturbance and destruction' of the deep engineering rock mass.
Description
Technical Field
The invention relates to the technical field of rock mass mechanics test equipment, in particular to a rock mass true triaxial indoor test system and a rock mass true triaxial indoor test method.
Background
The shallow mineral resources of China tend to be exhausted. In the future, the development of mineral resources in China will be fully advanced to the depth of 1000-2000 m. In a complex deep mining system, deep roadways and stope surrounding rocks are not only affected by high ground stress and excavation unloading, but also may be affected by external dynamic disturbances such as ore caving, ore breaking or adjacent stope mechanical rock drilling. Therefore, the stress environment is complex, and the mining difficulty is increased. Excavation of underground works tends to transfer and release part of the energy stored inside the surrounding rock. The change of the stress state of the surrounding rocks of the deep stope and the roadway after excavation unloading leads to the weakening and aggravation of the strength and the bearing capacity of the near-field surrounding rocks and the increase of unstable blocks, so that the mining of deep mineral resources becomes a very challenging world problem.
The anchor bolt supporting technology is one of the most common surrounding rock reinforcing modes in the engineering fields of deep mining and the like, and indoor tests are also important means for anchor bolt anchoring effect and mechanism research. At present, mechanical property tests and anchoring mechanism researches of an anchored rock mass are mostly based on tests such as uniaxial compression, biaxial compression, dynamic impact and the like, but the researches on the anchoring effect and the control mechanism of the mining rock mass under the deep multidimensional stress environment are not common. In fact, the occurrence mechanism of the deep mine disaster is closely related to the true three-dimensional stress environment (the main stress in three directions is often different) and the engineering excavation disturbance of the deep rock mass. In addition, in the prior art, the anchoring body is anchored in the rock sample before load is applied to the rock mass anchoring and destruction characteristic test, and the anchor rod in the actual engineering is installed after excavation and unloading, so that the rock mass is not only subjected to high ground stress but also influenced by excavation damage before anchoring, and is possibly subjected to external power disturbance after anchoring.
Therefore, the device and the method in the prior art cannot reproduce the complicated and changeable stress change environment of the simulated deep coal rock, and the prior art needs to be further improved.
Disclosure of Invention
The invention aims to provide a rock mass true triaxial test system based on 'unloading-anchoring-disturbing-then-disturbing', which truly reproduces the whole stress process of 'first stress, then excavation, then drilling and anchoring, and finally disturbance and destruction' of a deep engineering rock mass.
In order to achieve the purpose, the invention adopts the following technical scheme:
a rock mass true triaxial test system based on 'first unloading, second anchoring and second interference' comprises a true triaxial test device, wherein the true triaxial test device comprises a test bin, a loading mechanism and a clamp assembly, the test bin is of a frame structure and is positioned on a test bed, a rock sample is placed in the test bin, and the loading mechanism comprises a loading unit and upper, lower, left, right, front and rear loading plates; the movable anchoring support device comprises a first stirring mechanism and a second stirring mechanism, wherein the first stirring mechanism is arranged on an upper loading plate and a lower loading plate which are positioned at the maximum principal stress, and the second stirring mechanism is arranged on a front loading plate and a rear loading plate which are positioned at the middle stress;
the first disturbance mechanism and the second disturbance mechanism respectively comprise static actuators, disturbance rods, connecting rods and disturbance actuators, the two static actuators are respectively installed on the upper loading plate and the right loading plate, and the two disturbance rods, the connecting rods and the disturbance actuators are respectively installed on the lower loading plate and the left loading plate; the disturbance actuator, the connecting rod and the disturbance rod are sequentially connected, and the other end of the disturbance rod is in contact with the surface of the rock sample;
the movable anchoring and supporting device comprises a moving mechanism, a supporting mechanism and an anchoring and supporting mechanism, wherein the moving mechanism comprises a base, a first guide rail and a first hydraulic cylinder, one end of the base is aligned with the test bed, the other end of the base just contacts the lower loading plate, and the base and the lower loading plate are fixed together; the two first guide rails point to the direction of the test bin, two second guide rails are arranged at two ends of the base, the directions of the second guide rails and the first guide rails are mutually perpendicular, and second sliding blocks are arranged on the second guide rails;
the supporting mechanism comprises a lifting device, a sliding assembly is arranged at the bottom of the lifting device, and the lifting device can slide on the first guide rail in parallel under the action of the sliding assembly; one end of the first hydraulic cylinder is connected to the sliding assembly, and the other end of the first hydraulic cylinder is connected to the second sliding block;
and the anchoring and supporting mechanism is positioned on the lifting device and is used for drilling and anchoring and supporting the rock sample.
