CN117288563B

CN117288563B - Ultralow frequency cyclic load creep test system and test method

Info

Publication number: CN117288563B
Application number: CN202311263545.7A
Authority: CN
Inventors: 李银平; 施锡林; 董志凯; 刘元玺; 黄思; 陈祥胜; 马洪岭; 赵阿虎; 李小平; 陈海军; 丁根荣
Original assignee: Wuhan Institute of Rock and Soil Mechanics of CAS
Current assignee: Wuhan Institute of Rock and Soil Mechanics of CAS
Priority date: 2023-09-27
Filing date: 2023-09-27
Publication date: 2024-04-30
Anticipated expiration: 2043-09-27
Also published as: CN117288563A

Abstract

The disclosure relates to the technical field of cyclic load creep test, in particular to an ultralow frequency cyclic load creep test system and a test method. The device comprises a triaxial pressure chamber, an axial pressure module, a confining pressure module and an automatic oil return and supplement device, wherein the triaxial pressure chamber comprises a pressure chamber body and a piston, the piston is used for limiting a confining pressure cavity and an axial pressure cavity in the pressure chamber body, and the piston is used for applying axial pressure to a sample; the shaft pressure module is connected with the shaft pressure interface, and the first pressurizing cylinder is used for increasing the load pressure released by the first load generating device; the confining pressure module is connected with the oil injection and discharge interface, and the second pressurizing cylinder is used for increasing the load pressure released by the second load generating device; and the automatic oil removing and supplementing device is used for supplementing oil or removing oil to the first load generating device and/or the second load generating device. The method and the device realize the long-term stable ultralow frequency load effect, so that test data are more accurate, triaxial test requirements can be met, and stress suitable for actual occurrence conditions of salt cavern surrounding rock is provided.

Description

Ultralow frequency cyclic load creep test system and test method

Technical Field

The disclosure relates to the technical field of cyclic load creep test, in particular to an ultralow frequency cyclic load creep test system and a test method.

Background

The rock salt becomes an ideal medium for petroleum and natural gas storage, compressed air energy storage and other engineering due to its low permeability, good creep property and damage self-repairing property. When the salt cavern gas storage runs, the internal pressure of the cavity can rise and fall along with the gas injection and production process, so that the cavity surrounding rock is subjected to the action of cyclic load for a long time.

At present, the creep mechanism and rule of the salt rock under the long-term action of the ultralow frequency cyclic load are still studied freshly, creep mechanism and parameters can only be achieved by means of constant load creep achievements, and long-term creep test research under the ultralow frequency load is forced. However, the existing creep deformation instrument can not meet the requirement of long-term creep deformation test of the rock under low-frequency cyclic load, mainly reflects the creep deformation test instruments at home and abroad, mostly adopts electrohydraulic servo control, frequently encounters the problems of power failure, electronic sensor faults and the like in the long-term test process, seriously influences the accuracy of test data, even interrupts the creep deformation instrument which fails to adopt lever weight type loading, adopts constant load loading, and is difficult to stably develop creep deformation research under ultralow-frequency cyclic load. Moreover, the existing creep testing machine can only provide uniaxial loading conditions, and cannot meet triaxial test and high-temperature requirements, so that stress and temperature conditions suitable for actual occurrence conditions of salt cavern surrounding rock cannot be provided.

Based on the reasons, the invention needs to provide an ultralow frequency cyclic load creep test system for systematically developing the creep behavior of the salt rock under the ultralow frequency cyclic load.

Disclosure of Invention

The present disclosure is directed to solving at least one of the technical problems existing in the prior art or related art.

To this end, in a first aspect of the present disclosure there is provided an ultra-low frequency cyclic load creep test system comprising:

The triaxial pressure chamber comprises a pressure chamber body and a piston, wherein the piston is used for limiting a confining pressure cavity and a shaft pressure cavity in the pressure chamber body, the confining pressure cavity is provided with an oil injection and discharge interface, an oil injection and discharge interface and a sample mounting position, the sample mounting position is used for bearing the sample in the confining pressure cavity, the oil injection and discharge interface is arranged at one end, close to the shaft pressure cavity, of the confining pressure cavity, and the oil injection and discharge interface is arranged at the other end of the confining pressure cavity;

The shaft pressure cavity is provided with a shaft pressure interface, the shaft pressure interface is connected with the high pressure cavity of the pressurizing cylinder, the shaft pressure interface is used for inputting the pressure liquid into the shaft pressure cavity, and the piston is used for applying axial pressure to the sample;

the axle pressure module is connected with the axle pressure interface and comprises a first load generating device and a first pressurizing cylinder, wherein the first pressurizing cylinder is used for increasing load pressure released by the first load generating device;

The confining pressure module is connected with the oil injection and discharge interface and comprises a second load generating device and a second pressurizing cylinder, wherein the second pressurizing cylinder is used for increasing the load pressure released by the second load generating device;

and the automatic oil removing and supplementing device is used for supplementing oil or removing oil to the first load generating device and/or the second load generating device.

In a possible embodiment, the first load generating device and the second load generating device are identical in structure, and comprise an oil pressure load conversion module and a cyclic load function module, wherein,

The oil pressure load conversion module comprises a mounting plate, a movable oil cylinder and a fixed piston, wherein the movable oil cylinder sleeve is arranged on the fixed piston, a first oil inlet and outlet channel is arranged in the mounting plate, at least two oil inlet and outlet interfaces are arranged in the first oil inlet and outlet channel, one end of the fixed piston is connected with the mounting plate, a second oil inlet and outlet channel is arranged in the fixed piston, one end of the second oil inlet and outlet channel is communicated with the first oil inlet and outlet channel, and the opposite end of the second oil inlet and outlet channel is communicated with the interior of the movable oil cylinder;

The circulating load function module comprises a driving part and an adjusting part, and the driving part is connected with the movable oil cylinder; the adjusting part is connected with the driving part and is used for adjusting the acting force applied by the driving part to the movable oil cylinder.

In a possible implementation manner, the driving part comprises a suspension rod, a fulcrum frame and a connecting frame, the suspension rod is connected with the fulcrum frame, the suspension rod can rotate relative to a fulcrum of the fulcrum frame, the fulcrum frame is arranged on the mounting plate, the fulcrum frame limits the suspension rod to a first cantilever and a second cantilever through the fulcrum points, one end of the connecting frame is hinged with the second cantilever, and the opposite end of the connecting frame is hinged with one end, close to the suspension rod, of the movable oil cylinder.

In a possible embodiment, the adjusting part comprises a displacement element, which is connected to the first cantilever and which can be displaced in the direction of extension of the first cantilever, and a drive element for driving the displacement element.

In a possible implementation manner, the driving piece comprises a driving motor, a screw rod and a limiting piece, the moving piece is connected with the screw rod, the screw rod is arranged along the extending direction of the first cantilever, the driving motor is arranged opposite to the position of the fulcrum frame, the driving motor is used for enabling the screw rod to rotate to drive the moving piece to be close to or far away from the driving motor, the limiting piece is arranged at two ends of the screw rod, and the limiting piece is used for limiting the moving range of the moving piece.

In a possible implementation manner, the pressurizing cylinder comprises a cylinder body and a regulating piston, the regulating piston is arranged in the cylinder body, the regulating piston limits the cylinder body into a first chamber and a second chamber, the pressure of the first chamber is larger than that of the second chamber, a first channel is arranged on one side, away from the second chamber, of the first chamber, a connecting valve is arranged on the outer portion of the cylinder body, a second channel is arranged on one side, away from the first chamber, of the second chamber, the second channel is communicated with an oil outlet end of the first oil inlet and outlet channel, and an air inlet and outlet hole is arranged on one side, close to the first chamber, of the second chamber.

In a possible embodiment, a balance cavity is further arranged in the pressure chamber body, the balance cavity is arranged between the axial pressure cavity and the confining pressure cavity, the confining pressure cavity is communicated with the balance cavity through a piston channel, and the piston channel is arranged inside the piston.

In a possible embodiment, the piston is adapted to define the balancing chamber as a first chamber and a second chamber, wherein,

The first chamber is provided with a balance chamber exhaust hole which is used for exhausting air in the first chamber;

The second chamber is close to the shaft pressure cavity, and the pressure liquid in the confining pressure cavity enters the second chamber through the piston channel.

In one possible embodiment, a heating element for adjusting the temperature of the pressure fluid and a temperature sensor for monitoring the temperature of the pressure fluid are arranged around the sample mounting point.

