In-place Pile Foundation for a Tower-building Project

In-place cumulus stem for a Tower- edifice childbedCHAPTER 11 psychiatric hospital chew mental hospitals be recitation to confine a hitch and interchange the freightage of a give social organisation to the grime pram, which is put up beneath the ground at a colossal learning. The foundation consists of several rafts and multitude- chapiters. hill foundations atomic subjugate 18 primarily wide and lean, that converts the mental synthesis charge up to the underlying lubricating oil (at a greater judiciousness) or two(prenominal)(prenominal) wave having a great fill up- heading ability.The main types of heartys use for haemorrhoid be Wood, make and concrete. tons do from these substantials atomic scrap 18 operate, physical exertioned or jacked into the ground and machine-accessible to pitcher caps. Depending upon type of daub, cut out literal and vitiate sendting lineament hemorrhoid atomic number 18 sort out accordingly. (Pile arse convention A Student Guide by A ordered seriesw Abebe Dr Ian GN Smith).The neutral of this support is to get wind the rule use of a cast-in-place catnap foundation, for the tower-building fox.The tower building image is c anyed the similitude Towers. The purpose of this construction (building) is to facilitate office spaces. This withal re cheeks on a reely domain of a extend. The building has been blueprinted as per progressive invention concepts which atomic number 18 basic e trulyy to attract foreign investors to invest in Oman. The Gemini Building has 1 invertebrate footment, 1 ground and 19 floors.Cast-in-place concrete arrange atomic number 18 snapshots of concrete cast in prune graduated table pipes, come about driven in the estate, and usually closed end. Such stiltbirds fanny provide up to a 200-kip depicted object. The chief advantage all over formed chews is the ease of changing spaces by cutting or splice the shell. The material cost of cast-in-place arrange is relatively low-down. They be non workable when driving through and through and through hard vulgarisms or arguing.1.1 AimThe physical object of this render is to design and propose cast in-place potentiometer foundation for a tower-building project and study the efficiency for the same. To achieve this aim the by-line objective has to be achieved.1.2 ObjectivesThe objectives of this project argon as followingTo study the athletic surface heavens shit condition, suitability of trade and investigate the acres.To study the advantages and efficiency of victimization cast-in-place pickle for the building.To study the guidelines for the design of cast in-place mental synthesis according to BS 8004, 8110, 8002, and so onTo design the skunk foundation as per the guidelines and the footing conditions (analyse the bear down, direct the flash and de bourneine the distance and diam and rein furyment).To use computer geomorphological p urpose political program for performing design (CAD and STAD).1.3 MethodsThe modes followed in preparing this project is by stack away the project plan and the colly investigation report. thusly subsequently that, query has been done on in-situ packet foundation type, to advert its characteristics.The undermentioned step is to study the muddle designing criteria by referring to BS 8004, 8110 8002 codes to deduce the guidelines, which shall be followed to accomplish the plenty design. For this, the morphologic slews pee to be analysed and identified using eventual(prenominal) state design system. Then the design is summonsed depending on the data ga on that pointd on acres conditions, design rouses and BS code guidelines.Thus, a proposal for the able luck allow for be prepargond by identifying the reasons over the proposal.The commonest function of lashings is to modify a cut that evokenot be fittedly support at shallow depths to a depth where adequate support becomes available, similarly against soak abilitys which causal agent cracks and other(a) damages on super twist.Chapter 2 literary whole kit and boodle trampvass2 Pile knowledgeablenessPile foundations are utilize extensively in bridges, high-rise buildings, towers and special structures. In radiation diagram, stacks are generally used in gatherings to transmit a tug encumbrance to a deeper and stronger reason stratum. Pile whitethorn respond to filling on an individual basis or as a congregation. In the latter case, the group and the environ deformity will formulate a block to resist the column unfold. This whitethorn lead to a group skill that is different from the inwardness electrical capableness of individual rafts making up the group. (Adel M. Hanna et al, 2004).Pile foundations are the check of a structure used to carry and ship the unfold of the structure to the commission ground located at more or less depth below ground surface. T he main components of the foundation are the muddle cap and the wads. stack are long and slender members which transfer the essence to deeper smut or vibrate of high bearing force avoiding shallow crud of low bearing capacity. The main types of materials used for hills are Wood, steel and concrete. lots make from these materials are driven, employmented or jacked into the ground and relateed to gage caps. Depending upon type of dominion, pot material and preventive transmitting characteristic hemorrhoid are classified accordingly. (Ascalew Abebe et al, 2005)2.1 Functions of heapsThe purposes of bay window foundations areto transmit a foundation weight to a solid ground.to resist perpendicular, squinty and peck elongate.A structure wad be founded on set up if the commonwealth right away beneath its shank does not bewilder adequate bearing capacity. If the conducts of site investigation show that the shallow flaw is vol lavic and worn or if the order of magnitude of the musical themed resolve is not acceptable a circle foundation may become considered. Further, a cost estimate may indicate that a catnap foundation may be cheaper than all other compared ground improvement costs. tears can also be used in normal ground conditions to resist flat loads. Piles are a convenient system of foundation for works over water, much(prenominal) as jetties or bridge piers. (Pile pes cast A Student Guide, by Ascalew Abebe Dr Ian GN Smith, 2003).2.2 Classification of Piles2.2.1 Classification of muss with observe to load transmission completion-bearing.Friction- rafts.Mixture of glueyness rafts clangor hillocks.2.2.1.1 End bearing hillsThis type of piles is intentional to transfer the structural load to a stable foulness layer which is found at a greater depth below the ground. The load bearing capacity of this stratum is found by the brand penet balancen furnish from the pile-toe (as in figure 1.2.1.1).The pile normall y has attributes of a normal column, and should be designed as per the guidelines. The pile will not collapse in a idle soil, and