STRIP FOUNDATION 
Typical use
Strip foundation normally provide for loads bearing walls, and for rows of column which are space so close that pad foundation would nearly touch each other. 
Advantages & Disadvantage
It is more economic to excavate and concrete the strip foundation that to work in a large number of individual pits. In fact, it is often though to be more economical to provide a strip foundation whenever the distance between the adjacent square pads is less than the dimension of the pads, and for ease in construction closed spaced pad foundation can be formed by inserting vertical joints in a continuous strip of concrete. This foundation won't applied for low bearing capacity soil. The working procedur is too much such as diging, framing and other is the weakness. 
Typical parameter
The width depends on the hardness of soil and the load on it. The minimum strip width is 450mm. Its enough for two story building on the normal standard soil. The minimum dept is 150mm 
Narrow strip or Deep strip footing 
This type foundation is used for normal soil and normal loads which just needs 0.9m dept , cheep in cost construction. 
The essential feature of the narrow strip foundation is that the trench is too narrow to be dug by labours working in trench. It depends for its success in the ability of a mechanical excavator, such as a light tractor-mounted back-actor with a narrow bucket to dig the trench, which must be self-support until it can be backfill with concrete.
It can’t be economical be use in very soft clays or water bearing sand which support by close timbering.
 
 
Wide strip footing 
are necessary where the bearing capacity is low enough to necessitate where the bearing capacity of the soil is low enough to necessitate a strip so wide that transverse bending occur in the projecting portion of the foundation beam and reinforcement is required to prevent cracking. Fr heavy loads on it , the wickedness is shear force under the concrete footing should overcome by steel bar. 
 
Stepped foundation 
It need no necessary be at the same level through the building. The step should be lap for a distance at least equal to the thickness of the foundation or twice the height of the step whichever is the greater. The step should not greater height than the thickness foundation unless special precaution are taken. 
 
Reinforced concrete strip foundation 
They are likely to show an advantage in cost over unreinforced concrete where weak soil and unreinforced loading and heavy wall loading require a width strip at a comparative shallow depth. Reinforced in longitudinal bars is also desirable in strip foundation on highly variable soils when the foundation is enable to bridge over local weak or hard spot in the soil at foundation level or when there is no change in loading. The main reinforcement takes the frames of bars at he bottom of the slab. The slabs also design to withstand shear and stress. 
Bending moment, 
Mb = ( qn x b2 )/2 kNm per m length of wall 
Shear stress, 
S = ( qn x b’ )/d N/mm2 

RAFT FOUNDATION 
Characteristic
Raft foundation are required on soil of low bearing capacity, or where structural column or other loads areas are so close in both direction that individual pad will nearly touch each other. The function of raft foundation are to spread the load over as wide an area as possible, and to give a measure of rigidity to the sub-structure to enable it to bridge over local areas of weaker or more compressible soil. The degree of rigidity given to the raft also reduces differential settlement. It is useful in reducing different settlement on variable soils or there is a wide variation in loading and adjacent column or other applied loads.
Typical use
Rafts are used to bridge over soft spots if the the spots are very localised and to reduce the average pressure applied to the soil. Raft foundation can be used as a matter of constructional convenience in structure supported by a grid of fairly closed spaced columns. In such case, an overall raft will avoid obstruction of the site by a number of a individual excavation with their associated heaps of spoil. Some designer work on the rule that if more than 50% of the area of the structure is occupied by individual pad or strip foundation it will be more economical. Normally built at for support construction at low bearing capacity such as abondon mining site or at the slopping site which are refilled or not.
Advantages
It may be more economical to excavate the site to a level formation, construct individual close spaced pad foundation and then refill them. Basement with stiff slab or slab and beams floors are forms of foundation rafts; these and the special case of buoyancy rafts. Design of raft to counteract the effect of mining subsidence. The structure can protect the structure from failure if there is settlement or movement of the soil base because the raft base can hold the super structure.So it suitable for soil such as abandon mining site .
Disadvantage
A lot of conrete inquired for base at the low density capacity soil by adding the thickness of the base. The footing should construction on 150mm filled sand to avoid racking from horizontal raft footing should increase by construction side beam reinforcement increase the depth of raft wasn’t give an efficient increase of foundation strength
Plain slab rafts 
Typical Use  : It can be use in ground condition where large settlement are not anticipated and hence a high degree of stiffness is not required. Used for construction at refilled slopping land.
Characteristic : A layer of mesh reinforcement in the top and bottom of the slab is usually provide to resist bending moment due to hogging or sagging deflection at any point in the slab. It is usually to conceal the whole of the slab below finished ground level. Thus the top of the slab is placed at a depth of 100-150mm to allow for minor variation in ground surface level.
Materials : The slab can be either be cast directly on the soil or on a thin layer of blinding concrete. The waterproofing membrane is provide above the slab and is lapped with the damp proof course. 
 
