Based on the summary of the status of land subsidence research, Biot Consolidation Theory is proposed to analyze the coupling of seepage field caused by precipitation. By use of Biot consolidation two-dimensional plane finite element calculation programmed, the land subsidence of the WenZhou Yongqiang plain caused by the exploitation of underground water was analyzed. The results are more in line with the measured data, so the method for analysis of possible land subsidence is practicable.

Taking the draw water tunnel of the Jiulong river across railway in Fujian province as the research object,the influence of the subgrade settlement of Yingtan-Xiamen double railway and Xiamen-Shenzhen high-speed railway as a result of the double draw water tunnel excavation is analyzed by FLAC3D. Through numerical simulation the condition of whether the subgrade is reinforcement and whether have train load on the subgrade, the result of subgrade settlement in both single tunnel perforation and double tunnel perforation is derived. It shows that: the position of maximum settlement is just above the tunnel centerline, the proportion of subgrade settlement caused by the right line excavation is 67.5% and the one caused by the left line excavation is 32.5% when subgrade is unreinforced and there is no train load; the proportion of subgrade settlement caused by the right line excavation is 60% and the one caused by the left line excavation is 40% when subgrade is reinforced but there is no train load. The proportion of subgrade settlement caused by the right line excavation is 63% and the one caused by the left line excavation is 37% when subgrade is reinforced and there is train load. The results fit well with monitoring data and can be used as a reference for similar engineering projects. Currently, with the rapid development of China's economic, the situation of other engineering projects crossing the existing railway line has been increasing. Most researchers is carried out through the way of on-site monitoring to analyze deformation of ground surface and the railway embankment, and then comes up with the safety assessment and displacement control measures of the tunnel construction[. The common methods of ground surface deformation analysis and prediction contain empirical formula, model test and numerical simulation[. There are a lot of numerical simulation achievements for new construction crossing the existing railway[3-, which mainly focused on the embankment settlement for single or multiple tunnel beneath a single railway line. Based on previous studies, this paper analyzes the railway embankment settlement under the condition whether there is reinforced roadbed or not, and whether the two-lane tunnel crosses many railway line with a combination of train load conditions through the method of three-dimensional model, and compares with the measured data to verify the reliability of numerical simulation. 1 Engineering project and its engineering geological conditions