215 results about "Triaxial compression" patented technology

The invention discloses a rock test piece die for triaxial compression test on an intermittent double-fracture rock. The rock test piece die for the triaxial compression test on the intermittent double-fracture rock comprises a base and a middle frame die arranged on the base, wherein a gland is arranged on the top of the middle frame die; the middle frame die consists of two modules which are symmetrically buckled together and are provided with semicircular slots; fixing lugs are symmetrically arranged on the side walls of the two modules respectively; a bolt for integrally fixing the two modules is sleeved with the fixing lugs in a penetrating manner; rectangular wide slots for enabling a rectangular steel sheet to penetrate through and be positioned between the two modules are formed in the middle parts of the two modules. Compared with the prior art, the rock test piece die has the advantages of simple structure, easiness in machining, convenience in dismounting and mounting and fracture positioning accuracy; the precision and the efficiency for preparing a intermittent fracture rock material test piece.

The invention relates to a device and a method for measurement, in particular to the method for calculating the mechanical properties of a series of rock sample materials by recording relationships between testing forces / loads and indentation depths / displacements at different moments. The device comprises a rack, a DC motor, displacement measurers, a rigid flat-bottom pressure head and a sample fixing station, wherein the rack is divided into two layers; the upper layer of the rack is provided with the DC motor of which one end is connected with the rigid flat-bottom pressure head; the displacement measurers are distributed about the rigid flat-bottom pressure head; and the sample fixing station is fixed on a base of the lower layer of the rack. The reliability and effectiveness of the method can be evaluated by comparing basic rock mechanical property measurement results with those obtained by other conventional testing means. In addition, compared with conventional mechanical test methods such as single-pressing tests, single-pulling tests, triaxial compression tests and the like in laboratories, the method has the advantages of short test process, simplicity and convenience of operation, low requirements on samples, economy and the like.

The invention provides a method for measuring a shale brittleness index based on triaxial compression complete stress-strain curves and ultrasonic longitudinal wave speed. The method comprises the following steps: obtaining a triaxial compression complete stress-strain curve and the ultrasonic longitudinal wave speed of each time point in an experimental process by adopting dynamic and static combined triaxial compression experiment; determining a time point when a shale microcrack starts to be damaged by utilizing a change curve of the longitudinal wave speed; according to the change of the longitudinal wave speed and the shape of the complete stress-strain curve, dividing the complete stress-strain curve into four stages, namely, a stage of microcrack closure, a stage from compaction to starting of microcrack damage, a stage from microcrack extension to damage instability and a stage after rock damage instability; by utilizing the complete stress-strain curve, calculating the unit volume energy absorbed by a shale test piece in the corresponding stage; calculating the shale brittleness index by utilizing the ratio of the unit volume energy absorbed in the elastic stage to the absorbed total unit volume energy. The method is a comprehensive calculation method considering mechanical properties of shale in each stage and improves the accuracy and reasonability of rock brittleness evaluation.

The invention relates to a dynamically-disturbed low-temperature rock triaxial loading and unloading rheometer and test method. The rheometer comprises a dynamic disturbance system, a frame, a guide rail, a lifting mechanism, a pressure chamber, a trolley, a temperature control system, an axial loading system, a confining pressure loading system, a measuring system, a control system and a computer and software system, a loading cylinder in the axial loading system can switch between a lead screw booster and a servo valve through a switching valve, a servo oil source, a servo valve and a loading cylinder are communicated through the switching valve when a conventional triaxial compression test is performed, the lead screw booster is communicated with the loading cylinder through the switching valve when a triaxial rheological test is performed, and rock samples are subjected to dynamic disturbance by the aid of a weight dynamic disturbance system or an impacting cylinder disturbance system. The rheometer effectively achieves rock triaxial loading and unloading rheological tests and conventional triaxial compression tests under the conditions of negative temperature and dynamic disturbance and is simple in integral structure principle, variable in function and high in applicability.