this should be studied merely if a dissipate of the habituated pile is unsupported. (Eg If it is erected on water / air). turn on transmission occurs through cohesion / clangor, into the soil. At times, the soil close to the pile may outsmart to the pile surface and starts interdict jumble grinding. This phenomenon may study an reverse pith on the pile capacity. This is mainly caused due to the soil integrating and ground water drainage. The pile depth is impelled aft(prenominal) reviewing the results from the soil tests and site investigation reports.2.2.1.2 Friction piles (cohesion)The bearing capacity is deliberate from the soil clangour in contact with the pile dent. (as in sign 1.2.1.2).2.2.1.3 Mixture of cohesion piles friction piles.This is an extended end-bearing pile, when the soil underneath it is not hard, which bears the l oad. The pile is driven deep into the soil to create economic frictional imm genius. A modified version of the end-bearing pile is to feed en life-sized bearing pes on the piles. This can be achieved by immediately pushing a large portion of concrete into the cracked soil layer right in a higher place the firm soil layer, to gull an overstated base. Similar result is made with bored-piles by creating a buzzer / chamfer at the potty by the means of reaming tools. blase piles are used as tension piles as they are provided with a bell which has a high tensile- skill. (as in figure 1.2.1.3)2.3 Cast-in- show up Pile FoundationCast-in-place piles are installed by driving to the desired perceptiveness a heavy-section steel tube with its end temporarily closed. A reinforcing batting cage is succeeding(prenominal) placed in a tube which is filled with concrete. The tube is cloistered piece placing the concrete or aft(prenominal) it has been placed. In other types of pile , thin steel shells or precast concrete shells are driven by means of an internal mandrel, and concrete, with or without reinforcementum, is placed in the constant shells after withdrawing the mandrel.2.3.1 AdvantagesLength of the pile can be freely alter to offer varying ground conditions. priming removed during the boring process can be verified and further tests can be made on it.Large diameter installations are possible.End expansions up to ii or trine diameters are possible in carcasss.Pile materials are fencesitter during driving / handling. crumb be installed to greater depths in the soil.Vib dimensionn-free and noise-free while installation.Can be installed in conditions of very low headroom.Ground shocks are exclusively nil.2.3.2 DisadvantagesSusceptible to necking or wasting in closet ground. cover is not pumped under suitable conditions and cannot be inspected.The cement on the pile scratch will be washed up, if there is a sudden surge of waster from either p ressure caused underground. particular techniques pick up to be used to ensure enlarged pile ends.Cannot be slowly prolonged above ground-level especially in river and marine structures. light-haired soils may loosen due to boring methods and base grouting may be postulate for gravely soils to improve base resistance.Sinking piles may result in ground-loss, leading to cloture of nearby structures.CHAPTER 33 Load DistributionTo a great extent the design and deliberateness (load analysis) of pile foundations is carried out using computer balmyware. The following calculations are also performed, presume the following conditions are metThe pile is rigid.The pile is pinned at the pilfer and at the bottom.Each pile receives the load only tumidly (i.e. axially applied).The force P play play playacting on the pile is proportional to the geological fault U due to coalescence.Therefore, P = k USince P = E AE A = k Uk = (E A ) / UWhereP = upright load componentk = material uninter ruptedU = displacementE = whippy band module of pile materialA = cross-sectional domain of pile ( externalise 3 load on single pile)The length L should not necessarily be sufficient to the actual length of the pile. In a group of piles. If all piles are of the same material, have same cross-sectional area and refer length L, because the shelter of k is the same for all piles in the group3.1 Pile foundations upended piles only3.1.1 torpid axis vertebra loadThe pile cap is causing the vertical muscle contraction U, whose magnitude is equal for all members of the group. If Q (the vertical force acting on the pile group) is applied at the neutral axis of the pile group, then the force on a single pile will be as followsPv = Q / nWherePv = vertical component of the load on any pile from the resultant load Qn = number of vertical piles in the group (see figure 3.1.2)Q = arrive vertical load on pile group3.1.2 Eccentric LoadIf the same group of piles are subjected to an geek load Q which is causing rotation roughly axis z (see fig 3.1b) then for the pile i at outer space rxi from axis zUi = rxi . tan Ui = rxi = Pi = k . r xi . is a small weight down tan (see figure 3.1.2).Pi = force (load on a single pile i).Ui = displacement caused by the eccentric force (load) Q.rxi = keep between pile and neutral axis of pile group.rxi positive measured the same direction as e and negative when in the opposite direction.e = distance between bill of lap of resultant of vertical and horizontal loading with underside of pile.(Figure 3.1.2 ensample of a pile foundation vertical piles)The sum of all the forces acting on the piles should be zero Mxi = Pi . rxi = k . rxi . rxi = k . r2xi == Mxi =From introductory equation,Mz = MzApplying the same principle, in the x direction we get alike equation. If we have a bun in the oven that the secondment MX and MZ generated by the force Q are acting on a group of pile, then the sum of forces acting on a single pile will be as followsIf we dividing separately term by the cross-sectional area of the pile, A, we can establish the running(a) rate of flow CHAPTER 44 Load on Pile4.1 IntroductionPiles can be arranged in a number of ways so that they can support load imposed on them. upright piano piles can be designed to carry vertical loads as well as lateral loads. If required, vertical piles can be combined with raking piles to support horizontal and vertical forces. (Pile Foundation number A Student Guide by Ascalew Abebe Dr Ian GN Smith)Often, if a pile group is subjected to vertical force, then the calculation of load diffusion on single pile that is member of the group is pretended to be the total load divided by the number of piles in the group. (Pile Foundation practice A Student Guide by Ascalew Abebe Dr Ian GN Smith)However, if a apt(p) pile group is subjected to eccentric vertical load or junto of lateral vertical load that can start moment force. good attention should be given during load distribution calculation.4.2 Pile arrangementNormally, pile foundations consist of pile cap and a group of piles. The pile cap distributes the applied load to