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GEOSYNTHETIC FILTERS TO PREVENT
SOIL PIPING AND INTERNAL EROSION
Dhanya K A and Dr. Divya P V | Department of Civil Engineering, IIT Palakkad
References
Kerala has been facing severe natural hazards in the past few years.
In August 2018, Kerala received about 2515 mm rainfall as against a
normal rainfall of 2039 mm as per India Meteorological Department.
Rainfall infiltration can affect the stability of unsaturated residual soil
slopes. 3,4
Another major distress associated with rainfall is internal erosion or soil
piping.
Introduction
Properties of Water Collected
Internal Erosion and Soil Piping
Scanning electron micrographs of the piped soil indicates the presence of
mica, feldspar and halloysite.
Low pH value for the soil indicates the acidic nature which provides an
oxidizing environment for the erosion to happen.
Steep gradient and high intensity rainfall can cause piping irrespective of the
dispersive nature of the soil.
There is a lack of research in areas of lateritic or residual soil susceptible to
piping which is subjected to many mineralogical changes during weathering.
Observations
The erosion process which is taking place internally within ground
surface is called as ‘internal erosion’.
Subsurface erosion due to uncontrolled seepage which can lead to the
development of a ‘tunnel like structure’ below the ground due to
percolating water is called as ‘soil piping’.
Depends on the amount of fine content, mineral and chemical
composition of the soil and its dispersive nature
Internal erosion (Western Ghats, August 2019)
Soil piping
(Calicut, Kerala, August 2019)
Piping: Site at Calicut (Kerala)
Surrounding
soil
Piped soil
Soil pipe
Seepage water
Soil Gradation
Classification
pH
TDS
(%)
LL
(%)
PL
(%)
PI
(%)
Sand
(%)
Silt
(%)
Clay
(%)
Soil
Surrounding
piping area
61.2
20 SC
5.47
1.5 43
30 13
Piping Soil
81.4
6
SM
4.88
0.9
-
Non-Plastic
Properties of Soil Collected
pH
Electrical Conductivity
(µs/cm)
Hardness
mg/L as CaCO3
Existing water
source
6.98
42.24
16
Piping water
5.66
40.96
20
5000 x 13000 x
Brumadinho dam failure
(Brazil, 2019) 6
Filters to Control Internal Erosion
The main reason for failures in various geotechnical structures is due to the
loss of fine particles which initially may be un-noticed.
Lack of availability of conventional well graded granular soil in many
geotechnical applications resulted in increasing tendency of using locally
available soil.
Several researchers have reported that the use of geotextiles or
geocomposite can be justified over a conventional graded granular filter to
control internal erosion. 1,2
The existing criteria developed for sand do not directly address the filtration
capacity of geotextiles used to confine unconventional geomaterials. Also
consideration of geotechnical properties of the retained soil as well as filter
media and existing hydraulic condition is lacking.
Hence there is need to critically rethink on the current design criteria of
filters to improve the long term performance of the filter for internally
unstable soil which help in controlling internal erosion and piping.
1. Giroud, J.P. Development of criteria for geotextile and granular filters. In
Proceedings of the 9th International Conference on Geosynthetics, Guarujá, Brazil
, pp. 23-27 (2010).
2. Koerner, Robert M., ed.
Geosynthetics in filtration, drainage and erosion control
. Elsevier, 2013.
3. Rahardjo, H., ONG, T.H., Rezaur, R.B., Leong, E.C. “Factors controlling instability of homogenous soil slopes under rainfall.
Journal of geotechnical and geoenvironmental engineering ASCE,
133(12), 1532-1543 (2007)
4. Vibha,S and Divya,P.V. Performance of Geosynthetic Reinforced Steep Soil Slopes at the onset of Rainfall Infiltration.
Springer Proceedings, IGC,
(2019) (accepted).
5. https://images.app.goo.gl/4zEBkNTLJtk69K118, https://images.app.goo.gl/ftY2dP3SxjCVqpix6,
6. https://images.app.goo.gl/G9EG7keKdCRBRcSs7, https://images.app.goo.gl/4vVTbDMd34nBwMgy6
Conclusions
Adequate care for the dissipation of pore water pressure in various
geotechnical structures using filters and drains is required to avoid failures.
Hybrid geosynthetic filters and drains can be used to prevent internal erosion
and piping in engineered geotechnical structures and fills.
The soil-filter interaction need to be assessed by conducting performance
tests with due consideration of geotechnical properties of the soil as well as
existing hydraulic conditions.
Breach of Teton dam (US, June 1976) 5
ResearchGate has not been able to resolve any citations for this publication.
Article
Full-text available
In the present study, performance of geosynthetic reinforced MSE walls backfilled with locally available marginal lateritic soil at the onset of rainfall infiltration was investigated. Two different types of geosynthetics reinforcements were used. One was a conventional type of geogrids usually used in MSE walls, and the other was composite geogrids. Seepage analysis, stability analysis and strength and deformation analysis were carried out on MSE walls with rainfall simulated for a duration of 3 days. In case of geogrid reinforced soil wall (GR-W), the suction within the backfill was lost completely at the end of 2.176 days of rainfall, whereas suction was maintained even at the end of 3 days of rainfall in walls reinforced with composite geogrids (CGR-W). From the stability analysis, it was observed that the factor of safety of GR-W decreased at the onset of rainfall infiltration with time and reached less than the desirable value of less than 1.5 in 2.125 days of rainfall. The factor of safety of CGR-W was maintained at 1.88 throughout the period of rainfall. The facing deformation in GR-W was found to increase, with a maximum of 3.2 times increase at the end of three days of rainfall. Similarly, there was an increase in maximum tensile load mobilized in the reinforcements in GR-W, whereas in the case of CGR-W, the influence of rainfall was negligible. From the present study, it can be concluded that the presence of composite geogrids improves the overall performance of MSE walls backfilled with marginal lateritic backfills.
Article
Full-text available
Rainfall-induced slope failure is a common geotechnical problem in the tropics where residual soils are abundant. Although the significance of rainwater infiltration in causing landslides is widely recognized, there have been different conclusions as to the relative roles of antecedent rainfall to landslides. The relative importance of soil properties, rainfall intensity, initial water table location and slope geometry in inducing instability of a homogenous soil slope under different rainfall was investigated through a series of parametric studies. Soil properties and rainfall intensity were found to be the primary factors controlling the instability of slopes due to rainfall, while the initial water table location and slope geometry only played a secondary role. The results from the parametric studies also indicated that for a given rainfall duration, there was a threshold rainfall intensity which would produce the global minimum factor of safety. Attempts have also been made to relate the findings from this study to those observed in the field by other researchers. Results of this parametric study clearly indicated that the significance of antecedent rainfall depends on soil permeability.
Development of criteria for geotextile and granular filters
  • J P Giroud
Giroud, J.P. Development of criteria for geotextile and granular filters. In Proceedings of the 9th International Conference on Geosynthetics, Guarujá, Brazil, pp. 23-27 (2010).