摘要
煤是一种特殊的岩石,随机分布着大量裂隙和弱面,从而使得不同尺寸煤样力学特性差异很大。基于一组不同直径(D=61,101,146和300 mm)煤样常规三轴压缩试验结果,对不同直径煤样强度参数确定方法作了探讨。研究表明,煤样强度不仅是围压的函数,而且是直径的函数;随着直径的增加,煤样弹性模量近似呈负冪函数关系降低,但这种关系受围压影响较小;煤样泊松比与直径以及围压关系不大,基本上均在0.21～0.25之间。通过考察广义Hoek-Brown准则参数与直径之间的函数关系,可以近似预测所研究范围内(0≤σ3≤10 MPa及61 mm≤D≤300 mm)不同直径和不同围压条件下煤样的强度。利用广义Hoek-Brown准则强度参数,基于切线法理论,获得了不同直径煤样的黏聚力和内摩擦角,然而切线法理论存在着在个别试验点上逼近很好但整体逼近很差的不足之处。对于一种已经被评价适合广义Hoek-Brown准则的岩石材料,利用泛函分析中的最佳逼近多项式理论(一次式),提出了一个新的评判准则。采用该评判准则,更为精确地确定了不同直径煤样的黏聚力和内摩擦角,避免了切线法理论的不足之处。最后讨论了直径对煤样黏聚力和内摩擦角的影响。研究结果对于岩土工程设计和数值计算时岩样黏聚力和内摩擦角的选取具有参考价值。
Coal is a special kind of rock. There are plenty of fissures and weak faces distributed randomly over the coal samples, resulting in great difference of mechanical behavior of coal samples with different sizes. Based on a group of experimental results of coal samples with different diameters （D=61, 101, 146 and 300 mm） under conventional triaxial compression obtained by Medhurst and Brown （1998）, the confirmation methods for strength parameters of coal samples with different diameters are discussed. The results show that the strength of coal samples is the function of the confining pressure and the diameter. With the increase of the diameter, the elastic modulus of coal samples decreases by means of a negative power function, nearly independent of the confining pressure. The Poisson＇s ratio of coal samples is not related to the diameter and confining pressure and is 0.21~0.25. By considering the relation between the generalized Hoek-Brown criterion parameters and the diameter, the strength of coal samples with different diameters and confining pressures can be predicted approximately in the range of 0≤σ3≤10 MPa and 61 mm≤D≤300 mm. In accordance with the generalized Hoek-Brown criterion parameters, the cohesion and internal friction angle of coal samples with different diameters are obtained by the tangent method theory, which has the shortage of good approximation in a certain test point but bad approximation on the whole. For a kind of rock evaluated as a generalized Hoek-Brown material, a new evaluation criterion is put forward by adopting the optimal approximation polynomial theory （optimal approximation first equation） in functional analysis. It is employed to confirm more precisely the cohesion and internal friction angle of coal samples with different diameters. Finally, the effect of the diameter on the cohesion and internal friction angle of coal samples is investigated. The research results provide the reference value for the choice of the cohesion and internal friction angle of rock samples in the process of geo-engineering design and numerical simulation.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2010年第6期881-891,共11页
Chinese Journal of Geotechnical Engineering
基金
国家自然科学基金项目(50709008)
中国矿业大学人才引进资助项目
关键词
岩石力学
煤样
强度
直径
黏聚力
内摩擦角
准则
rock mechanics
coal sample
strength
diameter
cohesion
internal friction angle
criterion