The invention provides a triaxial compression rheological test system capable of simulating an engineering geological environment, belonging to rock material compression experimental facilities. The remarkable characteristics of the invention are as follows: a test chamber in the triaxial compression rheological test system capable of simulating the engineering geological environment can depend on a normal rheological compression test device to realize the analogue simulation of the variations of a temperature field, a humidity field and a chemical field in the engineering geological environment by utilizing a humidifier, a heater and a fluid tank. The device fundamentally solves the problems of larger deviation of rock mechanics parameters obtained by a laboratory test and a field in-situ test and analogue simulation of a geotechnical wall-rock multi-field coupling environment. The test system has compact structure and low cost, is rather easy to install and dismount test pieces, detectors, pipelines and lead wires, and has stronger adaptability on the test pieces with different lithologies and sizes, thereby providing a set of complete technology and means for the study on the mechanical behavior of the wall-rock stability under a complex engineering geological condition.

The invention discloses a method for establishing a rock damage constitutive model based on least energy consumption principle, the method is as follows: a damage evaluation equation is deduced based on the least energy consumption principle; the rock damage constitutive model is established in a continuum damage theoretical framework by combination of the damage evaluation equation; the theoretical relation between deformation parameters of and parameters of the model is deduced, and conventional triaxial compression tests of the rock under different confining pressures can be performed to obtain strain-axial and radial strain relation curves of a specimen under corresponding confining pressures and mechanical strength parameters and strain parameters of the rock specimen; and by experimental results damage threshold can be determined, and the model parameters can be identified. The damage threshold in the rack damage evolution law can be determined by combination of the model and the dilatation startup property of the rock, the proposed model can better reflect the nonlinear mechanical behavior of a rock material under complex stress conditions, the constitutive model influenced by the damage threshold has higher fitting precision on the post-yielding section of the rock material, and the constitutive model has great reference significance and application value to the safety analysis of rock engineering under the complex stress conditions.

The invention discloses a multifunctional true triaxial rock creepmeter, comprising a base, a test piece mounting base arranged on the base, two groups of horizontal direction stress loading systems with the same structure, a vertical direction stress loading system and a creep data measuring system. The multifunctional true triaxial rock creepmeter disclosed by the invention can carry out a single-axis pulling and pressing creep test and also can carry out a true triaxial compression, pulling and pressing combined creep and unloading-creep test which simulates three-dimensional stress state and loading and unloading stress path of a natural geological rock mass and an engineering rock mass and maintain tension stress states in one or two directions unloaded to the rock; and test function is more comprehensive, practicability is stronger, and a pulling and pressing combined creep and stable pressing and pulling stress conversion unloading-creep test is realized; a pull pressure loading system can provide a pressure which is high enough to meet creep test requirements of most rock materials, and a long-term constant load can be provided; and the multifunctional true triaxial rock creepmeter disclosed by the invention has the characteristics of having a simpler structure, hardly consuming energy source in a test process and having low test cost.

The invention relates to a method for establishing damaged rock constitutive relation by utilizing residual strength. The method comprises the following steps of: carrying out a rock indoor triaxial compression experiment, measuring the axle load sigma1, the confining pressure sigma 3, the peak value intensity strain Epsilon 1c and the residual intensity sigma r of a rock sample, calculating the rock elastic modulus E and poisson ratio Mu, carrying out data regression according to triaxial compression test results, and calculating the uniaxial compressive strength sigma ci and an experience intensity parameter mi of a rock block; then establishing a three-dimensional damage statistic constitutive relation capable of reflecting a rock post-peak softening characteristic; and finally, solving constitutive relation parameters n and F0 according to four boundary conditions of a rock full-stress-strain curve geometric characteristic, and drawing a constitutive relation curve by utilizing Matlab software. The constitutive relation can fully reflect rock post-peak softening and residual intensity characteristics, and can describe the full-stress-strain relation of the rock damage process well, so that a theory formula well corresponds to the actual condition of a rock material; and the method can be realized simply, is widely applied to the theory analysis of the rock material, and has an actual value.