Parameter : For raft slab 200mm thick suitable for a light building, the resulting foundation depth of 300-350 mm below ground level will be satisfactory for soil which are not susceptible to frost heave. In frost susceptible soil the periphery of the slab can be construct on the layer of lean concrete or compacted granular fill to provide an exterior foundation depth of 450mm as a precaution against frost heave. Some what greater depth are require in areas subject to severe frost. Where the flat slab has its upper surface below ground level it is necessary to provide a separate ground floor slab on a layer of lean concrete or compacted fill. 
 
Precaution are then necessary against rain driving beneath the wall or the external cladding of the structure. The ground floor slab is made an integral part of the rafts, and by stepping down the peripheral parts of the slab a cut off is provide against the ingress of water to the ground floor. A stiff beams can be formed integrally with the stepped down portion of the raft and its projecting toe. In a construction of a lesser stiffness the edge beam is cast separately from the slab when it perform structural as a wide strip foundation. In soil of high to very high compressibility such as peaty clays or loose recently deposited fill material, a more massive thickening should be provided to accommodate the stiffer beams with a more rigid connection to the slab.
 
Slab and beams rafts 
 These foundation is used as a foundation for heavy building where stiffness is the principle requirement to avoid excessive distortion of the super structure as a result of variation in the loads distribution over the raft or in the compressibility of the support soil. Usage : oil storage tanks for refineries, gathering ground, fuel depots, etc. should be avoid deflexion and cracking of a concrete slab could cause excessive stresses to develop in the bottom plates. The base is to prevent surface or sub-soil water from collecting around the plate. Material for base are bitumen sand mixture, crushes brick, stone, chalk, gravel sand mixture. 
 It can be design as down-stand beam and upstand-beam type. The downstand beam has an advantage of providing a level surface slab which can form the ground floor of the structure.It is suitable for firm to stiff clays which can stand for limited periods either without any lateral support or with widely spaced timbering. 
It is necessary to construct the beam in a trench which can cause difficulty in soft and loose ground when the soil require continuous support by sheeting and strutting. It would difficult when the trench are excavated in water bearing soil requiring additional space in the excavation for sub-soil drainage and sumps. 
The up-stand beam design ensures that the beam are construct in clean dry condition above the base slab. Excavation has to be undertaken in water bearing soil it is easier to due with the water in large open excavation than in the confines of narrows trenches. 
Its design required the provision of an upper slab to form the ground floor of the structure. This involves the construction and removal of soffitt formwork for the upper slab, or the alternative of filing the spaces between the beams with the granular material to provide a surface on which the slab can be cast. Priciest concrete slab can be use for the top decking but these require the addition of an insitu concrete screed to receive the floor finish. 
Stiffened edge raft
It is suitable for foundation of single or two story houses on weak compressible soil or loose granular fill materials. To withstand large settlement on made ground. The ground floor slab is made an integral part of the raft, and by stepping down the peripheral part of the slab a cut off is provided against the ingress of water to the ground floor. In a construction of lesser stiffness the edge beam is cast separately from the slab when it perform structurally as a wide strip foundation. In soil of high an very high compression 

PAD FOUNDATION 
is a structure reinforced concrete slab that support a number of columns distributed in both horizontal directions or that supports uniform pressure as from tank. 
Unreinforcemnent pad foundation 
The design method of Unreinforcemnent and reinforcement concrete pad foundation are similar in principle to those described in the preceding pages for strip foundation. Thus the minimum size of the pad is given by the practical requirement of being able to excavate by hand to the requirement depth and level off the bottom and to lay brick or fix steel wood for the columns. The thickness of Unreinforcemnent concrete pad foundation is given by the necessity of preventing development of tension on the underside of the base or reducing it to a small value. The consideration for determining the choice of stepped or sloping foundation or a plain rectangular section are the same as those describe for strip foundation
Reinforced pad foundation
Parameter : Method of design is as follow : (a.)determine the base area of the foundation by dividing the total loads of the column and base by the allowable bearing pressure on the soil. (b.)determine the overall depth of the foundation required by punching shear, based on the column loads. (c.)select the type of foundation to be used, i.e. simple slab, sloping upper surface. Assume dimension of the slope. (d.)check the dimension by computing beam shear stress at critical section, on the basics that diagonal shear reinforcement should not be provided. (e.)compute bending moment and design the reinforcement. (f.) check bond stresses in steel. (g.)Calculation of required thickness of pad to resist punching shear
 
