管单元用于缩减岩体渗透张量计算规模

Calculation scale reduction on determining permeability tensor for fracture networks using tube element

摘要:

为探讨裂隙空间渗流的优势路径、在满足精度的前提下减少计算量并使模型更具实用价值,根据实测结构面资料,采用圆盘模型,生成与现场岩体具有相同统计特征的三维裂隙网络,将渗流渠道简化为一维管单元模型,研究分组排列和全排列两种方式缩减计算规模对渗透张量和表征单元体（representative elementary volume,REV）大小的影响。并用某工程数据校核缩减规模效应。结果显示:采用全排列方式缩减误差相对较小；当计算规模缩减达到70%时,基本不改变渗透张量的精度；裂隙岩体的渗透张量REV尺寸会随缩减规模的增加有所增大。可见确实存在由直径较大裂隙控制渗流特性的主干裂隙网络骨架,计算时缩减裂隙网络规模到一定程度,仍然可以保证渗透张量具有足够的精度。

Abstract:

To explore the preferential flow pathways of seepage in the fracture space, reduce the amount of calculation and make the model more practical under the premise of meeting the accuracy, according to the measured structural surface data, a three-dimensional (3D) fracture network with the same statistical characteristics as the field rock mass was generated by using the disc model, and the seepage channel was simplified to one-dimensional tube element model. The influences of reducing the calculation scale by group arrangement and full arrangement on the permeability tensor and the size of representative elementary volume (REV) were investigated respectively. The scale reduction effect was verified using practical engineering data. Results show that the reduction error of full arrangement was relatively small. When the calculation scale was reduced to 70%, the accuracy of the permeability tensor was basically unchanged. The REV size of the permeability tensor of the fractured rock mass increased with the increase of the reduction scale. There was indeed a backbone fracture network skeleton with larger diameter fractures controlling the seepage characteristics, and sufficient accuracy of the permeability tensor could still be ensured when the calculation scale of the fracture network was reduced to a certain extent.