Geoenvironment Impact Mitigation and Management - Sustainable Practices in Geoenvironmental Engineering - page 358

Regardless, or independent, of the causative sources, there are many reasons that geo-
disasters happen in the constructed environment. One of the main reasons is inadequate
consideration or accounting of (a) the nature and intensity of potential geoenvironment
stressors, (b) the nature, extent, and magnitude of their impacts on constructed facili-
ties, and (c) the capability of the land compartment to fulill its design site functionality
requirements.
10.3.1.1 Naturally Occurring Events
Naturally occurring events provoking or resulting in geo-disasters fall into two categories:
(1) weather-related or weather-provoked and (2) non-weather-related events. Included in
the irst category of weather-related events are
• Seasonal winter-summer cycles: Stressor impacts include frost heave in win-
ter, ground collapse in summer due to thawing of ice lenses formed in winter,
looding due to melting of snowpacks, avalanches, seasonal drought conditions,
etc. By and large, knowledge of these kinds of stressors and their impacts is
well established in civil and geotechnical engineering practice, and preventa-
tive design and construction procedures have been developed to avoid develop-
ment or mitigation of geo-disasters resulting from these stressors. Examples of
some of these include the use of frost-free soil material underpinning founda-
tions, restricting water inlow to underpinning foundations in frost-susceptible
regions, alleviation of excessive pore pressures in slopes to minimize or elimi-
nate slope instability and slope failures due to buildup of excessive porewater
pressures, application of avalanche control procedures, construction of lood-
protective barriers along river banks, construction of diversion ditches and
canals, etc.
• Hurricanes, typhoons, and tornadoes: Although the common feature to these
weather-related events is wind , the results of the actions represented by these
events differ somewhat. The distinguishing feature is water. The resultant stress-
ors from hurricanes and typhoons passing over open water are both hydraulic and
mechanical—taking the form of looding of shorelines and low-lying areas and
wind forces acting on exposed facilities and objects.
As with the previous naturally occurring seasonal events, knowledge of the extent of
the effects of these events are well-appreciated. Predictive analytical-computer models
have been developed to forecast the advent and magnitude of such events—to a greater or
lesser degree of accuracy depending on the availability of on-site data. Flood control levees
and embankments form one of the major mitigating or preventative measures against the
hydraulic (water and looding) stressors and their impacts. Wind-resistant design of struc-
tures will minimize damage to structures, and most importantly, the construction and use
of robust storm shelters is perhaps the best means for withstanding the impacts from the
mechanical (wind force and tornado forces) stressors.
Outside of ensuring robust ground stability and support capability to mitigate the
mechanical and hydraulic geoenvironment stressor impacts, mitigation of stressor impacts
from the more commonly reported type of naturally occurring events provoking geo-
disasters such as earthquakes, hurricanes, tornadoes, and loods are technically not “miti-
gation” but are “protection” against stressor impacts. Examples of these are storm shelters,