Development of a Rockbolt Support Element for Discontinuous Deformation Analysis

CMS-0201577PI：Mary MacLaughlin Institution：Montana TechTitle：“用于非连续变形分析的锚杆支撑单元的开发”摘要：本研究项目的主要目标是开发一种能够模拟实际锚杆行为的锚杆支撑单元，特别是对数值模拟至关重要的锚杆和岩石之间的非线性运动。非连续变形分析(DDA)具有几个独特的功能，使其成为开发锚杆单元的完美候选者，该单元能够以比以前更高的真实性和准确性来表征锚杆行为。DDA是一种隐式离散元方法，它已经有能力模拟任何不规则形状的块，接触例程是专门设计的，可以有效地捕获具有凸顶角和凹顶角的块之间的接触。该方法考虑了接触处存在的摩擦力、内聚力和拉力，并允许块在不穿透的情况下滑动、分离和撞击。锚杆单元将被实现为具有与典型锚杆一致的特定几何形状和特殊材料属性的“块”。然后，支撑-岩石相互作用力学将被合并到模型中，如锚杆单元和围岩之间的位移所表现的那样。这种模拟锚杆行为，特别是拔出破坏的能力，将使DDA锚杆单元成为比以前开发的其他数值锚杆支撑单元更准确的建模工具。Mark(2000)指出：“加固模式实际上是由地面决定螺栓的，而不是相反的。”DDA方法的真正优势之一是，这一结果是分析的自然结果。行为和失效模式不必在分析之前或分析过程中指定-它们是计算结果的一部分。NIOSH斯波坎研究实验室在1995年前是美国矿务局的一个分支，现在是国家职业安全与健康研究所的一部分，自20世纪80年代中期以来，已投入大量资源开发、安装和测试仪表式锚杆。使用仪表式锚杆收集的数据分析对了解锚杆支护的行为有很大贡献，与NIOSH人员的合作是该项目的重要组成部分。螺栓元件的开发将涉及螺栓类型的选择，理论发展、算法开发和实现。PI和参与该项目的蒙大拿理工大学研究生Kathryn Clapp女士将在NIOSH的Steve Siger先生的协助下，共同致力于所有这些方面的工作。该项目的一个相当独特的方面是，一旦理论开发完成，锚杆算法被应用到软件中，将使用已经收集的NIOSH仪器测量的大量锚杆数据进行验证。这是一个巨大的优势，将使该项目在相对较短的时间内完成，预算适中。Clapp女士将执行大部分验证活动，这将需要构建与所使用的每一种不同实验室测试配置相对应的DDA模型，并根据指定的模型条件进行分析，以尽可能接近实验室测试。沿螺栓各点的头部位移和载荷值的DDA计算将被记录下来，并与试验期间观察到的实际螺栓行为进行比较。参考文献：Mark，C.(2000)。《顶板锚杆系统设计》在C.Mark，D.R.Dolina，和R.Tuchman，编辑。《煤矿顶板支撑新技术》，NIOSH公开行业简报，NIOSH IC 9453，第111-132页。

CMS-0201577PI: Mary MacLaughlinInstitution: Montana TechTitle: "Development of a Rockbolt Support Element for Discontinuous Deformation Analysis"Astract:The primary objective of this research project is to develop a rockbolt support element that is capable of modeling actual rockbolt behavior, particularly nonlinear movement between the bolt and the rock which is critical for numerical modeling. Discontinuous Deformation Analysis, DDA, has several unique features that make it a perfect candidate for development of a bolt element that has the ability to characterize rockbolt behavior to a much higher degree of realism and accuracy than has previously been possible. DDA is an implicit discrete element method that already has the capacity to model "blocks" of any irregular shape, and the contact routines are specifically designed to efficiently capture contact between blocks with both convex and concave vertex angles. The method accounts for frictional, cohesive, and tensional forces which are present at the contacts, and allows blocks to slide, separate, and impact without penetrating. A rockbolt element will be implemented as a "block" with a particular geometry and special material properties consistent with those of a typical rockbolt. The support-rock interaction mechanics will then be incorporated into the model as manifested by displacement between the bolt element and the surrounding rock blocks. This capability to model bolt behavior, especially pull-out failure, will make the DDA rockbolt element a more accurate modeling tool than other previously developed numerical rockbolt support elements. Mark (2000) states that "the reinforcement mode is actually dictated to the bolts by the ground, rather than the reverse." One of the real strengths of the DDA approach is that this outcome is a natural result of the analysis. The behavior and failure mode do not have to be specified before or during the analysis - they are part of the calculated results.The NIOSH Spokane Research Laboratory, which was a branch of the US Bureau of Mines until 1995 and is now part of the National Institute for Occupational Safety and Health, has invested significant resources into the development, installation and testing of instrumented rockbolts since the mid-1980's. Analysis of the data collected using the instrumented rockbolts has contributed a great deal to the general understanding of the behavior of rockbolt supports, and collaboration with NIOSH personnel is an important component of this project.The development of the bolt element will involve bolt type selection, theoretical development, algorithm development and implementation. The PI and Ms. Kathryn Clapp, the Montana Tech graduate student involved in this project, will jointly work on all of these aspects, with assistance from Mr. Steve Signer of NIOSH. One fairly unique aspect of this project is that once the theoretical development is finished and the rockbolt algorithms have been implemented into the software, validation will be performed using the large archive of NIOSH instrumented rockbolt data which has already been collected. This is a tremendous advantage and will allow the project to be completed in a relatively short period of time, with a modest budget. Ms. Clapp will perform the bulk of the validation activities, which will entail constructing DDA models corresponding to each of the different laboratory test configurations used, and performing analyses with model conditions specified to represent the lab tests as closely as possible. The DDA calculations of the head displacement and load values at points along the bolt will be recorded and compared to actual bolt behavior as observed during the tests.Reference: Mark, C. (2000). "Design of Roof Bolt Systems." In C. Mark, D.R. Dolinar, and R. Tuchman, eds. New Technology for Coal Mine Roof Support, Proceedings of the NIOSH Open Industry Briefing, NIOSH IC 9453, pp. 111-132.