Risk Assessment And Decision Of The Expansive Soil Railway Subgrade In Southwest Mountain Area

In the great development of the west, a rapid development of construction of railway in southwest area of china was obtained, and the standard of railway also constantly improving. The geological condition of Southwest is complex, and the geological disaster often happened in the construction process of railway. The distribution of expansive soil in the southwest area is widely, the harm of the geological disaster of expansive soil to construction and operation of railway is becoming more and more serious, and the factors of railway subgrade security risk in expansive soil area is very massive and complex, and the risk assessment to railway subgrade was seldom carried out, and the related research results were rarely.Therefore, during the southwest railway construction, risk assessment of the expansive soil railway subgrade is very necessary to avoid engineering accidents and reduce risk loss.In this thesis, the risk assessment based on both at home and abroad present research situation and commonly used method, and referenced the existing results of of tunnel engineering and hydropower project risk assessment, and choosed a qualitative and quantitative method according to the characteristics of railway subgrade engineering, and integrated used analytical hierarchy process (AHP) and expert scoring method, established the expansive soil subgrade risk assessment in the analysis model, and obtained the risk factors influence degree for expansive soil subgrade security, and put forward reasonable suggestion for the serious factors.The risk level division standard of railway subgrade has formulated, and the corresponding accepting criteria were put forward. Based on the rank of the possibility and the rank of consequences of geological disaster, and estimate the rank of railway subgrade in expansive erea through the expert investigation, and the corresponding accepting criteria were put forward.The sensitivity analysis of earth pressure calculation to the gravity retaining wall of railway cut has completed, and obtained the sensitive factors of expansive soil gravity retaining wall. Taked a risk assessment in a segment of nankun railway cutting for example, deduced the procedures of risk assessment and decision-making of specific project.Finally, the specific treatment countermeasures prevention and control of the risk of expansive soil railway subgrade in the design phase and the construction phase were put forward.