滇池北岸泥炭土工程特性垂向变化规律研究

Study on vertical variation law of engineering properties of peat soil in the north shore of Dian Lake

本文较为系统地分析了滇池北岸泥炭土形成的地质背景,对其空间展布及垂向工程特性进行了归纳总结。研究发现,滇池北岸泥炭土的形成与区域地质构造、区域水系和沉积环境等密切相关,工程性质较差;滇池北岸地区100m深度范围内揭露的泥炭土自上而下可分为五层,状态依次为:软塑—流塑、可塑、可塑—硬塑、硬塑、硬塑—坚硬;滇池泥炭土的物理力学性质变化随分布深度的增加呈现一定的规律性,天然含水率与天然孔隙比逐渐减小,干密度逐渐增大,有机质含量逐渐增加,压缩系数、压缩指数逐渐减小且呈收敛趋势,各指标与深度呈现乘幂或指数函数关系。高压固结试验表明,高应力(3200kPa)状态时的孔隙比e约为初始孔隙比e;的0.369倍;与一般软土相比,滇池北岸泥炭土的抗剪强度整体偏高,但粘聚力c值小,而内摩擦角φ偏大。

The geological background of the formation of peat soil in north shore of Dian Lake is analyzed systematically, and its spatial distribution and vertical characteristics are summarized in this paper. The research shows that the formation of peat soil is closely related to regional geological structure, regional water system and sedimentary environment, and the engineering properties of the peat soil are poor. The peat soil exposed within 100 m depth in the north shore of Dian Lake can be divided into five layers from top to bottom, and the statuses are in the orders of soft plastic to flow plastic, plastic, plastic to hard plastic, hard plastic, hard plastic to stiffness. As the depth of distribution increases, water content and void ratio decrease gradually, while dry density and organic matter content increase. It also shows that as the depth of distribution increases, the compression coefficient and compression index gradually decrease and tend to convergence. The relationship between each index and distribution depth is power or exponential function. The high pressure consolidation tests show that the void ratio(e) at high stress(3200 kPa) is about 0.369 times of the initial void ratio(e;). Compared with common soft soil, the shear strength of peat soil in the north shore of Dian Lake is higher on the whole, while it has smaller cohesion(c) and larger internal friction angle(φ).