基于颗粒流的高填黄土减载明洞土拱效应分析

实际工程表明,在高填方明洞顶部铺设EPS板可以明显降低洞顶竖向土压力,然而,铺设EPS板会将明洞上方的土体荷载向其两侧土体转移,导致其侧墙所受水平土压力及弯矩增大。为了进一步减小明洞受力,提出一种新型减载明洞体系,利用颗粒流软件建立相应数值模型,从竖向、水平土压力、颗粒竖向位移、颗粒间接触力和孔隙率等细观层面研究该减载明洞的荷载传递机制。此外,基于该减载体系,分析EPS板距拱顶位置、宽度和填土压实度对明洞土拱效应的影响。研究结果表明:该减载体系可以扩大土拱效应的影响范围,同时减小洞顶与洞侧土压力;土拱效应的发展与洞顶土体孔隙率的变化相关,孔隙率随EPS板距拱顶距离的增加逐渐减小,土拱效应逐渐减弱,洞顶土压力逐渐增大;随EPS板宽度的增加先增大后减小,当EPS板宽度W=1.5D时,孔隙率达到最大值,土拱效应最强,洞顶荷载分布最少;填土压实度越大,柱土应力比越大,洞顶土压力越小。

Analysis on soil arching for unloading structure of high-filled cut-and-cover tunnel based on particle flow simulation

The practical engineering shows that laying EPS board on the top of high-filled cut-and-cover tunnel can obviously reduce the vertical earth pressure. However, it will transfer the soil load on the top of high-filled cut-and-cover tunnel to its two sides, resulting in the increase of horizontal earth pressure and bending moment. In order to further reduce the stress around the cut-and-cover tunnel, a new type of unloading structure system was proposed in this paper, and the software Meso-scale Particle Flow Code was used to establish the corresponding numerical model. The influence laws of soil arching for unloading structure system were studied from the mesoscopic level of vertical soil pressure, vertical displacement of particles and contact force chain between particles. In addition, based on this system, the influence of location and the width of EPS, the compaction degree of the filled soil on the soil arching was analyzed. It is shown that this system can expand the influence range of soil arching and reduce the earth pressure at the top and side of the cut-and-cover tunnel. The development of soil arching is related to the change of the porosity of soil on the roof. The porosity decreases with the increase of the distance between EPS plate and the top of cut-and-cover tunnel, the soil arching weakens and the soil pressure on the roof increases. As the width of EPS board increases, it first increases and then decreases. When the width of EPS board W=1.5 D, the porosity reaches the maximum. The soil arching is the strongest, and the load on the top of cut-and-cover tunnel distribution is the least. The greater the compactness of the filling soil is, the greater the pillar-soil stress ratio is, and the smaller the earth pressure of the roof is.