Study On Engineering Characteristics Of High Altitude Soft Soil On Sichuan Tibet Railway

The Sichuan-Tibet Railway is located in the mountainous area of the southeastern Tibetan Plateau between the Gangdise Mountain and the Nyainqentanglha Mountain and the Himalayas.The topographical and geological conditions are extremely complicated.Due to climatic conditions,hydrological conditions,provenance characteristics,sedimentary conditions,etc,the railways will encounter typical high-altitude soft soils.In the process of railway construction and operation,engineering problems caused by high-altitude soft soil may be faced.In the construction of China's railways,it has been deeply affected by soft soil.Among them,there are many high-altitude railways,such as the Lijiang-Xianggelila line and the La sa-Linzhi line.Soft soil.Due to the high compressibility and low strength of soft soil,it is reflected in the settlement of the building,which is large in settlement and poor in drainage,which leads to unfavorable drainage and consolidation of foundation.In view of the difficulties encountered in the above construction,it is necessary to study the distribution,genesis and physical and mechanical properties of high-altitude soft soil along the Sichuan-Tibet Railway.In this paper,the distribution characteristics and genesis of typical soft soils in five different regions,namely Xinduqiao,Litang,Bangda,Cuopugou Mouth and Cuopugou,are analyzed systematically,and the causes of soft soil are divided into four categories.That is,the cause of alluvial,the cause of slope flooding,the cause of deposition of hot melt lake,and the cause of marsh sedimentation.Site investigation showed that the content of coarse particles and organic matter in soft soil was high.The particle analysis and organic matter test analyzed the difference of soft soil particle composition and organic matter content between soft soil in Yunnan and Tibet,and in the middle and lower reaches of the Yangtze River.Based on the test results of water content,specific gravity,liquid-plastic limit,compression and direct shear,the physical and mechanical properties of high-altitude typical soft soil of Sichuan-Tibet Railway were studied,and the values of physical and mechanical parameters of soft soil in the study area were proposed.In order to explore the improvement effect of cement admixture and curing time on high-altitude soft soil,the mechanical properties of cement-modified soft soil with different cement incorporation and different curing time were carried out,and the high-altitude softness of cement-modified Sichuan-Tibet Railway was proposed.The optimum cement content and optimal curing time of the soil.The results can provide reference for the study of high altitude soft soil modification in Sichuan and Tibet.