Geoscience Reference
In-Depth Information
Fig. 15.26. Seeping of dyed water into clean sand
Fig. 15.27. Uniformseeping of colloidal silicaliquid intosand withgravel layer
3.2. UNDRAINED TRIAXIAL TESTS ON SANDIMPROVED
BY COLLOIDAL SILICA
Laboratory shear tests were carried out on the effects of colloidal silica on improve-
ment of liquefaction resistance of loose sand (Kabashima and Towhata, 2000; Towhata
andKabashima,2001).Testedspecimenswerepreparedbyreproducingthein-situstress
historyasmuchaspossible;loosewater-saturatedsandwasconsolidatedinacontainerin
a Ko manner under realistic stress levels (Figure15.28), silicate liquid seeped into sand
under the anisotropic consolidation pressure, and then the sand was cured for 5 weeks
undersustainedstress.Curingunderstresswasconsideredimportantbecauseofthepos-
sibility that consolidation and deformation of sand after solidification of grout might
destroybondingwhichwasmadebysolidifiedsilica(Figure15.29).Specimensthuspre-
pared were firstly tested by undrained triaxial monotonic shear; both compression and
extension tests. In Figure15.30, sand which was improved by silicate liquid shows bet-
ter behavior than untreated sand. Furthermore, liquefaction resistance was improved by
colloidal silicaas well (Figure15.31).
One of the study interests lay in the possible breakage of bonding and grouting effects
due to cyclic loading. It was feared that the first strong earthquake may be well resisted
by bonding but cyclic stress during future earthquake would not be. This issue was
