Study on the Influence of Over Diameter Ratio on Pipe Jacking Construction Behavior in Soil-rock Composite Stratum

In the soil-rock composite stratum, the control of the jacking force value of the pipe jacking construction is directly related to the engineering safety and cost, and the over diameter ratio is regarded as the key geometric parameter affecting the jacking force. At present, there is still a lack of systematic research on the drag reduction mechanism of this parameter in soil-rock composite stratum and its quantitative influence on stratum deformation. Based on the background of the relocation of the main drainage pipe to the pipe jacking project of Chongqing Hengda Rail Times Project, this paper uses ABAQUS numerical simulation method to systematically analyze the whole jacking process under different over diameter ratio. Through parameter sensitivity analysis, the time history curve of stratum displacement field and jacking force is extracted. The results show that in the process of pipe jacking, the most obvious position of pipeline disturbance to soil is near the starting end of pipe jacking. With the increase of the over diameter ratio, the maximum deformation of the soil increases obviously, and the disturbance of the pipe jacking construction to the surrounding soil becomes more and more obvious. In addition, the jacking force increases nonlinearly with the increase of jacking distance. The larger the over diameter ratio is, the smaller the jacking force value is. The increase of the over diameter ratio has a significant drag reduction effect on the jacking force value of the jacking pipe. When the over diameter ratio is less than 1.13%, the influence on the jacking force value of the jacking pipe is the most significant, and the variation range of the jacking force value is also the largest. The research results provide a quantitative basis for the prediction and construction optimization of similar strata.