Research On Experiment And Numerical Simulation Of The Propagation Process Of Specimen With 2d Cracks Under Biaxial Loading And Water Pressure

Widely exists in the nature of rock cracks,voids,etc is not only by itself in the process of diagenetic environment(physical,chemical,etc.),and also affected by the external environment(tectonic movement,earthquake,volcanic eruption,etc.).Under the action of external load,rock randomly around the tiny defects in each other's extension,well versed in,eventually influence and cause material damage evolution and failure pattern.And rock as a underground railway,tunnel,water conservancy and hydropower engineering of large-scale engineering is closely related to human life the most important materials,studies the deformation of the rock and its failure mechanism for solving related to underground engineering disasters is of great significance.Predecessors' research focuses on uniaxial and conventional triaxial,because most of underground engineering in stress state,the study under the action of two-way axial compression of rock specimen with crack extension mechanism and damage rule is very necessary.Moreover,as the scale of the project grows,the underground adit is not only affected by the upper part of the rock,but also the groundwater is affecting the stability of the underground chamber.Therefore,it is also necessary to carry out the damage law and study of the crack rock mass under water pressure and axial pressure.As made up of concrete containing 3 d built-in fractures of type of rock specimens under the action of water pressure and axial compression experiment phenomenon is not convenient for observation,this paper USES the class containing through fracture rock specimen as the research object,studied under the action of axial pressure and water pressure,including through fracture of crack in rock specimen of crack,expansion and destruction law.The main tasks of this article are:(1)In the experiment,the problem of the original testing machine was found,the test machine exists eccentric defect.I come up with a specific improvement measures:the loading end of the original testing machine are removed,by replacing fixed with spherical hinge,it eliminates eccentricity in the experiment,the whole device has the advantages of simple operation,high test precision and can meet the experimental requirements very well.(2)Specimens make up of cement mortar are made,and use the improved machine carried out the experiment.By applying different lateral pressure,it can be found that when the lateral pressure is zero,the expansion direction of the crack is extended in the direction of maximum pressure stress.The peak strength of the specimen is decreased with the increase of the number of pre-set crack.When the number of pre-set cracks are certain,the peak strength of the specimen is decreasing with the increase of the pre-set crack angle.And,as the number of crack increased,the order of the expansion of wing cracks changed.When the lateral pressure is 10%of uniaxial peak strength,with the increase of lateral pressure,the stress of crack initiation increase gradually,the damage form of specimens also make a difference.Overall,propagation rule of the crack under uniaxial compression and biaxial compression are the same,crack initiation and propagation is mainly based on the original crack tips,but it clearly shows that the crack propagation rate under biaxial compression are delayed.(3)The destructive mechanism of rock under water-rock coupling was carried out in this paper.Firstly,take lots of try to the raw material of cement mortar specimens,after many experiments,determine to mix Silicon alkyl hate water agent in cement mortar finally,the ratio can work well,secondly,water will drain away from cement mortar from the pre-set crack under applied water pressure,so I designed a set of mould that can use to research water-rock coupling,the mould maintain injected water sealing in the interior of the specimen,so as to ensure the experiment completed.(4)In this paper,the compression experiment with the coupling of water-rock was carried out.Experimental results show that the existence of the internal water pressure can accelerate the failure process of rock and decrease the peak strength of the specimens,the reason is due to the existence of the internal water pressure changes the stress field within the scope of the pre-set crack,so that the beginning rate of the crack initiation becomes faster than no water pressure,after crack initiation of pre-set crack specimen,and the jacking and wedging effect of the water also accelerate the failure process of the specimens.(5)Using improved elastic brittle constitutive model that dependents residual standards based on the tension-shear failure,simulates the process of initiation and propagation of the fracture specimen under the different lateral pressure.The crack initiation and the extension process of cracks in three different lateral pressures are analyzed.It is found that the existence of the lateral pressure will delay crack initiation and failure process of the specimens,and with the growing lateral pressure,the destruction of the specimens is delayed,and the greater the peak strength becomes.(6)Improved elastic-brittle model are used to determine the mechanical parameters of the joint rock within the scope of main underground cavern,and using the geological parameters from the numerical simulation to analysis the stability of cavern after excavation.