Computer modelling of jointed rock masses
Maini, Tidu.; Cudnall, Peter.; Marti, Joaquin.; Beresford, Peter.; Last, Nigel.; Asgian, Margaret Isabelle.
Technical reportAbstract: This report describes work that forms part of an effort to explain and predict the phenomenon of "block motion" which can occur in jointed rock when exposed to dynamic loading. The objectives of the study were to (a) evaluate a general method for modelling jointed rock, (b) translate the original Deformable Element Technique (DET) written in machine language into standard FORTRAN, (c) develop a method for allowing blocks to crack and break into separate elements, and (d) conduct a review of the behavior of rock joints and develop an improved constitutive law for rock block interactions. The major objectives of the study were achieved. A numerical scheme for treating a fully deformable block was demonstrated to give accurate results. It was shown that very little error was introduced by the calculation of siding rock joints by the various rezoning schemes used. Although the new formulation is not likely to be more efficient than existing language, finite difference codes, it was shown to have two major advantages; namely, it is completely general and can completely model any arbitrary jointing pattern and the joints are modeled accurately with no interpolation necessary at interface. Other goals were accomplished. The original rigid block program was translated into FORTRAN Code, RBM. A new idea for treating simple block deformability was developed. Each block was given three degrees of freedom to deform internally, with general constitutive laws given for the intact material. The method differs fundamentally from finite elements and finite differences in that it relies upon the stiffnesses of joints to link neighboring elements or zones. The new program, SDEM, is only slightly slower than the rigid block program and is useful in cases where the intact deformation of rock blocks is important but not large. A modified version of the rigid block program, RBMC, was written which allow blocks to crack and divide into separate blocks in response to the loads acting on them. A simple cracking criterion was used which was based on empirical point-load tests on irregular blocks. An extensive literature survey was made on the properties and behavior of rock joints. Based on these findings, a constitutive law was proposed for rock joints and coded into the subroutine JOINT. Listings for all programs developed under this study are provided in appendices.
Weapons Effects Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Computer programs; Computerized models; Dynamic loads; Jointed rock; Rock deformation; Rock masses
Technical report (U.S. Army Engineer Waterways Experiment Station) ; N-78-4.
Approved for public release; distribution is unlimited.