PILED- RAFT FOUNDATION FOR HIGH RISE INDUSTRIAL STRUCTURE. Anantapur,Anantapuramu, India, Anantapur,Anantapuramu, India I.

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1 Iteratioal Joural of Techical Iovatio i Moder Egieerig & Sciece (IJTIMES Impact Factor: 5.22 (SJIF-2017, e-issn: Volume 4, Issue 11, November-2018 PILED- RAFT FOUNDATION FOR HIGH RISE INDUSTRIAL STRUCTURE K.Bhaskarreddy 1, Dr.c.sashidhar 2, B.Sreeivas 1 PG Scholar, Departmet of Civil Egieerig, Jawaharlal Nehru Techological Uiversity Aatapur,Aatapuramu, Idia, 2 Professor, Departmet of Civil Egieerig, Jawaharlal Nehru Techological Uiversity Aatapur,Aatapuramu, Idia Structural Egieer, BUTLAS Cosultig egieers Pvt Ltd, Hyderabad, Telagaa, Idia Abstract ---The desig of high rise buildig for idustrial structure with piled raft foudatio o clayey soil i UPSIDC idustrial area, sadila city, hardoi district. The higher load trasfer buildigs which are lies o loose soil. They caot desig with shallow foudatio. It is ecessary to provide deep foudatio.i preset area combiatio of shallow ad deep (piled-raft foudatio is used. Piled raft foudatio is adopted to reduce the total ad differetial settlemet of foudatio. I the preset study, aalysis of piled raft foudatio is doe by plate o sprig approach i which the raft is represeted by a elastic plate while the soil ad piles are modelled as bed of equivalet sprig at odal poits ad itersectig sprig respectively. The stiffess of pile is estimated by procedure give by Hazarika ad Ramaswamy(2000. For the estimatio of soil stiffess a method by de-beer ad martes (1975 is employed for sad. For clays the same is estimated usig immediate ad e-log p curve. Software for the aalysis of raft usig fiite differece method, estimatio of stiffess for soil ad pile ad structural desig of raft ad pile is developed i SAFE software. Usig this software a typical case study is aalysed ad results are preseted. Effect of coefficiet of subgrade reactio of soil ad pile stiffess o the settlemet, bedig momet, shear force ad puchig shear values of raft are studied. Key words: piled-raft foudatio, bedig momet, SAFE software I.INTRODUCTION Raft foudatio is a structure which support a arragemet of umber of colums i a row(s to trasmit load to the soil by meas of cotiuous slab. It has a advatage of reducig differetial settlemet as cocrete slab resists differetial movemets betwee the loadig positios. They are ofte required o soft or loose soils with low bearig capacity as they ca spread the loads over a larger area. Pile foudatio is used whe surface soil is usuitable for shallow foudatio, ad a firm stratum is so deep that it caot be reached ecoomically by shallow foudatio. A pile foudatio geerally much more epesive tha a shallow foudatio. It should be adopted oly whe a shallow foudatio is ot feasible. To overcome this issue, cocept of piled raft foudatio was developed.piled raft foudatios provide a ecoomical foudatio optio for circumstaces where the Performace of the raft aloe does ot satisfy the desig requiremets. A pile raft foudatio is cocept i which total load comig from super structure is partly shared by raft by through its cotact with soil ad the remaiig load is shared by piles through ski frictio. A piled raft foudatio is ecoomical as compared to the pile foudatio because piles i the case do ot have to peetrate to the full depth of clay layer but it ca be termiated at higher elevatio. Piled raft foudatios have bee used successfully i Germay ad other place where thick clay deposits eist over large depth. II.LITERATURE REVIEW Pile raft foudatio are composite geotechical structures which are characterized by their capability of sharig loads betwee their respective foudatio compoets, i.e. piles ad raft. They are particularly suitable i supportig major structures with cocetrated loads i highly compressible groud. Pile raft foudatios are required whe the soil is very weak, highly compressive over large depth ad i the presece of high water table. It is also use to resist horizotal forces i additio to vertical cocetrated load to resist uplift pressure. Davis ad Paulo s (1972 developed the cocept of piled raft foudatio, which was further described by may authors, icludig Burl et al (1977, Cooke (1986, chow ad Radolph (1994, ta ad small (1996, ki et al(2001, Paulo s (2001 etc. doli (196 aalysed the behaviour of piled raft system based o elastic solutios. A boudary elemet procedure to predict the settlemet of piles ad piles groups has bee developed by Paulo s ad Davis IJTIMES-2018@All rights reserved 89

