宁杭高速公路兰右山深路堑高边坡整体稳定性分析

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

南京～杭州(宁杭)高速公路(江苏段)线路近南北向穿越宜兴市兰右山。兰右山山体走向近东西向, 为剥蚀低缓丘陵。深路堑西侧边坡最大挖深约40m,设计边坡为台阶式,每级边坡高度为8m。该段路堑边坡主要 为岩质边坡,其主要岩组为泥盆系五通组石英砂岩夹泥岩,岩石强度一般较高,岩层产状平缓,具中～厚层结构类 型。西侧边坡泥岩层面稍内倾。在分析深路堑工程地质特征、边坡稳定性影响因素及边坡变形破坏机理的基础上指 出:该段西侧高边坡一级台阶为泥岩,二级以上台阶为石英砂岩,边坡呈“上硬下软”双层结构。由于泥岩岩性特殊, 具有浸水软化、膨胀、崩解、易风化等特征,在地下水诱因下,这种双层结构类型对边坡稳定性十分不利。为了保证 高速公路运营安全,宜采取主动防护措施,如坡面封闭隔水处理、预应力锚索、砂浆锚杆框架等防护方案,以防止发 生边坡深层破坏。

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.