X.4. Pile foundationDue to the fact that the good foundation soil is exceeded by the presence of the underground car park, the foundation system must be changed from a general mat to pile foundation. A pile foundation consists of two components: Pile cap and single or group of piles. Piles transfers the loads from structures to the hard strata, rocks or soil with high bearing capacity. These are long and slender members whose length can be more than 15m.Piles can be made from concrete, wood or steel depending on the requirements. These piles are then driven, drilled or jacked into the ground and connected to pile caps. Pile foundation are classified based on material of pile construction, type of soil, and load transmitting characteristic of piles.The use of pile foundations as load carrying and load transferring systems has been for many years.Timber piles were used in early days, driven in to the ground by hand or holes were dug and filled with sand and stones. The use of steel pile started since 19th century and concrete piles since 20th century.With the change in technology and industrial revolution, many advance systems have been devloped for pile driving from the invention of steam and diesel pile driving machines.The use of pile foundations is increasing day by day due to non-availability of land for construction. Heavy multi-storyed building are being constructed, and load from these structures can not be directly transferred to ground due to low bearing capacity issue and stability issues of building during lateral load application. So, demand for use of pile foundations are increasing day by day. Due to this demand for piles, there have been many improvements in piles and pile driving technology and systems. Today there are many advanced techniques of pile installation.There are three types of pile foundations according to their construction methods:1. Driven piles;2. Cast-in-situ piles;3. Driven and cast-in-situ piles.

Pile foundation designInput data:Internal forcesNK [kN]

ABCD

15064573458605120

24125--3465

34973--2842

45470453735442350

l0 = embedded length of the pile in the good soil= min(2d;1m) => l0 = 1 mDf= 1 ma) Determine the type of piles: precast pilesPrecast concrete piles are used in the construction of foundations for a wide range of different structures in the civil engineering and building sectors. As precast piles are suitable for all applications and ground conditions, they provide a very cost-effective piling solution. They are quick to install without producing spoil or arising material in the process, providing a further saving on waste disposal costs.Factory production techniques, using high performance precast concrete and rigid reinforcement cages, means that precast concrete piles can tolerate high loadings. Generally, design safety factors for piling are taken to be loadings in the range of 2.0 to 3.0. It is normal to use safety factors at the lower end of the range for precast concrete piles because of the: Enhanced quality control procedures operable in the factory manufacturing environment. Availability of a full product inspection to ensure that no defects are present prior to installation of the pile.Precast piles are generally top driven into the ground using hydraulic drop hammers. Sound levels from modern drop hammers are comparable to other piling systems such as continuous flight auger (CFA). Noise during piling can be further reduced by shrouding the drop hammer. The variety of segment lengths available, along with specialist piling equipment, makes precast piles particularly suited to restricted access and low headroom sites.

Lnec= hV+ hA + hB+ 1 m Df + 0.25 m = 0.5 + 1.6 + 6 + 1 1 + 0.25 = 8.1 m Well choose PA-35-15.00 4 20+ 416 PC52Mcap = 68.5kN*mQcap = 101.50kN

b) Resistance of thepileb.1) Working aloneRc,k= Rb,k+ Rs,k, where Rb,k= Ab * qbkand Ab = d2 = 0.352 = 0.1225 m2qbk = characteristic resistance beneath the tip of the pileqbk = 11640 kPa Rb,k= 1425.9 kNRs,k= U * (li*qski), where U= 4*d = 1.4 m For layer 1: l1 = hA 0.3 = 0.8 mD1 = hv+ hA l1/2 = 1.2 m and qsk1= 36.575 kPa Rs,k,1= 1.4 * 0.8 * 36.575 = 40.964 kN For layer 2:Rs,k,2= U*l2*qsk2l2 = 6 mD2 = hV+ hA+ hB/2 = 4.6 mqsk2 = 54.1 kPa Rs,k,2 = 1.4*6*54.1 = 454.44 kN For layer 3:Rs,k,3= U*l3*qsk3l3 = 8.2 mD3 = hV+ hA+ hB+ l3/2 = 3.2 mqsk3 = 63.15kPa Rs,k,2 = 1.4*8.2*63.15 = 724.962kNRs,k= Rs,k,1 + Rs,k,2 + Rs,k,3 = 1220.366 kNRc,k = 2646.26 kNRt,k= = = 508.49 kN

Design approach D2Rc,d= + = + = 2405.7 kN

Rc,d= = = 2405.7 kN

Rt,d= =

b.2) Working in a groupRc,d,g= mu * Rc,dRt,d,g= mu * Rt,d, where mu = f(r/r0) r = 3d = 1.05 m r0 = li*tgii = and d= 1= 5.25 2 = 7 3 = 0 r01 = 0.074 r02 = 0.737 r03 = 0 r0 = 0.811 mu =0.837Rc,d,g= mu * Rc,d= 2013.57kNRt,d,g= mu * Rt,d = 370.09 kN

c) Number of piles; arrangementn= +1(2) piles=1.3VD = Nk * G+ Gk * G= 53084*1.35+291.6 = 71955 kN n= = 46.45 = 48 pilesd0 = min 1.5d = 0.525 mmin 0.25 mmax 5d = 1.75 m d0 = 1.0 mr = min 3d = 1.05 mmax 10d = 3.5 m r = 2 m