Sub structure

SUBSTRUCTURE

Generally there are two major components of a building which are substructure and super structure. The substructure is a part of the building that is built below the ground level whereas superstructure is the part of the structure that is constructed above the ground level. A foundation is an element of a structure which connects it to the ground and transfers loads from the structure to the ground. Foundation is generally considered either shallow or deep

Foundation provide the structure’s stability from the ground. Main purposes of foundations are:

 · To distribute the weight of structure over a large area in order to avoid overloading           the underlying soil

· To anchor the structure against natural forces including earthquakes, floods, frost    heaves and wind

· To provide a level surface for construction

· To anchor the structure deeply into the ground

· To prevent lateral movements of the supported structure

Foundation depends on the,

· Ground condition

 · Groundwater condition

· Site, environment

· Structure of building

Foundation types

Ø  Shallow foundation

                         · Strip foundation

                         · Pad foundation

                         · Mat foundation

Ø  Deep foundation

                        · Pile foundation

                        · Slurry foundation

 

SCREED

 Screed is a thinner layer of concrete which is typically poured over a base floor to help form a smooth floor coating to provide a strong foundation for the top floor. 50mm thickness of G15 concrete was use for screeding at our site.

The screeds primary purpose, using one part cement to three to five parts sharp sand, is to give a smooth and level floor on which to lay your chosen floor finish. The thickness of the screed allows it to take up normal variations in flatness and levelness of the base on which it is laid. The mix should be fairly dry. The way to tell if you have it right is to grab a handful of mixed screed and squeeze. The mix should stay in one firm lump in your hand but very little liquid, if any, should come out.

                                                           Figure 4.1-screed concrete

 

REQUIREMENTS OF A GOOD FOUNDATION

The foundations shall be constructed to sustain the dead and imposed loads and to transmit these to the sub-soil in such a way that pressure on it will not cause settlement which would impair the stability of the building or adjoining structures.

Foundation base should be rigid so that differential settlements are minimized, Specially for the case when super-imposed loads are not evenly distributed.

Foundations should be taken sufficiently deep to guard the building against damage or distress caused by swelling or shrinkage of the sub-soil

Foundations should be so located that its performed may not be affected due to any unexpected future influence.

Foundation should be strong and designed with safety factor so that structure may not be damaged due to unexpected effects.

 

 SOIL COMPACTION

 Compaction procedure of soil,

1.    Material transport by truck

2.    Laying by excavator

3.    Rammer compacted

4.    Plate vibrator compacted

5.    5Ton Roller compacted

6.    1Ton Roller compacted

7.      Checking degree of compaction                                                 

                                                                                                Figure4.2-soil compaction