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Chapter 1 PILE FOUNDATIONS

This document provides information about pile foundations, including: - Piles transfer structural loads through weak soil layers into stronger soils and rocks below. - Common types of piles include pre-cast concrete, cast-in-situ concrete (e.g. Raymond, MacArthur), steel, timber, and composite piles. - Piles are selected based on factors like soil properties, loading conditions, costs, and availability of materials. Proper pile type and design are necessary to safely support structures.

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Prepared by:- Miss. Khushbu k. shah Asst. prof S.S.A.S.I.T, SURAT MODULE : - 1 S.S.A.S.I.T, SURAT GTU
Contents: -Introduction -Uses of pile -Selection of type of pile -Types of pile -Pile spacing -Group of piles -Efficiency of group of pile -Pile hammer -Micro piling -Causes of failure of piles 2
A pile is a slender structural member made of steel, concrete, wood or composite material. When the depth of foundation is more then the width of foundation ,then it is termed as deep foundation. The deep foundations are classified as below: Pile foundation Cofferdams Caissons Pile foundations are used extensively for the support of buildings, bridges, and other structures to safely transfer structural loads to the ground and to avoid excess settlement or lateral movement. They are very effective in transferring structural loads through weak or compressible soil layers into the more competent soils and rocks below. 3
4 1: The load of super structure is heavy and its distribution is uneven. 2: The top soil has poor bearing capacity. 3: Subsoil water level is high so that pumping of water from the open trenches for the shallow foundation is difficult and uneconomical. 4: large fluctuation in subsoil water level. 5: structure is situated near river bed, where there is danger of scouring action of water. 6: the top soil is of expansive nature. SITUATIONS WHERE A PILE FOUNDATION IS NEEDED
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FACTORS AFFECTING THE SELECTION OF TYPE OF PILES • Nature of structure • Loading conditions • Availability of funds • Availability of materials and equipments • Types of soil and its properties • Ground water table • Self weight of pile • Durability of pile • Cost of pile • Maintenance cost • Length of pile required • Number of piles required • Facilities available for pile driving • Presence of acids and other materials in the soil that would injure the pile 7
Classification of Piles  Based on the function 1. End bearing Pile 2. Friction Pile 3. Compaction Pile 4. Tension Pile 5. Anchor Pile 6. Fender Pile 7. Batter Pile 8. Sheet Pile  Based on the material & composition 1. Concrete Pile 2. Timber Pile 3. Steel Pile 4. Composite Pile: Concrete & Timber, Concrete & Steel  Based on the method of installation 1. Driven Pile 2. Cast-in-situ Pile 3.Driven and cast- in- situ Pile 8
End bearing piles • If the piles are driven into the ground until a hard stratum is reached and the piles act as a pillars supporting the super structure and transmitting the load to the hard ground.
10 ROCK SOFT SOILPILES
Friction pile • When loose soil extended to a great depth, pile are driven up to a such a depth that frictional resistance developed at the sides of the piles equals the load coming on the piles.
13 • Compaction piles are used to compact loose granular soil, thus increasing their bearing capacity. The compaction piles themselves don’t carry load. The pile tube, driven to compact the soil, is gradually taken out and sand is filled in its place thus forming a ‘sand pile’. COMPACTION PILE
14 • Tension piles or uplift piles- Anchor down the structure subjected to uplift due to hydrostatic pressure or due to overturning moment. TENSION PILE
15 • Fender piles- Used to Protect water front structures against the impact from ships or other floating objects. • Sheet piles- Used as impervious cutoff to reduce seepage and uplift under hydraulic structures. • Batter piles- Used to resist large horizontal or inclined forces. • Anchor piles- Provide anchorage against horizontal pull from sheet piles or other pulling forces.
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CLASSIFICATION OF PILES (BASED ON MATERIAL ) Piles Concrete Pile Steel Pile Timber Pile Composite Pile Sand Pile 17
TYPES OF PILING BASED ON MATERIAL 18
CONCRETE PILE Concrete Piles Pre Cast Pile Cast-in-situ Pile Prestressed Concrete piles Cased cast-in- situ pile Un Cased cast-in- situ pile 19
1. PRE CAST CONCRETE PILE • PRE-CAST CONCRETE PILES • The precast concrete piles are generally used for maximum design load of about 80 tonnes. They must be reinforced to withstand handling stresses. • They require space for casting and storage, more time to set and curing before installation and heavy machine are required for handling purpose and driving. • These piles require heavy pile driving machinery which is mechanically operated. • The size of pile may vary from 30cm to 50cm in cross-sectional dimension, and up to 20m length or more in length. • Reinforcement may include longitudinal steel bars of 20mm to 40mm in diameter, 4 to 8 nos. with lateral tie 5 to 10mm wire spaced at 10cm c/c for top and bottom 1m length and 30cm c/c for the middle length. • A cast steel shoe, properly secured to pile by mild steel straps, is provided at its lower end. Toe protect the pile and help in penetrating into hard strata during driving. 20
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Various shape of precast pile 23
24 PROCEDURE FOR FORMING PRECAST CONCRETE PILES • The form work of required space is prepared. Usually metal forms are used for mass manufacture. The inner sides of the form is coated with either soap solution so that soil does not adhere to the side. • The reinforcement cage, as per design, is placed in the form, maintaining proper cover all around. Cast steel shoe is also placed, and is secured to the reinforcement with the help of mild steel straps. • Concrete is then placed in the form and well vibrated with the help of form vibrators. Mix of concrete 1:2:4 with maximum size of aggregate equal to 19mm. • When the pile is driven into soil it is subjected to impact stress at its head. • Remove the form after three days. But the piles are kept in same place for 7days. The piles are then shifted to curing tank where concrete is allowed to mature for at least 4weeks before being driven. • Maturing period can be reduced if, raped hardening cement is used instead of normal Portland cement.
25 ADVANTAGE OF PRECAST CONCRETE PILES: • The piles are manufactured in the factory. Hence proper control can be exercised over the composition and design of these piles. • The position of reinforcement in the pile cannot be disturbed. • Large numbers of piles are manufactured at a time in the factory or any other place, cost of manufacturing will be less. • These piles can be driven under water. If the soil water contain more sulphate. Thus pre-cast concrete piles have added advantage in such circumstance. • These piles provide highly resistant to biological and chemical action of the subsoil. DISADVANTAGE OF PRECAST CONCRETE PILES: • These piles are very heavy. • They require equipment for handling and transporting purpose. • The length of the pile is restricted since it depends upon the transport facilities. • It is very difficult to increase the length of the pile, previously estimated on the basis of bore • holes.
2.CAST-IN-SITU CONCRETE PILE Cast-in-situ Concrete Piles Uncased Simplex pile Franki Pile Vibro pile Pressure pile Pedestal pile Cased Raymond pile Mac Arthur Pile Mono tube Pile Swage piles BSP base driven pile Button bottom piles 26
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Cast-in-situ concrete piles • In this type of concrete piles, a bore is dug into the ground by inserting. This bore is then filled with cement concrete after placing reinforcement, if any.
RAYMOND PILE • (RAYMOND STANDARD CONCRETE PILE) is used primarily as a friction pipe. It is uniform heavy taper of 1in30 result in short piles for equal driving resistance or higher driving resistance for equal lengths, than piles of lesser or no taper. • Length of piles varies from 6 to 12m. diameter of piles vary from 40 to 60cm at top and 20 to 30 at bottom. • The shell is driven into the ground with a collapsible steel core in it having the same taper. • When the pile is driven to desired depth the core is mechanically collapsed and withdrawn, leaving the shell inside the ground. • Shell is inspected internally by using the flash or drop light. • Shell is gradually filled with concrete up to the top. 29
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RAYMOND PILE INSTALLATION 31
32 • This pile is of uniform diameter, best example on non-taper pile. • It used extra steel casing heavy gauge in driving pile. • Steel casing with central core is driven into ground. • After reaching the desired depth, core is withdrawn and shell is placed in casing. • After that concrete is placed in the shell, by gradually compacting it, and withdrawing steel casing. • These piles are used in place where the driving soil is very hard and it is designed to kept water tight before filling the concrete in shell. MAC-ARTHUR PILES
MAC-ARTHUR PILES shaped into a series of parallel ridges and grooves so as to give added rigidity and strength. 33
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35 BSP-BASE DRIVEN PILES • This pile consist of a helically welded shell of steel plate. A concrete plug is provided at the bottom of the shell. • Driving Is done by allowing pile hammer to fall on the concrete plug. The casing is driving to the desired depth and then it is filled with concrete.