In a second aspect of the present disclosure, a test method for an ultralow frequency cyclic load creep test is provided, including the steps of:

Discharging air in the first chamber of each pressurizing cylinder, injecting hydraulic oil into the high-pressure port of each pressurizing cylinder, completely moving the piston to one end of the second chamber, and fully storing the hydraulic oil in the first chamber; completely exhausting air in the shaft pressing cavity;

Sealing the sample, mounting a circumferential strain gauge and an axial strain gauge on the sample, and mounting the sample on the sample mounting position in the confining pressure cavity;

The probe positions of the displacement sensors are adjusted to leave enough deformation measurement allowance;

closing the triaxial pressure chamber, and filling the confining pressure cavity with hydraulic oil;

Filling hydraulic oil into an oil tank of the automatic oil removing and supplementing device, opening the automatic oil removing and supplementing device, and automatically monitoring the oil quantity of the first load generating device and the second load generating device by the automatic oil removing and supplementing device and performing oil supplementing or oil removing operation;

and (3) regulating an average load value of a target circulating load of the terminal control switchboard, setting a waveform of the target circulating load, and starting loading of the ultralow frequency circulating load creep test system according to the target circulating load.

Compared with the prior art, the method at least comprises the following beneficial effects: the piston of the present disclosure defines the pressure chamber body into a confining pressure cavity and an axial pressure cavity, and load pressure conveyed by the load generating device enters the axial pressure cavity through the axial pressure interface to apply acting force to the piston, so as to apply axial pressure to the sample; the confining pressure cavity is provided with an oil injection and discharge interface, a confining pressure interface and a sample mounting position, pressure liquid enters the confining pressure cavity through the confining pressure interface to apply confining pressure to a sample on the sample mounting position, and the triaxial test requirements can be met through the technical scheme of the present disclosure, and stress suitable for the actual occurrence condition of the salt cavern surrounding rock is provided; and this disclosure realizes the supply of ultralow frequency pressure through oil pressure load conversion module and cyclic loading function module, its oil pressure load conversion module includes the mounting panel, movable cylinder and piston, the mounting panel is inside to be provided with first business turn over oil passageway, this first business turn over oil passageway of disclosure has two business turn over oil interface at least and installs the pressure chamber of oil liquid feed system and installation thing appearance, the piston sets up inside the movable cylinder, and the piston is inside to be provided with second business turn over oil passageway, second business turn over oil passageway one end and first business turn over oil passageway intercommunication, relative other end and the inside intercommunication of movable cylinder, be connected with movable cylinder through the drive division of cyclic loading function module and make movable cylinder and piston cooperation produce pressure supply and pass to the pressure chamber, utilize the effort that regulation portion regulation drive division was applyed to the movable cylinder, thereby realize long-term stable ultralow frequency load's effect, realize long-term stable ultralow frequency load effect, make test data more accurate.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the disclosure and together with the description, serve to explain the principles of the disclosure.

In order to more clearly illustrate the embodiments of the present disclosure or the solutions in the prior art, the drawings that are required for the description of the embodiments or the prior art will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the exemplary embodiments. The drawings are only for purposes of illustrating exemplary embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to designate like parts throughout the figures. In the accompanying drawings:

FIG. 1 is a schematic diagram of the structure of an axial compression module, a triaxial plenum, a confining pressure module and an automatic oil removal and replenishment device of the present disclosure;

FIG. 2 is one of the schematic structural diagrams of the triaxial pressure chambers of the present disclosure;

FIG. 3 is a second schematic diagram of the triaxial plenum of the present disclosure;

FIG. 4 is a schematic diagram of the structure of a sample of the present disclosure;

FIG. 5 is a schematic structural view of a first load generating device and a second load generating device of the present disclosure;

FIG. 6 is a schematic structural view of an adjustment portion of the present disclosure;

FIG. 7 is a schematic diagram of the oil pressure load conversion module of the present disclosure;

fig. 8 is a schematic structural view of a first and second booster cylinders of the present disclosure.

The correspondence between the reference numerals and the component names in fig. 1 to 8 is:

100-sample; balance chamber vent 300; axial displacement sensor 400, annular displacement sensor 500;

1-a triaxial pressure chamber; 11-a pressure chamber body; 111-confining pressure cavity; 112-axial compression chamber; 113-an oil filling and draining interface; 114-gas injection and exhaust interface; 115—sample mounting site; 116-an axial compression interface; 117-balancing chamber; 118-confining pressure interface; 12-a piston; 119-feet; 120-limiting balance plates; 121-a piston channel;

21-a first load generating device; 22-a first booster cylinder; 91-cylinder; 911-a first chamber; 912-a second chamber; 913—a first channel; 914-second pass; 915-air inlet and outlet holes; 916-a third chamber; 917-fourth chamber; 92-adjusting the piston; 31-a second load generating device;

32-a second booster cylinder; 101-assembling plates; 102-a movable oil cylinder; 103-fixing the piston; 104-a first oil inlet and outlet passage; 105-oil inlet and outlet ports; 106-a second oil inlet and outlet passage; 107-a driving part; 71-a suspension rod; 710—a first cantilever; 711-a second cantilever; 712-balance weight set; 713-a first counterweight; 714-a second counterweight; 72-supporting point frame; 73-a connecting frame; 108-an adjusting part; 81-a moving member; 821-driving a motor; 822-a screw rod; 823-limiting members 823;

4-an automatic oil removing and supplementing device.

Detailed Description

In order that the above objects, features and advantages of the present disclosure may be more clearly understood, a further description of aspects of the present disclosure will be provided below. It should be noted that, without conflict, the embodiments of the present disclosure and features in the embodiments may be combined with each other.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure, but the present disclosure may be practiced otherwise than as described herein; it will be apparent that the embodiments in the specification are only some, but not all, embodiments of the disclosure.

Based on the above, the embodiment of the disclosure provides an ultralow frequency cyclic load creep test system, which realizes a long-term stable ultralow frequency load effect, enables test data to be more accurate, can meet triaxial test requirements, and provides stress suitable for actual occurrence conditions of salt cavern surrounding rock.

The ultra-low frequency cyclic load creep test system is described in detail below by specific examples:

referring to fig. 1 to 8, in a first aspect of the present disclosure, there is provided an ultralow frequency cyclic load creep test system, including a triaxial pressure chamber 1, an axial pressure module, a confining pressure module and an automatic oil withdrawal and compensation device 4, the triaxial pressure chamber 1 of the present disclosure includes a pressure chamber body 11 and a piston 12, the piston 12 is used for defining a confining pressure cavity 111 and an axial pressure cavity 112 inside the pressure chamber body 11, the confining pressure cavity 111 has an oil injection and discharge interface 113, an air injection and discharge interface 114 and a sample 100 mounting position 115, the sample mounting position 115 is used for carrying the sample 100 in the confining pressure cavity 111, the air injection and discharge interface 114 is disposed at one end of the confining pressure cavity 111 close to the axial pressure cavity 112, and the oil injection and discharge interface 113 is disposed at the other end of the confining pressure cavity 111; the axial pressure cavity 112 is provided with an axial pressure interface 116, the axial pressure interface 116 is connected with a first cavity, namely a high pressure cavity, of the pressurizing cylinder 9, the axial pressure interface 116 is used for inputting the pressure liquid into the axial pressure cavity 112, and the piston 12 is used for applying axial pressure to the sample 100; the axle pressure module is connected to the axle pressure interface 116, and comprises a first load generating device 21 and a first booster cylinder 22, wherein the first booster cylinder 22 is used for increasing the load pressure released by the first load generating device 21; the confining pressure module is connected to the oil filling and discharging interface 113, and comprises a second load generating device 31 and a second pressurizing cylinder 32, wherein the second pressurizing cylinder 32 is used for increasing the load pressure released by the second load generating device 31; the automatic oil removing and supplementing device 4 is used for supplementing oil or removing oil to the first load generating device 21 and/or the second load generating device 31

As shown in fig. 3, the triaxial pressure chamber 1 of the present disclosure functions to apply a target stress to a rock specimen 100. The present disclosure may achieve target loading conditions by applying various combinations of hydrostatic and deflection stresses to the test specimen 100. Specifically, the piston 12 of the present disclosure defines the space inside the pressure chamber body 11 into a confining pressure chamber 111 and an axial pressure chamber 112, wherein the axial pressure chamber 112 is disposed at the top of the pressure chamber body 11, and in some embodiments, a portion of the axial pressure chamber 112 is formed of a separate structure, which is connected to the pressure chamber body 11 by bolts, and its form and function are unchanged, aiming at facilitating disassembly for maintenance.