The rock body true triaxial test system based on 'first unloading-then anchoring-then disturbing' comprises a motor and a drill rod, wherein the motor is connected with the drill rod through an output shaft, spiral blades are arranged on the periphery of the drill rod, pore channels are arranged in the output shaft and the drill rod, a sealing shell with an air inlet hole is arranged on the output shaft, and a drill bit is arranged at the front end of the drill rod.
According to the rock body true triaxial test system based on 'first unloading, second anchoring and second disturbing', a nitrogen gas bottle is arranged on the lifting device near the motor, and the nitrogen gas bottle is used for providing nitrogen gas for the drill bit and cooling the drill bit rotating at a high speed.
The rock body true triaxial test system based on 'unloading before-anchoring after-disturbing' is characterized in that the nitrogen cylinder is connected with an air guide pipe, the other end of the air guide pipe is communicated with the air inlet hole, and the size of the hole passage of the air inlet hole is the same as that of the hole passage in the output shaft and the drill rod.
The rock body true triaxial test system based on 'first unloading-second anchoring-second disturbance' comprises an upper clamp, a lower clamp, a left clamp, a right clamp, a front clamp and a rear clamp, wherein the upper clamp is positioned between a rock sample and an upper loading plate, the lower clamp is positioned between the rock sample and a lower loading plate, the left clamp is positioned between the rock sample and a left loading plate, the right clamp is positioned between the rock sample and a right loading plate, the front clamp is positioned between the rock sample and a front loading plate, and the rear clamp is positioned between the rock sample and a rear loading plate.
The rock body true triaxial test system based on 'first unloading-then anchoring-then disturbing' comprises a sliding assembly and a lifting device, wherein the sliding assembly comprises four first sliding blocks, the four first sliding blocks are respectively arranged at the bottom of the lifting device, and the four first sliding blocks can relatively slide on the first guide rail in the direction towards/away from the test bin.
According to the rock mass true triaxial test system based on 'first unloading, second anchoring and second disturbing', acoustic emission sensors are adhered to the upper clamp, the lower clamp, the front clamp and the rear clamp; and a high-speed camera is arranged near the test chamber.
The rock body true triaxial test system based on 'first unloading-then anchoring-then disturbing' is characterized in that the lifting device comprises an upper bearing plate, a lower bearing plate and a telescopic piece positioned between the upper bearing plate and the lower bearing plate, and the anchoring support mechanism and the nitrogen cylinder are positioned on the upper bearing plate.
The invention also aims to provide a rock body true triaxial test method based on 'first unloading-then anchoring-then disturbing', which comprises the following steps:
placing a rock sample in a test chamber, installing acoustic emission sensors on an upper clamp, a lower clamp, a front clamp and a rear clamp, fixing a movable anchoring support device and a test bed together, and installing the movable anchoring support device;
step two, applying stress to the rock sample through a true triaxial testing machine, and passing through an upper loading plate and a lower loading plate, namely the maximum principal stress sigma in the Z-axis direction 1 Increasing to 1MPa; the median principal stress σ of the rock specimen, i.e. in the X-axis direction and the Y-axis direction, is likewise applied by means of the front and rear load plates and the left and right load plates 2 And minimum principal stress sigma 3 Increasing to 1MPa; then, the sigma is controlled at a certain speed by adopting a load control mode 1 、σ 2 、σ 3 Loading to a predetermined stress value;
step three, maintaining the intermediate principal stress sigma 2 Unloading σ at a constant rate 3 When the pressure is 0MPa, the left loading plate and the right loading plate, namely the corresponding clamps are disassembled in order to reappear the excavation unloading process;
opening a switch of a motor in the anchoring and supporting mechanism to enable the drill bit to rotate at a high speed, and providing nitrogen for the drill bit through a nitrogen cylinder; the lifting device is driven by the moving mechanism to approach towards the direction of the rock sample, and when the lifting device approaches to a certain distance, the rock sample enters a cutting stage, the drill bit contacts the rock sample and drills a preset position of the rock sample; after the drilling of the rock sample is finished, the first hydraulic cylinder is controlled to drive the drill bit to move in the opposite direction and exit from the cutting stage;
placing the epoxy resin anchoring agent into the rock sample drilled hole cut in the fourth step, inserting the anchor rod adhered with the strain gauge into the rock test drilled hole, respectively installing a tray and a tray nut, and stirring the epoxy resin anchoring agent by using the anchor rod to ensure that the anchor rod and the rock sample are fully adhered together;
step six, mounting a disturbance device, and carrying out disturbance through the disturbance device to keep the middle principal stress sigma 2 Is constant, the maximum principal stress sigma is increased at a certain rate by means of displacement control 1 To near the peak strength of the anchored rock sample, typically between 70% and 90% of the peak strength. Keeping the maximum principal stress at the moment, and applying low-frequency periodic disturbance load sigma to the surface of the rock sample through a dynamic actuator d (namely disturbance stress) until the anchored rock sample is damaged, and ending the experiment;
and seventhly, combining the test data and theoretical knowledge, and developing and analyzing.
