Damage Analysis And Failure Prediction Of Jointed Rock Mass

Jointed rock mass is a kind of common complex media in nature,which has strong heterogeneity and discontinuity.Due to the formation conditions and geological movement,the jointed rock mass contains a large number of complex interlaced cracks,and the existence of cracks has a significant impact on the physical and mechanical properties of rock mass,which brings safety risks to the construction of various rock mass engineering(such as rock slope,foundation pit,etc.).Some studies have shown that the failure mode of jointed rock mass is mainly affected by the joint dip Angle.Therefore,it is of great significance to study the damage and failure law and instability prediction of rock mass with different joint dip Angle to ensure the safe construction and stable operation of geotechnical engineering.For this reason,this paper carried out uniaxial compression test and acoustic emission(AE)test on the common yellow sandstone in Hunan,and the mechanical properties,deformation and failure laws of jointed rock mass under uniaxial compression were studied.The damage analysis and failure instability prediction of jointed rock mass were carried out by using acoustic emission technology and theory,which provides some guiding suggestions for engineering practice.The main research contents and conclusions are as follows:(1)The stress-strain characteristics and failure modes of jointed rock mass were obtained by uniaxial compression failure test.Under the influence of joints,the strength and stiffness of rock mass are weakened in varying degrees compared with that of intact jointless rock mass.The strength and modulus of elasticity of jointed rock mass change in the same trend,and the distribution of strength and modulus of elasticity of jointed rock mass is open-ended upward parabola with the increase of joint dip angle.Among them,the strength and modulus of elasticity of jointed rock mass with 45 degree dip angle are the lowest.There are two failure modes: tension failure along the cut joint surface and shear failure along the joint surface.In the process of joint dip increasing from 0 to 90,the failure mode of jointed rock mass gradually changes from tension failure along the cut joint plane to shear failure along the joint plane,and the 45 joint dip is the critical angle value of the two failure modes.(2)The corresponding relationship between AE characteristic parameters(ringing counting rate and energy counting rate)and several stages in the rock mass failure process is obtained through the detection and analysis of acoustic emission data.The continuous sharp increase of the ringing counting rate and energy counting rate can be used as the precursor of time failure.The acoustic emission damage constitutive curve is in good agreement with the test curve of jointed rock mass,indicating that the acoustic emission signal is consistent with the internal damage of jointed rock mass,and the intensity and stress state of jointed rock mass can be estimated by using acoustic emission characteristic parameters.(3)By fitting the relationship between bell counting rate and time,and combining with cusp catastrophe model,the failure of jointed rock was predicted and analyzed.The results show that the prediction results of acoustic emission characteristic parameters for jointed rock failure are basically consistent with the actual situation.The results show that the predicted results of acoustic emission characteristic parameters are basically consistent with the actual situation.In most cases,it can be predicted in advance,but there are a few cases where the predicted results are not ideal.For example,the rock mass will be destroyed when the catastrophe model just enters the unstable state.Therefore,the safety and stability of jointed rock mass should be evaluated by combining the acoustic emission constitutive relationship of jointed rock mass.