The confining pressure cavity 111 of the present disclosure is disposed at the bottom of the pressure chamber body 11, and the piston 12 isolates the axial pressure cavity 112 from the confining pressure cavity 111, so that the axial pressure cavity and the confining pressure cavity are not communicated with each other, thereby loading the axial pressure and the confining pressure on the sample 100. The confining pressure cavity 111 is provided with a sample mounting position 115, when the sample is mounted at the sample 100 mounting position 115, the periphery of the sample 100 is not contacted with the side wall of the confining pressure cavity 111, the second load generating device 31 outputs load pressure to enter the second pressurizing cylinder 32 for enhancement, and then hydraulic oil after the enhancement is filled into the confining pressure cavity 111 through the oil filling and discharging interface 113 and then acts on the periphery of the sample 100 to provide confining pressure; the load pressure (hydraulic oil) supplied from the first load generating device 21 enters the axial pressure chamber 112 through the first pressure cylinder 22 and the axial pressure port 116 to apply a force to the piston 12 and thus to apply an axial pressure to the sample 100.

Specifically, the sample mounting location 115 of the present disclosure may be disposed in the middle of the confining pressure cavity 111, and the upper and lower ends of the sample 100 are mounted with solid metal indenters made of stainless steel, which are located on the same axis as the sample 100. In order to isolate the sample 100 from the hydraulic oil in the confining pressure cavity 111, a heat shrinkage tube is used for sealing the sample 100. Annular grooves are formed in the annular directions of the upper pressure head and the lower pressure head, O-shaped rubber sealing rings are embedded into the grooves, and the sealing rings have heat resistance. The rock salt and the pressure head are sleeved by the heat shrinkage pipe, and the heat shrinkage pipe is closely attached to the sample 100 and the pressure head after being heated for a plurality of minutes, and the sealing ring is hooped by the metal hoop, so that the effect of sealing the sample 100 is achieved. After the plastic packaging of the test sample 100 is completed, an axial displacement sensor and an annular displacement sensor are mounted on the test sample 100, and the annular displacement sensor is fixed at a position in the middle of the height of the test sample 100. The sample 100 is placed in the sample 100 mounting site 115, and the sensor lines are connected. The axial pressure to which the sample 100 is subjected is applied by the piston 12. The axial pressure applied to the sample 100 may be superimposed by a hydrostatic pressure exerted by the high pressure hydraulic oil in the containment chamber 111 and an axial biasing force exerted by the piston 12, the magnitude of which is equal to the oil pressure in the shaft pressure chamber 112. As shown in fig. 4, the sample 100 is provided with an axial displacement sensor and an annular displacement sensor to monitor the deformation amount of the sample 100.

The injection and exhaust port 114 of the present disclosure is disposed at the uppermost height of the confining pressure cavity 111, and is used for opening the injection and exhaust port 114 when injecting oil into the confining pressure cavity 111, and air in the confining pressure cavity 111 can be discharged from the injection and exhaust port 114 along with the rise of the hydraulic oil interface to the confining pressure cavity 111; when the confining pressure cavity 111 is filled with hydraulic oil, hydraulic oil stably flows out of the air injection and exhaust interface 114, so that the air injection and exhaust interface 114 also plays a role in judging whether the oil injection process is finished by observing whether hydraulic oil flows out of the air injection and exhaust interface 114 when the confining pressure cavity 111 is injected with oil. Further, the air injection and exhaust interface 114 is connected with a pipeline, so that hydraulic oil can be introduced into an external oil cylinder; after the test is completed, hydraulic oil needs to be discharged from the confining pressure cavity 111, and in the process, the air injection and discharge interface 114 is connected with an air compressor, and the hydraulic oil in the confining pressure cavity 111 is driven out by high-pressure air, and a discharge channel of the hydraulic oil is the oil injection and discharge interface 113. In some embodiments, the portion of the axial pressure chamber 112 is formed of a separate structure that is bolted to the pressure chamber body 11, in a manner and with a constant effect, with the aim of facilitating maintenance.

The oil filling and discharging interface 113 is arranged at the bottom of the confining pressure cavity 111, the oil filling and discharging interface 113 is connected with an oil filling pump, hydraulic oil is filled into the confining pressure cavity 111 through the oil filling and discharging interface 113, and air in the confining pressure cavity 111 can be discharged from an air filling and discharging interface 114 at the top end of the confining pressure cavity 111; after the test is completed, hydraulic oil needs to be discharged from the confining pressure cavity 111, the oil filling and discharging interface 113 is a discharge channel of the hydraulic oil, the oil filling and discharging interface 113 is connected with an oil conveying pipeline, the hydraulic oil in the confining pressure cavity 111 can be discharged into an external oil tank, and the discharged hydraulic oil can be reused in the next test; when the hydraulic oil in the confining pressure cavity 111 is drained, the oil filling and draining interface 113 does not output hydraulic oil any more, but the stable air flow can be used for judging whether the oil draining process is finished according to whether the stable air flow appears at the oil filling and draining interface 113.

In some embodiments, the confining pressure cavity 111 of the present disclosure is further provided with a confining pressure interface 118, the confining pressure interface 118 being used to increase or decrease the load pressure into the confining pressure cavity 111.

In this embodiment, the load pressure of the confining pressure cavity 111 is poured into the confining pressure cavity 111 from the confining pressure interface 118 in the test process, and the monitoring data are not accurate due to the fact that the connecting device is repeatedly disassembled and assembled at the same interface to cause the pressure change in the confining pressure cavity 111 by arranging an additional interface to be distinguished from the oil filling and discharging interface 113.

In some embodiments, confining pressure interface 118 is disposed on a sidewall of confining pressure cavity 111 with confining pressure interface 118 facing a sidewall of sample 100.

In this embodiment, the confining pressure interface 118 is disposed on the side wall of the confining pressure cavity 111, that is, on the side wall of the pressure chamber body 11, and directly aligns with the side edge of the sample 100 to perform load pressure transmission, so that the confining pressure cavity 111 can be more balanced when increasing or decreasing load pressure. Further, the confining pressure interface 118 is disposed at a central position in the extending direction of the sample 100, so that the sample 100 is more balanced in load pressure.

In some embodiments, a balance chamber 117 is further provided in the pressure chamber body 11, the balance chamber 117 being provided between the shaft pressure chamber 112 and the confining pressure chamber 111, the confining pressure chamber 111 and the balance chamber 117 being communicated through a piston 12 passage, the piston 12 passage being provided inside the piston 12.

As shown in fig. 2 and 3, the axial cross section of the piston 12 in this embodiment is in a cross shape, that is, the piston 12 is thin at the upper and lower ends, a cylinder with a thickened section is provided in the middle, the diameters of the upper and lower end surfaces are the same, and are 100mm, and there is a part of the thickened section in the balance chamber 117, the diameter of the thickened section piston 12 is 141.4mm, in this embodiment, the upper and lower cross section is thinner, the diameter is 100mm, and the cross section of the thickened section is thicker, minus the cross section of the thinner end, that is, the protruding annular area is equal to the cross section of the thinner section. This ensures that the piston 12 is forced vertically. The annular area is equal to pi (141.42-1002) ≡10000 pi, and the area of the thinner end face is pi 1002, which are equal to each other, so that the balance effect required by the above can be achieved. Wherein, the circumferential direction of the thickening section is provided with a sealing ring for guaranteeing the tightness of the balance cavity 117. The piston 12 is provided with a piston 12 channel, the piston 12 channel starts from the end face of the piston 12 close to the bottom of the confining pressure cavity 111, the end point is positioned at the upper end of the thickening section of the piston 12, and the piston 12 channel is communicated with the confining pressure cavity 111 and the balance cavity 117. The lower end surface of the piston 12 is provided with a groove, and when the piston 12 is in close contact with the pressure head on the sample 100, hydraulic oil can flow into the passage of the piston 12 through the groove and then into the balance cavity 117. The purpose of the balancing chamber 117 is to achieve self-balancing of the confining pressure, i.e. zero force in the vertical direction, by the piston 12 when the confining pressure is applied. When the confining pressure P is applied to the confining pressure chamber 111, hydraulic oil flows into the balance chamber 117 along the passage of the piston 12. The cross-sectional area of the thickened section of the piston 12 is multiple of the area of the lower end surface of the piston 12, the protruding annular area of the thickened section is equal to the area of the lower end surface of the piston 12, the resultant force applied to the piston 12 in the vertical direction is zero, and the force applied to the rock sample 100 is hydrostatic pressure with the magnitude of P. Specifically, the upward pressure of the hydraulic oil in the confining pressure chamber 111 to the piston 12 is balanced by the downward pressure of the hydraulic oil in the balancing chamber 117 to the piston 12, the downward pressure of the hydraulic oil in the balancing chamber 117 to the piston 12 is equal to the upward pressure of the hydraulic oil in the confining pressure chamber 111 to the piston 12, the two pressures cancel each other, and when the high-pressure hydraulic oil is added to the confining pressure chamber 111, the resultant force of the piston 12 in the vertical direction is zero, and the gravity of the piston 12 is far smaller than the force of the hydraulic oil in the confining pressure chamber 111 to the piston 12 during the test, so that the gravity of the piston 12 is ignored. Further, the confining pressure applied to the sample 100 is directly applied by the high-pressure hydraulic oil in the confining pressure chamber 111. The confining pressure cavity 111 is filled with high-pressure hydraulic oil, the pressure of the hydraulic oil is the target confining pressure P, the sample 100 is completely immersed in the high-pressure hydraulic oil, the pressure born by the sample 100 is the hydrostatic pressure of P, the pressures born by the sample 100 in all directions are equal, and the bearing direction is the normal direction of each point of the sample 100. The lower end face of the piston 12 receives pressure with the size PA (a is the cross-sectional area of the lower end face of the axial loading piston 12) in the vertical upward direction, and the upper end face of the thickening section in the balance cavity 117 receives pressure with the size PA '(a' is the annular area of the thickening section of the piston 12 in the balance cavity 117, namely the difference between the cross-sectional area of the thickening section and the cross-sectional area of the lower end face) in the vertical downward direction. Where a=a', the upward and downward pressures experienced by the axially loaded piston 12 cancel each other out, and the pressure experienced by it in the axial direction is zero.

