9 TYPES OF PILE FOUNDATION COMPOSITE PILECOMBINATION OF:STEEL AND CONCRETEWOODEN AND CONCRETEETC
10 PILE CATEGORIES END BEARING PILES Classification of pile with respect to load transmission and functional behaviour:END BEARING PILESThese piles transfer their load on to a firm stratum located at a considerable depth below the base of the structure and they derive most of their carrying capacity from the penetration resistance of the soil at the toe of the pileFRICTION PILESCarrying capacity is derived mainly from the adhesion or friction of the soil in contact with the shaft of the pileCOMPACTION PILESThese piles transmit most of their load to the soil through skin friction. This process of driving such piles close to each other in groups greatly reduces the porosity and compressibility of the soil within and around the groups.
13 PILE CATEGORIESClassification of pile with respect to effect on the soilDriven PileDriven piles are considered to be displacement piles. In the process of driving the pile into the ground, soil is moved radially as the pile shaft enters the ground. There may also be a component of movement of the soil in the vertical direction.
14 Classification of pile with respect to effect on the soil Bored Pile PILE CATEGORIESClassification of pile with respect to effect on the soilBored PileBored piles(Replacement piles) are generally considered to be non-displacement piles a void is formed by boring or excavation before piles is produced.There are three non-displacement methods: bored cast- in - place piles, particularly pre-formed piles and grout or concrete intruded piles.
19 POINT BEARING CAPACITY For Shallow Foundation- TERZAGHISQUARE FOUNDATIONqu = 1,3.c.Nc + q.Nq + 0,4..B.NCIRCULAR FOUNDATIONqu = 1,3.c.Nc + q.Nq + 0,3..B.N- GENERAL EQUATIONDeep FoundationWhere D is pile diameter, the 3rd part of equation is neglected due to its small contributionqu = qP = c.Nc* + q.Nq* + .D.N*qu = qP = c.Nc* + q’.Nq* ; QP = Ap .qp = Ap (c.Nc* + q’.Nq*)Nc* & Nq* : bearing capacity factor by Meyerhoff, Vesic and JanbuAp : section area of pile
20 POINT BEARING CAPACITY MEYERHOFF PILE FOUNDATION AT UNIFORM SAND LAYER (c = 0)QP = Ap .qP = Ap.q’.Nq* Ap.qlql = 50 . Nq* . tan (kN/m2)Base on the value of N-SPT :qP = 40NL/D 400N (kN/m2)Where:N = the average value of N-SPT near the pile point (about 10D above and 4D below the pile point)
22 POINT BEARING CAPACITY MEYERHOF PILE FOUNDATION AT MULTIPLE SAND LAYER (c = 0)QP = Ap .qPWhere:ql(l) : point bearing at loose sand layer (use loose sand parameter)ql(d) : point bearing at dense sand layer (use dense sand parameter)Lb = depth of penetration pile on dense sand layerql(l) = ql(d) = 50 . Nq* . tan (kN/m2)
23 POINT BEARING CAPACITY MEYERHOF PILE FOUNDATION AT SATURATED CLAY LAYER (c 0)QP = Ap (c.Nc* + q’.Nq*)For saturated clay ( = 0), from the curve we get:Nq* = 0.0Nc* = 9.0andQP = 9 . cu . Ap
24 POINT BEARING CAPACITY VESIC BASE ON THEORY OF VOID/SPACE EXPANSIONPARAMETER DESIGN IS EFFECTIVE CONDITIONQP = Ap .qP = Ap (c.Nc* + o’.N*)WHERE:o’ = effective stress of soil at pile pointKo = soil lateral coefficient at rest = 1 – sin Nc*, N* = bearing capacity factors
25 POINT BEARING CAPACITY VESIC According to Vesic’s theoryN* = f (Irr)whereIrr = Reduced rigidity index for the soilIr = Rigidity indexEs = Modulus of elasticity of soils = Poisson’s ratio of soilGs = Shear modulus of soil = Average volumetric strain in the plastic zone below the pile point
26 POINT BEARING CAPACITY VESIC For condition of no volume change (dense sand or saturated clay): = 0 Ir = IrrFor undrained conditon, = 0The value of Ir could be estimated from laboratory tests i.e.: consolidation and triaxialInitial estimation for several type of soil as follow:Type of soilIrSand70 – 150Silt and clay (drained)50 – 100Clay (undrained)100 – 200
27 POINT BEARING CAPACITY JANBU QP = Ap (c.Nc* + q’.Nq*)
28 POINT BEARING CAPACITY BORED PILE QP = . Ap . Nc . CpWhere: = correction factor= 0.8 for D ≤ 1m= 0.75 for D > 1mAp = section area of pilecp = undrained cohesion at pile pointNc = bearing capacity factor (Nc = 9)
29 FRICTION RESISTANCE Where: p = pile perimeter L = incremental pile length over which p and f are taken constantf = unit friction resistance at any depth z
30 FRICTION RESISTANCE SAND Where:K = effective earth coefficient= Ko = 1 – sin (bored pile)= Ko to 1.4Ko (low displacement driven pile)= Ko to 1.8Ko (high displacement driven pile)v’ = effective vertical stress at the depth under consideration= soil-pile friction angle= (0.5 – 0.8)
31 FRICTION RESISTANCE CLAY Three of the presently accepted procedures are: methodThis method was proposed by Vijayvergiya and Focht (1972), based on the assumption that the displacement of soil caused by pile driving results in a passive lateral pressure at any depth. method (Tomlinson) method
32 FRICTION RESISTANCE CLAY - METHOD Where:v’= mean effective vertical stressfor the entire embedment lengthcu = mean undrained shear strength ( = 0)VALID ONLY FOR ONE LAYER OF HOMOGEN CLAY
33 FRICTION RESISTANCE CLAY - METHOD FOR LAYERED SOIL
34 FRICTION RESISTANCE CLAY - METHOD For cu 50 kN/m2 = 1
36 FRICTION RESISTANCE BORED PILE Where:cu = mean undrained shear strengthp = pile perimeterL = incremental pile length over which p is taken constant
37 ULTIMATE AND ALLOWABLE BEARING CAPACITY DRIVEN PILEFS=BORED PILED < 2 m and with expanded at pile pointno expanded at pile point
38 EXAMPLEA pile with 50 cm diameter is penetrated into clay soil as shown in the following figure:NC clay = 18 kN/m3cu = 30 kN/m2R = 30o5 m20 mGWLOC clay (OCR = 2) = 19.6 kN/m3cu = 100 kN/m2R = 30oDetermine:End bearing of pileFriction resistance by , , and methodsAllowable bearing capacity of pile (use FS = 4)