A Contact Detection Method For The Three-dimensional Blocky System And Discontinuous Deformation Analysis (DDA)

Discontinuous Deformation Analysis (DDA) is a powerful numerical method for simulating the discontinuous media composed of blocks or particles. To simulate and analysis the natural physical process of such systems, it needs not only to render realistic images according the material's physical and geometric properties, but also needs to model objects interactions precisely. DDA has been widely applied to the 2D analysis of discontinuous deformation of rock blocky systems in rock engineering, while for 3D problems, the lack of reliable 3D contact detection algorithms for polyhedron blocks turns out to be the main obstacle. Contact detection is a key problem, at present, encountered by all numerical methods during modeling and analyzing practical 3D blocky systems in rock engineering. A contact detection algorithm must judge and distinguish reliably and correctly the different contact types, find the locations and determine, update the states of contacts of blocky systems. During numerical modeling, the contact detection inludes the contact judge and the contact transfer.Advantages and shortcomings of the existent contact judge schemes are discussed. The principle only according to which a correct contact judge algorithm be bring out is represented. And a new approach, namely Incision Body (IB) scheme is put forward, which combines the advantages of the existent methods. The scheme defined a contact scope for a block and, at the same time, divided the scope into four sections. No matter where a block contacts with another block, the contact part of the block must fall into one of four sections of another block. The contact type between two blocks is formed through combining the two geometry types of two contact components of the two blocks. The contact component of a block was determined by the information of incision body of the block, and a one-to-one mapping from the incision body to the contact component is established.Contact transfer is very important when analyzing discontinuous media using a DDA computer program because the analysis is implemented step-by-step with several time increments. If the contact informations of a blocky system are transferred inaccuratly, the tracking and updating of contacts will be failed. Block contact constraints are enforced using the penalty method and the point-to-face model is adopted as contact model. Subsequently, a contact transfer algorithm is presented to fulfill the transfer of contact informations from current time step to next time step. Furthermore, there are numerous difficulties in...