浅埋大跨偏压隧道的破坏模式分析

Analysis of Failure Mode of Shallow-buried Asymmetrically-pressured Tunnel with Large Span

为研究浅埋大跨偏压隧道破坏模式,利用有限元强度折减法对三心圆曲墙式断面隧道和马蹄形断面隧道在不同埋深、坡比工况下的塑性应变和安全系数进行研究,得到隧道的破坏模式及发展规律:无偏压条件下,随着埋深增加,三心圆曲墙式断面隧道最大塑性应变由拱肩向下转移到边墙附近,而对于马蹄形断面隧道,当埋深较浅时,在拱肩和边墙出现破裂面,随着埋深的增加拱肩的破裂面逐渐向边墙脚转移;当存在偏压时,三心圆曲墙式断面隧道浅埋侧先破坏,随着埋深的增加,最大塑性应变由浅埋侧拱肩移到浅埋侧边墙位置,对于马蹄形隧道,破裂面从浅埋侧拱肩和深埋侧边墙转移到墙角;在同一埋深条件下,三心曲墙式断面隧道安全系数高于马蹄形隧道安全系数。

The failure mode of shallow-buried asymmetrically-pressured tunnel with large span is studied in the paper.The plastic strain and safety factor of triple-center curved wall tunnel and horse-shoe shaped tunnel under differentdepths and slope ratios are analyzed by finite element strength reduction method. Some conclusions are drawn as follows：1） When the tunnel is under normal pressure condition, the maximum plastic strain of triple-center curved wall tunneltransfers from the arch to tunnel sidewall with the burial depth increase. When the tunnel is shallow-buried, the fracturesurface of horse-shoe shaped tunnel transfers from the arch and sidewall to wall feet with the burial depth increase. 2）When the tunnel is under asymmetrically-pressured condition, the failure firstly occurs in tunnel shallow buried side,and the maximum plastic strain of triple-center curved wall tunnel transfers from the arch to sidewall with the burialdepth increase. The fracture surface of horse-shoe shaped tunnel transfers from the arch of the tunnel shallow-buried sideand sidewall of the deep-buried side to the tunnel wall feet with the burial depth increase. 3） The safety factor of triple-center curved wall tunnel is larger than that of horse-shoe shaped tunnel under same buried depth.