An Improved SPH Method Based on Strength Reduction to Simulate Entire Process of Joint Slope Failure
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					    摘要:
裂隙岩质边坡失稳是重大地质灾害,其破坏涉及裂纹萌生、扩展与滑移耦合过程.传统数值方法难以兼顾连续破裂与非连续接触的模拟,且存在网格畸变、参数标定复杂等局限.开发了一种基于强度折减以及核函数改进的三维SPH算法,用于模拟三维裂隙岩体边坡破裂和裂纹扩展以及接触滑移全过程.在改进三维SPH方法中,通过强度折减以及带拉伸截断的摩尔库伦破坏准则实现了裂纹萌芽的判断,通过在改进的核函数内引入损伤标志,实现岩体的裂纹扩展,随后引入了损伤粒子点点三维接触准则,构建完整粒子和断裂粒子三维间接触力.首先采用三维单轴压缩试验来验证算法的可行性,并测定了不同倾角的单裂隙岩体的脆性断裂特征.随后将改进的SPH法以及强度折减理论运用于考虑不同节理倾角的多节理岩质边坡,模拟三维裂隙岩质滑坡破坏过程并评估其稳定性.研究结果表明基于强度折减改进的SPH方法在模拟三维裂隙岩坡破坏以及稳定性问题上具有计算效率高、参数标定少以及准确率高的优点,且该方法可被用于评估其他带结构面的岩质边坡的稳定性.
Abstract:The instability of fractured rock slopes is a major geological disaster, and its failure involves the coupling process of crack initiation, propagation and slip. Traditional numerical methods are unable to simultaneously simulate continuous fracture and discontinuous contact, and they have limitations such as grid distortion and complex parameter calibration. A three-dimensional SPH algorithm based on strength reduction and kernel function improvement is developed to simulate the entire process of fracture, crack propagation and contact slip of three-dimensional fractured rock mass slopes. In the improved three-dimensional SPH method, the determination of crack germination was achieved through strength reduction and the Mohr-Coulomb violation criterion with tensile truncation. The crack propagation of rock mass was realized by introducing damage marks in the improved kernel function. Subsequently, the three-dimensional contact criterion of damage particle dots was introduced to construct the three-dimensional contact force between intact particles and fractured particles. Firstly, three-dimensional uniaxial compression tests were adopted to verify the feasibility of the algorithm, and the brittle fracture characteristics of single-fracture rock masses with different inclinations were determined. Subsequently, the improved SPH method and the strength reduction theory were applied to multi-joint rock slopes considering different joint inclination angles to simulate the failure process of three-dimensional fractured rock landslides and evaluate their stability. The research results show that the improved SPH method based on strength reduction has the advantages of high computational efficiency, less parameter calibration and high accuracy in simulating the failure and stability of three-dimensional fractured rock slopes. Moreover, this method can be used to evaluate the stability of other rock slopes with structural planes.
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									Key words:
									
 - smooth particle hydrodynamics /
 - strength reduction /
 - rock slope /
 - crack propagation /
 - contact /
 - engineering geology
 
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图 7 多裂隙岩质边坡剖面的阶梯路径破坏及其对应的速度
a.SPH模拟的阶梯路径破坏情况;b.通过SPH模拟得到的对应速度分布(单位:m/s);c.中国小湾水电站水库边坡的阶梯路径破坏模式的现场观测实例(Huang et al.,2015);d.加拿大艾希希克河滑坡陡坎边坡的阶梯路径破坏模式的现场观测实例(Brideau et al.,2009);e.FDEM模拟的阶梯路径破坏情况(Brideau et al.,2009);f.DEM模拟的阶梯路径破坏情况(Huang et al.,2015);g.扩展有限元模拟的阶梯路径破坏情况(Zhou and Chen,2019)
Fig. 7. Step path failure and the corresponding velocity of the multi-fracture rock slope profile
图 8 多裂隙岩质边坡的裂纹扩展及完全破坏过程(a);采用SPH方法对应的速度(b) (单位:m/s);(c)多裂隙岩质边坡破坏后沉积物现场观测实例(Brideau et al., 2009)
Fig. 8. The crack propagation and complete failure process of multi-fracture rock slopes (a); the velocity corresponding to the SPH method (unit: m/s) (b); field observation examples of sediments after the failure of multi-fractured rock slopes (Brideau et al., 2009) (c)
表 1 SPH岩体参数
Table 1. Rock mass parameters
物理量 岩石基质 密度(kg/m3) 2 372 弹性模量(GPa) 6.2 泊松比 0.3 粘聚力(MPa) 42 内摩擦角(°) 45 抗拉强度(MPa) 23 表 2 SPH岩质边坡模型的物理力学参数
Table 2. Physical and mechanical parameters of rock slope models
物理量 岩石基质 节理 密度(kg/m3) 2 700 2 300 弹性模量(GPa) 4 0.4 泊松比 0.14 0.35 粘聚力(MPa) 20 0.4 抗拉强度(MPa) 15 0.2 内摩擦角(°) 25 15 正常刚度(N/m) 1×108 1×107 摩擦系数 0.25 0.25  - 
						
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