Continuous pad and beam foundation 
these foundation is a row of column as a row of pad foundation with only a joint between each pad. Continuous beam foundation may be require to bridge over weak pockets in the soil or to prevent excessive differential settlement between adjacent columns. The advantages of these foundation are ease of excavation by backacter or other machine; any formwork required can be fabricated and assembled in longer lengths; and there is improve continuity and ease of access for concreting the foundation; added advantage of providing strip foundation for panel walls of the ground floor of multi-story framed building.

GRILLAGE FOUNDATION 
Grillage foundation when very heavy loads from structural steel columns have to be carried on a wide base, and where the overall depth of the foundation is restricted (to enable the base slab to be sited above the ground water table, for example) a steel grillage may be require to spread the loads. The girder of the lowermost tier are design to act as cantilever carrying as a distribution loading equal to the bearing pressure on the foundation slab. 
The upper distribution the columns loads on the lower tier. An intermediate tier may be require. In large grillage the girders in each tier are located by tie bolts passing through holes drilled through their webs with gas barrel spacer threaded over the bolts between the web. 
 
Attention must be given to the stability of the girder webs in bearing under concentrated loading from the columns and upper tier of girder. Web stiffeners should be provide as required. Adequate space must be provide between girder flanges to allow the concrete to flow between and underneath them. The grillage must be set very accurately in location and must be quite level before the concrete is placed, and it must not be allowed to move during concreting, since any errors due to inaccurate setting or displacement will be highly expensive to rectify once the concrete has hardened. 
Foundation to structure steel column the traditional design of the bases of structural steel columns consisted of a rectangular steel base plates, rigidly connected to the stanchion by gusset and angle, while holding-down bolts secure the plates to the concrete foundation. The general adoption of welding of steel structure has led to a reduction in the size of base plates. The use of hinged ends to column in such structure as portal framed building and guyed masts permit base plates of minimum area, which are then governed in size by the allowable bearing pressure which can impose in the concrete. BS CP111 is the permissible stress on the surface of the foundation and state that the maximum stresses resulting from concentrated loading. The permissible distributed stress is define as 25 % of the works cube crushing strength or not more than 10.5n/mm2, whichever is less.

BASEMENT & BUOYANCY RAFTS FOUNDATION 
General principle of design Buoyant foundation and Basement foundation this type of foundation have same principle with raft foundation but it have an additional and important function that they utilise the principle of buoyancy to reduce the net load on the soil. In this way the total settlement of the foundation is reduced and it follows that the differential settlement are also reduced. 

Buoyancy is achieved by providing a hollow sub-structure of such of depth that the weight of the soil removed in excavation for it either balances or is only a little less than the combine weight of the super-structure and sub-structure. 

 
A basement is, in effect, a form of buoyancy raft, it is not necessary design for that purpose. Fluctuation in the water table affect the buoyancy of the foundation. Reconsolidate of soil has swelled as a result of the removal of overburden pressure in excavating for the sub-structure is another factor causing settlement of a buoyancy. 
 
Ground pumping station - uplift may be resist by the anchor pile which can take the form of steel rod grouted into hole drilled in into the rock. Drag down effect on deep foundation - the reconsolidate of this disturb soil will again cause a drag down effect on the wall. 

Function to provide additional space to the owner and the fact it reduce the net bearing pressure and advantages is taken. The buoyancy foundation is design solely for the purpose of providing support to the structure by the buoyancy given by the displaced soil without regard to utilising the spaces for other purpose. The structure support the power station and other plant installation

Problems maintaining buoyancy in ground condition which require the cell to be watertight. Asphalt tanking and other membrane protection is not feasibility where the raft re construction in the form of caisson, and any water finding its way through crack in the exterior walls or base should remove by pumping. Basement foundation or box foundation this structure must design to allowed the sub-structure to be used for various purpose such as warehouse storage or underground parking.

