偏压固结下高铁软土地基的分阶段加载变形特性

Deformation characteristics of high-speed railway soft soil foundations under staged loading with bias consolidation

摘要

高铁软土地基的变形演化过程受多重因素的综合影响,现有研究多基于连续振动条件下的动三轴试验探讨相关因素的作用机制,而对高铁实际运营过程中振动与停歇交替所形成的分阶段加载特征关注不足。针对上述问题,通过系统的循环动三轴试验,分析了分阶段加载条件下有效平均主应力、初始静偏应力及振动阶段次数对上海原状饱和软黏土变形特性的影响规律。研究结果表明:土体埋深及其对应的有效平均主应力水平对间歇阶段固结排水过程具有显著制约作用,随着埋深增加,间歇阶段固结排水行为对外部加载条件变化的敏感性逐渐降低;初始静偏应力通过诱导初始剪应力并促进固结排水的双重机制,对土体变形演化产生重要影响;振动阶段的振动次数显著影响间歇阶段固结过程中的累积应变增量,但对固结排水速率的调控作用相对有限。在分阶段加载条件下,系统认识各因素对软黏土变形特性的影响机制,研究成果可为高铁软土地基长期变形分析与安全运营评估提供参考。

Abstract

The deformation evolution of high-speed railway soft subgrades is influenced by the combined effects of multiple factors. Existing studies have mostly investigated these mechanisms based on cyclic triaxial tests under continuous vibration conditions, while insufficient attention has been paid to the staged loading characteristics formed by the alternation of vibration and rest during actual high-speed railway operation. To address the above issues, this study conducted systematic cyclic triaxial tests to examine the influence patterns of effective mean principal stress, initial static deviator stress, and the number of vibration cycles during the vibration stage on the deformation characteristics of undisturbed saturated soft clay from Shanghai under staged loading conditions. The results indicate that soil burial depth and its corresponding level of effective mean principal stress exert a significant constraining effect on the consolidation drainage process during the intermittent stage, and with increasing burial depth, the sensitivity of intermittent-stage consolidation drainage behavior to changes in external loading conditions gradually diminishes. Initial static deviator stress has an important influence on soil deformation evolution through a dual mechanism by inducing initial shear stress and enhancing consolidation drainage. In addition, the number of vibration cycles during the vibration stage significantly affects the cumulative strain increment during the consolidation process in the intermittent stage, whereas its influence on the consolidation drainage rate is relatively limited. Under staged loading conditions, a systematic understanding of the mechanisms by which various factors influence the deformation behavior of soft clay can provide a reference for long-term deformation analysis and safe operation assessment of high-speed railway soft subgrades.

关键词

高铁软土地基 / 分阶段加载 / 间歇固结排水 / 土体变形

Key words

high-speed railway soft soil foundation / staged loading / intermittent consolidation drainage / soil deformation

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基金资助

国家自然科学基金面上项目(52378381)

陕西省教育厅一般专项科学研究计划项目(24JK0528)