红砂岩粗粒土具有易破碎性，在动力荷载反复作用下会发生颗粒破碎，导致路基产生明显的工后沉降。针对红砂岩粗粒土颗粒破碎的特点，采用室内动三轴试验仪进行了不同工况下的动力荷载试验，研究了动弹性模量、动弹性应变与粒径大小之间的关系，以及颗粒破碎率与颗粒形状系数变化率的关系。根据试验材料的动力破碎特性，构建了考虑颗粒破碎的累积变形模型，并对模型进行了修正。研究结果表明：颗粒粒径越大，动弹性应变越大，动弹性模量越小；动弹性应变先快速增大最后逐渐趋于稳定，动弹性模量随着加载次数的增加不断减小，土体出现应变软化现象。颗粒形状系数变化率变化趋势与颗粒破碎率变化趋势相似，随着加载次数的增加，形状系数值趋近于1。 此外，所构建的累积变形模型包含了应力状态参数、物理状态参数和拟合参数，能够较好的描述颗粒破碎状态下的红砂岩粗粒土的累积变形趋势。根据试验数据的反算结果，对累积变形模型的拟合参数进行了确定，便于在实际工程应用中对路基变形进行计算。由于室内试验与工程实践现场工况有一定区别，提出了模型修正系数ψ，提高了模型的预测精度。本研究结果可为红砂岩粗粒土路基设计、施工及运营提供理论依据和工程应用基础。
Abstract
Red sandstone coarse-grained soil is fragile, and particle breakage will occur under the repeated action of dynamic load, resulting in obvious post-construction settlement of subgrade. According to the characteristics of particle breakage of red sandstone coarse-grained soil, dynamic load tests under different working conditions were carried out by using a large indoor dynamic triaxial tester, and the relationship between dynamic elastic modulus, dynamic elastic strain and particle size, as well as the relationship between particle breakage rate and the change rate of particle shape coefficient was studied. According to the dynamic breaking characteristics of the materials, a cumulative deformation model considering particle breaking was established and modified. The results show that the larger the particle size, the larger the dynamic elastic strain and the smaller the dynamic elastic modulus. The dynamic elastic strain increases rapidly at first and then tends to be stable. The dynamic elastic modulus decreases with the increase of loading times, and the soil appears strain softening phenomenon. The variation trend of particle shape coefficient is similar to that of particle breakage rate. With the increase of loading times, the shape coefficient value approaches to 1. In addition, the cumulative deformation model includes stress state parameters, physical state parameters and fitting parameters, which can better describe the cumulative deformation trend of coarse-grained red sandstone soil under the condition of particle breakage. According to the inverse computation results of test data, the fitting parameters of the cumulative deformation model are determined, which is convenient to calculate the subgrade deformation in practical engineering application. Due to the difference between the laboratory test and the field condition, the model correction coefficient ψ was proposed, which improves the prediction accuracy. The results of this study can provide theoretical basis and engineering application basis for the design, construction and operation of red sandstone coarse-grained soil subgrade.
关键词
红砂岩 /
粗粒土 /
铁路路基 /
颗粒破碎 /
累积变形模型
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Key words
Red sandstone /
Coarse grained soil /
Railway subgrade /
Particle breakage /
Cumulative deformation model
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