The invention discloses a temperature control-based dry-wet circulating unsaturated soil triaxial instrument and belongs to the technical field of geotechnical engineering test instruments. The triaxial instrument comprises a triaxial instrument main body, a temperature regulating system, a pressure regulating system, a humidity regulating system and a data analyzing system. The temperature regulating system and the humidity regulating system control the temperature and humidity in a test environment. The pressure regulating system controls the axial pressure and the confining pressure and cooperates with a gas-supplying assembly to ensure the stability of the pressure chamber confining pressure. The triaxial instrument realizes control of the environment temperature. Through control of the environment humidity of the triaxial compression test, the triaxial instrument can realize a triaxial shearing test of unsaturated soil dry-wet circulating. The test environment temperature and humidity are controlled simultaneously and the mechanical evolution characteristics of unsaturated soil under coupling action of the temperature and humidity are researched. Through a senor and a data acquisition device, the test data can be measured and acquired and then be subjected to intelligent processing so that the automation of measurement and acquisition is realized.

The invention discloses a rock triaxial compression acoustic emission test system, comprising a mechanics testing system (MTS) 815 rock servo test system, wherein a triaxial chamber of the system is internally provided with an upper pressure head and a bottom pressure head; an acoustic emission detector is arranged in the bottom pressure head; a shield signal of the acoustic emission detector penetrates out the triaxial chamber from a reserved communication channel of a base of the system; and a shield signal line is connected with a preamplifier, so as to realize outdoor transmission of a detection signal of the acoustic emission detector. By utilizing the rock triaxial compression acoustic emission test system disclosed by the invention, the acoustic emission signal can be monitored more comprehensively and truly; and the test system can be used for providing a more reliable test method and test results for predicating rock fracture, so as to prevent mine disaster accidents generated in rock body fracture.

The invention provides a triaxial tensile testing device and method for rocks. The triaxial tensile testing device comprises a follow-up interlocking device for enabling a loading platform to do freemovement along a piston of an actuator, a step type strip-shaped sliding rail and a multi-degree-of-freedom axial direct tensile clamp mounted in a triaxial chamber of a testing machine. The device provided by the invention is simple in structure, reasonable in design and simple and convenient to machine and produce, and use and operate; testing researches of triaxial tensile mechanical propertiesof the rocks under various complicated conditions can be conveniently, rapidly, stably and reliably finished by utilizing rock triaxial compression testing machines including an MTS815 type and the like, which only can be used for carrying out a rock test piece triaxial compression test, through the follow-up interlocking device and the multi-degree-of-freedom axial direct tensile clamp.

The invention discloses a design method for property parameters of anti-collapse drilling fluid for fractured formations. According to sequence, the design method includes the following steps: core samples are prepared; four of the core samples are chosen for a triaxial compression test and an acoustic emission test, and the crustal stress of a formation owning the core samples is determined; two of the core samples are chosen for the triaxial compression test, and the cohesion and internal friction angle of the weak planes of the rocks are tested; eight of the core samples are chosen to be put into the drilling fluid, the triaxial compression test is carried out after the core samples are soaked for different times, and the cohesion and internal friction angle of the weak planes of the rocks are tested; the cohesion and internal friction angle of the weak planes of the rocks are respectively linearly fitted to soaking times; the fluid-solid coupling theory is utilized to create a fractured formation well surrounding rock stress distribution model; the elastic mechanics coordinate transformation theory is utilized to create a fractured formation weak plane destruction model; a relation chart between the property parameters of the drilling fluid is determined. The design method disclosed by the invention can quantitatively optimize the key property parameters of the drilling fluid according the requirement of a site for well wall stability.

The invention discloses a method for forecasting a weak plane formation collapse pressure equal yield density window. The method sequentially includes the steps: dividing a weak plane formation into a compact section and a crack section according to characteristics of the weak plane formation; testing the strength of a rock body and the strength of a weak plane of a rock by the aid of the triaxial compression test of the rock; inverting stress distribution and pore pressure distribution of surrounding rocks of a compact formation well by the aid of a fluid-solid coupling model, and determining the lower limit of the collapse pressure equal yield density of a compact formation according to Mohr-coulomb failure criteria; analyzing the failure state of the surrounding rocks of the weak plane formation well according to the rock weak plane failure criteria, and determining the lower limit and the upper limit of the collapse pressure equal yield density window of a crack formation; building a weak plane formation collapse pressure equal yield density window calculation model, substituting parameter values into the model and then determining the weak plane formation collapse pressure equal yield density window. The weak plane formation collapse pressure equal yield density window can be forecasted before drilling, so that drilling fluid density is reasonably selected, and wellbore instability is effectively stopped.

