RBF composite parameter model for structural surface roughness with factor analysis
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摘要: 结构面粗糙度的表征是预测峰值剪切强度的基础性工作,单一参数无法全面反映结构面的形貌特征,而由各表征参数并列构成的指标系统是一个存在信息重叠的非线性系统,为此引入因子分析通过正向标准化实现参数降维可有效剥离交叉信息,同时将正向标准化的指标系统通过RBF神经网络结构实现非线性参数的线性映射,实际运行过程中选取6个反映结构面粗糙度的统计参数并建立JRC反算关系,构建76组训练样本和37组测试样本,建立了一个反映结构面形貌起伏高、起伏角、接触度的多指标复合参数模型,同时固定隐含层神经元的数目从而提高运算速度,通过实测数据计算相对误差和决定系数进行性能评价。利用样本数据和岩石结构面直剪实验验证了模型的预测精度。最后讨论了因子分析的适用性和可能的误差分析。Abstract: The characterization of the structural surface roughness is the groundwork for predicting the peak shear strength. The single parameter cannot fully reflect the characteristics of structural surface morphology. The index system composed of some single characterization parameters is a nonlinear system with much overlapping information. The factor analysis is conducted to reduce the dimension and strip the overlapping information by canonical normalization. At the same time, the standardized index system is transformed from nonlinear into linear by the RBF neural network structure. In practice, 6 statistical parameters reflecting the structural surface roughness are selected, the inverse calculation of JRC is established, 76 training samples and 37 group test samples are built. The multi-index composite parameters are established considering the characteristics of embossment of joints, such as height, angle and contact degree. In the mean time, the number of neurons in the hidden layer is fixed to improve the calculation speed. The prediction accuracy of the model is verified by the sample data and the direct shear tests of rock joints. The relative error and determination coefficient are calculated through the measured data to evaluate the performance. Finally, the applicability of the factor analysis and possible error analysis are discussed.
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Keywords:
- rock /
- structural surface /
- roughness /
- RBF neural network /
- factor analysis
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表 1 RBF指标系统及JRC计算式
Table 1 RBF index system and formulas for JRC
指标 定义式 JRC计算式 CLA 1N∑i=Ni=1|yi| 2.76+78.87CLA SDi {arctan[1N−1∑i=N−1i=1(λ)2]1/2λ=yi+1−yixi+1−xi−taniave 1.042SDi−4.733 SF 1N−1∑i=Ni=1(yi+1−yi)2 37.63+16.5lgSF Rp ∑i=N−1i=1[(xi+1−xi)2+(yi+1−yi)2]1/2∑i=N−1i=1(xi+1−xi) 229.44Rp−226.94 Z2 √1N−1∑i=N−1i=1(yi+1−yixi+1−xi)2 32.69+32.98lgZ2 C∗2D 90°(2D)/(C∗+1) 3.95(C∗2D)0.7−7.98 表 2 相关系数矩阵
Table 2 Matrices of correlation coefficient
指标 *SDi *Rp *Z2 *SF *CLA *C2D *SDi 1 *Rp 0.953 1 *Z2 0.986 0.947 1 *SF 0.875 0.997 0.967 1 *CLA 0.742 0.756 0.856 0.84 1 *C2D 0.642 0.912 0.653 0.756 0.954 1 表 3 旋转后的载荷系数
Table 3 Load coefficients after rotation
指标 *Z2 *SDi *Rp *C2D *SF *CLA F1 0.873 0.802 0.786 0.694 0.432 0.537 F2 0.462 0.411 0.364 0.679 0.927 0.934 表 4 基于不同方法测算的S~A1号试样结构面JRC值
Table 4 JRC values of S-A1 joints measured by different methods
指标 最小值 最大值 平均值 实测值 相对误差/% RBF 4.01 8.69 6.34 6.53 2.9~7.86 Z2 2.13 9.02 4.78 6.53 26.7~38.1 Rp 3.87 9.34 5.20 6.53 0.3~43.02 SDi 3.45 10.78 7.94 6.53 21.6~37 -
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