|Abstract: ||岩體之強度因節理之存在而降低,並呈 現高度之異向性。本文分別由物理模型實驗及 數學模式分析兩方面,來探討節理岩體於單軸 壓力下之破壞行為。於實驗方面,首先依材料 模擬相似律,以砂、石膏及水混合物灌製板狀 模擬岩石材料(30cm*25cm*5cm),再利用自製之 雙刃節理截斷器截取不同形狀之人工張裂節理 小岩塊。然後堆疊成含不同組數、方向節理之 三向度岩體模型,以從事壓力試驗探討其於單 軸壓力下之破壞模式與強度。於數學模式方面 ,基於能量觀點提出一三向度岩體組成模式,可 考慮不同方向、組數、間距及力學行為之節理 ,對岩體強度之影響。由研究結果知:單軸壓力下岩體之主要破壞模式有:(1)沿完整岩石破壞 ;(2)沿節理滑動破壞;(3)混合破壞模式。而其 強度隨著節理方向與主應力之夾角不同,呈現 高度之異向性。同時由實驗結果與數學模式預 測值相較,發現兩者趨勢甚為吻合。|
The strength of a jointed rock mass strongly depends on the orientation, number, spacing, and mechanical behavior of joints. In this investigation, the uniaxial strength of three-dimensional jointed rock masses with multiple skew joint sets is studied using experimental and analytical approaches. In experimental study, a mixture of plaster, sand, and water is used based on the similitude law of models. Moreover, a double-blade guillotine is used to produce artificial extension joint sets with specified orientation and spacing from rock model plates (30cm*25cm*5cm). Thus a series of small jointed blocks can be assembled to form a three-dimensional physical model of jointed rock masses . With these models, the experimental study on the failure modes and the strength of rock masses under uniaxial loading condition can be performed. In the analytical study, a versatile three-dimensional constitutive law based on the energy concept is proposed to model an assemblage of intact rock blocks separated by structural weak planes. It is capable of handling any number of joint sets with any orientation and the anisotropic strength for rock masses with non-othogonal sets of jointed can be predicted. From the results of this investigation, the failure mechanism of a jointed rock masses can be simply divided into three types: (1) fracture through intact material, (2) sliding along joint planes, and (3) mixed modes of types (1) and (2). Through the experimental study, it is found that the strength of the jointed models is highly anisotropic. According to the comparison between experimental and analytical results, good agreement is also obtained.