PARAMETERS FOR PILE DESIGN

Muhammad Shakeel Ahmad2007- MS- GEO -13

WHAT IS A PILE WHAT IS A PILE ??

PILES ARE STRUCTURAL MEMBERS PILES ARE STRUCTURAL MEMBERS THAT ARE MADE OF STEEL, CONCRETE THAT ARE MADE OF STEEL, CONCRETE OR TIMBER, AND ARE USED TO OR TIMBER, AND ARE USED TO TRANSMITT THE LOAD OF SUPER-TRANSMITT THE LOAD OF SUPER-SRUCTURE TO THE SOIL SAFELY. SRUCTURE TO THE SOIL SAFELY.

CONDITIONS WHERE PILES CONDITIONS WHERE PILES ARE REQUIRED ARE REQUIRED ??

WHEN THE UPPER SOIL LAYER IS HIGHLY WHEN THE UPPER SOIL LAYER IS HIGHLY COMPRESSIBLE AND TOO WEAK. COMPRESSIBLE AND TOO WEAK.

FOR STRUCTURES SUBJECTED TO HIGH FOR STRUCTURES SUBJECTED TO HIGH WIND/ EARTHQUAKE LOADS.WIND/ EARTHQUAKE LOADS.

IN CASE OF SWELLLING AND COLLAPSIBLE IN CASE OF SWELLLING AND COLLAPSIBLE SOILS.SOILS.

TRANSMISSION TOWERS , OFFSHORE TRANSMISSION TOWERS , OFFSHORE PLATFORM AND BASEMENT MATS BELOW PLATFORM AND BASEMENT MATS BELOW WATER TABLE.WATER TABLE.

LOSS OF BEARING CAPCITY IN CASE OF LOSS OF BEARING CAPCITY IN CASE OF SHALLOW FOUNDATIONS DUE TO EROSION SHALLOW FOUNDATIONS DUE TO EROSION OF SOIL.OF SOIL.

Types of Piles Based Upon Types of Piles Based Upon Method of Construction:Method of Construction:

Bored PilesBored Piles

Driven PilesDriven Piles

DESIGN OF A BORED PILE BY DESIGN OF A BORED PILE BY STATIC METHOD :STATIC METHOD :

QQUU = Q = QSS + Q + QBB

WHERE WHERE QQUU = = ULTIMATE BEARING CAPACITY OF ULTIMATE BEARING CAPACITY OF

PILE PILE QQS S == BEARING CAPACITY OF A PILE DUE BEARING CAPACITY OF A PILE DUE

TO TO SKIN FRICTION SKIN FRICTION QQB B == BEARING CAPACITY OF A PILE DUE BEARING CAPACITY OF A PILE DUE

TO TO END BEARINGEND BEARING

BEARING CAPACITY EQUATION FOR BEARING CAPACITY EQUATION FOR SKIN FRICTION (Qs):SKIN FRICTION (Qs):

QsQsD (D (CL+KP TAN CL+KP TAN L) L)WhereWhereQs = Bearing Capacity Due to Skin FrictionQs = Bearing Capacity Due to Skin FrictionD = Dia of PileD = Dia of PileL = length of pileL = length of pile Angle of Internal FrictionAngle of Internal Friction Adhesion Factor Adhesion Factor C = Cohesion of SoilC = Cohesion of Soil = Coefficient of adhesive friction= Coefficient of adhesive frictionP = PressureP = Pressure

BEARING CAPACITY EQUATION BEARING CAPACITY EQUATION FOR END BEARING (Q p):FOR END BEARING (Q p):

Q pQ pDD22 Nq P Nq PWhereWhere

Qp = Bearing Capacity Due to End BearingQp = Bearing Capacity Due to End Bearing

D = Dia of PileD = Dia of Pile

Nq = Bearing capacity FactorNq = Bearing capacity Factor

P = Pressure P = Pressure

EXTRACTION OF EXTRACTION OF PARAMETERSPARAMETERS ::

For C & For C & LABORATORY TESTS:LABORATORY TESTS:

1) Unconfined Compression Test: 1) Unconfined Compression Test: Used to find CUsed to find C2) Direct Shear Test:2) Direct Shear Test: Used to find Used to find

3) Triaxial Test:3) Triaxial Test: Used to find C & Used to find C &

FIELD TESTS:FIELD TESTS:

1)1) Cone penetration Test (CPT): Cone penetration Test (CPT): Used to find C & Used to find C & 2) Standard penetration test (SPT):2) Standard penetration test (SPT): Used to find C & Used to find C &

But before drawing this graph we should know, how But before drawing this graph we should know, how to find N to find N corrected corrected

N corrected = CN corrected = CNN N N

CCN N =Adjustment for effective overburden pressure = =Adjustment for effective overburden pressure = (95.76/Po’)(95.76/Po’)0.50.5

N = Field No. of blowsN = Field No. of blows

Po’ = Overburden PressurePo’ = Overburden Pressure

= = Er / Erb = Er / 70 =55/70Er / Erb = Er / 70 =55/70

= = Rod length correctionRod length correction

= = Sampler correctionSampler correction

= = Bore hole dia CorrectionBore hole dia Correction

TABLE TABLE TOTO FIND N corrected FIND N corrected

SPT PROFILESPT PROFILE

SPT PROFILE WITH SPT PROFILE WITH FACTORSFACTORS

TABLE TO FIND TABLE TO FIND

TABLE TO FIND “C”TABLE TO FIND “C”

GRAPH TO FIND GRAPH TO FIND

GRAPH TO FIND NGRAPH TO FIND Nqq

DIAGRAM TO FIND DIAGRAM TO FIND PRESSUR (P)PRESSUR (P)

ConclusionsConclusions

Hence after finding these factors the Hence after finding these factors the Ultimate bearing capacity can be found Ultimate bearing capacity can be found as:as:

QQUU = Q = QSS + Q + QBB

QQUU D (D (CL+KP TAN CL+KP TAN L) + L) + DD22 Nq P Nq P

QQallall = Q = Qu u / FOS/ FOS

FOS = 2.5 – 4.0FOS = 2.5 – 4.0

THANKSTHANKS

ANY ANY QUESTIONSQUESTIONS