Experimental Study On The Shear Properties Of Interface Between Soil-Rock Mixture And Structure

With the vigorous development of China's aviation industry,the number of airport planning construction in China has increased.However,in the construction of airports in Western regions,the terrain of Hilly and mountainous areas is contradictory to the tense land resources,and a lot of high fill slope projects have emerged.Among them,the contact surface between the Soil-Rock Mixture filling and the original surface is the weak surface which is easy to be destroyed in the practical engineering.It is the key research object in the stability of high fill slope engineering.It is the necessary preliminary research work to complete the early warning and prediction of large settlement deformation,landslide and other disasters in high fill slope engineering.In view of the special contact surface between the Soil-Rock Mixture filling and the original inclined ground(removing humus layer),this paper focuses on the nature of the Soil-Rock Mixture itself.With the same contact surface of the lower structure,and using the fractal theory model to control the gradation of different stone content,On the large-scale direct shear test system of ADS-500/HL-200 underground structure,the Soil-Rock Mixture is studied.Large-scale direct shear tests with control variables of rock content,moisture content and normal stress in the test were conducted to analyze the shear characteristics of the interface of different soil-rock mixtures.At the same time,a set of copy system of shear lateral trajectory was designed in this paper,through the data and analysis of the trajectory,the region of the interface layer and the deformation in shear direction V_h in the shear of the interface between different soil-rock mixtures and structures is obtained.The geometrical characteristics of the interface layer of different Soil-Rock Mixtures are analyzed.According to the analysis of the test results,the following results have been achieved:(1)With the increase of normal stress,the hardening characteristics of the shear stress-shear displacement curve of specimens show an increasing trend;the shear strength shows an increasing trend;the rigidity of specimens shows an increasing trend;the vertical displacement of specimens first decreases,reaching a equilibrium inflection point and then increases,and the normal stress corresponding to the equilibrium inflection point presents a trend with the increase of stone content.The best shear deformation resistance can be obtained by reducing the stone content of the Soil-Rock Mixture filler and stressing the integration of normal stress at the contact surface.(2)With the increase of stone content of Soil-Rock Mixture,the best shear strength is obtained when the stone content is about 50%;the vertical displacement decreases first and then increases,and the best shear deformation resistance is obtained when the stone content is about 60%;the rigidity of the sample increases first,then decreases,and then remains flat;the internal friction angle and cohesion of the specimens show two opposite trends,and the shear strength of the interface between the soil-rock mixture and the structure is dominated by the internal friction angle under the high normal stress of 1.4~2.0MPa.(3)With the increase of moisture content in soil-rock mixture,the hardening characteristics of the shear stress-shear displacement curve of the sample show the trend of weakening first and then strengthening,and the strain softening trend occurs when the water content is 10%;the shear strength shows a decreasing trend;the vertical displacement shows a decreasing trend;the rigidity of the sample shows a decreasing trend;the internal friction angle of the soil-rock mixture sample shows a decreasing trend,and the cohesion of the sample increases first and then decreases.Considering the situation of the project site and comparing with the optimum moisture content in the construction,the appropriate moisture content of each layer of filler can be obtained.(4)In this paper,the method of interface layer exploration in shear test,which is composed of lateral shear trace copying system,can reflect the scope and regularity of interface layer,and it is a simple and economical method of interface layer exploration.When the shear occurs at the interface between the filler and the original ground,the thickness of the interface layer satisfies the rule that increases with the increase of stone content and the decrease of water content.The soil near the contact surface can be treated in different ways according to the existing engineering experience and specific engineering conditions.