Effect of Colloidal Silica Aqueous Gel on the Monotonic and Cyclic Response of Sands

Effects of Colloidal Silica Grouting on Geotechnical Properties of Liquefiable Soils: A Review

“…For treated soil, most of the tests reported in older studies and in some recent ones were performed without prior water saturation [14,23,63,66,68,69] to avoid disturbance to the gelled material. On the contrary, in other studies soil specimens were previously saturated [48,64,70,71,74], in some cases using very high values of the backpressure (up to 700 kPa). When back-pressure saturation is not performed, pore pressure response is not measured during the shearing phase and test results are processed with reference to total stress, or assuming that mean total and effective stresses are practically identical [68].…”

“…Published data generally agree that the liquefaction resistance of grouted soil improves due to soil grouting, and that the level of improvement is directly related: (i) to the amount of silica particles diluted in the stabilizing grout; (ii) to the time between the end of the gelation process and the beginning of testing (known as curing time), increasing as both these factors increase [14,[23][24][25][37][38][39][47][48][49][50][60][61][62][63][64][65][66][67][68][69][70]. The same findings apply for grouted material subjected to static loading conditions [14,37,[48][49][50]60,61,[63][64][65]67,[69][70][71][72][73][74][75][76]. The behavior of grouted soil under dynamic loading at low-medium strain levels has been much less analyzed [77][78][79].…”

“…This decrease can be of several magnitudes, and the more the silica concentration in the grout, the more the expected permeability decreases, up to values typical of clay [13,14,17,66,72]. Finally, the effects of grouting on the soil compressibility have been scarcely investigated, even though this knowledge is fundamental for practical applications (the compressibility of soil would influence the settlements of structures and infrastructures in the area of intervention) [14,37,67,[70][71][72]. Most of the results show that the treated soil is more compressible than the untreated one, even though a strict comparison among these data is not possible due to the differences in testing conditions.…”

“…The same range of values was adopted by Triantafyllos et al [74], who stated that increasing the back-pressure within this range does not produce damage to the gel since they observed that drained loading on similar stabilized samples gave reproducible results. Pavlopoulou and Georgiannou [70] obtained repeatable results from specimens that were back-pressure saturated in a standard way; they also stated that increasing the pore water pressure does not damage the gel, and that the treated sand response is controlled by the effective stresses; thus, measuring the pore water pressure response is required in laboratory tests on CS-treated sand.…”

The Effect of Carbon Nanotubes on the Strength of Sand Seeped by Colloidal Silica in Triaxial Testing

“…% is above this threshold of colloidal silica concentration. Previous literature has shown that, for Portland-cement-based matrix, with the increase of carbon nanotube content there are three possible trends in the compressive strength: (1) the compressive strength remains unchanged or even decreases [33,34]; (2) the compressive strength increases [35][36][37][38][39][40][41][42]; or (3) the compressive strength increases first and then decreases [43][44][45]. Our study shows similar trends in carbon-nanotube-reinforced sand-gel composites, and such trends depend on the concentrations of colloidal silica, as shown in Figure 5: (1) at 10 wt.…”