High Slop Safety Analysis Of The Dazui Mountain In Niufei Village Under The Condition Of Continuous Rainfall After Earthquake

Maybe ""5.12"Wenchuan earthquake" shadow is not from the people’s mind,"4.20Lushan"7earthquake once again bring people great mental impact, seismic moment, and the collapse of the housing diversion, casualties, property loss, environmental change. After the earthquake, the secondary disasters, landslides can be seen everywhere, earthquake relief, reconstruction is the greatest threat in the strong rainfall or continuous conditions, these residues produced by the landslide caused by earthquake collapse, the mountain of loose solid material is very easy to cause landslide happen again and the formation of debris and other major secondary geological disaster. Experts predict that within5years of geological disasters hard-hit landslide, debris flow will occur frequently, the performance of the more prominent disaster chain.Domestic and foreign experts study shows, mechanism inducing the landslide is very complex, but the most fundamental reason is that rainfall infiltration leads to an increase in weight of slope, soil particles decrease in shear strength, thereby causing slope system matrix suction field, soil bulk density field and underground dynamic water pressure field changes, thus affecting the security and stability of the slope, and the formation of influence of danger or disaster, people’s safety of life and property. Research shows that both at home and abroad, research on simulation theory for saturated-unsaturated seepage and numerical current is not very deep, especially in simulated groundwater transient seepage field caused by continuous rainfall conditions, analysis of influence factors are still need to be further.In view of the above, taking the high slope actual project of the Dazui mountain (which is in the harder-hit area) in Niufei village, Pingtong town as example, the dissertation carried out the study on high slop safety evaluation after earthquake under the condition of continuous rainfall to avoid or mitigate the landslide hazard. The specific research works are as follows:a) A detailed investigation on the earthquake and rainfall-induced landslide was carried out in different regions, such as Lijiaba (in the west side of Pingtong town), Maliu mountain (in the northeastern side of Pingtong town), Dazui mountain (in Niuwen Village) and Houbei Moutain (in Wangong town, Hanyuan county, Yan’an city), to find out the circumstance of landslide hazard and slope remediation. And then the research object was selected.b) Using the high slop geomaterials of Dazui mountain and rainfall-induced landslide geomaterials of Houbei mountain in Hanyuan county, the impact of rainfall infiltration on the mechanical parameters of slope geomaterials after earthquake was researched by laboratory expriments. And then a function of the soil strength parameters (cohesive strength, friction angle and water-content coefficient) was established. The study provided the basic data for the slope safety evaluation under the rainfall condition.c) According to the rainfall infiltration theory of the saturated-unsaturated soil, taking the rainfall infiltration’s increscent effect on the penetration and weight of soil and softening effect on soil strength into account, the numerical analysis model of saturated-unsaturated soil slope stability under the rainfall infiltration condition was established with elastic-plastic finite element analysis theory and the corresponding computer program USlope-Fem was programmed.d) For the high slop of Dazui mountain, the numerical simulation of the slope seepage stability was carried out and the safety coefficient of slope engineering was evaluated quantitatively under the condition of continuous rainfall. The results showed that rainfall infiltration can lead to the increase of the water content in the upper soil of slope, the disappearance of negative pressure zone and the emergence of saturated zone. With the rainfall time, the transient saturated zone in the surface of slope is formed and it can transfer into the internal gradually. Then the weight and penetration of the soil significantly increased and the shear strength was significantly reduced. The shearing stress increased in the slope and sliding force was increased significantly along the soil-bedrock interface. The plastic strain area gradually extended to the top of the hill and connected gradually. Therefore, the local slump occured in the free face and this phenomenon was manifested as traceable sliding. In view of the above, it was recommended that the pre-manual processing needed to be used or the deformation monitoring should be strengthened for the study slope and the warning of slope safety was especially important under the continuous rainfall condition.