以熱探針法量測大地材料熱傳導係數之適用性

The study of measuring the thermal conductivity of geotechnical materials with thermal probe method.

張家銘(Chia-Min Chang)

指導教授 ： 田永銘

國立中央大學/工學院/土木工程學系/碩士(2006年)

摘要

熱探針量測法為量測熱傳導係數方法之一，其具有完整理論基礎及使用上的方便性，在實驗室及現地量測中被廣泛應用。本文針對熱探針量測法使用上可能造成誤差之處(鑽孔界面、導熱泥填充、試體尺寸等問題)逐一探討研究，以實驗結果配合統計分析，嘗試建立一套標準之量測步驟。
實驗結果顯示，在熱探針直接埋入試體條件下，具有最好的量測結果；而鑽孔後會造成量測值下降3%~7%，隨淨空值愈大，量測值變異性也隨之增加，因此當岩石在鑽孔條件下量測時，建議縮小淨空值與重覆量測可獲得較準確之量測值。
另就導熱泥使用、電壓輸入量、試體尺寸等問題做系列實驗，由實驗結果建議，導熱泥使用熱傳導係數3W/mK；電壓輸入量9~15Volt；試體寬徑比12.5以上，可得到穩定且準確之量測值。
大地材料量測結果可知，於類岩材料中，熱傳係數值與波速具有相當高之相關係數；但在天然岩石中，超音波量測可反映出岩石孔隙率多寡，但對石英含量高且多孔隙之岩石，則有過大的誤差產生。故超音波在熱傳導係數應用上，應配合岩石礦物組成分析；橫向等向性岩石中，波速與熱傳導係數皆會受到與層面夾角不同而有所變化，二者間關係仍需更多試驗來證明之。

關鍵字

熱傳導係數 ； 超音波速 ； 熱探針量測法

並列摘要

Thermal probe method is one of the ways to measure thermal conductivity which are applied comprehensively in laboratory and in-situ measurement for the complete rationale and convenience in uses. In this article, some factors, including the clearance between the thermal probe and drilled hole, type of thermal grease, and the relative size of the specimen, that influence the quality of thermal conductivity measurement with thermal probe are investigated. Standard measuring procedures by the implementation of test result and statistical analysis are prepared.
The experimental result showed that method with thermal probe directly buried inside the specimen delivers the best result. However, the value of thermal conductivity will be dropped 3%~7% with the traditional drilled hole, and the variability of result would dominate as the clearance increased. Reducing the clearance and repeating measurement are suggested in order to obtain the more accurate test results.
On the suggestions for the thermal grease uses, voltage input value and relative size of the specimen, experimental result shows that using thermal grease with 3W/mK, keeping the value of voltage input at 9~15Volt, and the aspect ratio of the specimen up to 12.5, delivers the stable and accurate test value.
For the geotechnical materials, the thermal conductivity has the best correlation with P-wave velocity in artificial rocks. As for isotropic rocks, the P-wave velocity can reflect the quantity of the rock porosity, but may produce oversized erroneous in rock with rich quartz content and porous. Thus the P-wave velocity waves might cooperate with rock-forming minerals to establish the relationship between thermal conductivity and P-wave velocity. However, in transversely isotropic rock, the wave velocity and thermal conductivity vary with the inclined angle of the bedding plane. Further research on the relationship between thermal conductivity and P-wave velocity is suggested.

並列關鍵字

thermal conductivity ； thermal probe method ； P-wave velocity

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