Abstract
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.
Highlights
In recent years, innovative remedial measures against liquefaction have been proposed and developed to improve the performance of liquefiable soils under cyclic loading conditions while minimising the economic cost and the impact on existing structures and infrastructures, as well as on the surrounding environment (Bao et al, 2019; Huang and Wen, 2015)
This paper presents the results of a laboratory study aimed to evaluate the influence of different colloidal silica (CS) contents on the behaviour of a liquefiable sand
Each specimen is subjected to a different value of the normalised cyclic stress ratio (CSR), and each one shows a different behaviour under cyclic loading: no failure for CTT-8 (CSR = 0.11, Figure 3(a)), failure for CTT-9 (CSR = 0.13, Figure 3(b)), failure for CTT-1 (CSR = 0.20, Figure 3(c)) and failure for CTT-4 (CSR = 0.27, Figure 3(d))
Summary
Innovative remedial measures against liquefaction have been proposed and developed to improve the performance of liquefiable soils under cyclic loading conditions while minimising the economic cost and the impact on existing structures and infrastructures, as well as on the surrounding environment (Bao et al, 2019; Huang and Wen, 2015) These liquefaction countermeasures include techniques based on microbial processes, such as bio-cementation (DeJong et al, 2006; Montoya et al, 2013; Xiao et al, 2019) or bio-desaturation (He et al, 2013; Rebata-Landa and Santamarina, 2012); other techniques aiming to induce partial saturation, such as water electrolysis (Yegian et al, 2007), air injection (Okamura et al, 2011) or eco-friendly chemical treatment (Eseller-Bayat et al, 2012); and techniques based on the use of waste materials, like tyre chips (Mashiri et al, 2015; Zornberg et al, 2004), as well as of grouting materials, such as bentonite suspension or colloidal silica (CS) (El Mohtar et al, 2013; Gallagher and Mitchell, 2002; Gallagher et al, 2007a, 2007b). Bentonite grouting suffers from the low mobility of the grout so that high injection pressures and/or chemical additives should be used to facilitate the grout permeation into the soil (Rugg et al, 2011; Yoon and El Mohtar, 2013)
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