軟弱砂岩力學行為與其岩象分析研究(II)

Abstract

延續前期研究結果，本研究以麓山帶 軟弱砂岩為樣本空間，探討微組構性質與 岩石力學特性之關係。首先將砂岩岩象影 像資料數位化，配合電腦影像辨識分析， 以精確定量化求出岩石之礦物組成因子及 顆粒幾何因子，建立客觀的判斷標準，改 善以往由於人工計數，可能流於個人主觀 或無法定量之缺點。在獲得砂岩之微組構 因子及由基本物性實驗求得物性因子後， 採用多變量階段迴歸分析逐一釐清影響岩 石乾燥單壓強度(UCS)及濕乾強度比(R)之 物性及微組構因子，由分析結果可知，影 響乾燥單壓強度之主要因子為孔隙率，次 要因子為顆粒面積比(GAR)，兩者皆與單壓 強度呈負相關；影響濕乾強度比之主要因 子為顆粒面積比，次要因子為孔隙率，前 者與濕乾強度比呈正相關，後者則與濕乾 強度比負相關。依據迴歸分析結果，本研 究提出一套砂岩力學特性分類，以孔隙率 及顆粒面積比為分類指標，在考慮單壓強 度及濕乾強度比兩項力學性質下，將砂岩 力學特性分為8 類。藉由此分類方法初步 評估砂岩力學性質，可獲致不錯之結果。

In this research, the correlation of mechanical behavior and microstructure (and composition) of sandstone was accessed. Sandstone samples were subjected to petrographic analysis and nine parameters were obtained. Based on the stepwise multiple regression results, mathematical functions were developed for estimating the uniaxial compression strength (UCS) and the ratio (R) of saturated strength to dry strength from the petrographic and petrophysical indexes. The research revealed that the major influence factor of UCS is porosity and the minor factor is grain area ratio (GAR). Otherwise, the major influence factor of R is GAR and the minor factor is porosity. According to the results, a mechanical classification of foothill sandstone was proposed, and sandstones were classified into eight kinds based on two index, porosity and GAR.