A study of the cracking mechanism of ground fissures under the action of active faults

There is continuing controversy about the genesis mechanism of ground fissures. The authors believe that the linkage mechanism between active faults and Holocene shallow surface fissures is one of the main reasons. The typical ground fissures in the North China Plain are examined, and detailed ground investigation, data analysis and summary are carried out, combined with geophysical survey, trench exploration and drilling and other technical methods. The results show that (1) according to the characteristics of surface morphology, ground fissures in the North China Plain can be divided into two types: Holocene jointed fissures and Holocene active fault fissures. (2) The external condition of joint-fissure type of ground fissure cracking is the decrease in groundwater level in the North China Plain, and the dried loose aquifer is the storage place of surface water after seeping down along joint fissures, which is the cause of seepage pressure, while the active fault is the internal factor of producing ground fissures, both of which are indispensable. Active fault type of ground fissures are essentially Holocene active faults. (3) The main characteristics of the jointed fissure type of ground fissures are local surface subsidence, discontinuity, no-difference in surface height, etc. The main characteristics of the active fault type ground fissures are strong continuity, obvious surface fault distance, which is the main distinguished feature between the two types of ground fissures. (4) The linkage mechanism between tectonic active faults and Cenozoic shallow surface fissures is studied for the first time in this paper. The clue elaborates the specific role of tectonic active faults in the formation of ground fissures, clarifies the “role” of groundwater level decline, and provides geological basis and suggestions for urban planning and construction.