Environmental Engineering Reference
In-Depth Information
Large-scale lysimeters
Water content (TDR)
Matric suction (TC sensors)
10 m
Diversion
berm
Instrument
nest
Cover
soils
Diversion
berm
Surface
runoff
Root
barrier
Geocomposite
drain
Geomembrane
liner
Interim
cover
soil
Percolation
Figure 6.59
Types of measurements required for verification monitoring of cover systems.
The climatic quantification that provides the final “net
moisture flux” at ground surface has many inherent broad
assumptions. The tendency to focus the analysis on average
conditions may cause a deviation from the real performance
of the cover system. In other words, extreme weather condi-
tions may need to be more carefully evaluated during cover
design. For example, extreme conditions where there is sig-
nificant water runoff can result in serious erosion problems.
The effect of cracks forming in a clay-rich soil can radi-
cally change the soil response to infiltration and exfiltration.
Unsaturated soil properties are highly nonlinear and may
even change to be bilinear in character. These extreme con-
ditions need to be given more attention and may even turn
out to be a controlling factor once the clay content reaches
a particular percentage.
6.4.8 Long-Term Integrity
The assessment of long-term integrity of soil cover sys-
tems may increasingly become an activity of concern within
geotechnical engineering. Soil cover designs have grown
rapidly and the evaluation of their performance is essential
for ensuring their long-term integrity and acceptability.
There appears to have been a strong dependence upon
average or typical conditions for design purposes; however,
it is the influence of extreme conditions that may have the
most dramatic effect. This is true for both soil properties
and weather conditions. Soils crack and the properties of
the overall soil mass can change dramatically. Extreme
weather conditions can be destructive, causing failures to
cover systems.
Search WWH ::
Custom Search