SAN

1. FIELD BLAST STUDIES
SANI P G

2.  Blast Tests
Main purpose is to determine whether the soil at the site will
liquefy under earthquake loading
Predeterminedcharge with electric detonators is installedin a
cased bore hole
Lead wires from detonators are connected with the blaster
Accelerationpickups,pore water pickups and settlement gauges
are placedat regular intervals
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3. Acceleration,pore water pressure and ground settlement at the blast
point are obtainedby extrapolation
The data is then interpreted to obtain the liquefaction potential.
Gupta and Mukerjee (1979) performed blast tests in river
bed having heterogeneous soil profile
 The critical hydraulic gradient of top loose sandy
deposit of 4m depth is 0.8
 Special gelatin was installed at 4m depth in 150mm
diameter cased bore holes
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4. Horizontalaccelerations were measured using acceleration pickups
The pore water pressure were measured at 2.5m depthfrom the
ground surface.
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8. Blast records at different distances are convertedinto equivalent
number of cycles of 0.075g acceleration.
The blast at a distance of 2.9m are equivalent to 19.6 cycles of
0.075g expectedearthquakes.
The pore water pressure developed at distanceof 2.9m and depth
2.5m is 1.74m of water column.
At a depth of 2.5m hydraulic head is 2m.
Actual pore water pressure developedis larger than the measured
value 1.74m
complete liquefactionof site is expectedduringearthquake.
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9. THANKS…
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