开展了不同剪应力水平下土体剪切位移的时间效应特征分析，提出了随剪应力水平增加，土体变形状态对应呈现快速稳定、缓慢稳定、缓慢破坏和快速破坏4种演化类别。通过粉质黏土蠕变直剪试验，对不同压实度下与剪应力水平相对应的土体剪切位移时间效应的4种状态类别进行了研究。采用幂函数拟合剪切位移时间历程试验数据，将幂次值作为划分变形状态类别的理论判据，基于幂次值与剪应力水平对应关系的曲线形态特征，得到了土体4种变形状态对应的3个剪应力水平阈值，提出了基于Coulomb强度公式表达的相应变形状态强度参数及其与极限状态强度参数的关系式。针对高速铁路无砟轨道路基工后沉降控制须满足毫米级变形的特殊要求，明确了应将土体变形时间效应控制于快速稳定状态作为路堤填料选择及压实标准的设计原则和技术条件。所得成果对构建高速铁路路基土工结构变形状态控制设计技术提供了理论和试验依据。

The time-effect characteristics of shear displacement of soil under different shear stress levels are analyzed. Four states of soil deformation are identified as the shear stress level increases, namely, fast steady, slowly steady, slowly breaking and fast breaking states. Based on the creep direct shear test of silty clay with different degrees of compaction, these four states are investigated. The test data are fitted by a power function which serves as the classification criterion of deformation state. Based on the shapes of shear stress level-power curve, three shear stress level thresholds corresponding to these four states are obtained. An expression between the state strength parameter and the ultimate strength parameter is developed based on the Coulomb strength equation. The post-construction settlement of subgrade in high-speed railway is of a magnitude of millimetre. It is found that the choice of embankment fill material and the compaction standard must meet the control principle and technology condition of fast steady state. The research results provide theoretical and experimental bases for controlling deformation states of soil structures in high-speed railway subgrade.