24-09-2016, 04:02 PM
1456146228-FOUNDATIONSINPROBLEMATICSOILS.pptx (Size: 777.23 KB / Downloads: 5)
INTRODUCTION
Foundation is a medium that transfers load from super structure to soil
Main component of a structure
Soil has to be studied very carefully
Foundations should be selected accordingly
SOIL BEARING CAPACITY
Load has to be resisted by soil
Soil should have sufficient bearing capacity
Safe bearing capacity is load to be resisted per unit area without displacement of soil
S.B.C=load to be resisted/area
TYPES OF FOUNDATIONS
SHALLOW FOUNDATIONS
Isolated footings
Combined footings
Strap footings
Raft foundation
DEEP FOUNDATIONS
Pile foundation
Pier foundation
Well foundation
caissons
CAUSES OF FAILURES
Expansive soils
Uplift action due to water
Liquefaction(during earth quakes)
Improper investigation of soil
EXPANSIVE SOILS
Black cotton soil is an expansive soil
It is having very low bearing capacity
Presence of mineral called montimorilite is responsible
Pavement designs is extremely difficult with black cotton soils
UPLIFT ACTION
Capillary action may take place if water is present underground
This water lifts the foundation upwards and causes the structure to fail
In b/c soils under reamed pile is provided to prevent this
STABILIZATION TECHNIQUES
Bitumen stabilzation
Cement stabilization
Geo textile and fabrics
Mechanical stabilization
Electrical stabilization
CONCLUSION
Foundations are to be laid on clayey soils as they are better than sandy soils
Site investigations should be properly done for soil
Stabilization of soils should be done only if necessary
While stabilizing with cement the water should be just sufficient to complete hydration