EFFECTS OF INCLINED CUTOFFS AND SOIL FOUNDATION CHARACTERISTICS ON SEEPAGE BENEATH HYDRAULIC STRUCTURES

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1 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 597 EFFECTS OF INCLINED CUTOFFS AND SOIL FOUNDATION CHARACTERISTICS ON SEEPAGE BENEATH HYDRAULIC STRUCTURES Kald Fadl Alsnous and Hasan G. Moamd Dpartmnt of Cvl Engnrng, Unvrsty of Garyouns, Lbya ABSTRACT If a dam s foundd on a prvous foundaton, t dffrntal ad formd by t dam acts on t foundaton and gnrats undr spag. T spng flow gnrats rosv forcs wc tnd to pull sol partcls wt t flow. Ts causs t formaton of rrgular passags lk pps wc mov bnat t dam. Ts procss s known as ppng pnomnon. Ppng occurs f t t ydraulc gradnt at t downstram pont approacs t crtcal ydraulc gradnt. In ordr to prvnt ppng, t s ncssary to rduc t vlocty of t spng watr to a saf valu. Ts can b accomplsd by lngtnng t spag pat. On of t mtods of suc a lngtnng s to ntroduc st pls or cutoff walls wtn t dam foundaton. Usng dffrnt soluton mtods, suc as t conformal analyss, mprcal formulas, lctrcal analog modls, prmntal works usng pyscal as wll as numrcal modls and t flow nt tcnqu many rsarcrs ad amnd t confnd spag troug prvous sols bnat ydraulc structurs and studd tr safty aganst ppng pnomnon. Estmaton of t t gradnt, uplft prssur, and flow rat wr provdd for varous problms ncludng cass of flat bottom dams wt on or mor mbddd vrtcal st pls. Howvr, lmtd ltratur s avalabl concrnng t us of nclnd walls or st pls. Morovr, most of ts solutons wr basd on t assumpton of a omognous and sotropc foundaton sol avng an nfnt dpt. Suc an assumpton s usually not mt dpndng on varous n stu condtons tat possss ansotropy, trognty, lmtd sol dpt,... tc. It appars tat no soluton s avalabl n t rady accssbl ltratur to dtrmn t ffct of usng a flat dam bas wt tr to or l st pl(s) on spag flow troug trognous and ansotropc sols of lmtd dpts. Ts problm s solvd usng t fnt lmnt mtod. A modl was prpard to comput t pomtrc ad dstrbuton for dffrnt flow condtons and sol caractrstcs. T calculatd t gradnt valus, flow rats, and uplft prssur wr sown to b affctd by cangng t slop angl of t st pl and varyng t sol and flow condtons. Kywords: Dam; nclnd cut-off; fnt lmnt; ppng; spag

