Long Term Cyclic Response of a Soil-Cement Mixture: Experimental Study and Modelling

Soil and granular materials stabilization with hydraulic cements is an interesting solution as stiffness and strength are highly improved. It is especially attractive when high traffic loads with considerable number of passages are expected and high mechanical properties of subgrade soils are required. Furthermore, such improvement allows reducing the amount of natural soils to be disposed for the fact of being rehabilitated, with significant environmental and economic advantages. Many authors have studied the cyclic behaviour of soils and soft rocks and others have studied soil-cement mixtures under static conditions. However, few studies have been published on soil-cement mixtures in cyclic conditions, particularly with a high number of cycles.The purpose of this paper is to analyse the behaviour of some mixtures of cement-treated soil subjected to long term cyclic loading in order to contribute to the identification of rational criteria for design of subgrades for transportation infrastructures. The soil used is a well-graded silty sand remoulded from the weathered horizons of Porto granite, the most common rock in the north-western region of Portugal. The cement added to the soil varied in four percentages from 0 to 7% of mass of the uncemented soil. For each of these cement contents, two specimens were moulded with two initial void ratios. The study included an extensive set of long-duration drained cyclic triaxial tests, performed under stress-controlled conditions using an automatic hydraulic system with cells containing high-precision internal axial and radial strain gauges.The scope of the triaxial cyclic tests is to study the evolution of the accumulation of permanent strain in cemented and uncemented specimens subjected to cyclic loading.