| Summary: | 碩士 === 國立臺北科技大學 === 土木與防災研究所 === 96 === Title：The Case Study Of Tunnel Excavation For Un-Consolidated Sandstone
In Northern Taiwan Pages：123
School：National Taipei University of Technology
Department：Institute of Civil and Prevention Engineering
Time：November, 2007 Degree：Master
Researcher：Wu-Feng Kuo Advisor：Kuang-Yen Cheng
Keyword: Soft-Rock, Un-consolidated, Soften, Collapse, Back analysis
There’s no specific definition of un-consolidated rock in engineering geological scope in general. It can be correlated to extremely weak rock as specificed by ISRM with characteristic strength less than 25 MPa.
A tunnel (Named as G Tunnel hereafter) which discussed is located at northern hill and ridge area of northern Taiwan, driven through Dananwan Formation soft rock, composite by unconsolidated interbreeded sandstone and mudstone, as the research object of this paper is to analyze the possibility of Demolition Model while encountering low-strength, poorly consolidate capability, and easily soften material during the process of excavation in CⅡ(S) rock mass, wihch defineed as the weight percentage of loose sandstone is more than 50%, by Public Construction Commission Rock Mass Classification System (PCCR-System). It further provides the construction filed to have some general idea to design and construct weak rock in tunnels and decrease the risk during construction period.
As result of Feedback analysis from this article, the material parameter of CⅡ(S) is E=125~275 MPa；C=50~70 KPa；φ=35°, This main damageed model is collapse during tunnel excavation. The possibilities of collapse location could be top arch and sidewall. But the finished supporting arches are rarely damaged or heavily deformed by unstable soil stratum.
The failure mechanism is controlled by bonding different particle size material specially the fines.Therefore, the key ways of keeping the tunnel excavation under control are shown below:
a). Eexact pre-survey the ground water distribution and correlated action for drainage,
dewatering method and efficient.
b). Strengthen the hardness of rockmass by fast consolidate grouting policy.
c). Reduce the disturbance during excavation to meet the fast-support scope of tunnel.
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