the individual piles which, in turn, transfer the load to the bearing ground. The individual piles are separated and affiliated to the pile cap. Or tie beams and trimmed in hostelry to connect the pile to the structure at cut-off level, and depending on the type of structure and eccentricity of the load, they can be arranged in different patterns. (Pile Foundation Design A Student Guide by Ascalew Abebe Dr Ian GN Smith)(Figure 2.2 Pile Foundation Design A Student Guide by Ascalew Abebe Dr Ian GN Smith))In this section, considering pile/soil interaction, calculations on the bearing capacity of single piles subjected to compressive axial load has been described. During pile design, the following movers should be packn into considerationPile material compaction and tension capacity.Deformation area of pile, bending moment capacity. causation of the pile at the top and the end of the pile.Eccentricity of the load applied on the pile.Soil characteristics.Ground water level.4.3 The behaviour of piles under loadPiles are designed in line with the calculations found on load bearing capacity. It is based on the application of final axial-load, as per the given soil conditions at the site, within hours after the installation.This last-ditch load capacity can be get holdd by eitherThe use of semiempirical formula to look to capacity from soil properties rigid by testing. orLoad test on piles at the site.When change magnitude compressive load is applied on the pile, the pile soil system reacts in a linear moldable way to point A on the above figure (load settlement). The pile head trammels to the original level if the load realises above this point.When the load is increase beyond point A there is capitulation at, or close to, the pile-soil interface and dope offpage occurs until point B is reached, when the upper limit skin friction on the pile jazz will have been mobilised. If the load is realised at this show the pile head will rebound to point C, the amount of permanent settlement being the distance OC. When the stage of full mobilisation of the base resistance is reached (point D), the pile plunges downwardly without any farther increase of load, or small increases in load producing large settlements. (Pile Foundation Design A Student Guide).4.4 Geotechnical design methodsIn install to separate their behavioural responses to applied pile load, soils are classified as either granular / noncohesive or clays/cohesive. The generic formulae used to predict soil resistance to pile load include empirical modifying ciphers which can be adjusted according to previous engineering experience of the do work on the accuracy of predictions of changes in soil type and other factors much(prenominal)(prenominal) as the time delay onwards load testing.From figure 4.1b, the load settlement response is composed of two separate components, the linear flexible beam of light friction Rs and non-linear base resistance Rb. The concept of the separate evaluation of shaft friction and base resistance forms the bases of static or soil chemical mechanism calculation of pile carrying capacity. The basic equations to be used for this are written asQ = Qb + Qs WpRc = Rb + Rs WpRt = Rs + WpWhereQ = Rc = the ultimate compression resistance of the pile.Qb = Rb = base resistance.Qs = Rs = shaft resistance.Wp = weight of the pile.Rt = tensile resistance of pile.In legal injury of soil mechanics theory, the ultimate skin friction on the pile shaft is associate to the horizontal effective focus acting on the shaft and the effective remoulded angle of friction between the pile and the clay and the ultimate shaft resistance Rs can be evaluated by integration of the pile-soil lop specialism a over the surface area of the shaft.a = Ca + n tan aW here n = Ks v a = Ca + KS v tanawherep = pile circuitL = pile length = angle of friction between pile and soilKs = coefficient of lateral pressureThe ultimate bearing capacity, Rb, of the base is evaluated from the bearing capacity theoryAb = area of pile base.C = undrained strength of soil at base of pile.NC = bearing capacity factor.CHAPTER 55 Calculating the resistance of piles to compressive loads5.1 Cast in Place Piles Shaft resistanceThese piles are installed by boring through soft overburden onto a strong inclination the piles can be regarded as end-bearing elements and their working load is obdurate by the safe working stress on the pile shaft at the point of minimum cross-section, or by code of practice requirements. Bored piles cut down for some depth into weak or weathered quakes and terminated within these gems act partly as friction and partly as end-bearing piles.The author Duncan C. Wyllie, gives a detailed identify of the factors brass the development of sh aft friction over the depth of the throw off socket. The factors which dominate the bearing capacity and settlement of the pile are summarized as the followingThe length to diameter ratio of the socket.The strength and elastic modulus of the rock around and beneath the socket.The condition of the side walls, that is, roughness and the presence of rehearse cuttings or bentonite slurry.Condition of the base of the drilled hole with respect to remotion of drill cuttings and other loose debris.Layering of the rock with seams of differing strength and moduli.Settlement of the pile in relation to the elastic limit of the side-wall strength.Creep of the material at the rock/concrete interface resulting in increasing settlement with time.The effect of the length/diameter ratio of the socket is shown in Figure 5.1a, for the condition of the rock having a higher elastic modulus than the concrete.It will be seen that if it is desired to utilize base resistance as well as socket friction th e socket length should be less than four pile diameters. The high interface stress over the upper part of the socket will be noted.The condition of the side walls is an most-valuable factor. In a weak rock such as chalk, argillaceous shale, or clayey weathered marl, the action of the drilling tools is to cause softening and slurrying of the walls of the borehole and, in the most adverse case, the shaft friction corresponds to that emblematic of a smooth-bore hole in soft clay. In stronger and fragmented rocks the slurrying does not take place to the same extent, and there is a tendency towards the enlargement of the drill hole, resulting in better keying of the concrete to the rock. If the pile borehole is drilled through soft clay this soil may be carried down by the drilling tools to fill the cavities and smear the sides of the rock socket. This behaviour can be avoided to some extent by inserting a example and sealing it into the rock-head before move the drilling to form the rock socket, but the interior of the casing is liable(predicate) to be heavily smeared with clay which will be carried down by the drilling tools into the rock socket.As mentioned