that possible impacts on the contaminant’s increasing mobility are evaluated, and
implementation of the measures is incorporated into the time schedule of the
project properly.
• Risk of impacts on stability of buildings and above-ground structures: During
fracturing, deformation of the geological material in the surroundings of the
newly formed crack takes place. Vertical movements on the surface and lifting
of the surface may take place, as well as propagation of vibrations and seismic
waves. Hence, it is recommended that the possible impacts on underground, as
well as above-ground structures, are thoroughly assessed before the fracturing
implementation. The extent of vertical movements on the surface of the ground
depends on the fracturing method, depth of the horizon of interest, number of
cracks, lithology of the geological environment, cohesion and strength of the
geological material, plasticity, density, consistency, weathering level, layering of
the environment, locations of aquifers and insulators, fracturing pressure and
gradient, speed of seismic wave propagation, etc. Thus, fracturing preparation
and implementation in gradual steps is necessary: investigation drilling, laboratory and field tests, pilot fracturing tests, project and implementation of full-scale
fracturing.
32.6 Fracturing in Remediation Applications
For the remediation purposes, hydraulic fracturing may be used for enhancing
remediation of unsaturated and saturated zones, as well as for remediation of perched
aquifers. In a majority of cases, fracturing is combined with a selected decontamination method, for the purpose of increasing its efficiency (pump-and-treat approach,
venting, in situ oxidation/reduction, methods based on the principles of in situ
biodegradation, etc.). Geological environment fracturing may increase its effective
hydraulic and pneumatic conductivity. Especially in an environment showing low
permeability, such as clayey and silty geological materials, transport of contaminants
is controlled by diffusion, and, thus, the process is very slow. Creation of a network
of artificial cracks in the geological environment causes reduction of length of the
diffusion paths, and, simultaneously, advection share of the transport increases. As a
result, the remediation intervention is accelerated. Concurrently, this method may
ensure access to places that would be left untouched in the case of utilization of
standard remediation boreholes. The radius of influence of a borehole increases, and,
thus, the number of boreholes necessary for the remediation is reduced. Simultaneously, fracturing may cause reduction of the level of soil heterogeneity.
The results stated in Table 32.1 may be achieved by fracturing.
The possibility of direct injection of various kinds of liquids and crystalline
materials into the fractured soils and rocks during the actual fracturing process
together or instead of regular proppant, for the purpose of increasing the remediation
efficiency, represents an advantage of utilization of hydraulic and pneumatic fracturing (Siegrist et al. 2001). Generally, this may concern, for example, substances of
the following kinds: (1) nutrients, buffers, and bacterial strains for supporting
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J. Kukačka and P. Kvapil
implementation of the measures is incorporated into the time schedule of the
project properly.
• Risk of impacts on stability of buildings and above-ground structures: During
fracturing, deformation of the geological material in the surroundings of the
newly formed crack takes place. Vertical movements on the surface and lifting
of the surface may take place, as well as propagation of vibrations and seismic
waves. Hence, it is recommended that the possible impacts on underground, as
well as above-ground structures, are thoroughly assessed before the fracturing
implementation. The extent of vertical movements on the surface of the ground
depends on the fracturing method, depth of the horizon of interest, number of
cracks, lithology of the geological environment, cohesion and strength of the
geological material, plasticity, density, consistency, weathering level, layering of
the environment, locations of aquifers and insulators, fracturing pressure and
gradient, speed of seismic wave propagation, etc. Thus, fracturing preparation
and implementation in gradual steps is necessary: investigation drilling, laboratory and field tests, pilot fracturing tests, project and implementation of full-scale
fracturing.
32.6 Fracturing in Remediation Applications
For the remediation purposes, hydraulic fracturing may be used for enhancing
remediation of unsaturated and saturated zones, as well as for remediation of perched
aquifers. In a majority of cases, fracturing is combined with a selected decontamination method, for the purpose of increasing its efficiency (pump-and-treat approach,
venting, in situ oxidation/reduction, methods based on the principles of in situ
biodegradation, etc.). Geological environment fracturing may increase its effective
hydraulic and pneumatic conductivity. Especially in an environment showing low
permeability, such as clayey and silty geological materials, transport of contaminants
is controlled by diffusion, and, thus, the process is very slow. Creation of a network
of artificial cracks in the geological environment causes reduction of length of the
diffusion paths, and, simultaneously, advection share of the transport increases. As a
result, the remediation intervention is accelerated. Concurrently, this method may
ensure access to places that would be left untouched in the case of utilization of
standard remediation boreholes. The radius of influence of a borehole increases, and,
thus, the number of boreholes necessary for the remediation is reduced. Simultaneously, fracturing may cause reduction of the level of soil heterogeneity.
The results stated in Table 32.1 may be achieved by fracturing.
The possibility of direct injection of various kinds of liquids and crystalline
materials into the fractured soils and rocks during the actual fracturing process
together or instead of regular proppant, for the purpose of increasing the remediation
efficiency, represents an advantage of utilization of hydraulic and pneumatic fracturing (Siegrist et al. 2001). Generally, this may concern, for example, substances of
the following kinds: (1) nutrients, buffers, and bacterial strains for supporting
630
J. Kukačka and P. Kvapil