On settlement of stone column foundation by Priebe s method

Transcription

1 Proeeding of the Intitution of Civil Engineer Ground Improvement 13 May 010 Iue GI Page doi: /grim Paper Reeived 13/0/009 epted 04/01/010 Keyword: foundation/ mathematial modelling Souhir Ellouze itant Profeor, Univerité de Gabè, Tuniia Mounir Bouaida Profeor, Univerité Tuni El Manar, Unité de Reherhe Ingénierie de Géotehnique, Tuni, Tuniia Laaad Hazzar PhD tudent, Univerité de Sherbrooke, Quebe, Canada Huein Mroueh oiate Profeor, Univerité de Siene et Tehnologie de Lille, Laboratoire de Méanique de Lille, Frane On ettlement of tone olumn foundation by Priebe method S. Ellouze, M. Bouaida, L. Hazzar and H. Mroueh Several ontribution have been uggeted to etimate the aumed linear elati ettlement of foundation on olumnar reinfored oil. number of author have onidered the o-alled Priebe method, whih ha been extenively ued worldwide, and they have made uggetion epeially for oft lay reinfored by tone olumn. Thi paper firt offer a ritial analyi of the emi-empirial Priebe method by pointing out ome inonitenie related to aumption made and the theoretial derivation of the ettlement formula. diuion of the limitation of Priebe method for ettlement etimation of foundation on oft oil reinfored by tone olumn, with repet to other method i inluded. Seond, a omparion ha been undertaken between predition by Priebe method and other deign method for three tone olumn projet in whih ome in itu data were reorded. On the bai of the tudied ae hitorie, it i onluded that reoure to other available and imple method of deign i more uitable than the ue of Priebe method. NOTTION grid area tone olumn area K a oeffiient of ative earth preure for olumn material P preure within the olumn along depth ª total unit weight of initial oil d depth of uboil layer from ground urfae í Poion ratio of native oil. frition angle of olumn material j 1. INTRODUCTION Evaluation of the tability of foundation reting on weak oil layer require predition of ettlement. It i well known that tone olumn repreent one of the popular oil improvement tehnique ued to inreae the bearing apaity and to redue the ettlement of foundation ontruted on oft oil layer extending to a depth of 0 to 30 m. Other advantage in the ue of tone olumn are aeleration of primary onolidation ettlement and the prevention of liquefation (dalier and El Gamal, 004). Variou method to etimate the ettlement of reinfored oil by tone olumn have been propoed in the pat, and in mot ae the linear elati behaviour for reinfored oil ontituent wa aumed. Thee method have inluded empirial method (Greenwood, 1970), emi-empirial method (Priebe, 199), analytial method (Balaam and Booker, 1981; Bouaida et al., 003; Norme Françaie, 00) and finally numerial method. In addition, other ontribution have alo been propoed baed on the ompoite ell model a onidered by Pooroohab and Meyerhof (1997). The firt part of thi paper preent an evaluation of the emiempirial Priebe method, namely the tep adopted for deign and the aumption for the etimation of ettlement a detailed in Priebe (199). Furthermore, referring to everal publiation whih have addreed Priebe method (Dhouib et al., 004; Dhouib and Blondeau, 00; Priebe, 004), it appear that ome relationhip have not been thoroughly written in omparion with the original paper (Priebe, 199). The eond part foue on a omparion between ettlement predition by Priebe method and other method programmed in Column oftware. Thi omparion wa related to three ae hitorie of oft oil reinfored by tone olumn.. PRIEBE S METHOD.1. Priebe method: bai aumption The bai of Priebe method wa developed ome 30 year ago and then publihed (Priebe, 197). Subequently, everal adaptation, extenion and upplement have been inorporated and thee modifiation jutify a new and omprehenive deription of the method whih refer to the improvement effet of tone olumn in a oil whih i otherwie unaltered in omparion with the initial oil. In a firt tep an improvement fator, denoted by n 0,i introdued by whih tone olumn improve the mehanial harateriti of the initial oil in omparion with it pretreatment propertie (without olumn). ording to thi improvement fator, Young modulu of the ompoite ytem i inreaed and, ubequently, the ettlement i redued. ll further tep of deign refer to thi bai priniple. Reinforement by tone olumn only allow a more or le aurate evaluation for the well-defined ae of an unlimited load area ubjeted to an unlimited olumn grid. In thi ae a unit ell with area i onidered, whih onit of a ingle olumn with ro-etion and the tributary area of the Ground Improvement 13 Iue GI On ettlement of tone olumn foundation by Priebe method Ellouze et al. 101

2 urrounding oil, o that the improvement area ratio i given by /. Furthermore the following idealied ondition are aumed. (a) The olumn i baed on a rigid layer (end-bearing). (b) The olumn material i non-ompreible. () The unit weight of olumn material and initial oil are negleted... Original verion of Priebe method Baed on Priebe reaoning, the olumn an never fail a endbearing apaity element and any ettlement of the load area lead to a bulging of the olumn although the volume remain ontant over it entire length. The improvement of a oil ahieved in uh ondition by the intallation of tone olumn i evaluated baed on the aumption that the tone olumn material hear from the beginning wherea the urrounding oil reat elatially. Furthermore, the oil urrounding the olumn i aumed to be already expanded during the tone olumn intallation to uh an extent that it initial reitane orrepond to the liquid tate, namely the oeffiient of earth preure amount to K ¼ 1. The reult of uh an evaluation i expreed by mean of the bai improvement fator n 0 a Equation 1 or Equation 4 for non-ompreible olumn material. Rather, it oinide at bet with the ratio of the ontrained, or oedometri, moduli of olumn material and initial oil. It i relatively eay to determine the improvement area ratio of olumn ro-etion and grid ize ( /) 1 for whih the bai improvement fator orrepond to the ratio of the ontrained (oedometri) moduli of olumn and initial oil D /D.iti aumed that í ¼ 1/3, the lower poitive reult of the following expreion (with n 0 ¼ D /D ) deliver the required improvement area ratio ( /) 1. Thu 1 ¼ 4K aðn 0 Þþ 8K a ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 4K a ðn 0 Þþ þ 1K aðn 0 1Þ 4K a 1 4K a 1 an approximation, the ompreibility of the olumn material an be onidered by uing a redued improvement fator n 1, whih an be omputed on the bai of the modified area ratio / given by: 1 n 0 ¼ 1 þ 1 þ f í, 3 K a f í, 17 4 ¼ 1 = þ ð =Þ where the additional amount ( /)of( /) i determined by f í, ¼ (1 í )(1 =) 1 í þ = 7 1 ¼ 1 ð =Þ 1 3 K a ¼ tan 4 j where j denote the frition angle of olumn material. dopting, for the native oil, a Poion ratio of í ¼ 1/3, whih i adequate for the tate of final ettlement in mot ae, lead to the imple expreion 4 n 0 ¼ 1 þ 4 4K a Taking aount of the ompreibility of olumn material Conideration hould alo be given to the olumn bakfill material whih i now aumed ompreible. Therefore, any load aue ettlement whih i not onneted with the bulging of the olumn. ordingly, in the ae where the improvement area ratio tend to / ¼ 1, the atual improvement fator doe not ahieve an infinite value of n 0 a determined theoretially from Subequently, the modified improvement ratio n 1 an be omputed baed on the following formula 8 n 1 ¼ 1 þ 4 4K a Taking aount of depth Uing Priebe method it i aumed initially that unit weight of tone olumn and the native oil are negleted. Then, the initial preure differene between the olumn and the oil depend olely on the ditribution of foundation load and it i ontant over the entire length of the olumn. Neverthele, beaue of the additional effet of the weight of the oil and of the olumn, repetively, the preure differene dereae aymptotially with depth. depth fator f d i then introdued a the ratio between the initial tre differene at the urfae of the reinfored oil (z ¼ 0) and tre differene at a given depth (z. 0). Baed on thi, the improvement fator i inreaed from n 1 to n ¼ f d n 1. It i uggeted (Priebe, 199) that the depth fator f d i omputed baed on the following formula 10 Ground Improvement 13 Iue GI On ettlement of tone olumn foundation by Priebe method Ellouze et al.

3 9 f d ¼ 1 1 þ K a 1 K a X ð ª dþ where d in Equation 9 i referred to a improvement depth (Priebe, 199), for whih the vertial tre P ª d ¼ ó v i omputed a detailed in Dhouib et al. (004). The main onern i whih depth of improvement hould be ued to ompute fator f d? In parallel, after Priebe (199) the limitation of depth fator ha been mentioned a follow 10 1 < f d < D =D p = p P where p i the preure within the initial oil. In relation to Equation 10, Dhouib and Blondeau (00) tated that for rigid foundation then, ine equal ettlement i aumed, the required value i f d ¼ 1. In the ame publiation (Dhouib and Blondeau, 00) for a ae hitory whih dealt with a irular rigid raft foundation in an axiymmetri ondition, the depth fator onidered for the deign, a dedution after fator n, ha an upper value f d ¼.98. Thi fat well illutrate how the deign proedure i miundertood, regardle of the bakground of the uggeted formula, for ettlement predition by Priebe method. Thi ituation i very important ine the bet ettlement i predited by the ue of depth fator. 3. CRITICISM OF PRIEBE S METHOD 3.1. Conerning the deign tep detailed by Dhouib et al. (004), the theoretial framework of Priebe method adopted the ompoite ell (CC) model. However, ome inonitenie are noted, baed on aumption onidered for thi model. Indeed, in a firt tep, Priebe onider a ylindrial avity ubjeted to lateral expanion during whih zero vertial deformation i aumed in order to give a olution expreed in plane tre ondition. In a eond tep, thi olution i inorporated in the CC model for whih there i a ditribution of vertial tre generating non-null vertial deformation, and, onequently, the ettlement i aumed ontant. It i noted that Priebe method i arried out by uing the ame CC model for two different problem (from the loading ondition point of view): firt the lateral expanion of a ylindrial avity, and eond a vertial loading. Then, the ombination uing the priniple of uperpoition of the two tate of tre olution i not obviou (Salençon, 1988). ording to the alulation given in Dhouib and Blondeau (00), the deign formulae appear of omplex ue, epeially, beaue of the emi-empirial harater of thi method a tated by Dhouib (00). For etimating fator n 1, the aumption to take n 0 ¼ D /D i not lear, and no explanation i provided onerning how to derive Equation 8 tarting from Equation 4. Thi may explain the improvement given by fator n 1 in omparion with n 0. Furthermore, Equation 9 how that the depth fator depend on the unit weight of initial oil, wherea it wa aumed earlier that unit weight of reinfored oil ontituent are negleted. Then, the ue of fator f d, whih further improve the redution of ettlement, need to be larified. In onluion, the tep of the deign proedure given by Priebe method are not onneted mathematially and they ue different implifiation and approximation. 3.. Conerning publihed paper The expreion of n 0 in Equation 4, ( /) 1 in Equation and n 1 in Equation 8 are ompletely different in the referene of Priebe (199) and Priebe (004). In the publiation by Dhouib and hi o-worker (Dhouib et al., 004; Dhouib and Blondeau, 00) onerning the tudied appliation dealing with a irular raft in axiymetri ondition, the ettlement of the non-reinfored oil i predited in linear elatiity, but on the other hand, the ettlement of the reinfored oil i etimated in a partiular manner. In addition, in thee lat two referene itation, the oedometri modulu i written 11 E oed ¼ (1 þ í)(1 í) E (1 í) whih orrepond to the denoted modulu D (Dhouib et al., 004) but it i different from the atual oedometri (ontrained) modulu expreed by Salençon (1988) 1 E oed ¼ (1 í) (1 þ í)(1 í) E Thu, Equation 11 need to be orreted in the above referene Comparion between Priebe method and deign method inorporated in Column 1.0 oftware The Frenh reommendation (Norme Françaie, 00) and Balaam and Booker method onider the unit ell model a aumed by Priebe model to predit the ettlement of reinfored oil, wherea the ame method, whih an be laified a rational method, adopt the linear elati harateriti, namely Young modulu and Poion ratio a oil parameter. However, for Priebe method, only a Poion ratio of í ¼ 0.3 i onidered. In parallel the deign method of Bouaida et al. (003) inorporated in Column 1. 0 oftware ha the advantage of onidering a three-dimenional model for reinfored oil but till ue the linear elati model, a in the Frenh reommendation and Balaam and Booker method. The emi-empirial Priebe method ue, in addition, the internal frition angle of tone material a a parameter for ettlement predition. The frition angle a a failure harateriti, whih i quite different from elati harateriti, i not onidered by the method of deign Ground Improvement 13 Iue GI On ettlement of tone olumn foundation by Priebe method Ellouze et al. 103

4 inorporated in the Column 1. 0 oftware, whih all ue the linear elati harateriti. 4. STUDIED CSE HISTORIES In the following etion, three ae hitorie are examined to ompare the method of ettlement predition inorporated in Column oftware with Priebe method. The latter ue the ettlement redution fator defined a the ratio of foundation ettlement for original ground ondition to final ettlement after improvement. Then, for all tudied ae hitorie, a omparion between ettlement predition i preented in term of the ettlement redution fator Oil torage tank at Zarzi Thi i a 4 m diameter tank built at Zarzi terminal (Tuniia) on an area relaimed a embankment (Solétanhe-Bahy, 1990). The working load of the tank wa approximated a a quai-uniform tre of 10 kpa, whih largely exeeded the allowed bearing apaity of the initial oil. In order to inreae the bearing apaity and to redue the ettlement of the tank at allowed value, reinforement by tone olumn wa adopted to enure the tability of the tank wa guaranteed. The reinforement wa exeuted along an average depth H ¼ 7 m with a nominal diameter of olumn equal to 1. m intalled in a triangular pattern. The oil wa improved on a irular area, the radiu being the radiu of the tank + 4 m, whih implie an improved area ratio of approximately 3%. The harateriti of the native oil and ontitutive olumn material are given in Figure 1. The ettlement of non-reinfored oil wa etimated to be about 3 m underneath the entre-line of the tank, wherea the ettlement at the edge of tank wa m. In the alulation, the ettlement of reinfored oil i predited along a mall depth H ompared to the tank diameter: H/R ¼ 7/4 ¼ Conequently, it i reaonable to neglet the horizontal diplaement of the reinfored oil, epeially at the entre-line of tank. Moreover, ine the reinfored oil area i greater than the tank area, the aumption of null horizontal diplaement beome more realiti. It i aumed that the tank i arrying uniform load q. Thi type of loading yield, on the oil urfae, an exe of vertial tre denoted by ó, whih varie with the ditane from the tank entre-line. Indeed ó entre ¼ q, and ó edge ¼ 0. 48q. The ettlement predition at the entre-line of the tank and it edge that were obtained uing the oftware Column (Bouaida et al., 009) and Priebe method are preented in Table 1. In fat, uing oil harateriti and under the urharge of 10 kpa, the ettlement predition wa dedued by different method. By uing the unreinfored oil ettlement value of 3 m at the entre-line of the tank and m at it edge the value of the ettlement redution fator wa dedued. It i notied that the reinforement by tone olumn led to ignifiant ettlement redution. For the majority of method, thi redution wa about three to five time the ettlement of reinfored oil. Furthermore, for thi projet, by omparing 4 m Tank E 3 MPa C kpa γ 17 kn/m ν E ϕ 3 MPa 4 γ 18 kn/m ν m Looe ilty and Marl tone Figure 1. Charateriti of the native oil and ontitutive olumn material 104 Ground Improvement 13 Iue GI On ettlement of tone olumn foundation by Priebe method Ellouze et al.

5 Method Settlement of reinfored oil at entre-line of tank: m Settlement of reinfored oil at edge of tank: m Settlement redution fator at entre-line of tank Settlement redution fator at edge of tank Reorded Bouaida et al. (003) Frenh tandard (Norme Françaie, 00) Balaam and Booker (1981) Priebe (199) Table 1. Comparion between predition of tank ettlement uing Column oftware and Priebe method predition an agreement ha been hown between the variational approah and the Frenh reommendation (Norme Françaie, 00), depite the differene between the model adopted by thee method. In fat, the predited ettlement by the two method appear the loet to reorded one at the edge of the tank. Uing the improvement fator n, the predited ettlement by Priebe method at the entre-line of the tank appear omparable with the predition by other method (variational (Bouaida et al., 003), Frenh reommendation (Norme Françaie, 00) and Balaam and Booker (1981)) programmed in Column oftware. For the predited ettlement at the edge of the tank, Priebe method underetimated the ettlement aording to the reorded ettlement (averaged value). 4.. Damiette projet The data onidered are from a tone olumn projet tudied by Vibroflottation (000). The oil profile wa formed by a oft lay layer, 1. m thik, overed by a andy layer 1.7 m thik. The oft lay wa reinfored with vibro-diplaement tone olumn, 1. 1 m diameter and with. 7 m triangular grid paing, implying an improvement area ratio of 1%. The parameter of the two oil layer and olumn material are ummaried in Table. To tudy the behaviour of reinfored oil the ompoite ell model depited in Figure wa onidered (Guetif et al., 007). Parameter of oil E 9: kpa í9 j9: degree Sand Soft lay Column material Compated and Table. Parameter of the reinfored oil ytem (Damiette projet) m q 100 kpa Sand Clay For thi ae hitory, the upper and layer wa aumed to behave like a urharge applied to the reinfored oft lay. Settlement predition preented in Guetif et al. (007) and thoe provided by Column oftware were ompared with all predition uing Priebe method. The overall reult are ummaried in Table 3. The value of ettlement fator redution wa dedued from the value of ettlement of non-reinfored oil. In fat, for the different method, namely thoe inorporated in Column oftware and in Priebe method, the linear elati behaviour wa ued to alulate the unreinfored ettlement whih wa about 3 m. In ontrat, by uing Plaxi oftware, the predited ettlement of unreinfored oil ettlement wa equal to 4 m. For thi axiymmetri model the predited ettlement derived uing Plaxi oftware wa underetimated in omparion with z 1 1 m Figure. The ompoite ell model m 1 7 m 1 7 m Method Settlement of reinfored oil at entre-line of tank: m Settlement redution fator Plaxi oftware Bouaida et al. (003) Frenh tandard (Norme Françaie, 00) Balaam and Booker (1981) Priebe (199) (with n 0 ) Priebe (199) (with n 1 ) Priebe (199) (with n )..40 Table 3. Comparion between predited ettlement with everal method (Damiette projet) Ground Improvement 13 Iue GI On ettlement of tone olumn foundation by Priebe method Ellouze et al. 10

6 the ettlement etimation by other method. Thee latter method, whih were programmed in Column oftware gave almot the ame predition of ettlement. On the other hand, the predited ettlement by Priebe method largely varied from one ondition to another, namely when uing either the n 0 or n 1 or n fator. To onlude, it i diffiult to deide what i the appropriate Priebe predition to adopt in thi example? 4.3. Tank foundation at Canvey Iland (Priebe, 199) 3 m diameter tank wa ubjeted to an applied load of about 130 kpa. The tank wa founded on a overing layer of 1 m thikne pread above reinfored oil by tone olumn, 10 m long and et in a triangular pattern with paing of 1. m and an average diameter of 0.7 m, a reorded at the urfae after intallation. The improved trata ompried ome 0. 4 m of top oil and onited of a 9 m depth of ilty and layey oil with the preene of oaional poket of peat. Column were embedded in medium dene ilty fine and whih wa aumed to form a rigid tratum. Referred to depth, the harateriti of the initial oil are ummaried in Table 4. Linear elati harateriti E ¼ 100E S and í ¼ 0. were adopted for the material of the tone olumn. The improvement area ratio wa about %. The ettlement at the entre-line of the tank before reinforement wa etimated to be 40 m. Predition of the ettlement of the reinfored oil by everal method are preented in Table. ording to the predition obtained uing the method of ettlement alulation inorporated in Column oftware (variational method (Bouaida et al., 003), Balaam and Booker (1981), Chow (199) and the Frenh reommendation (Norme Françaie, 00)) it an be een that the Priebe method groly overetimated the ettlement of reinfored oil by tone olumn. Further, a remarkable differene between the value of fator n taken from the hart and thoe alulated by n ¼ f d n 1 i quetionable. Studying Priebe example ha highlighted the very onervative predition of the ettlement redution fator by Priebe method, epeially when a very high Young modulu of tone olumn material wa onidered, namely E ¼ 100E with % a improvement area ratio. a matter of fat, by all method uing the linear elati framework, a redution of ettlement of nine time wa expeted wherea the predition by Priebe method approahe three time the ettlement redution. Thi example demontrate the emi-empirial nature of Priebe method whih hould be handled arefully.. CONCLUSIONS Several paper have deribed Priebe method thoroughly by illutrated example. In thi paper, everal apet of the method have been ritially evaluated and it ha been proved that the aumption and theoretial derivation of the ettlement formula are retritive for tone olumn reinforement and, ometime, are not lear. Furthermore, ome formulae are different from one publiation to another, and o an adjutment i needed to obtain the orret expreion. Priebe method ha been ued worldwide for projet related to the reinforement of oil by tone olumn. However, they are aimed eentially at the predition of ettlement and are olely devoted to the tone olumn tehnique. In the preent tudy, Column oftware ha been ued a a tool for omparion between ettlement predition given, on the one hand, by Priebe method and, on the other hand, by other linear elati model. From three analyed ae hitorie, global agreement wa found between predition by the linear elati model, wherea a differene, either inignifiant or muh different wa noted when Priebe method wa ued for predition. Layer n Nature Thikne: m í E: kpa 1 Soft oil Very oft oil Very oft oil Firm oil Table 4. Charateriti of oil (Priebe example) Method Settlement of reinfored oil: m Settlement redution fator Frenh tandard (Norme Françaie, 00) Bouaida et al. (003) Balaam and Booker (1981) Chow (199) Priebe (199) (with n 0 ) Priebe (199) (with n 1 ) Priebe (199) (with n from urve) Priebe (199) (with n from formula) Table. Predited ettlement with everal method (Priebe example) 10 Ground Improvement 13 Iue GI On ettlement of tone olumn foundation by Priebe method Ellouze et al.

7 REFERENCES dalier K and El Gamal (004) Mitigation of liquefation and aoiated ground deformation by tone olumn. Engineering Geology 7(3 4): 7 91 Balaam NP and Booker JR (1981) nalyi of rigid raft upported by granular pile. International Journal for Numerial and nalytial Method in Geomehani (4): Bouaida M, Guetif Z, De Buhan P and Dormieux L (003) Variational approah for ettlement etimation of a foundation on oil reinfored by olumn. Revue Françaie de Géotehnique 10(1): 1 9 (in Frenh). Bouaida M, Jellali B and Porbaha (009) Limit analyi of rigid foundation on floating olumn. International Journal of Geomehani, SCE 9(3): Chow YK (199) Settlement analyi of and ompation pile. Soil and Foundation 3(1): Dhouib (00) bout the paper: Reommendation for the deign, alulation, intallation and ontrol of tone olumn foundation under building and truture enitive to ettlement. Revue Françaie de Géotehnique 117(4): 3 (in Frenh). Dhouib and Blondeau F (00) Méthode de jutifiation. In Colonne Ballatée. Pree de Pont et Chauée, Pari, pp (in Frenh). Dhouib, Wehr J, Soyez B and Priebe HJ (004) Priebe method: origin, development and appliation. Proeeding of International Sympoium, SEP-GI, Pari, 9 10 September. Pree de Pont et Chauée, Pari, pp (in Frenh). Greenwood D (1970) Mehanial improvement of oil below ground urfae. Proeeding of the Conferene on Ground Engineering, Intitution of Civil Engineer, London, paper II: pp. 11. Guetif Z, Bouaida M and Debat JM (007) Improved oft lay harateriti due to tone olumn intallation. Computer and Geotehni 34(): Norme Françaie (00) Reommendation for the deign, alulation, intallation and ontrol of tone olumn foundation under building and truture enitive to ettlement. Revue Françaie de Géotehnique 111(): 3 1. Pooroohab HB and Meyerhof GG (1997) nalyi of behaviour of tone olumn and lime olumn. Computer and Geotehni 0(1): Priebe HJ (197) Etimating ettlement in a gravel olumn onolidated oil. Die Bautehnik 3(): 10 1 (in German). Priebe HJ (199) The deign of vibro replaement. Grounding Engineering Deember: Priebe HJ (004) The deign of tone olumn. Proeeding of International Sympoium, SEP-GI, Pari, 9 10 September. Pree de Pont et Chauée, Pari, p. (in Frenh). Salençon J (1988) Continuum mehani one-dimenional media. In Elatiité Milieux Curviligne. Edition Ellipe, Pari. Solétanhe-Bahy (1990) Foundation on reinfored oil by tone olumn, oil torage tank at Zarzi. In Projet MRETP, Tuniia. Solétanhe, ix-en-provene, Frane. Vibroflottation (000) Geotehnial Report of the Damiette Projet, Egypt. Solétanhe, ix-en-provene, Frane. What do you think? To diu thi paper, pleae up to 00 word to the editor at journal@ie.org.uk. Your ontribution will be forwarded to the author() for a reply and, if onidered appropriate by the editorial panel, will be publihed a diuion in a future iue of the journal. Proeeding journal rely entirely on ontribution ent in by ivil engineering profeional, aademi and tudent. Paper hould be word long (briefing paper hould be word long), with adequate illutration and referene. You an ubmit your paper online via where you will alo find detailed author guideline. Ground Improvement 13 Iue GI On ettlement of tone olumn foundation by Priebe method Ellouze et al. 107