Test on Mechanical Properties of Cemented Soils Using Secondary Development Data Acquisition Test System
A secondary development of computer aided data acquisition test system is performed in order to improve the disadvantages of original system. In this way, the qualified influences of cement content and curing time on yield strength and stiffness of soil can be automatic acquisition in consolidated undrained triaxial tests. The data collected from the system show that the deviatoric stress of soil increases with increasing axial strain initially followed by a relatively smooth decline after yield point. Yield strength increases with increasing cement content and curing time at the same strain. A well-defined linear relationship between yield strength and cement content are observed and also the relationship between yield strength and curing time. Finally, a linear function is defined to express the linear relationship between yield strength and those two factors and corresponding linear coefficients are obtained through a multiple regression analysis of test data. Stiffness of specimens shows an initial sharp degradation followed by smooth attenuation with increasing axial strain. The addition of cement and long curing time can effectively improve the stiffness of specimens especially at low strain areas.
Strength Properties of Sandy Soil–Cement Admixtures
Soil stabilization with cement is a good solution for the construction of subgrades for roadway and railway lines, especially under the platforms and mostly in transition zones between embankments and rigid structures, where the mechanical properties of supporting soils are very influential. These solutions are especially attractive in line works where other ground improvement techniques are extensive and, therefore, very expensive. On the other hand, the economic and environmental costs of such works should be optimized with good balances between excavation and embankment volumes. For this purpose, the improvement of locally available soils can bring great advantages, avoiding a great amount in borrowing appropriate material, as well as the need of disposing huge volumes in deposits. This paper focus on the characteristics of two soils, Osorio sand and Botucatu residual sandstone, which can be converted to well acceptable materials for this purpose, if stabilized with cement. The study of soil stabilization with cement relies on the quantification of the influence of percentage of cement and porosity adopted in the admixing process for different state and stress conditions. This influence will be evaluated from the analysis of unconfined compression strength (UCS or qu) test results. This experimental framework will enable a good definition of mechanical parameters used in design of foundations and subgrades of railways platforms and for their execution quality control.
Interpretation of undrained self-boring pressuremeter test results incorporating unloading
An interpretation method has been developed to incorporate nonlinear soil behavior to interpret undrained pressuremeter test results. The method makes use of both the loading and unloading portions...