不同掏蚀深度下古城墙的稳定性数值分析

以浙江良渚古城的宽顶古场面墙稳定性问题为研究对象,本文针对古城墙可能出现的不同深度的风沙掏蚀的实际工况,通过有限差分软件FLAC3D,建立计算模型进行了稳定性分析,探讨了不同掏蚀深度下城墙破坏机理和规律.研究表明:当城墙墙根掏蚀深度不是很大时,城墙整体稳定,土体开始出现比较小的位移量,掏蚀部位及其周围出现局部塑性破坏现象.随着掏蚀深度的增加,城墙塑性破坏区域不断向城墙体内部、顶部及顶部后缘范围发展,城墙上的土体位移量随着掏蚀深度的增加而呈数量级的增加,直至城墙出现整体崩塌破坏.掏蚀作用加剧了地震作用下城墙体的破坏,在掏蚀部位形成潜在破坏口,内部形成塑性贯通区,造成墙体整体崩塌.

Analysis and Numerical Calculations of Stability on Ancient City Wall under Various Sapping Depths

The width of the top of the ancient city wall in Liangzhu,which is known as the first city in China,reaches 40~60 m;stability issues for this wall have been identified.Finite differences determined through FLAC3D software were considered to build a calculation model for examining failure laws and the mechanism of the ancient city wall under various sapping depths.The results show that when the sapping depth is not sufficiently large,the entire city wall is stable,and local plastic failure occurs near the sapping location.When the depth of sapping increases,the plastic failure area becomes wider and deeper and can reach the top of the wall.In addition,the soil displacement increases until the entire wall slides.The sapping contributes to the damage of the wall,a potential slide opening appears in the sapping area,and a plastic area appears in the wall,which leads to sliding of the entire wall.