Title:
Evaluation of sand treated with colloidal silica gel

dc.contributor.advisor Rix, Glenn J.
dc.contributor.author Spencer, Laura Marie en_US
dc.contributor.committeeMember Assimaki, Dominic
dc.contributor.committeeMember Burns, Susan
dc.contributor.committeeMember Qu, Jianmin
dc.contributor.committeeMember Santamarina, J. Carlos
dc.contributor.department Civil and Environmental Engineering en_US
dc.date.accessioned 2011-03-04T20:15:29Z
dc.date.available 2011-03-04T20:15:29Z
dc.date.issued 2010-08-31 en_US
dc.description.abstract Liquefiable soils are common at ports due to the use of hydraulic fills for construction of waterfront facilities. Liquefaction-induced ground failure can result in permanent ground deformations that can cause loss of foundation support and structural damage. This can lead to substantial repair and/or replacement costs and business interruption losses that can have an adverse effect on the port and the surrounding community. Although numerous soil improvement methods exist for remediating a liquefaction-prone site, many of these methods are poorly suited for developed sites because they could damage existing infrastructure and disrupt port operations. An alternative is to use a passive remediation technique. Treating liquefiable soils with colloidal silica gel via permeation grouting has been shown to resist cyclic deformations and is a candidate to be used as a soil stabilizer in passive mitigation. The small-strain dynamic properties are essential to determine the response to seismic loading. The small-to-intermediate strain shear modulus and damping ratio of loose sand treated with colloidal silica gel was investigated and the influence of colloidal silica concentration was determined. The effect of introducing colloidal silica gel into the pore space in the initial phase of treatment results in a 10% to 12% increase in the small-strain shear modulus, depending on colloidal silica concentration. The modulus reduction curve indicates that treatment does not affect the linear threshold shear strain, however the treated samples reduce at a greater rate than the untreated samples in the intermediate-strain range above 0.01% cyclic shear strain. It was observed that the treated sand has slightly higher damping ratio in the small-strain range; however, at cyclic shear strains around 0.003% the trend reverses and the untreated sand begins to have higher damping ratio. Due to the nature of the colloidal silica gelation process, chemical bonds continue to form with time, thus the effect of aging on the dynamic properties is important. A parametric study was performed to investigate the influence of gel time on the increase in small-strain shear modulus. The effect of aging increases the small-strain shear modulus after gelling by 200 to 300% for the 40-minute-gel time samples with a distance from gelation (time after gelation normalized by gel time) of 1000 to 2000; 700% for the 2-hour-gel time sample with a distance from gelation of 1000; and 200 to 400% for the 20-hour-gel time samples with a distance from gelation of 40 to 100. The treatment of all potentially liquefiable soil at port facilities with colloidal silica would be cost prohibitive. Identifying treatment zones that would reduce the lateral pressure and resulting pile bending moments and displacements caused by liquefaction-induced lateral spreading to prevent foundation damage is an economic alternative. Colloidal silica gel treatment zones of varying size and location were evaluated by subjecting a 3-by-3 pile group in gently sloping liquefiable ground to 1-g shaking table tests. The results are compared to an untreated sample. The use of a colloidal silica treatment zone upslope of the pile group results in reduced maximum bending moments and pile displacements in the downslope row of piles when compared to an untreated sample; the presence of the treatment zone had minimal effect on the other rows of piles within the group. en_US
dc.description.degree Ph.D. en_US
dc.identifier.uri http://hdl.handle.net/1853/37131
dc.publisher Georgia Institute of Technology en_US
dc.subject Bender elements en_US
dc.subject Shaking table en_US
dc.subject Colloidal silica gel en_US
dc.subject Sand en_US
dc.subject Liquefaction mitigation en_US
dc.subject Resonant column en_US
dc.subject.lcsh Silica gel
dc.subject.lcsh Colloids
dc.subject.lcsh Soil conditioners
dc.subject.lcsh Soil liquefaction
dc.title Evaluation of sand treated with colloidal silica gel en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.corporatename School of Civil and Environmental Engineering
local.contributor.corporatename College of Engineering
relation.isOrgUnitOfPublication 88639fad-d3ae-4867-9e7a-7c9e6d2ecc7c
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
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