Design of Merensky Reef crush pillars

Sy by B.. W*, J.S. Kuj, d.r. Sy h Buhvld lum gu ml d w d, hllw-dg fm bul bd whh k f my hudd f klm. Mg xv, wh dh gg fm l--uf 2 300 m. h mg mhd v f l g. ll wdly mlyd u h. I h d lvl, - ll qud fl bl m f bg u, d h dul ll gh ud blz h hggwll. h ll mmly kw uh ll. Ll wk h b d h dm ll k d dul gh, d ll hv b dgd ug x d fmul dvld f h hd-k m. h h ld v d udz ll wh qul l f, ll bu d l ll. h db uh ll dg mhdlgy, d vd dg h. h mg vm w d h vg, whh ludd udgud d lby mum, lyl lu, uml mdl d bk ly. h ul f h udy ubl f h wh h h w d u, d my l b ld wh u h ml vm. Kywd Cuh ll dg, k ll gh, dul ll gh, u mum, dg h. Idu h Buhvld Cmlx lg lyd gu u whh bu 350 km fm w. I ud h h f Suh Af (Fgu 1). h lum gu ml d w l bd kw h Mky Rf, mlzd gmdl yx 0.7 m 1.4 m hk, d, udlyg h, h UG2 Rf mg m hm m f ml hk. h glly d 8 15 wd h f h mlx. h hzl vl (k ) v fm bu 0.5 v 2.5. h dh f mg g fm u 2 300 m. If uffly lg mg hvd, h bu glgl fu, lg vlum f hggwll k bm ubl, ulg ll, llqully, bkbk 1. I d v h bkbk hgh u ym qud. h uvlly hvd by h u f mll h ll d h k f b mg (Fgu 2) d f u dw-d mg. I h, ll h Mky d UG2 f hv b dgd ug x d k gh fmul dvd f h hd-k m. h qu f h u mhdlgy u vz ll, whh lw h x. I dd, ll u h d lvl qud fl bl m f bg u. h ll kw uh ll d h dul gh vd h qud u v bkbk d k h hggwll bl. A f ll bu, wh u qu, h d qu bu h dg f h ll. h m bjv uh ll dg u h h dul gh f h uh ll uff bkbk. ll z huld hf b dgd wh h dul gh md. Hwv, h ll bu hw h h k gh d ldg vm l d b dd h dg. I h Buhvld lum m, h dul gh 1 M h (Rb l.2). h hvd f h dul gh f ll bw 8 M d 13 M d h ll l d 30 m. * Gldfld Ld d Uvy f h Wwd, Jhbug, Suh Af. CSIR, Jhbug, Suh Af. Uvy f h Wwd, Jhbug, Suh Af. h Suh Af Iu f Mg d Mllugy, 2010. SA ISSN 0038 223X/3.00 + 0.00. vd Jul. 2010; vd vd S. 2010. h Jul f h Suh Af Iu f Mg d Mllugy VOLUME 110 REFEREED AER OCOBER 2010 581

Fgu 1 h x f h Buhvld lum xu h Iml lum M. h fmul, Equ [1], hw l lh bw ll z d k gh. [1] wh: h u f h flu f gully u dj d f h ll. h flu w dmd by Rb l.7: [2] Fgu 2 l vw f yl f h lum bd w d h h ll wdh d mg hgh, vly, d L f h ll lgh. Mky ll bhvu, ludg k d dul gh, w mud x ll f vbl z fm h dff m. h ul f h mum dud dl W4, d h k gh md Equ [1] Fgu 3. A gd f w hw by ll h md ll x by h w hghlghd ll fm h hbzmb, whh udmd by h fmul. Igly h b l fud dmg h h h h m f h h dbd h vd uh ll dg mhdlgy, bd ld k mh d bkd by udgud d lby mum. h vg w dud h Mky Rf h Iml lum M, d h hbzmb d Kudf. hf h ul dbd h lbl h Mky Rf, bu h my b ud y uh ll dg. I mmdd h mum f ldg ff d ll gh b md f h vm. k ll gh A ml fmul f dmg k ll gh f Mky ll w dmd by W l.3 f ll Fgu 3 Cm bw h fmul d mum f k ll gh 582 OCOBER 2010 VOLUME 110 REFEREED AER h Jul f h Suh Af Iu f Mg d Mllugy

