古浪软硬互层边坡崩塌机理研究

Research on Collapse Mechanism of Inter-bedded Soft-hard Strata Slope in Gulang

由泥岩和砂岩互层而构成软硬互层顺层边坡是甘肃省等西北地区分布较多的一种边坡形式,因工程建设需要而进行的削坡往往导致高陡边坡,进而引发崩塌等工程灾害。以甘肃古浪境内G312线界古公路十八里铺水库段典型砂岩和泥岩互层边坡崩塌为背景,通过分析现场崩塌形态与特征,将其归结为大型崩塌和小型崩塌两种类型;通过研究地形地貌特征,认为公路边坡具有"高"和"陡"的特点,为崩塌发育提供临空条件;通过分析气象和水文特征,认为较大的日温差、相对湿度日变化以及层间裂隙水的存在加剧了风化作用,集中降水则是崩塌产生的主要诱发因素;通过研究工程地质和地层结构特征,泥岩和砂岩显著的岩性差异和互层结构为崩塌提供了物质条件。其机理可概括为:干湿循环致泥岩风化、砂岩节理发育;集中降水诱发边坡崩塌。研究成果对西北地区高陡软硬互层边坡崩塌灾害的认识和防治具有参考价值。

The soft-hard strata inter-bedded slope is composed of mudstone and sandstone,and this kind of slope is widely distributed in Gansu and northwest China.Due to the need of construction,the cutting slope often leads to high and steep slope,thus causes the disasters such as collapse.The collapsed highway slope at the section of Shibalipu Reservoir of the G312 line in Gulang,Gansu Province,is a typical mudstone and sandstone inter-bedded slope.By analyzing the shape and characteristics of the collapse,it comes down to the two types,large scale collapse and small collapse.According to the topographic and geomorphic features,the highway slope with ＂high＂and ＂steep＂characteristics provides the free surface for the collapse.Based on the meteorological and hydrological characteristics,it is considered that the large daily temperature difference,large daily relative humidity difference and the interlayer fissure water aggravate the weathering effect,and the concentrated rainfall is the main inducing factor of the collapse.By studying the characteristics of engineering geology and stratum structure,the significant difference of lithology and inter-bedded soft-hard strata provide the material conditions for the collapse.The mechanism can be summarized as follows.The weathering of mudstone and the joint development of sandstone are caused by drying and watering cycles.Slope collapse is induced by concentrated rainfall.The research results have reference value for understanding and preventing the collapse hazard of high steep interbedded soft-hard strata slope in northwest region.