36 SWAGE PILES • Swage piles are used with advantage in some soils where the driving is very hard or where it is desired to leave water tight shell, for some time before filling the concrete. • In the first stage a steel shell is placed on a precast concrete plug and a steel core which is not long enough to reach the plug is inserted in the plug. • In the second stage the pipe is driven over the plug until the core reaches the plug the pipe is swaged out by the taper of the plug thus forming a water tight joint. • In the third stage the pipe is driven to a specified depth. • In the fourth stage after the pipe was reached the desired depth the core is removed and the pipe is filled with concrete.
SEWAGE PILES 37
38 BUTTON BOTTOM PILES • These piles are used in locations where increase in the end bearing area is desired. The pile uses a concrete plug of shape of button. There piles have been used up to lengths of about 23 m and for loads up to 50 tonnes. • In the 1st stage a steel pipe with 12mm thick walls is set on the concrete button. The concrete button has a diameter about 25mm larger than the pipe. • In the 2nd stage the pipe and button are driven to a specified depth. • In the 3rd stage a corrugated steel shell is inserted in the pipe resting on the button. • In the 4th stage the casing is withdrawn leaving the button in place and the shell is filled with concrete. Reinforcement may be used if necessary.
BUTTON-BOTTOM PILE 39
Uncased cast in situ concrete piles • These piles are comparatively cheap, as no casing will be left in the ground. But, great skill is required in this case to achieve the desired results. • The common types of uncased cast in situ concrete piles are: 1. Simplex piles 2. Franki piles 3. Vibro piles 4. Pedestal piles 5. Pressure piles 40
41 • Simplex piles can be driven through soft or hard soils. • In this type of piles a steel tube fitted with a cast iron shoe is driven into the ground up to the desired depth. • Reinforcement if necessary is put inside the tube concrete is then poured into the tube and the tube is slowly withdrawn concrete being tamped leaving behind the cast iron shoe. SIMPLEX PILES
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43 FRANKI PILES • In this type of pile a plug of dry concrete gravel is formed on the ground by heavy removable pipe shell. A diesel operated drop hammer of 20 to 30 KN weight is driven on the concrete plug. • When the tube has reduced the desired depth the tube is held in position by cables and the hammer is applied to the concrete plug forcing it down and outward. • In the next stage the shaft is formed by introducing successive charges of concrete ramming each in turn and withdrawn the casing gradually about 300mm at a time. • The pile diameter in franki piles vary from 50cm to 60cm while the enlarged base may have a diameter of about 90cm. The pile has a load carrying capacity of 60 to 90 tonnes.
FRANKI PILE Mush-room shape Drop hammer concret e 44
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46 VIBRO PILES • These pile are used where the ground is soft thus offering little frictional resistance to the flow of concrete. Both standard and expanded piles are formed by the vibro-process. • These piles are formed by driven a steel tube and shoe filling with concrete and withdrawing the steel tube. • Standard vibro piles are made in size of 35,45,50cm diameter for loads of 60 to 70 tonnes. • A steel tube fitted with a cast iron shoe is driven in the ground by 2 to 2.5 tonnes hammer operated by steam or compressed air delivering up to 40 blow per minute with a stroke of about 1.4m.
47 PRESSURE PILES • These are formed wit the help of a casing tube boring auger and compressed air equipment. These piles are especially suitable for those congested sites where heavy vibrations and noise are not permissible. • A hole is bored into the ground by means of an auger and as the boring proceeds the hole is lined by a steel tube. • When the tube reaches the required depth the boring tool is withdrawn. In the 2nd stage a layer of concrete is laid and pressure cap is provided at the top of the tube. • The process is repeated till the pile is completed
48 PEDESTAL PILES • This type of pile are used where thin bearing stratum is reached with reasonable depth. • The core and casing are driven together into the ground till they reach the desired level. • The core is taken out and a charge of concrete is placed in the tube. • The core is again placed in the casing to rest on the of poured concrete. Pressure is applied on the concrete through the core and as the same time the casing is withdrawn. • The process is repeated till the casing is completely removed.
49 Cast-in-Place Concrete Piles Among the advantages of cast-in-place concrete piles are the following: 1. The lightweight shells may be handled and driven easily. 2. Variations in length do not present a serious problem. The length of a shell may be increased or decreased easily. 3. The shells may be slipped in short lengths and assembled at the job. 4. Excess reinforcing, to resist stresses caused by handling only, is eliminated. 5. The danger of breaking a pile while driving is eliminated. 45 6. Additional piles may be provided quickly if they are needed.
50 Cast-in-Place Concrete Piles Among the disadvantages of cast-in-place concrete piles are the following: 1. A slight movement of the earth around an un- reinforced pile may break it. 2. An uplifting force, acting on the shaft of an uncased and unreinforced pile, may cause it to fail in tension. 3. The bottom of pile may not be symmetrical.
51 •Timber piles are made of-tree trunks driven with small end as a point •They may be circular or square. • They are 30 to 50 cm in diameter with a length not exceeding 20 times its top width. • At the bottom, a cast-iron shoe is provided and the top a steel plate is fixed. •They have small bearing capacity and are not permanent unless treated. TIMBER PILE
TIMBER PILES  Advantages: • The more popular lengths and sizes are available on short notice. • They are economical in cost. • They are handled easily, with little danger of breakage. • They can be cut off to any desired length after they are driven. • They can be pulled easily in the event removal is necessary. 52
53 Disadvantages: 1. It may be difficult to obtain piles sufficiently long and straight for some projects. 2. It may be difficult or impossible to drive them into hard formations. 3. It is difficult to splice them to increase their lengths. 4. While they are satisfactory when used as friction piles, they are not suitable for use as end-bearing piles under heavy loads. 5. The length of life may be short unless the piles are treated with a preservative.
Timber pile 54
55 Steel piles are useful where driving conditions are difficult and other types of piles are not suitable. Usually used for building and bridge foundations. The piles are in form of I, H sections and steel pipe piles. They can be used for: 1. Foundation piles 2. Sheet piles 3. Superstructure columns STEEL PILE
56 • Steel I and H Piles  Steel H piles are similar to I-beam except that the cross-section is generally heavier and the flange width and beam height is nearly the same.
Steel Piles Advantages: High axial working capacity. Wide variety of sizes. Easy on- site modifications. Fairly easy to drive, minimal soil displacement, good penetration through hard materials (with shoe). Disadvantages: High cost, difficulty in delivery, relatively higher corrosion, noisy driving. 57
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• Piles of two different materials are driven one over the other, so as to enable them to act together to perform the function of a single pile. • This type of composite pile is used with the object of achieving economy in the cost of piling work. Composite Piles
Composite Piles
61 Sand piles: These piles are formed by making holes in the ground and then filling them with sand. If sand is kept confined, it possesses great crushing strength and becomes incompressible. A bore hole of required diameter, then filled with sand and it is well rammed. The top of sand pile is filled with concrete to prevent the sand ejecting upwards due to lateral pressure.
