冻融～加卸载条件下单裂隙岩体疲劳损伤与断裂研究

发布时间：2018-03-06 04:24

  本文选题：循环荷载　切入点：单裂隙岩体　出处：《西安科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来,我国工程建设速度不断发展,更多工程项目涉及寒冷区域。岩体作为地质工程中最主要的部分,均含有自然损伤造成的裂隙,在地下岩体裂隙比较发育的地区,受季节和昼夜交替产生的温度差引起岩体内的裂隙反复冻融。因此,展开对冻融～加卸载反复作用下裂隙岩体损伤演化及断裂特性研究具有重要研究价值。制作具有0°、45°和90°的单裂隙标准试件,通过对单裂隙试件进行10、20、30和40次冻融循环试验,得到不同时期各个试件表面均出现不同程度的片状剥落和龟裂现象;单裂隙角度在相同冻融循环次数条件下所造成的局部化损伤效应随着角度的增大依次减弱;同一角度单裂隙试件随着冻融循环次数的增加局部化损伤效应越明显;冻融循环过程对单裂隙端部局部区域以外产生了近似同等规律的损伤效应。随后对试件进行不同应力水平条件循环加卸载,得到循环荷载条件下滞回曲线,同时对单裂隙岩体宏观模式进行分析得到三种典型的破坏模式,分析了等次冻融循环条件下单裂隙倾角岩体强度。在随后的理论分析中,对试件在冻融过程中的温度进行实时测量,得到冻融过程中温度变化曲线,分析冻胀力演化理论,给出了冻胀力理论表达式。根据岩石疲劳特性和疲劳理论,对单裂隙岩体端部疲劳累积损伤分析,基于断裂力学基本理论,对冻胀力和单轴循环荷载共同作用下的裂纹的扩展机理进行了探讨,提出考虑冻融损伤作用导致裂纹长度的增加和材料性质劣化影响的Ⅰ和Ⅱ型裂纹应力强度因子的计算表达式。利用颗粒流(PFC2D)软件对冻融和加卸载条件下不同单裂隙角度和冻融次数进行模拟分析,结果与室内试验一致。通过冻融～加卸载共同作用下单裂隙岩体试验分析和理论推导相结合,系统分析了单裂隙岩体在该条件下的演化过程,对解决相应寒区工程问题给出了一定的依据。
[Abstract]:In recent years, the speed of engineering construction in our country has been developing continuously, and more engineering projects are involved in cold regions. Rock mass, as the most important part of geological engineering, contains cracks caused by natural damage, and in areas where the cracks of underground rock mass are relatively developed, The cracks in the rock are frozen and thawed by the temperature difference between the seasons and the day and night. It is of great value to study the damage evolution and fracture characteristics of fractured rock mass under repeated freeze-thaw loading and unloading. The single fracture standard specimen with 0 掳or 45 掳and 90 掳is made, and the 10 ~ 2030 and 40 freeze-thaw cycle tests are carried out on the single fracture specimen. The results show that there are different degree of flake spalling and crack phenomena on the surface of each specimen in different periods, and the localized damage effect caused by the single crack angle under the same freeze-thaw cycle times is weakened with the increase of the angle. With the increase of freeze-thaw cycles, the local damage effect of the specimen with a single fracture at the same angle is more obvious. The damage effect of freeze-thaw cycle outside the local area of the end of a single fracture is approximately the same. Then the specimen is subjected to cyclic loading and unloading under different stress levels, and the hysteretic curve under cyclic load is obtained. At the same time, three typical failure modes are obtained by analyzing the macroscopic model of single fractured rock mass, and the strength of rock mass with order crack inclination is analyzed under the condition of equivalent freeze-thaw cycle. The temperature change curve during freezing and thawing process is obtained by measuring the temperature of the specimen in real time, the evolution theory of frost heave force is analyzed, and the theoretical expression of frost heave force is given. According to the fatigue characteristics and fatigue theory of rock, Based on the basic theory of fracture mechanics, the crack propagation mechanism under the combined action of frost heaving force and uniaxial cyclic load is discussed. The expressions of stress intensity factors of mode 鈪，

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