滇藏铁路滇西北段蒙脱石化蚀变岩的工程地质研究

Engineering geological research on altered rocks in the area of NW Yunnan along Yunnan-Tibet Railway line

滇西北地区是中国西南地区最重要的构造成矿带之一,与其相伴出现的蚀变岩常引起一系列工程问题。野外地质调查和室内测试表明:滇藏铁路滇西北段出露的多为蒙脱石化蚀变岩带,蚀变岩的黏土矿物组成绝大多数都是单矿物的蒙脱石,导致该地区的蚀变岩既是强度极低的软岩,又是典型的膨胀岩。蒙脱石化蚀变岩的发育分布与三江地区热液矿床的分布具有相似的规律。本文以滇藏铁路滇西北段为例,阐述了蒙脱石化蚀变岩的发育特征和工程特性,并针对隧道建设中由蚀变岩引起的工程问题提出了相应的防治对策。

The NW Yunnan area is one of the famous tectonic-metallogenic regions in southwestern China, and a series of engineering problems always occur because of the existence of altered rocks formed by hydrothermal action. It was shown by field investigation and lab tests that the types of altered rocks were mostly those of montmorillonitization, and the altered clay mineral was mainly pure montmoriUanite, which rendered the altered rock both soft and expansive. The altered rocks had a similar development with the hydrothermal ore deposits in the area of three paralleled rivers. Taking examples from the NW Yunnan area along the Yunnan-Tibet Railway line, the geological characteristics and engineering properties of the altered rocks were discussed, and a series of control measures were put forward for the engineering problems caused by them.