Embed Size (px)
Proceedings of Indian Geotechnical Conference
December 15-17, 2011, Kochi (Paper No. Q-087)
GRAVILOFT RETAINING WALL: A CASE STUDY
R. J. Balwan, HOD, Govt. Polytechnic, Kolhapur, [email protected]
Ajitkumar Kumbhar, Manager, C.E.C.M., M V M Ltd, Pune, [email protected]
ABSTRACT: Earth retaining structures cost is major cost in any infrastructural developmental project. Saving in earth
retaining structure influences the project cost. The use of gravity wall coupled with loft gives excellent combination,
resulting into about 40% cost saving. This has further advantages as no new material required, reduced foundation width,
uniform foundation pressure, no skilled labour required, speedy construction, material saving, etc. An attempt has been
made to work out the cost of construction of “Graviloft wall” and “RCC Cantilever and Gravity wall”. The comparison
clearly indicates a considerable reduction in the cost of construction.
INTRODUCTION
‘Retaining Structure’ is an indispensable feature of any
civil construction projects. Traditionally, Gravity Retaining
wall, Cantilever Retaining wall, Counterfort Retaining wall,
Buttress Retaining wall and Reinforced Earth walls are
adopted to retain soil at a slope steeper than that it would
naturally assume. It is noticed that the cost of earth
retaining structure is major one and therefore any saving in
earth retaining structure influences the project cost.
GRAVILOFT TECHNOLOGY Gravity retaining wall have limitations due to their bulky
section and higher cost. RCC cantilever retaining wall also
not cost effective for more height. The Graviloft technology
is essentially a marriage of Gravity Wall and R.C.C. wall
effected by the provision of a loft. In this concept the good
points of the gravity walls and R.C.C. walls are brought
together so as to save the resources. In this innovation, time
tested materials are used and the retaining wall which is
essentially gravity structure provided with reinforced loft,
which is built into it. The placement, geometric
configuration and the design of the loft is through
optimization.
CASE STUDY The site under consideration is Mahindra Vehicle
Manufacturers Ltd., Chakan Industrial Area, Pune. This
type of wall is extensively used at different locations within
the site area. For the present study a wall of 6.0m height is
considered for cost comparison. The cost worked out for
Cantilever wall section, Gravity wall section and Graviloft
wall section.
Cantilever R.C.C. Wall The total height of wall is 6.0m and base width of 4.2m.
The section is shown in Fig.1. The cost worked out per
running meter length of wall in rupees as :
Item Qty. Rate Amount
Excavation 28.8 m3 659 18979.2
PCC 0.44 m3 4761 2094.84
RCC 4.68 m3 5615 26278.2
Reinforcement 281 Kg 48.39 13598.71
Total = 60950.95
Gravity Wall The total height of wall is 6.0m and base width of 4.1m.
The section is shown in Fig.2. The cost worked out per
running meter length of PCC wall in rupees as :
Item Qty. Rate Amount
Excavation 28.2 m3 659 18583.8
PCC 0.41 m3 4761 1952
Plum concret 10.85 m3 3485 37812.2
Total = 58348.06
Graviloft Wall The total height of wall is 6.0m and base width of 1.8m.
The section is shown in Fig.3. The cost worked out per
running meter length of PCC wall in rupees as :
Item Qty. Rate Amount
Excavation 12. m3 659 7908
PCC 3.85 m3 4761 18329.8
RCC loft 0.84 m3 5615 4716.6
Reinforcement 22.46 Kg 48.39 1086.9
Total = 32041.38
For comparison PCC of M15 grade, RCC Concrete M20
grade considered. However, items like disposing excavated
material, back filling, shuttering, expansion joint and weep
holes are not considered.
1068
R. J. Balwan &, Ajitkumar Kumbhar
Fig.1 R.C.C. Cantilever Wall Section
Fig.2 PCC Gravity Wall Section
Fig.3 PCC Graviloft Wall Section
OTHER POINTS COMPARED
Base Pressure – Uniform base pressure distribution on
both sides as against trapezoidal pressure distribution with
large variation in case of cantilever and gravity walls.
Factor of Safety – Factor of safety against overturning and
sliding is the same i.e. 2.0 and 1.5 respectively, which is as
per codal requirement.
Time of Construction – Due to use of this technique
nearly 40% less time required as compared to gravity and
cantilever retaining walls.
Base Width – Lesser base width requires less land
compared to gravity and cantilever walls. This indicates
lesser land acquisition or more land available for user due
to less land locked.
Serviceability in Seismic Condition – Serviceable, Base
pressure remains positive during seismic conditions.
Ease of Construction and Supervision – No skilled
labour, neither special shuttering and supervision required.
Possibility of Wall Separation – Due to provision of lofts,
the wall becomes an integral part of backfill soil, resulting
in nhanced stability.
CASE HISTORIES Following is the list of works where the Graviloft
technology is adopted successfully. This technology
implemented for maximum wall height up to 26 m.
1) Wings walls of Aqueduct on Banda branch canal.
( Fig. 4)
Fig.4 Wings wall of Aqueduct
2) Wings of walls of Box Culvert at Tilari project
3) Guide walls at Lendi project
1069
Graviloft Retaining Wall : A Case Study
4) Divide walls and Guide walls at Amalibari M.I.
Tank
5) Guide walls at Vishnupuri barrage project
6) MSETC sub-stations
7) R.O.B., Pune (Fig. 5)
8) Foriculture Park, Talegaon (Fig. 7)
And so forth.
Fig.5 R.O.B., Pune
Fig.6 Wall at Kondawa, Pune
Fig. 7 Park at Talegaon
CONCLUSION Cost comparison analysis shows that the use of Graviloft
technology is cost saving solution to retain earthwork.
Graviloft wall has been constructed at many places
successfully.
ACKNOWLEDGEMENT The paper is published with the permission of Prof. D. R.
Phatak, who owns the Intellectual Property Rights for the
technology evolved. The authors are grateful to him for
giving encouragement for writing this paper.
REFERENCES
1. Joseph E. Bowels, Foundation Analysis and
Design, Mcgraw Hill Book Company.
2. Narayan V. Nayak, Foundation Design Manual,
5th Ed., Dhanpat Rai Publications.
1070
