| Summary: | 碩士 === 國立海洋大學 === 河海工程學系碩士在職專班 === 91 === In recent years, it is inevitable for the engineering works to reach their sites to mountain region, as a number of big projects of public works in Taiwan are being impelled, such that the importance of tunnel engineering becomes pronounced from day to day, and new records of tunnel length and diameter are created. Therefore, under the demands for high quality of engineering technique as day by day shaft engineering works are getting as one of major key which is the important subject of a long tunnel.
Taipei-Ilan Expressway is a 31km east-west alignment in length to connect Taipei and Ilan with a group of tunnels among which Pinglin Tunnel is the longest tunnel 12.9km in length. Due to collision effects of plate tectonics, slightly metamorphic sedimentary rock formations of the Hsuehshen Range were folded and faulted seriously to become several fold belts and fault structures across the alignment. Therefore, geology along the tunnel alignment is rather complicated.
There are three sets of vertical ventilation shaft located at about the same interval on the Pilot Tunnel of the Pinglin Tunnel. Diameters of the shafts, excepting the shaft N0.2 with 6.5m in diameter, are all 6m. The depths of them are ranged from 250m to 500m. Each set is composed of one for fresh-air and one for exhausted-air at 50m apart.
Construction methods of the shafts are quite different from one another under the effects of various advances of the pilot tunneling through the shaft bottom beneath the tunnel crown level, and on variation of construction conditions and based on rock formations of the shafts whether competent or not to be suitable for construction stability. For Shaft NO.1 is located in a monocline of the south limb of the Yingtzulai Syncline, and the Pilot Tunnel advances far beyond the shaft base, a mixing construction methord by raise boring alternating with down reaming of pilot hole is adopted. Shaft NO.2 is located in the north limb of the Taotiaotzu Syncline. The shaft excavation by classical down sink method has been accomplished in early 2000, for the rock masses are competent and with low permealility. The Shaft No.3 is sited in sandstone formation of the Szelong Formation in Eocene. The shaft excavation by classical methord is adopted.
Rock formation of the shaft No.3 is Szelong Sandstone in which rock masses are fractured and high permeable with large amount of groundwater. Under these conditions, grouting treatment has to be routinly performed to keep excavation continue. After grouting treatment with L.W. in short stage in the exhausted-air shaft is completely performed, and down sink excavation then follows. The excavation process has been accomplished in August, 2001. Below elevation 377m of the fresh-air shaft after grouting treatment with B.C. in long stage is done, excavation by down sink nethod follows and accomplishes in September, 2001.
This study paper concerning permeability treatment methods in the Shaft No.3 of the Pinglin Tunnel in Taipei-Ilan Express way is taken for example to elucidate geology characteristics and treatment processes. Detail analyses of the effects of both grouting treatment methords are offered for the exhausted-air shaft with shore-stage L.W. grouting and the fresh-air shaft with long-stage B.C. grouting, respectively. In addition, a comparison of the comtrast on excavation rates between both fore-mentioned methods is done for the purpose to offer some ideas on permeability treatment during construction in future design stage.
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