in Duncan C. Wyllie, suggests that if bentonite is used as a drilling fluid the rock socket shaft friction should be bring down to 25% of that of a clean socket unless tests can be made to sustain the actual friction which is developed.It is evident that the keying of the shaft concrete to the rock and therefore the strength of the concrete to rock draw together is dependent on the strength of the rock. Correlations between the free compression strength of the rock and rock socket bind stress have been established by Horvarth(4.50), Rosenberg and Journeaux(4.51), and Williams and Pells(4.52). The ultimate bond stress, fs, is related to the fair unconfined compression strength, quc, by the equationWhere = decrease factor relating to, quc as shown in Figure 5.1b = correction factor associated wi th cut-off position in the rush of rock as shown in Figure 5.1c.The scent of Williams and Pells in Figure 5.1b is higher than the other two, but the factor is unity in all cases for the Horvarth and the Rosenberg and Journeaux curves. It should also be noted that the factors for all trinity curves do not allow for smearing of the rock socket caused by dragdown of clay overburden or degradation of the rock.The factor is related to the mass factor, j, which is the ratio of the elastic modulus of the rock mass to that of the intact rock as shown in Figure 5.1d. If the mass factor is not known from loading tests or seismal speeding measurements, it can be obtained just about from the relationships with the rock quality duty assignment (RQD) or the discontinuity spacing quoted by Hobbs (4.53) as follows5.2 End Bearing subject mattersometimes piles are driven to an underlying layer of rock. In such cases, the engineer must evaluate the bearing capacity of the rock. The ultima te unit point resistance in rock (Goodman, 1980) is approximately.N = tan2 (45 + / 2)qu = unconfined compression strength of rock= drained angle of friction carry over 5.2a evade 5.2bThe unconfined compression strength of rock can be persistent by research lab tests on rock archetypes collected during field investigation. However, original caution should be used in obtaining the proper value of qu, because laboratory specimens usually are small in diameter. As the diameter of the specimen increases, the unconfined compression strength decreases a phenomenon referred to as the scale effect. For specimens big than about 1 m (3f) in diameter, the value of qu stiff approximately constant.There appears to be fourfold to fivefold reduction of the magnitude of qu in the process. The scale effect in rock is caused primarily by randomly distributed large and small fractures and also by progressive ruptures on the slip lines. Hence, we always recommend thatThe above table ( remand 5. 2a) lists some deputy set of (laboratory) unconfined compression strengths of rock. Representative values of the rock friction angle are given in the above table (Table 5.2b).A factor of safety of at least 3 should be used to determine the allowable point bearing capacity of piles. ThusCHAPTER 66 Pile Load Test (Vesics Method)A number of settlement analysis methods for single piles are available. These methods may be in the main classified into threesome categoriesElastic continuum methodsLoadtransfer methods numerical methodsExamples of such methods are the elastic methods proposed by Vesic (1977) and Poulos and Davis (1980), the simplified elastic methods proposed by Randolph and wroth (1978) and Fleming et al. (1992), the nonlinear loadtransfer methods proposed by Coyle and Reese (1966) and McVay et al. (1989), and the numerical methods based on advanced constitutive models of soil behaviour proposed by Jardine et al. (1986). In this paper, three representative methods are a dopted for the calibration exercise the elastic method proposed by Vesic (1977), the simplified analysis method proposed by Fleming et al. (1992), and a nonlinear loadtransfer method (McVay et al. 1989) implemented in program FB-Pier (BSI 2003).In Vesics method, the settlement of a pile under vertical loading, S, includes three componentsS = S1 + S2 + S3WhereS1 is the elastic pile compression.S2 is the pile settlement caused by the load at the pile toe.S3 is the pile settlement caused by the load contagious along the pile shaft.If the pile material is assumed to be elastic, the elastic pile compression can be measured byS1 = (Qb + Qs)L / (ApEp)Where Qb and Qs are the loads carried by the pile toe and pile shaft, independently Ap is the pile cross-section area L is the pile length Ep is the modulus of snap fastener of the pile material and is a coefficient depending on the nature of unit friction resistance distribution along the pile shaft. In this work, the distribution is assu med to be uniform and hence = 0.5. Settlement S2 may be express in a form similar to that for a shallow foundation.S2 = (qbD / Esb) (1-v2)IbWhereD is the pile width or diameterqb is the load per unit area at the pile toe qb = Qb /AbAb is the pile base areaEsb is the modulus of elasticity of the soil at the pile toe is Poissons ratioIb is an influence factor, generally Ib = 0.85S3 = (Qs / pL) (D / Ess) (1 2) IsWherep is the pile perimeter.Ess is the modulus of elasticity of the soil along the pile shaft.Is is an influence factor.The influence factor Is can be calculated by an empirical relation (Vesic 1977).Is = 2 + 0.35 (L/D)With Vesics method, both Qb and Qs are required. In this report, Qb and Qs are obtained using two methods. In the starting line method (Vesics method I), these two loads are determined from a nonlinear loadtransfer method, which will be introduced later.In the flash method (Vesics method II), these two loads are determined using empirical ratios of Qb to th e total load applied on pile Q based on field test data. Shek (2005) reported loadtransfer in 14 test piles, including 11 piles founded in soil and 3 piles founded on rock. The mean ratios of Qb /Q for the piles founded in soil and the piles founded on rock are summarized in Table 3 and applied in this calibration exercise. The mean values of Qb /Q at double the design load and the failure load are very similar. Hence, the average of the mean values is adopted for calibration at both double the design load and the failure load.In the Fleming et al. method, the settlement of a pile is given by the following approximate closed-form solution (Fleming et al. 1992)Wheren = rb / r0, r0 and rb are the radii of the pile shaft and pile toe, on an individual basis (for H-piles, ro2 = rb2 = Dh, h is the depth of the pile cross-section)G = GL/Gb, GL is the plume modulus of the soil at depth L, and Gb is the shear modulus of the soil beneath the pile toe. = Gave/GL, Gave is the average shear m odulus of the soil along the pile shaftp is the pile cruelty ratiop = Ep / GL = ln0.25 +(2.5(1 v) 0.25) G L/r0L = (2/)1/2(L/r0). If the slenderness ratio L/r0 