【作者】 万玲；

【导师】 彭向和；

【作者基本信息】 重庆大学 ， 固体力学， 2004， 博士

【摘要】 流变是岩石材料的重要力学特征,许多工程问题(采矿、石油开采、能源和放射性核废料的储存、边坡及地下构筑物的稳定性等)都与岩石的流变特性有密切关系。然而,随着各类岩土工程建设规模的扩大,以及对岩石类材料与工程特征认识的深入,在描述和处理材料的时间效应及其流变属性方面,尽管取得了重要的进展,但仍存在许多亟待解决的问题。 本文对盐岩和泥岩试件进行了系统的蠕变试验,根据非经典塑性理论建立了岩石类材料的粘弹塑性损伤本构模型,发展了相应的数值分析方法。对泥岩和盐岩在不同温度常规三轴应力状态下的蠕变损伤特性进行了分析。同时对素混凝土、纤维增强混凝土在复杂加载史下的损伤行为和寿命进行了计算。在实验方面,为了有效地对岩石进行蠕变试验,自行研制了一套能进行常规三轴蠕变试验、并能考虑温度影响的岩石三轴蠕变仪。该装置结构简单、操作方便。可提供 60kN 的轴向压力、80MPa 的围压和 150°C 的最大加热温度。利用所研制的三轴蠕变仪,对泥岩进行了系统的单轴和三轴蠕变试验,试验中考虑了轴压σ1 和围压σ3 对蠕变的影响。结果表明,当围压σ3 一定时,轴向应力σ1 增加,蠕变加快,在稳态蠕变阶段的应变率增大,试件的寿命缩短。而当应力差?σ =σ1–σ3 保持不变时,围压σ3 增加,蠕变减慢,稳态蠕变阶段的应变率也减小,试件的寿命增加。 通过对盐岩进行的不同温度和应力水平下的三轴蠕变试验表明,在围压σ3 和温度 T 不变时, 轴压σ1 对蠕变和蠕变率的影响与泥岩相同。随着温度的增加,蠕变应变增大,稳态蠕变应变率也相应增大。 研究表明岩石的蠕变特性除与应力水平、温度、载荷的加载方式有关外、还与岩石结构、湿度、岩石材料本身所具有的粘性性质和赋存条件等因素有关。 在理论方面,根据连续介质力学基本理论,基于含内变量的不可逆热力学和连续介质损伤力学,通过在不可逆应变和牛顿时间所构成的空间中合理的定义广义时间、引入四阶各向异性损伤张量,建立了岩石类材料的粘弹塑性损伤本构模型。该模型能够考虑复杂应力状态下材料的响应特性,各向异性损伤及其损伤的方向特征,静水压力和温度的影响,基于不同机制的不可逆变形间的相互作用,劣化规律和失效模式等。能对剩余强度、刚度、剩余寿命等进行分析和预测。重要的是,所建立的模型不以屈服面的存在为基本前提,但可获得含屈服面的情形作为其特例;在蠕变变形与塑性变形的描述方面,不采用分离型的方法分别对他们进行描述,而将两种变形均视为由热激活导致的不可逆变形并在此基础上发展 I<WP=6>中文摘要统一的本构描述,从而更有效地描述两者间的相互作用。 发展了不含屈服面的粘弹塑性损伤本构模型的数值分析方法,对泥岩和盐岩的蠕变过程进行了数值模拟,计算结果与试验结果吻和较好。表明所发展的模型能较好反映应力水平和温度对岩石蠕变特性的影响。计算了损伤变量的演化规律,得到了与实际相符合的结果。 弹塑性损伤本构模型是所发展本构模型的特殊情形,用它对素混凝土在单轴循环加载下和三轴复杂加载史下的响应进行了描述,计算结果与实际相符,验证了模型的正确性。同时对随机分布短纤维增强混凝土在三轴载荷下的响应和在循环应力下的响应及寿命进行了计算,理论模型计算结果与试验结果都表明,纤维体积分数增加,损伤速度减缓、材料的承载能力增大、寿命提高。因此模型能较好反映混凝土在复杂加载条件下的基本特征。更多还原

【Abstract】 Rheology is one of the most important mechanical characteristics of rock androck-like materials, which is related to mining, oil extraction, storage of resources andradioactive wastes, underground and civil engineering, etc. Although great progress hasbeen made in the description of the rare-dependent effects and rheological properties inthe past decades, there are still a lot of problems remained unsolved. In this dissertation, the creep of salt rock and claystone is systematicallyinvestigated with a specially designed testing device. A visco-elastoplastic damageconstitutive model is proposed for rock and quasi-brittle rock-like materials. Thecorresponding numerical algorithm is developed the creep and damage of the salt rockand claystone subjected to longitudinal stress under different confined pressure andtemperature is simulated. and the nonlinear behavior and damage of concrete subjectedto complex triaxial loading histories are analyzed. In order to make the creep experiment of rock and rock-like materials moreefficiently, a device is developed, which can provide 60kN of longitudinal load, 80MPaof confined pressure and temperature ranged from room temperature to 150°C. The uniaxial and triaxial experiments on the creep of claystone are performed, andthe effects of axial stress σ1 and confined pressure σ3 on the creep are investigatedsystematically. It can be found that for constant confined pressure, creep develops faster,the steady-state creep strain rate increases, and the life is reduced, with the increase ofaxial stress. If the stress difference ?σ =σ1–σ3 is constant, creep strain and steady-statecreep strain rate decrease and the life increases with the increase of confined pressure. The triaxial experiments on the creep of salt rock are also performed, and theeffects of axial stress σ1, confined pressure σ3 and temperature on the creep areinvestigated. It shows that if confined pressure σ3 and temperature T are constant, theeffect of axial stress σ1 on creep and creep rate is similar to that of clay stone. With theincrease of temperature, the creep strain increase and the steady state creep strain rateincreases accordingly. It indicates that the creep properties are related to the state ofapplied stress, temperature, loading history, and the properties of rock and rock-likematerials. Making use of irreversible thermodynamics with internal variables and the conceptof continuum damage mechanics, a visco-elastoplastic damage constitutive model is III<WP=8>英文摘要proposed by introducing generalized time defined in the space of irreversible strain andNewtonian time, taking into account the anisotropic nature of the micro-defects in rockand rock-like materials. The anisotropic evolution and unilateral effect of damage aswell as the effect of hydrostatic pressure and temperature can be taken into account inthe proposed model. The interaction between irreversible deviatoric and volumetricdeformation, for instance, the shear compaction and shear dilatation at differentconfined pressure and different phase of deformation, can also be considered. Theproposed model does not use the concept of yield surface and the correspondingloading/unloading rule, and describe unitedly the elastic, inelastic and viscous behaviorof materials, which may bring convenience to the corresponding numerical analysis.The proposed model is also a united description for the coupled viscous and plasticdeformation of materials, i.e., it regards both viscous and plastic deformation asirreversible deformation induced by thermal activation. The corresponding numerical analysis is developed, and the creep, inelastic anddamage behavior of some rock and rock-like materials are analyzed. It shows that thecalculated results agree well with the experimental observation. The influence of stressleveland temperature act on the creep can be well described withthe model. The elastoplasticit更多还原