In the step four, the anchoring modes comprise end anchoring, full-length anchoring and flexible anchoring.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention provides a rock mass true triaxial test system based on 'first unloading, second anchoring and second disturbing', which comprises a true triaxial test device, a disturbing device and a movable anchoring and supporting device.
The invention considers that the instability phenomenon can be generated after the underground mining rock mass is excavated and unloaded, and the anchor rod needs to be supported in time after excavation in order to solve the problem. Therefore, the mode that the true triaxial test device and the movable anchoring and supporting device are matched with each other is adopted, after the rock mass sample is unloaded through the true triaxial test device, the rock mass sample can be immediately anchored and supported through the movable anchoring and supporting device, and timely and effective supporting in actual engineering background is better met.
In addition, the movable anchoring and supporting device is used in combination with the true triaxial test device, for example, the movable anchoring and supporting device is fixed with a test bed of the true triaxial test device, and the movable anchoring and supporting device is used for carrying out drilling and supporting on a rock sample under a specific stress environment, namely before the rock sample is unstable after being unloaded.
The rock mass true triaxial test system and method based on 'unloading-anchoring-disturbing-then-disturbing' truly reproduce the whole stress process of 'three-dimensional initial static stress + unloading disturbance + drilling anchoring + external dynamic disturbance' of an underground engineering anchored rock mass, and overcome the defects of the prior first-anchoring-then-stressed rock mass anchoring destruction characteristic test; the method provides a theoretical basis for the follow-up study of the influence rule of different anchoring conditions on the mechanical behavior, peak strength and damage deformation characteristics of the deep mining engineering rock mass.
Drawings
The invention is further described with reference to the accompanying drawings:
FIGS. 1 (a) and (b) show the true triaxial test apparatus of the present invention perpendicular to σ 1 And σ 3 Plane, perpendicular to sigma 2 And σ 3 Loading a disturbance schematic diagram in a plane direction;
FIG. 2 is a schematic diagram of the test system of the present invention;
FIG. 3 isbase:Sub>A cross-sectional view A-A of FIG. 2;
FIG. 4 is a sectional view taken along line B-B of FIG. 2;
fig. 5 to 7 are schematic diagrams of three anchoring modes, namely end anchoring, full-length anchoring and flexible anchoring;
FIG. 8 is a flow chart of a method based on "unload before anchor after disturb" method;
in the figure: 1-upper loading plate, 2-lower loading plate, 3-right loading plate, 4-left loading plate, 5-rear loading plate, 6-front loading plate, 7-upper clamp, 8-lower clamp, 9-right clamp, 10-left clamp, 11-rear clamp, 12-front clamp, 13-rock sample, 14-static actuator, 15-disturbing rod, 16-connecting rod, 17-disturbing actuator, 18-true triaxial test bench, 19-fixing plate, 20-output shaft, 21-helical blade, 22-drill rod, 23-drill bit, 24-motor, 25-air inlet hole, 26-air guide tube, 27-nitrogen bottle, 28-upper bearing plate, 29-bolt nut, 30-first guide rail, 31-sealing shell, 32-first slider, 33-first hydraulic cylinder, 34-base, 35-second slider, 36-brake valve, 37-second guide rail, 38-second hydraulic cylinder, 39-anchor rod, 40-anchoring agent, 41-grooving, 42-strain sheet, 43-44-lead pad, 35-second slider, 36-brake valve, 36-brake disc, anti-abrasion disc, 1-48-moving stage, and S-stage.
