Lesson 1/Learning Event 2
FACTORS AFFECTING OPERATIONS
Ground and Surface Water Conditions. Test pits or auger borings should be used to determine the
approximate amount of ground water seepage to be expected and to locate the water table. Many
existing quarries contain standing water from seepage or rainfall which can often be drained with
pumping equipment. Estimate the feasibility of removing water by installing a pump and gaging the rate
of fall of the water surface. It is essential that most borrow pits be worked dry because it is difficult to
move and compact borrow material when it contains excessive moisture. Gravel pits containing little or
no clay can be worked wet if proper equipment is available. Quarries are worked dry unless it is
impossible or impractical, as in operations involving coral reefs. Extensive drainage projects, such as
diverting a stream or draining a lake or swamp, should be considered only when an extended operation
is planned or when no other sites are available.
Location and Accessibility. Choose a location as close as possible to the construction site and
convenient to good routes of transportation. This allows more efficient hauling by decreasing the length
of access roads. Quarry haulage is ordinarily done by trucks. However, for large operations in the
communications zone, rail and water transportation are sometimes used. When large quantities are
being shipped by rail, lay a siding into the pit or quarry to eliminate trucking from source to railroad.
Overburden. Clearing the vegetation and overburden from a site may be as extensive an operation as
excavating the material itself. Try to choose a site which will provide quality material with a minimum
of grubbing, clearing, and stripping. It is impractical to operate a site where the depth of overburden
exceeds one-third the thickness of the usable material. Overburden should not exceed a depth of fifteen
feet (about 5 meters). For some types of construction, the overburden may be useful as fill material,
either in its original state or after improvement by mixing with sand or gravel.
Slopes. Sites at which gravity can aid in the removal of materials are prcferable to those at which
materials must be moved uphill. Consider, too, the effects of topography on drainage, road construction
and quarry access, and on the location of processing and support facilities.
Jointing and Weathering. Joints are of considerable engineering importance, especially in excavation
operations. Joints oriented at right angles to the working face present the most unfavorable condition.
Conversely, joints oriented about parallel to the working face greatly facilitate blasting operations and
yield even, smooth breaks. Joints can serve as water channels. As such they can increase drainage and
weathering problems. Weather material should not be used for aggregate. The spacing of joints can
control the size of material removed and can affect drilling and blasting.