h. h glly gd l f h mud d wh h fmul gh h lbly f h l W l.3 qu h lul f k ll gh, ully h Iml d h Kudf. ll h ly dgd huld fl bly h f wh h ldg vm ff. Hwv, ll h lg my fl vl m, wy fm h f wh h ldg d f. h ll bu w vgd vd m gh bl d ubl ldg ff f Mky ll. All h ll bu ud h f d fully fmd ll bk fm h lggg f. h ll d w hu g h 10 m bk fm h lggg f, hw Fgu 4. O f h bu d mgud 1.2 m v, ulg vl j f k hw Fgu 5. h ll w ld bw 10 m d 14 m bhd h lggg f h m f h bu (Fgu 4). A hgh dg f fgm w bvd hughu h ll d k fgm w hw h ASG. M f h umd ll fld l wh, ju bhd, h lggg f. Oly w ll fld ub bu 4 m 5 m bhd h f, hw Fgu 6. ll 0 fld m-bl m bu 7 m bhd h lggg f (Fgu 7). A ll h ll fld bly wh ly m j f k fm f h ll, ldg d 5 m 7 m fm h lggg f ff ugh. Hwv, vd fm h ll bu ugg h ufld ll ld 10 m m fm h f dgu, f-ldg u d my bu f flu k l. Fm h vd f h fw ll fd bv, uudg ff f bl d ubl ldg d hv b dmd fm l mdllg (Fgu 8). h l bl dfm h fgu bd h vg dfm h f h ll f dv f 4 m (Fgu 6). h udgud l Fgu 8 f dfm mum whh lly b dud Fgu 5 m vw hwg h u-d d f bu ll. N h gully full f k fgm fm h ll bu Hghly d, ld ub Cuh ll (4 m 5 m lg) Dw-d l f S ff F dv Fgu 6 l vw hwg h f wh w f h md ll fld ( dw l) Fgu 7 Skh hwg h fug h ud wh 0 fld h Jul f h Suh Af Iu f Mg d Mllugy Fgu 8 Abl d ubl ff f h uudg f bl uh ll dg. El = vg dfm v ll, udgud = dfm mud dj ll VOLUME 110 REFEREED AER OCOBER 2010 583 Fgu 4 l vw hwg h f wh h vgd ll bu ud ( dw l)

udgud. h mum huld b dud bu 2 m h dw-d d f h ll dg d bu h md- f h ll. I h mdl, h uudg ll w umd hv dul gh f 20 M. h ubl ldg d f h m h bl mdl bu f d wh h ll fl 8 m 10 m bhd h f. M f h mud ll ld-dfm uv w lm lll h l bl l. N f h umd ll hd dfm f 32 mm dug h l flu d ll fld bly bl m. h ubl ff f h uudg bu 5.0 mm/gn. M f h mud ll fld ud ldg d wh h ff f h uudg w bu 3.2 mm/gn Rdul ll gh h dul gh f ll w dmd ug fld d -hg mum dud lvly hgh (4 m 6 m) bv h ll. h mum w fmd by f fld mum dud gul vl ju bv h ll. h ll fl d vg ll (AS ) w xld fm h f mum ug v mx f Buq qu: wh: σ zz = A = A f h gd z = Vl d by h gd. A l vw f yl Buq -d ym ud h budy f ll hw Fgu 9. h gd bld mull b dd h ll. [3] h ul. h k gh f h lby (Fgu 10) w ml h gh vdd by h l k gh fmul. h lly hgh f f k gh wh w/h Fgu 10 w l hw by FLAC7 mdllg (W l.3). Hwv, h w d h f gh h hgh w/h h lby, dg ll uhg (umg: h uh; fud; d fm vdd h fud by h ml g w