Study On Deformation Response Regularity And Mechanism Of Landslides In The Three Gorges Reservoir

Since the Three Gorges first reservoir water from 2003, more than 600 wading landslides have produced deformation in the more than 2600 wading landslides, and nearly ten places have occurred instability decline. During the process of long-term operation of the Three Gorges Reservoir, it will still face the huge pressure of geological disaster prevention. In general, the reservoir water level changes will cause landslide producing dynamic change of groundwater, and groundwater seepage and dynamic role will change slope stress state and stability, which can produce deformation or instability. Considered that the Three Gorges landslide has special geological conditions and the reservoir water has a strong dynamic action, and the goundwater infiltration process and deformation response mechanism are complicated, it needs further research. While using a large number of deformation landslides as sample, statistical analysis of landslide deformation, which is important for guiding the reservoir landslide prediction and evaluation. This is not only the key scientific and technical issues in the Three Gorges Reservoir landslide hazard prevention programs needing urgent study and solve, but also the subject of engineering geology, hydro geology and rock mechanics widespread concerned by the domestic and international scholars.In this paper, through the collection analysis of geological data and deformation monitoring data, mining extraction of the landslide deformation related data and doing more systematic statistical analysis of the response of the landslide deformation since the Three Gorges Reservoir. Moreover, this paper put the typical landslides as prototype, carries out physical model tests and numerical simulation about the landslide reservoir response mechanism. Finally, we summarize the impoundment response mechanism and the response rules of deformation and stability of the Three Gorges reservoir landslide. The main results and understanding as following:1. For reservoir landslides, there are biggish correlations between deformations and shapes of sliding surface, degree of wading. Mainly as follows: 1) the deformations of the straight shaped sliding surface landslides mainly occurred in the falling water segment of the early storage periods, the deformations of the arc and fold-line shaped sliding surface landslides developed both in the rising and falling water segment, the deformations of the settee shaped sliding surface landslides mainly occurred in the rising water segment. 2) the deformations occurred in the rising segment mainly concentrated in the wading level of 0-20%, the deformations occurred in the falling segment mainly concentrated in the wading level of 20-60%. 3) the combinations of advantage for landslides are straight shaped- wading level of 40-60%, arc shaped- wading level of 20-40%, fold-line shaped- wading level of 20-40% and settee shaped- wading level of 0-20 %.2. The deformations of reservoir landslides are apparently responsed to the shapes of sliding surface, rate of water level: 1) The deformation of straight shaped sliding surface mainly influenced by dynamic water pressure and the failure mode is traction type. The deformation of settee shaped sliding surface mainly affected by float weight reduction effect and the failure mode is thrust type. 2) The speed of water level changing mainly impact the effect of dynamic water pressure, the faster the speed is, the more obvious on groundwater lag, and the bigger influence on the landslide stability.3. The mechanism types of reservoir landslide deformation are classified into dynamic water pressure type, float type and compound type. 1) Change in reservoir water of dynamic water pressure type landslide is not only immersed against sliding section, but also applies to promoting sliding section. Underground water level lags change obviously along with reservoir water, the faster reservoir water fluctuation rate change, the greater the lag is. Deformation mainly occurs in the process of water level falling. Landslide stability increase according to water-level rise, likewise, decrease according to water-level fall. 2) Change in reservoir water of floating type landslide only affects anti-sliding section and underground water level has no significant lag with reservoir water. Deformation mainly occurs in the process of water level rising.Landslide stability decrease according to water-level rising, likewise, increase according to water-level falling.