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Numerical modelling of jointed and faulted rock
Published in Hans Peter Rossmanith, Mechanics of Jointed and Faulted Rock, 2020
As mentioned, many people have modelled rock that contains systems of existing discontinuities. As early as 1968, Goodman modelled a very complex system with many hundreds of joints in two dimensions. Three dimensional calculations of jointed rock soon followed: e.g. Mahtab & Goodman (1970). In the next twenty years many finite element or finite difference calculations included pre-existing discontinuities to represent joints or faults. In most finite element calculations, discontinuities are represented as a special kind of element, which is specified, in advance, as linking two neighbouring solid elements. Since the connectivity of the system is pre-specified, this type of formulation has difficulties with large movements and rotations of rock blocks. There is another class of model known as the “discrete element method” (DEM) that treats a discontinuity as a boundary condition rather than as a special element: large movements and rotations are allowed. A survey of such methods is provided by Cundall & Hart (1989). Note that the term “distinct element method” was used by Cundall & Strack (1979) to refer to the particular discrete element method that employs deformable contacts and an explicit, time-marching solution to the equations of motion. Current distinct element programs are three dimensional, fully dynamic, with deformable blocks and structural members (Hart et al, 1988).
Rock mass characterisation for rock dredging projects
Published in Peter N.W. Verhoef, Wear of Rock Cutting Tools, 2017
The recording of the patterns of the discontinuities of the rock mass is not such an easy task if only information can be obtained from over-water surveys. Also when discontinuity surveys can be conducted on-land, where outcrops or quarries are available, it remains to be established whether the patterns recorded are representative for the rocks to be dredged. A discontinuity is defined as a significant mechanical break or fracture of negligible tensile strength in a rock. Discontinuity is the general term used, and makes no distinctions concerning the age, mode of origin or geometry of the feature (Priest 1993). Singular discontinuities and systematic discontinuities can be distinguished.
Multidisciplinary monitoring of progressive failure processes in brittle rock slopes – Concepts and system design
Published in Jan Rybář, Josef Stemberk, Peter Wagner, Landslides, 2018
H. Willenberg, T. Spillmann, E. Eberhardt, K. Evans, S. Loew, H.R. Maurer
First, it is essential to properly investigate the 3-D geological structure of the monitored rock mass. Important geometrical parameters include discontinuity orientation, spacing, persistence and connectivity, and the location of discrete surface features (Einstein et al. 1983). This information can be attained through a combination of geological mapping, detailed discontinuity mapping, both at surface and in boreholes, and active geophysical testing. New developments in 3-D seismics, 3-D georadar, crosshole tomography and borehole to surface testing methods show promising trends with respect to improving the quality of geological models based on surface mapping data (e.g. Schepers et al. 2001).
Investigation of rock slope stability under pore-water pressure and structural anisotropy by the discrete element method
Published in Geomechanics and Geoengineering, 2021
Bahram Nadi, Omid Tavasoli, Denise-Penelope N. Kontoni, Ali Tadayon
For analysing and modelling discontinuities in the rock wall, a UDEC two-dimensional software has been used based on a ‘discrete element method’ (also called ‘distinct element method’). The numerical method of a distinct element with a separate block of elements allows the development of in-block behaviour, sliding, rotating, and, in general, interlocking large-scale displacements (Hart 1993). The two-dimensional UDEC and 3DEC software were introduced for the first time in the 1980s in the prevailing code to formulate rigid and modifiable blocks in the discontinuities. The aforementioned programs have been used in modelling the behaviour of rock masses, including the studies carried out by Cundall (1971, 1980) and Lemos et al. (1985). In this method, the discontinuous rock mass is presented as a series of rigid blocks, and later with the development of this method of flexible blocks, in which there are interchangeable joints and interactions Are considered. In this way, the numerical model must represent two types of mechanical behaviour, which include discontinuity behaviour and solid material behaviour. Boundary conditions in geomechanical issues are also divided into two real or artificial boundaries. The actual boundaries of the slope stability issues include drilled or natural surfaces, in which the stress is usually free. In this study, vertical boundaries are verified in the horizontal direction and the lower boundaries in the horizontal and vertical directions. The geometry and rock slopes dimensions studied in this study are shown in Figure 8.
Numerical analysis on mining-induced fracture development around river valleys
Published in International Journal of Mining, Reclamation and Environment, 2018
C. Zhang, R. Mitra, J. Oh, I. Canbulat, B. Hebblewhite
The Voronoi algorithm begins by distributing points randomly within the tessellation region. The interior points then are allowed to move. An iteration procedure moves the points; the higher the number of iterations, the more uniform the spacing between points will be. Then triangles are created between all points. At the final stage, the Voronoi polygons are created by constructing perpendicular bisectors of all triangles that share a common side. The polygons are truncated at the boundaries of the tessellation region [8]. As depicted in Figure 3, a physical discontinuity is created when the stress level at the interface between block exceeds a threshold value either in tension or in shear, and fracturing occurs.
Mixed FEM for solving a plate type model intended for analysis of pavements with discontinuities
Published in Road Materials and Pavement Design, 2018
H. Nasser, O. Chupin, J.-M. Piau, A. Chabot
This section deals with two types of discontinuity (of zero thickness): discontinuities within vertical plans (joints or cracks) and discontinuities at interfaces (construction will, partial debonding due to damaging at the interface between layers).