【作者】 尚涛；

【导师】 倪万魁；

【作者基本信息】 长安大学 ， 地质工程， 2007， 硕士

【摘要】 压实黄土就是采用一定的压实功能和方法(如碾压法或强夯法),把具有一定级配、含水量的松散的黄土压实到具有一定强度的土层,压实黄土对道路稳定性意义重大,压实黄土的受力过程也是受损伤的过程。损伤理论是经典的固体力学理论的发展和补充,既反映材料微观结构的变化,又能说明材料宏观力学性能的实际变化状况。把损伤与压实黄土相结合,研究压实黄土的损伤特性是本文的主要内容。首先,对压实前后的土样做了颗粒分析和扫描电镜观察,分析压实黄土结构的变化,得知压实黄土中颗粒变细,大孔隙明显减小,微结构由絮凝状微胶结结构和支架大孔微胶结结构变为镶嵌结构和叠置结构,土体结构变密;统计压实黄土基本物理力学指标的变化,分析了压实黄土的应力应变关系,得知压实黄土性状更加完善;通过对压实黄土结构和性状的分析,得出压实黄土的损伤实质宏观上表现为应力作用或含水量变化情况下,塑性区的产生和发展;微观上主要是新结构中小颗粒间的凝聚力和阻力不足以抵抗该点应力时候,土体内部发生的从无到有、从小到大的不可恢复的结构破坏。其次,损伤门槛值是压实黄土开始损伤的起点,通过三轴试验和原位载荷试验,可以找到损伤门槛值,并定量分析研究了压实黄土的损伤门槛值与夯击能、临塑荷载、含水量、压实度和固结压力等之间的关系,并分别拟合出关系公式。最后,选择了附加应力作为损伤变量参数,建立了压实黄土的损伤演化方程,并应用到路基最终沉降计算中去,找出各深度压实黄土的损伤门槛值,计算出损伤变量,再进行考虑损伤的沉降计算,然后与传统计算和有限元模拟计算相比较,得出了考虑损伤更符合实际情况的观点,更说明了考虑损伤的对压实黄土研究和工程应用的意义。更多还原

【Abstract】 Compacted loess is adopted certain compact function and method (such as rolling the law or strong rammer law), and is compacted by the loose loess of some gradation, some moisture into the soil layer with certain intensity. The compacted loess means great to stability of the road. A course of stress is also a course of damage to the compacted loess. Damage theory is a development and supplement to the classical solid theory of mechanics, which is not only lead to crack initiation and final fracture, but also induce progressive material deterioration. Combining damage with compacted loess and researching in the damage characteristic of compacted loess is a main content herein.Firstly, changes of structure of the intact loess and the compacted loess are contrasted by the way of grain-analysis and SEM. It is learnt that the grain became thinner in the compacted loess, the large hole was obviously reduced, the flocculate cline-cementation structure and plank-macrospore cline-cementation structure turns to be embedded structure and pile-up structure, and the structure of loess becomes compacted; It is learnt that compacted loess properties are more complete by counting the change of the basic physics mechanics index and analyzing the stress-strain relation of compacted loess; Through the analysis to structure and property of compacted loess, we can know that the damage essence of compacted loess is shown as production and development of the plasticity district under stress function or water content change in macroscopic side; and the irrecoverable destroy in structure from nonexistence to existence, from small to large happens within the soil when the cohesiveness and resistance among the granules are not enough to resist the stress in new structure in microcosmic side.Secondly, initial damage threshold is a starting point of compacted loess damage which we can find through triaxial apparatus and load test, and we analyze and research the relation among the initial damage threshold of the compacted loess with compact function, the critical edge load, water content, degree of compaction and consolidation pressure , etc, and fit separately out the relation formula.Finally, we choose additional stress as the variable parameter of damage variable, set up the damage evolvement equation of compacted loess, apply it to the final settlement calculation of the subgrade, find out the initial damage threshold of every deep in compacted loess, calculate damage variable, put up the settlement calculation while the damage is considered, compare with simulation of finite element and tradition, educe the view that it is according with the actual conditions even more while damage is considered, explain the meaning of the consideration of damage to the research of compacted loess and application of project.更多还原