强震过程巨型滑坡超孔隙水压力累积与激发作用研究

It has been reported that the sudden initiation of gigantic landslide is contributed by pore-water pressure induced strength degradation in sliding zone, such as the Daguangbao landslide (120000×104 m3) triggered by Wenchuan earthquake, Tsaoling landslide (13000×104m3) triggered by Chi-Chi earthquake and Higashi-Takezawa landslide (2000×104m3) triggered by Niigata earthquake. However, the study of water pressure accumulation and excitation dependent initiation mechanism is limited. This research chose the Daguangbao landslide as a case study, of which the sliding zone is a pre-existing and saturated crushed zone. The pore-water pressure response and excess pore-water pressure excitation pattern are studied by conducting physical and numerical simulation tests. The influences of internal structure in crushed zone, seismic parameters on transient response, and accumulation of excess pore-water pressure are studied. The importance of the factors is quantized. Based on the transient dynamics theory and incompatible deformation theory, the water pressure dynamic change and the peak value of excess pore-water pressure are triggered by dilatation and compression of the crushed zone. The amplification effect of strong seismic wave’s non-stationary and pulse character on excess pore-water pressure are analyzed. The incompatible deformation and physical properties response dependent theory of excess pore-water pressure excitation in crushed zone is established. The mechanisms of effective strength reduction and sudden initiation of gigantic landslide are further discussed.

已有成果表明，强震触发巨型滑坡(如汶川地震大光包滑坡(120000×104m3)、Chi-Chi地震Tsaoling滑坡(13000×104m3)、Niigata地震Higashi-Takezawa滑坡(2000×104m3)等)骤然启动与饱水滑带超孔隙水压力引起的力学参数骤降密切相关，但目前此方面有关水压力累积过程和激发机理研究基础和成果不足。拟申请课题以滑带背景为岩层层间饱水破碎带的大光包滑坡为原型，通过开展大型物理模拟试验，结合数值模拟，分析破碎带孔隙水压力瞬态特征与超水压发展模式。阐明在不同内部结构和地震动参数条件下超水压累积特征及影响规律；基于瞬态动力学理论和非协调变形理论，分析岩体扩容-压缩快速交替过程超水压特征及极值变化规律，探明天然强震波非平稳脉冲特性对超水压极值的放大规律，揭示依赖动力非协调变形和物态响应的超水压激发机理，进一步探讨有效应力降低及巨型滑坡启动机制。

近十几年来，青藏高原及其周缘相继发生了2008年汶川Ms8.0级、2010年玉树Ms7.1级、2013年芦山Ms7.0级、2014年鲁甸Ms6.5级、2015年尼泊尔Ms8.1级、2017年九寨沟Ms7.0级等多次强震。强震作用下巨型滑坡启动与滑带饱和水超水压引起的力学参数骤降密切相关。大光包滑坡是汶川地震触发的最大规模滑坡，其滑带地质背景为埋深400m的饱水层间构造破碎带。本项目以大光包滑坡为实例，基于大型平硐揭露其滑带背景为先期层间饱水破碎带事实，通过现场工程-水文地质调查与测试、室内大型物理模拟试验和理论分析等方法，分析强震过程层间饱水破碎带超水压瞬态过程、累积模式及变化特征，揭示依赖模型非协调变形的“振动冲压–拉张”和“振动剪切”是瞬态超间隙水压力成因、依赖软弱层非协调变形的动力损伤是超间隙水压力累积成因，建立了考虑超孔压激发的层间饱水破碎带摩擦系数弱化模型，首次尝试通过Newmark位移模拟由超孔隙水压力（基于实验数据）引起的滑动弱化对大型滑坡启动和运动的影响，揭示了破碎带有效应力降低规律，提出了强震触发大光包滑坡“超水压减阻触滑”启动机制。

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