Study Of Landslide Hazard Assessment On Typical Loess Area In Qianhe Valley, Qianyang County

Geological hazard assessment has become one of important problems that are popularly concerned with since 90s. Geological hazard assessment, aimed at hazard renovation, has special importance in planning and decision about economic development. The achievements in the risk analysis of geological hazard have widely practical value. It is a goal for the development of geological hazard study in the future that carryout the study quantitatively At present, the theory for the hazard analysis of landslide is not perfect, and it is needed to strengthen the comprehensive research cross subjects and fields, so that the risk analysis is combined with the planning of hazard reduction, protective construction and social economy. With the increasing need for land use in urban area, more constructions will be set on different kinds of slopes in future. So it is urgent to carryout positively the study on theory for geological hazard, which has important and realistic significance.There is no uniform theory system in the means of geological hazard assessment. Through the comprehensive studies on the factors influencing geological hazard, this paper established a case study on the geological hazard assessment in Qianhe valley and Qianyang County respectively. This paper also analyzed the stability of typical loess landslide (Tashan Landslide). Researches in the paper mainly include the following aspects:1. Based on the analysis of definition in geological hazard assessment, this paper taken geological susceptibility assessment as the core and basic study in geological hazard assessment. Geological susceptibility assessment is same to the geological hazard assessment in the point of analysis of nature background of geological hazards. Geological susceptibility assessment emphasized in comprehensive analysis of the geological hazards factors: landform, meteorological condition, hydrological geology, etc.. Geological hazard assessment emphasized in the style of the crash (damaged or buried), the scale of the hazard, the run out of hazard, etc.. It is appropriate to appraise the geological susceptibility assessment before geological hazard assessment in the process of geological analysis. In this sequence, we could distinguish the differential factors in the process of geological analysis.2. There are AHP method, information value method, ANN model and limited equilibrium slice method in the process of geological susceptibility assessment. Every method has its merit and deficiency. The AHP method is based on the analysis of experts, and is suitable in case of absence of investigation data but cognition of geological environment; ANN model is based on the method of monitoring classification, and is suitable in case of absence of investigation data but cognition of geological environment; Information value method is based on the statistic method, and is suitable in case of abundance investigation data of large-scale area. Limited equilibrium slice method is a rather strict mathematical technique, and is suitable in most cases. It is sound that to make an integration analysis in the process of geological susceptibility assessment, avoiding the deficiency of single method. It is reasonable to take the integration conclusion of different method as the better one because that every result of method comprised "partial" "real solution".3. The unit for the geological hazard assessment should have the properties of landform and the geological engineering of a single slope. Therefore, it is appropriate to take the surface of nature slope boundary, rock boundary and fault as the unit of geological hazard assessment.4. Tashan loess landslide is rather stable in nature state. In saturated state, Tashan loess landslide is unstable. The minimum FOS of Tashan loess landslide is 1.26 when saturated, approached the critical value of unstable slope, and the crash probability is 0.281%. Tashan loess landslide crashed in local part of the slide mass: the sliding zone located in the back of the landslide, leading edge is on the middle of settlement place, which is same whether in the state of nature or saturated.