【作者】 贾宇峰；

【导师】 林皋； 迟世春；

【作者基本信息】 大连理工大学 ， 结构工程， 2008， 博士

【摘要】 粗粒土具有压实性能好、填筑密度大、沉陷变形小、透水性强以及抗剪强度高等工程特性,广泛应用于土石坝、公路、铁路、机场、堤坝、房屋地基等建筑工程中。粗粒土在高应力水平下容易发生颗粒破碎,颗粒破碎直接改变土体结构,对土体的峰值强度、内摩擦角、剪胀性、渗透系数等工程特性均产生影响。随着高土石坝坝高的不断增加,作为主要筑坝材料的粗粒土承受的应力也越来越大,粗粒土的颗粒破碎现象则愈加显著。而传统的粗粒土本构模型并不考虑土体的颗粒破碎,已经不适合描述高应力水平下粗粒土的应力应变关系。本文在土体的能量平衡方程中引入颗粒破碎耗能,进而根据能量方程建立了考虑颗粒破碎的粗粒土本构模型。论文根据堆石料的三轴试验成果,研究了粗粒土三轴剪切过程中的颗粒破碎规律和破碎耗能,提出了相关计算公式。并结合三轴试验,根据剪切过程中的能量平衡关系,建立了考虑颗粒破碎影响的摩擦系数公式,确定了模型参数,验证了模型的有效性。论文研究了破碎参量的合理表达方式,并拟合试验数据,计算得到了破碎耗能与破碎参量的关系式。将破碎耗能引入剪切过程中的能量平衡方程,采用关联流动法则,推导得到了考虑颗粒破碎的屈服函数。研究确定了硬化规律,建立了本构模型。采用变异粒子群优化算法拟合试验数据,确定了模型参数。通过与试验曲线比较,认为提出的模型能够很好地反映粗粒土的应力-应变-体变关系。粗粒土剪切特性不仅受颗粒破碎的影响,而且受其内部状态的影响。针对粗粒土的这一特点,论文建立了非相关联流动法则本构模型。采用Pender建立的等应力比屈服函数描述粗粒土的剪切屈服特性,并根据考虑颗粒破碎耗能的能量平衡方程推导流动法则。采用Chavez提出的v-p平面的临界状态线,定义当前孔隙比与当前应力对应的临界孔隙比之差作为状态参量。在Wood建立的硬化规律中引入破碎耗能参量和状态参量,描述土体的应变软化现象,建立同时考虑颗粒破碎和内部状态影响的粗粒土本构关系。为了弥补相关联流动法则本构模型无法描述粗粒土状态依赖特性的不足,通过建立模型参数与初始状态参量之间的联系,将内部状态对剪切特性的影响引入所建立的相关联流动法则本构模型。采用Ishihara提出的临界状态线,计算初始状态参量。建立初始状态参量与破碎参量的参数关系式,以及初始状态参量与硬化规律参数的关系式,并拟合三轴试验曲线确定关系式参数。计算不同初始状态下的三轴曲线,验证模型的有效性。计算结果表明,修正后的本构模型,可以描述粗粒土在不同初始条件下的剪切特性。更多还原

【Abstract】 The coarse granular soil is applied widely in rockfill dam, high way, railway, aerodrome and dyke, because of the engineering properties such as suitable compactibility, high hydraulic permeability, high density, high shearing strength, and small settlement. The coarse granular soil is susceptible to particle breakage in high compressive strength, which modifies its structure directly, influencing its dilatancy, friction angle, strength and permeability. With the height of the rockfill dam increasing, the coarse granular soil, which is the main material in dam engineering, suffer higher stress. Therefore the particle breakage of the coarse granular soil gets increasingly notable. The traditional constitutive model, incorporating no influences of particle breakage, is not appropriate to describe the stress and strain of the coarse granular soil under the high stress. In this paper, the particle breakage energy is incorporated in the energy formulation, on which the constitutive model for the coarse granular soil incorporating particle breakage is developed according to the energy fomulation.In this paper, the particle breakage rule and breakage energy are studied during triaxial shearing, on which the associated equation is established. Combined with the triaxial test, the friction coefficient formulation incorporating particle breakage is developed according to the energy balance during shearing, which determines the model parameters and verifies the correction of the model.The breakage parameters are studied and the test data are simulated in this paper, on which the relationship of breakage energy and breakage parameters is established. The breakage energy is introduced in the energy balance formulation during shearing. And the yield function is deduced with the application of associated flow rule. The hardening rule is developed according to triaxial test result, on which the constitutive model is developed. The parameters of the model are determined by the mutation particle swarm optimization algorithm according the triaxial test results. The model developed is proved to reflect the stress-strain-volume strain relationship comparing with the test curve.The shearing features of coarse granular soil are influenced not only by particle breakage but the inner states, on which the unassociated flow rules constitutive model is developed in this paper. With the adoption of the equal stress ratio yield function developed by Pender, the shearing yield features are described. And the flow rules are deduced according to the energy balance equation incorporating particle breakage energy. With the critical state line in v-p plane developed by Chavez, the difference between the current void ratio and the critical state void ratio corresponding to the current stress is determined to be the state parameter. The breakage energy and state parameters are introduced in the hardening rules developed by Wood, on which the strain-softening behavior of the soil can be described, and the coarse granular soil constitutive relationship incorporating the influence of the particle breakage and the inner state is established.In order to make up the associated flow rules constitutive model lacking in describing the state-dependent features, the relationship between model parameters and initial state parameters is developed, and the influence of the inner state on the shear features is introduced in the associated flow rules constitutive model developed. The initial state parameters are calculated with the critical state line established by Ishihara. Therefore, the relationship between initial state parameters and breakage parameters, and the relationship between initial parameters and hardening parameters are developed, which are determined by the triaxial test curve simulation. The triaxial curves in different initial states are calculated, verifying the validation of the model. The calculation results indicate that, the constitutive model developed can describe the shearing features of coarse granular soil in different initial conditions.更多还原