MATERIALS

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 09 | Sep 2020 www.irjet.net p-ISSN: 2395-0072

Settlement Characteristics of Stone Column on Saturated Soil

Jisna P1, Seemon S.2

1Post Graduate Student of Civil Engineering, IES College of Engineering, Kerala, India 2Assistant Professor, Dept. of Civil Engineering, IES College of Engineering, Kerala, India --------------------------------------------------------------------*** ---------------------------------------------------------------------Abstract – Construction of structures in soft soils are fromstructuresgeneratesexcessporewaterpressureinsoft difficult due to change in properties of overlying soil. These layer.Theloadfromthestructureisinitiallytakenupbythe may include change in water content, shear strength, andvoid watermoleculesexistingwithinthesoftlayer.Asaresult,a ratio. Construction of road, railways embankments over a soft hydraulicgradientdevelopsandslowlythewaterwillooze soil needs special consideration due to the change in the outofporespacedependinguponpermeabilityofsoil.With overlying soil characteristics which may led to settlement the passageof time excess pore waterpressure decreases of the structure. Soft clays are characterized by low shear and correspondingly the effective stresses in the layer strength, high compressibility and low bearing capacity. increases. Consolidation is one of the problems in soil engineering. During consolidation of soft clays under loading, large ground As a result, consolidation process continues and soil gets settlements take place over long periods of time owing to low compressed due the load transferring to the soil grains. permeability of clays. So, it is necessaryto avoid such damages Foundationofthestructurewouldsettleuntilthecomplete by providing suitable vertical drains before construction. consolidationtakesplace.Irreparabledamageswilloccurto made. When structures are constructed over highly longtime.Thismayduetotheconsolidationcharacterofthe structure under consolidation process. Because of low This paper presents the results obtained from the settlement permeabilityandpoordrainagecharacteristicsofsoftsoil,it characteristics of saturatedbentoniteclayusingstonecolumn becomes essential to drain out pore water before as a vertical drain. The main objective of the study is to find construction begins otherwise, the added weight of new the settlement character, discharge capacity and shear structurewillcausewatertosqueezeoutforalongperiod strength of bentonite clay with stone columns under different oftime.Thus,settlementcanbereduced beforethenewly patterns. The study was carried out by changingthe diameter construction over these soft soils. So, it would be better if of stone column and spacing of stone columns and patterns of majorportionof this consolidation settlement takes place column. Shear strength characteristics of clay was determined before/duringconstructionphaseitself. at different depths adjacent to the stone columns. Results shows that using stone column in saturated soil, settlement Thestonecolumnsareconstructedbymakingholesinthe increases with 12% with increase in diameter, at decreased depositandfillingtheseholeswithgravel(orsmallstones) spacing. Decreased spacing accelerates the consolidation of size 6 to 100 mm. Stone columns act as vertical drains, effects by improving the drainage path for pore water increasingrateofconsolidation.Theyreinforcethesoftsoil dissipation. Straight pattern has moreeffect on the settlement deposit because it is replaced by strong stone columns at characteristics of stone column. Shear strength of the discrete points. The stiffness of the stone columns is very saturated soil increase to 4.7 % with the provision of stone largeascomparedtothatofthesoftsoil.Alargeportionof column. the superimposed load is carried by stone columns. Thus, thebearingcapacityoftheclaydepositisincreasedandthe Keywords— Consolidation, Ground Improvement, settlementsarereduced.

Settlement, Shear Strength, Stone Column

Thisstudyinvolvesuseofstonecolumnasaverticaldrain 1.INTRODUCTION in saturated soft soil. They are placed at a particular

Constructionofanystructureonthegroundrequiresa strengthandconsolidationcharacteristics ofsoftclays. By proper investigation about the site to be built. It mainly providingstonecolumninsaturatedsoildischargecapacity includesinvestigationaboutsoil;itstypestype,andshear increaseanditleadstosettlementofsurroundingsoil.Also strengthcharacteristics.Basedontheseresults,ifthesoilis shearstrengthofthesoilcanbeincreased.Besidesworking having suitable shear strength construction will proceed. asdrainsitalsoactsasareinforcementtothesoilbecause Whereasifthesoilispoorsuitablegroundmodificationsare softclaysreplacebythesecolumnsatdiscretepoint. compressiblesoilsuchasclay,settlementwilloccuraftera 2. OBJECTIVES AND SCOPE OF THE STUDY spacing. It is used as a technique for improving the shear soil.Consolidationistheexpulsionofporewaterfromclay Construction of structures over compressible soil is undertheapplicationofsteadystaticload.Thisresultsin difficultduetothesettlementproblems.Damagesaremainly reductioninvolumecausingsettlement.Impositionofload duetolongtermconsolidationsettlement.So,itisbetterto