岩石试样的杨氏模量与围压的关系

EFFECT OF CONFINING PRESSURE ON THE YOUNG'S MODULUS OF ROCK SPECIMEN

岩石种类繁多,变形历史复杂,围压对杨氏模量的影响规律尚缺乏明确的结论。由于岩样轴向压缩的应力-应变曲线并非直线,杨氏模量的数值依赖于确定方法。与割线模量相比,平均模量是应力-应变曲线中近似直线部分的斜率,受试验条件的影响较小,表示了应力与应变之间的变化关系。利用伺服试验机和文献上的试验结果得到了不同岩石的平均模量与围压的关系。宏观均匀致密的岩样或仅含有局部缺陷的岩样,杨氏模量与围压无关。从风化岩石和软弱岩层钻孔取芯得到的岩样,通常含有分布的裂隙,增大围压可以增大裂隙面之间的摩擦力,抑制剪切滑移的产生,从而提高杨氏模量。杨氏模量随围压的变化体现了岩样内部的损伤状态。

Rocks are different in their structure, mineral particles and deforming history, and the effect of confining pressure on Young's modulus is not understood clearly. The Young's modulus is various with the definition method as the stress-strain curve is not a direct line. The secant modulus from zero stress can not describe the deforming property of the practical rock mass. But the average modulus, which is determined from the average slope of the more-or-less straight-line portion of the axial stress-strain curve, is less influenced by the experimental conditions. Experimental results from servo-controlled testing machine and public references are used to study the relation between confining pressure and Young's modulus for various rocks. Confining pressure does not influence Young's modulus of rock with homogeneous material in macrostructure or with local flaw only. But specimen from weathered rock or drilled in weak rock strata usually has distributed fissures. The friction in the fissures will increase with confining pressure, which reduces the shear slide between fissures and makes Young's modulus higher as well. The relation between Young's modulus and confining pressure shows the state of rock damage.