DR. JIVRAJ MEHTA INSTITUTE OF TECHNOLOGY

PREPARED BY: AZAD SHAHNAWAZ (130820106001) BHAGAT VINAYAK (130820106002) BHATT DHARMIK (130820106003) BHOYA JIGNESH (130820106004) GUIDED BY: PROF. Rakesh Hingu PROF. Nanak Pamnani

Spread and pile foundation

Shallow foundation When the depth of foundation is less then or equal to the width of foundation, then it is termed as shallow foundation. It is also known as open foundation. A shallow foundation is placed immediately below the lowest part of the superstructure. A footing is a foundation unit constructed in brick work, stone masonry or concrete below the base of the wall or column for the purpose of distributing the structural-load over wide area.

Types The shallow foundation can be classified into following types: Spread footing Combined footing Strap footing Mat or Raft foundation

Spread Footing Spread Footing:- Spread footings are those which spread the super-imposed load of wall or column over larger area. Spread footing support either column or wall.

It may of following kinds Single footing for column Stepped footing for a column Sloped footing for a column Wall footing without step Grillage foundation

Single footing for column A spread footing for a single column is either known as the isolated footing or pad footing. In this case, the footing may consist of simple concrete block projecting out from the column face on all sides. The base dimensions of the concrete base should not be less than twice the appropriate lateral dimensions of the column in that direction.

Stepped Footing for a Column If the column load is more or if the safe bearing pressure of the soil is less, the base area will be large. In such a case, it is necessary to provide masonry offsets, to achieve larger spread, before the load is transferred to the concrete base. The height and width of each offset should be so proportioned that the rate of spread does not exceed the permissible value for the masonry.

Slopped Footing for a Column These are also known as Isolated or Individual column footings. They have the projections in the concrete base. Due to the low bending strength, the footing constructed with brick, stone or plain concrete require considerable depth to be safe to carry heavy loads. The depth of plain concrete footing can be reduced much, by providing reinforcements at its base to take-up tensile stresses.

Wall footing without step It is also called strip footing, which provides a continuous longitudinal bearing. Thus, a spread footing for a continuous wall is called a strip footing As a rule, the width of concrete base should not be less than twice the width of the wall and the thickness should be at least equal to offset.

Grillage Foundation A grillage foundation is an isolated footing generally provided, when heavy structural loads from columns, piers or steel stanchions are required to be transferred to a soil having poor or low bearing capacity. It can be broadly divided into two categories, depending upon the material used: Steel grillage foundation Timber grillage foundation

Steel Grillage Foundation Steel grillage foundation consists of steel joists or beams (Rolled Steel Joists-RSJ) which are provided in single or double tiers.

Timber Grillage Foundation This type of foundation is provided for heavily loaded masonry wall or timber columns. This foundation is specially useful in waterlogged areas, where the bearing capacity of soil and is very low and where the steel beams may get corroded due to subsoil water, the loading on the soil is limited to 50 to 60 KN/ m2 .

Combined Footing A spread footing which supports 2 or more columns is termed as combined footing. When the columns are very near to each other, so that their footing overlap. When the bearing capacity of soil is less, requiring more area under individual footing. It may of following kinds Rectangular combined footing. Trapezoidal combined footing. Combined column-wall footing.

Strap Footing If a Independent footing of two columns are connected by a beam, it is called a strap footing. A strap footing may be used where the distance between the column is so great that trapezoidal footing becomes quite narrow. The strap does not remain in contact with soil and does not transfer any pressure to the soil.

Raft Foundation A raft Foundation is a combined footing that covers the entire area beneath a structure and support all the wall and column. They are used in areas where the soil masses contains compressible lenses or the soil is sufficiently erratic so that differential settlement would be difficult to control.

pile foundation Pile Foundation:- Pile Foundation is that type of foundation in which the loads are taken to a low level by means of vertical members which may be timber, concrete or steel. Pile foundation may be adopted when no firm bearing strata is available and the loading is uneven.

Piles may be of following types End bearing piles Friction Pile Compaction pile Combined end bearing and friction pile

End bearing piles