Characteristics And Mechanism Of Land Subsidence In Hebei Plain

As Land subsidence commonly prevailing worldwide,especially in those areas where Industrialization and Urbanization level are really high,it is now becoming one of the most important environmental geological problems and city geological disasters that could influce development of economic society.Although with modern economy,dense populatioion and high Urbanization level,Hebei plain owes overall low and flat terrain,and serious land subsidence occurring in it causes great economic losses and damages and deep effects on regional economic development,environmental protection,taffic and flood control,people's life,and industrial production and urban construction.Characterisitics,mechanism and influenced factors of land subsidence in Hebei plain are systematically analyzed in this thesis according to the forming process and development of Hebei plain.Several aspects including the relationship between compressible soil and its consolidation status soul structure and clay mineral components of land subsidence center with land subsidence,layered-soil mechanics tests,step bench mark monitoring,groundwater monitoring and simulation of groundwater exploitation-land subsidence model,have been studied.Also the motive development of land subsidence from 2008~2010 in Hebei plain has been monitored by application of the InSAR technology.In accordance with the results of above researches as well as with history,nature and development trend of land subsidence,present exploitation situation of groundwater resource,thickness of Quaternary formation,ratio of clay minerals in main mining strata,hydrogeological texture and basement structure in Hebei Plain,easily land-subsidece-prone area are evalued through Analytic hierarchy process to be high,moderate and low land subsidence-prone areas.On the base of the land-subsidece-prone areas,population density,society economic conditions and prevention capability,land subsidence controlling area in Hebei plain are partioned into key,secondary key and common prevention regions.More research breakthroughs and innovations of this Doctoral thesis than fore-researches include such aspects that structure of strata in Hebei plain are sysmaticaly analyzed by microtextur,genesis of land subsidence and major facters influecing land subsidence are reseached through soil mechanics tests with a tiered observed result in recent years.It is concluded that land subsidence exists everywhere the step bench mark borehole have been drilled in Hebei plain,rates of land subsidence transfer from big to small as the depth of strata,and the main fators influencing land subsidence in Hebei plain are extraction volume of groudwater,compressability of strata texture and ratios of clay mineral in compressable soil.