The invention belongs to the technical field of rock and soil mechanics, and relates to a true triaxial test device for combustible ice sediments. According to the true triaxial test device, the formation process of the combustible ice sediments in a deep sea reservoir stratum can be simulated in a laboratory, a true triaxial compression test is carried out on the combustible ice sediments, and therefore a technical guarantee and support are provided for accurately predicting the strength characteristics of the reservoir stratum and researching the constitutive relation of the reservoir stratum; and in the true triaxial compression test, main stress in three directions can be applied independently, the real stress characteristics of the combustible ice sediments in a bottom layer can be better reflected, but the boundary loading condition problem can be easily caused in the loading process, composite loading plates of rigid plates and deformation plates are adopted in the front-and-back pressurization direction, so that the pressure can be uniformly loaded on a sample through the composite loading plates in the front-back pressurization process, and therefore the problems that mutual interference of loading plates in three-directional loading is caused in the loading process, and loading is not uniform due to the fact that the sample is deformed in the loading expansion processcan be solved.

During triaxial compression test, a soil specimen experiences reduction of its height with simultaneous increase in its diameter. For calculation of new cross-sectional area, it is always assumed that the specimen deforms as a cylinder with uniform increase in diameter through its height. This condition is seldom or never met in actual soil specimens, because specimen undergoes non-uniform increase in diameter through its height and very often with localized bulging in specimen affecting the accuracy of calculation of magnitude of deviator stress at any instant of time during the test. Non-uniform increase in diameter through its height with often localized bulging affects the real strength and volume change characteristics, and how much this effect of non-uniform lateral increase in diameter changes these properties remains unknown. The expandable jacket wrapped around the soil specimen for performing the triaxial compression test included in this invention, shall maintain uniform diameter of soil specimen through its height and shall provide accurate prediction of deviator stress, volume change characteristics and strength of soil specimen. The calibration device for calibration of expandable jacket shall provide the magnitude of correction to be made in deviator stress at various levels of axial and lateral strains.

The invention discloses a construction method for a rock freeze-thaw damage constitutive model under the action of constant confining pressure. Based on a popularized strain equivalence principle, taking the joint action of two damage factors (freeze-thaw cycle and load) into consideration, the invention proposes an expression of a total damage variable. If the strength of a rock element body is subject to Weibull distribution, on the basis of a D-P failure criterion and geometrical conditions at peak points of a rock stress-strain curve, an expression of a random distribution variable F, a distribution parameter m and F0 is obtained, and a rock freeze-thaw damage constitutive model under the action of constant confining pressure is created. A triaxial compression experiment is carried out on a rock under the action of freeze-thaw cycle, and the experiment verifies the rationality of the model. The method disclosed by the invention is a method combined with theoretical derivation and experimental verification. The theoretical curve of the rock damage constitutive model created by the method is identical with the experimental curve, the mechanical behaviors of a rock under various confining pressures and freeze-thaw cycle numbers can be perfectly reflected, and a theoretical guidance is provided for designs and construction of cold-region projects.

The invention discloses a method for constructing an elastoplasticity-damage coupling mechanical constitutive model of a rock material. The method comprises the following steps of obtaining the rock material on an engineering site, and manufacturing a standard cylinder sample; carrying out conventional triaxial compression mechanical tests under different confining pressures; obtaining a rock yield criterion, a plastic hardening criterion and a non-associated fluidity rule in combination with a test result; calculating a rock damage variable according to the stress-strain curve, and obtaininga rock damage evolution equation according to a damage variable-axial strain evolution rule; deriving a constitutive equation based on an elastic-plastic mechanics theory and an irreversible thermodynamic damage constitutive theory; combining the test data to obtain model parameters; writing the mechanical model into a UMAT subprogram, embedding the UMAT subprogram into ABAQUS finite element software, and carrying out triaxial test numerical simulation, so as to verify and improve the model. The method is clear in mechanical significance, simple in parameter acquisition, wide in application range and relatively high in accuracy.

