Answer-1: a. What is Soil Soil stabiliz stabilization ation? ? What ae ae the !aio"s !aio"s metho#s metho#s o$ stabilizat stabilization? ion? E%&lain these bie$l'. ----------------------------------------------------------------------------------
Soil sta(ili)ation is any treatment a!!lie$ to a soil to im!ro+e its strength an$ +ulnera(ility to ater/ i treate$ soil is a(le to ithstan$ the stresses im!ose$ on it (y traic un$er all eather con$itions ithout $eormation0 then it is generally regar$e$ as sta(le. The main metho$s o soil sta(ili)ations or roa$ !ur!oses are/ 1. echa echani nica call sta(i sta(ili li)a )ati tion on 2. Cemen Cementt sta( sta(il ili) i)at atio ion n 3. #ime #ime sta sta(i (ili li)a )ati tion on 4. itu itumi mino nous us sta(i sta(ili li)a )ati tion on
(. Me)hani)al stabilization*
echanical sta(ili)ation is accom!lishe$ (y mi,ing or (len$ing soils o to or more gra$ations to o(tain a material meeting the reuire$ s!eciication. The soil (len$ing may tae !lace at the construction site0 at a central !lant0 or at a
(orro area. The (len$e$ material is then s!rea$ an$ com!acte$ to reuire$ $ensities (y con+entional means. echanical sta(ili)ation can (e $one in three in$ o site installation as $escri(e$ olloing. %n site mi, o a granular sta(ili)e$ su((ase shall irst s!rea$ing the reuire$ thicness o im!orte$ (orro soil in uniorm $e!th0 an$ then a$mi,ing the $ry constituent materials using con+entional (la$e gra$ers to mo+e them rom one si$e o the roa$ to other. 5!on com!letion o the (len$ing !rocess the $rymi,e$ materials is s!rea$ in layer o uniorm thicness an$ ater is a$$e$ +ia the s!ray (ar o a ater taner to (ring it to the $esire$ moisture content or com!action to a uniorm thicness. %n Tra+elling !lant construction0 the !rocess is similar to that $escri(e$ a(o+e0 e,ce!t that a single !ass o s!eciali)e$ mo+ing eui!ment is all that is necessary to $ry mi, the soils0 a$mi, ater0 an$ s!rea$ the moist material to a uniorm $e!th0 !rior to com!action. %n stationary !lant0 the soil to (e (len$e$ are (rought to a central location or su!!ly0 an$ s!eciali)e$ eui!ment is then use$ to !ro!ortion an$ mi, the materials an$ ater0 ater hich the moist mi,ture shall (e (rought to the construction site (y truc0 s!rea$ to a uniorm $e!th (y an aggregate s!rea$er an$ com!acte$. 'hilst this construction !rocess is more e,!ensi+e than the to !re+iously $escri(e$0 it normally using in large scale ors.
+. Cement Stabilization*
Cement sta(ili)ation is the most commonly use$ in su(gra$e ca!!ing an$6or su((ase layers in ma7or roa$ !a+ements0 an$ in su((ases an$ roa$(ases o secon$ary ty!e roa$s. 8t is ne+er use$ in surace courses (ecause0 as ell as ha+ing !oor resistance to a(rasion0 it must (e !rotecte$ rom moisture entry into the cracs that ill ine+ita(ly orm the cement treate$ material. The ma7or actors o cement sta(ili)ation use i$ely are (ecause o olloing reasons/ - &asily a+aila(ility o cement in all !laces - 5se o cement usually in+ol+es less care an$ control than many other sta(ili)ers. - ore technical inormation a+aila(le o cement treate$ soil mi,ture than any other ty!e o soil sta(ili)ation. - ost ty!e o soils can (e sta(ili)e$ ith cement i enough is use$ ith the right amount o ater an$ !ro!er com!action an$ curing. Cement as a sta(ili)ing me$ium can (e +ery eecti+e i use$ !ro!erly. A!!ro!riate !article si)e $istri(ution0 thorough mi,ing an$ maintenance o o!timum moisture le+els ill yiel$ a successul mi, ith ma,imum inal set GPQS-11
strength. A com!romise in any o the a(o+e ill result in a re$uction in strength o the inishe$ !ro$uct. 9oe+er inal set strength is not the only reuirement o cement0 a$euate ora(ility an$ a$euate :i lo; strength !rior to curing are to others. These other reuirements oten conlict ith the ma,imi)ation o inal strength or e,am!le (y calling or higher clay content. A suita(le soil can (e consi$ere$ to (e one that has no organic material0 has a clay content (eteen 1<= an$ 2<= an$ has a air range o ell $istri(ute$ !article si)es u! to a ma,imum o 2
,. -ime stabilization
#ime0 either alone or in com(ination ith other materials0 can (e use$ to treat a range o soil ty!es. The mineralogical !ro!erties o the soils ill $etermine their $egree o reacti+ity ith lime an$ the ultimate strength that the sta(ili)e$ layers ill $e+elo!. 8n general0 ine-graine$ clay soils :ith a minimum o 2" !ercent !assing the >2<< sie+e :?4mm; an$ a Plasticity 8n$e, greater than 1<; are consi$ere$ to (e goo$ can$i$ates or sta(ili)ation. Soils containing signiicant amounts o organic material :greater than a(out 1 !ercent; or sulates :greater than <.3 !ercent; may reuire a$$itional lime an$6or s!ecial construction !roce$ures.
