一种确定各向异性单轴抗压强度的经验公式

An empirical equation to estimate uniaxial compressive strength for anisotropic rocks

岩石的单轴抗压强度可以通过相对简单且经济的方法直接测试得到,在岩土工程领域应用十分广泛。提出了一种确定岩石各向异性单轴抗压强度的经验公式。通过该经验公式对砂岩、千枚岩、板岩和页岩的各向异性单轴抗压强度数据进行了拟合。采用决定系数R^2、相对误差D_p和平均绝对相对误差AAREP这3种统计参数评价经验式的预测能力,结果表明,预测的单轴抗压强度与试验值吻合较好。基于包含274个各向异性单轴抗压强度的数据库,通过统计分析评价了经验公式的预测能力,并与3种常用方法的预测能力进行了对比。统计分析表明,仅有3个方位角(β分别为0°、30°和90°)的试验数据可用时,提出的经验式也能够很好地预测各向异性单轴抗压强度。

Uniaxial compressive strength of rocks is widely used in geotechnical engineering,as it can be directly estimated using relatively straightforward and cost-effective methods.In the present study,an empirical equation to predict the uniaxial compressive strength for anisotropic rocks is developed.The proposed equation has been used to fit the data for four types of anisotropic rocks,i.e.sandstone,phyllite,slate and shale.Three different statistical parameters（regression R-square value R^2,relative error D_p and average absolute relative error AAREP） have been used to assess the predictive ability of the empirical equation.Results show that the predicted uniaxial compressive strength values agree well with the experimental values.Statistical evaluation of performance of the proposed expression has also been carried out using a uniaxial compressive strength database,which includes 274 uniaxial compressive tests conducted worldwide on anisotropic rocks.Further,predictive capabilities of the proposed method have been compared with those of three commonly employed methods.Statistical analysis result shows that it is possible to predict uniaxial compressive strength of anisotropic rocks even if three data of uniaxial compressive strength tests at orientation angle β=0°,30° and 90° are available.