SUBJECT NAME: FOUNDATION ENGINEERING SUBJECT CODE: CE 1306 By R.Navaneethan Lecturer Department of Civil Engineering PITS

FOUNDATION ENGINEERING OBJECTIVE This subject is introduced to students with well organized five units, to let know the basics of soil mechanics through studying the properties and testing methods available for soil in context with Civil Engineering

TOPICS SITE INVESTIGATION AND SELECTION OF FOUNDATION SHALLOW FOUNDATION FOOTINGS AND RAFTS PILES RETAINING WALLS

Foundation Engineering In a broad sense, foundation engineering is a art of selecting, designing and constructing the elements that transfer the weight of structure to the underlying soil or rock. The role of engineer is to select the type of foundation, its design and supervision of construction. Before the engineer can design a foundation intelligently, he must have a reasonably accurate conception of the physical properties and the arrangement of the underlying materials. This requires detailed soil explorations.

Unit I SITE INVESTIGATION AND SELECTION OF FOUNDATION Methods of exploration Sampling Penetration tests Selection of foundation based on soil condition.

Standard Penetration Test Useful in determining properties of cohesionless soil Simple and inexpensive Use a split-spoon sampler

Core Boring

Unit II SHALLOW FOUNDATION Bearing capacity of shallow foundation on homogeneous deposits Factors affecting bearing capacity Methods of minimizing settlement SPT, SCPT and plate load

Bearing Capacity : Modes of Failure Strip footing in dense soil Load q (kN/m2) Settlement (mm) Sudden appearance of a clearly defined distinct failure shape General shear Failure

Unit III FOOTINGS AND RAFTS Types of foundation Isolated and combined footings Mat foundation Floating foundation

Combined Footing Whenever two or more columns in a straight line are carried on a single spread footing, it is called a combined footing. Isolated footings for each column are generally the economical. Combined footings are provided only when it is absolutely necessary, as Where soil bearing capacity is low, causing overlap of adjacent isolated footings, Proximity of building line or existing building or sewer, adjacent to a building column, When two columns are close together, causing overlap of adjacent isolated footings.

TYPES OF COMBINED FOOTINGS

Factors influencing the selection of pile Unit IV PILES Factors influencing the selection of pile Interpretation of pile load test Forces on pile caps Capacity under compression and uplift

Pile Load Test Load imparted to pile in gradual steps to twice design load, as settlement data recorded Often, load removed in steps, too, to produce load-deflection curve Behavior Elastic deformation Buckling Puncture Ensure multiple deflection references, in case one is lost

Pile Load Test

Active and passive states Condition for critical failure plane Unit V RETAINING WALLS Active and passive states Condition for critical failure plane Coloumb’s wedge theory Pressure on the wall due to line load

DESIGN The designed retaining wall must be able to ensure the following : Overturning doesn’t occur Sliding doesn’t occur The soil on which the wall rests mustn’t be overloaded The material used in construction are not overstressed.

TEXT BOOKS Murthy, V.N.S., “Soil Mechanics and Foundation Engineering”, UBS Publishers Distribution Ltd, 1999 Gopal Ranjan Rao, A.S.R.,”Basic and Applied Soil Mechanics”, Wiley Eastern Ltd., 2003   REFERENCES Das, B.M., “Principles of Foundation Engineering, 5th Edition, Thomson Books,2003 Kaniraj, S.R., “Design Aids in Soil Mechanics and Foundation Engineering”, Tata McGraw Hill Publishing Company Ltd., 2002 Bowles, J.E., “Foundation Analysis and Design”, McGraw-Hill, 1994

ASSIGNMENT TOPICS Problems in footings Problems in retaining walls Study of Plastic equilibrium in soils

URL en.wikipedia.org/wiki/Foundation_(engineering) www.gerionline.org/Library/35.pdf www.learnerstv.com/Free-Engineering-Video-lectures-ltv185-Page1.htm www.foundationengineering.info/ www.asce.org/Books.../Art-of-Foundation-Engineering-Practice/ en.wikipedia.org/wiki/Foundation_engineering

SYLLABUS UNIT I SITE INVESTIGATION AND SELECTION OF FOUNDATION Scope and objectives – Methods of exploration-averaging and boring – Water boring and rotatory drilling – Depth of boring – Spacing of bore hole - Sampling – Representative and undisturbed sampling – Sampling techniques – Split spoon sampler, thin tube sampler, stationary piston sampler – Bore log report – Penetration tests (SPT and SCPT) – Data interpretation (Strength parameters and Liquefaction potential) – Selection of foundation based on soil condition. UNIT II SHALLOW FOUNDATION Introduction–Location and depth of foundation – Codal provisions – Bearing capacity of shallow foundation on homogeneous deposits – Terzaghi’s formula and BIS formula – Factors affecting bearing capacity – Problems-bearing Capacity from insitu tests (SPT, SCPT and plate load) – Allowable bearing pressure, settlement – Components of settlement – Determination of settlement of foundations on granular and clay deposits – Allowable settlements – Codal provision – Methods of minimizing settlement – Differential settlement.

UNIT III FOOTINGS AND RAFTS Types of foundation – Contact pressure distribution below footings and raft – Isolated and combined footings – Types – Proportioning – Mat foundation – Types – Use –Proportioning – Floating foundation. UNIT IV PILES Types of piles and their function – Factors influencing the selection of pile – Carrying capacity of single pile in granular and cohesive soil – Static formula – Dynamic formulae (Engineering news and Hiley’s) – Capacity from insitu tests (SPT and SCPT) – Negative skin friction – Uplift capacity – Group capacity by different methods (Feld’s rule, Converse Labarra formula and block failure criterion) – Settlement of pile groups –Interpretation of pile load test – Forces on pile caps – Under reamed piles – Capacity under compression and uplift. UNIT V RETAINING WALLS Plastic equilibrium in soils – Active and passive states – Rankine’s theory – Cohesionless and cohesive soil – Coloumb’s wedge theory – Condition for critical failure plane –Earth pressure on retaining walls of simple configurations – Graphical methods (Rebhann and Culmann) – Pressure on the wall due to line load – Stability of retaining walls.