云南红土型库岸稳定性研究

发布时间：2018-09-12 06:00

【摘要】：云南作为红土高原,区域性红土广泛分布,作为一种资源优势,已经广泛运用在各种基础工程设施中。但是由于自然和人为因素的影响,再加上水位升降及水库蓄水引起的干湿循环过程和浸泡,常常导致库岸失稳,严重影响了工程安全运行和持续运行,且缩短了工程寿命。针对这一客观实际,本文以云南红土型水库库岸为研究对象,采用理论研究与试验研究相结合的方法,对云南红土型库岸进行稳定性研究。通过开展土工试验、干湿循环试验、微结构试验,设置不同初始干密度、不同初始含水率、不同加砂比例等条件,研究库水位升降及浸泡作用下库岸红土宏微观特性。通过开展室内模型库岸试验,研究库岸红土迁移特性以及典型特征点的孔隙水压力、土压力的变化规律。采用有限元法、极限平衡方法,结合概率论、土力学等学科研究红土型库岸失稳的临界条件,在综合试验研究和理论研究的基础上,揭示了库水位升降及浸泡作用下红土型库岸失稳机理,这对有效预测和防治红土型库岸失稳具有实际意义。库岸红土宏微观特性对库岸稳定性的影响在于:在整个干湿循环过程中,不同初始干密度、不同初始含水率、不同加砂比例红土的内摩擦角、粘聚力及抗剪强度均随着循环次数的增加而呈下降趋势,并在循环10次左右趋于稳定。针对不同初始干密度红土,在整个干湿循环过程中,内摩擦角降幅与初始干密度大小成正相关关系,粘聚力、抗剪强度降幅均与初始干密度大小成反相关关系;针对不同初始含水率红土,在整个干湿循环过程中,内摩擦角、粘聚力及抗剪强度降幅最小的是初始含水率为26.5%的红土,降幅最大的是初始含水率为30.5%的红土;针对不同加砂比例红土,在整个干湿循环过程中,内摩擦角、粘聚力及抗剪强度降幅最小的是加砂10%的红土,降幅最大的是加砂15%的红土。库岸地形地貌对库岸稳定性的影响在于:随着库岸坡角的增加,库岸安全系数越来越小,其中在坡角为45°～50°区间时,安全系数降幅最大,在实际工程中应尽量避免处于此危险区间的坡角。库水升降幅度及速率对库岸稳定性的影响在于:库水上升阶段,坡高的60%为相对危险水位,此时库水速率对库岸稳定性影响程度相对较小。库水下降阶段,坡高的70%为相对危险水位,此时库水速率越大,库岸安全系数降幅也就越大,库岸越不稳定。红土型库岸失稳的临界条件理论研究表明:在水库运行的第12年,红土型库岸处于失稳的临界状态,应该根据实际的工程情况及时对水库库岸进行加固处理。库水位升降及浸泡作用下红土型库岸失稳机理,实质上是库水对红土物理、化学、力学等多方面共同作用结果。其中物理作用包括:颗粒的软化、泥化作用,库水对坡内红土颗粒的迁移作用。化学作用包括:矿物质电离水解、水化作用。力学作用包括:地下水、孔隙静水压力及孔隙动水压力、库水浮托力对库岸红土颗粒作用。
[Abstract]:Yunnan, as a red earth plateau, is widely distributed in the region. As a resource advantage, Yunnan has been widely used in various infrastructure projects. However, due to the influence of natural and human factors, coupled with the rise and fall of water level and the process and immersion of the dry-wet cycle caused by reservoir impoundment, it often leads to the instability of the reservoir bank, which seriously affects the safe operation of the project. In view of this objective reality, this paper takes the Bank of Yunnan laterite reservoir as the research object, and studies the stability of Yunnan laterite reservoir bank by combining theoretical research with experimental research. The macroscopic and microscopic characteristics of laterite in reservoir bank under the action of water level fluctuation and immersion are studied under the conditions of dry density, initial water content and sand ratio. Combining probability theory and soil mechanics, the critical condition of laterite reservoir bank instability is studied. On the basis of comprehensive experimental study and theoretical study, the mechanism of laterite reservoir bank instability under the action of water level fluctuation and immersion is revealed, which is of practical significance for effective prediction and prevention of laterite reservoir bank instability. The influence of stability is that the internal friction angle, cohesion and shear strength of laterites with different initial dry densities, initial water content and sand ratio decrease with the increase of cycling times, and tend to be stable about 10 cycles. During the whole dry-wet cycle, the decrease of internal friction angle is positively related to the initial dry density, and the decrease of cohesion and shear strength is inversely related to the initial dry density. For different proportion of sanded laterite, the lowest reduction of internal friction angle, cohesion and shear strength is 10% sanded laterite, and the greatest reduction is 15% sanded laterite. With the increase of the angle, the safety factor of the reservoir bank becomes smaller and smaller. When the slope angle is between 45 degrees and 50 degrees, the safety factor decreases the most. In practical engineering, the slope angle in this dangerous zone should be avoided as far as possible. The stability of the reservoir bank is less affected by the rate. At the stage of the reservoir downhill, 70% of the slope height is the relative dangerous water level. The larger the rate of the reservoir water, the greater the decrease of the safety factor of the reservoir bank and the more unstable the reservoir bank will be. The failure mechanism of laterite reservoir bank under the action of water level fluctuation and immersion is essentially the result of physical, chemical and mechanical interaction between reservoir water and laterite. Migration of particles. Chemical processes include mineral ionization and hydrolysis, hydration. Mechanics include groundwater, pore hydrostatic pressure and pore hydrodynamic pressure, and reservoir water buoyancy on laterite particles.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV223

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