On the Investigations of Resilient Modulus of Residual Tropical Gravel Lateritic Soils from Senegal (West Africa)

Investigations on the mechanical behavior of compacted gravel lateritic soils have been the subject of several studies. Used as road materials, soils tests were mainly performed using standard tests. Static loads as unconfined compression test (UCT) remain the only engineering approach used. Alternative testing techniques can be chosen as supplementary tests for characterizing pavement materials. These researches were conducted so as to determine the response of these particular and problematic soils in its compacted form with road traffic loads. This paper presents the results of research conducted to investigate the effect of the soil compacity on the resilient modulus of lateritic soils. The influence of the percentage of cement added so as to stabilize each sample at the optimum modified proctor (OPM) State was also determined. Soil big specimens of around 180 mm diameter (with length to diameter aspect ratio of 2:1) were prepared according to the standard procedure described by AASHTO T 307 and then were subjected to repeated load triaxial tests. The models used, analyzed and developed in this paper are mainly the Andrei and the Uzan–Witczak universal model. Test results showed that the specimen compacity has no significant influence on the resilient modulus of the investigated gravel lateritic soils. Soil specimens with variation of the percentage of cement added exhibited the highest resilient modulus values while the specimens with variation of the compacity exhibited the lowest values. The resilient modulus variation seems to be independent of the level of stress.     

Wave-Based Techniques for Evaluating Elastic Modulus and Poisson’s Ratio of Laboratory Compacted Lateritic Soils

A rapid, low-cost evaluation methodology using the wave-based techniques is proposed in this study in order to determine the design parameters e.g., elastic modulus and Poisson’s ratio of the laboratory compacted lateritic soils. Knowing the elastic wave velocities as measured with the wave propagation technique (i.e., a small-strain non-destructive test) and total mass density of the specimens, the elastic moduli and Poisson’s ratio of the soil specimens can be determined. In addition, the unconfined compression test (i.e., a large-strain destructive test) is also performed on the same specimens under the same unconfined testing condition in order to compare the moduli corresponding to different strain levels. The experimental results showed the potentials and limitations of using impulse signal for the determination of the elastic moduli and Poisson’s ratio for laboratory compacted soil specimens from elastic wave propagation techniques.     

Prediction of Unconfined Compressive Strength of Soil–Cement at 7?Days

Unconfined compressive strength (UCS) of cement stabilized bases was collected from a number of highway construction projects in Thailand. Results from the statistical analysis indicated that the most important factors affecting the UCS were the CBR and the water to cement ratio. The UCS was however independent on the dry density. A statistical model was developed in the study to predict the UCS of cement stabilized bases. A model was developed based on the following criteria: (1) the dry density of the sample shall be greater than 95 percent of the maximum dry density based on the modified Proctor compaction, (2) samples shall be soaked for at least 2 h prior to testing, and (3) the CBR shall be measured at 0.1 inch (2.5 mm) penetration.