震后松散砾石土泥石流起动中的孔隙压力

Pore pressure is ultimately generated in the loose gravel soil by pore water and pore gas appreciably subjected to compression, compelling and drain off as it were under shear, e.g. in the case of debris flows motivation triggered by rain infiltration, which has been verified in a series of recent experiments carried out by applicant. Currently there are many studies concerning pore water pressure fluctuation in the initiation processes of debris flows, but fewer studies on soil pore gas's component contributions to pore pressure both domestic and foreign literatures. In this project, through taking the loose gravel soil post-wenchuan earthquake as the research object, carrying out observation and experimental research, adopting some research methods, such as, field trip to designated research sites, indoor model experiments, situ experiments, numerical simulation and theoretical analysis and so on, and observing timely the macro-failure phenomenon and parameter variation characteristics into the soil(pore pressure, soil moisture, dry density), firstly, the component ratio and conversion characteristics between pore water pressure and pore air pressure in the pore pressure are analyzed respectively. Secondly, the comprehensive effects of pore air pressure and pore water pressure(collectively referred to as the pore pressure) in the motivation process of gravel soil debris flow and fluctuation mechanism of pore pressure are researched. Thirdly, semi empirical expressions of pore pressure fluctuation equation using statistical regression method and the theory of classical unsaturated soil mechanics is proposed. Then debris flow critical discriminant rules on pore pressure fluctuation finally is established. Therefore, research achievements may not only can provide strong theoretical basis for perfecting the initiation mechanism of debris flow, but also play a reference guiding role for the prevention and early warning in the debris flow prone area after earthquake.

震后松散砾石土在降雨激发泥石流的过程中，孔隙液体与气体的流动、压缩与排逸最终形成孔隙压力，这在申请者最近的系列实验研究中得到验证。国内外学者的研究证实了泥石流起动中的孔隙水压力波动现象，却实质性忽略了其中土体孔隙气体对孔隙压力构成的贡献。本申请将以汶川地震震后松散砾石土为研究对象，开展观测与实验研究，采取野外考察与调查、模型试验与原位实验、数值模拟与理论分析等研究方法，通过实时观测泥石流的宏观溃动现象及土体内部参数变化特征（孔压、含水量、干密度），研究孔隙压力中孔隙水压力与孔隙气压力的构成比例及其相互转化，探索两者综合作用（总称为孔隙压力）对泥石流激发过程的影响及孔隙压力波动变化的机制，利用统计回归方法及经典非饱和土力学理论推导孔隙压力波动变化方程的半经验表达式，最终提出基于孔隙压力波动变化特性的泥石流起动临界判别式。研究成果可为震后砾石土堆积区泥石流的防灾预警提供参考。

震后松散砾石土在降雨激发泥石流的过程中，孔隙液体与气体的流动、压缩与排逸最终形成孔隙压力。国内外学者的研究证实了泥石流起动中的孔隙水压力波动现象，却实质性忽略了其中土体孔隙气体对孔隙压力构成的贡献。. 本项目通过文献评阅(400多篇国内外文献)、野外考察与调查（3次都汶公路沿线泥石流灾害考查)、气象观测(野外实测震后松散土泥石流起动降雨数据)、三维测量(野外测定泥石流特征参数)、水槽模型试验(9组)、原位试验、室内测试(测定土体物理力学性质)、数值模拟与理论分析等研究方法，以汶川地震震后松散砾石土为研究对象，系统地研究了震后松散砾石土体泥石流起动中孔隙压力波动变化特征与规律，揭示了孔隙气体对其泥石流灾害的起动影响作用，并以此探索了基于注浆理论的震后松散砾石土的防治新理论与技术。. 本项目查明了震后松散砾石土泥石流起动因素的变化特征与规律，研究了孔隙压力波动变化过程、空间分布规律及其与土体含水量的变化关系，分析了孔隙压力幅度、频率及传播速度等参数变化特征，探索了孔隙压力中孔隙水压力与孔隙气压力的组构关系、构成比例及相互转化规律，推导了孔隙压力波动变化方程的半经验表达式，提出了基于孔隙压力波动变化特性的泥石流起动临界判别式，探讨了孔隙压力波动变化机制与基于注浆理论的震后松散砾石土防治新理论与技术。. 项目取得的基于孔隙压力波动变化特性的泥石流起动临界判别式与基于注浆理论的震后松散砾石土防治新理论与技术等创新成果，具有较好的成果转化及应用价值，建议有关部门加强推广它们的科研成果转化及应用。. 项目取得的研究成果可为遭受强震的中国西南地区震后松散砾石土的水土流失防治与预警预报提供理论依据与技术支撑。