h m ll h ). h ul f h ll dul gh mum ld wh h S d Yk5 lby Fgu 11. A lw w/h h w gd gm bw h udgud mum d h lby ul. Hwv, lg w/h h dy w g. h bv wll b dud fuh. Alyl ly f dul gh If umd h ll f mll vl l h ubjd ufm, bl b lm qulbum lu f fly l ml 1 m 5 m Lby Lby w dud by S d Yk5, ug yldl uh ll f 25 mm dm d fud yld f 80 mm f bh h dm d h lgh. h fud w fd by ml g. Bh h uh d h fud w h fm h mmd Mky Rf fwll Iml lum. h ml yl f h lw hlf f h ll d mmd fwll f h Mky Rf h m. h w/h f h uh w vd by hgg h uh hgh. h budy d h f h uh l h ffv w/h. Shuld h f bw h uh d h ml l hv b fl, h w/h wuld hv b hlvd h f x f ymmy (b f h ). S h f hd f gl f bu 12 (Yk d Cbul6), uld h b gdd l f ymmy ugh f ml h bw h uh d h fud. h u w/h wll hf b g h 50% f h ul w/h f h uh, bu h ffv b qufd wh y y. h u w dd dug h ly f Fgu 9 l vw f h gd lyu ll f Buq vlu. h g h f h bm (dw-d dg) Fgu 10 Rul f lby uh (f S d Yk 5 ) 584 OCOBER 2010 VOLUME 110 REFEREED AER h Jul f h Suh Af Iu f Mg d Mllugy

Fgu 11 Rdul gh ul h yldg. Adg B8, h vl dbu hugh ll, g f uh ml, b xd : wh: S yy = Vl wh h ll φ b = Il f gl f h bk k UCS b = Uxl mv gh f h uhd (bk) ml x = Hzl d h ll h = ll hlf hgh. Fgu 12 llu h ll gmy, wll h g vl l. h ll wdh d hgh qul 2w d 2h vly. Equ [4] hw h h dul gh f ll wh gv w/h dd h uxl gh (UCS b ) d l f gl (Φ b ) f h bk k. Aumg Φ b, h ll dul gh wuld b dly ld h UCS b. h UCS b, u, dd h dul h (C b ) d h Φ b (Mh- Culmb ): [4] [5] ugg xl vl h dg f h ll. Hwv, lm l w glly ld fm h mum (Fgu 13). Equ [4] w gd b h AS : Ug h m m dmd f h uv Fgu 13, Equ [6] w ld g w/h d md h dul gh mud udgud (Fgu 14). h dul gh mud lby by S d Yk5 h uh, l ludd h fgu. h lu h vdd bl f 1 Fgu 13 (C b = 0.2 M) d f h lby d d vm dul gh w/h xdg bu 3. h lu f C b = 0.011 M udm h dul gh v mvly hgh w/h d d m wh h h udgud lby ul. Hwv, bh h B8 lu d h lby ul hw xl dul gh wh w/h. h x h lh hw by h lby Fgu 14, ugg f gl f Φ b = 30. Slm9 dvd lvly mld x db h dbu l ll, h llw f -ufm dbu h vl l (Equ [7]). h qu m l h h B8 lu. [6] hf, h dul h xmly lv h bhvu f fld ll. I dd, y hzl ld h ll dg,.g. u, h ml ff. h dul h b hugh f fl ff du gvy, whh ld mll vlu h k g. h my l b ddl dul gh d wh lkg f ugh fu uf. A quvl dul h (C b ) f 0.011 M w md fm h ff f gvy l f k h dg f ll. Aumg UCS b = 0.038 M, whh l C b = 0.011 M, d Φ b = 30, h B8 ll w ld fu f d h ll d hw Fgu 13. h ul w l md h mud vl fl f ll mud h hbzmb, 1 h fgu. h lyl lu vdd muh mll fl h 1 d w y h UCS b 0.7 M vd mbl fl (Fgu 13). Aumg Φ b = 30, C b f 0.2 M w luld fm Equ [5]. h lyl lu Fgu 12 Gmy f h ll umd Equ [4] Fgu 13 Cm bw h B 8 fmul d h 1 fl. Aumg Φb = 30 h fmul. 2.5 m-wd ll g wdh f 1.1 m h Jul f h Suh Af Iu f Mg d Mllugy VOLUME 110 REFEREED AER OCOBER 2010 585

