The Mechanical Response of a Silty Sand Stabilized with Colloidal Silica

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 straining up to at least 5% of double-amplitude axial strain does not influence the undrained shear strength of the stabilized silty sand.

Pengaruh Penambahan Pasir Terhadap Daya Dukung Subgrade Jalan

The performance of flexible pavement is highly influenced by the quality of subgrade material. In Palembang, the foundation soil is usually consisted of clay which is sensitive to change in water content caused by rainfall as well as inundation. This paper presents results of laboratory study on the effect of adding sand to clay to be used as subgrade material for urban roads. California Bearing Ratio (CBR) values were used as indication of strength improvement of the subgrade in unsoaked and soaked conditions. The suitability of the stabilized soil for use as subgrade of pavement construction in response to normal and inundated conditions was further assessed through field verification using Dynamic Cone Penetrometer. Results of both laboratory and field studies indicated that addition of 21% sand by dry weight give the most improvement in terms of CBR value. In this case, the CBR unsoaked increased from 8% to 18% while the CBR soaked increased from less than 3% to 8%. Field verification showed that the CBR of compacted natural soil decreased from 8% to 2% after rainfall while the CBR of the sand stabilized soil decreased from 17% to 8%. Thus the sand stabilized clay is expected to perform adequately even after subjected to rainfall and inundation.