The Stability Analysis Of Typical Cutting Slope Of SanLiu Expressway

China is a montanic country with that about 60% of the land are mountain areas, especially in the western, it is the complex landform that strongly affect the construction of engineering. In order to improve the development of the western, the project of Develop of Western Regions were formulated. Recently, with the develop of western regions, more and more expressways were constructed, actually, there were no doubt to face the cutting loess slope during the construction. The expressway of San Jiang to Liu Zhou in Guang Xi province is a important part of the expressway system of “Four vertical, Six horizontal and Three branches”, which is the major of the expressway from San Jiang to Bei Hai. Based on the typical cutting loess slope of San Liu expressway, firstly geological survey and a series of laboratory tests and in-situ tests were carried out to analysis the stability of the nature slope in qualitatively. Then based on the soft of FLAC3 D, the finite difference strength reduction method were used to simulate the nature slope and cutting loess slope, through it the distribution of shear strain, plastic zone and displacement were obtained. It shows that:(1) based on the in-situ geological survey, the slope was stable. The main soil layer are silty clay, weathered phyllite, strongly weathered phyllite and weak weathered phyllite;(2) the FLAC3 D numerical simulation of nature slope with finite difference strength reduction method indicated that the safety factor is 1.22, the slope is stable and the displacement is small, the plastic zone have not been breakthrough without any sliding surface;(3) after excavation, the safety factor of cutting loess slope is 0.81, it means that the slope is unstable. The plastic zone inside the expressway has been through out of the slope and the arc-shape sliding surface has been formatted. The toe of slope raised and the top soil moved down;(4) we suggest that it is necessary to excavate the slope step by step, prestressed anchor cable framework could be used inside slope of the expressway and protected the outside slope of the expressway by vegetation.