Sangri-Jiacha Valley Segment Stress Field And Tunnel Rockburst Forecast

Lasa – Linzhi railway line along the Brahmaputra overall distribution, which Sangri – Jiacha gorge steep terrain, poor geological development of the railway line selection is usually grown mountainside tunnels and composite uphill tunnel to avoid significant adverse geological conditions, in the Valley High stress, often includding rock burst and large deformation of tunnel construction, not only affect the construction schedule, and threaten the safety of construction personnel and equipment. Therefore, to carry out Sangri- Jiacha check canyon valley to study the stress field characteristics and Highland Valley hillside deep influence of stress on the tunnel grew up, not only has important practical significance for the Yunnan-Tibet railway construction and operation, and the western mountains and canyons area other major construction projects of great significance.This paper selected to Sangri- Jiacha gorge for example, through field research, field tests, geomechanical analysis, statistical analysis to stress, numerical simulation methods, evolution of the tectonic stress field of study, and the study area present stress field the basic characteristics of the tunnel excavation under stress conditions were upland valley rock burst prediction, specific content and achievements are as follows:(1) Based on field geological data analysis and demonstration, in-depth understanding of the engineering geological conditions of the study area topography, lithology, geological structure, formation and evolution of the valley a preliminary analysis.(2) Research on regional tectonic stress field evolution is analyzed by regional early Quaternary tectonic stress field and the current tectonic stress field characteristics in the main part of Qinghai-Tibet Plateau, the maximum principal stress direction is north east, the plateau north and east edge of change in the more large, and to stress the measured data for statistical analysis, to the north of the study area tectonic stress field in the East- NNE nearly horizontal squeeze, some areas deflection.(3) the structure of the surface area of Rock Valley Slope conducted a detailed investigation, the main structure of the surface has been fine description and analysis of the key controlling structural plane do focus on analysis, the region, the development direction of the structural advantage is 192°?64°?102°?79°and 26°?43°.(4) By collecting a large amount of stress measurement data, analyze the distribution of the measured stress direction to stress the study area. Study on the variation of the measured area of shallow crust to stress with depth, and the establishment of a research area vertical stress ?v, the maximum horizontal stress ?H, minimum horizontal stress with depth ?h scatter distribution, and the corresponding Statistical Analysis.(5) Analysis of the valley evolution, generalized cutting mode and of lower valley views, the establishment of three-dimensional geological model of the study area, the use of FLAC3 D numerical calculation software for stress measurement is based on data for the study area of initial stress field inversion analysis identify the Brahmaputra Sangri- stress distribution of stress field in the valley gorge plus check.(6) On the basis of the tunnel site engineering geological survey and exploration, combined with analysis of Valley Heights stress field, numerical simulation of the impact of stress on high ground tunnel project, analysis of secondary stress field after excavation of the tunnel, the tunnel evaluation the possibility of the occurrence of rock burst, and propose effective preventive measures.