Geological Exploration and Route Selection in Karst Area of Yunnan- Guizhou Plateau of Chengdu- Guiyang Railway Zhang Yu-jun and Yue Zhi-qin China Railway ErYuan Engineering Group Co.ltd, Chengdu,China
[email protected] ABSTRACT Sichuan Yibin City to Guizhou Bijie City section of Chengdu- Guiyang Railway lies in the transitional zone from the southern margin of the Sichuan Basin to the northwestern of Yunnan- Guizhou Plateau. In the transitional zone, karst and karst water are generally controlled by a variety of factors, including lithology, structure, geomorphology, meteorological and water network. With the variation of natural geological conditions, the development degree of karst, the development pattern of karst , karst water distribution and enrichment degree of the karst water change accordingly. Through comprehensive analysis of the factors affecting karst, the study area can be divided into three karst hydrogeological units including the fold zone in the edge of Sichuan Basin, Sichuan Basin - transitional Yunnan-Guizhou Plateau, Yunnan-Guizhou Plateau.Since the end of the Cretaceous, the crust of the study area has experienced two big uplift and three leveled, three ancient karst erosion surface formed. Since the Pleistocene, the earth crust has experienced a number of intermittent rises that result in one to six terraces in the valley and the formation of corresponding multi-cave. The lithologic is the important factor that controls the development of karst; the Qixia Formation and Maokou Formation of Permian are most developed karst in fifteen karst horizons, and the underground river system are in the largest scale, then follows the Triassic; in alternating or interbedded layers of the non-karst and karst, the features of Karst is bedded, and hydraulic connection between layers is weak; The accumulation of karst water is mainly affected by the karst development degree, landform, lithology and geological structures.