软黏土流变等效特性与土结构状态破坏相互作用机理研究

The long-term stability design of the geotechnical engineering in soft clay areas needs to consider the time-dependent behavior of soil. The key issues of the project on the time-dependent behavior of soft clay are the development of constitutive model based on experiments and the determination of the model parameters. Present study aims to investigate the interactive mechanism between the equivalent time-dependent behavior and the destructuration of soil structure and improve current time-dependent model. 1D creep, strain-rate and stress relaxation tests are conducted on reconstituted and intact structural soft clay using constant stress and constant strain oedometer apparatus, based on which the relationship between creep strain and rate, the time-dependency of consolidation pressure, stress relaxation and rate and destructuration state of clays are discussed. Based on all test results and current time-dependent theories, an equivalence model between creep, rate-dependency and stress relaxation with incorporation the effects of destructuration is proposed. By implementing the model to FEM, an elasto-visco-plastic model is developed with the equivalent input of the time-dependent parameters coupled with the destructuration of clay. This study is methodical in its experimental, analytical and numerical characterization of the effects of destructuration of clay and it can reveal the rules between the time-dependent and destructuration of clay and clarify the equivalence of different time-dependent behaviors. The proposed research also provide new ideas and theoretical basis in the analysis of the time-dependent problems of geotechnical engineering in soft clay area.

软黏土地区岩土工程的长期稳定性设计需要考虑土的流变特性。软黏土流变特性研究的关键是基于试验开发流变模型以及确定模型相关参数。本项目拟开展软黏土流变等效特性与土结构状态破坏相互作用机理研究，改进现有的流变模型。采用常规和恒速率固结仪，对重塑及天然结构性软黏土进行一维蠕变、加载速率和应力松弛试验，分析蠕变及其速率、固结压力及其速率、应力松弛及其速率与土结构状态破坏的相互关系；基于上述试验及规律，结合当前流变理论，提出考虑结构状态破坏的蠕变、加载速率和应力松弛等效方程；通过把等效方程嵌入有限元程序，建立流变参数等效输入的考虑结构状态破坏的软黏土流变模型。本研究展示软黏土流变等效特性与土结构状态破坏相互影响的试验、理论及数值等系列成果，揭示软黏土流变特性与土结构破坏相互作用规律以及阐明其等效性，为软黏土地区岩土工程流变问题的分析与计算提供新思路和理论依据。

软黏土地区岩土工程的长期稳定性设计需要考虑土的流变特性。软黏土强结构性的特性要求流变模型以及模型相关流变参数需要考虑土体结构性的影响。本项目针对软黏土蠕变、加载速率和应力松弛特性与土结构耦合机理问题，结合室内试验，提出了基于蠕变的土结构状态指标，此结构状态指标与原状和重塑土的蠕变系数相关，能够直观反映土体蠕变及演化特性；此外，试验结果表明：蠕变系数与土结构状态指标相关，而加载速率系数和应力松弛系数与土的结构状态指标关系不大。结合已建立的基于重塑土的流变参数等效性公式，建立了考虑土体结构性的软黏土流变参数等效方程。通过比较数值与试验结果，评价了流变参数等效方程的合理性。提出考虑结构状态破坏的软黏土流变参数等效方程，并明确相关流变参数的确定方法。通过嵌入流变参数等效方程至现有ANICRREP流变模型，结合有限元计算软件Plaxis，实现了流变模型与比奥固结理论的耦合，最终形成了考虑流变参数等效输入的考虑结构状态破坏的可用于边界值问题计算的分析模型。应用模型对软土地区Murro路堤的长期稳定性变形进行了预测分析。本研究展示了软黏土流变等效特性与土结构状态破坏相互影响的试验、理论及数值等系列成果，揭示了软黏土流变特性与土结构破坏相互作用规律以及阐明了其等效性，为软黏土地区岩土工程流变问题的分析与计算提供新思路和理论依据。