| The natural rock mass has a variety of fractures with different depths and different shapes after being subjected to various geological functions.And many of the large engineering rock masses also contains a lot of disorganized fractures,such as dam base rock,high steep slope rock mass and nuclear waste disposal repository.The existence of these fractured rock masses will affect the properties of strength and creep of rock mass,even the long-term stability.It will cause deformation,instability and failure of rock mass,which will bring unpredictable consequences to safety production and construction and people's life.Therefore,it is of great significance to carry out the experimental study on creep properties of fractured rock-like with different dip angles and penetration degrees.This paper is based on the national natural science fund project"The study of asphalt,rubber and soft rock rheological softening theory and similar simulation"?51074094?and"The study on the theory of solid flow transformation and energy consumption in multi-field coupled deep soft rock"?51374134?.This paper adopts the research method combining indoor test research and numerical simulation.The test of uniaxial and tri-axial compression failure and creep and splitting carried out for the standard cylindrical rock-like specimens made of mud and river sand.Analyzing the deformation and strength properties,failure form,crack propagation regulation and creep properties of fractured rock-like specimen under different dip angles and penetration degrees.According to the indoor creep test results under uniaxial and tri-axis loading and unloading conditions,the suitable creep constitutive model selected.The creep simulation of specimens is carried by the finite element analysis software ANSYS,realizing a numerical simulation study of the creep test with the same condition as indoor creep test.The main research content and achievements of this paper are as follows:?1?The preparation of standard cylindrical similar rock specimens.In the preparation stage of test,based on relevant literature at home and abroad and summarizing the previous research results.According to the principles for the selection of similar materials to selecting cement and river sand as similar material of soft rock,the three similarity theorems used to verify the feasibility of making standard cylindrical similar specimens with cement,river sand and water.Finally,the crack specimens with different dip angle and penetration prepared with the specimen mold containing single crack and numbered accordingly.?2?The influence of crack dip angle and penetration degree on the strength,deformation and failure characteristics of rock with single crack under uniaxial and tri-axi compression.Through the uniaxial and tri-axi compression failure tests on the prepared single crack rock specimens,the stress-strain whole-course curve,peak strength,elastic modulus and the rule that the failure mode of the specimen changes with the crack dip angle and penetration are analyzed.And the variation of mechanical parameters with dip angle and penetration under uniaxial and tri-axi compression is compared and analyzed.It found that the influence of crack dip angle and penetration on the mechanical parameters of similar rock specimens is significant,but the influence of the two on the peak strength,elastic modulus and failure mode is not the same.Finally,according to the uniaxial and tri-axi peak strength and compression test conditions,using Excel software to make the corresponding Mohr stress circle,combined with mole-coulomb formula to solve the internal friction angle?and cohesion C of the composite specimens with different dip angles and penetrations.?3?The effect of crack dip angle and penetration on the mechanical parameters of specimens under uniaxial compression after uniaxial and tri-axi creep.Uniaxial compression test carried out after uniaxial and tri-axi creep test carried out on the composite specimens with different dip angles and penetrations.The change rule of creep behavior under the action of medium and low stress level on the mechanical parameters of the specimens analyzed.It was found that uniaxial creep behavior at low stress level can degrade small inclination specimens and strengthen large inclination specimens in terms of peak strength.The effect of uniaxial and tri-axi creep behavior on peak strength,modulus of elasticity and crack propagation is different under medium and low stress.?4?Under the condition of uniaxial and tri-axi creep tests,the crack dip angle and penetration degree used to study the creep behavior of single crack similar rock.Firstly,analyzing the classical creep time curve,the combination of empirical formula and model method of experimental method commonly used in creep analysis and the creep equation of various complex models studied and deduced.Secondly,direct test and parameter inversion discussed.Finally,the uniaxial and tri-axi creep tests of the composite specimens with different dip angles and penetrations under graded loading show that the influence of dip angles and penetrations on the uniaxial steady creep rate is relatively simple.When the influence of dip angle on the uniaxial steady-state creep rate discussed,the dip angle plays a leading role,and the impact of penetration be neglected.In other words,under the conditions of 25%,50%,75%and 100%penetration,the uniaxial steady-state creep rate decreases with the increase of crack dip angle.When discussing the influence of penetration on uniaxial steady-state creep rate,penetration plays a leading role and the influence of dip angle is relatively weak.That is to say,uniaxial steady-state creep rate of each dip angle specimen firstly increases,then decreases and then increases with the increase of penetration.The influence of crack dip angle and penetration degree on the tri-axi steady-state creep rate is significant and complex.?5?Curve fitting and numerical simulation analysis of uniaxial and tri-axi creep tests of rocks with single crack.Origin data processing software used to fit the test data and the feasibility of the empirical creep formula to simulate rock creep verified.It found that the empirical formula??=(6+(7(?8? of power function fits well with the stage of steady creep and is an ideal creep curves fitting model.The appropriate creep equation was selected and the finite element analysis software ANSYS was used for the numerical simulation study.The displacements,stress and creep distribution laws of the composite specimens with different dip angles and penetrations analyzed.It found that the stress concentration and large displacement area under creep distributed near the crack tip,which is consistent with the failure mode and crack initiation and propagation law of specimens under uniaxial and tri-axi compression test conditions.It indicates that the defect area is prone to stress concentration and large deformation.The defect area should be the focus area in the excavation and support of geotechnical engineering.At the same time,numerical simulation results coincide with the model test results,which confirms the feasibility and correctness of rock-like model test and ANSYS numerical simulation.It has certain guiding significance for the design,construction and support of geotechnical engineering. |
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