EPS板减载对宽坦式高填黄土明洞衬砌结构内力和厚度的影响分析

Analysis on Influence of Load Reduction of EPS Board on Internal Force and Thickness of Lining Structure of High Fill Loess Open Cut Tunnel in Wide and Flat Area

为改善宽坦式高填黄土明洞衬砌结构内力,减少衬砌厚度,采用数值模拟方法,研究有无EPS板减载时高填黄土明洞不同位置处衬砌结构内力和厚度随回填土高度的变化规律。结果表明:无EPS板减载时,明洞衬砌结构内力随回填土高度的增加呈线性增长,拱顶至拱肩衬砌厚度呈非线性增长,其余位置呈线性增长;有EPS板减载时,明洞衬砌结构内力和厚度随回填土高度变化规律均与荷载作用下EPS板的应力—应变曲线有关,当EPS板处于塑性阶段时,内力与厚度变化率最大,减载效果最佳,当EPS板进入硬化阶段后,减载效果开始逐渐减弱;明洞的宽高比越大,衬砌结构内力和厚度越大,内力减载量也越大,减载效果越明显。建议针对不同回填土高度、宽高比的宽坦式高填黄土明洞,进行EPS板密度和厚度的优化设计。

In order to improve the internal force of lining structure and reduce the lining thickness of high fill loess open cut tunnel in wide and flat area,the variations of the internal force and thickness of the lining structure along with backfill height at different positions of the high fill loess open cut tunnel with and without the load reduction of EPS board were studied by numerical simulation method.Results show that,without the load reduction of EPS board,the internal force of lining structure increases linearly with the increase of backfill height,and the thickness of the lining structure from the vault to the spandrel of the arch increases nonlinearly,while those at the rest positions increase linearly.With the load reduction of EPS board,the variations of both the internal force and thickness of open cut tunnel lining structure with backfill height are related to the stress-strain curve of EPS board under load.When the EPS board is in plastic stage,the change rate of internal force and thickness is the maximum,and the load reduction effect is the best.When the EPS board is in hardening stage,the load reduction effect begins to weaken gradually.The greater the ratio of width to height of open cut tunnel,the greater the internal force and thickness of lining structure,the greater the load reduction of internal force,and the more obvious the load reduction effect.It is suggested to optimize the density and thickness of EPS board for high fill loess open cut tunnel in wide and flat area with different backfill heights and ratios of width to height.