ABSTRACT APPLICATION OF FLY ASH IN STABILIZATION OF BLACK COTTON SOIL Dr. S.R.Kumar (Director), Shirke Uay Singh(Asso.Prof.) Deptt. Of CIVIL Engg.,Meicapse Institute inore (M.P.) The black cotton soil hich erive from Bessel rock of mala region of often fin not suitable for infrastructure projects such as highays,railays, ater reservoir,reclamation etc,ue to it s high plasticity an expansive nature. Extensive laboratory an fiel trials having carrie out by various researchers an have shon promising results for application of such expensive soil after stabilization ith aitives such as san,silt,lime an fly ash etc as fly ash is freely available in the vicinity of a thermal poer plants, it can be use for stabilization of black cotton soil for various parts of civil construction. The present paper escribes a stuy carrie out to check the improvement in the in the properties of black cotton soil ith eition of the fly ash in varying percentages to form a homogenous mass of a require physical properties. The paper escribes a methoology aopte for placing the materialas in layers of require thickness. Key ors :- compaction, fly ash,black cotton soil & stabilization INTRODUCTION The Mala Pleatue is mainly consist of basaltic traps of volcanic origin an the entire area is cover ith highly expensive resiual black cotton soil ith liqui limit varying from 30% to 40% the soil by nature shoing extensive expansion in black climate an uring summer extensive shrinkage,cracks exceeing 10 mm in ith ere notice on surface generally. The soil as not suitable in natural form for construction of civil engineering Projects ue to folloing reasons. 1. Poor orkability for compaction the construction scheule is critical an it is ifficult to carry out the ork uring monsoon ell optimum moisture content cannot be achieve. 2. High compressibility 3. In aequate shear strength for require slope stability Instea of borroing a suitable material from ling istance for stabilization it as propose to use the fly ash that is available in nearest poer plant.accoringly a etail literature revie as carrie out oon the subject that as folloe by laboratory an fiel tests. This paper escribe the properties of natural black cotton soil an stabilize soil ith varying percentage of fly ash.the proceure aopte for mixing the soil ith fly in the fiel an the test result having escribe
LABORATORY TESTS Folloing laboratory tests have been carrie out as per IS : 2720. the tests ere carrie out both on mature soil in stabilize soil ith fly ash collecte from poer plant of Grasim inustries naga,hich is in the vicinity of Inore (M.P.) all tests carrie out in the civil engineering epartment s laboratory of meicaps institute of science technology, Inore(M.P.) i. Grain size istribution analysis ii. Atterberg limit test iii. Proctor compaction test iv. Unconfine compression test v. Permeability test The soil as mixe ith fly ash in varying proportion by volume.mixing as thoroughly carrie out manually an tests ere conucte as per the stanar proceure mention as per IS coe. The liqui limit an plastic limit of soil ith various percentage of fly ash given in table 1. s.no. Soil + fly ash Liqui limit Plastic limit (%) Plasticity inex (%) 1. Only soil 33 18 15 2. Soil + 10%fly ash 30 16 14 3. Soil + 20 %fly ash 28 15 13 4. Soil + 25% fly ash 27 13 14 5. Soil + 30 % fly ash 25 13 12 The proctor tests carrie out is summarize in fig 1.
