Study of non-symmetric deformation behavior along tunnel wall

• Main Authors: Ni, Tsan-Yao, 倪贊堯
• Other Authors: Ke, Te-Chih
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/12295253604390974780

碩士 === 中原大學 === 土木工程學系 === 88 === The active orogenesis is still proceeding in Taiwan, leading to young topography and complicated geological structures. In order to satisfy the traffic need and balance the development between the east- and west-side, tunnel construction is essential and encouraged. Because of in-situ non-uniform geological conditions, tunnel wall deformation observed is not always symmetric, leading to misleading in the design of excavation and lining. The goal of this thesis is to perform a sensitivity study of various site factors, which really contribute to unsymmetrical phenomenon of tunnel wall deformation. The two-dimensional FLAC code of Version 3.3 is the main analysis tool used in this thesis. The influence factors under investigation include transversely-isotropic elastic mode, ubiquitous joint mode, adjacent slope, undulate topography, surrounding cavity and fault. The plane strain mode, no water condition, small deformation mode, gravity and a circular tunnel section are adopted. The outcomes are presented by the threshold values of certain factors, under which unsymmetrical behavior can not be ignored. Besides, two tunnel sections of New Kuan-Yin Tunnel under construction on the east coast of Taiwan were selected for case study. The results of sensitivity study are summarized as follows. The unsymmetrical behavior of tunnel wall deformation is regarded as significant, and should be considered in lining design, under the following conditions: 1) the dip angle of transversely-isotropic structure plane is between 10 and 80°; 2) the dip angle of ubiquitous joint is between 30 and 85°; 3) the vertical distance between the tunnel wall and slope surface is less than 12 times tunnel diameter; 4) the vertical distance between the tunnel wall and slope toe of undulate topography is less than 0.75 times tunnel diameter; 5) the distance between the tunnel wall and cavity wall is less than 0.6 times tunnel diameter; 6) the vertical distance between the tunnel wall and fault surface is less than one tunnel diameter. Finally, the results of case study indicated that the observed unsymmetrical deformation could be well explained by both of transversely-isotropy of schistosity and one shear band in the field.