白鹤滩柱状节理岩体真三轴模型试验研究

在柱状节理玄武岩工程地质调查、现场精细结构描述等工作基础上，开展了柱状节理玄武岩体的脆性材料模型真三轴物理模拟试验。研究了复合柱状岩体在不同卸荷-加载应力途径下的破裂、破坏机制及不同方向三轴主应力作用下的应力-应变关系及其强度特性；开展的8种不同应力比和6种不同受力方向下各向异性试验结果表明，柱状节理玄武岩体强度、变形特征受三向不等围压和柱状节理特性影响明显，强度变形的各向异性特征显著。试验结果表明，应力比 对试样的强度、变形和破坏模式具有控制作用，随着应力比的变化，试样的极限强度呈现分段特性；较小应力比下试样的变形和破坏模式受应力比和原生节理的共同影响；较大的应力比对试样的变形和破坏模式的影响比原生节理的影响显著；随着应力比的增大，中主应力由约束侧向变形变为主动加载，这一作用的变化影响了极限荷载和破坏模式。

Experimental research of columnar jointed basalt with true triaxial apparatus at Baihetan Hydropower Station

There are many engineering geological problems in the dam foundation; and one new problem is how to evaluate and determine the mechanical properties of the columnar jointed basalt at the dam abutment. Using the true triaxial apparatus is an available measure to study the engineering geological property of the basalt in so compound field environment with high stress conditions and special rock structures. Based on the investigation and analysis of engineering geological condition in situ, a series of physical model tests by brittle material with the true triaxial apparatus were carried out to find out mechanical properties of columnar jointed basalt. The fracture and deformation mechanism of the sample, that is the compound columnar jointed basalt, was studied. Eight different stress ratios( ) are used in the strength test with the true triaxial apparatus; and the results show that the strength and deformation properties of the compound columnar jointed basalt is influenced by the columnar jointed characteristics and the stress ratios. The stress ratios can influence the value of ultimate breaking load of the rock. The test results show that when the stress ratio is less than 3, the stress ratio and the joints control the value of ultimate breaking load and the failure mode. When the stress ratio is higher than 3, the effect of stress ratio is more obvious than that of the joints. With the increase of stress ratio, the effect of intermediate principal stress varies from confinement to load and the ultimate breaking load and the failure mode varies with the change. Six different load models are used during the test; and the results show that the anisotropy of strength and deformation of the basalt is obvious. But if the microfissure distributing widely in the columna is considered, the columnar jointed basalt can be simplified as lateral isotropy.