IRJET- Soil Mass Movement with Recent Deluge in Kerala as Backdrop

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 05 | May 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 5170
Soil Mass Movement with Recent Deluge in Kerala as Backdrop
Ajay Shibu Parackal1, Pooja Nair2, Sandhra Benny3, Shaheer M.R.4, Dr. Balu E George5
1,2,3,4Graduate Student, Dept.of Civil Engineering, Mar Athanasius College of Engineering, Kerala, India
5Assistant Professor, Dept.of Civil Engineering, Mar Athanasius College of Engineering, Kerala, India
---------------------------------------------------------------------***----------------------------------------------------------------------
Abstract - In the beginning of July 2018, severe floods
affected the south Indian state of Kerala due to unusuallyhigh
rainfall in the monsoon season. The rainsubsequentlyresulted
in devastating effects on land and on properties including
major cracks and soil mass movement. The project was dealt
in the geotechnical engineering point of view as this scenario
pose very dangerous threats to the systemsthatexistedwithin.
The aim of the project is to plot the failure pattern of a site.
The work also included determining the basic soil properties
such as optimum moisture content, maximum dry density,
sieve analysis and direct shear test. Thestressesarecalculated
based on a linear-elastic behaviour using a Young’s modulus
and Poisson’s ratio.
Key Words: Deluge, Slopes, Failure slip circle, Factor of
safety, Plaxis
1. INTRODUCTION
Slopestability problemshavebeenfacedthroughout
history whenever the delicate balance of nature has been
disturbed by any kind of internal or external forces. In the
beginning of July 2018, severe floods affected the south
Indian state of Kerala due to unusually high rainfall in the
monsoon season, during which the “pressure gradient”–
which determines pressure changes and, in turn, rainfall–
between land and the Arabian sea was significantly strong,
resulting in heavy rain. The rain subsequently resulted in
devastating effects on land and on properties including
major cracks and soil mass movement. This scenario pose
very dangerous threats and thus is very significant from the
geotechnical engineering point of view.
2. LITERATURE REVIEW
Mass movement is the process by which soil, sand,
rock move downslope as a solid mass under the force of
gravity. Falls have a mass of any size detached from a steep
slope or cliff along a surface on which little or no shear
displacement take place while intopplesconsistofa forward
rotation of a unit about some pivot point under gravity or by
fluids in the cracks. In slides the movement consists of sear
strain and displacement along one or several surfaces. The
Swedish circle method assumes the surface of sliding as an
arc of the circle. A series of slip circles are checked and the
lowest factor of safety is the likely failure plane. PLAXIS is a
finite element program for geotechnical applications in
which soil models are used to simulate the soil behaviour.
PLAXIS can be used for Geotechnical applications that
require advanced constitutive models for the simulation of
the non-linear, time-dependentandanisotropicbehaviourof
soils and/or rock.
3. METHODOLOGY
The project wasinitiated byvisitinga site whichwas
highly affected but accessible to carry out the
reconnaissance survey. After analyzing the crack pattern in
the area using auto level, the profile of the crack wasplotted.
An undisturbed sample by core cutter and a sample of soil
from the area was collected to carry out the basic tests. The
slip circles of different radii were analyzed and the failure
plane was determined by Swedish circle method and
PLAXIS2D. The possible reasons for the failure at the site
was predicted and different methodologies were suggested
to make sure that the area remains safe at least in the recent
future.
4. LAB TESTS
 Sieve Analysis
Chart 1: Sieve Analysis

 Direct shear test
Chart 2: Direct shear test
From the graph,
C=22.563 kN/m2
Φ=210
 Specific Gravity using Pycnometer,
G=2.36
 Bulk Density using Core cutter,
γ=15.484 kN/m3
5. SLOPE STABILITY ANALYSIS
Stability analysis of slopes was done by Swedish circle
method and PLAXIS2D
Chart 3: Plot of crack
 Swedish circle method
Horizontal distance (m)
r=6.5m
Level staff
Readings(m) r=8.5m
Chart 4: Swedish circle method
 PLAXIS 3D
Chart 5: Isosurface for total displacement without anchors
Factor of safety obtained without anchors =8.163
Chart 6: Isosurface for total displacement witn anchors

Factor of safety obtained with anchors=8.445
6. CONCLUSIONS AND DISCUSSIONS
The severe damage of the buildings in the vicinityofthearea
can be explained through an unplanned and poor
construction techniques adopted inanarea characterized by
high level of soil instability. Also, continuous stagnation of
water during the deluge has substantially deteriorated the
soil quality. The site that has undergone failure due to the
flooding cannot be used for construction of any kind of high
rise buildings for commercial purposes nor any residential
buildings without any kind of strengthening methods to
stabilize the slopes.
Anchors are tension resisting elements prevent excessive
erosion and any further landslides in areas severelyaffected
by heavy rainfall and stagnant flooding. In PLAXIS 3D,
analysis is done for total displacements before and after
providing anchors in the slopes. The results thereby
obtained shows that the total displacement in the slope has
reduced with installation of anchors. Ground anchors prove
to be an efficient solution for maintaining slope stability
without considering the complexities and considering as a
homogenous linearly elastic mass.
REFERENCES
[1] Jones, J. A. A. (1987). The effects of soil piping on
contributing areas and erosion patterns. Earth Surface
Processes and Landforms, 12(3), 229-248.
[2] Cruden, D. M. (1991). A simple definition of a
landslide. Buletin of Engineering Geology and the
Environment, 43(1), 27-29.
[3] DeRisi, R., Jalayer, F., De Paola, F., Iervolino, I.,Giugni,M.,
Topa, M. E.,&Gasparini, P. (2013). Flood risk assessment
for informal settlements. Natural hazards, 69(1), 1003-
1032.
[4] Abrams, A. (1975). The influence of fluid viscosity,
interfacial tension, and flow velocity on residual oil
saturation left by water flood. Society of Petroleum
Engineers Journal, 15(05), 437-447.
[5] Gazetas, G., Tassoulas, J. L., Dobry, R., & O'Rourke, M. J.
(1985). Elastic settlement of arbitrarily shaped
foundations embedded in
GaZhang,RuiWhang,JiyunQian,Jian-Min
Zhang,JianguQian, Effect study of cracks on behavior of
soil slope under rainfall conditions, Soils and
Foundations,Volume 52,Issue 4, August 2012,Pages 634
half-space. Geotechnique, 35(3), 339-346.
[6] ManikathiyakanathanSasekaran,Impactofpermeability
and surface cracks on soil slopes, A dissertation
submitted to The University of Manchester for the degree
of Master of Science by Research in the Faculty of
Engineering and Physical Science.
[7] Brinkgreve, R.B.J., Swolfs, W.M., Engin, E., Waterman,D.,
Chessaru,A., Bonnier,P.G., & Galavi, V.(2010).PLAXIS2D
2010. User manual, Plaxis bv.
[8] 8. Bishop, A.W., (1955), “The Use of the Slip Circle in the
Stability Analysis of Slopes”, Geotechnique, Vol. 5, pp 7 -
17.

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