2 598 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt INTRODUCTION Spng watr troug a prmabl sol undr dams rts uplft prssurs and may carry sol partcls wt t wc lads to ppng. Ts may rsult n sttlmnt n t dam bas and as t potntal to caus falur of dams. Trfor, dams foundd on prmabl sol av to b dsgnd aganst uplft and ppng, also t spag losss as to b mnmd. If t t gradnt at t downstram sd, I, approacs t crtcal ydraulc gradnt, I cr, tn ppng orgnats n t sol. Trag and Pck γ sub (967) dfnd I cr as I cr. Cutoffs, lk st pls or concrt curtans, can b γ w provdd to rduc bot uplft prssur and t gradnt. If t cutoff s nclnd toward downstram sd, bot t gradnt and uplft prssur dcras, ts s concludd by Abbas (994) and Moamd and Agraloglu (25). LITERATURE REVIEW Solutons for varous problms of spag undr dams wt mbddd vrtcal st pls and a flat bottom dam wt on or mor vrtcal st pls wr gvn usng dffrnt approacs by Kosla (936), Harr (962), Llavsky (965), Trag and Pck (967), Ruston and Rdsaw (978), Grffts and Fnton n (993) and otrs. Howvr, lmtd ltratur s avalabl for spag troug prvous mdum bnat dams wt nclnd st pls. Vrgn (94) analyd spag flow around an nclnd st pl mbddd n a porous mdum of nfnt dpt. Polubarnova Kocna (962) gav t ydrodynamcal flownt for an nclnd cutoff n a porous mdum of nfnt dpt. Abbas (994) usd conformal transformaton and gav a soluton for spag flow bnat a flat bottom dam wt an nclnd st pl at ts to on a omognous and sotropc sol of nfnt dpt. Moamd and Agraloglu (25) usd a two dmnsonal fnt dffrnc modl to analy stady stat spag flow bnat a flat bottom dam wt an nclnd st pl at ts to on a omognous and ansotropc sol. Howvr, t appars tat no soluton was avalabl n t radly accssbl ltratur to dtrmn t ffct of usng an nclnd cutoff at t downstram nd of a dam on spag flow undr unstady flow on non-omognous and ansotropc sol. Suc soluton as bn obtand n ts prsnt study usng numrcal tcnqus. OBJECTIVE In ts prsnt study, t obctv s to dvlop a two dmnsonal fnt lmnt modl to analy spag flow bnat a dam wt an nclnd st pl undr stady or unstady flow condtons on omognous or non-omognous sol and sotropc or ansotropc spag flow. Fgur sows a scmatc rprsntaton of ts study.

3 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 599 H Nonomognous ansotropc sol Inclnd st pl Imprvous boundary Fg. Gnral dscrpton of t problm FORMULATION OF THE PROBLEM Govrnng Equaton T groundwatr confnd transnt flow quaton for two dmnsonal cas can b prssd by t followng lnar partal dffrntal quaton ( K ) + ( K ) s () t n wc: s t pomtrc ad, K & K ar t prmablts n t orontal and vrtcal drctons, rspctvly, s s t storag coffcnt, t s t tm. Soluton of Equaton () rprsnts tm and spac dstrbutons of pomtrc ad n non-omognous, ansotropc mdum wt confnd transnt flow. Matmatcal Formulaton T fnt lmnt mtod s usd r to solv Equaton (). Usng Galrkn's mtod, w sk an appromat soluton ovr ac fnt lmnt of t doman Ω and t boundary Γ. T polynomal appromaton of t soluton s of t form: wr n (,, ( (, ) (2) ar t valus of t soluton at t nods and ar t appromaton functons ovr t fnt lmnt wt n as t numbr of nods. T wak form of Equaton () s drvd, t can b prssd as:

4 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 6 Γ Ω + + ds wq dd t ws K w K w n ] ) ( ) ( [ (3) Wr q n s t dscarg and w s known as t wgt functon, t can b prssd as ), ( w (4) K and K ar assumd to b constant wtn on fnt lmnt (Pndr, 964). Substtut Equaton (2) for on fnt lmnt and Equaton (4) n Equaton (3) ylds: Γ Ω + + ds q dd t s K K n n n n )] ( ) ( ) ( [ (5) T prvous prsson can b prssd n a matr form as follows: [ ]{ } [ ] { } Q t G C + (6) Wr [C ] s t conductanc matr, [G ] s t storag matr and {Q } s t dscarg vctor. dd K K C ] [ + Ω (7) Ω dd s G (8) Γ ds q Q n (9) Lnar trangular fnt lmnt (tr nods lmn s usd r. T ntgrals n t abov quatons ar valuatd usng t natural coordnats L, L 2 and L 3. In summary, ty can b prssd as: ) ( 4 K K A C γ γ β β + () 6 S A G ()

