Study On The Genetic Model Of Ground Fissures In The Piedmont Of Shi Jiazhuangto Baoding Region

The ground fissure disaster is the most serious area in North China Plainof China.The ground fissures are the most developed in Shijiazhuang-Baoding region,which seriously threaten the plan and development of Beijing-Tianjin-Hebei Economic Circle and XiongAn new Area.The paper relies on the geological survey project of China Geological Survey."Beijing-Tianjin-Hebei Cooperative Development Zone,Shijiazhuangto Baoding Bay active structure and regional crustal stability survey" through spot investigation and detection,combined with the existing literature results,the main achievements of the parper are as follows:(1)The disaster inducing background of ground fissures in piedmont plain of Shijiazhuang to Baoding region includes external and internal dynamic geological background.Exteral daynamic geologica background includes landform,lithology,hydrogeological conditions,karst and human engineering activities.lnternal dynamic geological background includes active faults,crustal stress,earthquake.The ground fissures is mainly related tostructure and thickness of Quaternary soil layer,and the degree and mode of activefaults,andgroundwater over-exploitation.Analysed internal and external geological factors influence on formation of ground fissures.Summarized the genetic types of ground fissures.(2)Because of different genetic types of ground fissures,which have different distribution and activity.Tectonic ground fissures are mainly developed along the direction of active faults,which is characterized bydirectivity,zonation,concentration and systematicness.The distribution of non-structural ground fissures is characterized by directionality,concentration and correlation.(3)A Case Study of typical ground fissures.Study the Genetic mechanism of different genetic types ground fissures.Longyao ground fissure is a direct expression of the present creep movement of Longyao fault,cutting Quaternary rock and soil layers and extended to the surface to form a steep ridge.Caohe ground fissures are caused by groundwater over-exploitation,causing nonuniform compressed of aquifers,differential concretion subsidence of aquiclude,produced secondary tensile stress.Shunping ground fissures is causedby upward erosion of karst in basement.(4)The model of ground fissures in the piedmont plain area of Shijiazhuang to Baoding region can be divided into fault creeping model,Overexploited Horizontal Aquifer and Geological Weak Zone coupling induced model and karst collapse upward erode model.And fault creeping ground fissures include "fault direct shear model" and "buried fault model".The direct shear mode of faults is creep movement of faults.The fault plane cuts through Quaternary rock and soil layers and arrive the surface to form steep ridges.Buried fault induction mode is that the creep movement of faults does not develop to the surface,joints and fissures are formed in the shallow surface,and ground fissures are induced by external factors.And using Flac3Dfinite difference softwareto simulate and analyzethe formation and evolution of fault creepingground fissures.(5)According to the level of damage to the surface buildings in the ground fissure area.Considering the surface subsidence and buried fault activity influence.Propose the "damage" to describe the level of damage to the surface buildings.Divide different levels of damage,and combined with surface Deformation detection results,Determined the Safety distance of buildings in ground fissure region of Fault direct Shear mode.Providing a scientific basis for the prevention and warning ground fissures disasters.