During the high-speed and long-runout sliding failure process of large landslides, severe friction and heat generation in the sliding zone induce an interface friction effect between the debris flow and the bedrock, influencing the final accumulation morphology of the landslide. In this paper, a two-dimensional landslide model of the Yangbaodi landslide in Shenzhen was established using the material point method. A contact algorithm was introduced through a multi-background grid method to conduct numerical simulations on the initiation, sliding, and accumulation processes of the landslide. The results show that after initiation, the landslide moves over a long distance in a flow-like state along the bedrock. Influenced by the topographic and geomorphic characteristics of the bedrock, local accumulation is formed in some gently inclined areas. The final accumulation morphology is relatively close to the calculation results of methods such as the particle finite element method, which preliminarily verifies the effectiveness of the method in this paper. Calculations changing the friction coefficient between the debris flow and the bedrock reveal that the interface friction effect significantly influences the movement behavior of the debris flow. The maximum sliding velocity and farthest sliding distance decrease as the friction coefficient increases. However, the soil deformation of the debris flow near the bedrock area is more obviously affected by friction, and the equivalent plastic strain conversely increases as the friction coefficient increases. At the same time, a large number of discontinuous plastic deformation protrusions are formed, influencing the final accumulation morphology of the debris flow. The research results can provide an effective technical means for analyzing the failure mechanism of natural landslides under the interface friction effect.
许强等[8]总结分析了大型崩滑灾害动力特征,认为滑坡通常以碎屑流、碎裂‒滑移崩塌、碎裂‒俯冲滑移等多种形式发生高速运动。滑坡属于典型的大变形破坏问题,采用传统有限单元法(Finite Element Method, FEM)模拟该过程存在网格畸变或计算不收敛等局限,因此有学者建议采用新型数值计算方法分析滑坡致灾机理。例如,张卫杰等[9]采用滑粒子流体动力学(Smoothed Particle Hydrodynamics,SPH),模拟了四川省盐源县玻璃村“7·19”滑坡,分析了不同强度折减系数对滑坡滑动距离和滑动速率的影响;沈佳轶等[10]采用耦合欧拉‒拉格朗日(Coupled Eulerian-Lagrangian,CEL)框架下的欧拉方法揭示了加拿大Saint-Jude滑坡的渐进性破坏机制,计算结果表明,坡脚侵蚀导致的局部剪切带的形成和拓展是灵敏性黏土斜坡发生渐进性破坏的主要诱因;Li等[11]和Zhang等[12]分别采用离散单元法(Discrete Element Method,DEM)和粒子有限单元法(Particle Finite Element Method,PFEM)针对深圳杨宝地滑坡的破坏模式展开细致研究,分析了不同材料参数对其运动规律的影响。近些年发展起来的物质点法(Material Point Method,MPM)同时具有拉格朗日和欧拉方法的优势,在模拟固体材料的大变形破坏和界面演化等问题时具有良好的计算效率和精度[13-15]。该方法同样被广泛用于探究滑坡的致灾机制。Li等[16]和Fernández等[17]采用物质点法模拟了汶川地震诱发的大光包巨型滑坡的破坏过程,分别从二维和三维的角度揭示了地质条件和地貌特点等因素对滑坡运动规律的影响。但是,上述研究并未充分考虑碎屑流与下部基岩之间的界面摩擦作用。碎屑流在高速运动过程中与基岩表面发生剧烈摩擦会产生大量热量,由此产生的气垫层将降低摩擦系数。此外,碎屑流会改变基岩表面轮廓特征,造成接触面出现摩擦弱化现象。Zhang等[18]的研究成果表明,受碎屑流与基岩之间的摩擦生热影响,大光包巨型滑坡的界面摩擦系数显著下降,致灾范围显著扩大;朱晨光等[19]采用自主开发的MatDEM离散元软件分析了滑坡滑带摩擦生热过程,结果显示滑带附近会形成高热量区,引发的气垫作用将降低土体抗剪强度。因此,在采用物质点法分析滑坡破坏机理时,需要考虑界面摩擦效应,以得到更为准确的计算结果。
为提升计算精度,采用Bardenhagen等[21-22]提出的广义插值物质点法(Generalized Interpolation Material Point Method,GIMP),将计算域离散为由特征函数表示的质点,根据Petro-Calerkin方法建立新的求解格式。特征函数定义了质点占据的空间区域,在初始构型中满足单位分解条件,因此,可以将质点的体积表示为:
China Natural Resources News. China successfully predicted 534 geological disasters last year [EB/OL], 2021-01-18.