lud wh vy mll g f w/h. hf, h ubly f h qu f dbg h ll dul gh h my b qubl. h Slm9 qu f dbu h f ll (h) w ld, umg φb = 30 d h f 1.6 M Equ [8]. [8] Fgu 14 ll w/h -ghg ff AS. h B 8 lu f Φb = 30 md h mum d h S d Yk 5 lby [7] h uv f h f 0.011 d 1.6 ld Fgu 15. F ml h lby dul gh (S d Yk5) l ludd h fgu. I huld b mhzd h h dff bw lby d lyl lu. F, h lyl lu bd h lm qulbum f h ml h ldd bw w ld l;, h uh llw f dmg h fud. h fud dmg hv u ml f k ll gh h b dmd W l.3. I vy lubl h dul gh l ffd by fud dmg. I dd, h fmul bd l d, wh h lby w xyml. h gm ff wll l ul dff lh bw w/h d gh. D h dff, m w md mh h lby ul wh h Slm9 lyl mdl (Equ [7]). S h Slm9 qu d u f fud dmg, h vm f h ud h f h ll. hu h AS my l b vmd. h wuld b ully u f lg w/h. I l b gud h h w/h f h lby m w ffd by h budy d, lly h f bw h l l d h mll k d. h lmd f lg h f wuld u d h ffv w/h f h d bu f dud lmg ff. If umd h h d uld b muh 25%, h m f h Slm9 qu (Equ [7]) d b djud. A vy ly hwd h h f gl d h dul h uld vy bw 25 d 31 d 0.7 M d 1.6 M, vly, mh h lby ul wh h qu. h Slm9 uv wh dul h f 1.6 M (Fgu 15) fd h udgud mum fm h hbzmb d Kudf wll h lby (S d Yk5). Hwv, h udgud d h lyl lu w md h fl dmd f 1 Fgu 16. I huld b d h h h B8 h Slm9 qu d h ff f h fud ll bhvu;.. h fud dd b l d h f f bw h ll d h ldg l umd b qul h l f f h ml. hu h qu d qu ll bhvu, whh w bvd udgud. I h lyl lu, hgh w/h wuld b d wh vl h byd h uhg f h fud (hggwll fwll). h xl why h lg ll w/h my b wll d by h lyl lu hw Fgu 15. Fgu 15 ll w/h -ghg ff AS. h mum md h B 8 d Slm 9 lu (Φb = 30 ), d h S d Yk 5 lby Fgu 16 Cm bw h Slm 9 fmul (Equ [8]), umg Φb = 30 d C = 1.6, d h mud 1 fl 586 OCOBER 2010 VOLUME 110 REFEREED AER h Jul f h Suh Af Iu f Mg d Mllugy

Fl mdllg A f FLAC7 mdl w ud vg ll bhvu h x f l ldg vm. h vm ludd h ll fud h uld u dmg. F h u f h mdl, h fud ml w umd b h m h ll, whh w bl xm f h ll ll h. h mdl ludd h ll lf d h mmd hgg- d fwll. O m m h dd b dd f ll bhvu w ml bl. I h mdl, bl dfd h f d f flu. I h mdl, flu bhvu lld by h l. hf, d l bw h fg ( fg) d ml bl b qufd. h l f gl d h dl gl w vd h mdl vd ddl ml. I h uml mdl bl ufuly l ffd by gd z, flu flu llz. hf h mdl bl lld by bh h flu fg d h gd z. h u w dd h mdl ly. Whl bl d ff h gh f yl ld uxl d xl m, bm vy lv (ll) gm wh lg w/h. I h lg w/h gm, flu g fm h dg wd h f h ll v bf h k ll gh hd. I h f