The Stability Estimation Of The Karst Foundation For A Construction Site In Tangshan

With the great development of Tangshan, there plans to be an overall reconstruction project in the Changqinglou District, but the potential threats for the construction projects has been made by natural geologic hazards (e.g. the concealed karst), which constrain the further development in the region. So that the methods such as geophysical prospecting, drilling, test, numerical simulation, etc. were used to find out the Karst development situation and its distribution law, to analysis the stability of the karst foundation, and to recommend the foundation treatment methods of that area.Firstly, combining with the geophysical exploration methods, drilling and comprehensive regional geological conditions, it is determinate that across the east of the study area there is a regional fault near which many minor structures are well developed. After the northwest of the study area deformed by an overturned fold in the geological evolution, the older strata, Ordovician limestone, in which strip dissolution cracks, fracture zone, and small karst caves, most of which are filling, are well developed mainly in the 30～60m below the surface, overturned to the top while the newer, the coal measure strata of Carboniferous and Permian, went down.Secondly, according to all exploration results and experimental parameters, the conclusions which analyze with the SIGMA/W software are as follows: When the buildings within eight-storey, its impact is not more than 30m depth, if there are karst caves concealed in the range of 30～60m underlain the surface, they do not have an impact on the building above; But when the building is higher, the deeper the depth of its impact will be, even through the limestone layer, and there is the mutual influence between the concealed karst caves and the high-rise buildings.Finally, for the project proposed in the karst region of 26 high-level buildings, the numerical simulation of Karst region foundation treatment program were analyzed. Draw the following conclusions: After the treatment with 7m karst zone, the foundation strength, deformation and the stability of the karst cave roof meet the requirements. At last, end bearing pile should be adopted and playing a leading drilling of each pile, for instance, Karst foundation treatment and monitoring recommendations are given.