| Summary: | The aim of this research was to produce a generic rockbolt model for inclusion in two and three dimensional explicit finite element analyses of mining problems. Installation of rockbolts is completely automated. Algorithms for the automatic placement of rockbolt nodes within continuum elements are developed and described. The rockbolts are described independently of the continuum degrees of freedom. Continuum elements and the rockbolt elements are connected through bond elements. Displacements from the continuum are transferred to the rockbolt system through these elements, and the resultant reactions passed to the continuum as external loads. In this way, the solution procedures for the continuum and the rockbolts are separated, thus creating an explicit-explicit subcycle. Using this form or nodal partitioning, rockbolts may have much higher stiffness than the parent continuum without effecting the overall timestep for the problem. Rockbolt systems are constructed of interconnected layers of bond elements and axial structural elements. The constitutive models for both these types of elements are effectively one-dimensional and therefore may be expressed algebraically. The most appropriate bond models from the literature are discussed and implemented. In addition, there is the capacity for elements crossing discontinuities to generate reactions consistent with transverse shearing of rockbolts. The model is tested by performing numerical pull-tests, based on experimental data from the literature. The sensitivity of rockbolt system to the relative bond and axial stiffness is demonstrated. The numerical axial and bond stress distributions were consistent with the experimental results. The model is applied to an excavation problem, with various rockbolt types and support patterns being analysed. The capacity of rockbolts to reduce the occurrence and depth of fracturing around the excavation is demonstrated. The model is also used to represent reinforcing bars in a concrete beam.
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