Hydrogeological and engineering geological characteristics of Mangbang Formation soft rocks in Mangshi basin, western Yunnan Province: a case study of the Mangjiu coal mine

The Mangshi basin is a continental sedimentary basins formed on the tectonic background of episode II of Himalaya Movement, with the primary filling substance being the river-lacustrine sedimentary system of Mangbang Formation. According to mining and drilling data, the engineering geological consolidation classification of Mangbang Formation is semi-soft rock, which can be divided into sandstone-sandy conglomerate soft rock group, siltstone weak rock group and carbonaceous mudstone-coal weak rock group. The coal seam is of low ash (15%-25%), low sulfur (0.5%-2.5%), semi-dark-half light brown type, and there exists a certain degree of self-ignition, The strength of the rock groups are in order of Psand-gravel