mvly bl ml, h fld ml wll dly l gh d flu g lvly ly h ll. Flu d k gh wll b f ml mgud. Hwv, m dul ml wll m m gh f flu d flu g h ll wll b dd. h f h ll wll b fd by h lly fld ml d bl u hgh ld. A qu h mgud f flu wll b muh lw h h k gh. Fgu 17 hw h Mh-Culmb m h w ud h mdl. h m w lbd fm udgud mum f ll d d lby ul. Budy d ly m l h uhg mhm, hy ff hzl fm. I h mdl (Fgu 18), h vl bud w llwd mv hzl d (hu mulg fully ld f ll). h f du uh bddg l, ful d j huld l ff h uh, bu h w vgd h mdl. Whl h uml mdl vd gh h flu mhm, mu b mhzd h h mdl lwy d b lbd g l d. Mh dy d f fg m m h d hy b bly ld. h mdl w ud vlu h k ll gh fmul dvd fm h bk-ly. h w bu fv m h ll wdh (x ~ 83%) d h mdl hgh w m h gh m h ll wdh. h mdl ul md h k ll gh fmul d h k gh f h S d Yk5 lby Fgu 19. h gh hw h fgu w lghly hgh h mud h um, du h 2D d umd h mdl. h 2D d w ud f by umg fly lg ll h qu. I h lby, h budy d h f h uh w ul d h m l h ffv w/h. I dd, h h f h ll w dff h ml udgud ll d h z bw h uh d fud dd dquly h udgud u. D h dff, mkbl m hw Fgu 19. h uml mdllg hwd lvllg ff f k gh f w/h x f gh. h lvllg ff d wh full uhg h uudg. Fgu 17 FLAC 7 mdl Fgu 18 Dgm hwg h dubl ymmy FLAC 7 mdl ud h ll d fud vg. h mdl w ldd lg h bm dg h Jul f h Suh Af Iu f Mg d Mllugy VOLUME 110 REFEREED AER OCOBER 2010 587

[9] Fgu 19 Cm bw h gh db, FLAC 7 mdllg d lby fmd by S d Yk 5 h mdl w ud flu bv h dul gh f h ll. A gf d ud wh h ldg w dud z, dg m fm f l flw d wh h ldg vly. Obvuly, h f d b xludd b m l ul. h ubqu vy lw ldg dd hg h dul gh hvd dug h z vly ldg. I w hf umd h h dul gh w flud by h flw u. h mdl hwd h h lm l dul gh wh w/h u w/h f bu 3 (Fgu 20). Alhugh h mdl hv hd h bg y f h fud w/h f 3, h k gh d wh w/h, w/h f bu 10. A gd mh bw h udgud ul, h w lw w/h lby d h FLAC7 mdl w hw wh h f 0.26 w umd h mdl. h w hvd v wh f gl f 40 f h k d dul gh. A vy ly h ff f h f gl d h dul gh dbd S 8. h lg w/h my b wll d by h Slm9 lu bu d qu ll bhvu, whh w bvd udgud. h ulm bg y f h ll fud dd h h d f d dl gl f h fud ml. N fuh dul ll gh hu b xd bv h bg y. h ul Fgu 20 ugg h h ffv g f w/h lmd mxmum f bu h. N fuh gh b xd f g w/h. Fud bg y Nh h lyl h lby ul mhd h l lh bw ll dul gh d w/h mud udgud h Iml (Fgu 15). S h ll h mly h hgh w/h, h lm z dul gh wh w/h w ud b ld bg y. h ff f h fud fud w hf vgd ug lyl lu f bg y. h lh bw C b d bg y (BC) f gv f gl hw Equ [9] (Myhf10). h dl d f gl umd b h m h qu (v flw ul). Bg y h b ld fu f h f f gl f 30 d 40 Fgu 21. h ulm bg y f h ll hw Fgu 20 b bu 33 M. h ugg h f bu 1.1 M 0.4 M f f gl