高填黄土明洞土拱效应及土压力减载模型分析

Model analysis of earth pressure load reduction and soil arch effect for high fill open cut tunnel in loess area

通过室内模型试验研究高填方明洞土压力随填土高度的变化规律以及高填方明洞的拱效应,并比较以松散土体或EPS板做为变形层的减载效果及有无边坡对土压力的影响。试验结果表明:当填土达到一定高度后,明洞上方将产生土拱效应,拱顶部分土压力将由拱脚附近土体分担,由于土拱效应的不稳定性,使拱顶土压力随填土高度呈非线性规律变化,采用EPS板做为变形层的加筋减载效果优于松散土体,拱脚土压力受边界条件的影响较大。根据加筋减载原理和模型试验结果,建立了加筋减载力学计算模型,利用朗肯土压力理论,提出采取设置变形层和铺设土工格栅减载措施的高填方明洞顶的非线性土压力计算公式。通过现场试验证明土工格栅减载效果的有效性、耐久性以及本文计算方法的正确性,这对高填方明洞以及土工格栅减载结构的设计施工具有参考价值。

The influence laws of embankment height and the soil-arch effect of high fill open cut tunnel on earth pressures are studied by indoor model tests. The load reduction effects when loose soil and EPS are used as deformation layer are compared and the influence of slope on soil pressure is analyzed. The results show that the soil-arch effect will occur when the fills on the open cut tunnel is up to a certain height,and the earth pressure of arch crown will be shared by the soil near the springing. Due to the instability of soil arch effect,the earth pressures on the top of open cut tunnel increase nonlinearly with the filling height. As deformation,the EPS has better load reduction effect than the loose soil.The earth pressure of springing is greatly influenced by the boundary conditions. On the basis of the model test results,the reinforcement load reduction mechanical calculation model is established. According to the Rankine earth pressure theory,the computational formula of nonlinear earth pressure on the top of open cut tunnel with deformation layer and laying goegrid is proposed. Field experiments on a open cut tunnel demonstrate that the geogrid has good load reduction effect and durability,and that the proposed calculation method is accurate. The research results can provide reference value for design and construction on geogrid load reduction structure and high fill open cut tunnel.