非等温条件下非饱和土变形特性的本构模拟

发布时间：2018-10-14 14:55

【摘要】：作为一种由松散颗粒积聚而成的多孔介质,天然状态下的土体极易发生不可恢复的塑性变形。在很多情况下,这种变形不仅仅是由于外部荷载的改变引起,同时还和吸力及温度变化密切相关。尤其是在一些特殊的岩土工程中,这种表现更为突出。例如,在地热资源开发、高放废物地质处置、城市垃圾填埋场建设运营以及埋热管道建设等众多工程领域中,相应的岩土材料都同时受到外部荷载、水以及热的共同作用,这一特殊环境使得土体的变形特性变得更为复杂。为了更好地认识土体在热-水-力耦合作用下的变形行为,并对其进行定量化的描述,本文基于蔡国庆(2012)所建立的非饱和土热-水-力耦合本构模型对非等温条件下非饱和土的变形特性进行了模拟。通过开展大量的文献调研,首先综述了温度对非饱和土基本性质影响的相关研究,包括试验研究和本构模型,通过对现有研究成果进行总结,指出了现有研究存在的问题和不足：随后,对蔡国庆(2012)模型进行了进一步推导论证,给出了相应的屈服条件、硬化规律及流动法则,并完成了增量本构方程的推导建立;最后,通过编制Fortran计算程序,实现了模型的预测功能,并利用试验数据对模型进行了验证。主要研究成果包括： (1)基于非饱和土热-水-力耦合本构模型,对各向同性条件下吸力和温度对非饱和土变形性质的影响进行了预测和分析。基于建立的考虑温度影响的非饱和土增量本构方程,重点考察模型的固相变形部分,利用Fortran语言编制计算程序,对各向同性条件下非饱和土变形特性进行预测。结果表明：在某一确定温度下,吸力增加引起土体的屈服应力的增大,当温度升高时,吸力对土体的强化作用依然存在：在某一确定吸力下,温度增加引起土体屈服应力的减小,当吸力增加时,温度对土体的弱化作用依然存在。通过模型预测与试验数据的对比,验证了本文所提模型在等向压缩条件下的适用性。 (2)基于非饱和土热-水-力耦合本构模型,对三轴剪切条件下吸力和温度对非饱和土变形性质的影响进行了预测和分析。基于上述本构模型,利用Fortran的语言编制计算程序,对三轴剪切条件下非饱和土变形特性进行预测。结果表明,屈服应力随温度的增加而减小,随吸力的增加而增大。因此,温度的升高对土体有软化作用,吸力的增加对土体有硬化作用。另外,温度越高,土体体积收缩越显著,同样,吸力的增加,也会导致土体体积的收缩更加显著。通过模型预测与试验数据的对比,验证了本文所提模型在三轴剪切条件下的适用性。
[Abstract]:As a porous medium formed by the accumulation of loose particles, the soil in natural state is prone to irrecoverable plastic deformation. In many cases, the deformation is not only caused by the change of external load, but also closely related to the variation of suction and temperature. Especially in some special geotechnical engineering, this performance is more prominent. For example, in many engineering fields, such as geothermal resources development, high-level radioactive waste geological disposal, construction and operation of municipal solid waste landfills, and construction of buried heat pipelines, the corresponding geotechnical materials are subjected to the combined effects of external loads, water and heat at the same time. This special environment makes the deformation characteristics of soil more complex. In order to better understand the deformation behavior of soil under thermal-hydro-mechanical coupling, the deformation behavior of soil is described quantitatively. Based on the thermo-hydro-mechanical coupled constitutive model of unsaturated soil established by Cai Guoqing (2012), the deformation characteristics of unsaturated soil under non-isothermal condition were simulated. Based on a large number of literature studies, this paper first summarizes the relevant studies on the effects of temperature on the basic properties of unsaturated soils, including experimental studies and constitutive models, and summarizes the existing research results. The problems and shortcomings of the existing research are pointed out. Then, the Cai Guoqing (2012) model is further deduced and demonstrated, the corresponding yield condition, hardening law and flow rule are given, and the incremental constitutive equation is established. The prediction function of the model is realized by programming the Fortran program, and the model is verified by the experimental data. The main research results are as follows: (1) based on the thermo-hydro-mechanical coupling constitutive model of unsaturated soil, the effects of suction and temperature on the deformation properties of unsaturated soil under isotropic conditions are predicted and analyzed. Based on the incremental constitutive equation of unsaturated soil considering the influence of temperature, the solid deformation part of the model is investigated, and the deformation characteristics of unsaturated soil under isotropic condition are predicted by using Fortran language. The results show that under a certain temperature, the increase of suction causes the increase of yield stress of soil. When the temperature increases, the reinforcement of soil by suction still exists: under a certain suction, The soil yield stress decreases with the increase of temperature, and the weakening effect of temperature on soil remains when the suction increases. The applicability of the proposed model under the condition of isotropic compression is verified by comparing the model prediction with experimental data. (2) based on the thermo-hydro-mechanical coupling constitutive model of unsaturated soil, The effects of suction and temperature on the deformation properties of unsaturated soils under triaxial shear are predicted and analyzed. Based on the above constitutive model, the deformation characteristics of unsaturated soil under triaxial shear conditions are predicted by using Fortran language. The results show that the yield stress decreases with the increase of temperature and increases with the increase of suction. Therefore, the increase of temperature can soften the soil, and the increase of suction can harden the soil. In addition, the higher the temperature, the more significant the volume shrinkage of soil, the same, the increase of suction will lead to more significant shrinkage of soil volume. The applicability of the proposed model under triaxial shear condition is verified by comparing the model prediction with experimental data.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU43

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