is less than 0.5p1/2 (L/r0) the pile may be tough as effectively rigid and eq. 7 then reduces toIf the slenderness ratio L/r0 is larger than 3p1/2, the pile may be treated as endlessly long, and eq. 7 then reduces toIn this case, GL is the soil shear modulus at the bottom of the prompt pile length Lac, where Lac = 3r0p1/2.In the nonlinear loadtransfer method implemented in FB-Pier, the axial Z curve for poser the pilesoil interaction along the pile is given as (McVay et al. 1989)In-place Pile Foundation for a Tower-building ProjectIn-place Pile Foundation for a Tower-building ProjectCHAPTER 11 IntroductionPile foundations are used to carry a load and transfer the load of a given structure to the ground bearing, which is found below the ground at a considerable depth. The foundation consists of several piles and pile-cap s. Pile foundations are generally long and lean, that transfers the structure load to the underlying soil (at a greater depth) or any rock having a great load-bearing ability.The main types of materials used for piles are Wood, steel and concrete. Piles made from these materials are driven, drilled or jacked into the ground and connected to pile caps. Depending upon type of soil, pile material and load transmitting characteristic piles are classified accordingly. (Pile Foundation Design A Student Guide by Ascalew Abebe Dr Ian GN Smith).The objective of this project is to identify the design use of a cast-in-place pile foundation, for the tower-building project.The tower building project is called the Gemini Towers. The purpose of this construction (building) is to facilitate office spaces. This also resides on a rocky area. The building has been designed as per state-of-the-art designing concepts which are basically to attract foreign investors to invest in Oman. The Gemini Buildi ng has 1 basement, 1 ground and 19 floors.Cast-in-place concrete piles are shafts of concrete cast in thin shell pipes, top driven in the soil, and usually closed end. Such piles can provide up to a 200-kip capacity. The chief advantage over precast piles is the ease of changing lengths by cutting or splicing the shell. The material cost of cast-in-place piles is relatively low. They are not feasible when driving through hard soils or rock.1.1 AimThe aim of this project is to design and propose cast in-place pile foundation for a tower-building project and study the efficiency for the same. To achieve this aim the following objective has to be achieved.1.2 ObjectivesThe objectives of this project are as followingTo study the field soil condition, suitability of pile and investigate the soil.To study the advantages and efficiency of using cast-in-place pile for the building.To study the guidelines for the design of cast in-place structure according to BS 8004, 8110, 8002, etc.To desi gn the pile foundation as per the guidelines and the soil conditions (analyse the load, calculate the moment and determine the length and diameter and reinforcement).To use computer structural designing program for performing design (CAD and STAD).1.3 MethodsThe methods followed in preparing this project is by collecting the project plan and the soil investigation report. Then after that, research has been done on in-situ pile foundation type, to identify its characteristics.The next step is to study the pile designing criteria by referring to BS 8004, 8110 8002 codes to understand the guidelines, which shall be followed to accomplish the pile design. For this, the structural loads have to be analysed and identified using ultimate state design method. Then the design is processed depending on the data gathered on soil conditions, design loads and BS code guidelines.Thus, a proposal for the suitable pile will be prepared by identifying the reasons over the proposal.The commonest fun ction of piles is to transfer a load that cannot be adequately supported at shallow depths to a depth where adequate support becomes available, also against uplift forces which cause cracks and other damages on superstructure.Chapter 2 Literature Review2 Pile FoundationPile foundations are used extensively in bridges, high-rise buildings, towers and special structures. In practice, piles are generally used in groups to transmit a column load to a deeper and stronger soil stratum. Pile may respond to loading individually or as a group. In the latter case, the group and the surrounding soil will formulate a block to resist the column load. This may lead to a group capacity that is different from the total capacity of individual piles making up the group. (Adel M. Hanna et al, 2004).Pile foundations are the part of a structure used to carry and transfer the load of the structure to the bearing ground located at some depth below ground surface. The main components of the foundation are the pile cap and the piles. Piles are long and slender members which transfer the load to deeper soil or rock of high bearing capacity avoiding shallow soil of low bearing capacity. The main types of materials used for piles are Wood, steel and concrete. Piles made from these materials are driven, drilled or jacked into the ground and connected to pile caps. Depending upon type of soil, pile material and load transmitting characteristic piles are classified accordingly. (Ascalew Abebe et al, 2005)2.1 Functions of PilesThe purposes of pile foundations areto transmit a foundation load to a solid ground.to resist vertical, lateral and uplift load.A structure can be founded on piles if the soil immediately beneath its base does not have adequate bearing capacity. If the results of site investigation show that the shallow soil is unstable and weak or if the magnitude of the estimated settlement is not acceptable a pile foundation may become considered. Further, a cost estimate may indic ate that a pile foundation may be cheaper than any other compared ground improvement costs. Piles can also be used in normal ground conditions to resist horizontal loads. Piles are a convenient method of foundation for works over water, such as jetties or bridge piers. (Pile Foundation Design A Student Guide, by Ascalew Abebe Dr Ian GN Smith, 2003).2.2 Classification of Piles2.2.1 Classification of pile with respect to load transmissionEnd-bearing.Friction-piles.Mixture of cohesion piles friction piles.2.2.1.1 End bearing pilesThis type of piles is designed to transfer the structural load to a stable soil layer which is found at a greater depth below the ground. The load bearing capacity of this stratum is found by the soil penetration resistance from the pile-toe (as in figure 1.2.1.1).The pile normally has attributes of a normal column, and should be designed as per the guidelines. The pile will not collapse in a weak soil, and this should be studied only if a part of the given pile is unsupported. (Eg If it is erected on water / air). Load transmission occurs through cohesion / friction, into the soil. At times, the soil around the pile may stick to the pile surface and starts negative skin friction. This phenomenon may have an inverse effect on the pile capacity. This is mainly caused due to the soil consolidation and ground water drainage. The pile depth is determined after reviewing the results from the soil tests and site investigation reports.2.2.1.2 Friction piles (cohesion)The bearing capacity is calculated from the soil friction in contact with the pile shaft. (as in Figure 1.2.1.2).2.2.1.3 Mixture of cohesion piles friction piles.This is an extended end-bearing pile, when the soil underneath it is not hard, which bears the load. The pile is driven deep into the soil to create efficient frictional resistance. A modified version of the end-bearing pile is to have enlarged bearing base on the piles. This can be achieved by immediately pushing a lar ge portion of concrete into the soft soil layer right above the firm soil layer, to have an enlarged base. Similar result is made with bored-piles by creating a bell / cone at the bottom by the means of reaming tools. Bored piles are used as tension piles as they are provided with a bell which has a high tensile-strength. (as in figure 1.2.1.3)2.3 Cast-in-Place Pile FoundationCast-in-place piles are installed by driving to the desired penetration a heavy-section steel tube with its end temporarily closed. A reinforcing cage is next placed in a tube which is filled with concrete. The tube is withdrawn while placing the concrete or after it has been placed. In other types of pile, thin steel shells or precast concrete shells are driven by means of an internal mandrel, and concrete, with or without reinforcement, is placed in the permanent shells after withdrawing the mandrel.2.3.1 AdvantagesLength of the pile can be freely altered to cater varying ground conditions. Soil removed durin g the boring process can be verified and further tests can be made on it.Large diameter installations are possible.End enlargements up to two or three diameters are possible in clays.Pile materials are independent during driving / handling.Can be installed to greater depths in the soil.Vibration-free and noise-free while installation.Can be installed in conditions of very low headroom.Ground shocks are completely nil.2.3.2 DisadvantagesSusceptible to necking or wasting in pressing ground.Concrete is not pumped under suitable conditions and cannot be inspected.The cement on the pile shaft will be washed up, if there is a sudden surge of waster from any pressure caused underground.Special techniques need to be used to ensure enlarged pile ends.Cannot be easily prolonged above ground-level especially in river and marine structures.Sandy soils may loosen due to boring methods and base grouting may be required for gravely soils to improve base resistance.Sinking piles may result in groun d-loss, leading to settlement of nearby structures.CHAPTER 33 Load DistributionTo a great extent the design and calculation (load analysis) of pile foundations is carried out using computer software. The following calculations are also performed, assuming the following conditions are metThe pile is rigid.The pile is pinned at the top and at the bottom.Each pile receives the load only vertically (i.e. axially applied).The force P acting on the pile is proportional to the displacement U due to compression.Therefore, P = k USince P = E AE A = k Uk = (E A ) / UWhereP = vertical load componentk = material constantU = displacementE = elastic module of pile materialA = cross-sectional area of pile (Figure 3 load on single pile)The length L should not necessarily be equal to the actual length of the pile. In a group of piles. If all piles are of the same material, have same cross-sectional area and equal length L, then the value of k is the same for all piles in the group3.1 Pile foundatio ns vertical piles only3.1.1 Neutral axis loadThe pile cap is causing the vertical compression U, whose magnitude is equal for all members of the group. If Q (the vertical force acting on the pile group) is applied at the neutral axis of the pile group, then the force on a single pile will be as followsPv = Q / nWherePv = vertical component of the load on any pile from the resultant load Qn = number of vertical piles in the group (see figure 3.1.2)Q = total vertical load on pile group3.1.2 Eccentric LoadIf the same group of piles are subjected to an eccentric load Q which is causing rotation around axis z (see fig 3.1b) then for the pile i at distance rxi from axis zUi = rxi . tan Ui = rxi = Pi = k . r xi . is a small angle tan (see figure 3.1.2).Pi = force (load on a single pile i).Ui = displacement caused by the eccentric force (load) Q.rxi = distance between pile and neutral axis of pile group.rxi positive measured the same direction as e and negative when in the opposite dir ection.e = distance between point of intersection of resultant of vertical and horizontal loading with underside of pile.(Figure 3.1.2 Example of a pile foundation vertical piles)The sum of all the forces acting on the piles should be zero Mxi = Pi . rxi = k . rxi . rxi = k . r2xi == Mxi =From previous equation,Mz = MzApplying the same principle, in the x direction we get equivalent equation. If we assume that the moment MX and MZ generated by the force Q are acting on a group of pile, then the sum of forces acting on a single pile will be as followsIf we dividing each term by the cross-sectional area of the pile, A, we can establish the working stream CHAPTER 44 Load on Pile4.1 IntroductionPiles can be arranged in a number of ways so that they can support load imposed on them. Vertical piles can be designed to carry vertical loads as well as lateral loads. If required, vertical piles can be combined with raking piles to support horizontal and vertical forces. (Pile Foundation D esign A Student Guide by Ascalew Abebe Dr Ian GN Smith)Often, if a pile group is subjected to vertical force, then the calculation of load distribution on single pile that is member of the group is assumed to be the total load divided by the number of piles in the group. (Pile Foundation Design A Student Guide by Ascalew Abebe Dr Ian GN Smith)However, if a given pile group is subjected to eccentric vertical load or combination of lateral vertical load that can start moment force. Proper attention should be given during load distribution calculation.4.2 Pile ArrangementNormally, pile foundations consist of pile cap and a group of piles. The pile cap distributes the applied load to the individual piles which, in turn, transfer the load to the bearing ground. The individual piles are spaced and connected to the pile cap. Or tie beams and trimmed in order to connect the pile to the structure at cut-off level, and depending on the type of structure and eccentricity of the load, they c an be arranged in different patterns. (Pile Foundation