f 30 40, vly. h FLAC7 mdl dd h f 0.3 M f gl f 40. h mll dff bw h mdl d h lyl lu bbly bu h v flw ul w umd h mdl. h dl gl h mdl w 10. h gd gm bw h Slm9 lu d h dul gh fm h lby ul gv Fgu 20, ugg h ll uhg h dd u w d h lby. h w bbly u f h w mll w/h h bl l bw h lby, udgud d FLAC7 ul. Hwv, h dul gh f h k uh wh w/h f 5 w gfly hgh h h h ul v hugh h w gd mh wh h k gh d h udgud ul. h k ul fm h lby ugg uhg, wh h dul lby ul ugg h uhg ug. h d b xld vl wy: Fgu 20 ll w/h -ghg ff AS. h FLAC 7 mdl (Φb = 40 ) md h Slm 9 qu (Φb = 30 ), S d Yk 5 lby ul d h udgud mum Fgu 21 Ulm bg y f h fud, umg f gl f 30 d 40 588 OCOBER 2010 VOLUME 110 REFEREED AER h Jul f h Suh Af Iu f Mg d Mllugy

Rlvly lg -flu uh dl, h hgh w/h ml, uld bg gd h dld fud dwll bw h ml ldg l d ld fud If f h budy h ul (h fud yld w ly h m lg h h ld uh) d h g z lg m h hgh f h uh. -flu bhvu my hf hv b flud by fu dvlg hugh lvly g g. I gly mmdd h h hm hd fuh by lby. -flu h h h uggd by h lyl lu d h mdllg muh hgh h wuld b xd f uhd ml. O bl xl h h ml mlly uhd d h h bk k ully m ugly hgh dul gh. h ll my l b mvly m dul d hf l fud ul f fg h uld dvl h. h ff f fm bl w hd by Fg d H11. h dul gh ulg fm f bw blk, hld gh by gvy, wuld ly u f bu 1% f h lbd vlu. h lvly hgh gh f bk k h b d vuly bu xmly m m, lly f h dg d bhvu f uh ll. F flug h dul gh my b: lkg blk, blk z, flu vl, k gh d dul h. h f my b. h uy f h lvly hgh dul hmhm f dqu dul gh my lwy b. h dqu dul gh w l uggd by h d h ud f mg hd b mld h Kudf (Fgu 22). Fuh vg qud dm h f h glly hgh -flu h qud mul h dul ll gh mud udgud. h my lud h dvlm f m -flu gh. Dg gy h ll vg ugg d lh bw k ll gh d w/h u w/h f bu 8. Lg ll hu l lkly fl h f h mll ll. ll gh huld xd h vlbl ldg y f h ym wh 5 m 7 m f h f. A hllw dh h wuld qu vy ld ll h my hv uff dul gh bkbk. Ud h d ll dg uld b. A flwh f h dg f uh ll vdd Fgu 23. h um h ubl dul gh luld h b f gh qum. h xm ll w/h vd h gh qum b dmd fm Fgu 24. h lul huld lud l bw ll h h u x. A l mdl huld b u dm f h ldg y uff fl h qud ll wh 5 m f h f. I huld b d u h h k ll gh luld ug Equ [1], d dud Equ [10], vd 50% bbly f flu. Fgu 23 Flw h f uh ll dg [10] Fgu 22 Kudf : vl mum d md 1 AS d h ul f l MSm mdl Fgu 24 ll dul gh fu f w/h h Jul f h Suh Af Iu f Mg d Mllugy VOLUME 110 REFEREED AER OCOBER 2010 589

