多次爆破开挖中岩石动力学特性与累积损伤效应研究

Taking the blast-induced accumulative damage and deformation instability of surrounding rockmass as the research clue, this project focuses on the evolution mechanism of accumulative damage and the related numerical simulation method of rock subjected to repetitious blast excavations by using a method which combines theoretical analysis, laboratory test and numerical simulation. Considering the dynamic characteristics of rock under impact is the research basis of damage behavior of rock during blasting, the relationship between damage degree and confining pressure, axial pressure as well as energy accumulation & dissipation is firstly explored via the cyclic impact experiment of rock, the determinant criterion of characterizing rock damage degree is established, and the new definitions of rock tensile and compressive damage together with the dynamic constitutive model are also proposed; Subsequently, the spatial and time discretization method of fluid-solid coupling analysis system is explored, and the application modules and user-defined interface which can be used to analyze the coupling of solid and fluid of rock fracture process during repetitious blast excavations are developed on the basis of combining finite element and discrete element method. At last, the field test on the effect of rock accumulative damage under repeated blasting is carried out and further used to validate the above numerical tool along with the damage constitutive model, as thus the irreversible superposition phenomenon of rock damage subjected to frequent explosions can be disclosed in details. The results of this research can provide a theoretic guide and technical support for the correct understanding of the failure mechanism of rock during multiple blast operations and the scientific evaluation of the long-term stability of engineering rock masses, which has a broad application prospects in the engineering fields such as large hydropower engineering and mining engineering, etc.

本项目以围岩爆破累积损伤与变形失稳为研究主线，采用理论分析、实验测试与数值模拟相结合法，致力于多次爆破开挖下岩石累积损伤演化机制及其数值模拟方法。鉴于岩石在冲击作用下的动力特性是研究爆炸荷载下岩石损伤行为的基础，故先通过岩石循环冲击测试，探讨其累积损伤与围压、轴压及能量积聚耗散间关系，建立表征岩石损伤度的判定标准，并以现代力学理论为指导，确立岩石的拉裂、压剪损伤新定义与含损伤动态本构；接着研究流固耦合分析系统的时间与空间离散方法，基于有限元与离散元耦合思路，开发多次爆破作业下岩石流固耦合分析应用模块与用户自定义接口；最后开展重复爆破作用下围岩累积损伤效应的现场试验，并对数值程序进行验证，达到深入揭示频繁爆破产生的不可逆损伤叠加现象。相关成果可为正确认识围岩在多次爆破施工中的破坏机理、科学评价工程岩体长期稳定性等提供理论指导和技术支撑，在大型水利水电工程建设及矿山开采领域具有广阔的应用前景。

项目组采用理论研究、实验测试和数值模拟相结合的方法，开展了多项科研工作，圆满完成了计划书中规定的各项指标，主要工作有：对华山黑云母花岗岩循环荷载下的强度、变形及声发射行为开展研究，比较了不同围压下应力-应变曲线特征和岩样破坏模式，探讨了单轴和三轴循环加卸载过程中声发射振铃计数、能量计数特征与基于声发射振铃计数的损伤机理；基于单轴循环冲击试验，发展出此类岩石在循环冲击荷载下裂纹起裂应力的近似确定方法，较好地解释循环冲击试验中所观测到的现象；对不同围压和轴压下岩样进行了等幅循环冲击测试，探析了相同冲击荷载下承受不同围压的岩样循环冲击应力-应变曲线特征、平均应变率、弹性模量及累积损伤随冲击次数的变化规律；结合单次和重复冲击压缩试验，发现单次冲击下试样动态抗压强度与比能量呈现对数函数关系，而重复冲击下当试样未破坏时应力-应变曲线基本经历弹性加载、损伤演化和峰后回弹等3个阶段。试样破坏时累积比能量越大，其破坏越严重，且应变率曲线由“单峰”逐渐向“双峰”过渡；进行了室外爆破试验，对多次爆破荷载下质点振动衰减规律与累积损伤演化机理进行了探析，并对不同装药量下花岗岩试块的裂纹扩展与断裂形态进行了比较；基于有限元软件ANSYS/LS-DYNA及其重启动技术，数值分析了循环爆破下应力波传播规律、裂纹扩展及其开裂情况；针对爆破加速度零漂信号，采用集合经验模态分解（EEMD）与高低频处理相结合法进行修正，提出了表征修正前后频域平均偏差幅度的修正指数，确定出EEMD法修正爆破零漂信号中白噪声系数的最优取值范围等；对多次循环爆破作用下的岩石损伤累积效应作了数值分析，发现循环爆破载荷下累积损伤演化云图与单次爆破具有相似性，径向裂纹呈交叉放射状，累积损伤演化曲线呈反“S”形，并发现岩石累积损伤增量在径向上呈现出单峰正偏的Weibull分布；对完整岩体和含节理岩体中单孔和双孔爆破问题开展模拟，揭示爆破损伤在完整岩体中的衰减规律，并探究与炮孔斜交的节理对岩体中单孔爆破与双孔爆破中介质损伤演化的影响机理；采用FEM-SPH耦合法对爆破成坑现象进行模拟，取得良好效果。迄今，正式发表带标注论文34篇（SCI收录10篇，EI收录9篇），另有6篇论文网络首发中；获批省部级科技奖励1项、国家发明专利2件，培养研究生16名(毕业9名)。通过积极参与学术会议、邀请国外专家访问等形式，与国内外同行进行了深入交流与合作。