包山式古城墙土坡稳定性分析

Stability analysis of the soil slope of ancient city wall surrounded by mountains

南京古城墙文物价值非凡,滑坡是古城墙的典型损伤,对包山式城墙危害巨大。以狮子山段城墙历史滑坡勘察资料为背景,对砖砌体与土体的复合结构进行分析并适当简化。采用GEO-SLOPE软件中的瑞典法、简化Bishop法、Janbu法、Spencer四种极限平衡分析方法,对考虑自然情况、不同浸润深度、施加锚杆三种工况下的土坡稳定性进行分析。结果表明:各种方法对浸润深度的敏感程度很接近,评价土坡稳定性时以简化Bishop法得出的结果最安全;对于常见浸润深度2~4m,四种方法所得边坡安全系数为1.5~1.6;增加锚固长度比增加锚杆预加力对提高边坡安全系数效果更为明显。

The cultural relics of the ancient city wall in Nanjing are of great value, and landslides are typical damages to the ancient city walls and cause great harm to the city wall surrounded by mountains. Based on the historical landslide survey data of the Shizishan section of the city wall, the composite structure of brick masonry and soil was analyzed and appropriately simplified. Using four limit equilibrium analysis methods in GEO-SLOPE software, namely Swedish method, simplified Bishop method, Janbu method and Spencer method, the soil slope stability under three conditions of considering natural conditions, different infiltration depths and applying anchors was analyzed. The results show that the sensitivity of various methods to the infiltration depth is very close, and the result obtained by the simplified Bishop method is the safest to evaluate the stability of soil slopes. For the common infiltration depth of 2~4 m, the safety factor of the slope obtained by the four methods is 1.5~1.6. Increasing the anchorage length is more effective in improving the safety factor of the slope than increasing the prestressing force of the anchor bolt.