MATERIALS AND CONSTRUCTION I FOUNDATION SOFIA SEBASTIAN FOUNDATION

MATERIALS AND CONSTRUCTION I FOUNDATION SOFIA SEBASTIAN

FOUNDATION Function – To transfer the structural loads from the building to the ground Wood framed house – foundation reaches through the topsoil to the underlying soil Masonry, steel or concrete building – foundation to the strong soil or rock Requirements of the foundation 1. Safe against a structural failure (carry the weight of the building) 2. Must not settle

Settlement in foundation • Settlement is the gradual sinking of a structure as the soil below its foundation consolidates after loading. • On dense, granular soils, such as coarse sand gravel, this consolidation is usually slight and occurs quickly as loads are applied. • When the foundation soil is a moist, cohesive clay, which has a relatively large percentage of voids, consolidation can be quite large and occur. Building slowly over a longer period of time. Construction I Sofia Sebastian 3 3

Differential Settlement in foundation • Differential settlement is the relative movement of different parts of a structure caused by uneven consolidation of the foundation soil. • This can cause a building for cracks to occur in its foundation, structure, or finishes. Building Construction I Sofia Sebastian 4 4

CLASSIFYING EARTH MATERIALS ROCK – continuous mass of solid mineral material strongest material for foundation eg. granite, limestone – removed by drilling and blasting SOIL Soil is a general term referring to any earth material too large to lift by hand or requires two hands to lift - boulder

whole hand to lift a particle - cobble lifted easily between thumb and forefinger – gravel >4. 75 mm soil particles can be seen but are too small to be picked up individually - sand (4. 75– 0. 075 mm) Silt particles - Too small to be seen with the unaided eye 0. 075– 0. 005 mm Clay particles are plate-shaped Less than 0. 005 mm gravel

EXCAVATION Soldier beams and lagging as seen in horizontal section

THREE TYPES OF SHEET PILING 1. Timber sheet piling 2. Steel sheet piling 3. Precast concrete sheet piling

FOUNDATIONS a building consists of three major parts: the superstructure, which is the above ground portion of the building; the substructure, which is the habitable below-ground portion; and the foundations, Superstructure, substructure, and foundation. The substructure in this example contains two levels of basements, and the foundation consists of bell caissons.

Types of Foundations Shallow Column footing Strip foundation Building Construction I Deep Raft foundation Sofia Sebastian Pile foundation Caisson foundation 10 10

Strip footing/ Wall footing Combined footing Column footing/ Pad foundation Shallow foundations -transfer the load to the earth at the base of the column or wall of the substructure. Mat foundation/ Raft foundation

Types of Shallow Foundation Concrete strip foundation 1. Used for load bearing masonry structure 2. Consist of continuous mass concrete strips poured in the bottom of trenches 3. This concrete strip is of uniform width and depth 4. Depending on soil depth – the maximum depth – 90 cm Building Construction I Sofia Sebastian 12 12

Column/ Pad/ Isolated foundation 1. To support concrete columns 2. Square concrete pad foundation distributes the load evenly on the ground Building Construction I Sofia Sebastian 13 13

Raft/ Mat foundation 1. For soil which has poor bearing capacity 2. When the building loads are quite small and the cost of digging separate foundation is eliminated Building Construction I 1. The over-site concrete slab becomes the raft foundation 2. Slab can be thickened at the edges with an edge beam and thickened underneath internal load bearing walls 3. Mesh reinforcement increases the strength of the raft foundation and distributes the pressures of the building loads evenly Sofia Sebastian 14 14

Deep foundations 1. piles (15 cm diameter) or 2. caissons (45 cm -90 cm diameter), penetrate through upper layers of incompetent soil in order to transfer the load to good bearing soil or rock deeper within the earth.

Caisson, or drilled pier Caissons are concrete cylinders poured into drilled holes. They reach through weaker soil (light shading) to bear on competent soil beneath. end bearing caisson is belled when additional bearing capacity is required. socketed caisson is drilled into a hard stratum and transfers its load weaker soil stronger soil

PILE - forcibly driven into the earth rather than drilled and poured. If it is driven only into softer material and a good frictional resistance between the which it is driven; in this case, it is known as a friction pile. • For non cohesive soils, • subsurface water conditions, or • excessive depth of bearing strata Timber pile a tree trunk with its branches and bark removed beaten into the earth with repeated blows of a heavy mechanical hammer. If a pile is driven until its tip encounters firm resistance from a suitable load bearing stratum such as rock, dense sands, or gravels, it is an end bearing pile.

PILE FOUNDATION Piles are usually driven closely together in clusters of 2 -25 piles each. The piles in each cluster are later joined at the top by a reinforced concrete pile cap The pile cap distributes the load of the column or wall above among the piles An elevation view of a pile cap, column, and floor slab.

Pile Materials Piles may be made of timber, steel, concrete, and various combinations of these materials Timber piles they are economical for lightly loaded foundations. they cannot be joined during driving and are, therefore, limited to the length of available tree trunks

Steel piles Two forms of steel piles are used, H-piles and pipe piles. H-piles are special hotrolled, wide-flange sections, 20 to 35 cm deep any convenient lengths Steel pipe piles have diameters of 20 to 40 cm Minipiles, also called pin piles or micropiles, are a lightweight form of steel piles made from steel bar or pipe 5 to 30 cm in diameter.

concrete piles - precast or site cast Precast concrete piles are square, octagonal, or round in section reinforced Advantages high load capacity, an absence of corrosion or decay problems, A site cast concrete pile is made by driving a hollow steel shell into the ground and filling it with concrete.

Retaining wall holds soil back to create an abrupt change in the elevation of the ground. must resist the pressure of the earth that bears against it on the uphill side.

Retaining walls may be made of masonry, preservative-treated wood, coated or galvanized steel, precast concrete, or, most commonly, sitecast concrete.