英文篇名
MULTIPLE-STAGE TRIAXIAL TEST FOR ROCK
作者
李德河
摘要
近年來由於國內社會、經濟的快速變遷,人口不斷增加,土地需求量高漲,促成大量之山坡地開發。同時為了滿足用電、用水需求年年暴增之勢,核能發電廠、大型水壩等乃應運而生。
在從事此等巨大土木工程時常須以岩盤為其施工處理的對象,而尋求岩石之力學特性則為進行工程設計與施工所不可欠缺的工作之一。為了獲得必要的資料,在工地中,吾人常做多種之岩盤試驗,而在實驗室中,直接剪力試驗及三軸壓縮試驗則是最常被運用的試驗方法。
以往在從事岩石三軸壓縮試驗時,是將試體設置在三軸室(Triaxial cell)中,先加以適當的圍壓(Confining pressure)後,以具有足夠剛性之載重裝置給予試體軸向壓力,直到試體被壓壞為止。因此以傳統之三軸壓縮試驗方法僅能由一個岩石試體求得一組包括最大強度(Peak Strength)及殘留強度(Residual Strength)各一之強度數據。所以若要明確了解岩石之力學特性包括Peak Strength Criteria及Residual Strength Criteria,則必須使用三個以上的岩石試體方可。
由於岩石試體間常存有明顯的材質變異。使得由數個試體所求得之強度值無法簡單地歸納其Criteria來,因而所需之試體數及試驗次數更形增加。同時,由於地形、地質等條件之限制,在工地中要大量採取具有相同應力條件的試體亦頗為困難。
所以由經濟的觀點或是由節省試驗時間、提高試驗的準確性等觀點上看,將傳統三軸壓縮試驗法中加以改良、擴充,以尋求用較少的岩石試體而可求得岩石的強度規準(Strength Criteria)之試驗方法實有其必要。
本文的目的乃是介紹一些已經被實際應用於岩石強度試驗的改良三軸壓縮試驗法。由於此等方法均使用單一岩石試體以求取在多種圍壓作用下岩石的強度值,所以統稱這些方法為「岩石的多段式三軸壓縮試驗法」。
英文摘要
Kovari and Tisa(1975)have developed a test method, called "Multiple Failure State Triaxial Test", which is capable of deducing more sets of strength parameters from one specimen under different confining pressures. It has been proved that this new method is a suitable alternative to the traditional triaxial test when a dry and hard rock specimen such as marble or sandstone is used. However, their suitability for saturated porous soft rock is not known. Hence, a series of triaxial tests with similar method were conducted to determine the mechanical characteristics of saturated soft rocks under various kinds of confining pressure using only one rock specimen. This test might be called "Multiple Stage Triaxial Test Method" for soft rock, or MST for short.
In this paper, the MST for hard rock is presented, and the process of developing the MST for soft rock is also discussed.