Principle of design 
  • In excavation supported by a contiguous bored pile wall construction in advance of the main excavation. 
  • in excavation with sloping sides 
  • in excavation support by timbering or sheet piling

    in excavations support by a reinforced concrete diaphragm wall construct in advance of the main excavation. 

Piled basement 

the function of the pile is transfer the loading to stronger and less compressible soil at greater depth, or possible transfer the loading to bedrock or incompressible strata. The pile also have effect of stiffening the raft and reducing of ground heave, there by reducing differential settlement. 

 
The structural design of basement 

1. earth pressure and earth resistance

  • k = coefficient of the earth 
  • g = density of soil 
  • d = depth below ground level 
  • k = ka coefficient for active earth pressure if the wall is to yield deflexion (TABLE Ka)
  • k = kR coefficient for earth pressure at rest if the wall is to yield deflexion (TABLE KR)
  •  
    2. structural design
    Tanking material - three coated of hot mastic asphalt trowelled on the surface, or several later of bituminous felt. Which covered by BS 1418, Mastic asphalt for tanking and damp proof course (natural rock asphalt aggregate) ; BS1097, Mastic asphalt for tanking and damp proof courses (limestone).
    Application of tanking BS CP 102:1963, protection of building against water from the ground.
  • foundation must keep dry 
  • horizontal asphalt should be protect by 50mm cement-sand-mortar laid as soon as each section of the asphalt is complete, to protect the asphalt against damage by traffic, building material, and reinforcement bar. 
  • the asphalt should be continuous and it should be therefore be taken below all column. 
  • if it is applied to backing wall, the space between the inside of the asphalt and the inner wall should be solidly grouted to prevent movement under external water pressure. 
  • where the asphalt is applied to the external surface of the retain wall, a working space of 0.6m should be provided, and a 100mm thick protection wall should be build outside the asphalt to protect it from damage by sharp stones, bricks, and similar material in the back filling. 
  • for external applied asphalt, a horizontal set off at least 150mm wide should be provided to make satisfactory double angle fillet and connection to be form with the vertical asphalt. 
  • internal and external angles should be suitable splayed to allow the asphalt to be carried evenly round the angle without variation in thickness. 
  • brickwork should have all horizontal joint raked out and brushed clean to provide a good key for asphalt ; concrete should not have a smooth surface. 
  • asphalt tanking should be applied in the three coats to a total thickness of not less than 30mm for horizontal work and not less than 20mm for vertical work. 
  • . internal should be provided with asphalt angle fillets applied in 2 coats and finishing approximately 50mm wide on the face.

  • PIER AND CAISSON FOUNDATION 
    Pier and caisson foundation 
    This foundationis a heavy structure member acting as a massive strut, widely describe as a pad foundation and the buried columns above it which are construction insitu in a deep excavation. Caisson : a structure which is sunk through ground or water for the purpose of excavating and placing the foundation at the prescribe depth and which subsequently becomes an integral part of the permanent work. 
    Caisson, box : a caisson which is closed at the bottom but open to the atmosphere at the top.  Caisson, open : a caisson open both at the top and bottom.  Caisson, pneumatic : a caisson with a working chamber in which the air is maintenance above atmospheric pressure to prevent the enter of water into the excavation.  Monolith : an open caisson of a heavy mass concrete or masonry construction, containing one or more well for excavation. is to enable the structural loads to be taken down through deep layer of weak soil on to a firmer stratum. Pier support a bridge over the water way. 
     
    Used in river and maritime construction to be taken below zone of soil affected by scour. They fulfil a similar function to pile foundation, the main deferential is method of construction .
    Design parameter · bearing pressure for pier foundation and caisson calculate from shear strength and density of the soil. · skin friction (detail) · negative skin friction : can count from table skin friction · pier foundation and caisson on rock · resistance of pier foundation and caisson to lateral loads 
     
    Type of caisson 
    Box caisson are structure with a closed bottom designed to be sunk on to prepared foundation below water level. Suitable for sites where erosion can undermine the foundation, but they are eminently suitable for foundation on a compact inerodible gravel or rock which can trimmed by dredging can be founded on an irregular rock surface if all mud or loose material is dredge away and replaced by a blanket of sound crush rock. Where the depth of soft material is too deep for dredging they can be found on a pile raft. 
     