The invention relates to a nonlinear mechanical test equipment for a deep rock body, belonging to the mechanical test equipment for the deep rock body in geotechnical engineering. At present, the conventional rock body mechanical test comprises a unidirectional compression test, a unidirectional tension test, a triaxial compression test and a shear test. The force and the mechanical behavior in the action process of the deep rock body have the very close relations with the loading process. The conventional rock body mechanical test modes and equipments can't reflect the special mechanical behavior related to the loading process of the deep rock body. Therefore, the invention adopts the scheme of that each direction of three dimensions of a hydraulic loading device is provided with an independent hydraulic power control device, and combines the corresponding test piece fixture to provide the nonlinear mechanical test equipment which implements the composite stress test for the engineering rock body, particularly for the deep engineering rock body in order to implement the intensive study for the stress state of the engineering rock body in the process of tension and compression, intensity character of tension and shear composite state, constitutive relation and construction.

The invention discloses a rock brittleness index evaluation method based on a full stress-strain curve. The method comprises steps as follows: the geological environment where a to-be-measured rock sample is located is evaluated in the aspects of ground stress, temperature, water pressure and the like; rock mechanics experiments meeting the geological environment where the to-be-measured rock sample is located are selected and include an uniaxial compression experiment, a triaxial compression experiment with the temperature taken into consideration and a triaxial compression experiment with the water pressure taken into consideration; characteristic stress values and corresponding strain of the characteristic stress values in the experiment process are acquired; the characteristic stress values and the strain are taken in for calculation according to a proposed brittleness index calculation method, and the brittleness index of to-be-measured rock is obtained. The method is a comprehensive brittleness index calculation method aiming at the geological environment where the to-be-measured rock sample is located and based on the whole process of the rock mechanics experiments, and the reasonability and the accuracy of rock brittleness evaluation are improved.

The invention discloses a numerical simulation analysis method for the deformation of a soft soil deep foundation pit. The numerical simulation analysis method comprises the following steps: firstly taking soft soil to carry out a triaxial compression creep experiment in a laboratory before the excavation of the foundation pit, obtaining time hardening model creep parameters of the soft soil through STATISTIC software fitting, in the design stage of the foundation pit, applying large finite element software ABAQUS to build a finite element model, building the influence at the simulation infinity of an infinite element on the excavation of the foundation pit around the model, and obtaining the earth excavation manner and the excavation time of the foundation pit as well as the influence rule of a construction gap for stress and deformation of the foundation pit through analog computation. In the design stage, the construction parameters of the foundation pit, particularly the three important parameters such as earth excavation manner, earth excavation time and construction gap, can be optimally designed. Through the optimization of the three parameters, the deformation and support shaft force of the foundation pit can be effectively reduced, and then the safety coefficient of the foundation pit is increased.

The invention relates to a multifunctional experimental device and method of supercritical carbon dioxide flooded coalbed methane and belongs to the multifunctional experimental device and method of coalbed gas. The device comprises a supercritical medium supply system, a methane supplying and dissolving system, a vacuumizing system, a pressurized flooding extraction system, a separating and collecting system and a signal acquisition system. The supercritical medium supply system and the methane supplying and dissolving system are connected to an input end of the pressurized flooding extraction system, and the pressurized flooding extraction system and the output end are separately connected to the vacuumizing system, the separating and collecting system and the signal acquisition system. The device has the advantages that a multifunctional experiment of flooding the coalbed methane by supercritical carbon dioxide and extracting a coal rock under the action of triaxial compression by means of special physical and chemical characteristics of supercritical carbon dioxide is simple in structure, complete in function and low in cost, and can realize the flooding rate test of methane in supercritical carbon dioxide flooded extraction process, coal rock fracture development rule and stress deformation monitoring and permeability change test before and after extraction.

The invention discloses an improved method for carrying out rock shearing test by using a rock triaxial compression apparatus. An assembled die adopted for test of the rock triaxial compression apparatus comprises a jack pressure head (1), a pressure chamber (2), a pair of rigid stepped cylindrical base plates (5) and a pair of flexible semi-cylinder base plates (6). The assembled die adopted by the invention inherits the advantages of rock triaxial compression test, and steady confining pressure is provided for a rock sample (3) by the pressure chamber (2); according to axial force exerted when a rock sample is damaged and in combination with the elasticity modulus E1 of the rigid stepped cylindrical base plates and the elasticity modulus E2 of the flexible semi-cylinder base plates, pressures F1 and F4 applied by the two rigid stepped cylindrical base plates to the rock sample and pressures F2 and F3 applied by the two flexible semi-cylinder base plates to the rock sample can be computed, so as to further determine the shearing force delta F on the shearing surface of the rock; the shear strength of the rock can be obtained according to the relation between the shearing force and the shearing area on the shearing surface, so that a triaxial tester can be directly used for measuring the shear strength of the rock.

