Analysis of High Slope Integral Stability of Lanyou Hill Deep Cutting on Nanjing-Hangzhou Expressway

Nanjing-Hangzhou Expressway goes across Lanyou Hill from south to north in Yixing City. The hill extends from east to west and is low.The maximum depth of the west side slope of the cutting is 40 meters. The slope is designed as steps. The height of every step is 8 meters in this region. The character of the slope is rock mass. The main rock layer is Wutong group quartz sand stone of Devonian period and the sandwich mud stone. The rock mass strength is low. The dip angle of the rock layers is small, whose thicknesses chang from middle to large. The mud stone surface of western slope inclines to interior. The influence factors of deep cutting slope stability and breakage mechanism of slope distortion of Yixin Lanyou Hill on Nanjing-Hangzhou Expressway are mainly analyzed. The results show that the first step is mud-rock, the second step and others are quartz sand-rock in this section with high slope on right side,whose slope appears “rigid upward,soft downward”。Because of the particularity of mud-rock which can soften,expand or collapse after it is inundated, the two-layer structure type is disadvantageous to slope stability under the effect of ground water. In order to ensure the expressway normal operation, some protective measures such as slope surface waterproof, prestressing anchored cable and mortar anchored pile framework are taken prevent the slope from deeply destroying.