'hen lime an$ ater are a$$e$ to a clay soil0 chemical reactions (egin to occur almost imme$iately.
1. [email protected] 8 uiclime is use$0 it imme$iately hy$rates :i.e.0 chemically com(ines ith ater; an$ releases heat. Soils are $rie$0 (ecause ater !resent in the soil !artici!ates in this reaction0 an$ (ecause the heat generate$ can e+a!orate a$$itional moisture. The hy$rate$ lime !ro$uce$ (y these initial reactions ill su(seuently react ith clay !articles. 2. o$i[email protected] Ater initial mi,ing0 the calcium ions :Ca; rom hy$rate$ lime migrate to the surace o the clay !articles an$ $is!lace ater an$ other ions. The soil (ecomes ria(le an$ granular0 maing it easier to or an$ com!act. At this stage the Plasticity 8n$e, o the soil $ecreases $ramatically0 as $oes its ten$ency to sell an$ shrin. The !rocess0 hich is calle$ Blocculation an$ agglomeration0 generally occurs in a matter o hours. 3. Sta(ili)[email protected] 'hen a$euate uantities o lime an$ ater are a$$e$0 the !9 o the soil uicly increases to a(o+e 1<."0 hich ena(les the clay !articles to (rea $on. The soil is transorme$ rom a san$y0 granular material to a har$0 relati+ely im!ermea(le layer ith signiicant loa$ (earing ca!acity. The !rocess (egins ithin hours an$ can continue or years in a !ro!erly $esigne$ system. #ime-Po))olan i,tures or Soils ith #o Amounts o Clay #ime (y itsel can react ith soils containing as little as ? !ercent clay an$ Plasticity 8n$ices as lo as 1<. 8 the soil is not suiciently reacti+e0 lime can (e com(ine$ ith an a$$itional source o silica an$ alumina. Such B!o))olans inclu$e ly ash an$ groun$ (last urnace slag. The a$$itional silica an$ alumina rom the !o))olan react ith the lime to orm the strong cementitious matri, that characteri)es a lime-sta(ili)e$ layer. Pro!erly !ro!ortione$ mi,tures o lime an$ !o))olans can mo$iy or sta(ili)e nearly any soil0 (ut are ty!ically use$ or soils ith lo to me$ium !lasticity. Ely ash is the most commonly use$ !o))olan. 8t is the inely $i+i$e$ resi$ue that results rom the com(ustion o !ul+eri)e$ coal in !oer !lant (oilers0 hich is trans!orte$ rom the com(ustion cham(er (y e,haust gases.
Construction [email protected] The olloing construction recommen$ations a!!ly to the use o hy$rate$ lime an$ uiclime in the sta(ili)ation or mo$iication o su(gra$e :su((ase; an$ (ase courses. 1. Scariication an$ 8nitial Pul+eri)[email protected] Ater the soil has (een (rought to line an$ gra$e0 the su(gra$e can (e scariie$ to the s!eciie$ $e!th an$ i$th an$ then !artially !ul+eri)e$. 8t
is $esira(le to remo+e non-soil materials larger than ?"mm0 such as stum!s0 roots0 tur0 an$ aggregates. 2. #ime [email protected] i. Quiclime There are to ays that $ry uiclime can (e a!!lie$. Eirst0 selunloa$ing trucs or trailers can $istri(ute uiclime !neumatically or mechanically the ull i$th o the truc. ecause granular an$ !e((le uiclime lo is more controlla(le than hy$rate$ lime0 it is a common !ractice to use trucs ith (uilt in aggregate-ty!e s!rea$ers. ii. Dry 9y$rate$ #ime 9y$rate$ lime shoul$ (e uniormly s!rea$ at the s!eciie$ !ercentage rom suita(ly eui!!e$ trucs. An a!!ro+e$ s!rea$er is !reera(le or uniorm $istri(ution. The a!!lication rate o $ry hy$rate$ lime can (e measure$ using the same metho$ as $escri(e$ a(o+e or uiclime. 