沥青混凝土心墙与过渡层变形协调性及防渗的影响研究

Deformation coordination and seepage prevention of asphalt concrete core-wall and transition layers

采用三维有限元法对云南省某沥青混凝土心墙均质坝进行了心墙与两侧过渡层变形协调性的数值模拟分析,研究心墙的厚度对坝体防渗影响的变化规律。计算中坝体和心墙的本构模型采用邓肯张E-B模型,对不同厚度的心墙分别进行了模拟计算,并对比其相互之间的变形协调规律及心墙的防渗效果。计算结果显示,心墙厚度在0.3 m、0.4 m和0.5 m条件下,大部分水平位移满足变形协调性,顺河向水平位移值随着心墙厚度的增加而变大,拱效应越明显,说明对心墙水平位移越不利。心墙与过渡层的沉降随着高程的增加而变大,并且随着心墙厚度的增加,沉降的最大值随之减小。相对两侧的过渡层而言,心墙上部沉降小,底部沉降大,整个心墙在高度方向上有"被拉伸"的现象,这就为心墙产生拱效应提供了必要条件。心墙以受压应力为主,通过验算,并未发生水力劈裂破坏。坝体加入沥青混凝土心墙后,浸润线明显降低,防渗效果好,并且渗流量随着心墙厚度的增加而减小。

This study has conducted numerical simulations using a three-dimensional finite element method and an analysis on the deformation coordination of core-wall and the transition layers on its both sides for an earth dam with a homogeneous asphalt concrete core-wall in Yunnan province, focusing on core-wall anti-seepage effect and its trend of variation with core-wall thickness. A constitutive model for simulations of the dam body and core-wall was based on the Duncan E-B model. For the cases of different core-wall thicknesses, simulation data were analyzed and the deformation coordination and core-wall anti-seepage effects were compared. Results show that with core-wall thicknesses of 0.3, 0.4 and 0.5 m, most of the horizontal displacements can be well coordinated, but the stream-wise horizontal displacement is increased with an increasing core-wall thickness, resulting in an obvious arch effect in late stage, which is an adverse condition to horizontal deformation. As for vertical deformation, the subsidence of core-wall and transition layers becomes larger as elevation increases, and an increase in core-wall thickness will reduce the peak subsidence. Relative to the transition layers, subsidence of the upper core-wall is smaller while the lower part greater, so that a phenomenon that the whole core-wall has been ＂stretched＂ vertically can be observed. This provides a favorable condition to enhance the core-wall arching effect. Since the core-wall is dominated by compressive stress according to the calculations, hydraulic fracturing damage will be impossible. For a dam body imbedded with an asphalt concrete core-wall, its saturated surfaces are lowered significantly and its anti-seepage effects become better; the seepage flow decreases with an increasing core-wall thickness.