Research On Static And Dynamic Shear Characteristics Of The Interface Of Sulphate Saline Soil And Concrete

Road construction is seriously affected by the special properties of saline soil such as salt expandability,collapsibility and corrosivity.Concrete is the most commonly used structure in road construction.In recent years,more and more road construction is carried out in the saline soil area.The research on the shear characteristics of the interface between saline soil and concrete has been paid more attention.In this paper,indoor large-scale direct shear test combined with numerical simulation and scanning electron microscope technology were adopted.The effects of salt content,temperature and other factors on the static and dynamic shear characteristics of saline soil concrete interface were studied.The main contents are as follows:(1)A series of monotonic direct shear tests of were carried out on the interface of saline soil and concrete under the conditions of 5 salt contents,3 initial dry densities and 4 normal stresses.The variation laws of interfacial strength characteristics and volume deformation characteristics were analyzed.The results show that the deterioration of interfacial shear strength is caused by salt content.The enhancement effect of the initial dry density on the interfacial shear strength is inhibited by saline soil.Under the condition of lower normal stress and higher salt content,dilatancy is appeared in the interface,and shear shrinkage is shown in other cases.(2)Five kinds of saline soil and concrete were tested for 1,3,6 and 10 freeze-thaw cycles at ±20℃,respectively.After the cycle,the monotonic direct shear and scanning electron microscope tests were carried out on the interface.The variation law of the interfacial shear characteristics and soil pore distribution under different freeze-thaw cycles was analyzed.At the same time,based on FLAC3 D software,the effect of temperature on the interaction between saline soil and concrete was studied.The results show that the shear strength of saline soil concrete interface is reduced by freeze-thaw cycle.The scanning electron microscope tests found that the interfacial soil porosity was increased under the action of freeze-thaw cycles.The numerical simulation results obtain that the average shaft friction resistance of the interface is increased significantly as the temperature increases,which will be promoted when the salt content is higher.(3)Using large-scale indoor dynamic direct shear equipment,the monotonic direct shear,cyclic direct shear and post cyclic monotonic direct shear tests were carried out on the interface between saline soil and concrete.The effects of 5 salt contents,3 shear frequencies,3 shear displacement amplitudes on interface strength and deformation characteristics were studied.The results show that the peak shear stress of the interface is affected by the salt content,and the variation effect of the shear stress with the number of cyclic shear is restrained.The interfacial shear stress is increased under the cyclic loading with larger displacement amplitude and higher shear frequency.Compared with that before cyclic loading,the shear strength of the interface after cyclic loading is improved.