In some embodiments, piston 12 defines balance chamber 117 as a third chamber 916 and a second chamber 917, and fourth chamber 917 is provided with balance chamber vent 300, balance chamber vent 300 for venting air within third chamber 916; the fourth chamber 917 is adjacent to the axial pressure chamber 112 and the pressure liquid in the confining pressure chamber 111 enters the fourth chamber 917 through the piston channel 121.

In this embodiment, the third chamber 916 and the second chamber 917 are not in communication, the third chamber 916 is provided with the balance chamber vent 300, and when hydraulic oil enters the fourth chamber 917 through the piston passage 121, the piston 12 moves downward so that air in the third chamber 916 is discharged from the balance chamber vent 300.

Further, the inside diameter of the axial compression chamber 112 is 80-120 mm, the present disclosure specifically selects 100mm, the inside diameter of the balancing chamber 117 is 135-145mm, and the present disclosure specifically selects 141.4mm. The bottom of the balance cavity 117 is provided with a balance cavity 117 exhaust hole, which is used for ensuring that air in the balance cavity 117 below the third chamber 916 of the piston 12 can freely enter and exit when the axial loading piston 12 moves up and down; in the preliminary stage before the test, the exhaust hole of the balance chamber 117 is connected to the air compressor, and the piston 12 is pushed upward to the uppermost initial position by the air pressure, so that the hydraulic oil or air in the balance chamber 117 is emptied. A circular opening is provided between the confining pressure chamber 111 and the balancing chamber 117, the diameter of which is 100mm, which is the same as the diameter of the loading piston 12. The circular opening is provided with a sealing ring, and when the piston 12 is installed, the opening of the confining pressure cavity 111 and the balance cavity 117 form good sealing isolation.

In some embodiments, in order to meet the temperature requirement of the sample 100, a heating element and a temperature sensor are disposed around the mounting location 115 of the sample 100, the heating element is used for adjusting the temperature of the pressure liquid, the temperature sensor is used for monitoring the temperature of the pressure liquid, and the monitored temperature data can be used as a basis for adjusting the temperature of the pressure liquid by the heating element. Further, when the ideal ambient temperature cannot be controlled, the present disclosure provides a thermal insulation jacket at a position of the pressure chamber body 11 corresponding to the confining pressure cavity 111.

The bottom surface of the confining pressure cavity 111 is distributed with displacement and temperature sensor interfaces for connecting the axial displacement sensor 400, the annular displacement sensor 500 and the temperature sensor, and sealing rings are arranged at the interfaces for maintaining the tightness in the confining pressure cavity 111.

Specifically, four heating elements and a temperature sensor are disposed in the confining pressure cavity 111, and the heating elements and the temperature sensor are fixed on the bottom surface of the confining pressure cavity 111. The heat preservation cover is installed in the outside of confining pressure chamber 111, wraps up confining pressure chamber 111 completely, and the heat preservation cover adopts thermal-insulated asbestos material, can effectively play the heat preservation effect. Wherein the heatable temperature is in the range of room temperature to c. The heating system can be divided into two stages of heating and constant temperature when heating.

Heating: when the target temperature is set, the heating switch is turned on, and the heating member starts to generate heat, so as to heat the hydraulic oil in the pressure chamber body 11, and the hydraulic oil with the increased temperature transfers heat to the inside of the sample 100. When the temperature sensor detects that the temperature of the hydraulic oil of the pressure chamber body 11 reaches the set target temperature, the heating controller issues a command to stop heating, and the heating member is powered off to stop heating.

Constant temperature stage: after the heating member stops heating, heat is transferred to the outside due to the fact that the temperature in the pressure chamber body 11 is higher than the temperature of the outside environment, and the temperature in the triaxial pressure chamber 1 is reduced. In order to slow down the temperature falling speed in the confining pressure cavity 111, a heat preservation sleeve is arranged outside the triaxial pressure chamber 1, and the heat preservation sleeve is made of heat-insulating asbestos materials, so that heat dissipation of the confining pressure cavity 111 to surrounding air can be effectively slowed down. When the temperature sensor detects that the temperature in the confining pressure cavity 111 is lower than the target temperature, the heating controller sends out a heating instruction, the heating piece is electrified to heat, and when the temperature reaches the target temperature, the heating controller sends out a heating stopping instruction, and the heating piece is powered off to stop heating. This is cycled to maintain a constant temperature within the confining pressure cavity 111. The temperature in the constant temperature stage confining pressure cavity 111 can be kept within a target temperature + -..degree.C.

In some embodiments, a base is disposed at the bottom of the pressure chamber body 11, one end of the base and the pressure chamber body 11 together form a confining pressure cavity 111, a sample 100 mounting location 115 is disposed on an end surface of the base embedded in the confining pressure cavity 111, and an oil filling and draining interface 113 is disposed inside the base.

In this embodiment, the bottom end of the confining pressure cavity 111 of the present disclosure is connected and sealed to a base, and a portion of the upper end of the base is embedded in the confining pressure cavity 111. In order to avoid pressure relief, an annular sealing ring is arranged at the embedded part to seal, so that the confining pressure cavity 111 is a closed cavity. Optionally, the pressure chamber body 11 and the base are tightly fixed by a quick hoop, and after the confining pressure is applied, the pressure chamber body 11 and the base may have a tendency to separate, and the quick hoop can fix the pressure chamber body 11 and bear the tensile force generated by the pressure chamber body 11 and the base. Further, the base of the present disclosure is detachably connected to the pressure chamber body 11 to facilitate maintenance.

The axial compression module and the confining pressure module of the present disclosure have the same components, wherein the first load generating device and the second load generating device have the same structure, and the first pressure cylinder and the second pressure cylinder have the same structure. Taking a first load generating device as an example to introduce the structural characteristics of the first load generating device, the first load generating device comprises an oil pressure load conversion module and a circulating load functional module, wherein the oil pressure load conversion module comprises a mounting plate 101, a movable oil cylinder 102 and a fixed piston 103, the movable oil cylinder 102 is sleeved on the fixed piston 103, a first oil inlet and outlet channel 104 is arranged in the mounting plate 101, the first oil inlet and outlet channel 104 is at least provided with two oil inlet and outlet interfaces 105, one end of the fixed piston 103 is connected with the mounting plate 101, a second oil inlet and outlet channel 106 is arranged in the fixed piston 103, one end of the second oil inlet and outlet channel 106 is communicated with the first oil inlet and outlet channel 104, and the opposite end is communicated with the interior of the movable oil cylinder 102;

the cyclic load function module comprises a driving part 107 and an adjusting part 108, wherein the driving part 107 is connected with the movable oil cylinder 102; the adjusting portion 108 is connected to the driving portion 107, and the adjusting portion 108 is used for adjusting the urging force of the driving portion 107 to the movable cylinder 102.

The fixed piston 103 is arranged inside the movable oil cylinder 102, and the transformation of oil pressure load is realized through the cooperation of the movement of the movable oil cylinder 102 and the fixed piston 103, so that load pressure is transmitted to the triaxial pressure chamber 1 filled with the sample 100. Specifically, the fixed piston 103 is connected to the mounting plate 101, in the embodiment of the present disclosure, the fixed piston 103 is the fixed piston 103 that does not generate relative motion with respect to the mounting plate 101, and a first oil inlet and outlet channel 104 having at least two oil inlet and outlet ports 105 is disposed inside the mounting plate 101, where one of the oil inlet and outlet ports 105 is connected to a hydraulic oil supply device to convey hydraulic oil (pressure liquid) into the first oil inlet and outlet channel 104, and the hydraulic oil enters the first oil inlet and outlet channel 104 and then enters the movable cylinder 102 through a second oil inlet and outlet channel 106 that communicates with the first oil inlet and outlet channel 104 inside the fixed piston 103. It will be appreciated that during the priming process in the preparatory phase of the test, other oil inlet and outlet ports 105 should be plugged, and when it is necessary to confirm whether the oil is full, the oil inlet and outlet ports 105 of the pressure chamber to be connected are opened again, for example, when the ports are out of oil indicating that there is no air in the movable oil cylinder 102 and the first oil inlet and outlet passage 104 and the second oil inlet and outlet passage 106, the oil is full.

