Research on tetrahedral adaptive mesh grading refinement for intersecting faults
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摘要: 目前四面体自适应网格细化技术多集中于简单层状地质体的三维重构与表达分析,对结构复杂、数据不连续的含交错断层等地质体进行自适应网格细化时,易出现过度细化,导致断层区域的网格结构受到影响。为了提高含复杂断层四面体网格模型的精度,提出一种适用于交错断层的四面体自适应网格分级细化方法。首先,根据断层影响范围公式,自适应确定断层网格附近的细化范围;其次,构建四面体和四面体边的分级细分公式,确定细化范围内的四面体和四面体边的分级;然后,针对四面体网格细分时出现的多种情况,通过对边的升级处理,将细分的8种类型统一为3种类型;最后,在细化范围内,通过新增加顶点和原顶点重新连接四面体,改变网格的单元尺寸,生成高质量的网格模型。以内蒙古自治区某含交错断层露天煤矿的四面体网格模型为例,使用三维网格质量评估算法及FLAC3D模拟软件分析细化前后的网格模型,结果表明:细化后的网格模型失真值从0.331 7降低到0.306 1,表明网格的质量得到提升;在相同参数下,未细化模型的最大位移为1.16 m,稳定性系数为1.27,分级细化后模型的最大位移为1.29 m,稳定性系数为1.23;细化后模型的位移云图处于断层处,且能够体现断层分布特征和断层对边坡的影响规律,而未细化模型的位移云图的位置偏离断层中心,断层对边坡的影响效果不明显。Abstract: Current tetrahedral adaptive mesh refinement techniques have primarily focused on the 3D reconstruction and analysis of simple stratified geological bodies. When applying adaptive mesh refinement to complex geological structures, such as those containing intersecting faults with discontinuous data, excessive refinement can easily lead to compromised mesh structures in the fault zones. To improve the accuracy of tetrahedral mesh models for such complex fault systems, this study proposed a tetrahedral adaptive mesh grading refinement method specifically for intersecting faults. Initially, the refinement range around the fault was adaptively determined based on a fault influence formula. Subdivision formulas were then developed for tetrahedrons and tetrahedral edges to grade both the tetrahedrons and their edges within the refinement range. To address the various scenarios that arose during tetrahedral mesh subdivision, the eight types of subdivisions were unified into three types by upgrading the edge treatments. Finally, new vertices were introduced, and existing vertices were reconnected to tetrahedrons within the refined area, adjusting mesh element sizes to generate a high-quality mesh model. A case study was conducted on a tetrahedral mesh model from an open-pit coal mine in Inner Mongolia. The mesh model was analyzed before and after refinement using a 3D mesh quality evaluation algorithm and FLAC3D simulation software. Results showed that the distortion value of the refined mesh model decreased from
0.3317 to0.3061 , indicating an improvement in mesh quality. Under the same parameters, the unrefined model exhibited a maximum displacement of 1.16 m with a stability coefficient of 1.27, while the refined model showed a maximum displacement of 1.29 m and a stability coefficient of 1.23. The displacement cloud map of the refined model was aligned with the fault, accurately reflecting the fault distribution and its impact on the slope. In contrast, the displacement cloud map of the unrefined model was misaligned with the fault center, demonstrating a less pronounced effect of the fault on the slope. -
表 1 不同四面体类型边的升级情况
Table 1. Upgrades for edges of different tetrahedral types
类型 u 分级大于0的
边是否共面是否改变
边的分级进行升级的
边个数分级大于
0的边个数细分
模式① 1 是 否 0 1 case① ② 2 是 是 1 3 case② ③ 2 否 是 4 6 case③ ④ 3 是 否 0 3 case② ⑤ 3 否 是 3 6 case③ ⑥ 4 否 是 2 6 case③ ⑦ 5 否 是 1 6 case③ ⑧ 6 否 否 0 6 case③ 表 2 不同断层模型算法的计算时间
Table 2. Computation time of the different fault model algorithms
断层模型 顶点数 三角面数 四面体数 细分耗时/s 总耗时/s 初始网格模型 16 570 69 192 46 629 0 0 F1断层 225 620 935 428 630 385 3.5 5.1 F1和F 2断层 457 431 1 896 517 1 278 063 7.3 8.9 -
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