[3]
HEX, LIANGD, BOLTONM D. Run-out of cut-slope landslides: mesh-free simulations[J]. Géotechnique, 2018, 68(1): 50-63.
[4]
LINC, PASTORM, YAGUEA, et al. A depth-integrated SPH model for debris floods: Application to Lo Wai(Hong Kong)debris flood of August 2005[J]. Géotechnique, 2019, 69(12): 1035-1055.
RUIGuorong, XUJiancong, SUNJun. Stability and risk analysis of soft rock highway tunnel passing through ancient landslide[J]. Highway, 2024, 69(3): 399-404.
[9]
ZHANGW J, ZHENGH, JIANGF Y, et al. Stability analysis of soil slope based on a water-soil-coupled and parallelized smoothed particle hydrodynamics model[J]. Computers and Geotechnics, 2019, 108: 212-225.
XUQiang, HUANGRunqiu. Kinetics charateristics of large landlides triggered by may 12th Wenchuan earthquake[J]. Journal of Engineering Geology, 2008, 16(6): 721-729.
ZHANGWeijie, YURuihua, CHENYu, et al. Post-failure movement characteristics and parameter back-analysis for landslides considering effect of strength parameters[J]. Chinese Journal of Geotechnical Engineering, 2022, 44(12): 2304-2311, F0004.
SHENJiayi, CHENQian, KUMeng, et al. Numerical simulation of progressive failure of sensitive clay slopes using CEL method[J]. Chinese Journal of Geotechnical Engineering, 2022, 44(12): 2297-2303.
[18]
LIW C, LIH J, DAIF C, et al. Discrete element modeling of a rainfall-induced flowslide[J]. Engineering Geology, 2012, 149: 22-34.
[19]
ZHANGX, KRABBENHOFTK, SHENGD C, et al. Numerical simulation of a flow-like landslide using the particle finite element method[J]. Computational Mechanics, 2015, 55(1): 167-177.
[20]
SULSKYD, ZHOUS J, SCHREYERH L. Application of a particle-in-cell method to solid mechanics[J]. Computer Physics Communications, 1995, 87(1/2): 236-252.
[21]
SULSKYD, KAULA. Implicit dynamics in the material-point method[J]. Computer Methods in Applied Mechanics and Engineering, 2004, 193(12/13/14): 1137-1170.
[22]
SULSKYD, GONGM. Improving the material-point method[M/OL]//WEINBERG K, WALLIN M. Innovative numerical approaches for multi-field and multi-scale problems. Cham: Springer International Publishing, 2016: 217-240.
[23]
LIX P, TANGX, ZHAOS X, et al. MPM evaluation of the dynamic runout process of the giant Daguangbao landslide[J]. Landslides, 2021, 18(4): 1509-1518.
[24]
FERNÁNDEZF, VARGASE, MULLERA L, et al. Material point method modeling in 3D of the failure and run-out processes of the Daguangbao landslide[J]. Acta Geotechnica, 2024, 19(7): 4277-4296.
[25]
ZHANGY F, ZHANGW G, WANGL Q, et al. Mechanism of the high-speed and long-run-out landslide considering the evolution of the frictional heat in the sliding zone[J]. Natural Hazards, 2024, 120(4): 3299-3317.
ZHUChenguang, LIUChun, XUQiang, et al. Discrete element numerical simulation research on friction heat in sliding zone of the landslide[J]. Journal of Engineering Geology, 2019, 27(3): 651-658.
ZHOUCuiying, LIUZhen, XUEYiguo, et al. Some thoughts on basic research of red beds disaster[J]. Journal of Engineering Geology, 2023, 31(3): 689-705.
[30]
BARDENHAGENS G, KOBERE M. The generalized interpolation material point method [J]. Computer Modeling in Engineering and Sciences, 2004, 5(6): 477-496.
[31]
BARDENHAGENS G, BRACKBILLJ U, SULSKYD. The material-point method for granular materials[J]. Computer Methods in Applied Mechanics and Engineering, 2000, 187(3/4): 529-541.
[32]
MAJ, WANGD, RANDOLPHM F. A new contact algorithm in the material point method for geotechnical simulations[J]. International Journal for Numerical and Analytical Methods in Geomechanics, 2014, 38(11): 1197-1210.
ZHAOChunhong, DAIFuchu. Study on failure mechanism of a fill slope in Shenzhen[J]. The Chinese Journal of Geological Hazard and Control, 2007, 18(2): 1-8.