摘要
二元介质模型已成功用于模拟未冻结岩土材料,比如岩石、均质或各向异性结构性土、超固结黏土、堆石料以及黄土。类似地,为了探讨冻土的应力应变关系,此处引入二元介质模型来模拟其应力应变关系。基于岩土破损力学理论框架和二元介质模型概念,将饱和冻结粉土抽象成具有强胶结特性的胶结元（冻土骨架）和无胶结特性的摩擦元（融土骨架）,胶结元在一定围压下会产生压碎和压融现象,随围压的增大逐步破损并向摩擦元转化,二者共同承担外荷载。在-6℃和0.3~15.0 MPa围压下对冻结粉土进行了一系列低温三轴压缩试验,结果表明：随变形的增大,应力应变曲线均呈三阶段变化,分别是线弹性阶段、弹塑性阶段和应变软化阶段;强度随围压的增大呈先增大后减小的趋势,极限强度对应下的围压称为临界围压,且临界围压下的软化现象最不明显。通过细观角度运用二元介质模型概念探讨了冻土变形破损机理,在非均质材料均匀化理论基础上建立了冻土二元介质模型,讨论了破损率函数演化规律。理论与试验结果对比表明,所建立的模型可以较好地模拟冻土的应变硬化和软化现象。
The binary medium model （abbreviated as BMM） is suitable for unfrozen geomaterials, such as rock, isotropic or anisotropic structured soils, overconsolidated clay, rockfill materials and loess, and has a good accuracy and satisfactory applicability. Similarly, in order to investigate the stress-strain relationship of frozen soils, the BMM is introduced and employed to simulate the deformation characteristics. Based on the theoretical framework of breakage mechanics for geomaterials and the concept of BMM, the saturated frozen silt soils are conceptualized as the binary medium consisting of bonding blocks with strong bonding （the frozen soil skeleton） and frictional elements without weakened bonding （the melted soil skeleton）, and the bonding elements will be crushed, melted and gradually transformed to frictional elements with the increasing confining pressure during the loading process, resulting two of the bonding blocks and weakened bands bear the external loads, collectively. A series of cryogenic triaxial compressive tests are conducted at -6~C under confining pressure of 0.3 to 15.0 MPa, and the following test results demonstrate that the stress-strain curves behave three varying stages with the increasing axial strain, which are the initial linear elastic stage, elasto-plastic stage and strain softening stage, respectively. The strength of frozen soils increases first and then decreases with the further increase of confining pressures. The critical confining pressure corresponds to the peak strength for different test curves, under which the strain softening phenomenon is less obvious. From a mesoscopic point of view, the deformation and damage mechanisms of frozen soils are investigated based on the concept of binary medium, and the stress-strain formulation is established on the basis of the homogenization theory of the concept of binary medium, and the stress-strain formulation is established on the basis of the homogenization theory of the heterogeneous materials. Finally, the evolution of breakage function is analyzed and discussed through determination of the fitting parameters. The comparisons between theoretical and experimental test data demonstrate that the proposed binary medium model has a satisfactory applicability for frozen soils to simulate strain hardening and softening phenomenon.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2018年第1期82-90,共9页
Chinese Journal of Geotechnical Engineering
基金
中国科学院“百人计划”项目
国家自然科学基金项目(41771066)
关键词
岩土破损力学
冻结粉土
二元介质模型
破损机制
胶结元
摩擦元
breakage mechanics for geomaterials
frozen silt soil
binary medium model
breakage mechanism
bonding element
frictional element
