Evolution Analysis On Geo-Environment In Three Gorges Region

The Three Gorges Project has impounded for generation ofelectric energy since 2003, and engineering construction of theThree Gorges has been also carried on for many years. However,there are some prominent geological problems such as thelandslide disaster and its preventing. The basic reason of theseproblems is negligent in the evolutionary process ofgeo-environment in Three Gorges area. This article discussesthe genetic mechanism of complex slope in Three Gorges area,through researching on neotectonic movement characteristic,distribution of neotectonic stress field, geomorphy evolutionaryprocess, the time and the process of connection of two rivers.This article provides the theoretical basis of preventing andcontrolling geo-disaster, and provides reasonable instruction ofreservoir area stability forecast when Three Gorges Projectnormally operating.This research represents Three Gorges areagoe-environment surveys such as topography and geomorphy,stratum and lithologic character, geologic structure, seismicity,hydrology geology, dynamical geology phenomenon, on thebasis of reference of others' research.Through some studies on layered landform surface, riversterrace, layered karst landform, geological symbol foundation,and so on in Three Gorges area, a conclusion is drawn thatneotectonic movement is mainly discontinuous ascending, andthe average speed is 0.5mm/a.An improved method is presented and the line of start andend is replaced by the trendline on the plat of MapGis by utilizingGIS technology. Utilizing Visual Basic as a development tool, aprocedure is established. The neotectonic stress field of ThreeGorges region is inversed on the base of MapGis river data andthe principal stress trajectory is drawn. The result is that NE(42°)is the main direction in neotectonic stress field of Three Gorgesregion.A geomorphy evolution modeling of Three Gorges area is setup by using DEM method and GIS technology. Processsimulation of Three Gorges region geomorphy evolution during500,000 years is carried out. The result indicates that the liftingamplitude of midland is maximum since 500,000 years, which isthe genesis of Three Gorges.Combining the GIS technology with fractal theory, using thespatial analysis of MapGis and box-counting method to realizefractal research, can improve the precision and the efficiencygreatly. Utilizing this method, fractal research on the ThreeGorges area river system is carried on. Three Gorges area riversystem fractal dimension value D=1.7239, which indicate thatthe geomorphy of Three Gorges area is on the mature stage,and river system growth completely. The completion of ThreeGorges dam will further delay the corrosion of river system, anddrive it to the old stage.Geology and landform characteristic, the discontinuity ofterrace, the river bottom elevation anomaly, the gravity anomalyand so on in Qutang Gorge indicate that Qutang Gorge is theplace where Chuan river connected with Xia river. Theconnection way of the two rivers has close relationship withKarst collapse. The connection time of the two rivers is0.5~0.7MaB.P., when forth terrace and fifth terrace formed. It iscoincident on time that the connection of two rivers regionfracture activity and the landslide occurs.The unified Changjiang River is principal factor to sculpturecomplex slope and gorge landform, because it results in threestrong geological actions such as the short period and massivewater, strongly erosion, Karst collapse, underground rivercollapse and so on. It is a new tremendous man-made event thatthe Three Gorges project construction and impounding use willstrongly change the geo-environment. Therefore, engineers andscientists have to attach great importance to it.Evolutionary process of geo-environment in Three Gorgesarea is complex, and GIS is an effective method. Utilizing GISand other theory, this article analyses the evolutionary process ofgeo-environment in Three Gorges area, which has certain theorymeaning to research on geology and use vale to geo-hazardprevention and cure in Three Gorges area.