軟弱岩石孔內試驗

Abstract

軟弱岩石普遍具有固結差、膠結不良、遇水軟化之特性。由於岩層取樣過程對岩樣本身之組織構造可能已造成破壞，而且軟弱岩石中可能存在裂縫、互層與節理，造成取回之岩樣施作室內試驗時，試驗結果十分混亂，很難歸納出其力學性質與工程參數，所以量取極軟弱岩層性質比較理想的方法是使用現地試驗方法，因其可以量測缺陷對整個岩體的影響，而且可避免取樣擾動之問題。 本研究針對黃安斌與房正國(1999)所研發可施作鑽孔千斤頂試驗、鑽孔剪力試驗、及孔底平板載重試驗之多功能孔內試驗儀，先進行防水功能與某些設計之改良，再施作試驗決定軟弱岩石之現地橫向與縱向的應力-應變-強度之關係，再配合鄭孟雄(1999)研發之軟岩用高壓傍壓儀、現地孔內波速量測試驗、室內超音波試驗與三軸試驗所得到之工程參數進行比對、評估多功能孔內試驗儀所得到之試驗成果、並瞭解其效能。 本論文敘述軟弱岩石之特性、現地試驗、多功能孔內試驗儀系統、標定程序、試驗操作程序、結果與分析、以及結論與建議。

Soft rocks have the characteristics of weak and poorly cementation. While soaking them in water, the strength will be reduced. The typical rock coring process has a tendency to damage the structure that originally existed in situ. Besides that, soft rocks are likely to contain defects, such as fissures, bedding and joints. Accordingly, the laboratory tests always result in disorderly outputs. Thus, it is hard to obtain the correlation between strength properties and engineering parameters. In situ test is a better method to avoid disturbance and to get engineering properties of soft rocks. A medium sized, versatile in situ testing device specifically for soft rock has been developed by Huang and Fang (1999). The new device, referred to as the multiple-purpose Borehole Testing Device (BTD), is capable of performing lateral jacking test, direct shear test and plate bearing test at the bottom of a borehole. This research modified the former BTD and a series of tests were performed in soft rocks to determine the radial and longitudinal stress- strain relationships. Test results were complied and compared with those engineering properties derived from highly pressuremeter test, in situ P-S logging test, laboratory ultrasonic test, and triaxial test. This thesis introduces the characteristics of soft rocks, in situ tests, describes features of BTD, presents the available data obtained from BTD, and discusses their interpretations.