He Zhuoling, Zhang Junyun, Luo Xiaolong, Huang Rui, Yang Tao, Wu Xiaofei
School of Civil Engineering, Southwest Jiaotong University, Chengdu City, 610031, Sichuan, China.
Sichuan Highway Planning Survey and Design Institute Ltd, Chengdu, 610041, Sichuan, China.
Sci Rep. 2024 Oct 27;14(1):25647. doi: 10.1038/s41598-024-77366-x.
Spatial distribution orientations of blocks can cause significant errors in the discrete element model (DEM) calculation of soil-rock mixture (SRM). To avoid this error, spherical harmonic (SH) series whose harmonization degrees fixed at 15 were proposed for block reconstruction. This research refers to the case-history of a deep excavation rift valley spanning from the Mabian to Zhaojue section of the Leshan-Xichang Expressway, mainly containing moderately-weathered silty mudstone, in the Leshan City, Sichuan Province, China. The appropriate degree of finite-term SH series is selected by the volume, surface area. 100 blocks were scanned on site, and sphericity and angularity of the blocks were calculated. The sphericity and angularity of 50 reconstructed blocks were considered for the error analysis of SH method. Moreover, stochastic polyhedron method was considered for comparing different block reconstructions. The maximum block placement angle was defined to control the spatial distribution orientations of the blocks. Large scale direct tests were carried. Numerical simulations of large-scale direct shear tests were conducted to study the influence of the spatial distribution orientations of the blocks on the mechanical properties of the SRMs. The results revealed that the finite-term SH series fixed at 15 accurately reflected the shape characteristics and mechanical behaviors of actual blocks. The spatial distribution orientations of the blocks had a minimal impact on the friction angle and cohesion of SRM constructed through the SH method. The SRMs developed via the SH method exhibited marginal variations in contact force and anisotropy index of contact across diverse block placement strategies. The evolution of coordination number was closer when employing the SH method under varied block placement methods. Blocks reconstructed by the SH method, could mitigate errors in DEM calculation caused by the spatial distribution orientations of the blocks.
块体的空间分布方向会在土石混合体（SRM）的离散元模型（DEM）计算中导致显著误差。为避免此误差，提出了调和度固定为15的球谐（SH）级数用于块体重构。本研究参考了四川省乐山市乐山 - 西昌高速公路马边至昭觉段一个深挖裂谷的工程实例，该区域主要包含中等风化的粉质泥岩。通过体积、表面积选择合适的有限项SH级数。现场扫描了100个块体，并计算了块体的球形度和棱角度。考虑了50个重构块体的球形度和棱角度用于SH方法的误差分析。此外，还考虑了随机多面体方法来比较不同的块体重构。定义了最大块体放置角度以控制块体的空间分布方向。进行了大规模直接试验。开展了大规模直剪试验的数值模拟，以研究块体空间分布方向对土石混合体力学性能的影响。结果表明，调和度固定为15的有限项SH级数准确反映了实际块体的形状特征和力学行为。块体的空间分布方向对通过SH方法构建的土石混合体的摩擦角和黏聚力影响最小。通过SH方法生成的土石混合体在不同块体放置策略下的接触力和接触各向异性指数呈现出微小变化。在不同块体放置方法下采用SH方法时，配位数的演化更接近。通过SH方法重构的块体可以减轻块体空间分布方向在DEM计算中引起的误差。
