玄武岩台地区边坡隧道开挖稳定性评价

Stability Evaluation of Slope Tunnel Excavation in Basalt Platform Area

玄武岩台地是一种特殊的地貌类型,常发育成蠕变型滑坡。以浙江省新昌县上三高速某段为研究对象,采用三维数值模拟的方法,对不同降雨工况下的隧道开挖玄武岩台地区边坡稳定性进行了分析评价。首先,在详细的地质资料基础上采用三维模拟软件进行建模,继而基于P-III型分布曲线确定降雨重现期,并采用岩土软件FLAC3D进行隧道边坡开挖下的变形模拟,最后进行不同降雨重现期下的边坡稳定性及变形特征分析。研究结果表明:随着削坡工程的进行,由于坡度变陡,导致位移发生突变,同时应力释放;随着隧道的开挖,开挖处上部出现下榻,底部出现隆起,并且最大位移主要产生在较高山体隧道开挖一侧。降雨强度对玄武岩台地型边坡的稳定性影响较大,最不利工况为100年一遇降雨工况,此时滑坡稳定性系数为0.975,最大变形量为8.0 mm。分析其原因,主要是玄武岩台地滑坡的稳定性与硅藻土滑带、节理裂隙面的发育、降雨入渗滞后性有明显的相关性。该研究成果可为同类滑坡的稳定性评价提供参考和依据。

Beinga special geomorphic,basalt platform often develops into creep landslide.Taking a section of Shang San Expressway in Xinchang County,Zhejiang Province as the researched object,the stability of basalt platform slope in tunnel excavation under different rainfall conditions were analyzed and evaluated by 3 D numerical simulation method.Firstly,based on the detailed geological data,3 D simulation software was used for modeling.And then,the rainfall return period was determined based on P-III type distribution curve,the deformation of tunnel slope under excavation was simulated by rock and soil software of FLAC3 D.Finally,the stability and deformation characteristics of slope under different rainfall return periods were analyzed.The results show that with the progress of slope cutting,the displacement abruptly changed and stress releasedat the same time due to the steepening of slope.With excavation of the tunnel,the upper part of the excavation collapsed and the bottomupliftd.The maximum displacement mainly occurred on the side of the tunnel excavation of the higher mountain.The rainfall intensity has great influence on the stability of basalt platform slope.That rainfall once every 100 years is the most unfavorable condition,when the stability coefficient of landslide is 0.975 and the maximum deformation is 8.0 mm.The main reason is that the stability of basalt platform landslide has obvious correlation with the development of diatomite sliding zone,joint fracture plane and rainfall infiltration lag.The research results can provide reference and basis for the stability evaluation of similar landslides.