ISSN 1000-3665 CN 11-2202/P

    细粒含量对土工格栅-砾性土界面剪切特性的影响分析

    Effect of fine particle content on shear characteristics of geogrid-reinforced gravelly soil

    • 摘要: 加筋砾性土路基长期服役后受细粒侵入影响,筋土界面受力性能易发生劣化,目前细粒污染筋土界面的相关研究较少。为了研究细粒含量对砾性土填料剪切性能的影响,利用室内大型直剪仪开展系列不同细粒含量的加筋砾性土直剪试验,分析四种细粒含量(0%、10%、20%、30%)、三种法向应力(40,60,80 kPa)对土工格栅-砾性土界面剪切特性的影响,并建立了界面剪切膨胀系数的经验公式。结果表明:(1)加筋砾性土直剪试验的剪应力-剪切位移曲线均为应力软化型,随着细粒含量的增加,峰值剪切强度与剪切强度指标呈现出先增加后减小的趋势;(2)级配良好砾性土颗粒间的咬合力较强,宏观上表现为似黏聚力较大;(3)剪胀性曲线表现为相对剪缩—相对剪胀—相对剪缩阶段,相对剪胀量最大值的出现存在滞后现象,最大剪胀角与峰值剪切强度存在对应关系;(4)利用剪胀系数模型发现细粒含量、法向应力越小,界面剪胀性越强。研究成果可为公路工程的强度设计与劣化防护提供理论指导。

       

      Abstract: Over prolonged service periods, reinforced gravel soil subgrades are susceptible to deterioration in interfacial mechanical properties due to the intrusion of fine particles. However, few studies focus on the interface of fine-grained polluted soil. To study the effect of fine particle content on the shear performance of gravelly soil, a series of direct shear tests of reinforced gravelly soil with different fine particle contents were carried out. The impacts of four different fine particle contents (0%, 10%, 20%, 30%) and three normal stresses (40, 60, 80 kPa) on the shear characteristics of the geogrid-gravel soil interface were analyzed, and the empirical formula of interfacial shear expansion coefficient was established. Results indicate that the shear stress-displacement curves of the reinforced gravelly soil direct shear tests are all of the stress softening type. With the increase in the fine particle content, parameters of peak strength and shear strength show an initial increase followed by a decrease trend. The particle interlocking force of well graded gravel soil is strong, which manifests as a high apparent cohesion in macroscopical. The dilatancy curve shows relative shear contraction, relative dilatancy, and relative shear contraction stages, and the occurrence of the maximum value of relative shear dilatation lags behind. The maximum dilation angle is closely associated with the peak shear strength. Through the dilation coefficient model, it is found that the smaller the fine particle content and normal stress are, the stronger the interfacial dilation is. This study can provide theoretical guidance for strength design and degradation protection of highway engineering.

       

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