Study On The Formation Mechanism Of Ground Fissures In Weihe Basin

China is one of the countries which ground fissure hazards are most serious in the world, especially in Weihe basin the phenomenon of ground fissures are most typical and the disasters caused by ground fissures are most serious. Since recorded history, there were many ground fissures occurred in Weihe Basin. With the implementation of western development strategy, large-scale urban construction, such as Xi’an city subway, Datong to Xi’an high-speed passenger rail and other projects have been unable to avoid this particular hazard, it is essential to carry out comprehensive and systematic analysis and research on the formation mechanisms of ground fissures in Weihe Basin.In dissertation, based on the field investigation of ground fissures and mapping, extensive collection of information, by means of a variety of technical methods, in-depth understanding geological environment background of Weihe Basin, the distribution conditions of ground fissures were arranged, the distribution rules and activity characteristics were revealed, development patterns and genetic types were concluded, the formation mechanism was researched, the group mechanism of ground fissures was studied, and the development tendency of ground fissures was estimated.The major research work and results of this dissertation are as follows:(1) By field investigation and data collection,191ground fissures in136places were ascertained for the first time. The distribution of ground fissures in Weihe basin has obvious regional characteristic and zonality characteristic in the space, which the central and eastern of Weihe basin is more, while the western is less. The distribution mainly focused on Xi’an City central and southern of the basin, Jingyang and Sanyuan County northern edge of the basin, Dali County northeast of the basin and Xianyang City central of the basin.(2) According to analyze the developmental state of ground fissures in Weihe basin, the distribution rules of ground fissures were found out for the first time, distribution along fault zone, landforms near boundary. Small and medium-sized seismic active regions.(3) Fine exploration was carried out to the typical ground fissures in Weihe basin for the first time, the basic characteristics of ground fissures were systematically studied, the formation and subtypes were divided, the formation mechanism was analyzed and concluded. There are several different types, such as basin margin fault breaking mode, loess structural joints opening mode, collapsibility ground fissure mode, land subsidence ground fissure mode, basin buried fault creeping model, seismic ground fissure mode, extensional faults coupling land subsidence mode, and so on.(4) Based on the analysis of GPS observation data and deep tectonic data, the dynamic model of continental deformation in Weihe basin was set up. Combining the finite element numerical simulation technology, the relationship between group ground fissures and continental deformation was determined. The results show that the NNW-SSE direction regional tensile stress field in Weihe basin hold a leading post in modern tectonic changing, which is the main power source of group ground fissures in Weihe Basin.(5) The development tendency of ground fissures in Weihe basin was predicted for the first time, and the development positions of new ground fissures were found out. By means of geographic information system technology, the risk assessment of ground fissures was conducted.