h bbly f flu, hwv, b d by ug g vlbl ldg y h luld by h qu. Fgu 25 hw h h huld b ddd h ul f Equ [10] vd h dd bbly f flu f h ll w/h. Shuld h ldg y b uff fl h ll, h dg dg f l mu b dd. Smll wll qu mll dul gh d hu mll ll. h l mdl d hw h flw h (Fgu 23) huld b d wh h w lyu. Cuh ll ld dj bly ll hl (lf bly ll) my d b u mll h h ll l u dqu ldg d. h g wdh ff h ll hgh d f vbl l. F h ll u z my hv dff dul gh ulg fm h g wdh dj h ll. h u f g wdh f ul wh h mg bw h qud d uld dul gh mll. h lh bw g wdh d ll dul gh vdd Fgu 26. h lh bd h m hw Fgu 24, umg dd 3 m-wd ll. ll ug dfful d m m uggl u dd zd ll. A ly f dul gh v llwdh vbly g wdh f 1.2 m vdd Fgu 27. A vuly fmuld k ll gh qu f Mky ll h Iml M w fmd by mum dud h Iml d h Kudf. Al ll mum fm h hbzmb w ly lghly udmd by h fmul. Abl d ubl ldg ff w dmd fm bk-ly f bl d ubl ll flu, vly. I w fud h ll flg m h 10 m bhd h lggg f, uld fl vlly. Hwv, ll flg wh 5 m 7 m f h f lwy fld bly. h dul ll gh lh w/h w dmd by udgud mum. I w fud h fuh gh ud bv w/h f bu h. Hwv, lmd lby, whh m w md du uhg, hwd xl u w/h f fv. h xl dul gh wh w/h w l hw by lyl lu dvld dm h dul gh f uh ll. Hwv, h lu dd lud h flu f h fud h ul, hu dg qu bhvu h w bvd udgud. A FLAC7 mdl h ludd h hgg- d fwll muld h udgud mum d hwd h h bg y f h fud fud w h llg f h Clu h f d b dd dug h dg f uh ll: Rdul gh qum; Ldg ff f h vm, d hw h v wh d fm h f; d h lh bw k ll gh d w/h. h m f Mky ll hv b hd f h dff mg vm. Dg h hv b dvld fm h vg d h d h. h ul f h h l dud. Fgu 26 Eff f g wdh dul gh, umg dd 3 m-wd ll. Slm 9 lyl lu wh Φb = 30 d C = 1.6 M Fgu 25 Cm bw h fy f d h d ddl ll qum f ll f w/h = 2.0, 3.0 d 4.0, bd h l bk-f ly (lg = 0.073) Fgu 27 Eff f ll wdh dul gh, umg g wdh f 1.2 m. Slm 9 lyl lu umg Φb = 30 d C = 1.6 M 590 OCOBER 2010 VOLUME 110 REFEREED AER h Jul f h Suh Af Iu f Mg d Mllugy

ulm dul gh. h mdl l dd h ulm gh fm w/h f h. Bh h mdl d lyl lu f bg y uggd uxdly hgh vlu f h. h m u d b vgd fuh. h l f uh ll dg uvl. Hwv, mmdd h h ul dbd h b ud h wh h h w dud. I dd h h ul my l b uuly ld h ml d. Akwldgm h CSIR d lm kwldgd f flg h u f h h wk dbd h. I ul, h mgm d Rk Egg Dm f Iml lum M d m h hbzmb d Kudf hkd f h. Rf 1. ROBERS, M.K.C., GRAVE, D.M.H., JAGER, A.J., d KLOKOW, J. Rk M Bhvu f h Mky Rf Nhm lum M.. SARES, Jhbug, S. Af. Nl I. F Rk Egg. 1997. 2. ROBERS, D.., ROBERS, M.K.C., JAGER, A.J., d COEZER, S. h dm f h dul gh f hd k uh ll wh wdh hgh f 2:1, Jl S.Af. I. M. Mll., vl. 105, 2005.. 401 408. 3. WASON, B.., RYDER, J.A., KAAKA, M.O., KUIJERS, J.S., d LEEANE, F.. Mky ll gh fmul bd bk-ly f ll flu Iml lum, Jl S.Af. I. M. Mll., vl. 108, 2008.. 449 461. 4. WASON, B.. Rk bhvu f h Buhvld Mky Rf d h dg f uh ll, hd h, Shl. f Mg Egg, Uvy f Wwd, Jhbug, RSA. 2010. 