Design A Student Guide by Ascalew Abebe Dr Ian GN Smith)(Figure 2.2 Pile Foundation Design A Student Guide by Ascalew Abebe Dr Ian GN Smith))In this section, considering pile/soil interaction, calculations on the bearing capacity of single piles subjected to compressive axial load has been described. During pile design, the following factors should be taken into considerationPile material compression and tension capacity.Deformation area of pile, bending moment capacity.Condition of the pile at the top and the end of the pile.Eccentricity of the load applied on the pile.Soil characteristics.Ground water level.4.3 The behaviour of piles under loadPiles are designed in line with the calculations based on load bearing capacity. It is based on the application of final axial-load, as per the given soil conditions at the site, within hours after the installation.This ultimate load capacity can be determined by eitherThe use of empi rical formula to predict capacity from soil properties determined by testing. orLoad test on piles at the site.When increasing compressive load is applied on the pile, the pile soil system reacts in a linear elastic way to point A on the above figure (load settlement). The pile head rebounds to the original level if the load realises above this point.When the load is increase beyond point A there is yielding at, or close to, the pile-soil interface and slippage occurs until point B is reached, when the maximum skin friction on the pile shaft will have been mobilised. If the load is realised at this stage the pile head will rebound to point C, the amount of permanent settlement being the distance OC. When the stage of full mobilisation of the base resistance is reached (point D), the pile plunges downwards without any farther increase of load, or small increases in load producing large settlements. (Pile Foundation Design A Student Guide).4.4 Geotechnical design methodsIn order to se parate their behavioural responses to applied pile load, soils are classified as either granular / noncohesive or clays/cohesive. The generic formulae used to predict soil resistance to pile load include empirical modifying factors which can be adjusted according to previous engineering experience of the influence on the accuracy of predictions of changes in soil type and other factors such as the time delay before load testing.From figure 4.1b, the load settlement response is composed of two separate components, the linear elastic shaft friction Rs and non-linear base resistance Rb. The concept of the separate evaluation of shaft friction and base resistance forms the bases of static or soil mechanics calculation of pile carrying capacity. The basic equations to be used for this are written asQ = Qb + Qs WpRc = Rb + Rs WpRt = Rs + WpWhereQ = Rc = the ultimate compression resistance of the pile.Qb = Rb = base resistance.Qs = Rs = shaft resistance.Wp = weight of the pile.Rt = tensi le resistance of pile.In terms of soil mechanics theory, the ultimate skin friction on the pile shaft is related to the horizontal effective stress acting on the shaft and the effective remoulded angle of friction between the pile and the clay and the ultimate shaft resistance Rs can be evaluated by integration of the pile-soil shear strength a over the surface area of the shaft.a = Ca + n tan aWhere n = Ks v a = Ca + KS v tanawherep = pile perimeterL = pile length = angle of friction between pile and soilKs = coefficient of lateral pressureThe ultimate bearing capacity, Rb, of the base is evaluated from the bearing capacity theoryAb = area of pile base.C = undrained strength of soil at base of pile.NC = bearing capacity factor.CHAPTER 55 Calculating the resistance of piles to compressive loads5.1 Cast in Place Piles Shaft resistanceThese piles are installed by drilling through soft overburden onto a strong rock the piles can be regarded as end-bearing elements and their working l oad is determined by the safe working stress on the pile shaft at the point of minimum cross-section, or by code of practice requirements. Bored piles drilled down for some depth into weak or weathered rocks and terminated within these rocks act partly as friction and partly as end-bearing piles.The author Duncan C. Wyllie, gives a detailed account of the factors governing the development of shaft friction over the depth of the rock socket. The factors which govern the bearing capacity and settlement of the pile are summarized as the followingThe length to diameter ratio of the socket.The strength and elastic modulus of the rock around and beneath the socket.The condition of the side walls, that is, roughness and the presence of drill cuttings or bentonite slurry.Condition of the base of the drilled hole with respect to removal of drill cuttings and other loose debris.Layering of the rock with seams of differing strength and moduli.Settlement of the pile in relation to the elastic l imit of the side-wall strength.Creep of the material at the rock/concrete interface resulting in increasing settlement with time.The effect of the length/diameter ratio of the socket is shown in Figure 5.1a, for the condition of the rock having a higher elastic modulus than the concrete.It will be seen that if it is desired to utilize base resistance as well as socket friction the socket length should be less than four pile diameters. The high interface stress over the upper part of the socket will be noted.The condition of the side walls is an important factor. In a weak rock such as chalk, clayey shale, or clayey weathered marl, the action of the drilling tools is to cause softening and slurrying of the walls of the borehole and, in the most adverse case, the shaft friction corresponds to that typical of a smooth-bore hole in soft clay. In stronger and fragmented rocks the slurrying does not take place to the same extent, and there is a tendency towards the enlargement of the dril l hole, resulting in better keying of the concrete to the rock. If the pile borehole is drilled through soft clay this soil may be carried down by the drilling tools to fill the cavities and smear the sides of the rock socket. This behaviour can be avoided to some extent by inserting a casing and sealing it into the rock-head before continuing the drilling to form the rock socket, but the interior of the casing is likely to be heavily smeared with clay which will be carried down by the drilling tools into the rock socket.As mentioned in Duncan C. Wyllie, suggests that if bentonite is used as a drilling fluid the rock socket shaft friction should be reduced to 25% of that of a clean socket unless tests can be made to verify the actual friction which is developed.It is evident that the keying of the shaft concrete to the rock and hence the strength of the concrete to rock bond is dependent on the strength of the rock. Correlations between the unconfined compression strength of