      
    Open caisson and monolith suitable for foundation in river and water way where the predominating soil consist of soft clays, silts, sands or gravel since these materials can be readily excavated by grabbing from the open well and they did not offer high resistance in skin friction to the sinking of the caisson. disadvantage is the process of grabbing under water in loose and soft material cause surging and inflow of material beneath the cutting edge with consequent major subsidence of the ground around the caisson. Open caisson are unsuitable on sites where damage might be cause by subsidence beneath adjacent structure. Monolith are essentially open caisson of reinforcement or mass concrete construction with heavy wall. They are unsuitable due to their weight, for sinking in deep soft deposits. Mainly use for quay well where their massive construction and heavy weight is favourable for resisting overturning from retained back filling and for withstanding impact force from berthing ship.
      
    Materials steel in the form of a skin plating which is subsequently fill with concrete. The concrete in the lower part of the shoe should be high quality. Cast iron is only used for open well caisson sunk by assembly of bolted segments on a cutting shoe, the segment being built up at ground level as the caisson continuous to sink to its founding level. Due to the high of special casting, cast iron segmental caisson are not used in preference to steel plate or precast concrete segmental caisson.

    PILED FOUDATION 
    Pile are relative long and slender members used to transmit loads through soil strata having a high bearing capacity to deeper soil or rock strata having a high bearing capacity. Also used in normal soil to resist heavy uplift forces or in poor soil conditions to resist horizontal loads. classification - if the stratum for foundation piles is a hard and relatively impenetrable material such as rock or a very dense sand and gravel, the piles derive most of their carrying capacity from the resistance of the stratum at the toe of the pile.
     
    First three piles are displacement piles since the soil is displaced as the pile is driven or jacked into the ground. In all form of bore pile and in some forms of composite piles the soil is first removed by boring a hole into which the concrete is placed or various type of precast concrete or other proprietary units are inserted. The basics different between displacement and non-displacement piles required a different approach to the problems of calculating carrying capacity.
    In all cases where piles are support wholly by soil and are arranged in group, the steps in calculating allowable pile loads are : · determine the base level of the piles which is required to avoid excessive settlement of the pile group. · Calculate the required diameter of pile. · examine the economics of varying the number and diameter of the piles in the group to support the total load on the group. 
     
    Behaviour of pile group if piles are taken down to a hard incompressible stratum is the settlement of a group of piles equal to that of single pile under the same working load as each pile in the group. If piles are driven in a compressible bearing stratum (stiff clay) or relatively incompressible (a dense sand ) but is underlain by a compressible stratum, then the carrying capacity of a group piles may be very much greater than the sum of the individual pile.
     
     
     
    Design of axially loaded piles considered as columns 
    Piles embedded wholly in the ground need not be considered as long columns for the purposes of structural design. They project above the ground as in the case of jetties or piled trestles, the portion above the ground or the sea or river bed must be considered as a column and it is then necessary to consider their effective length and condition of end fixty.the codes of practise for foundation, BS CP2004 make such recommendation: 
    1. In good ground the lower point of contra-flexure can be taken as about 1.5m below the ground surface. 
    2. When the top stratum is soft clay and silt, this point may be taken as about half the depth of penetration into this stratum, but not necessary more than 3m. 
    3. Astratum of liquid mud should be treated as if it were water. 
    4. Reduction factor for working stress in piles acting as column for various ratio of effective length to least radius of gyration.
     
    DRIVEN PILE PREFORMED UNIT 
  • Materials usually in timber, concrete, or steel driven into the soil by the blows of hammer. To drive the pile to refusal in order to obtain the maximum carrying capacity from the pile. 
      TIMBER PILES (round and square) 
      1. The BS CP 2004 recommends that timber of stress grade 50 or better will be suit for piling. 
      2. In the form of trimmed tree trunk, driven butt uppermost. Lightness gives buoyancy to the foundation. 
      3. Suitable for temporary work because of it lightness, flexibility, and resistance to shock. -they are liable to decay in the zone of fluctuating water table. -case in river and marine structure. 
      4. Liable to severe attack by marine organism. 
      5. Reach difficulty in driving condition for hard soil or damage at the head should be prevent by using the heaviest practicable. 
      6. Type of timbers : Douglas fir, parana, pitch pine, larch, western red cedar, and spruce in the softwood class, and green heart, jarrah, opepe, teak, European ash, beech, and oak in the hard wood class. 
       
