高填黄土明洞卸载结构土压力模型试验和数值模拟分析

通过模型试验,研究了高填黄土明洞不同卸载结构的土压力、土体位移随填土高度的变化规律。试验结果表明,边坡的摩擦上提作用、低压实土产生的土拱效应以及土工格栅变形后的"提兜"作用均能够引起明洞洞顶土压力的减小,其中,低压实土+土工格栅卸载结构卸载率最大;卸载结构不同,明洞顶平面土压力分布规律不同,SY0和SY1在1倍明洞宽度范围内的土压力近似为梯形分布,大于1倍明洞宽度的土压力基本保持不变,近似为均匀分布,SY2~SY5明洞中轴线到0.75倍明洞宽度处,土压力基本保持一致,大于0.75倍明洞宽度的土压力呈先增大后减小的趋势。随后对试验过程进行了数值模拟分析,两者结果较为吻合。最后探讨了土拱效应形成机理,从而为高填明洞土压力卸载技术的进一步研究提供科学依据。

Model tests and numerical simulations of earth pressure for unloading structures of high fill open cut tunnel

The influence laws of earth pressure and soil displacement for different unloading structures of high fill loess open cut tunnel with the increase of filling height are studied through the model tests. The results show that the friction resistance of slope, the soil arch effect of low compacted soil and the geogrid effect can reduce the earth pressure of the open cut tunnel, and the unloading rate of low compacted soil and geogrid is the largest. Under different unloading structures, the distribution law of earth pressure on the top of the open cut tunnel is also different. Within the scope of 1 times the width, the earth pressures of SY0 and SY1 are approximately in trapezoidal distribution. Within the scope of over 1 times the width, the earth pressures keep unchanged, and are approximately in uniform distribution. The earth pressures are basically consistent in the scope of the central axis to 0.75 times the width, and they increase at first and decrease later within the scope of over 0.75 times the width. Based on the numerical simulation analysis, the test and numerical results are basically identical. Finally, the formation mechanism of soil arch effect is discussed so as to provide a scientific evidence for further researches on the unloading technology of the earth pressure of the high fill open cut tunnel.