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研究生:陳思宏
研究生(外文):Chen, Sze-Hung
論文名稱:黏土層中未襯砌隧道之破壞機制
論文名稱(外文):Failure Mechanism of Unlined Tunnel in Clay
指導教授:李崇正李崇正引用關係
指導教授(外文):Chen Huei-Tsyr, Su Yung-Feng
學位類別:碩士
校院名稱:國立中央大學
系所名稱:土木工程學系
學門:工程學門
學類:土木工程學類
論文種類:學術論文
論文出版年:1996
畢業學年度:84
語文別:中文
論文頁數:2
中文關鍵詞:離心機隧道破壞機制崩潰壓力
外文關鍵詞:CentrifugeTunnelFailure MechanismCollapse Load
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摘 要
在軟弱黏土層中構築隧道,必須在未襯砌階段,提供適當的臨時支撐壓力
,確保施工安全。同時也避免土體大量位移,以維持鄰產之安全與完整。
因此,如何估算維持穩定所需之最小支撐壓力非常重要。這個問題可以藉
由理論或試驗方式解決。使用全尺寸隧道進行觀察,雖然可以得到完整的
資訊,但費用高昂。此外,為了工作人員的安全,進行原型隧道破壞試驗
亦難以執行。
本研究利用縮尺小模型,在安全無慮的狀況下,進行隧道變形與破壞試驗
,並可連續觀察其過程。地工離心機提供縮尺模型之最佳試驗工具。隧道
離心模型試驗可以藉由持續調降隧道內支撐氣壓,直到隧道崩壞,而能連
續且清楚觀察其破壞形態,並進一步瞭解隧道破壞機制。
本研究利用自行設計之試體準備箱,以單向度壓密方式,製作等強度剖面
之黏土試體。進行深徑比(C/D)分別為1與2之二維隧道離心模型試驗。隧
道模型在100g的離心加速度力場中進行試驗,直徑6公分之模型可以模擬
現場直徑6公尺之隧道。利用彈塑性理論分析圓形隧道在半無限域空間中
,隧道周圍土體之應力分佈形態及支撐壓力與隧道變形之互制關係;另外
再進行上、下限分析,求得上限及下限隧道支撐氣壓。利用不同強度剖面
及不同深徑比之隧道離心模型所得結果與理論分析結果比較。本研究釐清
隧道破壞機制,亦證實離心模型試驗為大地工程之另一有利研究工具。
ABSTRACT
If a tunnel is being constructed in soft clay, prior to erection
of a perm-anent lining, it may require temproary support to
provide an acceptable margin of safety for the tunneler and also
to limit ground movements to prevent damage to adjacent
buildings and services. It is therefore important to establish
the minimum pressure necessary for stability. These problems may
be addressedthrough both theory and experiments. Observation of
the behaviourof full-scale tunnel may provide the designer with
considerae insight, but this is costly. Moreover, it is rarely
practicable if conditions near to collapseare approached,
because of the obvious danger.
The geotechnical centrifuge provides the opportunity for
constructing small-scale model tunnels and observing their
deformation and collapse insafety. During a centrifige test, the
supporting pressure is progessively and manually reduced until
collapse occurs. It provides insight into the mechanics of
deforming tunnels and leads to a clearer understanding.
The clay sample consolidated from a slurry in a large
consolidation cell was adopted to prepare the soil bed having a
uniform strength profile. The specified tunnel cover-to-diameter
ratios(C/D) for each experiment were 1 and 2 respectively. The
centrifuge acceleration chosen for the experiment series was
100g ; the model tunnel diameter was 6cm, which means that the
equivalent prototype tunnel is of a diameter 6m. This
investigation presents a stress analysis surrounding a tunnel in
an infinite space by idealizing thclay as an elastic, perfectly
plastic material, and also shows the relation of deformation and
supporting pressure. The supporting pressure which may be
required to maintain stability can be estimated by lower and
upper bound theorems of plasticity. The results of experiments
and theorems can be competed by different values of strength of
the clay and the cover-to-diameter ratio. This research leads to
a clearing understanding of mechanics of tunnel collapse and
proves that the centrifuge isa useful tool for geotenical
engineering.
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