桂东南泥盆系莲花山组泥岩膨胀性研究

Swelling property of mudstone of the Devonian Lianhuashan Formation in southeast Guangxi

泥岩的膨胀性对边坡稳定性及其他岩土工程有重要影响。桂东南中部岑溪市区一带发育泥盆系莲花山组泥岩,主要呈小范围分布于剥蚀-溶蚀垄丘谷地地貌区低丘地带。为查明该区泥岩是否具膨胀性,对出露于山坡地带的泥岩开展了常规调查、钻探、野外试验、室内土工试验、X射线衍射等研究,厘定了泥岩的宏观特征和物理力学性质;采用宏观初判—物理力学指标定量初判—高斯过程定量详判的综合评价方法对泥岩膨胀性进行研究,选取的物理力学指标为效蒙脱石含量、<2μm的胶粒成分含量、液限、塑限指数和胀缩总率,并给出了泥岩膨胀性定量判别标准。研究区泥岩的这5个指标值分别为22%~33%、20%~33%、46.8%~78.0%、24.1~42.9、1.3%~5.2%,经综合判断,该泥岩具中等—强膨胀性。

The swellability of mudstone has important influence on slope stability and other geotechnical engineering.Lianhuashan Formation of the Devonian is developed in Cenxi City,central of southeast Guangxi.It is mainly distributed in a small scale in the low hill area of the stripped and dissolved ridges and valleys geomorphologic area.In order to find out the dilatability of the mudstone in this area,this study has carried out geological mapping,drilling,field test,laboratory geotechnical test and X-ray diffraction analysis to determine the macro-characteristics and physical and mechanical properties of the mudstone.The swelling property of mudstone is studied by the comprehensive evaluation method of macroscopic preliminary judgment—physical and mechanical indexes quantitative initial judgment—Gaussian process quantitative detailed judgment.The physical and mechanical indexes are selected as effective montmorillonite content,<2μm colloidal content,liquid limit,plastic index and total swelling and shrinkage ratio,and the quantitative criterion of swelling property is given.The five indexes of mudstone in the study area are 22%-33%,20%-33%,46.8%-78.0%,24.1-42.9 and 1.3%-5.2%,respectively.It is concluded that the mudstone in the study area has moderate to strong swellability.