Study On The Geomorphic Evolution Of Sanjiang District And The Geo-Hazards Effect Along The Railway

Endogenous and exogenous processes and consequent neotectonic movement have been highly developing in the Three River region which has four mountains with interjacent three rivers,forming the distinctive landform with high mountains and canyons.The Yunnan-Tibet railway will be built through the Three River region characterized by fragile ecological environment and developed geological hazards and engineering geological problems.Combined with numerical simulation analysis,geomorphic features have been studied to constrain their influences on geological hazards,such as landslide and rockfall.The mainly aspects studied in this thesis are listed as follows:1.The regional geological backgrounds of the Sanjiang area,such as stratum lithology,topography,geological structure,meteorological and hydrological conditions,neotectonic movements,intra-regional active faults and earthquakes,were collated and analyzed;2.Sanjiang district is divided into four types of landforms: mountain-multi-level terrace-river,mountain-stripping surface-alluvial fan-lake,plateau surface-erosion surface-lake or basin and mountain-river-delta-lake.It is divided into erosion structure zone,structural erosion zone,erosion accumulation zone and three zones from the perspective of dynamics;its internal and external dynamical actions are successively reduced,and the distribution is gradually from the Lanping structural junction to the north;3.The influence of internal and external dynamics on geomorphic evolution from three aspects was analyzed: the distribution characteristics of the plane,the information entropy of the geomorphology and the shape of the longitudinal section of the river.The distribution characteristics of the east-west and the north-south direction of the Sanjiang area are analyzed.The three basins are used to calculate the geomorphic information entropy above and below the planes of each basin and each basin,so as to analyze the geomorphic evolution stages of each basin and judge the strength of internal and external dynamic confrontation in each basin.Based on the characteristics of river longitudinal profiles,each river basin was divided into upper,middle and lower sections,and analyze the developmental stages and morphological characteristics of each section;4.Analyze landslides and collapse geo-hazards effect along the Yunnan-Tibet Railway in the Sanjiang district,including slope effect,elevation effect,aspect effect,slope shape effect,slope structure effect and fault zone effect;5.By using the MIDAS/GTS numerical simulation of the dynamic progress of the dominant slopes where the geological disasters in the Sanjiang district are concentrated,respectively analyze the stress,strain,displacement field and plastic zone of the sloped and anti-dip rocky layered slopes.