Experimental Research On Anisotropic Mechanical Behavior Of Weak Rocks With Lamellar Fabric

In underground engineering of mines and water conservancy,we often encounter weak schist with flaky fabric.The physical and mechanical properties of this type of schist are closely related to the geometric and mechanical properties of the flaky structure,and have significant anisotropy characteristics.It helps to understand its engineering characteristics,especially to guide the corresponding engineering design,construction and stability analysis and prediction,which has far-reaching and important engineering value and theoretical significance.Taking the chlorite with flaky fabric in the Tangxian-Shang City tunnel of the northern Hubei water resources allocation project as the research object,taking the anisotropic physical and mechanical properties as a breakthrough,chlorite physical and mechanical experiments were carried out.First of all,in terms of physical properties,XRD method and polarized light microscopy test technology are used to determine the mineral composition and mineral structure of chlorite under different degrees of weathering.Based on the SEM study of the differences in the microstructure,the research shows that chlorite has a flaky shape.The composition of the transversely isotropic material,and its different weathering state leads to a qualitative change in the internal mineral composition.Secondly,in terms of mechanical properties,single-axis,three-axis and acoustic emission test studies were carried out for the angle effect,weathering effect and water softening effect,and the particle flow discrete element method was used to interpret the lamella structure in each experiment.The influence mechanism on strength,deformation and failure mode.Studies have shown that:(1)The schistosity angle leads to significant transverse isotropic mechanical behavior of chlorite,and its mechanical parameter anisotropy grade belongs to low anisotropy rock mass,and the schistosity structure induces chlorite anisotropy.The main internal cause of damage;(2)Experimental research combined with particle flow discrete element numerical simulation revealed that the chlorite with significant schistosity is mainly sheared during loading;under triaxial loading,confining pressure not only affects the rock There is an impact on the compressive strength of the sample,and it will also affect the fracture mode of the rock sample;(3)A uniaxial compression acoustic emission test was carried out to study the damage mechanism under the control of the schistose structure.Studies have shown that different schistosity rock samples have different acoustic emission energy and release rate,and different b-values,which are manifested as differences in compressive strength.In short,through physical,mechanical experiments and numerical simulation studies on chlorite with lamella structure,it is found that the core controlling factors of anisotropic strength and fracture mode of chlorite are schistoscopy and the degree of weathering leading to the mineral composition of chlorite.Difference,the degree of water softening process between different minerals and water,among which schistoscopy is the most core controlling factor,which means that the schist flake structure factors should be considered when evaluating the engineering mechanical behavior of schist,such as the response of underground engineering excavation In order to better analyze the stability of schist and the causes and conditions of deformation failure and instability,it is necessary to deeply study its control effect on the strength,deformation and failure mode of schist,so as to effectively guide the scientific analysis and design of underground engineering.