The Contact Theory proposed by Shi in 2015 is expected to solve the contact detection problem of discrete blocks in a perfect and universal manner. In the present paper, a contact detection algorithm for arbitrary polygonal blocks based on the Contact Theory is proposed and coupled into the two-dimensional DDA (2D-DDA). Four different methods to determine the contact entrance lines are presented, and among which the contact vector method is used in the proposed contact detection algorithm because of its advantage in treatment of small overlapping of blocks along the edges and its simplicity in implementation. The vertex-to-vertex contact and vertex-to-edge contact are separately handled to effectively select the final actually needed entrance lines for the contact treatment. The proposed algorithm is examined by some representative and complex simulation examples, and the results are theoretically verified or compared with that by the original 2D-DDA with the direct contact detection algorithm based on the angle method. It is shown that the proposed algorithm can handle the contact detection of convex and concave blocks in diverse scenarios effectively. This work proves the feasibility and robustness of the Contact Theory, and provides 2D-DDA an optional effective approach for the contact detection.

Shi于2015年提出的“接触理论”有望以一种完美，通用的方式解决离散块的接触检测问题。本文提出了一种基于接触理论的任意多边形块接触检测算法，并将其耦合到二维DDA（2D-DDA）中。提出了四种确定接触入口线的方法，其中接触矢量方法在所提出的接触检测算法中被使用，这是因为其在处理沿边缘的小块重叠方面的优势及其实现的简便性。顶点到顶点的接触和顶点到边缘的接触被分别处理，以有效地选择最终实际需要的接触线。通过一些具有代表性和复杂的仿真示例对提出的算法进行了检验，并使用基于角度方法的直接接触检测算法对结果进行了理论验证或与原始2D-DDA进行了比较。结果表明，所提算法可以有效地处理各种场景下凹凸块的接触检测。这项工作证明了接触理论的可行性和鲁棒性，并为2D-DDA提供了一种可选的有效的接触检测方法。