5 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 6 A s G (2) 2 Wr A s t ara of t fnt lmnt β γ k ( k ) ( k) (3) Q can b st quals to ro for all nods bcaus of t followng: - Q for no flow boundars. - Q for ntror nods. - Q s rrlvant for nods on spcfd ad boundars. T fnt lmnt ms sown n Fgur 2 s usd. T total numbr of lmnts and tr gomtry ar not constant. Ty dpnd on t gomtry of t study ara (dam bas, st pl lngt, angl of nclnaton, tc.). Howvr, ms gnraton s don automatcally by t prpard computr program. Aftr assmbly of t fnt lmnts, Equaton (6) bcoms: [ C ]{ } + [ G] { Q} (4) t Elmnt No Fg. 2 Fnt lmnt ms

6 62 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt From Taylor srs, t drvatv t can b appromatd as follows: t t+ t t t (5) Trfor, t vctor t can b prssd as: t t+ t t ({ } t { } ) (6) In ordr to obtan stabl soluton for Equaton (4), an mplct numrcal tcnqu s usd; wc s t backward dffrnc mtod. T soluton of Equaton (4) aftr t tm bcoms: { } t+ t t t [ C] + [ G] { Q} + [ G]{ } t (7) Usng t matrcs soluton, Equaton (7) s solvd at ac tm stp. Intal and Boundary Condtons Consdr t cas as sown n Fgur (3). T boundary condtons ar as follows: (,, TL on bc (, DP + FD, BS + USL TL on d ds ( USL + BS,, (, DP, DP DP + FD on f USL + XS USL + BS on fg / ( / SK, 2, / SL on g / ( / SK, 2, / SL on

7 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 63 USL u DSL ub Z a u2 FD k BS X XS g f SL H Xt ds d SK DP b TL c X Fg. 3 Scmatc sktc for t proposd modl sowng t boundary condtons

8 64 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt (, DP, ( USL, Z, USL USL + XS on DP Z DP + FD on k For t boundary ak, f t upstram watr lvl s constant at lvl u, tn + USL on ak (, DP FD, u For t boundars ab and cd, ty ar ntr constant ad nor mprvous boundars. Trfor, t ffcts of coosng tr typ on t modl rsults av to b nvstgatd. If ty ar consdrd as constant ad boundars, ty wll av t form: Z DP + FD on ab (, Z, u ( TL, Z, Z DP + FD on cd ds Altrnatvly, f ty ar consdrd as mprvous boundars, ty wll b prssd as: (, Z, ( TL, Z, Z DP + FD on ab Z DP + FD on cd Two cass ar consdrd for t ntal condton: Cas I: Constant watr lvl at t upstram sd T ntal condton s as follows: (,,) ds Cas II: Varabl watr lvl at t upstram sd As sown n Fgur 3, consdr tat u, u2 as t ntal and fnal watr lvls at t upstram sd and ub s a watr lvl btwn u and u2. It s rqurd to analy t spag flow at lvl ub. T frst stp s to apply t sam ntal condton as n cas I wt boundary condton on ak as follows: + USL (, DP FD, u

9 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 65 In t scond stp, wn stady stat s racd, t ad valus of pomtrc ad obtand n t frst stp ar consdrd as ntal condton and t followng boundary condton wll b appld on ak: + USL (, DP FD, u2 Hr n cas II ub s a spcfc watr lvl occurs durng t tm TFE (Tm rqurd to fll or mpty t rsrvor). Assumng constant rat to fll or mpty t rsrvor, tn ub can b prssd as: + n cas of fllng t rsrvor, and ub ub ( u 2 u) SPT / TFE u + n cas of mptyng t rsrvor ( u u 2) ( TFE SPT )/ TFE u 2 Wr SPT s t tm at wc ub occurs. Foundaton Sol Tr cass of t foundaton sol ar consdrd n ts study, - Homognous and sotropc. - Homognous and ansotropc. - Block ws omognous. Slcton of K, K and S dpnds on t typ of t foundaton sol. MODEL APPLICATION AND RESULTS T computr program was wrttn n COMPAQ VISUAL FORTRAN 6.. T output ncludd t uplft ad, t t gradnt and t spag quantty bnd t dam. Any rqurd gomtry of t cas can b analyd as follows: - Angl of nclnaton of t st pl 8. - St pl locaton XS BS (XS at l, XS BS at to). - Dam bas s dprssd ( FD ) or on ground ( FD ). - T cas wt or wtout st pl ( SL or SL ). - Otr dmnsons BS, DP, USL and DSL can b nputtd n t modl as rqurd. T modl can analy stady or unstady spag flow. For t foundaton sol, any of t tr cass prsntd can b slctd. T t gradnt can b obtand as follows: I d ds (8) Wr ar t valus of t pomtrc ad at nods vrtcally blow t t nods, and d ar t vrtcal dstancs as sown n Fgur 4.