Further, as shown, the mounting plate 101 of the present disclosure may be a square, a rectangular, a cylindrical, or other metal plate, and the present disclosure specifically selects a rectangular flat plate. The bottom surface of the mounting plate 101 is a surface to which the fixed piston 103 is attached, and the top surface thereof is a surface opposite to the bottom surface. Further, the first oil inlet and outlet passage 104 inside the mounting plate 101 may be a through hole directly formed in the inner radial direction, or may be a pipe installed inside the mounting plate 101, such as a steel pipe, an aluminum alloy pipe, or the like. In order to achieve the accuracy of the load pressure better, the passage turntables of the first oil inlet and outlet passage 104 and the second oil inlet and outlet passage 106 are all arranged to be straight lines, and the connection part of the first oil inlet and outlet passage and the second oil inlet and outlet passage is smoothly excessive, so that the pressure change caused by fluid force is avoided.

In some embodiments, the driving part 107 is configured as a gravity type driving, the driving part 107 includes a cantilever 71, a fulcrum frame 72, and a connection frame 73, the cantilever 71 is connected to the fulcrum frame 72, and the cantilever 71 is capable of rotating with respect to the fulcrum of the fulcrum frame 72, the fulcrum frame 72 is disposed on the mounting plate 101, the fulcrum frame 72 defines the cantilever 71 as a first cantilever 710 and a second cantilever 711 with the fulcrum as a boundary, one end of the connection frame 73 is hinged to the second cantilever 711, and the opposite end is hinged to one end of the movable cylinder 102 near the cantilever 71.

In this embodiment, the suspension bar 71 is connected to the fulcrum frame 72 to form a "seesaw" structure, the fulcrum frame 72 is provided on the top surface of the mounting plate 101, and the connection point of the fulcrum frame 72 and the suspension bar 71 is a fulcrum, and the rotation direction of the suspension bar 71 through the fulcrum is the height direction of the movable cylinder 102. The second cantilever 711 is connected to the movable cylinder 102 through the connecting frame 73, and a specific connection manner thereof may be that a through hole is formed on the mounting plate 101, one end of the connecting frame 73 passes through the through hole to be connected to the movable cylinder 102, and the opposite end is hinged to the second cantilever 711. In another embodiment, the connecting frame 73 includes a first connecting member, a second connecting member and a connecting plate, wherein the first connecting member and the second connecting member are respectively hinged to two ends of the connecting plate, and the other end of the first connecting member is hinged to the second cantilever 711, and the other end of the second connecting member is fixedly connected to the movable cylinder 102 through a through hole of the mounting plate 101. The direction of rotation after the above-mentioned hinge is the same as the direction of rotation of the suspension lever 71 through the fulcrum.

In some embodiments, the adjusting part 108 includes a moving member 81 and a driving member, the moving member 81 is connected to the first cantilever 710, and the driving member drives the moving member 81 to move in the extending direction of the first cantilever 710. Specifically, when the hanger bar 71 is kept horizontal, the moving member 81 is disposed at a horizontal position of the hanger bar 71, which may be a center position of the first cantilever 710 or other positions, in order to secure the horizontal of the hanger bar 71, the present disclosure particularly sets the horizontal position at the center position of the first cantilever 710. When the load pressure is adjusted, the driving member drives the moving member 81 to move from the horizontal position to both ends of the first cantilever 710, so that the cantilever 71 swings to adjust the waveform of the load pressure. The driving part drives the motion logic of the moving part 81 to adjust according to specific load waveforms, and the control command of the driving part is sent by the terminal switchboard.

The suspension lever 71 of the first load generating device 21 of the present disclosure is configured as a lever structure rotatable about the fulcrum of the fulcrum frame 72. When the arms of the first cantilever 710 and the second cantilever 711 of the suspension lever 71 are equal, the suspension lever 71 enters a stable stationary state and does not rotate around the fulcrum any more; when the arms of the first cantilever 710 and the second cantilever 711 of the suspension rod 71 are unequal, the suspension rod 71 rotates around the fulcrum, and during the rotation, the volume in the movable cylinder 102 changes (increases or decreases), resulting in the pressure change of the hydraulic oil in the movable cylinder 102, and assuming that the hydraulic oil in the movable cylinder 102 is airtight, when the volume in the movable cylinder 102 increases, the compression degree of the hydraulic oil by the movable cylinder 102 decreases, and the pressure of the hydraulic oil decreases; when the inner volume of the movable oil cylinder 102 is reduced, the compression degree of the movable oil cylinder 102 on the hydraulic oil is increased, and the pressure of the hydraulic oil is increased.

The movable cylinder 102 is a closed cylinder 91, and is filled with hydraulic oil, and when a weight is added to the first arm 710 of the cantilever 71, the arm of force of the first arm 710 is larger than the arm of force of the second arm 711. At this time, the first cantilever 710 rotates downward about the fulcrum, and the second cantilever 711 rotates upward about the fulcrum. The upward rotation of the second cantilever 711 drives the movable cylinder 102 to displace upward, and the volume of hydraulic oil in the movable cylinder 102 is reduced, which causes the hydraulic oil to be squeezed, and the pressure of the hydraulic oil increases. Thus, the force of the hydraulic oil acting on the movable cylinder 102 (acting on the bottom plane of the movable cylinder 102, the direction being vertically downward) increases. When the pressure of the hydraulic oil increases to balance the arm of the first and second cantilevers 710, 711 of the cantilever 71 again, the cantilever 71 is not rotated any more and the first load generating means 21 is stabilized again. This process achieves the effect that the pressure of the hydraulic oil in the oil cylinder increases when the weight on the first load generating device 21 is increased.

When the weight is reduced from the first cantilever 710 of the cantilever bar 71, the moment arm of the first cantilever 710 is smaller than the moment arm of the second cantilever 711. At this time, the first cantilever 710 rotates upward about the fulcrum, and the second cantilever 711 rotates downward about the fulcrum. The downward rotation of the second cantilever 711 drives the movable cylinder 102 to displace downward, and the volume of hydraulic oil in the movable cylinder 102 increases, which reduces the extrusion degree of the hydraulic oil and reduces the pressure of the hydraulic oil. Thus, the force of the hydraulic oil acting on the movable cylinder 102 (acting on the bottom plane of the movable cylinder 102, the direction being vertically downward) decreases. When the pressure of the hydraulic oil is reduced to balance the moment arms of the first and second cantilevers 710 and 711 again, the cantilever 71 is not rotated any more and the first load generating means 21 is stabilized again. This process achieves the effect that the hydraulic oil pressure in the oil cylinder is reduced when the weight on the first load generating device 21 is reduced.

When the weight-suspended moving member 81 continues to move in a direction away from the fulcrum, the arm of the first cantilever 710 increases and is larger than the arm of the second cantilever 711, and at this time, the first cantilever 710 rotates downward about the fulcrum and the second cantilever 711 rotates upward about the fulcrum. The upward rotation of the second cantilever 711 drives the movable cylinder 102 to displace upward, and the volume of hydraulic oil in the movable cylinder 102 is reduced, which causes the hydraulic oil to be squeezed, and the pressure of the hydraulic oil is continuously increased. This process achieves the effect that the pressure of the hydraulic oil in the hydraulic cylinder is continuously increased as the moving member 81 is continuously moved away from the fulcrum end.

When the weight-suspended moving member 81 continues to move in a direction approaching the fulcrum, the arm of the first cantilever 710 is reduced and smaller than the arm of the second cantilever 711, and at this time, the first cantilever 710 rotates upward about the fulcrum and the second cantilever 711 rotates downward about the fulcrum. The upward rotation of the second cantilever 711 drives the movable cylinder 102 to displace downward, and the volume of the hydraulic oil in the movable cylinder 102 increases, so that the extrusion degree of the hydraulic oil is reduced, and the pressure of the hydraulic oil is continuously reduced. This process achieves the effect that the pressure of the hydraulic oil in the hydraulic cylinder is continuously reduced as the moving member 81 is continuously moved away from the fulcrum end.

