Full-Scale Field Testing of Colloidal Silica Grouting for Mitigation of Liquefaction Risk (original) (raw)
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SOIL IMPROVEMENT TO COUNTER LIQUEFACTION USING COLLOIDAL SILICA GROUT INJECTION
Soil liquefaction due to earthquakes is a major reason of damage to buildings and other structures. This study deals with soil improvement against liquefaction by injection of a particular stabiliser, colloidal silica, which is nontoxic and stable. Laboratory experiments were performed to determine the effects of colloidal silica grout injection regarding soil strength and deformations. The experiments involved static and dynamic triaxial tests on untreated and treated soil samples. The variables used in the tests are the relative density (loose-40%, medium-60% and dense-80%), the confining pressure (100 and 300 kPa), and the curing period of silica treated samples (7 and 28 days). The results clearly indicate the significant increase in strength of the soil with colloidal silica injection. Furthermore, the relative increase is the highest in the sand of the lowest relative density which is the most probable candidate for soil improvement. The observations that the increase in the strength of colloidal silica treated sands with curing time is gradual and continuous add to the advantage of this method for use in soil improvement works. By using the dynamic test results, the equivalent Young modulus (or shear modulus) and the hysteretic damping ratio of untreated and treated soils are compared.
Effects of high-diluted colloidal silica grouting on the behaviour of a liquefiable sand
Geotechnical Research, 2020
The effectiveness of colloidal silica (CS) treatment in increasing the liquefaction resistance of sandy soils is by now amply demonstrated. However, the best value of the CS content to achieve high performance, minimising economic cost and impact on buildings and the environment, has not yet been quantified. This paper presents the results of a laboratory study aimed to evaluate the influence of different CS contents on the behaviour of a liquefiable sand. The investigation included direct shear, cyclic triaxial, hydraulic conductivity and oedometer tests. CS contents 0, 2 and 5% (by weight) were used for all tests, except for direct shear tests (CS contents 0 and 2%) and oedometer tests (CS contents 0, 2, 3, 5, 10 and 13%). The test results showed that 2% CS content was enough to increase the soil strength under cyclic and monotonic loading conditions. The hydraulic conductivity of treated soil decreased significantly as CS content increased. Oedometer tests pointed out that the main disadvantage of CS treatment is the soil compressibility increase. On the basis of the obtained results, 2% CS content seems to be recommended because it shows effectiveness and capability to improve the liquefaction resistance of sand while minimising the soil compressibility increase.
1996
Colloidal silica (CS) is a low-viscosity liquid that can be made to gel by addition of brine. This property allows it to be injected into, or mixed with, soil, so that after gelling the colloidal silica blocks the pore space in the soil and forms a barrier to the flow of contaminated groundwater or non-aqueous liquids (NAPLs). Gelled-in-place CS was first studied for the petroleum industry and later for protecting groundwater quality. Noll investigated the use of colloidal silica diluted so that its solids content was reduced from 30% (a typical nominal value for material as delivered) to values as low as 5%. The more dilute colloids could still be made to gel, although more slowly, and the resulting gel was weaker. Because the proposed application of colloidal silica grout involves emplacing it in the subsurface by permeation, jet grouting, or soil mixing where its role as a barrier will be to resist flow of contaminants, the effects of these contaminants on the properties of the g...
The Mechanical Response of a Silty Sand Stabilized with Colloidal Silica
Geotechnics
This paper presents a laboratory investigation into the mechanical response of a silty sand, with a fines content of 10%, stabilized with colloidal silica (CS). To this end, a series of unconfined compression tests as well as monotonic and cyclic triaxial tests was performed on a silty sand, comprising a mixture of a clean sand and a silty sand, stabilized with two concentrations of CS. The effect of various parameters on the behaviour of the stabilized silty sand was studied, such as CS concentration, soil density, and the presence of fines. The test results were compared with the corresponding of the untreated silty sand as well as the parent clean sand. It is shown that stabilization, even at the lowest CS = 6% concentration studied, significantly improves the undrained shear strength as well as the liquefaction resistance of the stabilized silty sand. Both the monotonic and cyclic response of the stabilized soil are only slightly affected by density. Furthermore, cyclic strainin...