Experimental Study On The Friction And Distribution Characteristics Of The Side Wall Of The Super Deep And Large Sinking

The value and distribution of the side wall friction during the sinking process is one of the key factors affecting the sinking of the sinking well.At present,the analysis of the frictional resistance of the sidewall of the caisson is mostly based on the field test,and the indoor test for the frictional resistance of the sidewall of the sinking well is still carried out less,and the test results are obtained under the condition of 1 g gravity field.In order to better study the characteristics of the frictional resistance of the side wall of the sinking well,this paper relies on the research project of the scientific research and development plan of the China Railway Corporation,“Research on the interaction performance between the deep-water large-section caisson and the subsoil”,to build the 29# pier of the Shanghai-Shanghai Yangtze River Bridge.The foundation of the well is the research object,and the on-site and indoor centrifugal model tests are carried out.The main conclusions are as follows:(1)The field test results show that when the depth of the soil is 47 m,the effective earth pressure of the side wall of the caisson is between the static earth pressure and the passive earth pressure;when the vertical state sinking mud sinks,the side wall of the sinking well is near the edge The pressure relaxation zone appears,so that the effective earth pressure of the side wall of the sinking well is small and large,and the middle is large;the arrangement of the steps is beneficial to reduce the effective earth pressure of the side wall of the sinking well.(2)In the centrifugal test,the effective earth pressure of the side wall of the straight wall and the stepped caisson is between the static earth pressure and the passive earth pressure..(3)In the centrifugal test,the frictional resistance of the sidewall of the straight-walled caisson is generally small and large,and the middle is large.When the sinking depth is small,the frictional resistance of the sidewall of the sinking well is basically linear with the depth of the intrusion.As the sinking depth increases further,the frictional resistance of the sidewall increases first and then decreases.Within a certain depth of sinking,the extreme value of the frictional resistance corresponding to different depths increases with the increase of the sinking depth,and the occurring part gradually moves down.(4)In the centrifugal test,above the steps,the value of the frictional resistance of the stepped caisson sidewall is about 0.5 times that of the straight wall.The reason is that due to the existence of the step,the sidewall of the caisson and the soil around the sinking well create pores,so that the sidewall of the caisson There is a certain relaxation in the position soil,which also shows that the step has a significant effect on reducing the frictional resistance of the sidewall of the sinking well;near the step position,the frictional resistance of the stepped sidewall has a large increase,and it is below the step to the edge of the blade.The value is close to the straight-walled caisson,indicating that the influence of the step on the step below the step is gradually reduced,and the influence is negligible in a certain area above the blade foot.(5)According to the centrifugal and field test,the calculation formula and model of the sidewall friction of the straight wall and stepped caisson are proposed,which will provide reference for similar projects in the future.