Experimental Study On Scale Effect And Mechanical Properties Of Red Beds Soft Rock Filling Material

As the engineering filling material,the red beds soft rock had the characteristics of natural disintegration,which would bring about hidden dangers and cause huge losses to the engineering construction.And,the red beds soft rock need to be studied in depth.Red beds soft rock filling material belong to special coarse-grained materials,scholars and practitioners always had paid attention to the mechanical strength and scale effect of red beds soft rock.In order to carry out laboratory tests on the mechanical properties of red beds soft rock,the filling material should be scaled firstly.The red beds soft rock had strong disintegration,traditional scale method could not evaluate the scale effect effectively.For the question above,this thesis mainly completed the following works:Firstly,Based on the study of the red beds filling material formation process,it was found that the fractal theory could effectively describe the repetitive and selfsimilar features in the red beds soft rock disintegration and crushing.And,it provided theoretical basis for the research on the preparation of red beds soft rock scale sample and established the relationship between scale sample and raw materials.Secondly,in order to solve the scale sample preparation problem of soft rock filling material for indoor experiments,the new scale sample preparation method using ball mill was studied based on fractal theory.Based on the requirements to simulate the field crush mechanism,the ball mill was selected to prepare the scale sample raw material.And the effect of secondary crush on the filling material during the preparation of triaxial specimen was studied.A new method on preparing scale sample which had the same fractal dimension with the original filling material was established.Thirdly,a large number of static triaxial tests were conducted to investigate the influence of the scale effect of red beds filling material on its strength and deformation characteristics.The strength and deformation characteristics of red beds soft rock with the same fractal dimension and different maximum size were obtained.The relationship between the maximum particle size of the red beds filling material and the strength index was obtained.Finally,the E-B constitutive model was used to analyze the triaxial shear test results about the red beds soft rock filling material.Then the E-B model was improved,the difference between the E-B model and the test results was analyzed.The comparison between the theoretical and experimental results shows that the improved model simulates the experimental results more effectively,and the new parameters have physical significance.The results can provide reference for engineering practice and numerical simulation of red beds soft rock filling material.