【作者】 孔德志；

【导师】 张丙印；

【作者基本信息】 清华大学 ， 土木工程， 2009， 博士

【摘要】 堆石料在高应力作用下会发生较严重的颗粒破碎现象,并会对其变形和强度特性产生较大的影响。目前针对颗粒破碎的试验研究工作主要采用天然堆石料进行,存在颗粒破碎不易控制和颗粒破碎率不能准确确定等问题,难以进行定量的研究工作。为了深入研究颗粒破碎机理及其对堆石体强度和变形的影响,本文采用水泥椭球人工模拟堆石料进行了系列的常规三轴试验研究,探讨了颗粒破碎的特性和破碎变形的机理。本文取得的主要新成果有:1.人工模拟堆石料制备方法研究。采用水泥净浆浇筑不同强度的椭球颗粒的方法,成功制备了一种新的人工模拟堆石料。与已有的同类人工材料相比,本文制备的水泥椭球模拟堆石料更加接近天然堆石料的力学性质,且具有初始形状规则和颗粒强度可控的优点。2.人工模拟堆石料颗粒破碎三轴试验研究。采用五种不同颗粒强度的水泥椭球模拟堆石料,针对颗粒破碎特性进行了系列的常规三轴试验,包括完整三轴试验、过程三轴试验、等向固结试验和往复加卸载试验等。利用人工模拟料颗粒可数的优点,对试验后颗粒破碎的情况进行了详细的统计和筛分。3.颗粒破碎特性研究。根据水泥椭球模拟堆石料三轴试验成果,对颗粒破碎的方式、破碎后的粒径分布、破碎率变化过程以及破碎功等颗粒破碎特性进行了系统的分析和探讨,提出了颗粒破碎最优状态线的概念。4.颗粒破碎对堆石体强度和变形的影响机理研究。分析了颗粒破碎对堆石料损伤和压密硬化的双重作用机理,建立了可反映颗粒破碎作用机理的强度计算公式。根据不同颗粒强度模拟堆石料试验结果,定量地分离出了破碎体应变。发现破碎体应变颗粒破碎率之间存在唯一性关系,并可用幂函数进行拟合。5.考虑颗粒破碎影响的弹塑性本构模型。基于沈珠江双屈服面模型,通过引入本文有关颗粒破碎的研究成果,建立了可考虑颗粒破碎特性的堆石料弹塑性本构模型。该模型对堆石料发生颗粒破碎后的力学特性具有更好的适用性。更多还原

【Abstract】 Particle breakage of rockfill materials is serious under high pressure, so the influence of particle breakage on deformation and strength of rockfill can not be ignored in practice. Most of the research works about particle breakage were performed on natural rockfill so far. The triaxial tests of natural rockfill have some disadvantages that particle breakage can not be controlled and particle breakage rate cannot be precisely determined, so it is difficult to conduct such research quantitatively. In order to investigate deeply the mechanism of particle breakage and the influence of particle breakage on deformation and strength of rockfill, a series of triaxial tests were performed by using cement-ellipse-shaped artificial rockfill. The main achievements obtained in the dissertation are as follows.1. A method for preparing artificial rockfill. The ellipse-shaped particles were moulded in various size and strength with cement pastes. Comparing with the existing artificial rockfill materials, the cement-ellipse-shaped artificial rockfill prepared in this dissertation is more simular to the natural rockfill in mechanical properties, and have the merits of regular shape and controllable strength.2. Triaxial tests on the artificial rockfill. A series of triaxial tests including complete triaxial tests, process triaxial tests, isotropic consolidation tests and load-unload cyclic triaxial tests were performed by using artificial rockfill particles with five levels of strength to investigate the characteristics of particle breakage and the mechanism of breakage deformation. By making use of the merits of artificial rockfill, a detailed statistic and sieving analysis of particle breakage was performed.3. Characteristics of particle breakage. Based on the triaxial test results on the artificial rockfill, the characteristics of particle breakage such as the particle breakage pattern, the grain-size distribution, the evolution of breakage rate, the breakage work and so on were analyzed systemically, and the optimizing state line concept of particle breakage was presented.4. Influence of particle breakage on deformation and strength of rockfill. By analyzing the damage and hardening mechanism caused by particle breakage, a formula for evaluating the strength reflecting the breakage mechanism was developed. On the basis of test results of artificial rockfill materials with different particle strength, the breakage volumetric strain of artificial rockfill materials was separated successfully. The test results show that the relationship between breakage volumetric strain and relative breakage rate is unique and can be fitted by a power function.5. A constitutive model considering the influence of the particle breakage. Based on Shen’s double-yield-surface elastoplastic model, a constitutive model considering the influence of the particle breakage was developed by introducing the research findings about particle breakage in this dissertation. The modified model can preferably reflect the influence of particle breakage on the mechanical behaviour of the rockfill materials.更多还原