岩樣熱傳導試驗及深岩層地溫推估模式

Abstract

現代許多岩石工程均涉及極深之覆岩狀況，工程中可能遭遇的岩溫也 隨之增高。著眼於地溫推估的重要，本研究中進行了一系列的岩樣熱傳導 試驗並建立一套以最佳化方法為基礎之地溫推估模式。 本研究採用分 割棒法進行岩樣熱傳導試驗。試驗結果顯示板岩及硬頁岩的熱傳導係數約 略隨傾角的增加而增大。板岩及變質砂岩的熱傳導係數約隨溫度的增加而 降低。由於本試驗之岩樣數目有限，本試驗結果顯示板岩及變質砂岩的熱 傳導係數與取樣深度並無明顯的關係。 在本研究中，利用有限元素法 及最佳化方法來決定邊界熱流的方式建立一套以逆 分析模組以推估地溫 。在此計算模組中，僅考慮因二向度的熱傳導行為所引致的地溫分佈情形 。經過計算結果驗證本計算模組確實合理可行。同時經數值分析結果顯示 ，熱傳導係數對地溫分佈的影響至為重大，且異向性對地溫分佈的影響不 容忽視。本研究中的計算結果亦顯示地溫梯度分佈將因不同的地形而有差 別。且在本模式中，當存在鑽井的地溫量測誤差時會對地溫推估造成影響 。 Engineering projects such as deep tunnel under high mountain may involve deep site conditions.As the depth at considered site increases,the underground temperaturetends to elevate.This study aims to experimentally study the thermalconductivity of underground rock specimens and to develop a reasonable methodology for estimating underground rock temperature in great depth. This study carries out a series of experimental work for determining thermal conductivity of rock spcimens of slate and argillite.Experimetal results show that the thermal conductivity roughly increases with the increasing temperature.Due to the limited data,the relation between thermal conductivity and depth is not conclusive. This study proposed a methodology of modular anaysis for estimating undergroundrock temperature.The methodology of proposed anaysis involves finite-element methodand nonlinear optimization method.The proposed analysis assumes that the distribution of underground temperature is solely due to two-dimension thermal conduction.The proposed methodology is verified and proved to be applicable.Numerical experimentsshow that the anisotropy of thermal conductivity and the round surface profile alsoaffect the distributions of temperature and thermal gradient.This study also discussesthe error source for underground temperature estimation.