Morphotectonics-based Analysis Of Disaster-Pregnant Environment And Disaster-reduction Strategy For Line Engineering

China, located in the southeast corner of the Eurasian plate, besieged by the India plate, the Pacific plate, the Philippines plate and the Siberia plate. Present tectonic stress in this region is strong active. China has the most continental strong earthquakes around the world, and the gravitational hazards here are extraordinary developed. Technology of route selection in mountain area is a complex procedure, without any margin for alignment designs stage, weak in technology accumulation.At present, technology of route selection in mountain still stays at the level of the principles listed. So the key of optimization design can only be placed on a more macro level operations.From the perspective of tectonic geomorphology, the disaster-pregnant environment is analysed in this artical.From hundreds or even thousands of kilometers of regional route location operations, is an engineering practice matching to the scale of tectonic geomorphology. With the advanced technology application, like remote sensing and ArcGIS, useful information is get high efficiency and low cost in the spatial and temporal scale of tectonic geomorphology.Then the scheme comparison in a wide range is achieved.The clearance of regional geomorphic features and inference the disaster’s origin in the perspective of tectonic geomorphology is the basis of quality line selection operation. Yet the mountain environment disaster is the result of the coupling of the earth’s endogenic and exogenic.Endogenic is systematic, is from global plate tectonics, yet the exogenic is random. The effect of endogenic and exogenic is mutual promotion and intercoupling.And this effect is the basic reason for the formation of geological disasters.Based on the theory of the Davis’ Cycle of Erosion (youth-maturity-old age), this paper expound and prove the sequence of within-reaching-deviation from the critical slope in one ideal cycle, the mountain hazards present the sequence from develop to strong and then decline respectively. This is the principle that the tendency prediction of collapse-landslide induced by earthquake estimated by judging development stage of drainage basin.Davis’ Cycle of Erosion assumes that the whole basin develops synchronously.According to this defect, the method of distinguishing different stages of basin by selecting the breakpoint of SL index is proposed based on the Feedback mechanism on the valley and valley slope. Therefore, This method eliminates the spatial dependency of small drainage basins.There are two methods expounded to confirm the status of valley slope:by the Erosion Cycle Theory and the valley longitudinal profile index.The two methods are proved to be correct, but the accuracy is different. The accuracy of method Based on The Erosion Cycle Theory can match with the requirement in principle selection stage.yet the other one is only useful for rough judgment. The methods proposed in this chapter can provide reference for the regional mountain disaster risk prediction of other triggering factors.In the feasibility stage of the route selection, it is inadvisable to do large-scale crustal stress on-site drilling examination along the route due to the route is not determined. Based on existing measured stress data, b-value, and depth H-value as independent variables, the evaluation model of crustal stress was developed. Compared with the current method using the depth as the only independent variable, the evaluation precision is significantly increased. Baesd on the landslides triggered by LuShan Earthquake(blind reserve-fault earthquake),The dominant direction of the number of landslides is only consistent to one of the dominant aspects of the natural slope. Then it is put forward that predominant direction of natural slope is control factor of the direction of collapse and landslide considering the asymmetry of mountain slope landform. Based on the Principle of Antagonism, the direction of the new tectonic stress field is also a global factor of the direction of collapse and landslide. The directions of the maximum cumulative acceleration control the sensitivity directions of landslides in the surrounding range of the stations. For earthquakes from blind fault, it might be a universal law that the above three factors control the direction of earthquake-triggered landslides.Glacial debris flow is the result of endogenic and exogenic.At the margin of rapid uplift area, river cut down tapidly.The original U-shaped glacial Valley is converting to the V-shaped Valley:U-shaped Valley in upstream and V-shaped River Valley in downstream.The wide and slow flat U-shaped Valley in upstream provide a place of gathering loose material and water.the deep, narrow, steep V-shaped River Valley in downstream provide circulation area and the essential slope requirement for the debris flow initation.This is the ideal terrain for debris flows. The original glacial Valley and cirque in the upstream is a natural catchment terrain.and this terrain accelerated the formation process of large debris flow terrain.The mitigation countermeasures proposed in this paper can provide direct references to the proposed Sichuan-Tibet Railway. Glacial lake outburst and glacial debris flow usually lead to a sequence of disasters. This sequence of disasters can cause large-scale effects in the main river. Changing the road spatial location is the first choice in these areas. Avalanche and unlikely blockage of the river by glacier debris flow are point disasters. Countermeasures for point disasters usually include changing road spatial location, point disaster improvement projects and road protection measures. One can choose the right plan through comparing the technical and economic indices. Through the comparison between landslides and snow avalanches, both the two phenomenon are the formation sliding surface due to dramatic changes of water content. Therefore, the Equivalent friction coefficient can be used to estimate the avalanche distance.36 typical trench medium wet snow avalanche paths are selected in the Palongcangbu river basin, and Plot the relationship between the equivalent friction coefficient and formation area. The statistic shows that: there is a good linear relation between the equivalent friction coefficient and the formation area (the correlation coefficient is R2=0.425).Based on this relationship, the relationship between avalanche distance and the formation area, the maximum height is in the Palongcangbu river basin.