Reciprocating Shear Behavior And Strength Weakening Mechanism Of Steel-Soil Interface In Rock-socketed Filling Pile With Steel Tube

There are many high mountains and deep valleys in the upper reaches of the Changjiang River with rapid flows,large variation of water level and the characteristics of complicated geological conditions.In order to solve those engineering difficulties,the rock-socketed filling pile with steel tube as wharf structure of mountain river that is a new foundation form was widely used.It's different from the contact problem of traditional pile foundation and soil around pile.The contact surface of rock-socketed filling pile with steel tubeis and back fill course is steel-soil contact interface.Under the influence of long term cyclic load,such as ship impact load,mooring force,wave load and so on.There are will be reciprocating shear between the rock-socketed filling pile with steel tube and steelsoil contact interface,thus affecting on the normal work and even security and stability.Therefore,this paper used widely distributed study on reciprocating shear properties of steel-soil contact interface and got some results:(1)Improved huge systerm of reciprocating shear system.On the basis of the original instrument,the system of reciprocating shear and steel-soil contact interface is improved.Shear system includes the main part,power system and the system of date acquisition and control.Repeating the test with improved system,results show that the repeatability test less impact on the results of test system,and provide a reliable hardware support to reciprocate shear test.(2)The effects of initial normal stress,interface roughness and sample moisture content on the reciprocating shear properties of steel-soil interface are revealed.Based on the improved test system,the shear stress-strain relationship,normal stress,normal displacement and interfacial shear strength of the specimens were studied.Compared with the shear strength of the interface under constant stiffness condition and the constant stress condition,the degree of weakening under the constant stress condition is far less than the constant stiffness condition.(3)The variation law of particle crushing in the reciprocating shear test of steel-soil interface was analyzed statistically.The particle size of each particle size was calculated by the screening test.The results showed that the particles had different degree of particle crushing.The relationship between the breaking rate of the sample and the initial normal stress is linearly distributed;the relationship with the interface roughness is parabolic distribution;the logarithmic function distribution is the relationship with the reciprocating shear number.Comparing the regularity of particle breaking rate under constant condition and constant stress,it is found that the two kinds of boundary conditions have the same variation rule,and the constant stress condition is always larger than the normal stiffness condition.