In Situ Test of Traffic-Load-Induced Settlement of Alluvial Silt Subsoil Treated by Unslaked Lime

The soft wet alluvial silt is widely distributed material in the world. In order to improve the bearing capacity and decrease the traffic-load-induced settlement of silt subsoil, the shallow subsoil always treats with the unslaked lime. However, the mitigating effect of this ground treatment method on traffic-load-induced settlement of alluvial silt subsoil is inconclusive. Therefore, with the developed falling weight simulation equipment of traffic load, in situ tests are carried out on the natural and unslaked lime treated alluvial silt ground in the Yellow River delta of China to study traffic-load-induced settlement. Furthermore, Chai-Miur cumulative deformation model of soil is employed to numerically simulate the long-term traffic-load-induced cumulative settlement. In situ test results indicate that because unslaked lime treatment enhances wave impedance of the reinforced soil layer, the wheel-load-induced dynamic stress and excess pore water pressure in the substratum decreases. The decrease of excess pore water pressure reduces the cumulative settlement of unslaked lime treated subsoil. For short-term cumulative settlement, there are differences between tested and calculated results, but not much. The calculated results imply that after opening to traffic for 10 years, compared with the natural ground, the cumulative settlement of the unslaked lime treated subsoil reduces by about 21%, and the change of transverse slope of pavement induced by cumulative settlement decreases by 1/3. In situ test and numerical calculation results demonstrate that shallow layer treatment with unslaked lime can effectively mitigate the cumulative settlement of alluvial silt subsoil.