Research Of Simulation Testing Of Subway Tunnel Crossing Over Ground Fissures In Xi'an

Subway construction in Xi'an is in the face of 13 ground fissures. There is no precedent of the subway constructing in this kind of site in the history of subway construction at home and abroad, even no codes can be followed. It will bring availability purport to subway construction and subway safe operation in Xi'an if the ground fissure of function mechanism to the tunnel structure and failure mode of tunnel structure are known with certainty.Two physics model experiments of subway structure crossing over the ground fissure are carried on to study the force exerting mode of subway structure and pressure changing form of rock soil mass around subway structure when the ground fissure is active by using the self-built experimental platform. The tunnel structure form is respectively integral tunnel structure and segmenting tunnel structure. The influence scope of ground fissure activity to integral tunnel structure crossing over it mainly locates in vicinity of bilateral ground fissure according to experiment result. The activity has most influence on the footwall structure nearby ground fissure. The top of structure is subjected to tension while the bottom is compressed in vicinity of ground fissure. The influence scope of ground fissure activity to segmenting tunnel structure crossing over it also mainly locates in vicinity of ground fissure.But it is different from integral tunnel structure. The structure in hanging wall soil is strongly subjected to squeezing function. It has larger displacement and smaller internal force. The integral tunnel structure crossing over the ground fissure will prevent rock soil mass at certain scope of top structure from moving downward. Descending soil at both sides of structure will has downward dragging effect on the soil at top of structure which will greatly increase the vertical pressure of surrounding rock at top of structure. While the lining of segmenting model has little influence on the pressure of surrounding rock. The hanging wall of ground fissure occurs integral settlement with the settlement of hanging wall of soil and will not produce hindering effect on the surrounding rock when ground fissure is in activity.The numerical simulation is carried on to the integral model by using finite element software, The change law of displacement, stress and strain etc has consistency when the testing result is compared with the numerical simulation result.