THE EFFECTS OF WATER-SATURATED SAND-FRACTIONS ON THE SAND-BOILING PHENOMENON
Keywords:Relative density, Sand fraction, Very loose sand, Upward flow, Effective stress
Understanding the stress distribution behaviors along a soil cross-section have been the challenging topics in geotechnical engineering for the last two decades. Stress analysis by considering saturated sand without upward flow of water has been well studied. However, stress analysis in saturated sand-fraction with upward flow of water, which causes the sand-boiling phenomenon still needs a better understanding. In this paper, the relative density is used to indicate the denseness and looseness of sand fraction. The sand-boiling behaviors are then investigated through two scenarios. The first scenario uses a fine sand-fraction, called the FS scenario. The second scenario uses a mixture of coarse and medium sand-fractions, called the CS-MS scenario. For the FS scenario, the fine sand-fraction only consists of one layer, while for the CS-MS scenario, it consists of two layers where the coarse sand-fraction is above the medium one. The use of the relative density values of the fine sand, medium sand, and coarse sand in both scenarios are 7.6%, 12.4%, and 5%, respectively. As a result, all sand fractions used are categorized as very loose sand because their relative densities are less than 15%. The FS scenario shows that the effective stress is equal to zero obtained within 10 seconds at a depth of 0.12 m under the ground surface. This indicates that the sand boiling has occurred in the FS scenario. Whereas in the CS-MS scenario, the variation of effective stress with depth for a soil layer with upward seepage has a value greater than zero. This indicates that the sand boiling never occurred in the CS-MS scenario. Furthermore, both scenarios also show that the addition of coarse sand-fraction above medium sand-fraction could prevent the sand-boiling phenomenon.