10 66 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt Dam ds d Fg. 4 Scmatc sktc for computaton of t gradnt Dffrnt cass ar slctd and analyd usng t modl. T followng rprsnts som of ts cass undr stady stat spag flow BS Xt SL Et gradnt.2.8 Wtout st pl Xt / Bs Fg. 5 Varaton of t gradnt for dffrnt valus of

11 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 67 As sown n Fg. 5, wn t st pl s at t to, g valus for t gradnt ar dvlopd f t st pl s nclnd towards t upstram sd ( s lss tan 9 ), also bot of t uplft ad and t spag bnd t dam ar gratr tan tos of vrtcal st pl (Fg. 7 and Fg. 8). On t otr and, t t gradnt dcrass as ncrass towards t downstram ( 9 Fg. 6) for a dstanc Xt / SL.75.8 byond t to, tn t t gradnt starts ncrasng slgtly wt ncrasng. It s also clar tat t mamum t gradnt dcrass for 2 o and starts ncrasng for 35. From Fg. 7, t uplft ad dcrass as ncrass. From Fg. 8, t mnmum spag quantty bnd t dam s at appromatly quals to 2. I. SL / H Xt / SL Fg. 6 Varaton of t gradnt for dffrnt valus of ( 9 o ) Uplft ad / H SL X / BS Wtout st pl Fg. 7 Varaton of uplft ad along t dam bas for dffrnt valus of

12 68 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt.2 Q / ( K. H ) Angl of st pl (dgr) Fg. 8 Varaton of spag bnd t dam for dffrnt valus of For Fgurs (5, 6, 7 and 8) SL XS BS, ds FD, K K From Fg. 9, wn t st pl s at t l, g valus for t gradnt ar dvlopd f t st pl nclnd towards t upstram sd ( s lss tan 9 ), also t uplft ad s gratr tan tat of vrtcal st pl (Fg. ). T t gradnt dcrass as ncrass towards t downstram ( 9 ) untl appromatly quals to 2, tn t t gradnt starts ncrasng wt ncrasng From Fg., t mnmum spag quantty bnd t dam s at appromatly quals to I. SL / H Xt / SL Fg. 9 Varaton of t gradnt for dffrnt valus of

13 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 69 Uplft ad / H X / BS Fg. Varaton of uplft ad along t dam bas for dffrnt valus of.2 Q / ( K. H ) Angl of st pl (dgr) Fg. Varaton of spag bnd t dam for dffrnt valus of For Fgurs (9, and ) SL BS, ds FD XS, K K From Fg. 2, wn t st pl was at t md dstanc of t dam bas, g valus for t gradnt wr dvlopd f t st pl nclnd towards t upstram sd ( s lss tan 9 ), also bot of t uplft ad and t spag bnd t dam wr gratr tan tos of vrtcal st pl (Fg. 3 and Fg. 4). T t gradnt nar t to dcrass as ncrass towards t downstram ( 9 ) untl appromatly quals to 2, tn t mamum t gradnt starts ncrasng wt ncrasng. From Fg. 4, t mnmum spag quantty bnd t dam s at appromatly quals to 9.