The grain size istribution of the natural & fly ash is shon in fig.2 FIG : GRAIN SIZE ANALYSIS OF BORROW SOIL AND FLY ASH
Unconfine compression strength tests have been carrie out on cylinrical sample of 35 mm ia. & 25 mm height prepare using miniature compaction apparatus ith 15 % moisture content.the sample ere alloe to cure by air rying for 15 ays the samples ere teste ith a constant strain rate of 0.625 mm per min. the result are given in table 2. Description Sample imension before tests in Dia (mm) Height of sample (mm) Wet ensity (kn/m 3 ) Water content (%) Dry ensity (kn/m 3 ) Unconfine compressive strength(kn/m 2 ) Soil 33 70.20 18.51 2.61 18.04 2697 Soil + 33 70.20 18.46 2.34 17.74 3533 10%flyash Soil + 20%flyash 33.10 70.30 17.53 2.22 17.15 2850 Soil + 25 33.20 70.35 16.47 1.80 16.17 2805 %flyash Soil + 30%flyash 33.25 70.40 15.40 1.64 15.13 21.65 DETERMINATION OF UNCONFINED COMPRESSIVE STRENGHT OF SOIL FLY ASH MIXTURE. The permeability of natural & stabilize soil as measure using a falling hea test in the laboratory an results are given in table 3. sr.no. Soil mixture Permeability (m/sec) 1. Natural soil 13.6*10-7 2. Soil ith 10% fly ash 9.14*10-7 3 Soil ith 25% fly ash 6.9*10-7 FIELD TESTS PERMEABILITY TEST RESULTS Fiel trails ere carrie out by construction an environment measuring 4 meter ie an 25 meter long,keeping height about 600 mm.each layer of 200 mm loose thickness as place hich varying fly ash content the layers ere place such that fly ash layer is saniche beteen 2 soil layers as per etail given table no. 4
Fly ash content Thickness of layers in (mm) (%) Bottom soil layer Mile fly ash layer Top soil layer 10 90 20 90 20 80 40 80 25 75 50 75 30 70 60 70 TABLE 4. THICKNESS OF LAYERS After spreaing layers of require thickness a isc harro equipment as use for uniform mixing of soil an fly ash. Then the require quantity of ater as manually sprea over the layer to achieve the require moisture content of 50% the compaction is carrie out ith a 12 ton smooth heal roller. Each layer of mix prepare as above as compacte ith 8 passes of the roller the material after compaction as fin to be quite har an no significant penetration of the roller heel as note uring last 2 passes. After compaction the thickness of layer as fin to be 120 130 mm it as initially 200mm loose thickness. To check the aequacy of compaction folloing controlle tests ere carrie out on each of the compacte layer. 1. In-site ensity by core cutter. 2. Moisture content 3. Light cone penetration tests The result of the ensity observe base on core cutter is summarize in table 5 it s shos that the maximum ry ensity is obtain for moisture content beteen 12-14%. Among various % of fly ash use the ensity is foun 25 % fly ash in the mix.on penetration ere also carrie out from the compacte embankment. Typical results are given in fig.3
Fig 3. results of light one penetration tests Layer Ash Content b = bulk unit t.(kn/m3) = moisture content (%) = ry unit t in.(kn/m3) (i) (ii) I 10 b 16.8 10.2 15.3 16.6 13.0 14.9 ii 20 b iii 25 b 19.0 14.2 16.7 18.5 17.0 15.6 19.9 15.0 17.5 17.9 18.0 15.1
iv 30 b 17.6 11.9 15.5 17.6 14.0 15.6 Table 5 : DENSITY AND MOISTURE CONTENT OF COMPACTED LAYERS BY CORE CUTTER CONCLUSIONS Base on laboratory an fiel tests folloing conclusions having mae As the natural soil has generally high plasticity (liqui limit >40) it as ifficult to use irectly for construction hoever the test carrie out ith ifferent proportion of fly ash inicate that the orkability an ry ensity are maximum ith 25 % fly ash the natural soil use in construction shall be rie ith moisture content belo 7 %. it has also observe that placing three layers ith fly ash layer sanich beteen soil layers an mixing them ith isc : hallo is conveniently orkable. REFERENCES 1. Chan.F.H (1988) founations on expensive soils chen & associates.elsevier publications U.S.A. 2. Erai cokca(2001) use of claas c fly ash for the stabilization an an expensive soil journal of geotechnical an geo environmental engineering vol.1-7,july pp.568-573 3. Prashanth.J.P.(1998) evoluytion of the properties of fly ash for its use in geo technical applications,ph.d thesis IISC Bangalore 4. Raymon n.yong an benno P. Warkentin(1975) soil properties an behavior :-Elsevier publications U.S.A.