Unequal Settlement of Subsoil :-
Due to unequal distribution of load on the foundations, varying bearing capacity of the soil, eccentricity of the load, etc., unequal settlement occurs. In order to prevent this, the foundations should rest on rock or hard moorum. Also, it should be seen that the allowable bearing pressure of the soil is not exceeded and proper attention should be given to the eccentricity of the load.
Cause of failure :-
- Uneven distribution of load
- Change in soil Bearing capacity
- Eccentric loading
Remedies measures :-
- The foundation should be supported on a rock or hard surface.
- The foundation should be designed keeping in mind the type of soil.
- The pressure on the soil should not exceed Permissible bearing pressure on it.
Unequal Settlement of Masonry :-
Mortar joints may shrink and compress, which may lead to unequal settlement of the masonry. In order to avoid this settlement, the mortar to be used in the masonry should be stiff, the masonry should be raised evenly and should be watered properly.
Cause of failure :-
- Due to improper curing.
- Height of the wall erected in a single working day exceed 1.5m.
- Motor used in masonry is of poor quality.
Remedies measures :-
- The mortar used in masonry should be exactly stiff and have the required workability.
- The masonry work should be lifted slowly together.
- If cement mortar is used in one day, the height of the wall should not exceed 1.5 m.
- The masonry should be cured properly for 10 days.
Withdrawal of Moisture from the Sub-Soil :-
This occurs at places where there is considerable variation in the height of the water table. The precaution needed to avoid this type of failure is to drive piles up to the hard-rock level.
Cause of failure :-
- Due to movement of water table.
Remedies measures :-
- In such a situation, the footing steps should be lowered down to the hard rock.
Lateral Pressure on the Superstructure :-
The thrust of a pitched roof or wind action on the superstructure causes the wall to overturn. The remedial measure is to provide a foundation of a suitable width.
Cause of failure :-
- Neglecting lateral forces factor during design and construction of structure.
- Insufficient width of foundation
Remedies measures :-
- The foundation of the structure should be kept wide.
- Lateral forces like wind, earthquake, should be taken into consideration while designing the structure.
Horizontal Movement of Earth :-
Very soft soil is liable to give way under the action of load. In such cases it is desirable to construct retaining walls or to drive sheet piles to prevent sliding of earth.
Cause of failure :-
- Presence of water body adjacent to the structure.
- Not considering failure of soil during design of the structure.
Remedies measures :-
- Building a retaining wall.
- Lower the seat piles.
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