复合土工膜封闭特殊土路基动态性能模型试验研究

Model Experimental Study on Dynamic Performance of Special Soil Subgrade Reinforced with Composite Geomembrane Seal Layer

为了分析复合土工膜封闭基床底层特殊土对有砟轨道特殊土路基的保护效果,建立了2组有砟轨道特殊土路基足尺试验模型,研究了在有无复合土工膜封闭特殊土基床底层的条件下,浸水前后有砟轨道特殊土路基试验模型的动态性能.试验结果表明:在同等加载频率和等级条件下,浸水后无布组试验模型振动状态比有布组更剧烈;在未浸水循环动力荷载作用下,当加载次数达到8万次后,有布组和无布组试验模型累积变形均逐渐趋于稳定;在浸水循环动力荷载作用下,无布组累积变形持续增大,而有布组累积变形逐渐趋于稳定,当加载140万次后,无布组基床底层顶面特殊土含水量和地基系数K30值分别增加了41%和降低了39%,有布组基本无变化;采用复合土工膜封闭特殊土基床底层,可有效阻截地表水下渗,防止基床底层特殊土填料浸水软化,使有砟轨道特殊土路基在循环荷载作用下具有良好的长期动力稳定性.

To analyze the protective effect of a composite geomembrane seal layer on special soil subgrades, two full-scale models of ballast track-special soil subgrade were developed. In this study, the dynamic performance of ballast track-special soil subgrades with and without a composite geomembrane seal layer were investigated under both soaked and unsoaked conditions. The test results show that the vibration in the model without a composite geomembrane seal layer is more severe than the vibration in the model with a composite geomembrane seal layer for the same loading frequency and level. Under cyclic loading in unsoaked conditions, the accumulative settlement of the models with and without a composite geomembrane seal layer tends to stabilize at cyclic loading greater than 80,000 cycles. Under cyclic loading in soaked conditions, the accumulative settlement of the model without a composite geomembrane seal layer continually increases, while the accumulative settlement of the model with a composite geomembrane seal layer gradually stabilizes. When the cyclic loading reaches 1,400,000 cycles, the moisture content of the special soil is increased by 41 % , while the ^ 3 〇 value at the top of the bottom layer of the subgrade is reduced by 39% in the model without a composite geomembrane seal layer. However, the moisture content of the special soil and ^30 values for the model with a composite geomembrane seal layer remain basically unchanged. The composite geomembrane used for protecting the special soil of a subgrade bed can effectively intercept water seeping into the subgrade bottom of a bed filled with special soil, which can prevent the special soil from softening. Therefore, the ballast track-special soil subgrade demonstrates favorable long-term dynamic stability when subjected to cyclic loading.