Based On Unsaturated Seepage Mechanism Of Groundwater Buoyancy

With the development of economy， more and more development and utilizationof city underground space， safety problems of underground structure is emerging.The groundwater occurrence state and its variation， especially the influence ofgroundwater on underground structure bottom uplift force and lateral pressure ofunderground structure is particularly strong. Due to buried depth of the undergroundstructure is different and in which these structure might encounter different situationsof the underground water， so it has become a research hotspot in geotechnicalengineering anti-floating design of underground structure in the city. When carryingon the anti-floating design of underground structures， the key is to determine thebuoyancy load on the underground structure. If buoyancy load determination is notaccurate， it may causes the waste of financial resources because of overestimation orsafety hazards because of underestimation. Therefore， study on the mechanism ofaction of buoyancy for underground structure has important engineering significance.This paper based on one Anti-Float the fortified water level consulting projects inBeijing，through research，the original test and numerical calculations，engineeringsite in different situations pore water pressure distribution were analyzed， and on thisbasis a theoretical discussion. The main research results are as follows:1. Analyzed and summarized hydrology Geology and HydrogeologyCharacteristics of the urban area of Beijing， summed up the regional groundwaterrecharge， discharge and Runoff Characteristics， and summed up the the Beijingtypical basement buried model based on the actual engineering.2. Relying on the actual works long-term observed groundwater level and porewater pressure on the building and summarized the regularity of site groundwaterdynamic variation of pore water pressure distribution.3.Baced on variably saturated seepage physical field in the Comsol Multihpysicsfinite element analysis software， analyzed distribution of pore water pressure of thedifferent conditions for seepage， and analyzed the actual project current situation， as well as the adverse conditions that may be encountered in the future， optimizedagainst float the design.4. On the basis of the foregoing studies，combined with groundwater dynamics，the microstructure characteristics of the soil， soil bound water migrationcharacteristics of unsaturated soil mechanics of groundwater buoyancy mechanismwas investigated.