Study On Soil-structure Interaction Of The Concrete Jacking Pipe In Sand Strata

The pipe jacking process pushingwill inevitably disturb the soil around the pipeline,which will be influenced by many factors,such as the loading and unloading process caused by the changing contact stress between soil and structure and the deformation of soil.The complex interaction between soil and sturcute increases the difficultyin controlling the jacking force and the deformation of soil.The past engineering experiences in sandy strata of jacking large concrete pipe are quite few.For this reason,this paper was aimed for clearfying the soil structure interaction during the jacking process.Firstly,the friction parameters were analyzed through laboratory tests a and the controlling parameters of thixotropic mud were optimized;then combined with field monitoring data and site parameters from geological prospecting analysis,the equivalent field paramaters were figured out;based on this,using the ABAQUS finite element analysis software,the anti-jacking force of work well as well as the soil-sturcture interaction were analyzed.The optimized proporation of the thixotropic mud got from laboratory test are:Bentonite:CMC:Soda ash:Water =1:0.0136:0.06:5.5.The friction coefficient of concrete pipe in the sand-thixotropic mixture is 0.26.Numerical results showed that when the pipe jacking counterforce is over 45000kN,the soil around the working well came to its limited state.If load increased,sliding surfaces appeared with an oval shaped damage area in the ground surface.It can be found that the jacking frictional resistance per unit area is 39-44.2 kN after thixotropic mud was pumped into the sandy soil layer;Meanwhile,if the overburden thickness exceeded 12 m;the arching effect can be formed;The mechanism and the failure form of the excavation face are related to the pressure and the thickness of the overburden;Pipe support pressure control can guarantee the stability of excavation face by 1.1?1.2 times of the static soil pressure.