Analysis On The Development Mechanism Of Ground Fissure In Baoding Area

In recent years,the ground fissure activity in the Baoding area of Hebei is becoming more and more frequent.It is of great significance for the prevention and control of the ground fissure disaster in this area to make clear the law and mechanism of the development of the ground fissure in Baoding.On the basis of previous studies,this paper analyses the distribution,development and genetic mechanism of ground fissure in the region of Baoding by the field investigation and numerical simulation.The main conclusions are as follows:1.The northwest part of Baoding is the bedrock mountain area.The outcropping strata are mainly the Archaean to Mesozoic strata and a few Cenozoic strata,while the southeast is the faulted plain area,the surface is mainly covered by the Quaternary strata,and the southeast part of the study area has strong tectonic activity since Cenozoic and several active faults developed.2.The distribution of ground fissures in Baoding area is wide,and the distribution of ground fissures is regular in space and time.The ground fissures are distributed in the sloping plain of the front of the mountain.It shows a small hole in the ground,and a few ground cracks have a strong direction of development.Most of them have a straight line or a line of folding in the plane.It is consistent with the direction and activity of the fracture.The time is concentrated in the rainy season of 6-8 months a year and is clustered in some areas.3.Field investigation and exploration and drilling engineering reveal that the ground fissure in Baoding area is generated by the coupling of internal and external forces.The internal force comes from the tectonic stress field caused by the extension of the Baoding regional crust,and the external dynamic factors are the overexploitation of groundwater and the sudden ground heavy rainfall,and the internal dynamic action is the fundamental factor of the development of the ground fissure,and the external dynamic action is the inducing factor of the development of the ground fissure.4.The results of numerical simulation show that:1)in regional tectonic activities,there is a strike slip fault in the two disks of fracture,and there is obvious stress and strain concentration in the fracture turning point,end point and fracture intersection point.The surface of the corresponding area is often deformed and destroyed relatively seriously,and it is also a more dangerous area for the development of the ground fissure.2)under the action of tectonic activity,there is obvious dislocation and stress and strain concentration in the two disks of the fracture,which leads to the deformation of the overlying soil in the fracture,and in some places it has reached the surface and then developed into the ground crack.In addition,due to the continuous change of fracture activity and stress field,the distribution of stress and strain field in shallow surface is complex,and there are secondary stress and strain concentrated zones in some parts,which all provide favorable conditions for the birth and occurrence of ground cracks.