The invention relates to a monitoring apparatus for a charge during a gas or water-contained coal rock triaxial compression and fracture process. According to the invention, a groove is arranged at a bottom in a cylindrical shell (13); a square frustum insulation pad (14) is installed in the groove; a square pressure head (15) is installed on the insulation pad (14); a square coal rock sampling (16) is arranged on the square pressure head (15); a square pressure head (15) and an insulation pad (14) are arranged on the square coal rock sampling body (16), wherein the square pressure head (15)and the insulation pad (14) are respectively the same as the ones under the square coal rock sampling body (16); compressed nuts (4) are arranged on circular beads of position sleeves (3) and are used for threaded connection of the position sleeves (3) on the cylindrical shell (13) fixedly; center holes (1-2) are arranged in a pressure bar; conductive screws (12) are fixed on the cylindrical shell (13); insulation sleeves I (8) are arranged at sealing bolts (7) and insulation sleeves II (9) are arranged at the conductive screws (12). According to the invention, a technical guidance is provided for prediction and control of coal and gas outburst as well as water inrush, so that monitoring on charges during the gas or water-contained coal rock triaxial compression and fracture process can be realized.

The invention provides a rock brittleness evaluation method based on a stress strain curve and a scratch test. The method comprises the following steps that: evaluating rock from a crustal stress environment where the rock is positioned, and pore pressure, and obtaining the stratum condition of the rock; selecting a rock mechanical experiment of the environment where a rock sample to be tested ispositioned, wherein the experiment includes a conventional triaxial compression test or a triaxial compression test which considers pore pressure, and a scratch test; obtaining a pre-peak strain energy density value, a crack initiation stress value, a peak value stress value, a residual stress value as well as corresponding strain size and crack linear density; and determining the value range of an effective stress coefficient [Alpha] from the pore pressure of a tested rock sample, and substituting the pre-peak strain energy density value, the crack initiation stress value, the peak value stress value, the residual stress value as well as the corresponding strain size and crack linear density into a brittleness index calculation formula to obtain the brittleness index of the rock to be tested. By use of the brittleness evaluation method, the accuracy and the applicability of the rock brittleness evaluation can be improved.

The invention provides a rock damage prediction method based on acoustic emission source dominant frequency uniqueness. The rock damage prediction method comprises the steps of preparation of a standard rock test piece, acoustic emission source positioning, acoustic emission source type identification, calculation of acoustic emission dominant frequencies corresponding to different types of sources and rock damage prediction. According to the method, the defects of wide acoustic emission main frequency band and non-obvious acoustic emission main frequency characteristics of an existing rock damage prediction method based on acoustic emission main frequency characteristics are overcome. The method is suitable for predicting rock damage in Brazilian splitting tests, shearing tests and creeptests under uniaxial and triaxial compression conditions.

The invention relates to a squeeze head used for a rock conventional triaxial test acoustic emission test and belongs to the technical field of geotechnical engineering. The squeeze head comprises an upper squeeze head and a lower squeeze head, wherein the upper squeeze head and the lower squeeze head are arranged on a rock message delivery system (MTS) conventional triaxial compression test machine. Round grooves are formed in the lower end face of the upper squeeze head and the upper end face of the lower squeeze head. Two perpendicular installation holes are symmetrically formed in the bottom of each round groove. Perpendicular conductor holes are formed in bottoms of the installation holes. Horizontal conductor holes are formed in side walls of the upper squeeze head and the lower squeeze head, and the perpendicular conductor holes are communicated with the horizontal conductor holes. Springs are arranged at the bottoms of the installation holes. Cover plates are arranged on the round grooves and shapes and sizes of the cover plates are identical to shapes and sizes of the round grooves. By means of the squeeze head used for the rock conventional triaxial acoustic emission test, attenuation and distortion of emission signals can be reduced to the maximum extent, the situation that an acoustic emission sensor is immersed in hydraulic oil is avoided, the acoustic emission test of high confining pressure can be carried out and the facture surface of rock can be positioned.

