a study of foundation scour in the east coast of sri lanka due to ...
a study of foundation scour in the east coast of sri lanka due to ...
a study of foundation scour in the east coast of sri lanka due to ...
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A STUDY OF FOUNDATION SCOUR IN<br />
THE EAST COAST OF SRI LANKA<br />
DUE TO TSUNAMI 2004<br />
V. SUTHAGARAN, V. KANDEEPAN,<br />
G. KALATHEEPAN, AND H.N. SENEVIRATNE<br />
DEPARTMENT OF CIVIL ENGINEERING<br />
UNIVERSITY OF PERADENIYA<br />
SRI LANKA
TSUNAMI 2004<br />
• WORST NATURAL DISASTER ON RECORD<br />
• OVER 31,000 DEATHS<br />
• OVER 2 BILLION U.S. DOLLARS DAMAGE<br />
• NEXT LARGEST NATURAL DISASTER ON RECORD<br />
CAUSED ONLY ABOUT 1000 DEATHS<br />
• BROUGHT THE REALITY OF NATURAL DISASTERS<br />
TO SRI LANKANS<br />
• IN TERMS OF PER CAPITA LOSS SRI LANKA WAS<br />
WORST HIT
INUNDATION<br />
MAP
AFFECTED<br />
DISTRICTS
BATTICALOA DISTRICT
GEOTECHNICAL SUMMARY<br />
• MAIN CAUSE OF DAMAGE – SCOUR<br />
• SOME OVERTURNING - TILT<br />
• SOME SETTLEMENT FAILURES<br />
• SOME DRAWDOWN FAILURES<br />
• NO RECORDS OF OTHER PHENOMENON
Scour<strong>in</strong>g<br />
Foundation Settlement
Tilt<strong>in</strong>g <strong>of</strong> Foundation<br />
Drawdown Failure <strong>of</strong> Embankment
Overturn<strong>in</strong>g <strong>of</strong> Build<strong>in</strong>g
AIM:<br />
• To <strong>study</strong> <strong>the</strong> <strong>scour</strong> patterns around <strong>the</strong> <strong>foundation</strong> <strong>of</strong><br />
build<strong>in</strong>gs <strong>due</strong> <strong>to</strong> tsunami wave action.<br />
OBJECTIVES:<br />
• To identify and measure <strong>the</strong> depth, shape and<br />
position <strong>of</strong> <strong>scour</strong> holes<br />
• To analysis <strong>the</strong> effect <strong>of</strong> environment, wave action<br />
and o<strong>the</strong>r fac<strong>to</strong>rs on <strong>scour</strong><strong>in</strong>g<br />
• To <strong>study</strong> suitable <strong>foundation</strong> types for low cost<br />
build<strong>in</strong>gs <strong>in</strong> tsunami areas
DEFINITION OF SCOUR<br />
Scour is def<strong>in</strong>ed as <strong>the</strong> removal <strong>of</strong><br />
hydrodynamic force <strong>of</strong> granular bed material <strong>in</strong><br />
<strong>the</strong> vic<strong>in</strong>ity <strong>of</strong> <strong>coast</strong>al structures.<br />
It occurs whenever <strong>the</strong> hydrodynamic bot<strong>to</strong>m<br />
shear stress is greater than <strong>the</strong> sediment critical<br />
shear stress.
Scour at vertical wall<br />
S m = H max -or- S m = h<br />
S m - Maximum depth <strong>of</strong> <strong>scour</strong><strong>in</strong>g<br />
H max - Maximum wave height<br />
h - Pre <strong>scour</strong> water depth at wall
STUDY<br />
AREA
SITE LOCATION<br />
Location<br />
Lat(E)<br />
Coord<strong>in</strong>ate<br />
Long(N)<br />
No. <strong>of</strong> Houses<br />
Navaladi<br />
081 42 39.7<br />
07 43 38.8<br />
18<br />
Kathankudy<br />
081 42 58.1<br />
07 43 03.0<br />
15<br />
Chettipalayam north<br />
081 47 17.6<br />
07 35 02.6<br />
01<br />
Palamunai<br />
081 44 07.5<br />
07 41 24.1<br />
06<br />
All Divisions<br />
40
GEOTECHNICAL ASPECTS<br />
• NAVALADI AREA CONFINED BETWEEN<br />
LAGOON AND SEA<br />
• ALL AREA FLAT WITH DEEP SAND DEPOSITS<br />
• GROUNDWATER TABLE NOT VERY SHALLOW<br />
(< 2 m)
DATA COLLECTED<br />
• LOCATION OF BUILDINGS – GPS – DISTANCE FROM<br />
SHORELINE<br />
• TYPE OF FAILURE<br />
• SHAPE, DEPTH, AND WIDTH OF SCOUR HOLE<br />
• POSITION OF SCOUR HOLE (SEA/LAND SIDE)<br />
• OBSTRUCTIONS TO BUILDINGS<br />
• TYPE OF SOIL, WATERTABLE POSITION
OBSERVATIONS<br />
OBSERVATIONS<br />
3.4<br />
3.4<br />
10.2<br />
10.2<br />
0.7<br />
0.7<br />
1.2<br />
1.2<br />
40<br />
40<br />
All Divisions<br />
All Divisions<br />
3.0<br />
3.0<br />
9.4<br />
9.4<br />
0.6<br />
0.6<br />
1.2<br />
1.2<br />
06<br />
06<br />
Palamunai<br />
Palamunai<br />
2.5<br />
2.5<br />
5.5<br />
5.5<br />
0.8<br />
0.8<br />
0.8<br />
0.8<br />
01<br />
01<br />
Chettipalayam<br />
Chettipalayam<br />
north<br />
north<br />
4.2<br />
4.2<br />
10.0<br />
10.0<br />
0.6<br />
0.6<br />
1.0<br />
1.0<br />
15<br />
15<br />
Kattankudy<br />
Kattankudy<br />
3.8<br />
3.8<br />
10.2<br />
10.2<br />
0.7<br />
0.7<br />
1.2<br />
1.2<br />
18<br />
18<br />
Navaladi<br />
Navaladi<br />
Average<br />
Average<br />
Maximum<br />
Maximum<br />
Average<br />
Average<br />
Maximum<br />
Maximum<br />
Width (m)<br />
Width (m)<br />
Depth (m)<br />
Depth (m)<br />
No. <strong>of</strong><br />
No. <strong>of</strong><br />
houses<br />
houses<br />
Division<br />
Division
FACTORS INFLUENCING SCOURING<br />
• Shape <strong>of</strong> <strong>the</strong> <strong>foundation</strong> layout<br />
Circular – or - Elliptical<br />
• Distance from shorel<strong>in</strong>e<br />
50 <strong>to</strong> 100 m<br />
• Obstructions <strong>to</strong> <strong>the</strong> build<strong>in</strong>g<br />
Not affect <strong>to</strong> <strong>the</strong> <strong>scour</strong><strong>in</strong>g
Recommended design<br />
Sample 01
Sample 02
Sample 03
THANK YOU