沟槽式高填黄土明洞卸载模型试验研究

 为研究不同卸载措施下沟槽式高填黄土明洞垂直土压力、土体沉降变化规律，通过室内模型试验，对不同方案下的卸载效果进行对比分析。结果表明：增大填土边坡坡角、明洞顶设置低压实土、铺设土工格栅、提高明洞两侧填料压缩模量可减小明洞洞顶土压力，其中，增大边坡坡角卸载作用最优。与无边坡相比，明洞洞顶垂直土压力卸载率可达20.6%，若与低压实土形成的土拱效应及土工格栅的“提兜效应”相结合，有利于进一步减小明洞洞顶垂直土压力。同时，填土高度较低时，垂直土压力接近均匀分布；随着填土高度的增大，垂直土压力分布曲线随距明洞中轴线距离的增加呈先减小后稳定的趋势；低压实土的设置使明洞顶虚实土接触附近垂直土压力分布曲线出现突变。研究成果可为沟槽式高填黄土明洞卸载措施的设计和施工提供参考依据。

Unloading model test on open cut tunnels in high filled loess trench

In order to study the variation of vertical earth pressure and soil settlement of the open cut tunnel in high filled loess trench under different unloading measures，the unloading effect in different schemes were analyzed and compared through the indoor model test. The results show that increasing the angle of the filling slope，setting the low compacted soil on the top of the open cut tunnel，laying the geogrid and improving the compression modulus of filling on both sides of the open cut tunnel reduce the earth pressure on the top of open cut tunnel. The increase of slope angle has the best effect. The vertical earth pressure on the top of the open cut tunnel is reduced 20.6% in comparison with the one without the slope. The soil arch effect of low compacted soil and the effect of geogrid reduce further the vertical earth pressure on the top of the open cut tunnel. The vertical earth pressure is almost uniformly distributed when the height of earth filling is low. The vertical earth pressure decreases at first and then becomes stable as the increase of the filling height. The setting of low compacted soil resultes in a jump of the vertical earth pressure near the interface of virtual and compacted soil.