Detailed Description
The invention provides a rock body true triaxial test system and a rock body true triaxial test method based on 'first unloading, then anchoring and then disturbing', and in order to make the advantages and the technical scheme of the invention clearer and clearer, the invention is further explained by combining with specific embodiments.
Referring to fig. 1 to 4, the rock body true triaxial test system based on 'first unloading-then anchoring-then disturbing' comprises a true triaxial test device, wherein the true triaxial test device comprises a test chamber, a loading mechanism and a clamp assembly, the loading mechanism is used for applying load to a rock sample in the test chamber, the test chamber is of a frame structure and is positioned on a test bed, the rock sample 13 is placed in the test chamber, and the rock sample is a cubic rock sample with the size of 100mm x 100 mm.
The loading mechanism comprises a loading unit, an upper loading plate 1, a lower loading plate 2, a left loading plate 4, a right loading plate 3, a front loading plate 6 and a rear loading plate 5; the clamp assembly comprises an upper clamp 7, a lower clamp 8, a left clamp 10, a right clamp 9, a front clamp 12 and a rear clamp 11, wherein the upper clamp is positioned between a rock sample and an upper loading plate, the lower clamp is positioned between the rock sample and a lower loading plate, the left clamp is positioned between the rock sample and a left loading plate, the right clamp is positioned between the rock sample and a right loading plate, the front clamp is positioned between the rock sample and the front loading plate, and the rear clamp is positioned between the rock sample and the rear loading plate.
As a main innovation point of the invention, the system further comprises a disturbance device and a movable anchoring and supporting device, wherein the disturbance device comprises a first disturbance mechanism and a second disturbance mechanism, the first disturbance mechanism is arranged on the upper loading plate and the lower loading plate which are positioned at the maximum main stress, and the second disturbance mechanism is arranged on the front loading plate and the rear loading plate which are positioned at the middle stress;
the first disturbance mechanism and the second disturbance mechanism respectively comprise a static actuator 14, a disturbance rod 15, a connecting rod 16 and a disturbance actuator 17, the two static actuators are respectively installed on the upper loading plate and the right loading plate, and the two disturbance rods, the connecting rod and the disturbance actuator are respectively installed on the lower loading plate and the left loading plate; the disturbance actuator, the connecting rod and the disturbance rod are sequentially connected, and the other end of the disturbance rod is in contact with the surface of the rock sample.
The working principle of the first disturbing mechanism and the second disturbing mechanism is as follows:
the dynamic disturbance load with low frequency is applied to the surface of the sample through the dynamic actuator, the dynamic disturbance influence of blasting (the blasting shock wave is attenuated and then converted into low-frequency cyclic seismic wave) after mining, adjacent working face mining, ore removal or mechanical operation on the engineering surrounding rock is simulated until the anchored rock sample is damaged, and the experiment is finished. In the selection of test dynamic disturbance parameters, the selection of the disturbance amplitude value is based on the occurrence of fracture of a sample, and the trial and estimation are required in the test process; three types of disturbance frequencies, namely 1HZ, 3HZ and 5HZ are selected; the direction of the disturbance is primarily defined as whether the disturbance source is applied parallel to the direction of the maximum principal stress or parallel to the direction of the intermediate principal stress.
The movable anchoring and supporting device comprises a moving mechanism, a supporting mechanism and an anchoring and supporting mechanism, wherein the moving mechanism comprises a base, a first guide rail and a first hydraulic cylinder, one end of the base is aligned with the true triaxial test bed 18, the other end of the base is just in contact with the lower loading plate, and the base 34 and the lower loading plate are fixed together through bolts and nuts 29; the first guide rails 30 are located on the base and are arranged in parallel, the two first guide rails point to the direction of the test chamber, the first guide rails are divided into two stages which are a moving stage S2 and a cutting stage S1 respectively, when the first guide rails move, the anchoring supporting mechanism slides towards the direction of the test chamber under the action of the moving mechanism, and when the first guide rails move, the anchoring supporting mechanism can be unfolded to perform cutting work.
Two second guide rails are arranged at two ends of the base, the directions of the second guide rails 37 are perpendicular to the direction of the first guide rail 30, and a second sliding block 35 and a brake valve 36 are arranged on the second guide rails.
