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PataguppaPataguppa
BridgeBridge
Location of the Proposed Bridge
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Ariel View of Project Location
Proposed New
Bridge
Towards Hosanagara
Towards Sagara
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Existing facility:
A Stone masonry arch bridge of 4 spans of
15m in the year 1884 (132year old bridge with open
foundation) .
1940 the bridge was submerged due to the
construction of dam at Hirebhaskara for power
generation.
the height of the bridge was raised to 1783 feet
from 1769 feet by constructing the composite structure
over the arch bridge.
1964 when the Govt. has constructed
Linganamakki dam across Sharavathi River. The
maximum height of water that can be stored at the
Linganamakki dam is 1819 feet leaving the bridge got
completely submerged during full flow of water
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Carriageway Live Loads
a) One / Two lanes of IRC Class A loading.
b) One lane of IRC Class 70R loading (Wheeled / Tracked).
Horizontal Forces due to Water Currents
as per clause 213 of IRC: 6-2000.
Seismic Loading
Seismic forces are considered as per IRC: 6-2000.
Wind Loading
wind at right angles to the bridge or 65 % of right angle to the bridge and
35% along the traffic as per clause 212 of IRC: 6—2000.
Temperature Loading
as per Clause 218 of IRC: 6- 2000.
Earth Presuure
Water current
Wave pressure for the substructure based on the flowing water current has
been considered v=2.00m/sec assumed
Buoyancy
Uplift due to buoyancy considered in accordance with cl. 216 of IRC:6
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Height earth pressure in t Moment in t-m Force for 5.50m
6 4.44 23.8 79.92
7 5.1837 48.1 108.8577
8 5.92163 71.6 142.11912
9 6.666 102.1 179.982
10 7.4437 140.1 223.311
12.5 8.33 273.3 312.375
55.82775
Self weight of pier P8 up to pile bottom=147.35t 78.09375
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OVER ALL VIEW OF P8 PIER WHEN LEANED TOWARDS UPSTREAM SIDE
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Pile work for P8 was completed during may 2013 and Pier was standing and
intact for two years, But on23/06/2015 the pile started tilting and fell down
on 26/06/2015.
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Events occurred since 22/06/2015 to 26/06/2015
•Height of embankment constructed for service road (about
10.50mheight at Pier P8 location ie deepest point of river
bed and center of river) and island for facilitating for driving
of pile and movement of man ,machinery and material for
construction activity was intact and pier P8 was standing
and stable for 2 years after casting pier cap.
•The bund has breached on 22/06/2015 at the location of
pier P8 due to following reasons
due to heavy rain fall in the catchment area in the order of
300 to 400mm from 20/06/2015 to 22/06/2016
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Since the embankment for service road is a
temporary structure, normally the
embankment would not be designed for long
service, thereby side slopes were not designed
for the height of embankment constructed at
work site and slope protection work was not
carried out.
Since the bridge across back water of
Linganamakki dam , the minimum water level
at bridge location being 4.00m from lowest
bed level the embankment could not be
compacted as per required specification.
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The vent way provided for inflow was very
much smaller than the required and as
indicated in above table, the 900mm dia of 5
rows were provided during 2011 and there are
more chances of choking up of these vents ,
thereby it leads to rising of water level on U/S
of bund due to heavy rains in the catchment .
The failure/breach of bund may be due to
internal seepage, slope failure at weak zone
where the pipes were laid at gaurge portion of
river .
The piles of this project were designed as
compression piles to transfer the load coming
from the structure.
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Stage1. On 22/06/2015
The bank and the bed of the river erroded due to
breaching of earthen embankment , and from photo it
can be observed that the soil below the pile cap was
also carried awy by the flash floods. Due to this
accidental event , the soil on one side of the pier was
standing for a considerable height in saturated
condition, which caused the pier unstable due to
destabilising moment acting on pier for a width of
6.00m and height of about 8 to 10m. The pile has
started leaning in the direction of destabilising
moment.
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Stage 2. On 23/06/2015
On 23/06/2015 morining it was observed by
the field people that, pile was leaning towards
Pier P7 considerably, thereby the eccentricity
of pier mass is shifted away from the CG of
pile group . Due to this the additional
destabilising moment added to the moment of
earten bund.There by leaning of pier is
increased due to heavy rain fall is continued
on 23/06/2015.
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Stage 2a. On 24/06/2015 and 25/06/2015
Continuity of leaning of pier P8 was in
progress, since the pier was constructed with
pile foundation and reportedly piles were
socketted into the rock, the pier might have
stood for almost 3 days, otherwise there was a
sudden collapse of pier due to reasons
mentioned below.
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Stage3. On 26/06/2016
On 26/06/2015 finally the pier P8 has fell in the river
due to
the erosion of bed below the pile cap , the piles
towards water became unstable,
destabilising moment due to the enormous earth
pressure,
There are no stabilising moments .
Shifting of CG of pier mass due to tilting.
Tendency of flow of soil along with water towards
deep point, ie; from the side of P9 towards deep point
of river, additional force exerted on the P8.
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Conclusion:
Due to above reasons and natural
calamity the pier has fell before loading
with super structure.