5. SENCER, D d YORK, G. Bk-ly f yldg ll ym bhvu Iml lum M,. SARES99, Jhbug, S. Af. Nl I. F Rk Egg, 1999. 44 52. 6. YORK, G. d CANBULA, I. h l ff, l k m gh d ll ym dg, Jl S.Af. I. M. Mll., vl. 98,. 1 J/Fb, 1998.. 27 37. 7. IASCA CONSULING GROU, INC. F Lgg Aly f Cu (FLAC), V. 3.2. Ml M USA. 1993. 8. BARRON, K. A lyl h h dg f ll l, C R N. 1SQ80-00161, Cd C f Ml d Egy hlgy, Egy, M d Ru, Cd, 1983.. 36 42. 9. SALAMON, M.D.G. Sgh d bly f l ll, Wkh l ll mh d dg, US Buu f h I, US Buu f M, S F, USA. 1992. 10. MEYERHOF, G.G. h ulm bg y f fud, Ghqu, vl. 5, 1951.. 301 332. 11. FANG, Z. d HARRISON, J.. Al f ll dgd mdl h ly f bl fu f lby l k m ud xl d, I. J. f Rk Mh. d M. S., vl. 39, 2002.. 459 476. REORIA MARIC LEARNERS SCOO O SCIENCE AWARD* l mgd v f h y l Mquz S Cm hld Mk mu Rdbug 27 d 28 Smb 2010. Eh mmb f h wg m wlkd wy wh hlf-u Kug Rd, d by Rd Rfy Lmd d wh bu R4 500 h, d h hl vd h z f R3 250, d by DCM D Ml. h w md g m h 50 h fl, udyg Gd 12 hyl S d Mhm hl, wh hd dvd h l m fllwg gu vl m July. h m w dud by Mk 1988 wh m f xll Mhm d hyl S hl d ug l S, Egg d hlgy. hfm, Nh W, w u-u. Eh ud h m vd bl dul m fm Advd Lby Sul; h mmb hl vd R2 250 dd by Suh Af u, Mk Shulwh, vu Mquz w d w f h m. Sl, Slbug m hd; h f ud vd bk z dd by All Sf d h hl vd R1 250 fm h Suh Af Iu f Mg d Mllugy (SAIMM). All h l f, d d hd vd -y ub Qu, mgz ublhd by h Admy f S f Suh Af. All vd f f, u f Qu, Gd 12 hy, Chmy, Mhm d lgug udy gud ublhd by v, d Sl yld. Cg Adw, f Slly k Hgh Shl h Nh W v, d Ay Jm Lk, f Fh Hk Hgh Shl h W C, w md l h lum d Gld gy (w ) vly. hy w h wdd Nbk vlud R2 200 d hgh-d x Ium f lul wh R2 300, vly dd by UK-bd GFMS d Oxfd Edul Sul. Hh Elzbh R, f Eu Hgh Shl h F S, d Lulm Alg f Sl lj Sdy Shl h Nh W, w h gl l h lum d Gld gy (w ). hy w h wdd h z f R1 000, dd by h Cul f Sf d Idul Rh (CSIR), d x Ium lul. All h Gld d lum gy w d h h vd x Ium -d f lul. h l bd D Cf (60 79%) d vd x Ium b f lul. f Dvd Blk, D f h Agl Am Cm Du Lby h Uvy f h Wwd, w h gu k. H xd h g l wh h lk ld h w f V, whh w d by Aglgld Ah d Mhm SA. Cludg h dd d ugg h l u hg md d v f gl d, Blk d: Evy, d ll bl b h. H ddd h h m f Mquz u blz m lumu lgy. uly ml! H l dd fu f h l ff-bl bk, Shud f h Ngh, whh h -uhd wh fllw m, f Kh Fm. M. Zmb Zw, Sl Cmmuy d Gvm Rl Aff Mg l ddd h l. Sl h f Mquz. F fuh fm bu h u, Gh Wllm : ghw@mk..z l. (011) 709 4476. F gl fm bu Mquz, l M Wdy hw : wdy@mk..z l. (011) 709 4797. h Jul f h Suh Af Iu f Mg d Mllugy VOLUME 110 REFEREED AER OCOBER 2010 591