The supporting mechanism comprises a lifting device, a sliding assembly is arranged at the bottom of the lifting device, and the lifting device can slide on the first guide rail in parallel under the action of the sliding assembly; one end of the first hydraulic cylinder 33 is connected to the sliding assembly, and the other end of the first hydraulic cylinder is connected to the second sliding block; the sliding of the lifting device is controlled by controlling the first hydraulic cylinder 33.
Specifically, the sliding assembly includes four first sliding blocks 32, the four first sliding blocks are respectively installed at the bottom of the lifting device, and the four first sliding blocks can relatively slide on the first guide rail in a direction towards/away from the test chamber.
The lifting device comprises an upper bearing plate 28, a lower bearing plate and a telescopic part positioned between the upper bearing plate and the lower bearing plate, wherein the telescopic part can also be a second hydraulic cylinder 38, and the upper bearing plate 28 is driven to ascend or descend by the telescopic part.
The anchoring support mechanism and the nitrogen cylinder 27 are positioned on the upper bearing plate.
And the anchoring and supporting mechanism is positioned on the lifting device and is used for drilling and anchoring and supporting the rock sample. The anchoring support mechanism comprises a motor 24, an anchor rod 39, a drill rod, a fixing plate 19, an anchoring agent 40, a cutting groove 41, a strain gauge 42, a wiring terminal 43, a lead 44, an end tray 45, an anti-abrasion gasket 46, a tray nut 47, a pressure-yielding ring 48 and a pore channel 49, wherein the motor is connected with the drill rod through an output shaft 20, a spiral blade 21 is arranged on the periphery of the drill rod, the pore channel is arranged inside the output shaft and the drill rod 22, a sealing shell 31 with an air inlet hole is arranged on the output shaft, and a drill bit 23 is arranged at the front end of the drill rod. The nitrogen cylinder is connected with an air duct 26, the other end of the air duct is communicated with the air inlet hole 25, and the size of the hole channel of the air inlet hole is the same as that of the hole channel inside the output shaft and the drill rod.
Preferably, the acoustic emission sensors are adhered to the upper clamp, the lower clamp, the front clamp and the rear clamp; and a high-speed camera is arranged near the test chamber.
Preferably, the size of the anchor rod is 120mm, and the diameter of the anchor rod is 6 mm. The epoxy resin anchoring agent is firstly put into a stressed rock drill hole, then the strain gauge is stuck into a cutting groove of the deformed steel bar anchor rod, and two leads are connected through a connecting terminal. Inserting the anchor rod into the stressed rock sample borehole, respectively installing a metal tray and a tray nut with the dimensions of 20mm multiplied by 1mm, stirring the anchoring agent by the anchor rod for 30s, fully bonding the anchor rod and the rock sample, and applying pre-tightening torque to the tray nut by adopting a mechanical torque wrench. As shown in fig. 5 to 7, three anchoring modes are selected, which are end anchoring, full length anchoring and flexible anchoring, wherein the end anchoring needs to inject an anchoring agent at a position close to the anchoring end (the length of the anchoring agent accounts for about 1/4-1/3 of the total length of the anchor rod body), the full length anchoring needs to inject the anchoring agent at the full length of the anchor rod hole, and the flexible anchoring refers to anchoring by using the anchor rod with a yielding function, and can be realized by installing an elastic sleeve between the anchoring section and the tray.
Preferably, the output shaft is in threaded connection with the drill rod.
The helical blade can realize automatic waste rock discharge at drilling process, and high strength screw-thread steel stock length is slightly bigger than the size of rock sample, and the diameter of stock is not more than the diameter of drilling.
Furthermore, one end of the base is aligned with the true triaxial test bed, and the other end of the base is in contact with the lower loading plate. When the bearing plate of the lifting device enters a cutting stage, the drilling device starts to drill the rock sample, and when the bearing plate contacts the track bearing base sliding block, the rock sample is completely drilled through.
Preferably, the high-speed camera placement position can clearly record the test process; and 4 acoustic emission sensors are selected and respectively attached to the clamps in the directions of the maximum main stress and the middle main stress of the rock sample.
Furthermore, the motor models are ACSM180-G19015 numerical control servo motors, so that the rotating speed of the motor can be controlled, and the steering direction of the motor can be controlled.
The working method of the rock body true triaxial test system based on 'first unloading, then anchoring and then disturbing' is further explained in the following by combining the rock body true triaxial test system.
