During excavation in deep foundation pit, the deformation of soil and earth surface caused by engineering dewatering is an important factor to affect engineering safety. In this paper, according to the data provided by the detailed survey report of route I subway in Shenyang, the subsidence laws of the ground and around buildings caused by the dewatering of route I subway were analyzed by using Coupling System of Flow & Solid in Rock Failure Process Analysis (abbreviated as RFPA) which is based on poroelasticity theory and consolidation theory, developed by CRISR, Northeastern University, and preliminary results were obtained.
The Shenyang route 1 metro is altogether 22.048 km long with 18 stations. Considering the depth and the area of the foundation are very big as well as the long Period and big amount of the dewatering work, the subsidence of the earth surface caused by the dewatering during the construction is an important problem during the construction. The level of the groundwater is Very high in Shenyang, and the aquifer is mainly sandy gravels whose permeability coefficient and the radius of influence caused by dewatering are big. Whether the dewatering will cause uneven settlement thus to bring big influence on the buildings around is an urgent problem must to be solved in time.
In this paper, the subsidence laws of the ground Surface and the buildings adjacent in Qingnian Street caused by dewatering are analyzed.
According to the reconnaissance report, the stratum from top to bottom are miscellaneous fill of 2~3m thick, sandy gravel of5 m thick with 3~5 m fine gravels, 4~5 m sandy gravels and fine gravels below. There is lack of clay and the whole stratum is composed of medium and coarse sand, gravels and pebbles.
The groundwater belongs to the phreatic water of Quaternary with average depth of 7.5m and permeability coefficient of 78~ 121 mid. The depth of the bottom of the aquifer is 45.0 m and the thickness of the aquifer is 39.3 m, with the radius of influence of about 157 m.
The station will be constructed by the open-cut method combined with the pipe well dewatering method. The dewatering depth is 9 m. Buildings near to the foundation pit are Electricity industry garden A of 30 stories whose pile length is 28 m and the Sanshengyuan hotel of 6 stories. The profile of the stratum is given in fig. 1 and the parameters of the foundation soil are given in table 1.
In order to find out the existing condition, cause of formation and the trend in development of the deformation caused by dewatering and to supply scientific control measures as well as reasonable monitoring project for the design and construction, the Rock Failure Process Analysis software (abbreviated as RFPA2D) developed by CRISR, Northeastern University, which is based on poroelasticity theory and consolidation theory is used.
