News Abstract: the internal reason of surrounding stratum deformation caused by pipe jacking construction is that the soil in natural static equilibrium state is damaged, which leads to the change of stress state. This part of soil undergoes complex stress paths, such as extrusion, shear and twist.
The internal reason of surrounding stratum deformation caused by pipe jacking construction is that the soil in natural static equilibrium state is destroyed, which leads to the change of stress state. This part of soil undergoes complex stress paths, such as extrusion, shear and twist. Because the advance of pipe jacking machine and pipeline depends on the thrust of Jack, only when the jack has enough strength to overcome various resistance encountered in the process of advancing, can the pipe be continuously pushed forward, and the resistance reacts on the soil. From the mechanical point of view, the construction process of the top pipe is a continuous extension process of a column hole parallel to the semi infinite interface in the three-dimensional semi infinite medium. There are two deformation zones on the outside of the column hole. The inner deformation zone is plastic deformation, and the outer deformation zone is elastic deformation. During pipe jacking, the first micro shrinkage (building gap) and then micro expansion (grouting behind the wall) are manifested as the squeezing and loosening of soil by the pipe jacking machine, loading and unloading, the variation of soil properties caused by the rise and fall of pore water pressure, and the surface uplift and subsidence. Thus, the stress release, volume, water content or pore water pressure change, especially the destruction and change of soil structure or fabric. Especially in the jacking construction in soft clay, a little disturbance of soil will make its mechanical parameters change greatly, and cause consolidation and secondary consolidation settlement for a long time. Website: www.dsfsdl.com www.dtdlfs.com micheledimaio.com www.dtgk88.com