两相物质组成对泥石流沉积物固结机理及承载特性的影响机制研究

Dealing with the debris flow sediments has been found a difficult and time-consuming problem when highways are blocked after debris flows. Thus usually an emergency passage is necessary during the sediment dredging. However, as key issues which determine the safety of the emergency passage, the consolidation mechanism of debris flow sediments, as well as their responses to loads is still not clear. So far, there is still not any well-accepted calculation method for the bearing capacity of debris flow sediments, and this has been a key problem for improving highway reconstruction. As a typical two-phase flow, the composition of the debris flow will significantly affect its bearing capacity. In this study, in order to investigate the consolidation mechanism and bearing capacity of debris flow sediments, we will chose slurry viscosity, solid phase ratio and grain diameter as the characteristic factors for the two-phase debris flow, and we will focus on the following concerns: (1) the two-phase model of debris flow sediments and interaction between liquid and solid during consolidation and sedimentation;(2) the consolidation mechanical model with different characteristic factors; (3) the relationship between the composition and the bearing capacity of debris flow; and (4), the determination for bearing capacity of debris flow sediments. This study will be helpful to not only better understanding of the impact of material composition on mechanical characteristics of debris flow sediments, but also the improvement of the technics for dealing with debris flow disasters to highway.

大型及特大型泥石流淤埋路段清淤困难大，断道时间长，需在泥石流沉积物上开辟应急通道通行救灾，泥石流沉积物的固结过程与承载特性是保证应急通行的关键，目前对泥石流沉积物固结、承载特性的研究尚处于开始阶段，尚未建立有效的泥石流沉积物承载力计算方法，严重阻碍了灾害抢通能力的提升。泥石流是典型的两相流体，其固液两相物质的组成对沉积物承载力的影响较大，本项目即基于两相流理论，遴选浆体粘度、固相比与颗粒粒径为泥石流沉积物的两相特征指标，建立泥石流沉积物两相结构模型，结合实验研究，分析两相指标在固结过程中的相互影响，建立不同物质组成条件下的泥石流沉积物固结力学模型，揭示不同物质组成条件下的泥石流沉积物承载力变化规律，最终建立泥石流沉积物承载力计算公式。本项目研究对于深入认识泥石流物理组分对其力学性质影响机制，促进泥石流力学研究的发展以及提高公路抗险救灾能力具有重要的科学价值。

大型及特大型泥石流沉积物淤积厚度大，清淤难度大，应急通行及灾后重建需以泥石流沉积物为直接承载对象，然而泥石流沉积物具有高流变、慢固结、低承载性，探讨泥石流沉积物的固结与承载特性是泥石流灾害评估与防治的关键。本项目基于泥石流沉积物的两相性，进行物质组成对泥石流沉积物固结与承载特性的影响研究。.（1）基于两相结构模型，以浆体黏度、体积浓度与颗粒粒径为泥石流沉积物的两相特征指标，考虑液相浆体的粘滞力和浮力、固相颗粒的静止摩擦力和接触挤压摩擦力，分析泥石流沉积物两相物质间的相互作用，建立一维准静止流态下的泥石流沉积物的本构关系。.（2）基于泥石流沉积物的结构特性，将泥石流沉积物的固结过程简化为自重应力下的正常固结过程。固结中，液相浆体发生由饱和至非饱和的相变，并由沉积物表面向内部形成固结壳对内部施加的固结附加应力，浆体黏度增大，固相颗粒的体积浓度增大，颗粒正粒序沉积。据此建立固结方程，进行泥石流沉积物固结特性室内模型试验，揭示固结附加应力、固结壳锋面发展及孔隙水压力消散规律。.（3）泥石流沉积物因其表层的固结壳及底部细颗粒“铺床”，孔隙水压力消散与承载力增长过程十分缓慢。根据将泥石流沉积物不同固结阶段固结壳的厚度建立其承载力计算方法。进行泥石流沉积物承载特性室内模型试验，探讨两相特征指标对泥石流沉积物承载力的影响，试验结果表明，体积浓度与承载力的增长呈正相关。.（4）在沉积物中加入巴氏芽孢杆菌作为加速固结剂，进行泥石流沉积物微生物矿化室内模型试验，记录芽孢杆菌的添加对泥石流沉积物固结过程中的固结与承载特性的变化规律。结果表明微生物矿化生成的碳酸钙作用于固结壳，减小沉积物的沉降，因菌液和培养液的添加不利于孔隙水压力的消散，但沉积物固结壳的承载力相对提高了1.24倍。.本项目研究对于深入认识泥石流物理组分对其力学性质影响机制，促进泥石流力学研究的发展以及提高公路抗险救灾能力具有重要的科学价值。