2 (1968 ad Paulo s (1972 based o the iteractio betwee the sigle piles with rigid circular pile cap. Raft fleibility has bee cosidered by Haim ad lee (1978 by combiig the fiite elemet method for the raft with the iteractio factor procedure for the pile group. The stress distributio alog the piles shaft ad beeath the raft could ot be obtaied by these approimate methods. To overcome this rigorous study usig three dimesio fiite elemet has bee preseted by ottaviai (1975, but the aalysis was valid for maimum 15 members of piles. Later a hybrid fiite elemet elastic cotiuum method was developed by Haim ad lee (1978 cosiderig 66 piled raft. Further Griffiths et al (1991 developed a hybrid fiite elemet cotiuum- load trasfer approach to specially miimize the amout of computatios ad icrease the umber of piles (more tha 200piles i the aalysis. The effect of pile-cap-soil iteractio, load carried by the raft ad the effect of the additioal pile support o absolute ad differetial have further bee discussed by Radolph ad Real (200. III. SOIL INVESTIGATION AND SOIL RESULTS Soil ivestigatio represet method of determiig physical properties of soil at costructio site. This procedure is doe with the aim of establishig whether soil is safe ad solid for costructio. The etire process of soil ivestigatio etails differet steps ad methods. However, there are several methods like ispectio, test pits ad borig. Ispectio is the first step ad etails the eamiatio of the site. After wards test pits are dug with the aim of collectig samples. For a more detailed aalysis, borehole are made, which eables gatherig the iformatio o soil/rock strata, soil properties, ad groud waters. I the preset idustrial area to kow the soil coditios four bore hole are dug from that bore holes soil is take ad coduct tests. The results of lab tests ad bore holes 1, 2, ad 4 idicate that the strata at the site is foud to comprise of cohesive soil oly ad et stadard peetratio test is coducted i clayey regio. The S.P.T. values obtaied i the clayey layer regio preset as per bore-log charts eclosed are foud to rage from 6 to 0 idicatig Medium to Very Stiff cosistecy. The other tests coducted o soil are sieve aalysis, atterberg tests, moisture cotet test, specific gravity, ad shear test is coducted. The water table at a depth of 5.00 metre below groud level has bee adopted for calculatio purposes. The soil result are Depth of foudatio below groud level (m = 2.50 Legth of footig (m = Width of footig (m = Water Table below groud level assumed (m = Cohesio (Kg/sqcm. = 0.5 Agle of Iteral Frictio (Ø = 6 Desity above foudatio level (gms/cc = 1.97 Desity below foudatio level (gms/cc = 1.97 Overburde (toe/sqm. = 4.92 Void Ratio (eo = Net Safe Bearig Capacity (toe/sqm. = Settlemet produced (mm = Safe Allowable Pressure (toe/sqm. = 6.15 Settlemet produced for safe allowable pressure (mm = as i Sl. No. 1 ad withi safe permissible limit as per IS: IV. STRUCTURAL DESIGN OF RAFT AND PILE FOUNDATION A raft foudatio usually cosist of a cocrete slab with cosist thickess throughout its pla area, through other forms such as slab thickeed uder colum. I fact the isolated footig are essetially flat slabs. The slab directly subjected to actio of cocetrated colum loads, it is treated as structure critical i puchig shear mode as the footig. If the colum is small ad the colum load is larger substatially thick slab will be ecessary to resist puchig shear aroud the IJTIMES-2018@All rights reserved 90

3 colum. Flat slab meas a reiforced cocrete slab with or without drops, supported geerally without beams, by colums with or without flared colum heads. The pile is a small diameter colum, which are drive or cast ito groud by suitable meas. The piles may be subjected to vertical loads, horizotal loads or both, they are very useful ad ecoomical i trasferrig load through the poor soil or water to a suitable bearig stratum by meas of ed bearig. A pile ca be desiged as structural member i accordace with IS: 2911:1985 (part 1 sectio 1, 2,, ad 4. Loads from superstructure is trasferred to the piles through pile cap. The load the start gettig distributed through ski frictio ad bearig ad fially reach the toe. Thus, a pile should adequate stregth to sustai the desig load ad satisfy the desig criteria as a reiforced cocrete colum. The umerical aalysis of the piled raft foudatio has bee carried out usig SAFE 2016.The aalysis is doe with the prelimiary data provided. SAFE model has bee doe by cosiderig Plat North upward Directio (Alog Z ais. The Aalysis is carried out for all load combiatios icludig Sustaied load with Wid ad Earthquake. Calculatios ad desig of foudatios are based o related codes, IS 2911 (part 1 to (for pile foudatios, ad IS The aalysis of the sub structure, maimum shear forces, bedig momets, are computed ad compared for all cases. A. terial properties of cocrete Compressive stregth of cocrete (Fck = C0 Youg s modulus of cocrete (Ec = m 2 Poisso ratio = 0.2 B. terial properties of steel Youg s modulus of steel (Es = m 2 Yield stregth of steel = 400m 2 Ultimate stregth of steel = 500m 2 C. Raft data Thickess of slab = 750mm Legth of slab = 44m Width of slab = 25m D.Pile data Diameter of pile = 00mm Legth of pile = 17m E. Soil property Sub grade modulus = 20000K G. Raft aalysis The followig stresses are tabulated for Critical Load Combiatios. Shear Membrae Bedig Momet Q Q Qy Qy S S Sy Plat e L/C DL+0.9EE+0.9PE+1.5WL DL+0.9EE+0.9PE+1.5WL DL+1.5EO+1.5PO+1.5EQ SQX SQY SX SY SXY MkNm /m My knm/ m MykNm /m IJTIMES-2018@All rights reserved 91

