CHAPTER 1: SUB-STRUCTURE
LECTURE 1 - SOIL INVESTIGATIONS
LECTURE 2 - CHOICE OF FOUNDATION IN RELATION TO SOIL CONDITION
LECTURE 3 - SHALLOW FOUNDATIONS: PAD, STRIP & RAFT
LECTURE 4 - BASIC UNDERSTANDING OF PILING DEEP FOUNDATIONS
LECTURE 5 - BASEMENT CONSTRUCTION & WATERPROOFING
LECTURE 2 CHOICE OF FOUNDATIONS IN RELATION TO SOIL CONDITION
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MAJOR TYPES OF SOIL
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Defining Factors: Large particles Dry and gritty to touch Easily drains water Less water retention Warm and airy Even when wet, easily crumbles through the fingers Lacks essential nutrients
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Defining Factors: Fine particles Smooth when dry Sticky when wet Retains water Drains poorly Less spaces to let air pass Rich in nutrients Cool and dense
SOIL TEXTURE TRIANGLE
TYPES OF SOIL
FINE- GRAINED COHESIVE SOILS (eg: silts, clays)
Natural deposit of the finest siliceous and aluminous products of rock weathering
High proportion of voids
High cohesion
High compression
High plasticity
Low permeability
Smooth and greasy
Dries slowly and shrink when dry
COARSE- GRAINED NONCOHESIVE/COHESIONLESS SOILS (eg: sands, gravels)
Siliceous products of rock weathering/deposit of rock fragments
Consists of coarser siliceous caused by rock weathering
Non-plasticity
Lack cohesion when dry
Compress and consolidate when under pressure
Low proportion of voids
High permeability
Medium compression
FACTORS WHICH INFLUENCE THE CHOICE OF FOUNDATIONS
NATURE AND STRENGTH OF SOIL
CONSIDERATION OF ECONOMY AS A WHOLE
NATURE OF STRUCTURE
DISTRIBUTION OF LOADS FROM SUPERSTRUCTURE
TOTAL WEIGHT OF BUILDING AND ITS PARTS
ď ś NATURE AND STRENGTH OF SOIL
A soil’s
strength under loading is dependent on its resistant to: - shear - internal friction - cohesion soil strength/ compressibility = bearing capacity
NATURE AND STRENGTH OF SOIL
Soil is divided into 3 types :
Rock
Soil
Weathered soil (between soil and rock)
Rock - a continuous mass of solid material such as granite and limestone. - can only be removed by drilling and blasting - the strongest and most stable material on which building can be founded
Soil - earth material that is particulate
Weathered Soil
boulders – too large to fit by hand
cobble – slightly smaller
gravel – easily lifted with thumb or forefinger
sand – too small to be picked up individually
fine grained lit or clay – too small to be seen individually
clay – plate shaped, smaller than silt particles with small pores greatly influences the properties of clay soil – referred as ‘cohesive’
Rocks, gravel, sand and many silts – stable soils (Non Cohesive Soils)
Organic soils – unstable soils due to change of properties through bacterial decomposition and change in water content.
Clay – unstable soils under changing subsurface moisture conditions (swells and shrink) (Cohesive Soils)
Properties of Soil - different soils exhibit different properties because of variations in the shape and nature of their particles.
Compressibility – the property of a soil to deform under load by the closer wedging together of the soil particles due to the expulsion of air and water from voids.
Permeability – the passage of water through voids. In sands and gravel (larger voids), water in the soil rapidly flows out and permits the soil particles to consolidate quickly. In clay soils (smaller voids), water must force its way slowly through the fine spaces as pressure is exerted on the soil.
END OF LECTURE THANK YOU