62 Classification based on method of installation  Driven piles:  These piles are driven into the ground by applying blows with a heavy hammer on their tops.  Timber, steel and precast concrete piles are installed by driving, which may be driven into position either vertically or at an inclination.  Driven and cast-in-situ piles:  These piles are formed by driving a casing with a closed bottom end into the soil.  The casing is later filled with concrete.  The casing may or may not be withdrawn, it is called uncased pile, and if not withdrawn, it is called cased pile.
63 Bored and cast-in-situ piles:  These piles are formed by excavating a hole into the ground and then filling it with concrete.  Screw piles:  These piles are screwed into soil.  Jacked piles:  These piles jacked into the ground by applying a downward force with the help of a hydraulic jack.
NON LOAD BEARING PILES 64
NON - LOAD BEARING PILES  This piles are used to function as the separating members below ground level and they are generally not designed to take any vertical load.  This piles are also known as the sheet piles. The materials used for the construction of non load bearing piles are, i. Timber sheet piles ii. Steel sheet piles iii. Concrete sheet piles 65
SHEET PILES  Sheet piles are thin piles, made of plates of concrete, timber or steel, driven into the ground for either separating members or for stopping seepage of water. They are not meant for carrying any vertical load. Therefore, sheet piles are also termed as non-load bearing piles. 66
67 SHEET PILES • Sheet piles are never used to provide vertical support but mostly used to act as retaining walls. They are used for the following purposes: o To construct retaining walls in docks, and other marine works. o To protect erosion of river banks. o To retain the sides of foundation trenches. o To confine the soil to increase its bearing capacity. o To protect the foundation of structures from erosion by river or sea. o To isolate foundations from adjacent soils.
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SHEET PILES 1.Concrete sheet piles: Concrete sheet piles are reinforced, precast units. The width of each unit may vary from 50 cm to 60 cm and thickness varies from 2 cm to 6 cm. The reinforcement is in the form of vertical bars and hoops. 70
2. Steel sheet pile: Steel sheet piles are most commonly used. They are trough shaped and when the piles are interlocked with alternate once reversed. They are generally made from steel sheets 20 to 30 cm wide and 4 to 5 m long. 71
Different types of steel sheet piles are: 1. Arch web steel sheet pile. 2. Built up steel sheet pile. 3. Z-type steel sheet pile. 4. Corrugated steel sheet pile. 5. Deep arch web steel sheet pile. 6. Universal joint steel sheet pile. 72
STEEL SHEET PILES 73
Timber sheet piles are commonly used for temporary works Such as Cofferdams. 3. Timber sheet piles: 74
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These piles are successfully developed by C.B.R.I., Roorkee (U.P.) for serving as foundations for black cotton soils, filled up ground and other types of soils having poor bearing capacity. An under reamed is a cast-in-situ concrete pile having one or more bulbs or under-reams in its lower portion. The bulbs or under-reams are formed by under reaming tool. The diameter of under reamed pile varies from 20cm to 50cm and that of bulb varies from 2 to 3 times the diameter of pile. Under reamed piles 76
METHOD OF CONSTRUCTION -The equipment for the construction of pile consists of auger boring guide, spiral auger with extension road, under-reamer with bucket and concreting funnel etc. -The auger should be rotated slowly with a constant downward pressure and taken out when it is full with soil. -The holes for casting pile in the ground may be bored by using hand augers. -For deeper borings , the length of the auger can be increased by adding suitable extension rods or pipes. -In sites where the sub soil water table is high, bentonite slurry are used to retain the sides of the bore hole against collapse. -After the pile holes are ready for concreting , the reinforcement cages are lowered in the holes and concrete is poured by the use of funnel.
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PILE SPACING • The spacing of pile is the center to center distance between two successive piles. • The factors to be considered while deciding the pile spacing are as follows: 1. The nature of soil through which the pile is driven. 2. The obstruction during pile driving 3. The type of pile 4. The depth of penetration 5. The area of cross section of the pile 6. The centre to centre distance of piles in a group 7. The manner in which the pile supports the load 8. The material of pile 82
GROUP OF PILES • Sometimes the piles are arranged in close- spaced groups. When the piles are driven to the required depth, their tops are cutoff a same level and then the pile cap is provided. • In case of single pile small pressure is developed in the surrounding soil. And in case of group piles, the pressure developed surrounding the individual piles will overlap laterally and the pressure in the overlapping zone will be sufficient 83
EFFICIENCY OF GROUP OF PILE The efficiency of a pile group is taken as the ratio of the load carrying capacity of the pile group to the sum of the load carrying capacities of the individual piles. It is determined by two methods: •converse Labbore equation. •Field rule.
86 Converse –labarre Equation: Where, n1= number of piles in row n2= number of rows D= diameter of pile d= spacing of pile Feld’s rule:- According to this rule the value of each pile is reduced by one-sixteenth on account of the effect of nearest pile in each diagonal or straight row of which the particular pile is a member.
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PILE ACCESSORIES In case of Wooden Piles, Steel Piles, Pre-cast Concrete Piles, to protect the top and bottom of the Pile while driving into the ground and to facilitate easy Pile driving certain accessories are required as under: 1. Pile Cap 2. Pile Shoe 88
PILE CAP REINFORCEMENT • In case of driven pile, piles are driven in to the ground by applying blows of a heavy hammer on their tops. Thus to protect the top of the pile cap is provided. • Pile caps carrying very heavy point loads tend to produce high tensile stresses at the pile cap. • Reinforcement is thus designed to provide: – Resistance to tensile bending forces in the bottom of the cap – Resistance to vertical shear 89
PILE SHOE • While driving wooden or steel pile by hammer the bottom end of the pile gets damaged causing difficulty in driving. • Therefore, a pile shoe is fitted at the bottom end of the pile to protect the pile and to facilitate easy pile driving. • Pile shoe are made of cast iron, steel iron. 90
Various Types of Pile Shoe 1. Square Pile Shoe 2. Wedge shape Shoe 3. Round Pile Shoe 4. Steel Trap shoe 5. Socket Type pile shoe 6.Closed end shoe for pipe pile. 91
92 PILE DRIVING
PILE DRIVING The operation of inserting a pile into the ground is known as pile driving. Piles are commonly driven by means of a hammer supported by a crane or a special device known as a Pile Driver. The various methods of pile driving are: 1. Hammer driving 2. Vibratory pile driver 3. Water jetting & hammering 4. Partial Angering method 93
94 1. Hammer driving:- For hammer driving following equipment's are used. 1. Pile frame 2. Pile hammer 3. Leads 4. Winches 5. Miscellaneous equipment's Hammers adopted for driving the pile are of the following types: 1. Drop hammer 2. Single acting hammer 3. Double acting hammer 4. Diesel hammer 5. Vibratory hammer.
95 1. Pile frame:- • Pile driver with crawler mounted crane rig commonly used for pile driving. The hammer between guided between two parallel steel channels known as leads. • Pile Driving Rigs provide basic operation of lifting the pile, holding the pile in position, hammering it into the ground or of pulling it out of the ground and guiding the pile in the desired direction of movements. • It supports the boom, the winch, mechanism, driving hammer, the guiding leaders and a platform for mounting the auxiliary equipment such as jet pumps, drilling auger etc.,
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PILE HAMMER: 1.Drop hammer: The drop hammer in the pile driving equipment consists of a heavy ram in between the leads. The ram is lifted up to a certain height and released to drop on the pile. This type is slow and therefore not in common use.
DIFFERENT TYPES OF HAMMERS USED Drop Hammer ( simple and hydraulic) 98
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2. Single acting hammer • In a single acting hammer a heavy ram is lifted up by steam or compressed air but dropped by its own weight. • The energy of a single acting hammer is equal to the weight of the ram times the 100
3. Double acting hammer: The double acting hammer employs steam or air for lifting the ram and for accelerating the downward stroke. The energy of a double acting hammer is equal to weight of ram or effective pressure of 1 times the height of fall. 101
Double Acting hammers 102
4. Diesel hammer: • The diesel hammer is a small, light weight and highly mobile. They use gasoline for fuel. To start the operation, the ram is raised, and the fuel is injected. As the ram released, the ram falls and compressed air and fuel.