  •  
    PRECAST CONCRETE PILE (solid or hollow section) 
    General application of precast foundation is widely use for ware house or jetty or to carry above soil level in the form of structure columns. They also used in soil which may be unfavourable to cast in place pile, and in condition where a high resistance to lateral forces is required.
    Design parameter are normally square section, but hexagonal, octagonal, or circular pileare prefered for short and moderate lengths. They are driven hollow to save weight in handling and can be filled with concrete after dry. If the soil condition require a large cross section area, precast concrete tubes are used.
    References : # Table maximum length for various square section usually acceptable # Maximum static bending moment for a variety of condition of support in lifting and handling a pile of weight (W) and length (L) # Maximum length of square section precast concrete piles for given reinforcement
    PRESTRESSED CONCRETE PILES
    pre-stressed concrete (solid or hollow section) --required high quality concrete which is turn gives good resistance to driving stresses -the pile is stressed to prevent the development of hair cracks during handling. -these pile are made by the pre-tensioning process, the wire placed in the mould and stress by jacking the end of the wires against an abutment, after the concrete is placed and vibrated into the moulds. -pile larger than 500mm are more economical made with a hollow core. -pre-stressed concrete pile are liable to crack and spalling if they are not handle and driven carefully and should avoid high velocity impact. 
    STEEL PILE
    Characteristic-used in marine structure where their resilience and columns strength are advantageous in resist impact force from the berthing of ship. A steel suitable for marine structure where piles are subject to high impact force from ship or waves in low temperature condition is a high tensile alloy steel conforming to grade 55C or 55E of BS4360, having minimum and average Charpy V impact values of 2.4m/N and 2.0m/N, respectively when test at 0 oC working stress should be appropriate to the grade BS4360 grades 43A or 50B. recommends by CP2004, a work loads stress of 0.3 times the minimum yield strength.
    Type : *H section, usually in form of wide flange section (rolled in accordance with BS 2566) they do not cause large displacement of soil useful where upheaval of the surrounding ground would damage adjoining property or where deep penetration is required through loose or medium dense sands. *Tube piles, manufacture in seamless, spirally welded or lap welded forms. It can fabricated with thicker plates than the standard section where it is necessary to provide for high axial loads or bending moment or to provide wastage by corrosion. *Box piles, are fabricated by welding together steel plates or trough section to form hollow pile capable of carrying very high compressive, uplift or lateral loads. The area of steel considred greater than tubular piles of corresponding overall dimension. (some of the various section box pile). *Filling box and tube pile with concrete, is to drive box or tube piles a closed end to avoid splitting or enlargement at the end.
    Typical use : It used for marine structure where high lateral force due to the berthing impact of ship of ship and to wave action must be resist. Using of high tensile steel can gives economy in weight of material and hence reduced shipping and handling cost. 
    Advantage *if driven on to a hard stratum they have a high carrying capacity. *They can withstand hard driving without shattering; if the pile head buckling during hard driving it can readily be cut down and reshape for further driving. *If required they can be design to give relatively small displacement of the soil into which they driven. *They can ready be lengthened by welding or coupling on additional lengths, thus permitting deep penetration and to be achieved without the need for a tall pile frame. *They can readily cut down if not driven to their penetration and the cut off portion have value as scrap. *They can be roughly handled without damage. *They have good resistance to lateral force and buckling.
    Disadvantages : *Life time of the pile normally not so effective compare to concrete pile.*Need prevention of rust or corrosion *The tendency to bend on the weak axis during driving. Thus if pile are driven to deep penetration , a considerable curvature may result. *Low resistance to penetration of the H section pile in loose sandy soil may be a disadvantage in circumstance where high shaft friction and end bearing resistance is required at an economic depth of penetration. box piles, are fabricate together steel plates or trough steel plates or through section to form hollow piles capable of carrying very high compressieve, uplift, or lateral loads. (Properties of H-section pile)
    DRIVE AND CAST IN PLACE PILE
    Driven and cast in place piles formed by driving a tube with a closed end into the soil, and filling the tube with concrete. The tube may or may not be withdraw. jacked pile - steel or concrete unit jacked into the soil. 
    Withdrawable steel drive tube, end close by concrete plug 
    Steel shells driven by withdrawable mandrel or drive tube
    Withdrawable steel drive tube, end close by detachable plug
    Problems in driven and cast in place piles is ground heave cause by displacement of the soil by the drive tube which can cause tension failure in the shafts of adjacent piles already driven, and in the worst cases to lifting of the complete piles. It can be overcome by pitch the drive tube into bore hole drilled by mechanical auger. 
     
