铁路台阶式加筋土挡墙潜在破裂面特征模型试验

Model test on potential failure surface characteristics of railway stepped reinforced soil retaining wall

铁路台阶式加筋土挡墙的设计方法尚不成熟,现有设计方法不能满足铁路边坡工程实践的需求。潜在破裂面的确定是加筋土挡墙设计的关键,但现行规范仅对10m以下单级加筋土挡墙的潜在破裂面有了明确的规定。为了研究台阶式加筋土挡墙在铁路荷载作用下潜在破裂面的特征,设计了1:4的大比例尺二级台阶式加筋土挡墙室内模型试验,以周期性加卸载的方式模拟铁路荷载,通过监测墙面水平位移、墙顶沉降及土工格栅筋带变形,分析确定潜在破裂面的位置和形状。试验结果表明:Ⅰ级墙(下级墙)潜在破裂面形状与现行规范中的0.3H法破裂面类似,但位置更深,且下部破裂面更缓,表明潜在不稳定范围更大;Ⅱ级墙(上级墙)潜在破裂面形状与朗肯主动破裂面基本一致,但并未从Ⅱ级墙坡脚剪出,而是内移刺入Ⅰ级墙体;研究结果可为铁路台阶式加筋土挡墙的设计提供理论参考。

The current design methods for the railway stepped reinforced soil retaining walls are still immature,which fails to satisfy the requirement of railway slope reinforcement practice.For the design of reinforced soil retaining walls,accurate determination of the potential failure surface is the key issue.However,though current specifications clearly address the shape and location of the potential failure surface,they limit their use only in single walls with a height of no more than 10 m.This paper attempts to identify the characteristics of potential failure surfaces in stepped reinforced soil retaining walls under railway loads by the use of model test.The model was designed with a large scale of 1:4 and the railway load was stimulated by a specific cyclic surcharge load.The shape and location of the potential failure surface were determined by the comprehensive analysis of the slope surface lateral displacements,vertical settlements at the slope crust and strains of the geogrid at different investigation points.The result illustrated:the potential failure surface in the lower stage wall is similar to that given by the'0.3 H'method but has a deeper location and a more gentle inclination of the bottom part,which indicate a larger potential unstable area;while the shape of the potential failure surface in the upper stage wall is generally similar to the Ranking’s active rupture,however it thrusts into the lower stage wall rather than thrusts out from the foot of the upper stage wall.The test results and conclusions drawn in this study can provide theoretical reference for the design of railway stepped reinforced soil retaining wall.