The modeling of geoengineering processes involves special considerations and a design philosophy
different from that followed for design with fabricated materials. Analyses and designs for structures
and excavations in or on rocks and soils must be achieved with relatively little site-specific data and
an awareness that deformability and strength properties may vary considerably. It is impossible to
obtain complete field data at a rock or soil site. For example, information on stresses, properties
and discontinuities can only be partially known, at best.
Since the input data necessary for design predictions are limited, a numerical model in geomechanics
should be used primarily to understand the dominant mechanisms affecting the behavior of the
system. Once the behavior of the system is understood, it is then appropriate to develop simple
calculations for a design process.
This approach is oriented toward geotechnical engineering, in which there is invariably a lack of
good data; but in other applications, it may be possible to use 3DEC directly in design if sufficient
data, as well as an understanding of material behavior, are available. The results produced in a
3DEC analysis will be accurate when the program is supplied with appropriate data. Modelers
should recognize that there is a continuous spectrum of situations, as illustrated in Figure 3.1: