Axial Load Capacity of Cast in Place Piles from SPT and CPTU Data

Transcription

1 World Journal of Engineering and Technology, 014,, Publihed Online May 014 in SciRe. hp:// hp://dx.doi.org/10.436/wje Axial Load Capaciy of Ca in Place Pile from SPT and CPTU Daa Ergy Anamali 1, Nerian Shkodrani 1, Luia Dhimiri 1 Deparmenof Civil Engineering, Faculy of Civil Engineering, Polyechnic Univeriy of Tirana, Tirana, Albania Deparmen of Geoechnical Engineering, T. T. Soil & Earhquake Conuling, Tirana, Albania luiadhimiri@iniui.com Received 5 April 014; revied 9 May 014; acceped 16 May 014 Copyrigh 014 by auhor and Scienific Reearch Publihing Inc. Thi work i licened under he Creaive Common Aribuion Inernaional Licene (CC BY). hp://creaivecommon.org/licene/by/4.0/ Abrac Thi paper aim o deal wih he aemen of axial load capaciy for ca in place pile foundaion, which are made by he earh drill mehod, by uing he daa aken from Sandard Peneraion Te (SPT) and Piezocone Peneraion Te (CPTU). Thee e were carried ou a par of he inveigaion program for P.N.G. Terminal-Power Plan, near Semani beach, in Hoxhara marh, in he weern par of Albania. The deign of axial load capaciy of pile i baed on empirical formula uing SPT and CPTU value. Thi udy preen he reul of axial load capaciy analyi of ca in place pile by differen analyical calculaion mehod, which are baed on in iu e reul, and alo referring o he Building Sandard Law of Japan. In he end of our work, difference beween calculaion mehod by uing differen in iu e reul are hown in able and graph. Keyword Ca in Place Pile, Axial Load Capaciy, Sandard Peneraion Te (SPT), Piezocone Peneraion Te (CPTU) 1. Inroducion The conrucion ie, where he SPT and CPTU e are carried ou, i locaed in he area of Semani beach, near Fier ciy, Albania. The e conidered in hi udy, are execued according o he ie inveigaion program a Terminal Power Plan (here in afer referred a P. N. G.) in Seman. A plan of he conrucion ie and he locaion of in iu e are hown in Figure 1. The reul of 416 SPT and 1 CPTU are conidered during he axial load capaciy analyi. SPT e were carried ou, a he primarily recommended e for granular oil and oher ground condiion How o cie hi paper: Anamali, E., Shkodrani, N. and Dhimiri, L. (014) Axial Load Capaciy of Ca in Place Pile from SPT and CPTU Daa. World Journal of Engineering and Technology,, hp://dx.doi.org/10.436/wje

2 E. Anamali e al. Figure 1. Plan of geological work. where i i difficul o ample and e in laboraory. Thi e provide aemen of oil properie and foundaion deign parameer. I meaure he oil reiance o peneraion hrough compuaion of he number of blow required o drive he ampler 300 mm ino he ground, afer i ha been advance 150 mm. In recen year he N-value meaured by SPT ha been ubjeced o variou correcion and i andardized o a reference value of 60% of he poenial energy of SPT hammer [1]. Excep SPT, alo CPTU were performed, becaue he piezocone e allow he coninuou monioring of he pore preure, u, generaed during driving, in addiion o he elecrical meauremen of cone ip reiance, q c, and leeve fricion, f. The deerminaion of pile capaciy i one of he earlie applicaion of he CPT daa. CPT mehod of axial pile capaciy calculaion generally give uperior predicion, becaue CPT provide a coninuou profile of oil and i i ill he e ha give he cloe imulaion o a pile []. In hi udy, deep foundaion of ype ca in place pile are conidered. The deph of pile i kep a a conan value of 0.0 m, meanwhile he diameer varie from 0.5 m unil.0 m. The daa aken by Sandard Peneraion Te (SPT) will be involved in calculaion according o O Neill & Reee and he Japanee Deign Law. The daa aken by Piezocone Te (CPTU) will be involved in calculaion according o Ellami & Felleniu Mehod. All he reul will be preened in able and graph, o i will be poible o compare he reul obained by differen in iu eing echnique.. Axial Load Capaciy of Pile by Uing SPT In hi par are decribed analyical mehod ued o obain Ulimae Axial Load Capaciy, by uing he reul of in iu e, SPT and CPT. Alo in hi ecion of he paper, he Japanee Pracice of axial load capaciy analyi will be preened..1. Axial Load Capaciy from Japanee Mehod The oal load capaciy of pile i calculaed by uing Equaion (1), where oe bearing reiance and ide fricion reiance are boh conidered [3]. Pul P + P qa + f A Pa = = = (1) F F F q = ne uni oe bearing reiance of pile, which i calculaed by he equaion given in Table 1 f = ide fricion bearing reiance of pile A = oe area (normally, he cro ecional area of he pile) A = circumferenial area of he pile a deph z 101

3 E. Anamali e al. F = facor of afey According o Building Sandard Law of Japan he allowable axial load capaciy i defined in relaion o ulimae axial load capaciy, by uing a facor of afey F = 3, in cae of normal condiion. The ulimae bearing capaciy of oil i eimaed baed on geoechnical inveigaion. The allowable axial load capaciy of pile hall be calculaed by he equaion in paragraph Table, in cae when he oil in conac wih he pile i a of clay, or a looe and, and alo in hoe cae when i i eimaed a big liquefacion poenial of oil where are driven he pile or are inalled he ca-in-place pile [4]. P = ide-fricion reiance calculaed by he following equaion: 10 1 P = NL + ql u c ϕ () 3 N = average percuion frequency (p.. in our calculaion N are equal o ((N 1 ) 60 ) by andard peneraion e of andy ground ha i par of he ground around he foundaion pile (if i exceed 30, he value hall be 30). L = oal lengh of he foundaion pile ha i in conac wih andy ground ha i par of he ground around he foundaion pile. q u = average ingly compreive rengh of clayey ground ha i par of he ground around he foundaion pile (if i exceed 00, he value hall be 00). L c = oal lengh of he foundaion pile ha i in conac wih clayey ground ha i par of he ground around he foundaion pile. ϕ = lengh of he circumference of he foundaion pile [5]... O Neill and Reee Mehod for Toe Bearing Reiance Analyical deign of ca in place pile i baed on empirical formula developed from inrumened full cale aic load e. O Neill and Reee defined he oe bearing reiance a ha which occur a a elemen of 5% of he pile diameer. Baed on hi crierion hey recommend compuing he ne oe bearing reiance in and wih N a follow [6]: q = 57.5N 900 kpa (3) 60 N 60 = SPT N-value correced for field procedure from pile oe unil he deph B b under he oe. B b = diameer in bae. Ne uni oe bearing reiance for ca in place pile, wih diameer in bae bigger han 10 cm, in andy oil wih N according O Neill & Reee hould be reduced by muliplying wih he raio of 100 mm wih he diameer in bae of he pile. Oherwie a elemen analyi i required. Table 1. Ne uni oe-bearing reiance according o SPT-value [4]. Caegory of pile foundaion Allowable uni re of oil a he ip of he pile foundaion Driven pile q = 300N Bored preca pile made wih cemen milk mehod q = 00N Ca-in-place pile made by he earh drill mehod, ec. q = 150N In hi able N (p.. in our calculaion N are equal o ( N 1 ) hall repreen average percuion frequency baed on andard peneraion e of 60 he ground near he ip of he foundaion pile (when i exceed 60, i hall be 60). Table. Formula for eimaion of allowable load capaciy of bearing pile [4]. Allowable bearing capaciy of ground under inernal force produced by uained Allowable bearing capaciy of ground under inernal force produced by emporary 1 3 (1) P = ( qa + P) P = ( qa + P) a 3 a 10

4 E. Anamali e al. Becaue of heir low hydraulic conduciviy, i i aumed ha undrained condiion exi in clay beneah he oe of he pile. The ne uni oe bearing reiance for pile embeded in clay can be calculaed by uing he undrained hear renghh, a given in he Equaion (4). O Neill and Reee reccomend o ue in hi cae he bearing capaciy facor, which varie a a funcion of he undrained hear rengh of he oil [6]. q = N (4) c u 100 mm q r = q. B N c = facor of bearing capaciy (O Neill & Reee). u = undrained hear rengh beween he pile oe and B b under he pile oe. Ne uni oe bearing reiance for ca in place pile, wih diameer in bae bigger han 190 cm, in clayey oil wih u 50 kpa, according O Neill & Reee hould reduced by uing he reducion facor, F r, a given by he formula below [5]: q = Fq (5) r r The reducion facor i calculaed by Equaion (6):.5 F = r 1.0 ψ1bb +.5ψ ψ 1 = 0.8Bb ( DBb) ψ = u D = he deph of pile embedmen..3. β Mehod for Side Fricion Reiance When uing he β mehod he oil i divided ino layer, where each layer boundary i locaed a he oil raa boundarie or a he ground waer able. Than i compued f by he formula given below [6]: f = βσ (7) For ca in place pile embedded in and, when he value of N60 15, O Neill and Reee recommend he following value for β: z β = z 0.5 β 1.0 (8) z = he deph in he middle of he raa. Side fricion reiance, f, calculaed by uing he value of β i limied unil 190 kpa. If N 60 < 15, he value of β hould be muiplied by he raio of N For ca in place pile embedded in gravel (gravel grain >50%) Rollin, Clayon and Mikeell recommend he following value for β: β 3.4e 0.085z = 0.5 β 3.0 (6) (9) For ca in place pile embeded in gravelly SAND (gravel grain 5% - 50%) he following value of β are recommended: 0.75 β = z 0.5 β 1.8 (10) For ca in place pile embedded in il or clay he following value of β are reccommended by Felleniu: β = (Sil) β = (Clay) (11) 3. Axial Load Capaciy of Pile by Uing CPT Te Daa 3.1. Elami and Felleniu Mehod Elami and Felleniu recommend he applicaion of an addiional pore waer preure u o correc he value of 103

5 E. Anamali e al. effecive reiance of cone a follow [6]: q E = effecive reiance of cone. q T = correced reiance of cone. u = pore waer preure meaure a cone ip. q = q u (1) E T 3.. Toe Bearing Reiance Elami & Felleniu mehod i widely ued o correc he ne oe bearing reiance, q, wih he effecive reiance of cone, q E. Thee analyi conider he value of q E only wihing he following zone: Pile inalled hrough weak oil a he beginning and han paing hrough compac oil 8B above he end of he cone and 4B below i. Pile inalled hrough compac oil a he beggining han paing hrough weak oil B above he end of he cone and 4B below i. Average value, q Eg, of n value q E meaured wih he defined deph can be calculaed a a geomerical average. Ne oe bearing reiance, q, hould be correlaed in empirically manner a hown in Equaion (13) [6]: q = Cq (13) Eg C = bearing reiance coefficien = 1. q = geomeric average effecive reiance of cone. Eg 3.3. Side Fricion Reiance The ide fricion reiance by uing he daa of CPT hould be calculaed by mean of Equaion (15) [6]: f = Cq (14) E The value of C depend on oil ype and are aken in Table 3. Menawhile oil claificaion i done in grapphical way by uing he CPT daa. C = coefficien of ide fricion. q = effecive reiance of cone. E 4. Reul and Dicuion Since he analye of Axial Load Capaciy of pile in hi conrucion ie are relaed o he daa of SPT and CPTU e, a fir we dialed wih he reul of hee e, which were repored in he geological udy. Average field SPT N-value, correced SPT(N 1 ) 60 -value, average q c -value and f c -value are conidered. The geological profile are conruced for every borehole (1 borehole in oal). In Figure, Figure 3 and Figure 4 are given he variance of field SPT N-value, SPTN 60 -value and field CPTUq c -value, f c -value wih deph for 1 borehole conidered in hi paper. Table 3. Side fricion coefficien, C according o Elami & Felleniu. Soil Type Range C Typical Deign Value Sof eniive oil Clay Siff clay or mixure or clay and il Mixure of il and and Sand

6 E. Anamali e al. SPT - N value, N 60 value Deph v. N Deph, D (m) 0 1 Figure. Field SPT N-value, SPTN 60 value. Cone reiance, q C value (MPa) Deph v. q C Deph, D (m) 0 1 Figure 3. Field CPTUq c -value. The axial load capaciy analye are performed for each borehole baed on he analyical mehod already decribed above. Conidering oil profile and oil condiion of every borehole, a uiable deph of 0 m i eleced for ca-in- 105

7 E. Anamali e al. place reinforced concree pile foundaion. Pile lengh i no varied; we have fixed i in a value of 0 m. The conidered pile widh (pile diameer) i varied in he inerval m. All he reul of our geoechnical calculaion relaed o axial load capaciy of pile are preened in char conidering variou pile diameer (ee Figure 5). In hee char, each graph preen axial load capaciy relaed o pile diameer in cerain oil condiion which belong o a cerain borehole [7]. From he reul preened in Table 4, Figure 5 and Figure 6, i i hown ha calculaed value of axial load capaciy baed on he SPT, CPTU daa and on Japanee pracice of deign don differ very much. We ee ha Fricion reiance, f c value (MPa) Deph v. f c Deph, D (m) 0 1 Figure 4. Field CPTUf c -value. Table 4. Axial load capaciy for ca in place pile foundaion (D = 0.0 m). Mehod CPT Mehod SPT Mehod (O Neil & Reee) Japanee mehod (by SPT) Table of axial capaciy of ca in place pile foundaion wih 0 m lengh, baed on 3 mehod Axial load capaciy P a (kn) B (m)

8 E. Anamali e al. Axial Load Capaciy, Pa (kn) Axial Load Capaciy of Drilled Pile From SPT Daa FromO'Neill & Reee (L = 0 m) Diameer of Pile, B (m) 0 1 Axial Load Capaciy, Pa (kn) Axial Load Capaciy of Drilled Pile From SPT Daa From Japonee Pracice(L = 0 m) Diameer of Pile, B (m) 0 1 Figure 5. Axial load capaciy of ca in place pile by SPT and baed calculaion mehod. conruced curve in all cae are imilar and he gap beween hem i no ignifican, epecially when he diameer i in he range of m. We can ay ha all mehod give comparable and conien reul for pile which have he ame dimenion and are inalled in he ame oil urrounding. 5. Concluion Axial load capaciie of pile a P.N.G. Terminal-Power Plan are aeed in hi paper. From he reul of calculaion and dicuion of hem he below concluion have reuled from he conrucion ie menioned above. The axial load in pile varie from one mehod of calculaion o anoher. According o he SPT baed calculaion, known a O Neill and Reee mehod, he axial load capaciie varied from 400 up o 400 kn. According o he Japanee Deign Law he reul vary from 500 o 4010 kn. The reul aken by CPT baed calculaion mehod and he value of axial mode can be from 500 up o 1480 kn. Maximal axial load capaciy i reached according o Japanee Deign Law, which i 4010 kn. 107

9 E. Anamali e al. Axial Load Capaciy of Drilled Pile From CPTU Daa (L = 0 m) Axial Load Capaciy, P a (kn) Diameer of Pile, B (m) 0 1 Figure 6. Axial load capaciy of ca in place pile by CPT and baed calculaion mehod. According o he calculaion baed on CPT reul he main imporan componen of oal axial load capaciy i he oe bearing capaciy, deermined by he value of q c and correlaed by q. A he pile oe i uppored by a layer of dene and. Thi i he reaon ha beween he oher graph a gap exi in hi one. Oher pile have almo he ame axial load capaciy, o he graph do no creae coniderable gap beween each oher. Concerning o SPT, i i ofen noiced ha for he ame SPT N-value according o wo differen mehod we obain wo differen axial load for pile diameer. Thi mean ha he real difference i aribued o oe bearing reiance, becaue ide fricion reiance i almo he ame in hee cae. Thi i due o differen correlaion mehod of SPT daa. Reference [1] Schnaid F. (009) In Siu Teing in Geomechanic, 1 Ediion, Taylor and Franci, London, New York. [] Lunne, T., Roberon, P.K. and Powell, J.J.M. (1997) Cone Peneraion Teing in Geoechnical Pracice. 1 Ediion, E & FNSpon Pre, Abingdon. [3] Felleniu, H.B. (009) Baic of Foundaion Deign. Elecronic Ediion (The Red Book). [4] Shkodrani, N. (01) Dinamika e Piloave. Parime Bazedhe Zabime. 1 Ediion, Pegi Publihe, Tirana. [5] Sugimura, Y., Fujiwara, K., Ohgi, T. and Karkee, M.B. (1997) Seimic Behaviour of Pile Supporing Tall Building and he Conideraion of Ground Repone Effec in Deign. Proceeding of he fourh Conference on Tall Building in Seimic Region, Tall Building for he 1 Cenury, Lo Angelo, California, Lo Angelo Tall Building Srucural Deign Council and he Council on Tall Building and Urban Haba. [6] Coduo, D.P. (001) Foundaion Deign/Principle and Pracice. nd Ediion, Prenice-Hall, Inc., New Jerey. [7] Shkodrani, N. and Lako, N. (008) Load Capaciy of Pile in Japanee and Albanian Pracice of Deign. Proceeding of Second Briih Geoechnical Aociaion Inernaional Conference of Foundaion, Scoland, 4 June