Evaluation of the Auxiliary Measures on Softrock

• Main Author: 陳太平
• Other Authors: 鄭光炎
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/18096581107349881205

碩士 === 國立臺北科技大學 === 土木與防災技術研究所 === 91 === Tunnels have mainly been constructed using the New Austria Tunneling Method (NATM) recently. This method takes advantage of the strength of rock to share stresses generated after excavation in association with applying appropriate shotcrete, rockbolts, wire mesh etc. Up to date, NATM is mostly applied on hard rock stratum and many tunnels have been constructed using NATM in Taiwan. Where gravel, sandy, silty or clayey soil etc. softrock strata are encountered, appropriate auxiliary methods can be used for strengthening the NATM, namely Auxiliary New Austria Tunneling Method (A-NATM). Traffic in Taiwan becomes more congested each day. Since the island is mountainous, tunnel construction is increasing, including tunnel excavation by A-NATM. Due to the young age rock stratum in the west of Taiwan, tunnel construction civil works through softrock stratum is inevitable. It is important to apply A-NATM effectively to stabilize the excavation face during tunnel construction. Since softrock tunnel contains various soils with many characteristics, this study classified the soils into 2 types, cohesive and non-cohesive, collected information of instrumentation and excavation records obtained from 8 kinds of A-NATM measures including temporary invert, rockbolt, cement grouting, foot rockbolt, spread footing (extended outward), foot steel pipe, spread footing (extended inward) and self-drilling rockbolt that were used for construction in Lin-Kou and Hu-Kou softrock tunnels, subsequently complied the information, made summary tables and plotted figures of trend regarding soil type and its relative deformation for studying the application timing and effectiveness of A-NATM. According to the study that temporary invert is more suitable for construction in the case of soil stratum that tends to cohesive silty or silty/clayey alternative, self-drill rock bolt is more suitable to cohesive silty/clayey alternative and cement grouting, spread footing (extended outward) and foot steel pipe are more suitable for that tends to non-cohesive dense sand soil.