104 Diesel hammer (left)
105 Leads:- • The leaders guide the pile and the hammer during operation which extents to the entire height of the rigs. • In case pile driven below the rigs in to excavations or trenches extensible leaders are used. • It enable hammer to deliver blow axially to pile.
106 Winches: • It is used to lift hammer & pile. • It should be light with single drum or double drum. It may be fitted with reverse gear system.
WATER JETTING AND HAMMERING • The use of a water or air jet to facilitate pile driving by displacing parts of the soil. • Jetting is useful in driving piles through very dense granular material. 107
108 VIBRATORY HAMMER: • Very effective in driving piles through non cohesive granular soils. • Pile is driven by making vibration. • The vibration can be produced by electrically / hydraulically. • Penetration rates can approach up to 20 m/min in moderately dense granular soils. • It can be used with another
109 PARTIAL AUGERING METHOD: • Inclined piles(batter pile) are usually advanced by partial augering. • In this technique, a power auger is used to drill the hole for a part of the depth. • The pile is then inserted in the hole & driven with hammer to the required depth.
CAUSES OF FAILURE OF PILES • Absence of statistical data regarding the nature of soil strata through which the piles are to be driven. • Actual load coming on the pile being more than the design load. • Bad workman ship in case of the cast-in-situ cement concrete piles. • Breakage due to over driving especially in case of the timber piles. • Buckling of piles due to removal of side support, inadequate lateral support, etc. 110
CAUSES OF FAILURE OF PILE • Lateral forces (wind, waves, currents etc.) not being taken into the design of the pile. • Improper choice of the type of pile. • Improper choice of the method of driving the pile. • Improper classification of pile. • Insufficient reinforcement or misplacement of reinforcement in case of the R.C.C. piles. • Wrongful use of pile formula for determining its load bearing capacity. 111
 Proposed by A.M. Wellington in the following general form; Qa= F;S+CͿ WH Where, Qa= allowable load W= wt. of the hammer H= height of the fall F= F.O.S, taken as ͞6͟ S= final set (penetration) C= empirical constant 2.5 for drop hammer,& 0.25 for single and double acting hammers. ENGINEERING NEWS FORMULA:
IS: 2911 gives the following formula based on the original expression of Hiley: 𝜼 𝒉WH 𝜼 𝒃Qd= 𝑺+𝑪/𝟐 Where, Qd= ultimate load on a pile C= toatal elastic compression C = C1+C2+C3, temporary elastic compression of dolly and packing, pile & soil respectively. 𝜼 𝒉 = efficiency of hammer 𝜼 𝒃=efficiency of hammer blow (i.e. ratio of energy after impact to striking energy of ram) HILEY’S FORMULA:
 Ultimate bearing capacity of a pile is determined by the formula given below; Qd= Rf + Rp= Asrf + Aprp Where, Rf = total ultimate skin friction Rp= total ultimate point or end bearing resistance As= surface area of pile upon which the skin friction acts Ap= area of cross section of pile on which bearing resistance acts rf = average skin friction rp= unit point or toe resistance A FOS 2.5 or 3 may be adopted for finding the allowable load. STATIC FORMULA
PILE LOAD TEST  Preliminary pile design is first carried out on the basis of site investigations, laboratory soil testing, and office study.  Pile load tests are then carried out to refine and finalize the design. For these conditions, the test piles are generally tested to failure. 115
EQUIPMENTS  Anchor Girder or Reaction Girders  Hydraulic Jack  Test Pile  Anchor Pile  Dial Gauges  Reaction Truss (in case of truss loading)
CONSTRUCTION 117
PROCEDURE: • The set-up consists of two anchor piles provided with an anchor girder or reaction girder at their top. • The test pile is installed between the anchor piles as like foundation pile is installed. The test pile should be at lest 3B or 2.5m clear from the anchor pile. • The test is conducted after a rest period of 3 days after the installation in sandy soils and period of one month in silts and soft clays. • The load is applied through a hydraulic jack resting on the reaction girder or Truss. The measurement of pile movement are taken with respect to a fixed reference mark. • The load is applied in equal increment of about 20% of the allowable load.
By Reaction Girder or Anchor Girder method
By Truss Loading Method
• Settlement should be recorded with 3 dial gauges. • Each stage of the loading is maintained till the rate of movement of the pile top is not more than 0.1mm per hour in sandy soils and 0.02mm per hour in case of clayey soils as maximum of two hours. • Under each load increment, settlements are observed at 0.5, 1, 2, 4, 8, 12, 16, 20, 60 minutes. • The loading should be continued up to twice the safe load or the load at which the total settlement reaches a specified value. • The load is removed in the same decrements at 1 hour interval & the final rebound recorded 24 hours after the entire load has been removed. • Plot a graph of Load-Settlement and make a curve for loading as well as unloading obtained from a pile load test.
123
Calculations • Figure shows a typical Load-Settlement curve for loading as well as unloading from a pile load test. • For any given load, the net pile settlement (Sn ) is given by, Sn = St- Se Where , •St = Total settlement (gross settlement) Se = Elastic settlement (rebound) Sn= net settlement
Fig.(A) Fig.(B) (2) (1)
Micro piling: • A micro pile is a small-diameter (typically less than 300 mm), drilled and grouted replacement pile that is typically (up to 20% As/Ac) reinforced. • A micro pile is constructed by drilling a borehole, placing reinforcement, and grouting the hole. Micro piles can withstand axial and/or lateral loads.
127 HISTORICAL BACKGROUND The use of micro piles has grown significantly since their conception in the 195Os, 1952 - First introduced in Italy for foundation restoration (underpinning) of WWII damaged buildings 1960’s – Widely used in Europe for underpinning old sensitive structures mid 70’s – First introduced in USA (New York &Boston) 1980’s – Being introduced in East Asia
128 CLASSIFICATIONS OF MICRO PILE 1. Based on Design Application 2. Based on Grouting method Based on Design Application CASE 1 :- micro pile elements ,which are loaded directly and where the pile reinforcement resists the majority of the applied load. CASE 2 :-micro pile elements circumscribes and internally reinforces the soil to make a reinforced soil composite that resists the applied load.
129
130
131
132
133 Based on Grouting method • The method of grouting is generally the most sensitive construction control over grout/ground bond capacity . Grout-to-grout capacity varies with the grouting method. 1) Type A: Gravity Grout 2) 2) Type B: Pressure through Casing 3) 3) Type C: Single Global Post Grout 4) 4) Type D: Multiple Repeatable Post Grout
134 Type A: Here the grout is placed under gravity head only using sand-cement motors or neat cement . Type B: 1) In this type neat cement grout is placed into the hole as the temporary steel casing is with drawn. 2) 2) Injection pressures varies from 0.5to 1.0 MPa. The pressure is limited to avoid fracturing of the surrounding ground.
135 Type C: This is done in two step process: 1) As of Type A 2) Prior to hardening of the primary grout, similar grouts injected one time via a sleeve grout pipe at pressure of at least 1.0MPa. Type D: This is done in two step process of grouting similar to Type C with modifications to step 2 where the pressure is injected at a pressure of 2.0 to 8.0MPa.
136
137
139

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Chapter 1 PILE FOUNDATIONS

  • 1.
    Prepared by:- Miss. Khushbuk. shah Asst. prof S.S.A.S.I.T, SURAT MODULE : - 1 S.S.A.S.I.T, SURAT GTU
  • 2.
    Contents: -Introduction -Uses of pile -Selectionof type of pile -Types of pile -Pile spacing -Group of piles -Efficiency of group of pile -Pile hammer -Micro piling -Causes of failure of piles 2
  • 3.
    A pile isa slender structural member made of steel, concrete, wood or composite material. When the depth of foundation is more then the width of foundation ,then it is termed as deep foundation. The deep foundations are classified as below: Pile foundation Cofferdams Caissons Pile foundations are used extensively for the support of buildings, bridges, and other structures to safely transfer structural loads to the ground and to avoid excess settlement or lateral movement. They are very effective in transferring structural loads through weak or compressible soil layers into the more competent soils and rocks below. 3
  • 4.
    4 1: The loadof super structure is heavy and its distribution is uneven. 2: The top soil has poor bearing capacity. 3: Subsoil water level is high so that pumping of water from the open trenches for the shallow foundation is difficult and uneconomical. 4: large fluctuation in subsoil water level. 5: structure is situated near river bed, where there is danger of scouring action of water. 6: the top soil is of expansive nature. SITUATIONS WHERE A PILE FOUNDATION IS NEEDED
  • 5.
  • 6.
  • 7.
    FACTORS AFFECTING THE SELECTIONOF TYPE OF PILES • Nature of structure • Loading conditions • Availability of funds • Availability of materials and equipments • Types of soil and its properties • Ground water table • Self weight of pile • Durability of pile • Cost of pile • Maintenance cost • Length of pile required • Number of piles required • Facilities available for pile driving • Presence of acids and other materials in the soil that would injure the pile 7
  • 8.
    Classification of Piles Based on the function 1. End bearing Pile 2. Friction Pile 3. Compaction Pile 4. Tension Pile 5. Anchor Pile 6. Fender Pile 7. Batter Pile 8. Sheet Pile  Based on the material & composition 1. Concrete Pile 2. Timber Pile 3. Steel Pile 4. Composite Pile: Concrete & Timber, Concrete & Steel  Based on the method of installation 1. Driven Pile 2. Cast-in-situ Pile 3.Driven and cast- in- situ Pile 8
  • 9.
    End bearing piles •If the piles are driven into the ground until a hard stratum is reached and the piles act as a pillars supporting the super structure and transmitting the load to the hard ground.
  • 10.
  • 11.
    Friction pile • Whenloose soil extended to a great depth, pile are driven up to a such a depth that frictional resistance developed at the sides of the piles equals the load coming on the piles.
  • 13.
    13 • Compaction pilesare used to compact loose granular soil, thus increasing their bearing capacity. The compaction piles themselves don’t carry load. The pile tube, driven to compact the soil, is gradually taken out and sand is filled in its place thus forming a ‘sand pile’. COMPACTION PILE
  • 14.
    14 • Tension pilesor uplift piles- Anchor down the structure subjected to uplift due to hydrostatic pressure or due to overturning moment. TENSION PILE
  • 15.
    15 • Fender piles-Used to Protect water front structures against the impact from ships or other floating objects. • Sheet piles- Used as impervious cutoff to reduce seepage and uplift under hydraulic structures. • Batter piles- Used to resist large horizontal or inclined forces. • Anchor piles- Provide anchorage against horizontal pull from sheet piles or other pulling forces.
  • 16.
  • 17.
    CLASSIFICATION OF PILES(BASED ON MATERIAL ) Piles Concrete Pile Steel Pile Timber Pile Composite Pile Sand Pile 17
  • 18.
    TYPES OF PILINGBASED ON MATERIAL 18
  • 19.
  • 20.
    1. PRE CASTCONCRETE PILE • PRE-CAST CONCRETE PILES • The precast concrete piles are generally used for maximum design load of about 80 tonnes. They must be reinforced to withstand handling stresses. • They require space for casting and storage, more time to set and curing before installation and heavy machine are required for handling purpose and driving. • These piles require heavy pile driving machinery which is mechanically operated. • The size of pile may vary from 30cm to 50cm in cross-sectional dimension, and up to 20m length or more in length. • Reinforcement may include longitudinal steel bars of 20mm to 40mm in diameter, 4 to 8 nos. with lateral tie 5 to 10mm wire spaced at 10cm c/c for top and bottom 1m length and 30cm c/c for the middle length. • A cast steel shoe, properly secured to pile by mild steel straps, is provided at its lower end. Toe protect the pile and help in penetrating into hard strata during driving. 20
  • 21.
  • 22.
  • 23.
    Various shape ofprecast pile 23
  • 24.
    24 PROCEDURE FOR FORMINGPRECAST CONCRETE PILES • The form work of required space is prepared. Usually metal forms are used for mass manufacture. The inner sides of the form is coated with either soap solution so that soil does not adhere to the side. • The reinforcement cage, as per design, is placed in the form, maintaining proper cover all around. Cast steel shoe is also placed, and is secured to the reinforcement with the help of mild steel straps. • Concrete is then placed in the form and well vibrated with the help of form vibrators. Mix of concrete 1:2:4 with maximum size of aggregate equal to 19mm. • When the pile is driven into soil it is subjected to impact stress at its head. • Remove the form after three days. But the piles are kept in same place for 7days. The piles are then shifted to curing tank where concrete is allowed to mature for at least 4weeks before being driven. • Maturing period can be reduced if, raped hardening cement is used instead of normal Portland cement.
  • 25.
    25 ADVANTAGE OF PRECASTCONCRETE PILES: • The piles are manufactured in the factory. Hence proper control can be exercised over the composition and design of these piles. • The position of reinforcement in the pile cannot be disturbed. • Large numbers of piles are manufactured at a time in the factory or any other place, cost of manufacturing will be less. • These piles can be driven under water. If the soil water contain more sulphate. Thus pre-cast concrete piles have added advantage in such circumstance. • These piles provide highly resistant to biological and chemical action of the subsoil. DISADVANTAGE OF PRECAST CONCRETE PILES: • These piles are very heavy. • They require equipment for handling and transporting purpose. • The length of the pile is restricted since it depends upon the transport facilities. • It is very difficult to increase the length of the pile, previously estimated on the basis of bore • holes.
  • 26.
    2.CAST-IN-SITU CONCRETE PILE Cast-in-situ Concrete Piles Uncased Simplex pile FrankiPile Vibro pile Pressure pile Pedestal pile Cased Raymond pile Mac Arthur Pile Mono tube Pile Swage piles BSP base driven pile Button bottom piles 26
  • 27.
  • 28.
    Cast-in-situ concrete piles •In this type of concrete piles, a bore is dug into the ground by inserting. This bore is then filled with cement concrete after placing reinforcement, if any.
  • 29.
    RAYMOND PILE • (RAYMONDSTANDARD CONCRETE PILE) is used primarily as a friction pipe. It is uniform heavy taper of 1in30 result in short piles for equal driving resistance or higher driving resistance for equal lengths, than piles of lesser or no taper. • Length of piles varies from 6 to 12m. diameter of piles vary from 40 to 60cm at top and 20 to 30 at bottom. • The shell is driven into the ground with a collapsible steel core in it having the same taper. • When the pile is driven to desired depth the core is mechanically collapsed and withdrawn, leaving the shell inside the ground. • Shell is inspected internally by using the flash or drop light. • Shell is gradually filled with concrete up to the top. 29
  • 30.
  • 31.
  • 32.
    32 • This pileis of uniform diameter, best example on non-taper pile. • It used extra steel casing heavy gauge in driving pile. • Steel casing with central core is driven into ground. • After reaching the desired depth, core is withdrawn and shell is placed in casing. • After that concrete is placed in the shell, by gradually compacting it, and withdrawing steel casing. • These piles are used in place where the driving soil is very hard and it is designed to kept water tight before filling the concrete in shell. MAC-ARTHUR PILES
  • 33.
    MAC-ARTHUR PILES shaped intoa series of parallel ridges and grooves so as to give added rigidity and strength. 33
  • 34.
  • 35.
    35 BSP-BASE DRIVEN PILES •This pile consist of a helically welded shell of steel plate. A concrete plug is provided at the bottom of the shell. • Driving Is done by allowing pile hammer to fall on the concrete plug. The casing is driving to the desired depth and then it is filled with concrete.
