闽西地区典型煤系土的工程性质分析

Analysis of Engineering Properties of Typical Coal-measure Soils in Western Fujian

为揭示闽西地区典型煤系土工程特性,以龙岩东环高速公路沿线分布的典型煤系土为例,进行大量室内试验,分析煤系土基本工程性质、耐崩解性以及干湿/冻融循环下土样强度指标变化规律等。结果表明:闽西地区煤系土具有塑性指数高、干密度大、压缩系数大等特点。矿物成分为白云母、石英、高岭石,属于中压缩性土、低液限粉质黏土。击实过程中煤系土具有显著颗粒破碎现象。煤系土颗粒间黏结力较低,遇水较易崩解。压实度相同煤系土,其含水率越高越容易被压缩。黏聚力和内摩擦角均随压实度增大而增大,随含水率增大而减小。压实度与含水率对煤系土黏聚力影响大于内摩擦角。干湿循环4次或冻融循环5次后,其压缩强度与抗剪强度趋于稳定,土样基本无裂隙存在。煤系土样孔隙比均随着循环次数、含水率、压实度增加不断减小;黏聚力随着循环次数增加而增大,而内摩擦角呈相反趋势。

To reveal the engineering characteristics of typical coal-measure soils in western Fujian, a typical coal-measure soils distributed along the Longyan East Ring Expressway was taken as an example, a large number of laboratory tests were carried out to analyze the basic engineering properties, disintegration resistance and dry/wet/freeze properties of coal-measure soils. The change law of soil strength index under melting cycle, etc. The results show that the coal-measure soil in western Fujian has the characteristics of high plastic index, high dry density and high compressibility. The mineral composition is muscovite, quartz and kaolinite, which belongs to medium compressibility soil and low liquid limit silty clay. During the compaction process, coal-measure soil has obvious particle breakage phenomenon. Coal-measure soil has low cohesion between particles, and is easier to disintegrate when exposed to water. Coal-measure soil with the same compaction degree, the higher the moisture content, the easier it is to be compressed. The cohesion force and the internal friction angle both increased with the increase of the compaction degree and decreased with the increase of the water content. The effect of compaction and moisture content on the cohesion of coal-measure soil is greater than that of the internal friction angle. After 4 dry-wetting cycles or 5 freeze-thaw cycles, the compressive strength and shear strength tend to be stable, and the soil samples basically have no cracks. The void ratio of coal-measure soil samples decreased continuously with the increase of cycle times, water content and compaction degree;cohesion increased with the increase of cycle times, while the internal friction angle showed an opposite trend.