3. Slurry 8n this a!!lication0 the soil is generally scariie$ an$ the slurry is a!!lie$ (y $istri(utor trucs. ecause lime in slurry orm is much less concentrate$ than $ry lime0 oten to or more !asses are reuire$ to !ro+i$e the s!eciie$ amount o lime soli$s. To !re+ent runo an$ conseuent non-uniorm lime $istri(ution0 the slurry is mi,e$ into the soil imme$iately ater each s!rea$ing !ass. 4. Preliminary i,ing an$ 'atering ". Preliminary mi,ing is reuire$ to $istri(ute the lime throughout the soil an$ to initially !ul+eri)e the soil to !re!are or the a$$ition o ater to initiate the chemical reaction or sta(ili)ation. This mi,ing can (egin ith scariication. Scariication may not (e necessary or some mo$ern mi,ers0 hoe+er. During this !rocess or imme$iately ater0 ater shoul$ (e a$$e$. F. elloing Perio$ The lime-soil mi,ture shoul$ mello suiciently to allo the chemical reaction to change :(rea $on; the material. The $uration o this melloing !erio$ shoul$ (e (ase$ on engineering 7u$gment an$ is $e!en$ent on soil ty!e. The melloing !erio$ is ty!ically 1 to ? $ays. Ater melloing0 the soil shoul$ (e remi,e$ (eore com!action. Eor lo Plasticity 8n$e, soils0 or hen $rying or mo$iication is the goal0 melloing is oten not necessary. ?. Einal i,ing an$ Pul+eri)ation To accom!lish com!lete sta(ili)ation0 a$euate inal !ul+eri)ation o the clay raction an$ thorough $istri(ution o the lime throughout the soil are essential. i,ing an$ !ul+eri)ation shoul$ continue until 1<< !ercent o GPQS-11
non-stone material !asses the 1-inch sie+e an$ at least F< !ercent o nonstone material !asses the num(er 4 sie+e. . Com!action The lime-soil mi,ture shoul$ (e com!acte$ to the $ensity reuire$ (y s!eciication0 ty!ically at least H" !ercent o the ma,imum $ensity o(taine$ Stan$ar$ test. &[email protected] To ensure a$euate com!action0 the eui!ment shoul$ (e matche$ to the $e!th o the lit. Com!action can (e accom!lishe$ in one lit using hea+y !neumatic or +i(ratory !a$oot rollers or a com(ination o the shee!soot an$ light !neumatic +i(ratory !a$oot rollers or tam!ing oot rollers. Ty!ically0 the inal surace com!action is com!lete$ using a steel heel roller. H. Einal Curing eore !lacing the ne,t layer o su((ase :or (ase course;0 the com!acte$ su(gra$e :or su((ase; shoul$ (e alloe$ to har$en until loa$e$ $um! trucs can o!erate ithout rutting the surace. During this time0 the surace o the lime treate$ soil shoul$ (e e!t moist to ai$ in strength gain. This is calle$ Bcuring an$ can (e $one in to [email protected] :a; moist curing0 hich consists o maintaining the surace in a moist con$ition (y light s!rinling an$ rolling hen necessary0 an$ :(; mem(rane curing0 hich in+ol+es sealing the com!acte$ layer ith a (ituminous !rime coat emulsion.
. it"mino"s stabilization
8n ituminous sta(ili)ation metho$ (ituminous materials are thoroughly mi,ing into a soil or soil aggregate mi,ture to construct the (ase course0 an$ surace course0 ca!a(le to carry traic loa$ un$er normal con$itions o moisture an$ traic. De!en$ing on the granulometric com!osition an$ !hysical !ro!erties o the soil0 there are our ty!es o (itumen-sta(ili)e$ !ro$ucts0 as ollos/ 1. Soil ([email protected] ater!rooe$ cohesi+e soil. est results are o(taine$ ith soils ith grain si)e such that0 a; ma,imum si)e is not greater than a!!ro,. one-thir$ o the com!acte$ thicness or the same as thicness o com!acte$ (ase course. 2. San$ ([email protected] #oose san$ !articles cemente$ ith (itumen. The sa$ can (e (each or ri+er san$. e,isiting roa$ay material0 su(stantially ree rom organic matters0 lum!s0 or a$herent ills o clay are also inclu$e$ in this category. 3. 'ater!rooe$ granular sta([email protected] A goo$ gra$ation o soil !articles0 rom coarse to ine an$ ha+ing a high !otential $ensity0 is ater!rooe$ (y a$$ition o 1 to 2 !recent (itumen. GPQS-11
4. %ile$ [email protected] A soil surace consisting o silt-clay materials is sta(ilise$ (y s!raying slo or me$ium curing (itumen cut(acs or emulsions. The main !ur!ose o oile$ earth is to !ro$uce a ater an$ a(rasion resistant surace.
These are the our ma7or in$ o soil sta(ilisation on roa$ ors0 there are many other in$ o soil sta(ili)ation metho$s are in !ractice or (uil$ing construction sectors.