  • 36.
    36 SWAGE PILES • Swagepiles are used with advantage in some soils where the driving is very hard or where it is desired to leave water tight shell, for some time before filling the concrete. • In the first stage a steel shell is placed on a precast concrete plug and a steel core which is not long enough to reach the plug is inserted in the plug. • In the second stage the pipe is driven over the plug until the core reaches the plug the pipe is swaged out by the taper of the plug thus forming a water tight joint. • In the third stage the pipe is driven to a specified depth. • In the fourth stage after the pipe was reached the desired depth the core is removed and the pipe is filled with concrete.
  • 37.
  • 38.
    38 BUTTON BOTTOM PILES •These piles are used in locations where increase in the end bearing area is desired. The pile uses a concrete plug of shape of button. There piles have been used up to lengths of about 23 m and for loads up to 50 tonnes. • In the 1st stage a steel pipe with 12mm thick walls is set on the concrete button. The concrete button has a diameter about 25mm larger than the pipe. • In the 2nd stage the pipe and button are driven to a specified depth. • In the 3rd stage a corrugated steel shell is inserted in the pipe resting on the button. • In the 4th stage the casing is withdrawn leaving the button in place and the shell is filled with concrete. Reinforcement may be used if necessary.
  • 39.
  • 40.
    Uncased cast insitu concrete piles • These piles are comparatively cheap, as no casing will be left in the ground. But, great skill is required in this case to achieve the desired results. • The common types of uncased cast in situ concrete piles are: 1. Simplex piles 2. Franki piles 3. Vibro piles 4. Pedestal piles 5. Pressure piles 40
  • 41.
    41 • Simplex pilescan be driven through soft or hard soils. • In this type of piles a steel tube fitted with a cast iron shoe is driven into the ground up to the desired depth. • Reinforcement if necessary is put inside the tube concrete is then poured into the tube and the tube is slowly withdrawn concrete being tamped leaving behind the cast iron shoe. SIMPLEX PILES
  • 42.
  • 43.
    43 FRANKI PILES • Inthis type of pile a plug of dry concrete gravel is formed on the ground by heavy removable pipe shell. A diesel operated drop hammer of 20 to 30 KN weight is driven on the concrete plug. • When the tube has reduced the desired depth the tube is held in position by cables and the hammer is applied to the concrete plug forcing it down and outward. • In the next stage the shaft is formed by introducing successive charges of concrete ramming each in turn and withdrawn the casing gradually about 300mm at a time. • The pile diameter in franki piles vary from 50cm to 60cm while the enlarged base may have a diameter of about 90cm. The pile has a load carrying capacity of 60 to 90 tonnes.
  • 44.
  • 45.
  • 46.
    46 VIBRO PILES • Thesepile are used where the ground is soft thus offering little frictional resistance to the flow of concrete. Both standard and expanded piles are formed by the vibro-process. • These piles are formed by driven a steel tube and shoe filling with concrete and withdrawing the steel tube. • Standard vibro piles are made in size of 35,45,50cm diameter for loads of 60 to 70 tonnes. • A steel tube fitted with a cast iron shoe is driven in the ground by 2 to 2.5 tonnes hammer operated by steam or compressed air delivering up to 40 blow per minute with a stroke of about 1.4m.
  • 47.
    47 PRESSURE PILES • Theseare formed wit the help of a casing tube boring auger and compressed air equipment. These piles are especially suitable for those congested sites where heavy vibrations and noise are not permissible. • A hole is bored into the ground by means of an auger and as the boring proceeds the hole is lined by a steel tube. • When the tube reaches the required depth the boring tool is withdrawn. In the 2nd stage a layer of concrete is laid and pressure cap is provided at the top of the tube. • The process is repeated till the pile is completed
  • 48.
    48 PEDESTAL PILES • Thistype of pile are used where thin bearing stratum is reached with reasonable depth. • The core and casing are driven together into the ground till they reach the desired level. • The core is taken out and a charge of concrete is placed in the tube. • The core is again placed in the casing to rest on the of poured concrete. Pressure is applied on the concrete through the core and as the same time the casing is withdrawn. • The process is repeated till the casing is completely removed.
  • 49.
    49 Cast-in-Place Concrete Piles Amongthe advantages of cast-in-place concrete piles are the following: 1. The lightweight shells may be handled and driven easily. 2. Variations in length do not present a serious problem. The length of a shell may be increased or decreased easily. 3. The shells may be slipped in short lengths and assembled at the job. 4. Excess reinforcing, to resist stresses caused by handling only, is eliminated. 5. The danger of breaking a pile while driving is eliminated. 45 6. Additional piles may be provided quickly if they are needed.
  • 50.
    50 Cast-in-Place Concrete Piles Amongthe disadvantages of cast-in-place concrete piles are the following: 1. A slight movement of the earth around an un- reinforced pile may break it. 2. An uplifting force, acting on the shaft of an uncased and unreinforced pile, may cause it to fail in tension. 3. The bottom of pile may not be symmetrical.
  • 51.
    51 •Timber piles aremade of-tree trunks driven with small end as a point •They may be circular or square. • They are 30 to 50 cm in diameter with a length not exceeding 20 times its top width. • At the bottom, a cast-iron shoe is provided and the top a steel plate is fixed. •They have small bearing capacity and are not permanent unless treated. TIMBER PILE
  • 52.
    TIMBER PILES  Advantages: •The more popular lengths and sizes are available on short notice. • They are economical in cost. • They are handled easily, with little danger of breakage. • They can be cut off to any desired length after they are driven. • They can be pulled easily in the event removal is necessary. 52
  • 53.
    53 Disadvantages: 1. It maybe difficult to obtain piles sufficiently long and straight for some projects. 2. It may be difficult or impossible to drive them into hard formations. 3. It is difficult to splice them to increase their lengths. 4. While they are satisfactory when used as friction piles, they are not suitable for use as end-bearing piles under heavy loads. 5. The length of life may be short unless the piles are treated with a preservative.
  • 54.
  • 55.
    55 Steel piles areuseful where driving conditions are difficult and other types of piles are not suitable. Usually used for building and bridge foundations. The piles are in form of I, H sections and steel pipe piles. They can be used for: 1. Foundation piles 2. Sheet piles 3. Superstructure columns STEEL PILE
  • 56.
    56 • Steel Iand H Piles  Steel H piles are similar to I-beam except that the cross-section is generally heavier and the flange width and beam height is nearly the same.
  • 57.
    Steel Piles Advantages: High axialworking capacity. Wide variety of sizes. Easy on- site modifications. Fairly easy to drive, minimal soil displacement, good penetration through hard materials (with shoe). Disadvantages: High cost, difficulty in delivery, relatively higher corrosion, noisy driving. 57
  • 58.
  • 59.
    • Piles oftwo different materials are driven one over the other, so as to enable them to act together to perform the function of a single pile. • This type of composite pile is used with the object of achieving economy in the cost of piling work. Composite Piles
  • 60.
  • 61.
    61 Sand piles: These pilesare formed by making holes in the ground and then filling them with sand. If sand is kept confined, it possesses great crushing strength and becomes incompressible. A bore hole of required diameter, then filled with sand and it is well rammed. The top of sand pile is filled with concrete to prevent the sand ejecting upwards due to lateral pressure.
  • 62.
    62 Classification based onmethod of installation  Driven piles:  These piles are driven into the ground by applying blows with a heavy hammer on their tops.  Timber, steel and precast concrete piles are installed by driving, which may be driven into position either vertically or at an inclination.  Driven and cast-in-situ piles:  These piles are formed by driving a casing with a closed bottom end into the soil.  The casing is later filled with concrete.  The casing may or may not be withdrawn, it is called uncased pile, and if not withdrawn, it is called cased pile.
  • 63.
