Abstract:In land sections of Xiang¢an subsea tunnel in Xiamen with unfavorable geological condition,where large-section shallow-buried excavation method is adopted,the vault subsidence of some sections exceeds allowable value obviously. As the measured data in field show that the integral subsidence(including both during excavation of headings and after closure of primary lining) is an important factor leading to vault subsidence. Countermeasures including setting locking anchor pipes and grouting in inverted arch have been taken in field to control the settlement. In order to investigate the effect of different countermeasures,firstly,a numerical simulation is carried out based on physico-mechanical parameters of surrounding rock and lining structure provided by both design documentation and field test. And then a general analysis is carried out based on the numerical simulation and measured data in field. Results indicate that,after setting locking anchor pipes,vault subsidence can be reduced about 17 percent,and horizontal convergence 12 percent nearly;after grouting in inverted arch,vault subsidence can be reduced about 18 percent;both two countermeasures can reduce plastic area in surrounding rock and increase structure safety to a certain extent.