As shown in fig. 8, the method specifically includes the following steps:
firstly, placing a rock sample on a true triaxial testing machine, and adjusting the position to be straightened; and fixing the clamp between the rock sample and the loading plate, and correcting the position of the clamp. And (3) mounting acoustic emission sensors, and respectively sticking 4 acoustic emission sensors on the clamps in the directions of the maximum main stress and the middle main stress, wherein the positions of the acoustic emission sensors are close to the rock sample. A high-speed camera is placed to ensure that the test process can be clearly seen.
And installing a movable anchoring support device, fixing the base and the true triaxial test bed by using bolts and nuts, aligning one end of the base with the true triaxial test bed, and just contacting the other end of the base with a loading plate (lower loading plate) with the maximum main stress. And then, four sliding blocks of the lifting device are arranged on the first guide rail, wherein two sliding blocks are respectively connected with 2 first hydraulic cylinders fixed on the base. Fix drilling servo motor on scissors fork elevating gear's bearing plate through 2 fixed plates and bolt and nut. Then, the output shaft is connected with a drill rod with a helical blade through threads, and pore channels are arranged in the output shaft and the drill rod. The output shaft provided with the sealing shell is arranged on the drilling motor, and then the drill bit is arranged at the front end of the drill rod, so that the installation of the anchoring support mechanism is completed. Install the nitrogen cylinder on elevating gear's bearing plate, be convenient for to the local cooling of cutting drill bit.
Secondly, controlling the loading in the direction of the maximum principal stress of the rock sample, namely the Z-axis direction, through the displacement of the true triaxial testing machine, so that the maximum principal stress sigma is enabled to be 1 Increasing to 1MPa. The rock sample is loaded with the mean principal stress and the minimum principal stress directions, i.e. the Y-axis and X-axis directions, also using displacement control, such that sigma 2 、σ 3 And also to 1MPa. Then, the sigma is controlled at a certain speed by adopting a load control mode 1 、σ 2 、σ 3 Loading to a predetermined stress value.
Thirdly, the intermediate principal stress sigma is kept through the load control of the true triaxial test device 2 Is unloaded at a constant rate 3 To 0MPa to reproduceAnd (5) excavating and unloading. Then, the sigma is adjusted 3 The two loading plates and the clamp in the direction are slowly disassembled.
And fourthly, controlling the guide rail and the second hydraulic cylinder to enable the cutting drill bit to be aligned to the designed drilling position of the rock sample. And opening a power switch of a drilling motor to enable the motor to drive the cutting drill bit to rotate at a high speed, and then opening a valve of a nitrogen gas bottle to enable nitrogen gas to enter an air inlet through an air guide pipe and reach the position of the cutting drill bit through a pore passage. And controlling two first hydraulic cylinders on the guide rail bearing base to drive the sliding blocks of the lifting device to slide on the two guide rails, so that the anchoring and supporting mechanism slowly approaches to the rock sample, and when the anchoring and supporting mechanism slides into the cutting stage of the rail bearing base, the drill bit is contacted and drills the rock sample. When the lower bearing plate of the lifting device contacts the sliding block of the base, the movement is stopped, and at the moment, the anchoring and supporting mechanism breaks through the rock sample. And then, controlling the hydraulic oil cylinder to drive the cutting drill bit to move in the opposite direction, and when the lifting device slides out of the cutting stage, completely withdrawing the rock sample by the anchoring and supporting mechanism. And when the piston rod of the hydraulic oil cylinder on the guide rail bearing base is completely retracted to the cylinder barrel of the piston cylinder, the guide rail stops moving. And finally, closing the drilling motor power supply and the nitrogen cylinder valve.
Fifthly, firstly putting the epoxy resin anchoring agent into the stressed rock drilled hole, then inserting the high-strength deformed steel bar anchor rod adhered with the strain gauge into the stressed rock sample drilled hole, respectively installing the metal tray and the tray nut, stirring the anchoring agent for 30s by using the anchor rod, fully adhering the anchor rod and the rock sample, and applying pre-tightening torque to the tray nut by using a mechanical torque wrench.
