洞庭湖砂纹淤泥质土一维固结蠕变模型研究

One-dimensional consolidation creep model for sandy grain muddy soil of Dongting Lake

利用一维固结蠕变试验研究洞庭湖砂纹淤泥质土的蠕变特征,建立了适用于描述洞庭湖砂纹淤泥质土应力-应变-时间关系的经验蠕变模型。研究结果表明,轴向应变ε与时间t在双对数坐标系中呈良好的线性递增关系。随着固结应力的增加,lnε-lnt关系曲线的斜率显著减小,且相邻两级荷载作用下lnε-lnt关系曲线的间距逐渐变短。在高应力水平下,lnε-lnt关系曲线趋于水平,同时曲线斜率减小的速率明显降低。双曲线函数比指数函数更为适合描述洞庭湖砂纹淤泥质土的应变-应力关系,将Singh-Mitchell模型中的应变-应力关系修正为双曲线型比较符合工程实际。发现lnε-lnt关系曲线的斜率与固结应力呈双曲线函数关系。在此基础上,建立了反映应力水平影响、适用于描述洞庭湖砂纹淤泥质土蠕变特性的5参数修正Singh-Mitchell模型。

In this study, one-dimensional consolidation creep test was conducted to study the consolidation creep characteristics of the sandy grain muddy soil of Dongting Lake, and an empirical creep model suitable for describing the stress-strain-time relationship of the sandy grain muddy soil of Dongting Lake was established based on the test results. The results show that there is a good linear increasing relationship between axial strain ε and time t in double logarithmic coordinate system. In addition, with the increase of consolidation stress, the slope of lnε-lnt relationship curve decreases significantly, and the distance between lnε-lnt relationship curves becomes shorter under the action of two adjacent loads. Under high stress levels, the lnε-lnt relationship curve tends to be horizontal, and the decrease rate of the slope of the curve is significantly reduced. Moreover, hyperbolic function is more suitable than exponential function to describe the stress-strain relationship of the sandy grain muddy soil of Dongting Lake, and it is more in line with engineering practice to modify the strain-stress relationship in Singh-Mitchell model to hyperbolic relationship. It is found that the slope of the lnε-lnt relationship curve has a hyperbolic function relationship with the consolidation stress. On this basis, a modified Singh-Mitchell model with five parameters reflecting the influence of stress level and suitable for describing the creep characteristics of the sandy grain muddy soil of Dongting Lake is established.