地震作用下高填减载明洞土压力研究

Earth pressure characteristics of high-filled cut-and-covertunnels under earthquake action

针对西北黄土高原地区高填方减载明洞工程,明洞顶部铺设EPS板可以有效减小明洞周围土压力,保证结构安全。然而,由于填土的动力高敏感性,地震作用将会对已经稳定的回填土体产生扰动,导致明洞结构周围土压力发生较大变动,对明洞结构造成不利影响。因此,采用数值模拟方式,对地震作用下的高填减载明洞周围土压力变化特性及土拱效应进行研究。研究结果表明:地震作用下,由于减载作用产生的土拱效应始终存在,使得土拱高度降低和效应减弱;明洞顶部竖向动土压力时程曲线在距明洞中央0~5 m范围内变化趋势一致,在距中央5~7 m范围内变化趋势相反,当明洞顶竖向动土压力达到峰值时,平均竖向动土压力为平均竖向静土压力的1.14倍;明洞两侧水平动土压力时程曲线变化趋势呈“此消彼长”状态,当水平动土压力达到峰值时,平均水平动土压力为平均水平静土压力的2.89倍。

For the high-filled cut-and-cover tunnel(HFCCT)constructed in the loess plateau of Northwest China,laying the expanded polystyrene(EPS)plate on the top of the cut-and-cover tunnel(CCT)effectively reduces the earth pressure around the CCT and ensures structural safety.However,given the high dynamic sensitivity of the backfill,earthquakes will disturb the stabilized backfill and cause considerable changes in the earth pressure around the CCT,thus adversely affecting the CCT.In this paper,the numerical simulation method is used to study the characteristics of earth pressure change and soil arching effect around the HFCCT under earthquake action.The results show that under seismic action,although the soil arching effect triggered by load reduction of the EPS plate remains,it weakens with the decline in soil arching height.The variation trends of the time-history curves of vertical dynamic earth pressure are consistent in the range of 0-5 m from the center of CCT,and the opposite is observed in the range of 5-7 m from the center of CCT.When the vertical dynamic earth pressure at the top of CCT reaches the peak value,the average vertical dynamic earth pressure is 1.14 times the average vertical static earth pressure.The opposite change trends of the time-history curves of horizontal dynamic earth pressure occur on both sides of CCT.When the horizontal dynamic earth pressure reaches its peak value,the average horizontal dynamic earth pressure is 2.89 times the average horizontal static earth pressure.