    63 Bored and cast-in-situpiles:  These piles are formed by excavating a hole into the ground and then filling it with concrete.  Screw piles:  These piles are screwed into soil.  Jacked piles:  These piles jacked into the ground by applying a downward force with the help of a hydraulic jack.
  • 64.
  • 65.
    NON - LOADBEARING PILES  This piles are used to function as the separating members below ground level and they are generally not designed to take any vertical load.  This piles are also known as the sheet piles. The materials used for the construction of non load bearing piles are, i. Timber sheet piles ii. Steel sheet piles iii. Concrete sheet piles 65
  • 66.
    SHEET PILES  Sheetpiles are thin piles, made of plates of concrete, timber or steel, driven into the ground for either separating members or for stopping seepage of water. They are not meant for carrying any vertical load. Therefore, sheet piles are also termed as non-load bearing piles. 66
  • 67.
    67 SHEET PILES • Sheetpiles are never used to provide vertical support but mostly used to act as retaining walls. They are used for the following purposes: o To construct retaining walls in docks, and other marine works. o To protect erosion of river banks. o To retain the sides of foundation trenches. o To confine the soil to increase its bearing capacity. o To protect the foundation of structures from erosion by river or sea. o To isolate foundations from adjacent soils.
  • 68.
  • 69.
  • 70.
    SHEET PILES 1.Concrete sheet piles: Concretesheet piles are reinforced, precast units. The width of each unit may vary from 50 cm to 60 cm and thickness varies from 2 cm to 6 cm. The reinforcement is in the form of vertical bars and hoops. 70
  • 71.
    2. Steel sheetpile: Steel sheet piles are most commonly used. They are trough shaped and when the piles are interlocked with alternate once reversed. They are generally made from steel sheets 20 to 30 cm wide and 4 to 5 m long. 71
  • 72.
    Different types ofsteel sheet piles are: 1. Arch web steel sheet pile. 2. Built up steel sheet pile. 3. Z-type steel sheet pile. 4. Corrugated steel sheet pile. 5. Deep arch web steel sheet pile. 6. Universal joint steel sheet pile. 72
  • 73.
  • 74.
    Timber sheet pilesare commonly used for temporary works Such as Cofferdams. 3. Timber sheet piles: 74
  • 75.
  • 76.
    These piles aresuccessfully developed by C.B.R.I., Roorkee (U.P.) for serving as foundations for black cotton soils, filled up ground and other types of soils having poor bearing capacity. An under reamed is a cast-in-situ concrete pile having one or more bulbs or under-reams in its lower portion. The bulbs or under-reams are formed by under reaming tool. The diameter of under reamed pile varies from 20cm to 50cm and that of bulb varies from 2 to 3 times the diameter of pile. Under reamed piles 76
  • 78.
    METHOD OF CONSTRUCTION -Theequipment for the construction of pile consists of auger boring guide, spiral auger with extension road, under-reamer with bucket and concreting funnel etc. -The auger should be rotated slowly with a constant downward pressure and taken out when it is full with soil. -The holes for casting pile in the ground may be bored by using hand augers. -For deeper borings , the length of the auger can be increased by adding suitable extension rods or pipes. -In sites where the sub soil water table is high, bentonite slurry are used to retain the sides of the bore hole against collapse. -After the pile holes are ready for concreting , the reinforcement cages are lowered in the holes and concrete is poured by the use of funnel.
  • 79.
  • 80.
  • 81.
  • 82.
    PILE SPACING • Thespacing of pile is the center to center distance between two successive piles. • The factors to be considered while deciding the pile spacing are as follows: 1. The nature of soil through which the pile is driven. 2. The obstruction during pile driving 3. The type of pile 4. The depth of penetration 5. The area of cross section of the pile 6. The centre to centre distance of piles in a group 7. The manner in which the pile supports the load 8. The material of pile 82
  • 83.
    GROUP OF PILES •Sometimes the piles are arranged in close- spaced groups. When the piles are driven to the required depth, their tops are cutoff a same level and then the pile cap is provided. • In case of single pile small pressure is developed in the surrounding soil. And in case of group piles, the pressure developed surrounding the individual piles will overlap laterally and the pressure in the overlapping zone will be sufficient 83
  • 85.
    EFFICIENCY OF GROUPOF PILE The efficiency of a pile group is taken as the ratio of the load carrying capacity of the pile group to the sum of the load carrying capacities of the individual piles. It is determined by two methods: •converse Labbore equation. •Field rule.
  • 86.
    86 Converse –labarre Equation: Where, n1=number of piles in row n2= number of rows D= diameter of pile d= spacing of pile Feld’s rule:- According to this rule the value of each pile is reduced by one-sixteenth on account of the effect of nearest pile in each diagonal or straight row of which the particular pile is a member.
  • 87.
  • 88.
    PILE ACCESSORIES In caseof Wooden Piles, Steel Piles, Pre-cast Concrete Piles, to protect the top and bottom of the Pile while driving into the ground and to facilitate easy Pile driving certain accessories are required as under: 1. Pile Cap 2. Pile Shoe 88
  • 89.
    PILE CAP REINFORCEMENT •In case of driven pile, piles are driven in to the ground by applying blows of a heavy hammer on their tops. Thus to protect the top of the pile cap is provided. • Pile caps carrying very heavy point loads tend to produce high tensile stresses at the pile cap. • Reinforcement is thus designed to provide: – Resistance to tensile bending forces in the bottom of the cap – Resistance to vertical shear 89
  • 90.
    PILE SHOE • Whiledriving wooden or steel pile by hammer the bottom end of the pile gets damaged causing difficulty in driving. • Therefore, a pile shoe is fitted at the bottom end of the pile to protect the pile and to facilitate easy pile driving. • Pile shoe are made of cast iron, steel iron. 90
  • 91.
    Various Types ofPile Shoe 1. Square Pile Shoe 2. Wedge shape Shoe 3. Round Pile Shoe 4. Steel Trap shoe 5. Socket Type pile shoe 6.Closed end shoe for pipe pile. 91
  • 92.
  • 93.
    PILE DRIVING The operationof inserting a pile into the ground is known as pile driving. Piles are commonly driven by means of a hammer supported by a crane or a special device known as a Pile Driver. The various methods of pile driving are: 1. Hammer driving 2. Vibratory pile driver 3. Water jetting & hammering 4. Partial Angering method 93
  • 94.
    94 1. Hammer driving:-For hammer driving following equipment's are used. 1. Pile frame 2. Pile hammer 3. Leads 4. Winches 5. Miscellaneous equipment's Hammers adopted for driving the pile are of the following types: 1. Drop hammer 2. Single acting hammer 3. Double acting hammer 4. Diesel hammer 5. Vibratory hammer.
  • 95.
    95 1. Pile frame:- •Pile driver with crawler mounted crane rig commonly used for pile driving. The hammer between guided between two parallel steel channels known as leads. • Pile Driving Rigs provide basic operation of lifting the pile, holding the pile in position, hammering it into the ground or of pulling it out of the ground and guiding the pile in the desired direction of movements. • It supports the boom, the winch, mechanism, driving hammer, the guiding leaders and a platform for mounting the auxiliary equipment such as jet pumps, drilling auger etc.,
  • 96.
  • 97.
    PILE HAMMER: 1.Drop hammer: Thedrop hammer in the pile driving equipment consists of a heavy ram in between the leads. The ram is lifted up to a certain height and released to drop on the pile. This type is slow and therefore not in common use.
  • 98.
    DIFFERENT TYPES OF HAMMERSUSED Drop Hammer ( simple and hydraulic) 98
  • 99.
  • 100.
    2. Single acting hammer •In a single acting hammer a heavy ram is lifted up by steam or compressed air but dropped by its own weight. • The energy of a single acting hammer is equal to the weight of the ram times the 100
  • 101.
    3. Double actinghammer: The double acting hammer employs steam or air for lifting the ram and for accelerating the downward stroke. The energy of a double acting hammer is equal to weight of ram or effective pressure of 1 times the height of fall. 101
  • 102.
