Study On Mechanical Behaviour Of Tunneling Through A Box Retaining Wall In Chongqing Nanping Exhibition Center

With the development of city construction, the scale of city becomes larger and larger, tunnel planning and designing becomes more and more difficult, especially in mountain cities, tunnel cross through existing buildings and structures becomes inevitable, and increases with the time. The corresponding problems embrace:①Weak backfill construction problem.②Shallow covered tunneling problem.③The influence of tunnel construction on surrounding existing buildings and structures.④The problem of surface settlement. Then under the condition of complex urban areas, how to design tunnel to enable the influence on surrounding buildings and structures reduce to minimum, to ensure that there's no collapse, deformation and settlement become controllable, blasting disturbance becomes small, have become a research keystone of urban tunnel construction, and researches home and abroad become more and more. However, there's a lack of research on structure stabilization measurements and tunneling construction Optimization when tunneling through existing buildings and structures. The research about the removal of structures and pile foundations that beyond limit does not exist. So taking the Nanping central transport hub under ground cut tunnel as background, this paper develops around reinforcement of the boxed retaining wall, and gives out conclusions for similar project..According to the field site of Nanping central transport, this paper has discussed problems about tunneling cross through boxed retaining wall, which include crack, tilt and sink of the wall, slip and collapse of the backfill, unsymmetrical-pressure tunnel, and the influence of explosive vibration, drainage systems for underground water, surface waste water, and rainfall. Measurements have been made in respond to the problems, such as backfill counter-pressure on the back, measurements to reduce vibration, drainage system, grouting to stop water, surface drainage. In order to research the feasibility and necessity of the measurements, this paper has performed case analysis by means of 3-D FEM, assessed the advant age and disadvantage of each case, and screened out the best case. And then, By means of monitoring measurement, this article has verified the reliability of FEM analysis, and analyzed the difference born between FEM and monitoring measurements.In research of tunneling cross through boxed retaining wall, conclusions has been drawn as follows:①The reinforcement of retaining wall could reduce the influence of tunneling engineering on the wall stability. The reinforce measurements include:1) grouting to the box in order to increase the wall gravity;2) backfill on the back of the wall to keep mechanical balance.②Advance length management could limit the influence of tunneling on the wall;③Remove the pile foundation by two steps could reduce the mechanical influence of pile removal on the wall stability;④By comparing the results of FEM and monitoring measurement, this paper has demonstrated the correctness of FEM results;...