【作者】 张树光；

【导师】 张向东；

【作者基本信息】 辽宁工程技术大学 ， 工程力学， 2004， 博士

【摘要】 通过对风积土的含水量、密度、比重等指标进行测试、颗粒分析和粒度分布分形性质的研究，系统地研究了风积土的物理性质，对物理参数的分析表明：风积土的颗粒成分中细颗粒为主要颗粒，其结构相对致密，浸水后不具有明显的湿陷性，初步推断风积土易发生冻胀，且其粒度分布具有明显的自相似性。 通过对不同冻结温度和不同初始含水量的单轴强度试验，得出风积土的破坏形式为：高温状态或含水量较小时表现为塑性破坏，低温状态或含水量较大时则表现为脆性破坏，并采用分形插值理论获得了冻风积土单轴状态的应力—应变曲线；通过不同冻结温度、不同围压下的三轴强度试验和三轴蠕变试验，在理论分析的基础上，回归得出了冻风积土的三轴本构关系和三轴蠕变方程。 利用SYC—2型非金属超声波检测仪设计了动态损伤监测系统，获得了冻风积土的抗压强度、抗拉强度、弹性模量等物理参数和声波参数的关系；实现了对冻风积土损伤的动态监测，基于损伤和分形理论建立了损伤变量和分形维数随应力变化的数学经验表达式。 进行了风积土在不同冻结温度、含水量、干密度等条件下的水分迁移试验，建立了水热耦合条件下水分迁移的数学模型，获得了试样的温度分布规律，土中的含水量变化在一定的含水量范围内，会随着时间的延长、温差的增大和干密度的减小而增大；通过水分迁移过程的扫描电镜微观分析表明：水分的迁移加剧了土颗粒的不均匀分布和团聚现象，同时，土颗粒的不均匀分布和团聚又促成了水分迁移通道的形成，更有利于水分的迁移，因此，土颗粒的重新排列与水分迁移是相互作用的。 自行设计了风积土在水分、温度、荷载作用下的冻融试验系统，进行了封闭和开敞系统的冻融试验，结果表明：在封闭系统中，应力的存在对整个冻胀过程的冻胀量变化趋势并没有显著的影响，主要影响土样的最终冻胀量：外界水的补给使得冻胀量增加，冻胀过程中的周期性或循环性更加明显，幅值的变化(起伏)也更显着；在有外加荷载的情况下，融沉量的变化在整个过程中相对较平稳，由于外荷载对融沉和土颗粒重新调整的促进作用，初期的融沉发展速度要较无外加荷载时快，但最终的融沉值要较无外加荷载时小。 通过对风积土的水分迁移试验，得出在靠近冷端的一定深度内，冻结后的含水量并没有持续增加，反而有减小的趋势，在此称之为人工冻结试验的“顶端效迁宁工程技术大学博卜学位论文应”，这一点在数值计算中是无法考虑的;冻融试验表明温度的降低一方面会造成冻胀量的增加，同时温度梯度增大对水分迁移的充分性又是不利的，因此在研究温度对冻胀量的影响以及在冻胀量的评价和相关数学模型中，应从温度和温度梯度两一方面来考虑，在此称之为“温度效应”现象。 通过理论研究和实验分析，得出风积土的冻胀曲线具有良好的自相似性，即提出冻胀曲线具有分形特征，并基于分形理论建立了冻胀曲线的分形优化方法和在非等温条件下风积土冻胀量的预测方法。更多还原

【Abstract】 The physical property of aeolian soil is studied systematically by testing moisture content, density, specific weight etc., grain analysis and fractal character. The physical parameters show that the thin grain is main grain in the grain of aeolian soil, and its construction is opposite and fine. Aeolian soil does not have the obviously wet sinking after soaking in water, so it has the property of frosting heave. At the same time, its grain distribution has obviously self-similarity.The single-axle strength experiments with different frosting temperature and moisture content are tested, which obtains the breakage form of aeolian soil as: it presents plastic breakage under the condition of high temperature and low moisture content, otherwise, it presents brittle breakage. Based on the theory of fractal interprolation, the - curve of aeolian soil is obtained. By testing the tri-axle strength and creep experiments with different frosting temperature and round press, the tri-axle constitutive function and creep function are obtained using regression method on the basis of theory analysis.The dynamic damage test system(DDTS) is designed by making use of SYC-2 nonmetal supersonic test meter. The relations between compressive strength, tensile strength, elastic modulus, etc. and wave parameter in frozen aeolian soil is studied using DOTS. The TTDS realizes dynamic test of damage in frozen aeolian soil, based on damage and fractal theory, the experience function of damage variable and fractal dimension with stress are obtained.The moisture migration of frosting aeolian soil is tested under the condition of different frosting temperature, moisture content and dry density. A mathematic coupling model of moisture and heat in the process of moisture migration is established, and the rule of temperature distribution is obtained. The change degree of moisture content is in direct proportion to time and temperature, and it is in inverse to dry density. The results of SEM in the process of moisture migration show that the moisture migration aggravate the phenomenon of uneven distribution and reunion in soil grain, at the same time, the phenomenon of uneven distribution and reunion in soil grain also help to form passageway of moisture migration, which is beneficial to moisture migration. Therefore, the rearrange of soil grain and moisture migration act each other.The system of frosting-sweal experiment acted on moisture, temperature and load is made by oneself, and the frosting-sweal experiments of closed and unclosed system are done. In closed system, the stress don’t affect obviously the change tendency of frosting heave in the frosting and sweal process, mainly the final frosting heave. In the unclosed system, the outside water makes the frosting heave increase, and the periodicity and scope of frosting heave is more obvious. If the specimen is loaded, the change of sweal is considerably steady. Because of promotion action of load to sweal and rearrange of soil grain, the beginning sweal velocity is quicker than that of unload, but the final sweal value is little.By testing the moisture migration of aeolian soil, in a certain depth near cold end, the moisture content of frozen soil not only increase, but decrease. Therefore, this phenomenon is defined as "End Effect" in the paper, and it is unable to be considered in the numerical calculation.The result of frosting-sweal experiment show that low temperature leads to increase of frosting heave, meanwhile, the increase of temperature gradient is harmful to adequacy of moisture migration. According to the above, both temperature and temperature gradient should beconsidered for researching the influence and estimation of temperature to frosting heave and numerical model. The above phenomenon is defined as "Temperature Effect" in the paper.From theory and experiment analysis, the research make known that the frost heave curve has well self-similarity, namely the curve of frosting heave has fractal character. Based on fractal theory, this paper proposes fractal optimi更多还原