And sixthly, mounting a true triaxial disturbance device, namely respectively mounting two static actuators on the loading plates in the directions of the maximum principal stress and the middle principal stress, and simultaneously respectively mounting two groups of disturbance rods, linkage rods and disturbance actuators on the other group of loading plates with the maximum principal stress and the middle principal stress, wherein the mounting is shown in figure 1. Continuously maintaining the intermediate principal stress sigma by means of load control 2 Is constant, and increases sigma at a certain rate by means of displacement control 1 To near the peak strength of the anchored rock sample,typically between 70% and 90% of the peak intensity. Maintaining the maximum principal stress at this time, applying a low-frequency periodic disturbance load sigma to the sample surface by a dynamic actuator d (i.e., the disturbance stress) until the anchored rock specimen fails, the experiment is ended.
And seventhly, analyzing the experimental result in detail according to the stress-strain curve of the sample, the acoustic emission parameters, the failure mode, the fragment distribution characteristics and the like.
The structures and working principles of the static actuator, the disturbance actuator and the motor are realized by taking the prior art as reference.
Parts which are not described in the invention can be realized by adopting or referring to the prior art.
Although terms such as upper load plate 1, lower load plate 2, right load plate 3, and left load plate 4 are used more often herein, the possibility of using other terms is not excluded. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed as being without limitation to any additional limitations that may be imposed by the spirit of the present invention.
It is further understood that the specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (10)
1. A rock mass true triaxial test system based on 'first unloading, second anchoring and second interference' comprises a true triaxial test device, wherein the true triaxial test device comprises a test bin, a loading mechanism and a clamp assembly, the test bin is of a frame structure and is positioned on a test bed, a rock sample is placed in the test bin, and the loading mechanism comprises a loading unit and upper, lower, left, right, front and rear loading plates; the method is characterized in that:
the device also comprises a disturbance device and a movable anchoring and supporting device;
the disturbance device comprises a first disturbance mechanism and a second disturbance mechanism, wherein the first disturbance mechanism is arranged on an upper loading plate and a lower loading plate which are positioned at the maximum main stress, and the second disturbance mechanism is arranged on a front loading plate and a rear loading plate which are positioned at the middle stress;
the first disturbance mechanism and the second disturbance mechanism respectively comprise static actuators, disturbance rods, connecting rods and disturbance actuators, the two static actuators are respectively installed on the upper loading plate and the right loading plate, and the two disturbance rods, the connecting rods and the disturbance actuators are respectively installed on the lower loading plate and the left loading plate; the disturbance actuator, the connecting rod and the disturbance rod are sequentially connected, and the other end of the disturbance rod is in contact with the surface of the rock sample;
the movable anchoring and supporting device comprises a moving mechanism, a supporting mechanism and an anchoring and supporting mechanism, wherein the moving mechanism comprises a base, a first guide rail and a first hydraulic cylinder, one end of the base is aligned with the test bed, the other end of the base just contacts the lower loading plate, and the base and the lower loading plate are fixed together; the two first guide rails point to the direction of the test bin, two second guide rails are arranged at two ends of the base, the directions of the second guide rails and the first guide rails are mutually perpendicular, and second sliding blocks are arranged on the second guide rails;
the supporting mechanism comprises a lifting device, a sliding assembly is arranged at the bottom of the lifting device, and the lifting device can slide on the first guide rail in parallel under the action of the sliding assembly; one end of the first hydraulic cylinder is connected to the sliding assembly, and the other end of the first hydraulic cylinder is connected to the second sliding block;
and the anchoring and supporting mechanism is positioned on the lifting device and is used for drilling and anchoring and supporting the rock sample.
2. The rock mass true triaxial test system based on 'first unloading-then anchoring-then disturbing' according to claim 1, wherein: the anchoring support mechanism comprises a motor and a drill rod, the motor is connected with the drill rod through an output shaft, spiral blades are arranged on the periphery of the drill rod, pore channels are formed in the output shaft and the drill rod, a sealing shell with an air inlet hole is arranged on the output shaft, and a drill bit is arranged at the front end of the drill rod.
3. The rock mass true triaxial test system based on 'first unloading-then anchoring-then disturbing' according to claim 2, wherein: and a nitrogen bottle is arranged on the lifting device near the motor, and is used for providing nitrogen for the drill bit and cooling the drill bit rotating at a high speed.
4. The rock mass true triaxial test system based on 'first unloading-then anchoring-then disturbing' according to claim 3, wherein: the nitrogen cylinder be connected with the air duct, the other end of air duct with the inlet port intercommunication, the pore of inlet port the same with the inside pore size of output shaft and drilling rod.
