Zhang Qishu, Leng Wuming, Zhai Bin, Xu Fang, Dong Junli, Yang Qi
School of Civil Engineering, Central South University, Changsha 410075, China.
National Engineering Laboratory for High Speed Railway Construction, Central South University, Changsha 410075, China.
Materials (Basel). 2021 Sep 30;14(19):5722. doi: 10.3390/ma14195722.
Critical dynamic stress () and accumulative plastic strain () are primary indicators regarding the dynamic stability of unbound granular materials (UGMs). This study aims to seek an effective method to evaluate the dynamic stability of UGMs used in railway subgrades. First, the dynamic characteristics of an UGM used in railway subgrade bed construction were investigated by performing a series of large-scale cyclic triaxial tests, with the results showing that versus cycle number () curves can be categorized into stable, failure, and critical patterns. Grey relational analyses were then established, where the analyzed results demonstrated that the - curve pattern and final accumulative plastic strain () of the stable curves are strongly correlated with the moisture content (), confining pressure (), and dynamic deviator stress (). The analyzed grey relational grades distributed in a narrow range of 0.72 to 0.81, indicating that , , and have similar degrees of importance on determining the - curve patterns and the values of of the UGM. Finally, a data processing method using a back-propagation (BP) neural network is introduced to analyze the test data, and an empirical approach is developed to evaluate the (considering the effects of and ) and (considering the effects of , , and ) of the UGM. The analyzed results illustrated that the developed method can effectively reflect the linear/non-linear relationships of and with respect to and/or . The approximately increases linearly with increasing , and a simple empirical formula is proposed for the . In addition, and its variation rate increase non-linearly with increasing but decrease non-linearly as increases.
临界动应力（）和累积塑性应变（）是关于无结合料粒料（UGMs）动力稳定性的主要指标。本研究旨在寻找一种有效的方法来评估铁路路基中使用的UGMs的动力稳定性。首先，通过进行一系列大型循环三轴试验，研究了用于铁路基床施工的UGM的动力特性，结果表明与循环次数（）的曲线可分为稳定、破坏和临界模式。然后建立了灰色关联分析，分析结果表明稳定曲线的-曲线模式和最终累积塑性应变（）与含水量（）、围压（）和动偏应力（）密切相关。分析得到的灰色关联度分布在0.72至0.81的狭窄范围内，表明、和在确定UGM的-曲线模式和值方面具有相似的重要程度。最后，引入一种使用反向传播（BP）神经网络的数据处理方法来分析试验数据，并开发了一种经验方法来评估UGM的（考虑和的影响）和（考虑、和的影响）。分析结果表明，所开发的方法能够有效地反映和相对于和/或的线性/非线性关系。随的增加近似呈线性增加，并提出了一个关于的简单经验公式。此外，及其变化率随的增加呈非线性增加，但随的增加呈非线性减小。