14 6 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt I. SL / H Xt / SL Fg. 2 Varaton of t gradnt for dffrnt valus of Uplft ad / H X / BS Fg. 3 Varaton of uplft ad along t dam bas for dffrnt valus of.9.88 Q / ( K. H ) Angl of st pl (dgr) Fg. 4 Varaton of spag bnd t dam for dffrnt valus of For Fgurs (2, 3 and 4) SL BS, ds FD, XS BS/2, K K

15 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 6 T ffct of ansotropy s clarly ndcatd n Fgurs 5, 6, and 7. Et gradnt, uplft ad and spag ncras as t ansotropy rato (K / K ) ncrass K/K K/K 5 K/K I. SL / H Xt / SL Fg. 5 Effct of ansotropy rato (K / K ) on t gradnt. Uplft ad / H K/K K/K 5 K/K X / BS Fg. 6 Effct of ansotropy rato (K / K ) on uplft ad

16 62 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt Q / ( K. H ) K / K Fg. 7 Effct of ansotropy rato (K / K ) on spag bnd dam For Fgurs (5, 6 and 7) SL BS XS, ds FD, 2 o For a trognous foundaton sol, t varaton of t gradnt dos not follow a gnral trnd. Accordng to t spcfcatons of t foundaton sol, ac cas as to b analyd and dscrbd ndvdually. For t cas sown n Fgur 8, four sol layrs ar ntrd to t modl wt spcfcatons as n Tabl. Tabl Dtals of t sol layrs usd n t modl Layr No Layr tcknss. (m) K (m/day) K (m/day).4.2. I. SL / H Xt / SL Fg. 8 Varaton of t gradnt for dffrnt valus of wt trognous sol For Fgur 8, SL BS XS, ds, FD BS/, 2 o

17 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 63 T followng cass rprsnt som rsults undr unstady stat spag flow:.25 T Days.2 T5 Days T Days T5 Days Stady Stat I. SL / H Xt / SL Fg. 9 Varaton of t gradnt (unstady flow, constant upstram ad) Uplft ad / H T Days T5 Days T Days T5 Days Stady Stat X / BS Fg. 2 Varaton of uplft ad along (unstady flow, constant upstram ad) Q / ( K. H ) Tm (day) Fg. 2 Varaton of spag bnd t dam (unstady flow, constant upstram ad)

18 64 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt.25 H / BS.2 H / BS.67 H / BS.5 H / BS.33 I. SL / H.5. H / BS Xt / SL Fg. 22 Varaton of t gradnt (unstady flow, varabl upstram ad).2 H / BS H / BS.67 H / BS.5 Uplft ad / H H / BS.33 H / BS X / BS Fg. 23 Varaton of uplft ad (unstady flow, varabl upstram ad) Q / ( K. BS ) H / BS Fg. 24 Varaton of spag bnd t dam (unstady flow, constant upstram ad) For Fgurs (9-24), SL BS XS, ds FD, 2 o, K K

19 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 65 Rlablty of t Modl T valdty of t prsnt numrcal modl was vrfd by comparng ts rsults wt t analytcal soluton gvn by Abbas (994), and t fnt dffrnc soluton gvn by Moamd and Agraloglu (25), also t comparson s don wt t flow nt mtod. A clos agrmnt s racd as follows: - T dffrnc n spag computaton bnd t dam usng t flow nt mtod and t prsnt modl s about 7.5 %. - For t t gradnt and t uplft ad, Fgurs 25 and 26 sow t comparsons of t prsnt modl wt prvous studs I. SL / H.5..5 Fnt lmnt soluton Fnt dffrnc soluton Analytcal soluton Xt / SL Fg. 25 Comparson of t gradnt obtand by prsnt modl wt prvous studs / H Fnt lmnt soluton.3 Fnt dffrnc soluton Analytcal soluton Angl of st pl (dgr) Fg. 26 Comparson of uplft ad varaton at pont () (S Fg. 3) obtand by prsnt modl wt prvous studs For Fgurs (25 and 26), SL BS XS, ds FD, 2, K K

