In coastal area, there are many muddy soil layers with high compressibility, rheology and thixotropy bad engineering geological properties. Therefore, the deep silt soil deep excavation is facing high risk construction and has significant effects on the surrounding environment. In order to further clarify the deep silt soil mechanical excavation of significant effect, based on a deep foundation pit project, through the finite element three-dimensional numerical simulation, the influences of silt soil deep excavation on nearby architectural structures are revealed. The results show that: the existence of deep silt soil makes the horizontal influence area of the foundation pit excavation increase obviously, while the vertical influence area is less affected. In the horizontal distance of 150 m and the depth of 85 m, the soil and structures are all affected by the foundation pit excavation. Foundation pit and outline in concave and convex, architectural structures, discover stress concentration. Therefore, in the land of silt soil layer depth, wall and both the horizontal displacement of tunnel wall panel with obvious mutation; both the horizontal displacement and settlement curve tunnel is the characteristics of the "large in the middle and small at both ends". The deformation of the bridge increases with the increase of the excavation depth and the horizontal displacement of the bridge piles in the silt soil depth increases obviously with the maximum horizontal displacement of 5.33 mm and maximum subsidence of 9.92 mm.

Southwest mountainous area is an important energy base in China. There are a large number of mining engineering, which is one of the important inducements of many landslide disasters. Under the action of mining, the development of mountain fracture zone controls the stability of mountain. The development height of the fracture zone was quantitatively calculated by a simple beam model based on key layer theory, and the results were verified by UDEC numerical simulation. The results show that under the influence of coal mining, the overburden loses its support and flexure deformation occurs. The cracks on roadway top gradually expand to the surface. The cracks have the characteristics of large scale and difficult to heal, and they finally form a permanent fracture zone. Considering the location of the cut hole, the nature of the rock stratum, the mining range and other factors, the subsidence value of the mountain rock stratum under the mining action is quantified, and a theoretical formula is proposed to effectively predict the height of the fracture zone. Based on UDEC numerical simulation test, the prediction of fracture zone height is verified. The result is close to the theoretical calculation result, and the maximum error is 7%. It is feasible to use the model to predict the overestimation of fracture zone.