The invention discloses a self-balancing rock all-end-surface true triaxial compression test device, which consists of a triaxial cell, a four link plate mechanism, a sigma 1 loading transfer system, a sigma 2 loading transfer system and a sigma 3 loading transfer system. The device is characterized in that the sigma 1 loading transfer system is positioned at the upper end of the triaxial cell and is connected with the triaxial cell through a piston in a sigma 1 direction; the sigma 2 loading transfer system is positioned at the side end of the triaxial cell and is connected with the triaxial cell through a piston in a sigma 2 direction; the sigma 3 loading transfer system is connected with the triaxial cell through a drain hole and a water inlet hole; and the four link plate mechanism is positioned inside the triaxial cell. The device can perform a plurality of tests on various rocks, and perform true triaxial compression tests on most of soluble rocks and undissolved rocks; the device can apply unidirectional pressure through water solution, and can perform a stress-dissolution coupling test on the soluble rocks; and the device can apply the stress on all end surfaces of a rock specimen to truly reflect the load bearing state of a rock body; and the test device has a simple structure, is easy to operate, and has a self-balancing function.

The invention discloses a multifunctional unsaturated soil consolidation apparatus and a test method, belonging to the field of geotechnical testing instruments. A thrust bearing, a linear bearing, a self-aligning assembly and an axial pressure sensor are arranged on a loading rod of a consolidation apparatus test platform in a built-in mode, so that the influence of friction force is eliminated during loading; and unnecessary pre-compression on a sample is reduced due to the design of a rotary rigid connection assembly, and the problem that the loading rod and the sample are eccentric due to machining and mounting is solved by virtue of the design of the self-aligning assembly. Meanwhile, according to the optimization design of the structure, the apparatus can be adaptive to multiple loading platforms, and the test can be performed on a conventional saturated soil consolidation apparatus and also can be performed on a triaxial compression tester.

The invention provides an elastoplastic constitutive model of steel fiber reinforced concrete considering fiber slippage. The elastoplastic constitutive model of the steel fiber reinforced concrete is characterized in that the model is as shown in the following formula. According to the elastoplastic constitutive model of the steel fiber reinforced concrete considering fiber slippage disclosed by the invention, composite material mixing theories are used, and steel fiber and matrix concrete constitutive equations are respectively obtained based on a thermodynamic dissipation inequation. Matrix concrete is the elastoplastic constitutive model, and steel fibers are one-dimensional elastic constitutive models considering fiber interface slippage. The plasticity of the matrix concrete adopts Hsieh-Ting-Chen four-parameter yield criteria and Drucker-Prager classic plastic flow rules, and plastic hardening / softening criteria adopt a modified Guo Zhenhai model. The parameters of the steel fiber one-dimensional elastic constitutive model considering an interface are determined through a steel fiber pullout test. The parameters of the concrete elastoplastic constitutive model can be calibrated by uniaxial and true three-axial compression tests. The model considers a steel fiber slip mechanism in the meso-scale, and combines elastic constitutive structures of the ordinary concrete and the steel fibers to construct the elastoplastic constitutive model of the steel fiber reinforced concrete, thereby being simple and feasible, and having important promoting significance to basic theoretical research of the fiber reinforced concrete.

The invention discloses a method for determining fracture pressure of hydraulic fracturing on the basis of a geological strength index, which includes the steps of preparing a standard sample by utilizing an intact coal rock, performing tests for homotaxial and triaxial compression strength, determining a GSI (geological strength index) value of a reservoir according to a geological strength index template, and determining the fracture pressure of the reservoir according to structural characteristics of the intact coal rack and the reservoir which are comprehensively considered. Limitedness that tensile strength tested by the intact coal rock is taken as the tensile strength of the entire reservoir is avoided, structural characteristics of the reservoir are considered, the GSI value is determined according to a rock structure quantized GSI template and a coal structure quantized GSI template, and then the fracture pressure of the reservoir is determined. A new method for determining fracture pressure according to of strength of the intact coal rock and structural characteristics of the reservoir is realized, and the foundation for quick and easy determination for fracture pressure of the reservoir is laid.