  • 103.
    4. Diesel hammer: •The diesel hammer is a small, light weight and highly mobile. They use gasoline for fuel. To start the operation, the ram is raised, and the fuel is injected. As the ram released, the ram falls and compressed air and fuel.
  • 104.
  • 105.
    105 Leads:- • The leadersguide the pile and the hammer during operation which extents to the entire height of the rigs. • In case pile driven below the rigs in to excavations or trenches extensible leaders are used. • It enable hammer to deliver blow axially to pile.
  • 106.
    106 Winches: • It isused to lift hammer & pile. • It should be light with single drum or double drum. It may be fitted with reverse gear system.
  • 107.
    WATER JETTING ANDHAMMERING • The use of a water or air jet to facilitate pile driving by displacing parts of the soil. • Jetting is useful in driving piles through very dense granular material. 107
  • 108.
    108 VIBRATORY HAMMER: • Veryeffective in driving piles through non cohesive granular soils. • Pile is driven by making vibration. • The vibration can be produced by electrically / hydraulically. • Penetration rates can approach up to 20 m/min in moderately dense granular soils. • It can be used with another
  • 109.
    109 PARTIAL AUGERING METHOD: •Inclined piles(batter pile) are usually advanced by partial augering. • In this technique, a power auger is used to drill the hole for a part of the depth. • The pile is then inserted in the hole & driven with hammer to the required depth.
  • 110.
    CAUSES OF FAILUREOF PILES • Absence of statistical data regarding the nature of soil strata through which the piles are to be driven. • Actual load coming on the pile being more than the design load. • Bad workman ship in case of the cast-in-situ cement concrete piles. • Breakage due to over driving especially in case of the timber piles. • Buckling of piles due to removal of side support, inadequate lateral support, etc. 110
  • 111.
    CAUSES OF FAILUREOF PILE • Lateral forces (wind, waves, currents etc.) not being taken into the design of the pile. • Improper choice of the type of pile. • Improper choice of the method of driving the pile. • Improper classification of pile. • Insufficient reinforcement or misplacement of reinforcement in case of the R.C.C. piles. • Wrongful use of pile formula for determining its load bearing capacity. 111
  • 112.
     Proposed byA.M. Wellington in the following general form; Qa= F;S+CͿ WH Where, Qa= allowable load W= wt. of the hammer H= height of the fall F= F.O.S, taken as ͞6͟ S= final set (penetration) C= empirical constant 2.5 for drop hammer,& 0.25 for single and double acting hammers. ENGINEERING NEWS FORMULA:
  • 113.
    IS: 2911 givesthe following formula based on the original expression of Hiley: 𝜼 𝒉WH 𝜼 𝒃Qd= 𝑺+𝑪/𝟐 Where, Qd= ultimate load on a pile C= toatal elastic compression C = C1+C2+C3, temporary elastic compression of dolly and packing, pile & soil respectively. 𝜼 𝒉 = efficiency of hammer 𝜼 𝒃=efficiency of hammer blow (i.e. ratio of energy after impact to striking energy of ram) HILEY’S FORMULA:
  • 114.
     Ultimate bearingcapacity of a pile is determined by the formula given below; Qd= Rf + Rp= Asrf + Aprp Where, Rf = total ultimate skin friction Rp= total ultimate point or end bearing resistance As= surface area of pile upon which the skin friction acts Ap= area of cross section of pile on which bearing resistance acts rf = average skin friction rp= unit point or toe resistance A FOS 2.5 or 3 may be adopted for finding the allowable load. STATIC FORMULA
  • 115.
    PILE LOAD TEST Preliminary pile design is first carried out on the basis of site investigations, laboratory soil testing, and office study.  Pile load tests are then carried out to refine and finalize the design. For these conditions, the test piles are generally tested to failure. 115
  • 116.
    EQUIPMENTS  Anchor Girderor Reaction Girders  Hydraulic Jack  Test Pile  Anchor Pile  Dial Gauges  Reaction Truss (in case of truss loading)
  • 117.
  • 118.
    PROCEDURE: • The set-upconsists of two anchor piles provided with an anchor girder or reaction girder at their top. • The test pile is installed between the anchor piles as like foundation pile is installed. The test pile should be at lest 3B or 2.5m clear from the anchor pile. • The test is conducted after a rest period of 3 days after the installation in sandy soils and period of one month in silts and soft clays. • The load is applied through a hydraulic jack resting on the reaction girder or Truss. The measurement of pile movement are taken with respect to a fixed reference mark. • The load is applied in equal increment of about 20% of the allowable load.
  • 119.
    By Reaction Girderor Anchor Girder method
  • 120.
  • 122.
    • Settlement shouldbe recorded with 3 dial gauges. • Each stage of the loading is maintained till the rate of movement of the pile top is not more than 0.1mm per hour in sandy soils and 0.02mm per hour in case of clayey soils as maximum of two hours. • Under each load increment, settlements are observed at 0.5, 1, 2, 4, 8, 12, 16, 20, 60 minutes. • The loading should be continued up to twice the safe load or the load at which the total settlement reaches a specified value. • The load is removed in the same decrements at 1 hour interval & the final rebound recorded 24 hours after the entire load has been removed. • Plot a graph of Load-Settlement and make a curve for loading as well as unloading obtained from a pile load test.
  • 123.
  • 124.
    Calculations • Figure showsa typical Load-Settlement curve for loading as well as unloading from a pile load test. • For any given load, the net pile settlement (Sn ) is given by, Sn = St- Se Where , •St = Total settlement (gross settlement) Se = Elastic settlement (rebound) Sn= net settlement
  • 125.
  • 126.
    Micro piling: • Amicro pile is a small-diameter (typically less than 300 mm), drilled and grouted replacement pile that is typically (up to 20% As/Ac) reinforced. • A micro pile is constructed by drilling a borehole, placing reinforcement, and grouting the hole. Micro piles can withstand axial and/or lateral loads.
  • 127.
    127 HISTORICAL BACKGROUND The useof micro piles has grown significantly since their conception in the 195Os, 1952 - First introduced in Italy for foundation restoration (underpinning) of WWII damaged buildings 1960’s – Widely used in Europe for underpinning old sensitive structures mid 70’s – First introduced in USA (New York &Boston) 1980’s – Being introduced in East Asia
  • 128.
    128 CLASSIFICATIONS OF MICROPILE 1. Based on Design Application 2. Based on Grouting method Based on Design Application CASE 1 :- micro pile elements ,which are loaded directly and where the pile reinforcement resists the majority of the applied load. CASE 2 :-micro pile elements circumscribes and internally reinforces the soil to make a reinforced soil composite that resists the applied load.
  • 129.
  • 130.
  • 131.
  • 132.
  • 133.
    133 Based on Groutingmethod • The method of grouting is generally the most sensitive construction control over grout/ground bond capacity . Grout-to-grout capacity varies with the grouting method. 1) Type A: Gravity Grout 2) 2) Type B: Pressure through Casing 3) 3) Type C: Single Global Post Grout 4) 4) Type D: Multiple Repeatable Post Grout
  • 134.
    134 Type A: Herethe grout is placed under gravity head only using sand-cement motors or neat cement . Type B: 1) In this type neat cement grout is placed into the hole as the temporary steel casing is with drawn. 2) 2) Injection pressures varies from 0.5to 1.0 MPa. The pressure is limited to avoid fracturing of the surrounding ground.
  • 135.
    135 Type C: Thisis done in two step process: 1) As of Type A 2) Prior to hardening of the primary grout, similar grouts injected one time via a sleeve grout pipe at pressure of at least 1.0MPa. Type D: This is done in two step process of grouting similar to Type C with modifications to step 2 where the pressure is injected at a pressure of 2.0 to 8.0MPa.
  • 136.
  • 137.
  • 139.