Analysis Of The Anisotropism And Strength Characters Of Jointed Rock Mass

ABSTRACT:Rock mass has suffered from two geological processes, such as complicated structure and transform in the process of its formation and existence,during this term,it generated a variety of structural plane of different types and sizes,for instance,joints,faults,schistosity,bedding,cracks,etc.By cutting function of these structural planes,the rock mass forms a unique split structure.Thus,when the jointed rock mass contains a minority or majority uneven distribution of joint,its strength shows anisotropic characteristics,and the anisotropy and strength characteristics of jointed rock masses are controlled not only by the rock types of rock mass,but also mostly controlled by the joint plane of rock mass and the rock mass structure formed by the joint plane.The main research content of this article is separately analyzing the anisotropic characteristics of joint rock mass especially the anisotropic characteristics of strength in theory by reading a large number of references,by using the3DEC numerical analysis method in this paper,the anisotropic strength characters of jointed rock mass is studied from the macroscopic aspect.In the case of different joint plane angle,the anisotropic strength characters of jointed rock mass is studied during the jointed rock mass contains single joint,one set of joints, two intersecting joints, multiple intersecting joints or under different confining pressure,the anisotropic strength characters of jointed rock mass is also studied when it contains joints with different spacing or when it has different number of joints.In this paper, the main results of the study are summarized as follows:(1) The existence of joints makes the strength of jointed rock mass show a significant anisotropic character,it weaks the compressive strength of joint rock mass in different degree,the occurrence of the joints,different space distribution or the effect of confining pressure also have a certain influence to the anisotropic strength characters of jointed rock mass.(2) The existence of joints makes the strength of jointed rock mass show an anisotropic character,and with the increase of the number of joints and the decrease of joint’s spacing,the strength of the rock mass with a single set of joints also gradually become smaller,and the anisotropic characteristics of rock mass become more and more obvious. If the joint’s spacing is more smaller,the amplitude of rock mass strength’s reducing will become bigger and bigger,the decrease of the rock mass strength presents a nonlinear change law.(3) The anisotropic characteristics of the strength of joint rock mass has been changed due to the existence of confining pressure.With the increase of confining pressure,the strength of the joint rock mass increases,the anisotropic coefficient decreases, and the degree of anisotropy subsides,the joint rock mass is transformed from anisotropic to isotropic.When the confining pressure increases,the strength of joint rock mass will increase,but the increase is not a linear relationship,the strength increases rapidly when it is at low confining pressure and increases slowly when it is at high confining pressure.(4) When the rock mass contains multiple intersecting joints,the change of the amplitude of the the jointed rock mass strength is smaller with the change of joint angle,the curve is relatively flat,the anisotropic coefficient becomes small.When rock mass contains four or more intersecting joints,the degree of rock anisotropy is not obvious,we can approximately treat it as an isotropic body.But because of the existence of the joints and the influence between them,the strength of the rock mass has been greatly reduced.