岩石隧道襯砌水壓荷載簡化分析模式之探討

A study of simple analyzing method for the water pressure on rock tunnel lining

吳學強(Syue-Ciang Wu)

指導教授 ： 丁原智 ； 王泰典

國立臺北科技大學/工程學院/資源工程研究所/碩士(2010年)

摘要

目前有關隧道混凝土襯砌之受力問題至今尚無一定論，但此受力問題往往成為隧道設計上之焦點問題。然而隧道工程若跨越至含水覆蓋層時，其隧道混凝土襯砌所承受之力，將不僅僅只有岩覆荷載力，亦須考慮到襯砌上之水壓力。一般隧道襯砌承受之水壓分為外水壓及內水壓，其中，內水壓僅在部份水利隧道需加以考慮，本文主要針對外水壓力這個部份做一探討。若將整個隧道分析做一現地試驗，其試驗方式實為困難且所需經費亦相當高，因此本研究所使用之數值模擬程式為有限差分連續體分析之套裝軟體FLAC，以給予地下水位面分析開挖隧道襯砌上所承受之壓力水頭。
本研究係以一維定水頭模型來探討靜水壓與作用至圓形隧道支撐上水壓之關係，此模型之滲流方向與層面(圍岩、噴凝土、混凝土襯砌)呈垂直關係。襯砌上水壓力理論解之推導部份亦遵循於達西定律。而本研究之滲透係數(K)為圍岩滲透係數(Kr)與噴凝土滲透係數 (Ks)兩項的函數關係，其噴凝土滲透係數(Ks)可借由假設得知，流量(q)便能利用簡化分析獲得，當簡化模型架設另一層混凝土襯砌時將得到不同的流量(q)，因此襯砌之滲透性亦隨之改變，其襯砌上所受的力亦不相同，當一維定水頭模型確立時，便可運用至二維隧道開挖模型上。
而本文最後利用FLAC數值模擬所得之結果，試著探討出更為合理化之襯砌水壓力。

關鍵字

隧道 ； 混凝土襯砌 ； 水壓力

並列摘要

At present, the evaluation of loading on concrete lining still could not reach a unique consensus until now, but they are always key issues in tunnel design. However, if the tunnel crosses the aquiferous overburden, the force that the tunnel concrete lining is exposed to will not only be rock covered loading, but it must also take into account the water pressure on tunnel lining. The water pressure that tunnel lining bears is usually divided into external water pressure and internal water pressure, of which only part of the water pressure inside the hydraulic tunnel needs to be taken into consideration. This paper aims at studying the parts related to external water pressure. It will be very difficult and cost very much in case of doing an in situ experiment according to the analysis of tunnel. Hence the software FLAC which is a package of finite difference continuum analysis is used in this research as the numerous simulation program in order to give an underground water table for analyzing the water pressure endured by the lining on the tunnel when doing excavation.
This research makes a discussion on the relation between the hydrostatic pre- ssure and the water pressure on the lining of circular tunnel by using an one dimen- sional constant head model. The flow direction of this model is perpendicular to the bedding(wall rock, shotcrete, concrete lining). The derivation part of Analytic solu- tions of the water pressure on the lining goes with Darcy’s Law as well. The per- meability coefficient (K) in this research is a functional relation between the wall rock permeability coefficient (Kr) and the shotcrete permeability coefficient (Ks) which can be assumed by hypothesis with the flow (q) being capable to be known by simple analysis. The flow (q) can be known when the simplified model builds another layer of concrete lining, hence the permeability of lining changes with it and the pressure endured by the lining is different as well. This one dimensional constant model can be applied to two dimensional tunnel excavation model when confirmed.
The last work in this paper is to make the result of FLAC numerical simulation, trying to find another reasonable method of assessing the water pressure on the lining.

並列關鍵字

tunnel ； concrete lining ； water pressure

參考文獻

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