On the premise that the automatic oil returning and supplementing device 4 is not provided in the present disclosure, the left-right movement of the moving member 81 causes the suspension rod 71 to swing around the fulcrum, which causes the load pressure to change, after the position of the moving member 81 moves, the arm (i.e. bending moment) at the end of the first suspension rod 71 changes, and because the arm is balanced, the arm at the second suspension arm 711 also changes, and the position of the force from the fulcrum frame 72 does not change, which causes the load pressure to change. When the automatic oil removing and supplementing device is added, oil is supplemented (or removed) to the movable oil cylinder 102 as soon as the suspension rod 71 is detected to incline at a small angle, the suspension rod 71 basically does not swing at a large angle, however, the load pressure also changes circularly, and the force arm is balanced. The above aims to introduce the principle of gravity driving, and the technical proposal of the present disclosure is that the device is provided with an automatic oil returning and supplementing device

In some embodiments, the driving member includes a driving motor 821, a screw 822 and a limiting member 823, the moving member 81 is connected with the screw 822, the screw 822 is disposed along the extending direction of the first cantilever 710, the driving motor 821 is disposed opposite to the position of the fulcrum frame 72, the driving motor 821 is used for enabling the screw 822 to rotate to drive the moving member 81 to approach or separate from the driving motor 821, the limiting member 823 is disposed at two ends of the screw 822, and the limiting member 823 is used for limiting the moving range of the moving member 81. It will be appreciated that the rotation of the screw 822 is the forward force of the moving member 81, and the moving member 81 does not rotate, and the specific principle is that the details of the prior art will not be repeated herein.

In this embodiment, the position of the driving motor 821 and the fulcrum frame 72 is opposite to each other, so that the suspension rod 71 is balanced, wherein the limiting member 823 may be selected from a structure of a stop block, a baffle, and the like, and the present disclosure specifically selects a limiting baffle. Further, a sensor may be disposed on the limiting member 823, and when the moving member 81 is present in the pre-warning range of the sensor, the sensor sends a signal to the terminal exchange, and the terminal exchange controls the driving motor 821 to stop. The sensor can prompt test personnel whether the equipment fails or whether the setting of load pressure is wrong, so that the stability of long-term test is ensured. In some embodiments, to avoid interruption of the test by a power outage, a backup power source may be provided to the drive motor 821. Further, the moving member 81 of the present disclosure may be a sliding block, and the moving member 81 itself has a certain weight and a specific weight to be adjusted according to the requirement. The wheel group can be arranged under the sliding block, so that the movement is smoother.

In some embodiments, the end of the second cantilever 711 remote from the first cantilever 710 is provided with a set of balancing weights having a plurality of balancing weights detachably connected to the second cantilever 711. In this embodiment, mainly to enable the suspension rod 71 to be kept horizontal, and the balance weights on the balance weight set can be increased or decreased to finely adjust the load pressure, the balance weights are used to balance the initial moment arm generated by the self gravity of the cantilever at the end of the first cantilever 710, so that when the weight is not added at the end of the first cantilever 710, the force applied by the driving part 107 to the movable cylinder 102 is such that the adaptability of the present disclosure to various load waveforms is stronger.

In some embodiments, the first cantilever 710 further includes a first weight portion, a running slot is formed in the extending direction of the first cantilever 710, one end of the first weight portion passes through the running slot and is connected with the moving member 81, and the moving member 81 can drive the first weight portion to move within the range of the running slot.

The running groove of the present disclosure is a long strip-shaped through hole opened along the extending direction of the first cantilever 710, and in the embodiment provided with the limiting members 823, the running groove is opened between the two limiting members 823. It should be noted that, in the embodiment of the moving member 81 provided with the wheel set, the first cantilever 710 should also be provided with a wheel set sliding surface for the wheel set to contact and slide after forming a running groove, and the running groove is intended to enable the connection portion of the first weight portion and the moving member 81 to pass through and slide in the running groove along with the movement of the moving member 81.

In some embodiments, the first weight includes a first boom and a first weight placement location, one end of the first boom being connected to the mover 81 through the travel slot and the opposite end being connected to the first weight placement location.

One end of the first boom of the present disclosure serves as a connection portion with the bottom of the moving member 81, and the other end is provided with a first weight placement position, which may be a placement box for weights, or may be a local position where weights are directly suspended and sleeved on the first boom. Wherein the weight can be a weight or other article with a certain weight. In a second aspect of this embodiment, the weight may be fixed by providing a snap on the first boom, where the snap is provided as the first counterweight placement position.

In some embodiments, as shown, an end of the first cantilever 710 of the present disclosure remote from the second cantilever 711 is provided with a second weight, one end of which is hinged with the first cantilever 710. In order to cooperatively adjust the balance of the suspension rod 71, a plurality of detachable weights are also arranged on the second weight portion, and the second weight portion is arranged at the tail end of the first cantilever 710, so that a certain weight is added to the side of the first cantilever 710, the maximum threshold value of the load pressure can be further increased, and a wider debugging range is provided for fine adjustment of the load pressure.

In some embodiments, as shown in the figures and drawings, in order to realize secondary amplification of load pressure, the present disclosure is provided with a first booster cylinder 22 and a second booster cylinder 32, specifically, a structure of the first booster cylinder 22 is described, the first booster cylinder 22 includes a cylinder 91 and an adjusting piston 92, the adjusting piston 92 is disposed in the cylinder 91, the adjusting piston 92 defines the cylinder 91 into a first chamber 911 and a second chamber 912, the pressure of the first chamber 911 is greater than that of the second chamber 912, a first channel 913 is disposed on a side of the first chamber 911 away from the second chamber 912, a connection valve is disposed on the outside of the cylinder 91 in the first channel 913, a second channel 914 is disposed on a side of the second chamber 912 away from the first chamber 911, the second channel 914 is communicated with an oil outlet end of the first oil inlet and outlet channel 104, and an air inlet and outlet hole 915 is disposed on a side of the second chamber 912 close to the first chamber.

The second passage 914 of the present disclosure is communicated with the oil outlet end of the first oil inlet and outlet passage 104 through a connecting valve, and an air inlet and outlet hole 915 is disposed on one side of the second chamber 912 close to the first chamber 911, which is used for freely allowing air in the cavity of the adjusting piston 92 and the cylinder 91 to enter and exit when the adjusting piston 92 moves up and down.

In the first booster cylinder of the present disclosure, the adjusting piston 92 defines two independent oil chambers inside the cylinder 91, namely, a first chamber 911 and a second chamber 912, wherein the first chamber 911 is a high-pressure chamber, the second chamber 912 is a low-pressure chamber, the pressure of hydraulic oil in the first chamber 911 is Ph, and the pressure of hydraulic oil in the second chamber 912 is Pl. In the embodiment, the upper and lower parts of the adjusting piston 92 are respectively solid cylinders, square cylinders, etc. with two dimensions, and the cross-sectional areas of the adjusting piston 92 at the high-pressure end and the low-pressure end are Ah and Al respectively. According to the force balance principle, the adjusting piston 92 is used as an analysis object, and the relationship between the pressures in the first chamber 911 and the second chamber 912 is:

Wherein, To adjust the mass of the piston 92. The relationship between the hydraulic oil pressure in the first and second chambers 911, 912 when the load changes can be expressed as:

wherein the ratio of the cross-sectional areas of the low pressure end and the high pressure end of the regulator piston 92 is:

I.e. when the pressure at the low pressure end in the cylinder 91 increases At this time, the pressure of the high-pressure end in the cylinder 91 increasesThe pressure cylinder 9 may multiply the pressure input to the low pressure side and output from the second passage.

When the pressures at both ends of the adjustment piston 92 are equal, the adjustment piston 92 does not undergo positional movement; when the load needs to be increased, the acting force applied to the movable oil cylinder 102 by the circulating load functional module is increased, the hydraulic oil in the movable oil cylinder 102 flows into the second chamber 912 of the cylinder 91, the pressure of the second chamber 912 is increased, and at the moment, the pressure Fl of the second chamber 912 is greater than the pressure Fh of the first chamber 911 and the gravity of the piston 12And, the regulator piston 92 moves toward the first chamber 911 side, the hydraulic oil pressure of the first chamber 911 increases, and when the second chamber 912 pressure Fl is equal to the pressure Fh of the first chamber 911 and the gravity/>, of the piston 12And, the adjusting piston 92 stops moving, completing the transmission of the load pressure.

In some embodiments, the adjusting piston 92 is provided with sealing rings with the inner wall of the cylinder 91, ensuring the sealing of the first chamber 911 and the second chamber 912. Further, a position scale is fixed on the adjusting piston 92, and is used for judging the position of the adjusting piston 92 relative to the cylinder 91 when moving up and down, and the position scale and the adjusting piston 92 can be connected or welded by threads. As shown, the position scale is connected to the adjusting piston 92 in the second chamber 912 by a through hole opened outside the cylinder 91 into the cylinder 91.