     
    BORED AND CAST IN PLACE PILES
    Bored and cast in place piles - piles formed by boring a hole into the soil and filling it with concrete. 

    Type of bored pile :

    Continuous bored - boring by mechanical auger machines will drill pile shaft. It must reasonable free of tree roots, cobbles and boulder and should be self support or without bentonite slurry since mechanical augers can only use in uncase hole. 

    Cable percussion drilling - applied at the site where hand and mechanical augering is impossible, such as in water bearing sand or gravel, stony or boulder clays, or very soft clays and silts, it is the usual practice to sink a hole for a small and medium diameter bored and cast in place piles by a conventional cable percussion boring rig. A problems in drilling is the risk excessive removal of soil during drilling. · augured 

    Large diameter under reamed - used for very tall building to create a large diameter piles with or without enlarged or belled out bases. The saving cost is from saving in material excavation from the pile bore hole and in concrete used to replace the excavation material. It is impossible to form under reamed at the boulder clays containing lenses of silt or sand. It also a long time to form under reamed. 

    Precast piles - there are proprietary form of bored pile in which precast concrete cylindrical units are lowered down a bore hole. They are advantages in squeezing ground containing aggressive chemicals. It can be ensure that high quality concrete is used with special cement as necessary. Also there is no ramming or vibration is employed. 

    COMPOSITE PILES
    1. combination of two or more of the preceding types or combination of different materials in the same type of pile. 
    2. are used in ground condition where conventional piles are unsuitable or uneconomical. 
    3. concrete and timber are the typical used because it is cheap and ease of handling of the timber pile with the durability of the concrete. The timber pile is terminated below ground water level and the upper portion formed in concrete. 
     
     
    Design for pile caps - pile caps must therefore be of ample dimension to allow them to accommodate piles which deviate from their intended position. The pile caps should be deep enough to ensure stability against lateral forces. Minimum pile for isolate pile group should at least 3 piles. A pile cap with 2 piles should be connected to the tie beams to adjacent caps. The heads of reinforcement concrete piles should be strip down and the projection reinforcement bonded into the pile cap to give the required bond length. In the case of slender steel piles , the depth of the piles, the depth of the pile cap required for resistance to punching shear may uneconomically large. Saving in the depth of the pile cap can be achieve by welding or reverting projection to the head of the steel pile to give increase area in bearing.
    Loads transfer devices used fro the head of Rendhex steel box pile and H-section piles.  For small pile cap and relatively large columns bases the columns loads may be partly transfer directly to the piles.  For the single columns loads on large pile group with widely spaced pile can cause shear and could be prevent by a system of link or bent up bars and top and bottom horizontal reinforcement in two layers. 
     
    Capping beams piles support a load bearing wall or close space columns may be tied together by a continuous capping beams. The pile can be staggered along the line of the beams to take care of small eccentricity of loading. 
    THE CHOICE OF TYPE OF FILE
    Having decided that piling is necessary, the engineer must make a choice from a Varity of types and sizes. It has already been noted that there is usually only one type of pile which is satisfactory for any particular site conditions. The following notes will summarise the detailed descriptions already given of the various types of pile and their particular application.
    Driven piles
    Advantages 

    Material of pile can be inspected before it goes into the ground. Stable in ‘squeezing’ ground. Not damaged by ground heave when driving adjacent piles. Construction procedure unaffected by ground water. Can be readily carried above ground level, especially in marine structure. Can be driven in very long lengths.

    Disadvantages 

    May break during hard driving causing delays and replacement charges, or worse still may suffer major unseen damage in hard driving condition. Uneconomical if amount of material in pile is governed by handling and driving stresses rather than by stresses from permanent loading. Noise and vibration during driving may cause nuisance or damage. Displacement of soil during driving piles in groups may damage adjacent structure or cause lifting by ground heave of adjacent piles. Cannot be driven in very large diameters. End enlargement not always advantages. Cannot be driven in condition of low headroom. 

