砂卵石地层中地铁盾构隧道开挖面稳定性离散元数值模拟研究

Discrete Element Numerical Simulation Study on the Stability of Subway Shield Tunnel Excavation Faces in Sandy Pebble Stratum

为了研究砂卵石地层坍塌失稳模式,建立隧道开挖面稳定性的三维颗粒流数值模型。首先将砂卵石土层从松散到致密分为4种情况,并进行参数标定;接着分析埋深比和内摩擦角对隧道开挖面破坏模式、极限支护力等的影响规律;最后,对砂卵石地层中隧道开挖面失稳模式开展研究,并基于数值模拟结果对砂卵石地层中塌落拱的高度进行修正。研究结果表明,(1)内摩擦角越大,支护力受埋深比的影响越明显;不同埋深比下,极限支护力均随着内摩擦角的增大而减小,并且埋深比越大,支护力受内摩擦角的影响越明显。(2)随着内摩擦角的增大,破坏区逐渐减小;在相同内摩擦角下,埋深比大时破坏区范围更大。(3)当埋深比超过1.0时,大部分地层都可以成拱,其破坏区形状为椭球体和旋转抛物面形成的组合体。(4)浅埋情况下,塌落拱无法形成,修正公式与模拟结果误差均在15%以下,修正公式具有一定的适用性。

In order to study the collapse and instability modes of sandy pebble stratum,a three-dimensional numerical model of granular flow is established to analyze the stability of tunnel excavation faces.Firstly,the sandy pebble stratum is divided into four conditions ranging from loose to dense,and the parameters are calibrated accordingly.Then,the influence of burial depth ratio and internal friction angle on the failure modes of tunnel excavation faces and the limit support pressure is analyzed.Finally,the instability modes of tunnel excavation face in the sandy pebble stratum are studied,and the height of collapse arches in the sandy pebble stratum is modified based on the numerical simulation results.The research results indicate the following:(1)The larger the internal friction angle,the more significant the influence of burial depth ratio on the support pressure.Under different burial depth ratios,the limit support pressure decreases with an increase in the internal friction angle.Moreover,the larger the burial depth ratio,the more significant the influence of the internal friction angle on the support pressure.(2)As the internal friction angle increases,the failure zone gradually decreases.Under the same internal friction angle,a larger burial depth ratio results in a larger range of the failure zone.(3)When the burial depth ratio exceeds 1.0,most layers can form arches,and the shape of the failure zone is a combination of ellipsoids and rotated paraboloids.(4)In shallow burial depth conditions,collapse arches cannot form.The error between the modified formula and the simulation results is below 15%,indicating that the modified formula has a certain applicability.