Abstract: The embankment diseases of Nanbai Highway （from Nanning to Baise） are serious, and the slide and collapse occurred in embankment of expansive soil inclined ground are most serious. The embankment will slide when it has certain degree of slope between the highway route and its vertical direction. Through investigating collapses of embankment in K169 ＋ 500m - K189 ＋ 400m on the Nanbai road, three failure modes of expansive soil embankment are generalized by the method of FEM, that is, the slide in the cross direction, the slide in the longitudinal direction and the longitudinal-cross slide mode. The failure modes of embankment are simulated by the strength reduction finite element method and the causes of embankment failure are discussed. New thoughts about rule of the ＂Specifications for Design of Highway Subgrades＂ （ JTG D 30--2004） are put forward, which provides a new way of thinking to the research on the subgrade filling of expansive soil.

Key words: expansive soil , embankment , failure mode , shear strength ;

摘要： 南宁??百色高速公路路堤病害中以在膨胀土斜坡地基上填筑的路堤发生滑移和坍塌最为严重。当路堤沿公 路路线方向和垂直路线方向有一定坡度时,填筑路堤都有发生滑移的危险。通过对南百高速公路K169+500m~ K189+400m段路堤失稳破坏调查,总结出膨胀土地基路堤填方的3种破坏模式,即以横向为主的滑移、以纵向为 主的滑移以及存在纵横向的空间滑移模式。采用有限元强度折减法对路堤的破坏模式进行模拟,探讨了路堤破坏 的原因。对公路路基设计规范!(JTGD30??2004)有关膨胀土地基路堤填方规定有了新的思考,为在膨胀土地基 上进行填方施工研究提供了新的思路

关键词: 膨胀土, 路堤填方, 破坏模式, 抗剪强度