【作者】 相彪；

【导师】 林皋； 迟世春；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2009， 博士

【摘要】 堆石料作为一种常用的工程建筑材料,由于具有强度高、压实性好、成本低和性质稳定等优点已在土石坝工程中得到广泛应用。随着土石坝设计坝高的不断增加,筑坝堆石料的受力情况变得更为复杂,而坝料的应力应变关系也已成为工程设计中所必须了解和掌握的基本性质之一。目前的室内试验通常是在围压不变条件下进行三轴剪切使试样达到破坏状态,其应力路径与堆石料在坝体施工和蓄水过程的实际应力路径有所不同,而采用三轴试验结果整理得到的本构计算模型进行坝体应力应变分析时其结果与实测数据仍存在一定差距,其主要原因就是所用的本构模型通常不能很好地反映应力路径的影响。基于上述问题,本文进行了筑坝堆石料应力路径本构关系研究,主要内容如下:(1)研究了粗粒土的工程特性。在对土体应力路径最新研究成果进行总结评述的基础上,论述了堆石料应力路径本构模型研究的必要性。针对坝体堆石料的实际应力路径,介绍了模拟坝体填筑期的等应力比路径,以及蓄水期转折应力路径下的三轴排水试验。根据试验结果整理了应力应变关系曲线,分析了堆石料在不同形式应力路径下的应力与变形特性。(2)采用应变解耦分析的办法,分别考虑p、q应力对体应变和剪应变的影响,在兼顾实际应用的前提下,提出了等应力比路径四模量增量非线性模型和三模量增量非线性模型,两模型都适于描述堆石料在等应力比路径下的应力应变关系。(3)根据堆石料应力路径试验结果,分析了经典的邓肯-张模型的应力路径适用性问题,并提出了一个新的应力路径本构模型。该模型根据堆石料在不同应力路径下的变形规律性,对应力路径进行合理分区,构建了不同路径分区下合适的本构柔度矩阵。新模型构造简单,能充分考虑应力路径的影响。(4)对Gudehus-Bauer亚塑性本构模型进行了适当改进,使之适于描述堆石料复杂应力路径下的应力应变关系。采用变异粒子群优化算法确定了模型参数,并取得了较好的效果。为了考虑应力路径的影响,分析了Gudehus-Bauer亚塑性模型参数与瞬时应力路径之间的关系,将应力路径影响引入亚塑性本构模型。计算结果表明,改进的Gudehus-Bauer亚塑性模型能够较好地模拟堆石料的主要力学特性,适于堆石坝的应力应变分析。更多还原

【Abstract】 Rockfill,as a common construction material in civil engineering,is widely used in the earth-rock dam engineering for its advantages of high strength,good compactibility,low cost and stable properties.With the increasing of design height in earth-rock dam,the stress state of rockfill becomes more complex,and the stress-strain relations of rockfill have already become one of the basic properties that must be deeply understood in the engineering design. At present the laboratory tests are usually conducted in triaxial shear state with constant confining pressure until the samples reach the failure state,the stress path of which is quite different from that of rockfill during dam construction and reservoir filling,and the results in the stress-strain analysis of dam body using the calculating constitutive model proposed by triaxial test results have differences with the measured data in some degree.The main reason of the problem is that the constitutive model adopted can not fully take the effect of stress path into account.Based on the above problems,the paper carries out the study on constitutive relations of dam rockfill considering the effect of stress path.The main work is as follows:(1) The engineering characteristics of coarse grained soil are studied.Based on the latest research on stress path summarized,the necessity of studying on the stress-path constitutive model of rockfill is to be considered.For simulating the actual stress path of dam rockfill, drained triaxial tests under two types of stress path are introduced,which are the stress paths of constant stres ratio during dam construction and the transitional stress paths upon reservoir filling.According to the measured stress-strain relation curves,the stress and deformation characteristics of rockfill under different forms of stress path are analyzed in detail.(2) Employing the method of decoupling analysis on strain variable,the coupling effects of mean principal stress p and shear stress q are taken into account.On the premise of considering practical application,the incrementally nonlinear models of rockfill under the stress paths of constant stress ratio including four modulus and three modulus are proposed respectively.The two proposed models are suitable for describing the stress-strain relations of rockfill under the paths of constant stress ratio.(3) Based on the stress-path test results of rockfill,the applicability of classical Duncan-Chang model in stress-path analysis is discussed,and a new stress-path constitutive model is proposed.According to the deformation regularity of rockfill under different stress paths,the stress paths are divided into several parts and the constitutive compliance matrixes in each stress-path partition are presented.The proposed model is simple and can fully reflect the effect of stress path.(4) Referring to the Gudehus-Bauer hypoplastic constitutive model,the model is improved appropriately to describe the stress-strain relations of rockfill under complex stress paths.The mutation particle swarm optimization algorithm is employed to determine the constitutive parameters and it is proved to present good performance.For considering the effect of stress path,the relations between the constitutive parameters in Gudehus-Bauer model and instantaneous stress path are analyzed and the stress-path factor is integrated into the hypoplastic constitutive model.The calculation results show that the improved Gudehus-Bauer hypoplastic model can well predict the main mechanical properties of rockfill, which is suitable for the stress-strain analysis on rockfill dam.更多还原