总长568.63米的“八一”隧道有462.63米为基岩段。基岩段岩质为朱罗系上砂溪庙亚组紫红色泥岩夹薄层砂岩,水平倾角4—7度,层理发育。砂岩岩层最厚1.5米,最薄仅几厘米;泥岩岩层无法分辨,石质松,遇水即散。整个岩基段有渗漏水地段210米,占总长的45%;渗漏水严重地段94米,占总长的20%。设计确定岩石坚固系数KP=3-6(比实际偏高),四种衬砌断面毛洞最大跨度14.2米,最大高度7.9米。 The “Bayi” tunnel with a total length of 568.63 meters has 462.63 meters of foundation rock. The bedrock section of the Jurassic system is a sandstone of purplish red mudstone sandstone sandstone on the Juluo-sandstone sub-system, with horizontal dip of 4-7 degrees and bedding development. Sandstone rock thickness of 1.5 meters, the thinnest only a few centimeters; mudstone rock layer can not tell, stone pine, water is scattered. There are 210 meters of seepage water in the whole rock foundation section, accounting for 45% of the total length; 94 meters of serious water leakage, accounting for 20% of the total length. Designed to determine the rock solid coefficient KP = 3-6 (higher than the actual high), the four lining section of the maximum length of 14.2 meters hair hole, the maximum height of 7.9 meters.