GEOSYNTHETICS ENGINEERING: IN
THEORY AND PRACTICE
Prof. J. N. Mandal
Department of civil engineering, IIT Bombay,
Powai , Mumbai 400076, India.
Tel.022-25767328
email: [email protected]
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Module - 3
LECTURE- 12
Geosynthetic properties and test methods
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
RECAP of previous lecture…..
 Puncture resistance test
 Penetration resistance test (drop test)/ tear resistance
 Tensile behavior of geogrid
 Geogrid rib tensile strength
 Geogrid junction (node) strength
 Junction strength of geocell
 Tensile strength of gabions
 Direct shear test on geosynthetic
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Pullout or anchorage resistance
It is very important to compute the pullout capacity of
reinforcement to ensure stability of any reinforced
structure like reinforced soil retaining wall, reinforced
slopes etc.
Two basic mechanisms are involved to mobilize or transfer
pullout resistance between soil and geosynthetic
1) Interface friction, and
2) Passive resistance
 Only interface friction is associated with geotextile
 Both interface friction
associated with geogrid.
and
passive
resistance
are
Pullout resistance or anchorage capacity is expressed as the
ratio of pullout force to the width of the sample (kN/m)
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Pictorial view of pull-out test
Schematic view
Interaction coefficient of geotextile (Ci)
Pr = F/W = 2. L. n. Ci. tan
Ci 
Pr
2  L  ( h   q )  tan 
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
FEM analysis of pull-out test on cellular reinforcement
Cellular reinforcement
Stress distribution in cellular reinforcement
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
 Ultimate pullout load was found increasing with
increasing height of the reinforcement up to 30 mm,
 Further increase in height shows the decrease in
ultimate pullout resistance.
 The optimization analysis shows that the spacing to
height ratio of 3.3 gives the maximum pullout
resistance for cellular reinforcements.
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Example:
Determine interaction coefficient.
The following data is given.
P = 65kN/m; Le= 1m;  = 30˚;
q = 60kpa.
Solution:
σn = γ x h + q = 20x0.3 + 60 = 66 kPa
P = 2 Ci Le σn tan 
66 = 2xCix1x66xtan30˚
Ci = (66)/ (2x66x0587) = 0.849
Interaction coefficient = Ci = 0.849
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Tensile behavior of geomembrane
Smooth high density polyethylene (HDPE) and textured high
density polyethylene (HDPE) geomembrane are used for
conducting dumbbell shaped tests.
Test specimens are dying
cut from large sheets
ASTM D 638, D 882,
D 6693 (Dumbbell shape)
Dumbbell shaped test specimen
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Tensile behavior of dumbbell shaped geomembrane
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Tensile behavior of wide width shaped Geomembrane is
suitable in plain strain condition and much more design
oriented compared to dumbbell shaped geomembrane
Specimen is 200 wide with
100 mm gauge length
Strain rate = 1 mm/ minute
Wide width geomembrane (ASTM D4885)
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
 Greater width of the specimen minimizes the contraction
edge effect (necking) and provides closer results to actual
material behavior (ASTM D4885).
Tensile behavior of wide width shaped
geomembrane (Smooth and textured HDPE)
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Tensile behavior of smooth and textured 1.5 mm thick HDPE
geomembrane
Tensile
property
Dumbbell shape
ASTM D638
Smooth Textured
Strength at
yield (kN/m)
Elongation at
yield (%)
Strength at
break (kN/m)
Elongation at
break (%)
Narrow width
(25 mm)
ASTM D882
Smooth Textured
Wide width
(200 mm)
ASTM D4885
Smooth Textured
30.3
27.7
28.0
27.54
26.0
24.0
10.4
9.6
16.5
15.0
15.5
15. 0
28.19
29.5
-
-
-
-
435
358
> 500
> 500
> 500
> 500
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Tear resistance of Geomembrane (ASTM D 1004, D2263,
D5884, D751, D1424, D1938, and ISO 34)
The specimen has a 90
degree angle.
Tearing resistance of geomembrane (a)
schematic view and (b) pictorial view
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
 Geomembranes can be joined for seam in shear and
seam in peel test.
Equipments for joining
geomembrane
Some typical seams of
geomembrane
(After Giroud, 1994)
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Hydraulic properties
 Porosity
 Apparent opening size
 Percent open area
 Permittivity or cross plane permeability
 Transmissivity or In- plane permeability
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Porosity
Porosity (n) = (Volume of void / Total volume) = Vv / V
Total volume (V) = Vs + Vv
Vs = volume of solid = ( m. A) /,
m = mass per unit area (g/m2),
A = Area (m2),
 = density (g/m3),
Vv = volume of void,
V = total volume = A. tg
tg = thickness of geosynthetics.
V v V  Vs
Vs
n

 1
V
V
V
m .A
m

n  1
 1
A .t g
 .t g
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Apparent Opening Size (A.O.S.) or Equivalent
Opening Size (E.O.S) [ASTM D4751]
Apparent opening size can be measured in four ways:
1. By sieving glass beads
2. By image analyzers (Gours et al. 1982), and
3. By mercury intrusion (Holtz, 1988)
4. By bubble point method (Bhatia et al., 1996)
Pictorial view of the glass beads of different sizes
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
 The size of the beads
which passes by less
than or equal to 5 % is
represented as Apparent
opening size (A.O.S.) or
O95 expressed in
millimeters.
 The O95 value is
specifically used for
design of any hydraulic
structure.
Determination of apparent opening
size by dry glass sieving method
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Apparent opening size of different geotextile filters
 Apparent opening size of geotextile decreases with
increase in the weight of geotextile.
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Percent open area (POA)
Percent open area can be defined as the ratio of total open
area or total voids area of the geotextile to the total area of
geotextile. It is expressed in percentage (%).
POA 
Total area of the openings of geotextile
Total area of geotextile
 The open area is measured by passing a light through the
geotextile to a poster sized cardboard which is in the form of
a graph sheet. From the graph sheet, number of squares can
be counted. Otherwise, the voids can be mapped by a
planimeter.
 Total area is measured by same magnification.
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
 POA is applicable only for monofilament woven geotextile.
 The percent open area (POA) for monofilament and slit
film wovens should be greater than or equal to four
percentage.
 As the filaments of non woven geotextiles are closely
tightened and very random, light cannot pass through it
properly and as a consequence, the light passing method is
not suitable for it.
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Please let us hear from you
Any question?
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay
Prof. J. N. Mandal
Department of civil engineering, IIT Bombay,
Powai , Mumbai 400076, India.
Tel.022-25767328
email: [email protected]
Prof. J. N. Mandal, Department of Civil Engineering, IIT Bombay