Civil Engineering Reference
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on the structure of the soil layer, unsaturated zone, and even part of the saturated
zone. The second ones are determined by distribution of the geodynamic stresses
and degassing processes in Earth's crust, geochemical processes, and the lithofa-
cial peculiarities of deposits. Because of the long-term influence of endogenic
factors, they often lead to the appearance and imposition of exogenous processes
on the endogenous formation of the PFMZ. As a result, in many cases it is pos-
sible to distinguish a third group of zones with a mixed genesis. These are formed
under the influences of internal and external forces but are mainly due to endo-
genic stresses and processes. The presence of endogenic, geodynamic, and gas-
related factors in the formation of PFMZ determines their maximum development
depth (hundreds and thousands of meters).
The lithofacial and geochemical factors of PFMZ formation usually deter-
mine their lower depths (mainly meters and tens of meters). Even smaller depths
are characteristic of the exogenic PFMZ (usually within 1 or a few meters).
Due to the presence of morphological peculiarities in the section, PFMZ may
be classified in the plane as linear, oval and round, and crescent-like and combined
and in the section as window-like, vein-like, fractured, elementary (filled or not
filled), etc.
Based on the infiltration and migration activity, PFMZ can be subdivided
into hyperactive, with more than a tenfold increase of infiltration and migration
processes as compared to background sites; very active, with an increase of these
processes of 5-10 times as compared to background values; medium active (2-5
times higher than background); and low active (less than 2 times higher than the
background). It is worth noting that the infiltration and the migration activity,
depending on the deposit composition and migrant type, may not correlate.
According to the involvement of the elements of the hydrogeological system
(soil, unsaturated zone, upper groundwater, deep confined aquifers, and aquitards),
one can distinguish the following PFMZ types:
1. Thorough, with a complete or high involvement of the main water exchange
geosystem elements
2. Mesodeep, with the involvement of soils, the unsaturated zone, and one or
two aquifers
3. Subsurface (aeration), with the involvement of soils, the unsaturated zone,
and possibly a part of the upper aquifer (in the case of a thin unsaturated
zone)
4. Soil, located within the soil cover
By evolution, one can distinguish stable, progressing, and degrading PFMZ.
In solid and semisolid rock massifs, the macrozones, nanozones, and picozones
of increased permeability related with fracturing are also known. However, their
role as zones of preferential flow and mass exchange is usually assessed only
integrally.
Special importance for the PFMZ phenomena that represent the micro-
PFMZ and meso-PFMZ is usually related to the depression-type relief. For
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