20 66 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt CONCLUSIONS On t bass of fnt lmnt appromatons, a two-dmnsonal numrcal modl was dvlopd to solv t govrnng quatons of groundwatr spag undr ydraulc structurs. T goal was to study t ffct of nclnd cutoffs, prmablty rato, and foundaton sol dpt on t gradnt, uplft prssur and flow rat. T modl calculatd t pomtrc ad at all nodal ponts n t problm soluton doman for stady and unstady flow condtons. Usng ts ad valus, t t gradnt, uplft prssur and flow rat wr dtrmnd. T modl rsults ndcatd tat t fnt lmnt tcnqu gav comparabl valus for smlar cass solvd wt otr soluton mtods and offr a mor gnral approac tat prmts t usag of t dsrd prmablty, foundaton sol dpt, and flow typ. From t modl rsults, t followng rmarks can b concludd: - T t gradnt, aftr a dstanc Xt / SL. 85 downstram from t dam to, dcrass wt ncrasng t st pl nclnaton and t rducton ncrass as ncrass. T rsult s an ncras n t safty factor aganst ppng pnomnon. 2- Usng an nclnd st pl towards t downstram sd wt lss tan 2 s bnfcal n ncrasng suc a safty factor. On t otr and, t dangr from undrmnng wll b sftd furtr downstram from t to of t structur. 3- Placng t st pl at t dam l s not rcommndd undr any angl of nclnaton. T sam concluson was also vald for t cas of to stng nclnd towards t upstram sd. Dong so producs a sngularty at t nd of t dam wt a matmatcally nfnt vlocty. Ts wll produc unstabl sol condton n clos promty to t to. 4- Complt analyss for varous cass was consdrd n ordr to ascrtan t optmum locaton and t optmum angl of nclnaton of t st pl. Howvr, as prlmnary conclusons, f t t gradnt and t spag bnd t dam ar consdrd as t maor factors n t dsgn of t dam, t optmum locaton of t st pl s at t to of t dam wt nclnaton angl quals to 2. Wl f t uplft ad s consdrd as t maor factor, t optmum locaton of t st pl s at t l of t dam wt nclnaton angl quals to 2. Ts conclusons old wn t sol bnat t dam s omognous. Howvr, f t s non-omognous, ac partcular cas as ts own optmum crtra. REFERENCES Abbas, Z. I., 994. Conformal analyss of spag blow a ydraulc structur wt an nclnd cutoff. Intrnatonal Journal for Numrcal and Analytcal Mtods n Gomcancs, Vol. 8, pp

21 Twlft Intrnatonal Watr Tcnology Confrnc, IWTC2 28, Alandra, Egypt 67 Grffts, D. V. and Fnton, G. A., 993. Spag bnat watr rtanng structurs foundd on spatally random sol. Gotcncal and Gonvronmntal Engnrng, ASCE, Vol. 43, pp Harr, M. E., 962. Groundwatr and Spag, McGraw-Hll, Nw York. Kosla, A. N., Bos, N. K., and Taylor, E. M., 936. Dsgn of wrs on prmabl foundatons, Publcaton No. 2, Cntral Board of Irrgaton, Inda. Llavsky, S., 965. Dsgn Tt Books n Cvl Engnrng: Vol. III: Dsgn of Dams for Prcolaton and Eroson, Capman and Hall Ltd., London. Moamd, H. G., and Agraloglu, N., 25. Journal of Istanbul Tcncal Unvrsty of Engnrng, Vol. 4, pp Pndr, G. F., and Gray, W. G., 977. Fnt lmnt smulaton n surfac and subsurfac ydrology. Acadmc Prss, Inc., Nw York. Polubarnova-Kocna, P. YA., 962. Tory of ground watr movmnt. Prncton Unvrsty Prss, Prncton, NJ. Ruston, K. R. v Rdsaw, S. C., 978. Spag and groundwatr flow, Jon Wly and Sons, Nw York. Trag, K., and Pck, R. B., 967. Sol mcancs n ngnrng practc. Jon Wly and Sons, Nw York. Vrgn, N. N., 94. Spag undr dam foundatons wt nclnd scrns and cutoffs, Journal of Hydraulc Constructon, 2.