Theoretical Study On Properties Of Soil And Structure During Pipe Jacking Construction

Utilizing and empowering underground space was more and more emphasized during the development of urbanization in China. As a unexcavtion technology, pipe jacking had a unique excellence. Pipelines could be laid completely without digging the ground surface. Thus, it had been used widely in civil engineering. At the same time, pipe jacking construction would induce soil movement and additional soil stress inevitably. When ground displacement was big enough, the construction or buried pipelines around the pipe would be damaged.The interaction between soil and pipe, soil deformation, and the calculation for earth counterforce in working well during pipe jacking construction were investigated in this dissertation. The major works and results of this dissertation were as follows:(1) The shape of sliding block and upside of sliding block were presumed as a trapezoid wedge and a trapezoid prism respectively when the tunnel face was collapse. Using the theory of Terzaghi's relation soil pressure, the minimal support pressure formula with tunnel face in stratified sandy soil was obtained based on the principle of sliding block entire force balance. It was shown in analytical calculation that, the calculation result by the method mentioned above was smaller when compared with that by wedge stability model, and also more closer to the results of centrifugal-model test.(2) Vertical and annular reinforcing steel bar stress and pipe-soil contact pressure during pipe jacking were monitored on the spot. Field data were analyzed. It showed that axis force and pipe-soil contact pressure increased along with pipe jacking at the very start, and it maintained stated basically when jacking to a certain distance. When inner side reinforcing steel bar of tip and bottom pipe were pulled, outer side were pressed. And both sides of pipe were just contrary. Annular reinforcing steel bar bears very little but with great alteration. Contact pressure of tip pipe was greatly affected by grouting. The pressure decreased obviously after grouting. Contact pressures of both sides were affected less.(3) It analyzed the reciprocal action between pipes and soil during long-distance linear pipe jacking. Rotational moment was considered to arise when pipeline was diagonally loaded. Soil breakage took place to produce the whole stability failure of pipeline when the maximal soil counterforce of tail pipeline exceeded its bearing capacity. It analyzed the interaction between pipe and soil during the traditional curved pipe jacking. Circular earth pressure was calculated by adopting the displacement-considered calculation of earth pressure. The maximal earth counterforce formulae for the heading and the latter pipelines were deduced. Finally, several control methods to avoid the stability failure of pipeline during long-distancelinear and curved pipe jacking were advanced.(4) The influence of internal friction angle