Research purposes: Through the establishment of simulation model based on ANSYS，the two influence laws for control of surface and arch subsidence caused by the strata disturbance due to the excavation of tunnel were researched for control of the unfavorable effects on construction safety and structure stability caused by stress redistribution of strata．The space—time sequence of tunnel excavation was optimized through the comparative analysis of simulation results with measured results and feedback design for construction of the ultra—shallow—buried and ultra—high sectional tunnel with underground excavation under the conditions of complex environment and weak—water rock．
Research conclusions: Compared with the absolute measured deformation，all calculated deformations were in the controlled ranges stipulated in the codes and standards based on the pre—measured and simulated results．Therefore，for construction of ultra—high sectional and ultra—shallow—buried tunnel under the condition of weak—water rock．the establishment of ANSYS simulation model with 100 percent of the stress release by the plane strain mode could meet the demands of the process control and optimization．For construction of the tunnel with CRD method，the simulation results showed that settlement of 2，4，5 and 7 subsections accounted for 85～90 percent of total settlement under the complex conditions．Based on this，the space—time sequence of excavation was optimized in the ways that the excavation method of the reserved cole soil was used along with the stepped CRD method．The sequence was firstly to cut through the upper step is and then to cut through the lower step．The practice has proved that this optimized method is safe and reliable．
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