     
    Advantage 

    Length can be readily adjusted to suit varying level of bearing stratum. Tube is driven with a closed end, this excluding ground water. Possible to form an enlarged base in most types. Material in pile is not determined from handling or driving stresses. Noise and vibration can be reduced in some types.

    Driven and cast-in-place piles 

    Disadvantages 

    ‘Necking’ or ‘wasting’ may occur in squeezing ground unless great care is taken when concreting shaft. Concrete shaft may be weakened if strong artesian water-flow pipes type outside of shaft. Concrete cannot be inspected after completion. Limitations on length of driving in most types. Displacement of ground may damage ‘green’ concrete of adjacent piles, or cause lifting by ground heave of adjacent piles. Noise, vibration, and ground displacement may cause a nuisance or damage adjacent structures. Cannot be used in river or marine structure without special adaptation. Cannot be driven in very large diameters. Very large end bulbs cannot be made. Cannot be driven in conditions of very low head-room. 

    Bored and cast-in- place piles
    Advantages 

    Length can be readily varied to suit varying ground conditions. Soil removed in boring can be inspected and of necessary sampled or in-situ tests made. Can be installed in very large diameters. End enlargements up to two or three diameters are possible in clays. Material of pile is not dependent on handling or driving condition. Can be installed in very long lengths. Can be installed without appreciable noise or vibration. Can be installed in conditions of very low head-room. No risk of ground heave.

    Disadvantages 

    Susceptible to ‘wasting’ or ‘necking’ in ‘squeezing’ ground.. Concrete is not placed under ideal condition and cannot be subsequently inspected. Water under artesian pressure may pipe up pile shaft washing out cement. Enlarged ends cannot be formed in cohesionless materials. Cannot be readily extended above ground level especially in river and marine structures. Boring methods may loosen sandy of gravely soil. Sinking piles may cause loss of ground in cohesionless soils, leading to settlement of adjacent structures. 

    Choice between types of pile in each category
    Driven piles 

    Timber. Suitable for light loads or temporary works. Unsuitable for heavy loads. Subject to decay due to fluctuating water table. Liable to unseen splitting or brooming if driven too heavily.

    Concrete. Suitable for all ranges of loading. Concrete can be designed to suit corrosive soil conditions. Readily adaptable to various sizes and shapes. Disadvantages: additional reinforcement must be provided for handling and driving stresses; liable to unseen damage under heavy driving; delay between casting and driving.

    Steel. Suitable for all ranges of loading. Concrete can be readily cut down or extended. Cut-off portions have scrap value and they can be used for extending other piles. Can be driven hard without damage. Can be driven in very long lengths by welding on additional lengths. Some types have small ground displacement. Structure steel bracing can be readily welded or bolted on. Resilience makes it suitable for jetty or dolphin structures. Disadvantages: subject to corrosion in marine structures and requires elaborate paint treatment and/or cathodic protection; long and slender piles liable to go off line during driving. 

    Driven and cast-in - place piles 

    The author finds it difficult for obvious reasons to make comparisons between proprietary types of piles, but in general it may be said that the types which have a withdrawable tube are cheaper than those where a steel or concrete tube or shell are left in the ground for subsequent heating with concrete. However the latter types are a sounder form of construction for ‘squeezing’ soils or water-bearing sands or where the hammer acts on the plug of concrete or shoe at the bottom of the pile are likely to cause much less noise and vibration than those in which the hammer acts on top of the tube. Generally, the recommended procedure is to approach several proprietary piling firms for quotation and let the issue be decided on the basis of costs. Reputable piling firms will not hesitate to say that their piles are unsuitable for particular ground conditions.

    Bored and cast-in-place piles

    The cheapest forms are the simple, mechanically augured piles sunk without any casing. However, they are only suitable for reasonably firm to stiff cohesive soils. The cost more than doubles when casing has to be installed and withdrawn and the slower conventional boring methods must be used.

    The enlarged base has advantages in permitting shorter piles, so bringing them within the depth range of a particular type of mechanical rig. However, enlarged bases to bored piles cannot be contemplated in sands or gravel’s.

    The use of drilling under bentonite slurry has overcome many of the problems associated with ground water and the loosening of granular soils.

    Very often head-room condition decide the type of pile.