Nails To Rock
Nails To Rock
Nails To Rock
P.G. Student, Department of Civil Engineering, Datta Meghe College of Engineering, Maharashtra, India
Professor and Head, Department of Civil Engineering, Datta Meghe College of Engineering, Maharashtra, India
Abstract- Buildings with deep basements and without substantial weight of the super-structure, when constructed within
highly fluctuating rise and fall of underground water level, experiences significant uplift pressure due to buoyancy effect.
Use of pre stressed rock anchor is a prominently accepted technique to fix the structure to the ground against the excess
hydrostatic pressure, when the sound rock is available at the level of basement stitched raft. The efforts are made in this
study to suggest a suitable design approach and arrive at appropriate constitution of various parameters like locking of
anchors to partial capacity, residual load in anchors, spacing of anchors, raft thickness and reinforcement consumption in
raft, to achieve practical and economical solution which will help maintain structure in position.
Index Terms- Deep basement, Buoyancy, Stitched Raft, Pre-stressed rock anchor, lock off load, residual load in anchor.
I. INTRODUCTION
Large scale developments in building construction and
lack of available space on account of cluster
development has produced demand to go deep into the
ground to manage parking and other services of the
building.
III. PARAMETERS
The parameters for this study are selected upon their
contribution in composite design of stitched raft for
hydrostatic uplift and are categorized as follows;
(a) Constant Parameters:
Proceedings of 12th IRF International Conference, 29th June-2014, Pune, India, ISBN: 978-93-84209-31-5
129
Effect of Buoyancy on Stitched Raft of Building Having Three Basements in Presence of Ground Anchors
No.
Spacing of Anchors(Sa)
L/2
L/3
L/4
Raft thickness
Sa/8
Sa/8
Sa/8
Locking of anchors @
100%
80%
60%
15%
No.
30%
Unit
No. of basements
Basement
Foundation
System Details
Spacing Of Anchors
L/2
3
L/3
3
L/4
3
3.5
3.5
3.5
Nos.
m.
m.
Spacing of anchors
m.
4.5
2.25
Proceedings of 12th IRF International Conference, 29th June-2014, Pune, India, ISBN: 978-93-84209-31-5
130
Effect of Buoyancy on Stitched Raft of Building Having Three Basements in Presence of Ground Anchors
Thickness of raft
m.
0.6
0.4
0.3
m.
10.5
10.5
10.5
m.
0.1
0.1
0.1
m.
1.2
1.2
1.2
m.
12.4
12.2
12.1
Uplift Force
Hydrostatic Pressure
kN/ Sq.m.
-124
-122
-121
Downward
Loading
Top PCC
kN/ Sq.m.
2.4
2.4
2.4
Plum Concrete
kN/ Sq.m.
24
24
24
Raft
kN/ Sq.m.
15
10
7.5
kN/ Sq.m.
41.4
36.4
33.9
kN/ Sq.m.
-82.6
-85.6
-87.1
m.
m.
Nos.
m.
0.3
0.3
0.3
kN/ Sq.m.
7.5
7.5
7.5
kN/ Sq.m.
22.5
22.5
22.5
kN/ Sq.m.
20.25
20.25
20.25
kN/ Sq.m.
-62.35
-65.35
-66.85
Nos.
16
1.5
1.5
1.5
190
90
55
Structure
Details
6
Sr.
No.
1
2
3
4
5
6
T.
3
3
3
3
3
3
L/2
L/2
L/2
L/2
L/2
L/3
Locking anchor
@
Sa/8
Sa/8
Sa/8
Sa/8
Sa/8
Sa/8
Proceedings of 12th IRF International Conference, 29th June-2014, Pune, India, ISBN: 978-93-84209-31-5
131
100%
80%
60%
30%
15%
100%
Effect of Buoyancy on Stitched Raft of Building Having Three Basements in Presence of Ground Anchors
7
8
9
10
11
12
13
14
15
Model 7
Model 8
Model 9
Model 10
Model 11
Model 12
Model 13
Model 14
Model 15
3
3
3
3
3
3
3
3
3
L/3
L/3
L/3
L/3
L/4
L/4
L/4
L/4
L/4
Sa/8
Sa/8
Sa/8
Sa/8
Sa/8
Sa/8
Sa/8
Sa/8
Sa/8
80%
60%
30%
15%
100%
80%
60%
30%
15%
Proceedings of 12th IRF International Conference, 29th June-2014, Pune, India, ISBN: 978-93-84209-31-5
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Effect of Buoyancy on Stitched Raft of Building Having Three Basements in Presence of Ground Anchors
B.
Differential Deflection(settlement) in raft
for Various Percentage Of Locking Of Anchors
Variation in the differential settlement (deflection) in
the raft for various condition of locking of anchors is
displayed below in Fig.10.
Fig. 10.
Proceedings of 12th IRF International Conference, 29th June-2014, Pune, India, ISBN: 978-93-84209-31-5
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Effect of Buoyancy on Stitched Raft of Building Having Three Basements in Presence of Ground Anchors
C.
Construction Cost Per Unit Area Of Stitch
Raft for Various Percentage Of Locking Of Anchors
Variation in the construction cost per unit area of the
stitched raft for various condition of locking of
anchors is displayed below in Fig.11.
Fig. 11. Cost Per Sq.m Area of Raft for Various %age of Lock
off Load in Anchor For 3 Basements
[1]
[2]
[3]
IS 10270:1982: Code for Design & Construction Of Prestressed ground anchors, Stressing of Anchor, Clause: 6.7
[4]
[5]
[6]
[7]
CONCLUSION
[8]
[9]
Proceedings of 12th IRF International Conference, 29th June-2014, Pune, India, ISBN: 978-93-84209-31-5
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Effect of Buoyancy on Stitched Raft of Building Having Three Basements in Presence of Ground Anchors
[15] Amit Shrivastava, G.L. Sivakumar Babu, Uplift Capacity
and Performance Assessment of Anchor piles installed to
basement raft : 2012
[16] R.S. Merifield & S.W. Sloan , The ultimate pull out
capacity of anchors in frictional soil :, 2006
Proceedings of 12th IRF International Conference, 29th June-2014, Pune, India, ISBN: 978-93-84209-31-5
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