4 Sy S y S y M M My My M y M y DL+0.9EE+0.9PE+1.5WL DL+0.9EO+0.9PO+1.5EQ DL+1.5EO+1.5PO+1.5EQ +Z DL+1.5EO+1.5PO+1.5EQ X DL+1.2LL+1.2EO+1.2PO +1.2EQ -Z+1.2TL +VE Sice loads are highly usymmetrical ad maimum shear stress obtaied from the aalysis are 2.m 2 i both the horizotal directios (X ad Y which is more tha the maimum allowable omial shear stress of 2.2 m 2 (for M0 mi as per I.S. 456, Table o 24 thus it is advised to maitai the raft thickess to 750mm uiformly. Figure1: Two dimesioal view of piled raft foudatio IJTIMES-2018@All rights reserved 92

5 Figure2: Three dimesioal view of piled raft foudatio V. RESULT AND DISCUSSION Detailed aalysis of pile raft foudatio has bee carried out cosiderig the effect of iteractio for all the load cases. I this report two load combiatios (115 & 168 had bee preseted cosiderig the effect of supportig soil media. A. For Load Combiatio 115 (1.0DL+1.0LL+1.0EO+1.0PO Horizotal Vertical Horizotal Directio Node L/C F KN Fz KN Fy KN F F Fy Fy Fz Fz M M My My Mz Mz IJTIMES-2018@All rights reserved 9

6 Figure : Node 2690 (Pile reactio 76 KN eceed maimum capacity B. For Load Combiatio 168(1.0DL+1.0LL+1.0EO+1.0PO+1.0EQ -X+1.0TL VE Horizotal Vertical Horizotal Directio Node L/C FkN FzkN FykN F F Fy Fy Fz Fz M M My My Mz Mz IJTIMES-2018@All rights reserved 94

7 Figure 4: Nodes (1171, 2104, 1600eceed ma capacity The maimum pile reactios for load combiatio 115 is KN ad 168 is KN based o the detailed aalysis. The pile capacity as per the geotechical report provided was 720 KN for 20. m legth. Almost 80 to 90 % utilizatio is achieved by all the piles ad the piles those are marked (i bold have eceeded the maimum capacity. However as per IS codal provisios, while cosiderig critical load case especially with seismic loads, oe or two piles ca have capacity up to 10% more tha maimum capacity. Therefore, Optimizatio could ot be achieved for the critical load cases. Pile Load capacity(kn No of Piles % of Piles < > Total VI.CONCLUSION Piled raft foudatio is adopted to reduce the total ad differet settlemet of foudatios, ad thus estimatio of settlemet profile of piled raft foudatio forms a importat desig eercise. So accordigly a method is proposed to obtai the settlemet profile of piled raft foudatio. I this proposed method, raft is represeted is represeted by a elastic plate, while the soil ad piles are modelled as bed of equivalet sprig at odal poits, ad itersectig sprig respectively. Software is developed for the aalysis of raft usig fiite differece method, estimatio of stiffess for soil ad pile ad the structural desig of raft ad pile i SAFE software. The load combiatio 115&168 had bee cosidered. The maimum pile reactios for load combiatio 115 is KN ad 168 is KN based o the detailed aalysis. I load case 115, oly ode umber 2690 eceeds maimum capacity, ad i load case 168, three ode umbers 1171,2104, 1600 eceeds maimum capacity. The aalysis adopted i the preset study is strictly applicable to vertical loadig. I highly seismic area, estimatio of the behaviour of piled raft durig earthquake becomes a importat factor i the foudatio desig process. IJTIMES-2018@All rights reserved 95

8 REFERENCES [1]. Burlad, H.B,, Broms, B.B,, et. al(1977, Behaviour of foudatio ad structure. Proceedig 1 th iteratioal coferece o soil mechaics ad foudatio egieerig, Tokyo, pp [2]. Is :code of practice for desig ad costructio of pile foudatios, part 1: cocrete piles,sectio 4bored precast cocrete piles. [].Paulo s,h.g.(1994, A approimate umerical aalysis of pile raft foudatio. Iteratioal joural for umerical ad aalytical methods i geo mechaics. [4].Horikoshi K,, ad Radolph M,F,,(1996, Cetrifuge modellig of piled raft foudatio o clay,geotechique,46(4,pp [5].Cooke R.W,,(1986,Piled raft foudatios o stiff clays, cotributio to desig philosophy, Geotechique,5(2,pp [6].Burlad,J.B,,&Wroth,C,P,(1975, Settlemet of Buildig ad Associated damge. Proceedigs of british geotechical society coferece,(april. IJTIMES-2018@All rights reserved 96