Analysis Of The Geological Characteristics And Stability Of Quaternary Deposits Of Shallow Buried Section Of Tunnel In The Southeastern Margin Of The Qinghai-tibet Plateau

In the southeast margin of the Qinghai Tibet Plateau,a large number ofQuaternary deposits distribute in the valleys and Foothills.With the development ofeconomy and the reconstruction of post earthquake disaster, the projects ofinfrastructure and hydropower construction are reached to mountain canyon areadeeply in the southwest area. These projects relate to Quaternary deposits and theengineering geological problems are becoming more and more serious.Therefore,ithas important theoretical significance and practical value to stably study geologicalcharacteristics and engineering system of Quaternary deposits, and put forward thereasonable control measures.Based on the full collection on the results of previousstudies, through the field geological survey, I study the regularity of thedevelopment the Quaternary sediments of the southeastern margin of Qinghai TibetPlateau.Forthermore,I reveal the characteristics of distribution and fabric ofQuaternary sediments.The research results show that the sediment composition is diversified, and thesorting is poor.The consisting of particles includs boulder, stone, gravel, coarse sand,medium sand,sand,silt and clay. It plays an important role in the continuity ofaccumulation is that the clay is contented in the accumulation.But the lithology ofQuaternary sediments and lithology of bedrocks are the same.It is included most ofslate, phyllite, and metamorphic sandstone in Quaternary deposits.There are differentclay proportion in the different parts of deposits.With the method of digital imageprocessing technology and indoor test, the grain of glacial sediment had been sizeanalysised.Using the fractal theory,it has researched the composition of glacier deposit,the morphology and arrangement characteristics of gravel in this paper.The section of surrounding rock was detected by geological forecast detection in shallow buriedtunnel,As far as possible in order to exact analysis the engineering stability of theQuaternary sediments in study area.It analysises the internal structure of matter, thedegree of loose,and groundwater occurrence condition of Quaternary deposits basedon the analysis of geological radar diagram. This provides basic data for stabilityanalysis.Then the surface subsidence rate and the subsidence displacement waslearned by means of monitoring, especially through the surface subsidence monitoringand data analysis.According to the standard of three level of displacement,we canput forward corresponding, and provide early warning and guidance for theengineering construction.Monitoring results show that there was larger displacementin Quaternary deposits which was disturbance by excavation in tunnel, and was inshort-term risk.According to field investigation, the main failure form of glacialdeposits are landslide, collapse and debris flow in this area.The main factors affectingthe development of geological disaster are the engineering characteristics, rainfall,river erosion and excavation of glacial deposits.It has certain reference value andreference meaning to the rest of the similar engineering geological problems with theresearch methods and research ideas which used in this paper.