Analysis On The Formation Mechanism Of Ground Fissure In Dacheng And Wen'an Country Of Hebei Province

Dacheng county and wen'an county are located in the east of Hebei plain,which is the transition region of Jizhong depression and Cangxian uplift.Since the quaternary period,the neotectonic movement has been violent.And human engineering activities in the region(such as groundwater over exploitation etc.)are so frequent to lead to the ground fissure of the region development,and bring serious impacts and trouble for the local people in recent years.Therefore,it is of great significance to find out the cause and development mechanism of fissure for disaster prevention and control of ground fissures in the region.Based on the previous research and the field survey and indoor numerical simulation,this paper analyzes the distribution,development characteristics and causes of the ground fissure in the research area and draws the following conclusions.1 There is close relationship between the occurrence of fissures and tectonic activity in Wen'an county.The fissures in wen'an are distributed along the Cangxi faults,and the dominant trend is consistent with the faults.The mechanical pattern of ground fissure on the surface is single and has obvious structural characteristics.2 The Dachen fissure is the result of tectonic activity and human engineering activities,of which human overexploitation of groundwater has triggered and accelerated the occurrence of ground fissures.The fissure scale is relatively small in Dacheng county,and there is less exposed to the surface.And its occurrence are closely related to hydrodynamic factors.Dacheng county is located in the radiation range of Cangzhou subsidence funnel,therefore differential settlement on the ground plays a very important role in the development of fissures in the Dacheng country.3 According to the fracture plane form and the structure of profile,The breeding environment of the ground fissure in the research area is mainly controlled by the tectonic stress environment of the region,and is gradually widened and deepened under the joint action of the internal and external forces.4 The numerical simulation results show that:1)The extrusion of the north China block near EW and the stretching action of near SN provide the dynamic conditions for the occurrence of fissures.The fracture of the research area is mainly based on the sliding motion and the tensile-shear stress field is formed in the zone.The stress and strain concentration at the end point,inflection point and intersection point of the fracture provide the power source for the occurrence of fissure.2)NE or NNE to fracture under the compressive stress of near EW,the tensile shear movement occurred,controlling the formation of NE to crack in the region.3)In the numerical simulation,the main stress path of the region is consistent with the direction of the ground fissures in wen'an county,and it can be concluded that the cracks in wen'an county are mainly controlled by the Cangxi faults.Dacheng county is located in the Dacheng uplift,and regional stability is better,but still affected by the tensile stress environment,Cause of the ground fissures within the county is still mainly tectonic factor,cangzhou subsidence funnel has triggered the occurrence of Dachen ground fissures.