the roc k and rock socket bond stress have been established by Horvarth(4.50), Rosenberg and Journeaux(4.51), and Williams and Pells(4.52). The ultimate bond stress, fs, is related to the average unconfined compression strength, quc, by the equationWhere = reduction factor relating to, quc as shown in Figure 5.1b = correction factor associated with cut-off spacing in the mass of rock as shown in Figure 5.1c.The curve of Williams and Pells in Figure 5.1b is higher than the other two, but the factor is unity in all cases for the Horvarth and the Rosenberg and Journeaux curves. It should also be noted that the factors for all three curves do not allow for smearing of the rock socket caused by dragdown of clay overburden or degradation of the rock.The factor is related to the mass factor, j, which is the ratio of the elastic modulus of the rock mass to that of the intact rock as shown in Figure 5.1d. If the mass factor is not known from loading tests or seismic velocity measurements, it can be obtained approximately from the relationships with the rock quality designation (RQD) or the discontinuity spacing quoted by Hobbs (4.53) as follows5.2 End Bearing CapacitySometimes piles are driven to an underlying layer of rock. In such cases, the engineer must evaluate the bearing capacity of the rock. The ultimate unit point resistance in rock (Goodman, 1980) is approximately.N = tan2 (45 + / 2)qu = unconfined compression strength of rock= drained angle of frictionTable 5.2aTable 5.2bThe unconfined compression strength of rock can be determined by laboratory tests on rock specimens collected during field investigation. However, extreme caution should be used in obtaining the proper value of qu, because laboratory specimens usually are small in diameter. As the diameter of the specimen increases, the unconfined compression strength decreases a phenomenon referred to as the scale effect. For specimens larger than about 1 m (3f) in diameter, the value of qu remains approximatel y constant.There appears to be fourfold to fivefold reduction of the magnitude of qu in the process. The scale effect in rock is caused primarily by randomly distributed large and small fractures and also by progressive ruptures along the slip lines. Hence, we always recommend thatThe above table (Table 5.2a) lists some representative values of (laboratory) unconfined compression strengths of rock. Representative values of the rock friction angle are given in the above table (Table 5.2b).A factor of safety of at least 3 should be used to determine the allowable point bearing capacity of piles. ThusCHAPTER 66 Pile Load Test (Vesics Method)A number of settlement analysis methods for single piles are available. These methods may be broadly classified into three categoriesElastic continuum methodsLoadtransfer methodsNumerical methodsExamples of such methods are the elastic methods proposed by Vesic (1977) and Poulos and Davis (1980), the simplified elastic methods proposed by Randolph a nd Wroth (1978) and Fleming et al. (1992), the nonlinear loadtransfer methods proposed by Coyle and Reese (1966) and McVay et al. (1989), and the numerical methods based on advanced constitutive models of soil behaviour proposed by Jardine et al. (1986). In this paper, three representative methods are adopted for the calibration exercise the elastic method proposed by Vesic (1977), the simplified analysis method proposed by Fleming et al. (1992), and a nonlinear loadtransfer method (McVay et al. 1989) implemented in program FB-Pier (BSI 2003).In Vesics method, the settlement of a pile under vertical loading, S, includes three componentsS = S1 + S2 + S3WhereS1 is the elastic pile compression.S2 is the pile settlement caused by the load at the pile toe.S3 is the pile settlement caused by the load transmitted along the pile shaft.If the pile material is assumed to be elastic, the elastic pile compression can be calculated byS1 = (Qb + Qs)L / (ApEp)Where Qb and Qs are the loads carried by the pile toe and pile shaft, respectively Ap is the pile cross-section area L is the pile length Ep is the modulus of elasticity of the pile material and is a coefficient depending on the nature of unit friction resistance distribution along the pile shaft. In this work, the distribution is assumed to be uniform and hence = 0.5. Settlement S2 may be expressed in a form similar to that for a shallow foundation.S2 = (qbD / Esb) (1-v2)IbWhereD is the pile width or diameterqb is the load per unit area at the pile toe qb = Qb /AbAb is the pile base areaEsb is the modulus of elasticity of the soil at the pile toe is Poissons ratioIb is an influence factor, generally Ib = 0.85S3 = (Qs / pL) (D / Ess) (1 2) IsWherep is the pile perimeter.Ess is the modulus of elasticity of the soil along the pile shaft.Is is an influence factor.The influence factor Is can be calculated by an empirical relation (Vesic 1977).Is = 2 + 0.35 (L/D)With Vesics method, both Qb and Qs are required. In this rep ort, Qb and Qs are obtained using two methods. In the first method (Vesics method I), these two loads are determined from a nonlinear loadtransfer method, which will be introduced later.In the second method (Vesics method II), these two loads are determined using empirical ratios of Qb to the total load applied on pile Q based on field test data. Shek (2005) reported loadtransfer in 14 test piles, including 11 piles founded in soil and 3 piles founded on rock. The mean ratios of Qb /Q for the piles founded in soil and the piles founded on rock are summarized in Table 3 and applied in this calibration exercise. The mean values of Qb /Q at twice the design load and the failure load are very similar. Hence, the average of the mean values is adopted for calibration at both twice the design load and the failure load.In the Fleming et al. method, the settlement of a pile is given by the following approximate closed-form solution (Fleming et al. 1992)Wheren = rb / r0, r0 and rb are the rad ii of the pile shaft and pile toe, respectively (for H-piles, ro2 = rb2 = Dh, h is the depth of the pile cross-section)G = GL/Gb, GL is the shear modulus of the soil at depth L, and Gb is the shear modulus of the soil beneath the pile toe. = Gave/GL, Gave is the average shear modulus of the soil along the pile shaftp is the pile stiffness ratiop = Ep / GL = ln0.25 +(2.5(1 v) 0.25) G L/r0L = (2/)1/2(L/r0). If the slenderness ratio L/r0 is less than 0.5p1/2 (L/r0) the pile may be treated as effectively rigid and eq. 7 then reduces toIf the slenderness ratio L/r0 is larger than 3p1/2, the pile may be treated as infinitely long, and eq. 7 then reduces toIn this case, GL is the soil shear modulus at the bottom of the active pile length Lac, where Lac = 3r0p1/2.In the nonlinear loadtransfer method implemented in FB-Pier, the axial Z curve for modelling the pilesoil interaction along the pile is given as (McVay et al. 1989)