考虑二期荷载的高填明洞加筋减载土压力计算

随着城市建设的迅速发展，既有高填明洞填土顶面将不可避免地出现新增结构物等二期荷载的情况。为了明确明洞回填完成后新增二期荷载对其顶部垂直土压力的影响，在已有明洞减载结构土压力计算公式的基础上，利用土体沉降弹性理论计算公式建立了土工格栅变形与土体沉降变形的关系，并考虑二期荷载作用，进一步完善了高填明洞减载前后的洞顶垂直土压力计算公式。建立数值分析模型，将数值分析结果与文中公式计算结果进行了对比。结果表明：公式计算与数值分析结果较为接近，表现出相同的规律性；有无减载措施对明洞回填土压力影响较大，填土越高，减载越显著，实际作用在明洞顶土压力越小。新增二期荷载作用下的明洞顶垂直土压力计算，应考虑其对土体沉降变形的影响，而非简单叠加。

Calculation of the earth pressure on the high fill open-cut tunnel with load-reduction reinforcement considering secondary loading

With the rapid development of urban construction, new structures inevitably induce the secondary loading on the top of existing high fill open-cut tunnel. In order to characterize the influence of the new secondary loading due to backfilling on vertical earth pressure on the top of high fill open-cut tunnel, the relationship between the geogrid deformation and the soil settlement is established by using the elastic theory of soil settlement, based on the formulation of earth pressure on the load reduction structure. Meanwhile, the effect of the secondary loading is considered. The method for calculating vertical earth pressure on the top of high fill open-cut tunnel before and after the load reduction is further improved. Numerical analysis models are established, and the numerical results are compared with the results obtained from the proposed procedure in this paper. The results show that the theoretical results are close to the numerical results, with the same regularity. The load reduction measure has a great impact on the backfill earth pressure on open-cut tunnel. The higher the fill, the more significant the effect of load reduction, and the smaller the practical earth pressure on the top of open cut tunnel. The calculation of vertical earth pressure on the top of open-cut tunnel under the secondary loading should consider the influence of soil settlement rather than a simple superposition.