Study On The Factors Affecting The Disaster Mechanism Of Ancient Landslides

As a special geological body with a long time of formation,the ancient landslide,under the long-term coupling of internal and external battalion,re-bonding the soil in the sliding zone to generate regenerative strength,and reached a relatively stable state with the external system.With the continuous construction of various types of engineering in the mountainous areas,it is inevitable to encounter the revival of ancient landslides.Comprehensively studying the formation causes and basic characteristics of ancient landslides,and evaluating their disturbance factors and stability are of great significance for the prevention of ancient landslides.First of all,find out the domestic and foreign literatures and materials about ancient landslides,and systematically summarize the achievements in the analysis of ancient landslide stability,double reduction coefficient method and external force disturbance ancient landslide resurrection.The basic definitions and unique features of ancient landslides are summarized,and the internal and external factors related to the revival of ancient landslides are analyzed.Aiming at the resurrection characteristics of ancient landslides under the influence of external factors,it is concluded that the stability of ancient landslides is affected by both internal and external factors,and the continuous coupling between them eventually leads to the resurrection of ancient landslides.Secondly,the key issues of the double-reduction coefficient method are discussed,including the double-reduction coefficient ratio,the parameter path and the comprehensive safety factor.Based on the strain softening characteristics of rock and soil materials,the functional relationship between shear strength parameters is derived,and a matching reduction mechanism of double reduction coefficient method is established.The calculation and analysis of the example are carried out according to the proposed method,and the feasibility of the method is verified.Then,based on the ancient landslide of gravel soil in the Sangzhi-Zhangjiajie expressway section of Hunan Province,the physical properties of the soil in the gravel soil are tested by means of large-scale direct shearing equipment.Through the method of artificially preparing gravel soil samples,the variation law of strength of gravel soil under different conditions of stone content,water content,compaction degree and shear rate are discussed.On the basis of this analysis,the law of influence of stability of the ancient landslide was analyzed when the water content changed.Finally,taking a middle-aged ancient landslide in Zhangjiaping as the prototype,an analytical model of cut and fill sub-grades is established.Based on the FLAC3 D finite difference method numerical analysis software,the calculation and analysis of the excavation and filling disturbance,the different scale disturbance and the stability analysis of the excavation and filling process in different positions of the ancient landslide are carried out,and the excavation and filling disturbance is stabilized from the whole to the local to the stability of the ancient landslide.The sexual impact mechanism provides reasonable advice for the construction and treatment of such landslides.