5. The rock mass true triaxial test system based on 'first unloading-then anchoring-then disturbing' as claimed in claim 3, wherein: the clamp assembly comprises an upper clamp, a lower clamp, a left clamp, a right clamp, a front clamp and a rear clamp, wherein the upper clamp is positioned between the rock sample and an upper loading plate, the lower clamp is positioned between the rock sample and a lower loading plate, the left clamp is positioned between the rock sample and a left loading plate, the right clamp is positioned between the rock sample and a right loading plate, the front clamp is positioned between the rock sample and the front loading plate, and the rear clamp is positioned between the rock sample and the rear loading plate.
6. The rock mass true triaxial test system based on 'first unloading-then anchoring-then disturbing' according to claim 1, wherein: the sliding assembly comprises four first sliding blocks, the four first sliding blocks are respectively arranged at the bottom of the lifting device, and the four first sliding blocks can relatively slide on the first guide rail in the direction towards/away from the test chamber.
7. The rock mass true triaxial test system based on 'first unloading-then anchoring-then disturbing' according to claim 5, wherein: acoustic emission sensors are adhered to the upper clamp, the lower clamp, the front clamp and the rear clamp; and a high-speed camera is arranged near the test chamber.
8. The rock mass true triaxial test system based on 'first unloading-then anchoring-then disturbing' according to claim 3, wherein: the lifting device comprises an upper bearing plate, a lower bearing plate and a telescopic piece positioned between the upper bearing plate and the lower bearing plate, and the anchoring support mechanism and the nitrogen cylinder are positioned on the upper bearing plate.
9. A rock mass true triaxial test method based on 'first unloading-second anchoring-second disturbing', which is characterized in that the rock mass true triaxial test system based on 'first unloading-second anchoring-second disturbing' as claimed in any one of claims 1 to 8 is adopted, and the method comprises the following steps:
placing a rock sample in a test chamber, installing acoustic emission sensors on an upper clamp, a lower clamp, a front clamp and a rear clamp, fixing a movable anchoring support device and a test bed together, and installing the movable anchoring support device;
step two, applying stress to the rock sample through a true triaxial testing machine, and passing through an upper loading plate and a lower loading plate, namely the maximum principal stress sigma in the Z-axis direction 1 Increasing to 1MPa; the median principal stress σ of the rock specimen, i.e. in the X-axis direction and the Y-axis direction, is likewise applied by means of the front and rear load plates and the left and right load plates 2 And minimum principal stress sigma 3 Increasing to 1MPa; then, the sigma is controlled at a certain speed by adopting a load control mode 1 、σ 2 、σ 3 Loading to a predetermined stress value;
step three, maintaining the intermediate principal stress sigma 2 Unloading at constant rateσ 3 When the pressure is 0MPa, the left and right loading plates, namely the corresponding clamps, are disassembled in order to reappear the excavation unloading process;
opening a switch of a motor in the anchoring and supporting mechanism to enable the drill bit to rotate at a high speed, and providing nitrogen for the drill bit through a nitrogen cylinder; the lifting device is driven by the moving mechanism to approach towards the direction of the rock sample, and when the lifting device approaches to a certain distance, the rock sample enters a cutting stage, the drill bit contacts the rock sample and drills a preset position of the rock sample; after the drilling of the rock sample is finished, the first hydraulic cylinder is controlled to drive the drill bit to move in the opposite direction and exit from the cutting stage;
placing the epoxy resin anchoring agent into the rock sample drilled hole cut in the fourth step, inserting the anchor rod adhered with the strain gauge into the rock test drilled hole, respectively installing a tray and a tray nut, and stirring the epoxy resin anchoring agent by using the anchor rod to ensure that the anchor rod and the rock sample are fully adhered together;
step six, mounting a disturbance device, and carrying out disturbance through the disturbance device to keep the intermediate principal stress sigma 2 Is constant, the maximum principal stress sigma is increased at a certain rate by means of displacement control 1 To near peak strength of the anchored rock sample, typically between 70% and 90% of the peak strength; keeping the maximum principal stress at the moment, and applying low-frequency periodic disturbance load sigma to the surface of the rock sample through a dynamic actuator d Until the anchored rock sample is damaged, ending the experiment;
and seventhly, combining the test data and theoretical knowledge, and developing and analyzing.
10. The rock mass true triaxial test method based on 'first unloading-then anchoring-then disturbing' as claimed in claim 9, wherein: in the fourth step, the anchoring mode comprises end anchoring, full-length anchoring and flexible anchoring.
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