Research on collapsible sand under plate load test in Luanda, Angola

The collapsible sand (Quelo sand), which occurs widely in Luanda of Angola, is sensitive to water content with the properties of soften and may causes collapsible deformation during soaking. Due to the lack of relevant data and engineering experience, it is difficult to evaluate the engineering properties of the collapsibility and bearing capacities. In this paper, the characteristics of the collapsible deformation and bearing capacities of Luanda Quelo sand are measured and studied by the plate load test (PLT) under the natural and soaking conditions. The experimental results show that the Quelo sand is a collapsible soil with slight to moderate collapsibility; the bearing capacity of the Quelo sand is sensitive to moisture. With the increasing moisture content of foundation soil, the bearing capacity will be reduced significantly with slight change in moisture and can make the bearing capacity several times lower than before during soaking. If the Quelo sand becomes saturated, the bearing capacity can be revised by the embedment depth with the coefficient of 1.07 in the design of foundation. Thus, the foundation treatment, which according with the ordinary design theory and using the bearing capacity value under the condition of subsoil moisture change, could conform to the requirements while construction without eliminating all collapse or partial collapse of subsoil.