基于固结-渗透联合试验的泥炭土渗透系数变化规律研究

Study on Change Law of Permeability Coefficient of Peat Soil Based on Combined Consolidation-permeability Test

随着我国西南地区高速铁路的快速发展,泥炭土地基的处置需求日益增多。渗透系数影响地基沉降的速率与大小,关乎高速铁路路基施工过程中以及工后的变形大小,但泥炭土固结压缩过程中渗透系数变化规律的研究成果较少。为此,通过固结-渗透联合试验,对大理西湖和昆明两处泥炭土不同取样方向的渗透系数展开研究。试验中,测量不同加载时刻的渗透系数,并结合泥炭土固结三阶段进行分析。研究结果表明:泥炭土的渗透系数具有较为明显的各向异性,随着孔隙比的增大,水平方向的渗透系数k_(h)与垂直方向渗透系数k_(v)的比值k_(h)/k_(v)以指数函数的形式趋近于1;通过分析固结渗透联合试验数据,提出基于初始孔隙比、荷载以及加载时间的渗透系数计算式;无论荷载的大小,渗透系数在主固结阶段下降百分比超过了75%,而在第三固结阶段下降百分比不足3%;泥炭土渗透系数k与固结压缩速率v的比值与时间t具有显著的线性关系。研究可为明确泥炭土固结过程中渗透系数的变化规律、优化高速铁路泥炭土地基沉降计算提供理论参考。

With the rapid development of high-speed railways in southwest China,there is an increasing demand for the disposal of peat soil foundations.Despite the influence of the permeability coefficient on the settlement of foundation and the direct relationship of the coefficient with the deformation of high-speed railway subgrade,there are few research results on the change law of the permeability coefficient during the consolidation loading process of peat soil.Therefore,by measuring the permeability coefficient during the consolidation process,this paper studied the permeability coefficient of peat soil in different sampling directions in the lakeside of Dali West Lake and Kunming.In the test,the permeability coefficients at different loading times were measured,and analyzed in combination with the three stages of peat soil consolidation.The results indicate that the permeability coefficient of peat soil has obvious anisotropy.As the void ratio increases,the ratio k_(h)/k_(v)of the permeability coefficient in the horizontal direction k_(h)to the permeability coefficient in the vertical direction k_(v)approaches 1 with an exponential function.Based on the analysis of the data of the combined consolidation permeability test,the calculation formula of permeability coefficient was proposed based on initial void ratio,load and loading time.By dividing the consolidation of peat soil into three stages,it is proposed that regardless of the level of load,the permeability coefficient decreases by more than 75%in the main consolidation stage,but less than 3%in the third consolidation stage.The ratio of the permeability coefficient k of peat soil to the consolidation compression rate v has a significant linear relationship with time t.The conclusions of this paper provide a basis for clarifying the variation law of permeability coefficient during the consolidation process of peat soil and optimizing the settlement calculation of peat soil foundation of high-speed railway.