Civil engineering

1. PRESENTATION
ON
EARTHEN DAM FAILURES
BY
P. HARI CHARAN REDDY
207R1A0138

2. INTRODUCTION TO FAILURES OF EARTHEN DAMS
THERE ARE MAINLY 3 TYPES OF FAILURES CAN OCCURE IN EARTHEN
DAMS
1) HYDRAULIC FAILURE
2) SEEPAGE FAILURE
3) STRUCTURAL FAILURE
WHY FAILURES WILL OOCURES IN EARTHEN DAMS ?
Earthfill dams are less rigid and more susceptible to failure. Like most of engineering structures,
earth dams may fail due to various reasons such as faulty design, improper construction and poor
maintenance practices, etc.

3. SEEPAGE FAILURE :
1) Seepage means the slow escape of a liquid or gas through porous material or
small holes.
2) Seepage always occure in the dams. If the magnitude is within the designed
limts, it may not harm the stability of the dam.
3) However, if seepage is concentrated or uncontrolled beyond limts, it will lead to
failure of the dam.

4. CAUSES OF SEEPAGE FAILURES :
1) Piping through Foundation
2) Piping through Dam body
3) Sloughing of Downstream toe

5. Piping through Foundation :
When the foundation of earthen dam consists gravel or coarse sand layers or
fissures etc., the water from upstream will seep through it. The seepage at higher
gradient erode the soil and creates hollow spaces inside the foundation which is
called as piping through foundation. This problem will cause the dam to sink
downwards resulting failure of dam. Hard and impermeable strata should be
selected as foundation for dam to avoid piping through foundation.

6. Piping through Dam body
Piping through dam body will occur due to seepage of water through dam
body. This is mainly due to insufficient compaction of soil used for the dam,
faulty construction of dam, shrinkage cracks, animal burrows in dam body,
etc. This problem will arise mostly near the pipe conduits passing through
dam body. Piping may develop due to seepage along the outer side of
conduit or due to leakage of conduit inside the dam body. To prevent this,
the soil layers around the conduits must be fully compacted as well as the
conduits should not be overloaded.

7. Sloughing of Downstream toe :
IF the downstream toe of dam gets saturated by piping or any seepage
action, it will get eroded and forms small slide or small slump. The slump
will create steeper face which again gets eroded due to seepage and form
slump again. This progressive removal of saturated soil is called sloughing.
This will finally lead to removal of soil from whole downstream face and
makes the dam body thin resulting failure of dam.

8. Consequences of Seepage Failure :