Research On Genetic Mechanisms And Activity Of Chang'an Earth Fissures

As one kind of geological disasters,earth fissures occur in many areas and represent an important economic problem associated with damage to construtions,especially in Xi'an where is located on the hanging wall of Lintong-Chang'an fault zone.However,within the fault zone,there also exist Chang'an earth fissures,which are similar to the Xi'an earth fissures and they are hidden or present so far.Therefore,it is of great significance to research on the genetic mechanisms,activity characteristics and induced factors of these earth fissures.Based on the study of Xi'an earth fissures,this paper mainly analyzed the Chang'an earth fissures from two aspects.On the one hand,considering the regional geological tectonic movement,the initation of Chang'an earth fissures was discussed,which is controlled by Lintong-Chang'an fault zone in the Weihe basin.On the other hand,considering the influence of human engineering activities,the influence of pumping groundwater on Chang'an earth fissures' activities was discussed.Numerical simulation was developed using the software flac3 d to analyze the initation and propagation of Chang'an fissures induced by the extension of Lintong-Chang'an fault zone.The results show that fissures originate in the hanging wall of the fault zone,where happens the compensatory collapse while the hanging wall slips along the fracture plane caused by gravity.Then,taking the actual human engineering activities and the stratigraphic structure of the fault zone into account,the effect of groundwater extraction on the Chang'an earth fissures' activity was simulated.The results show that duing to the earth fissures,pumping groundwater causes different water levels in the hanging wall and the footwall and leads to the irregular subsidence,which will strengthen the activity of the earth fissure.In short,the impact of the pumping well in the hanging wall is greater than it's in the footwall;the smaller the distance between the pumping well and the earth fissure,the greater impact on the earth fissure;the deeper the pumping well,the greater impact on the earth fissure;the different sedimentary strata between the hanging wall and the footwall will also strengthen the activity of the earth fissure.