In some embodiments, the device further comprises a supporting frame and a limiting balance plate, the supporting frame is used for supporting the mounting plate 101, the supporting frame at least comprises two supporting feet, the two supporting feet are symmetrically arranged, the limiting balance plate is connected with the movable oil cylinder 102, and the limiting balance plate is in sliding connection with the supporting feet.

In this embodiment, by providing a support frame for supporting the mounting plate 101 so as to accommodate more use environments, the support frame includes at least two brackets and two legs are symmetrically provided to achieve balance, and further, the legs can be provided as a telescopic structure so that the length of the legs is adjusted. When the support legs are used, the support leg is ensured to keep the mounting plate 101 horizontal and the movable oil cylinder 102 vertical, so that shaking and gradient image load pressure change of the support leg image mounting plate 101 and the movable oil cylinder 102 are avoided. Further, as shown in the figure, the movable oil cylinder 102 is arranged in the middle of the limiting balance plate, and two ends of the limiting balance plate are slidably connected with the bracket, so that the movable oil cylinder 102 is prevented from shaking when moving. Specifically, in some embodiments, the limiting balance plate may be directly connected to the connection frame 73, and the movable oil cylinder 102 is penetratingly arranged in the limiting balance plate and fixed, so that the connection frame 73 and the limiting balance plate cooperate to realize movement of the movable oil cylinder 102, and stability of movement of the movable oil cylinder 102 is ensured.

When the first load generating device 21 of the present disclosure generates a cyclic load, hydraulic oil is generated to flow from the movable cylinder 102 of the first load generating device 21 into the low pressure end of the first pressure cylinder 22 when the load increases; when the load decreases, the hydraulic oil amount in the movable cylinder 12 is insufficient or excessive because the hydraulic oil 102 flowing into the first load generating device 21 from the low pressure end of the first booster cylinder 22 is generated, and in this case, the automatic oil-returning and supplementing device 4 is required to supplement the hydraulic oil into the movable cylinder 12 or discharge the hydraulic oil from the movable cylinder 12.

This process can be expressed specifically as: when the load is increased, firstly, the arm of force at the weight end is required to be increased, and the position of the weight or the adjusting moving part 81 on the first cantilever 710 can be increased, the pressure of hydraulic oil in the movable oil cylinder 102 of the first load generating device 21 is increased and is larger than the pressure of hydraulic oil in the low-pressure end of the first booster cylinder 22 communicated with the movable oil cylinder, the hydraulic oil flows outwards, the oil quantity of the hydraulic oil in the movable oil cylinder 102 is reduced, the weight end of the cantilever 71 of the first load generating device is inclined downwards, and the oil is required to be replenished from the automatic oil withdrawal and replenishment device 4 to the first load generating device 21; when the load is reduced, the arm of force at the weight end needs to be reduced first, the pressure of the hydraulic oil in the movable oil cylinder 102 of the first load generating device 21 is reduced and is smaller than the pressure of the hydraulic oil in the low pressure end of the first pressurizing cylinder communicated with the arm of force, the hydraulic oil flows into the movable oil cylinder 102 of the first load generating device 21 from the low pressure end of the first pressurizing cylinder 22, the hydraulic oil in the movable oil cylinder 102 is increased, the weight end of the suspension rod 71 of the first load generating device 21 is inclined upwards, and the hydraulic oil needs to be discharged from the movable oil cylinder 102 of the first load generating device to the automatic oil withdrawal and supplement device 4.

The automatic oil removing and supplementing device 4 realizes oil supplementing and oil removing functions and comprises two steps: the oil quantity of the first load generating device 21 is monitored, and the oil supplementing or oil removing actions are completed.

Monitoring the amount of oil in the first load generating device 21 and/or the second load generating device 31 is achieved by monitoring the angle of inclination of the boom 71 of the first load generating device. An angle sensor is provided on the suspension rod 71, and the angle sensor reads 0 ° when the suspension rod is horizontal, and the angle sensor reads less than 0 ° when the weight end of the suspension rod 71 is inclined downward, and the angle sensor reads more than 0 ° when the weight end of the suspension rod 71 is inclined upward. The inclination angle of the suspension rod 71 detected by the angle sensor is transmitted to the control system of the automatic oil returning and supplementing device 4 in real time. For example, the automatic oil-compensating angle threshold is set to be 1 °, and the automatic oil-removing angle threshold is set to be-1 °, so that the automatic oil-compensating process is that when the reading of the angle sensor is monitored to be greater than 1 °, the system of the automatic oil-removing and compensating device 4 controls the valves of the movable oil cylinder 102 and the low pressure end of the first booster cylinder 22 to be closed, and then controls the valve between the automatic oil-removing and compensating device 4 and the first load generating device 21 to be opened, and the oil is compensated from the automatic oil-removing and compensating device 4 to the first load generating device. The oil supplementing process monitors the reading of the angle sensor in real time, when the reading of the angle sensor is monitored to be 0 ℃, the automatic oil supplementing device 4 stops supplementing oil to the first load generating device 21, the control system of the automatic oil supplementing device 4 firstly controls the pneumatic valve between the automatic oil supplementing device 4 and the first load generating device 21 to be closed, and then controls the pneumatic valve between the first load generating device 21 and the first pressurizing cylinder 22 to be opened.

The automatic oil removing process is that when the reading of the angle sensor is smaller than-1 DEG, the control system of the automatic oil removing and supplementing device 4 firstly controls the valve of the movable oil cylinder 102 of the first load generating device 21 and the low pressure end of the first pressurizing cylinder 22 to be closed, and then controls the valve between the automatic oil removing and supplementing device 4 and the first load generating device 21 to be opened, and oil is removed from the first load generating device 21 to the oil cylinder of the automatic oil removing and supplementing device 4. And the reading of an angle sensor is monitored in real time in the oil removing process, when the reading of the angle sensor is monitored to be 0 ℃, the control system of the automatic oil removing and supplementing device 4 firstly controls the pneumatic valve between the automatic oil removing and supplementing device 4 and the first load generating device 21 to be closed, and then controls the pneumatic valve between the first load generating device 21 and the first pressurizing cylinder 21 to be opened, so that the oil removing process is completed.

The above described oil-returning and replenishing process is exemplified by the first load generating device 21 and the first pressure cylinder, and the second load generating device 31 and the second pressure cylinder 32 are identical in structure and distance to the first load generating device 21 and the first pressure cylinder 22.

In a second aspect of the present disclosure, a test method for an ultralow frequency cyclic load creep test using the above ultralow frequency cyclic load creep test system is provided, including the following steps:

test preparation

Checking whether the displacement sensor and the temperature sensor work normally or not, and calibrating the displacement sensor and the temperature sensor by using a calibration tool; opening valves at high-pressure ends and low-pressure ends of the first booster cylinder 22 and the second booster cylinder 32, injecting air into second chamber interfaces of the first booster cylinder 22 and the second booster cylinder 32 by utilizing an air compressor, completely moving pistons inside the first booster cylinder 22 and the second booster cylinder 32 to one end of a first chamber under the action of air pressure, discharging air inside the first chamber of the booster cylinder, injecting hydraulic oil into the high-pressure interfaces of the first booster cylinder 22 and the second booster cylinder 32 by utilizing a hand pump, completely moving the pistons to one end of the second chamber, and fully storing hydraulic oil inside the first chamber; the valve of the axial pressure cavity 112 of the triaxial pressure chamber 1 is opened, so that air in the axial pressure cavity 112 can be freely discharged, the piston 12 of the axial pressure cavity 112 is moved to the top end by utilizing the air injection and exhaust interface 114 of the air compressor to the triaxial pressure chamber 1, and the air in the axial pressure cavity 112 is completely discharged.

Mounting sample

The rock sample 100 is sealed, the sample 100, the upper pressure head and the lower pressure head are aligned to the same central axis, annular grooves are formed in the annular directions of the upper pressure head and the lower pressure head, O-shaped rubber sealing rings are embedded in the grooves, and the sealing rings have heat resistance. Sleeving the rock salt and the cushion block by using a heat-shrinkable plastic sleeve, and heating and baking the electric hair drier for a plurality of minutes until the heat-shrinkable plastic sleeve is closely attached to the sample 100 and the cushion block, and hooping the sealing ring by using a metal hoop to achieve the effect of sealing the sample; after the plastic packaging of the sample 100 is completed, the axial displacement sensor 400 and the annular displacement sensor 500 are installed on the sample 100, and the annular displacement sensor 500 is fixed at the middle position of the height of the sample; the sample 100 is loaded into the triaxial pressure chamber 1, and the axial displacement sensor 400 and the temperature sensor are connected to corresponding interfaces on the triaxial pressure chamber base.

