Estimation Of Jacking Force During Jacking Pipes In Shenyang Sandy Stratum

Jacking force is the key parameter in pipe jacking engineering.It affects jacking shaft layout,immediate station layout,choosing jacking kinds and jacking bearing design.Calculating jacking force reasonably is an important issue before process the whole pipe jacking engineering.Concerning the issue,macro and micro physical and mechanical properties for of Shenyang sandy soil,face support pressure for jacking pipe,frictional resistance for jacking pipe and jacking force transmission mechanism were studied respectively.Based on these research results,the new model for estimation of jacking force during jacking pipes in Shenyang sandy stratum was built.Shenayng sandy soil was taken as the research object,moisture contents,and densities,proportions of solid particles and triaxial compression test and plate load test were performed.The physical and mechanics parameters for sandy soil were tested.The friction coefficients between soil and pipe were measured using modified direct shear apparatus.Slio plus sliding wedge model were studied by independent two parts:wedge part and its upper octagonal.Theory of calculating crown vertical soil pressure was modified basing on modified Promojiyfakonov theory and Terzaghi theory.After comparison with monitored data,it can be concluded that this modified theory is more suitable for calculate vertical stress of pipe crown in sandy soil with large buried depth.The earth pressure on the pipe jacking face can be calculated using a new method proposed in this part.The 3D arching effect in loosening soil and modified wedge shape can be taken into account in this method.The result of the proposed method agree well with these models reported in other literatures.Under consideration of wood joint and hydraulics joint,the jacking force transmission mechanism of axis compression and eccentric compression between pipes were studied.Function fk presented the effect of jacking deviation on jacking force was built,and effect of pipe joint angle and maximum deviation angle on jacking force were studied.A new model for investigating the 2D porosity of gradation particles was processed.A series of simulation tests for investigating the effect of different parameters on Macro Properties in PFC2D Biaxial Tests were processed.The model to investigate frictional force between soil and pipe was built using PFC2D,and the optimized modeling method was presented in this part.Then the new method to estimate jacking force during jacking pipes in Shenyang sandy stratum is provided,four pipe jacking engineering cases as engineering projects to analyze the jacking force using this method.The result of the proposed method agree well with field monitoring data.