Experimental Study On Mechanical Properties Of Interface Between Silty Sand And Concrete Structure

In practical engineering,the interaction between soil and structure leads to structural damage and soil deformation,which seriously threatens the safety and stability of the foundation of structures.In order to ensure that the soil and structure system have a good deformation coordination mechanism,it is of guiding significance to carry out the experimental study on the mechanical properties of the soil-structure interface.In this paper,the mechanical properties of silty sandy soil,silty sand-concrete structure contact surface and frozen silty sand-concrete structure contact surface are studied by taking the contact surface of canal soil-concrete lining structure in the cold and arid region of southern Xinjiang as the research object.The mechanical properties of the interface with different media under different water content,different dry density,different normal stress and different freezing temperature were explored to reveal the mechanism of each influencing factor on the shear strength of the interface.In order to establish a foundation for the research of multi-field coupled salt-frost heave failure model of lining channels under the condition of water and salt supply in cold and arid areas.The paper mainly carries out the following research work:(1)The mechanical properties of silty sand in southern Xinjiang under different water content,different dry density and different normal stress conditions were studied by indoor direct shear test.The results show that when the dry density is small,the shear failure is plastic,and with the increase of the dry density,the shear failure changes from plastic failure to brittle failure.The shear strength of silty sand increases with the increase of dry density and normal stress,and decreases with the increase of water content.The cohesion of silty sand increases first and then decreases with the increase of dry density and water content.The internal friction Angle of silty sand increases with the increase of dry density and decreases with the increase of water content.(2)Through the silty sand and concrete interface under different moisture content,dry density,under the condition of different normal stress,the mechanical characteristics of direct shear test,the study found that:silty sand and concrete interface shear stress and shear displacement curve shape strain hardening model,interface shear failure for the plastic damage;The shear strength of the contact surface decreases with the increase of dry density,and increases first and then decreases with the increase of water content.The shear strength of the contact surface reaches the maximum near the optimal water content of silty sand,and increases continuously with the increase of normal stress.With the increase of normal stress,a shear zone of certain thickness is formed on the interface between silty sand and concrete structure,and the thickness and area of the shear zone increase with the increase of normal stress.According to the normal stress of dry density,moisture content and significant analysis of interface shear strength,get three experimental factors on silty sand and concrete interface is the primary and secondary order of the influence of shear strength:normal stress > moisture content > dry density,moisture content and the method to stress has significant effects on the shear strength of interface,dry density effect is not significant.(3)To simulate the low temperature environment canal foundation soil and concrete lining structure interface mechanical characteristics,through the frozen silty sand and concrete interface under different moisture content and different freezing temperature and normal stress under the condition of direct shear test,the mechanical characteristics of the research results show that the frozen silty sand and concrete interface shear stress and shear displacement curve is peak point,the curve is strain softening model,interface shear failure of brittle failure;The shear strength of contact surface increases significantly with the increase of water content and normal stress,and increases with the decrease of freezing temperature.With the increase of water content,the cohesion of the interface between frozen silty sand and concrete increases,and the internal friction Angle decreases.With the decrease of freezing temperature,the cohesion of the interface between frozen silty sand and concrete shows a trend of increase,and the internal friction Angle shows a trend of decrease.(4)By comparing and analyzing the characteristics of shear stress-shear displacement curves of interfaces with different media and the shear strength of interfaces,it is found that the softening phenomenon of shear stress-shear displacement curves of interfaces between frozen silty sand and concrete is more obvious than that of silty sand.Due to the differences in cohesion and internal friction Angle of contact surfaces with different media,the shear strength varies greatly with the contact surfaces with different media.The overall performance is as follows: the shear strength of the contact surface between frozen silty sand and concrete>the shear strength of silty sand and concrete>the shear strength of silty sand and concrete.