Intelligent measurement and control system for starting

Opening intelligent measurement and control software, and checking whether signals of all sensors are normally displayed; the probe positions of the displacement sensors are adjusted so as to leave a sufficient deformation measurement margin.

Sealing the triaxial pressure chamber and injecting oil into the confining pressure cavity

The triaxial pressure chamber is closed, the gas filling and exhausting interface of the triaxial pressure chamber is opened and connected with an oil delivery pipe, the other end of the oil delivery pipe is inserted into an empty container for containing hydraulic oil, and the step aims at observing whether the hydraulic oil flows out of the gas filling and exhausting interface 114 so as to judge whether the gas filling and exhausting interface is full. Connecting the oil filling and discharging interface 113 with an oil filling pump, and injecting high-temperature-resistant hydraulic oil into the confining pressure cavity 111 of the triaxial pressure chamber 1 through the oil filling and discharging interface 113 by using the oil filling pump, wherein air in the confining pressure cavity can flow from the oil filling and discharging interface 114 in the process; when the pressure cavity 111 of the triaxial pressure chamber 1 is filled with hydraulic oil, the hydraulic oil is discharged from the gas filling and discharging port 114 of the triaxial pressure chamber, and after the stable liquid flow without bubbles flows out from the gas filling and discharging port 114, the oil pump is closed, the gas filling and discharging port 114 is closed, and finally the oil filling and discharging port 113 is closed.

Automatic oil supplementing system opened

The oil tank of the automatic oil removing and supplementing device 4 is filled with hydraulic oil, the automatic oil removing and supplementing device 4 is opened, and the automatic oil removing and supplementing device 4 automatically monitors the oil quantity of the first load generating device 21 and the second load generating device 31 and performs oil supplementing or oil removing operation.

Applying an initial load

Setting storage parameters of the sensor data, including a storage path and a storage period. The file output by data storage is in xlsx format, and can be directly opened by Excel. The reasonable range of the preservation period is 5 s to 24 h, and the preservation period can be set according to test requirements. In the process of data acquisition and automatic storage, the storage period can be modified, and the operation is as follows: the first step, clicking a pause button; step two, resetting the preservation period; third, clicking the save button, the process does not require replacement of the save path. Controlling the moving parts 81 of the first load generating device 21 and the second load generating device 3 to move to the middle position of the stroke, and applying a proper number of weights on the weight tray below the moving parts 81, so that the load change value is larger than the amplitude value of the target circulating load in the forward and backward movement of the movable parts 81 in the full stroke; weights are added to the weight trays of the first load generating device 21 and the second load generating device 31 based on the average load (average value of the maximum load and the minimum load) of the target cyclic load until the pressure output into the triaxial pressure chamber is equal to the average load of the target cyclic load.

Set cyclic load waveform opening test

And setting a waveform of a target cyclic load in a stress control area of the intelligent measurement and control software, clicking for operation, and starting loading of the testing machine according to the target cyclic load.

In this disclosure, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more, unless expressly defined otherwise. The terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; "coupled" may be directly coupled or indirectly coupled through intermediaries. The specific meaning of the terms in this disclosure will be understood by those of ordinary skill in the art as the case may be.

In the description of the present disclosure, it should be understood that the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "rear", etc., are based on the directions or positional relationships shown in the drawings, are merely for convenience in describing the present disclosure and simplifying the description, and do not indicate or imply that the devices or units referred to must have a specific direction, be configured and operated in a specific direction, and thus should not be construed as limiting the present disclosure.

In the description of the present specification, the terms "one embodiment," "some embodiments," "particular embodiments," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing is merely a preferred embodiment of the present disclosure, and is not intended to limit the present disclosure, so that various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. An ultra-low frequency cyclic load creep test system, comprising:

The triaxial pressure chamber comprises a pressure chamber body and a piston, wherein the piston is used for limiting a confining pressure cavity and a shaft pressure cavity in the pressure chamber body, the confining pressure cavity is provided with an oil injection and discharge interface, an oil injection and discharge interface and a sample mounting position, the sample mounting position is used for bearing a sample in the confining pressure cavity, the oil injection and discharge interface is arranged at one end, close to the shaft pressure cavity, of the confining pressure cavity, and the oil injection and discharge interface is arranged at the other end of the confining pressure cavity;

The axial pressure cavity is provided with an axial pressure interface, the axial pressure interface is used for inputting pressure liquid into the axial pressure cavity, and the piston is used for applying axial pressure to the sample;

the first load generating device comprises an oil pressure load conversion module and a circulating load functional module, the oil pressure load conversion module comprises a mounting plate, a movable oil cylinder and a fixed piston, the movable oil cylinder sleeve is arranged on the fixed piston, a first oil inlet and outlet channel is arranged in the mounting plate, at least two oil inlet and outlet interfaces are arranged in the first oil inlet and outlet channel, one end of the fixed piston is connected with the mounting plate, a second oil inlet and outlet channel is arranged in the fixed piston, one end of the second oil inlet and outlet channel is communicated with the first oil inlet and outlet channel, and the opposite end of the second oil inlet and outlet channel is communicated with the interior of the movable oil cylinder;

The circulating load function module comprises a driving part and an adjusting part, and the driving part is connected with the movable oil cylinder; the adjusting part is connected with the driving part and is used for adjusting the acting force applied by the driving part to the movable oil cylinder, wherein,

The driving part comprises a cantilever rod, a fulcrum frame and a connecting frame, wherein the cantilever rod is connected with the fulcrum frame, the cantilever rod can rotate relative to a fulcrum of the fulcrum frame, the fulcrum frame is arranged on the mounting plate, the fulcrum frame limits the cantilever rod to a first cantilever and a second cantilever by the fulcrum, one end of the connecting frame is hinged with the second cantilever, and the opposite end of the connecting frame is hinged with one end of the movable oil cylinder close to the cantilever rod;

The adjusting part comprises a moving part and a driving part, the moving part is connected with the first cantilever, the moving part can move in the extending direction of the first cantilever, and the driving part is used for driving the moving part;

2. The ultralow frequency cyclic load creep test system according to claim 1, wherein the driving member comprises a driving motor, a screw rod and a limiting member, the moving member is connected with the screw rod, the screw rod is arranged along the extending direction of the first cantilever, the driving motor is arranged opposite to the position of the fulcrum frame, the driving motor is used for enabling the screw rod to rotate so as to drive the moving member to be close to or far away from the driving motor, the limiting member is arranged at two ends of the screw rod, and the limiting member is used for limiting the moving range of the moving member.

3. The ultralow frequency cyclic load creep test system according to claim 1, wherein the first booster cylinder and the second booster cylinder each comprise a cylinder body and an adjusting piston, the adjusting piston is arranged in the cylinder body, the adjusting piston limits the cylinder body to a first chamber and a second chamber, the pressure of the first chamber is larger than that of the second chamber, a first channel is arranged on one side, away from the second chamber, of the first chamber, a connecting valve is arranged on the outer portion of the cylinder body, a second channel is arranged on one side, away from the first chamber, of the second chamber, the second channel is communicated with an oil outlet end of the first oil inlet and outlet channel, and an air inlet and outlet hole is arranged on one side, close to the first chamber, of the second chamber.

4. The ultralow frequency cyclic load creep test system according to claim 1, wherein a balance cavity is further provided in the pressure chamber body, the balance cavity is provided between the axial pressure cavity and the confining pressure cavity, the confining pressure cavity and the balance cavity are communicated through a piston channel, and the piston channel is provided inside the piston.

5. The ultra-low frequency cyclic load creep test system according to claim 4, wherein the piston is adapted to define the balance chamber as a third chamber and a fourth chamber, wherein,

The third chamber is provided with a balance chamber exhaust hole which is used for exhausting air in the third chamber;

The fourth chamber is close to the shaft pressure cavity, and the pressure liquid in the confining pressure cavity enters the fourth chamber through the piston channel.

6. The ultralow frequency cyclic load creep test system according to claim 1, wherein a heating member for adjusting the temperature of the pressure liquid and a temperature sensor for monitoring the temperature of the pressure liquid are provided around the sample mounting position.

7. A test method of an ultralow frequency cyclic load creep test, characterized in that a booster cylinder of the test method comprises a cylinder body and an adjusting piston, the adjusting piston is arranged in the cylinder body, the adjusting piston limits the cylinder body into a first chamber and a second chamber, the pressure of the first chamber is larger than that of the second chamber, and the test method is applied to the ultralow frequency cyclic load creep test system of any one of the above claims 1 to 6, and comprises the following steps: