岩石动态破坏的多尺度颗粒数值流形法研究

The numerical manifold method (NMM) has been a useful tool in rock mechanics, especially in rock dynamics, to model the continuous and discontinuous behaviors of rock materials and jointed rock masses in a unified framework. One of the main challenges in NMM is the complex geometrical operations between different types of polyhedrons in contact analysis. Besides, NMM lacks the ability to take the heterogeneity and complex microstructure of rock materials into consideration. Attempting to tackle these issues, a multiscale particle-based numerical manifold method will be developed as an extension by introducing the particle concept into NMM. First, we intend to develop the contact model between particles, as well as an efficient contact-searching algorithm for particles, in order to improve the performance of NMM in contact analysis. Then, by incorporating the random distribution of material properties and strength parameters as well as a failure criterion for micro-cracks, we will apply the developed numerical model to study the effect of heterogeneity of rock on its rate-dependent behavior under dynamic loads. Besides, we will study the effect of the microstructure of rock materials using digital images of rock specimens and particle elements in the developed method. We are also going to develop a coupled method, by combining the conventional NMM and the multiscale particle-based numerical manifold method, for the sake of higher computation efficiency. This project will help to develop a numerical tool that has the ability to simulate the pre- and post-failure behavior of rock materials and the capacity to study the mechanism of dynamic rock fracturing and to simulate rock engineering problems.

大量不规则块体相互接触的检测与运算过于繁琐是数值流形法NMM应用于大型岩土工程问题的主要制约因素。此外，在考虑岩石材料非均匀性及内部矿物分布方面的欠缺也使该方法无法探索岩石动态特性的影响因素及机理。本项目拟通过将数值方法中的颗粒概念引入数值流形法来解决这些问题。首先，通过引入颗粒单元发展一种基于颗粒的多尺度数值流形法,并开发颗粒接触理论模型和接触对高效搜索算法，解决传统数值流形法中多边形单元接触复杂的难题。其次，通过引入弹性参数和破坏参数随机分布以及颗粒单元尺度上的动态问题微裂纹生成及扩展准则，填补数值流形法对岩石材料非均匀性研究的空白。此外，利用数字图像处理技术构建包含内部微观结构的岩石材料数值模型，并依此发展多尺度数值流形法与传统流形法的耦合模型。最终，形成一套能够对岩石动态破坏过程进行完整分析的数值工具，该工具可用于岩石动态破坏机理的研究以及岩石工程动力稳定性问题的分析。

本项目以岩石材料和岩石工程中广泛存在的动态破坏机理为主要研究对象，通过将数值计算方法中的颗粒概念引入传统数值流形法，发展了一种基于颗粒的多尺度数值流形法，并依此进行自主软件程序代码编写。颗粒数值流形法简化了数值流形法中多边形块体的复杂接触问题，并且实现了对连续体内微裂纹萌生与发展的模拟。同时，还发展了颗粒数值流形法与传统数值流形法的耦合算法。此外，利用块体离散元法对岩石矿物微观非均匀性对岩石材料动态力学特性的影响进行了数值研究。最后，将本项目提出的颗粒数值流形法应用于岩石爆破、切割等动态破坏问题中。结果证明，颗粒数值流形法能够对岩石材料的裂纹萌生、扩展和岩石块体的破碎、接触进行完整的动力学数值模拟，可被用作对岩石/岩体动态破坏过程完整分析的数值工具。