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小浪底水利枢纽南岸引水隧洞Ⅱ标段工程,断面为圆形,洞径为4.5,4.7,5.1m3种。该标段岩层构造简单,呈单叙构造,产状倾向SE,倾用5°～8°,主要为T~1_1T~(3-1)_1地层,由砂岩夹页岩和粘土岩组成。岩石致密坚硬,新鲜完整,力学强度高,围岩稳定性好,围岸类型为Ⅱ类,岩石为Ⅸ级。根据岩石特征,经多次论证与反复实验,最后确定采用超前导洞开挖法。导洞开挖:导洞尺寸为2.5m×2.5m,采用平行直孔掏槽,掏槽孔为五孔梅花状,孔深2.4m;辅助孔深2.3m,间距为0.5～0.9m。炮孔布置见图1.导洞炮孔装药结构见表1.导洞
Xiaolangdi Water Control Project South Island diversion tunnel Ⅱ standard section project, the section is circular, with a diameter of 4.5,4.7,5.1 m3 species. The segment has a simple structure and a single Syrian tectonic tectonic setting. Its tectonic orientation is SE and its dip is between 5 ° and 8 °. It is mainly composed of T_1_1T_ (3-1) _1 stratum and is composed of sandstone intercalated with shale and clay rock. Rock is dense and hard, fresh and complete, high mechanical strength, good stability of surrounding rock, the type of shore Ⅱ, rock Ⅸ level. According to rock characteristics, after repeated demonstration and repeated experiments, and finally determine the use of advanced leading tunnel excavation method. Guide hole excavation: The guide hole size is 2.5m × 2.5m, with parallel straight hole cut, cut hole for five holes plum, hole depth 2.4m; auxiliary hole depth 2.3m, spacing of 0.5 ~ 0.9m. Blast hole arrangement shown in Figure 1. Guided hole charge structure shown in Table 1. Guidance hole