| Structural plane refers to the material interface with a certain direction,scale and shape,such as layer,bedding,joint,etc.,which exist in the rock mass.The instability failure of the rock mass is often not caused by the failure of the material itself,but the instability failure occurs along the structural plane inside the rock mass.The mechanical properties of discontinuities control the mechanical properties of engineering rock masses to a certain extent,and the shear strength of discontinuities is one of the most important mechanical properties of discontinuities.Therefore,research on the shear strength of discontinuities is carried out for the stability of rock masses.The evaluation of sex has important theoretical and practical significance.There are many factors affecting the shear strength of structural planes in nature.Because the surface characteristics of structural planes are difficult to accurately express with simple mathematical relations,scholars at home and abroad have simplified the surface morphology of structural planes into regular sawtooth structural planes.Research on the influence of structural plane morphology on the shear strength of structural plane.In addition to the influence of structural plane morphology,structural planes in rock masses will be affected by weathering in the natural environment,and the impact of weathering on the shear strength of structural planes cannot be ignored.Regarding the research on the shear strength of structural surfaces,the most representative ones are the three shear strength formulas of Patton,Barton,and Landanyi.Among them,Patton and Landanyi simplified the undulating structural surface surface morphology into a regular zigzag structural surface.Based on the analysis of the shear strength characteristics of the structural surface,most of the subsequent research scholars on the shear strength of the structural surface are also carried out on this basis.Barton considers the impact of weathering on the shear strength of the structural surface through the strength of the two walls of the structural surface(JCS).Therefore,in order to study the influence of weathering on the shear strength of structural surfaces,through indoor weathering simulation tests,the influence of weathering on the strength of limestone was studied,and the relationship between the degree of weathering and the strength of limestone rock walls was established.An experimental study on the shear strength of saw-tooth structural surfaces with different weathering degrees was carried out,the influence of weathering on the shear strength of limestone structural surfaces was studied,and the relationship between the degree of weathering and the shear strength of saw-tooth structural surfaces was established.Based on the Patton formula and Barton formula,respectively,the shear strength estimation model of the sawtooth structure surface under the influence of weathering is established.The main conclusions of this research are as follows:(1)Through indoor rock weathering test,it is proposed to use wave velocity ratio to quantitatively characterize the degree of limestone weathering,and obtain limestone samples with different degrees of weathering.Combining the resilience test and shear strength test of limestone rock,test and analyze the change law of limestone strength with different weathering degrees,establish the relationship between wave speed ratio and limestone strength,and realize the quantitative relationship between weathering degree and limestone strength It also gives the suggested values of mechanical parameters of limestone with different weathering degrees.(2)Through the indoor limestone structural surface weathering test,the saw-tooth structural surface samples with different weathering degrees are obtained,combined with the indoor structural surface shear strength test,the basic research on the mechanical properties of the saw-tooth structural surface is carried out to analyze the sawtooth structure The changing law of the shear strength of the surface under different weathering degrees is established,the relationship between the weathering degree and the shear strength of the structural surface is established,and the mechanical parameters of the sawtooth structural surface of limestone are suggested.(3)Use UDEC numerical calculation software to establish a two-dimensional numerical model of the saw-tooth structural surface,carry out numerical simulation research on the shear test of the saw-tooth structural surface,and further analyze the shear failure mode and failure of the saw-tooth structural surface from the perspective of the displacement field.In the evolution process,the indoor structural surface shear test was supplemented and deepened.(4)Based on the shear strength estimation model of Patton zigzag structure surface and the shear strength estimation model of Barton structure surface respectively,combined with the test results of the zigzag structure surface shear strength of different weathering degrees,a zigzag structure considering the effect of weathering is established Surface shear strength estimation model.By comparison,it is recommended to adopt an improved structural plane shear strength estimation model based on Barton formula. |
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