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.
Fundamental Parameters of Cement-Admixed Clay—New Approach
The fundamental parameters such as after-curing void ratio (eot) and cement content (Aw) have been found sufficient to characterize the strength and compressibility of cement-admixed clay at high water contents. From analyses performed on the results of unconfined compression tests, the ratio eot/Aw has been proven to combine together the influences of clay water content, cement content, and curing time on the strength of cement-admixed clay. Moreover, the results of oedometer consolidation tests revealed that while Aw governs the position of the postyield compression line, the magnitude of eot determines the magnitude of the one-dimensional vertical yield stress σvy′ at particular Aw. The value of eot reflects, primarily, the clay water content and, secondarily, the cement content and the curing time. Normalizing the after-curing unit weight, after-curing water content, and after-curing specific gravity were incorporated in an empirical relationship of eot.
BEARING CAPACITY OF PLANE-STRAIN FOOTINGS ON LAYERED SOILS
A study has been carried out of the bearing capacity of sand layers overlying clay soils for the case where the thickness of the sand layer is comparable to the width of a rigid foundation placed on the soil surface. A review of previous work is given and a discussion is presented of the dimensionless groups that govern the behaviour of this type of foundation. A parametric study is carried out using both finite element and finite difference methods. This study is based on the use of soil parameters obtained from an assessment of the range of values that might be expected to be appropriate for full-scale structures. The results of the parametric study are used to illustrate the mechanics of the system and also to develop charts that may be used directly in design. In particular, the results illustrate that the shear strength of the clay has an important influence on the mechanisms of load spread within the fill. Resume : Lion a rOalisO une Otude sur la capacitO portante de couches de sable reposant sur des sols argileux pour le cas oo liOpaisseur de la couche de sable est comparable ‡ la largeur diune fondation rigide posOe sur la surface du sol. Lion prOsente une revue des travaux antOrieurs et une discussion sur les groupes sans dimension qui rOgissent le comportement de ce type de fondation. Une Otude paramOtrique est rOalisOe en utilisant les mOthodes tant des OlOments finis que des diffOrences finies. Cette Otude est fondOe sur liutilisation des paramtres de sols obtenus en partant de liOvaluation de la plage des valeurs que lion pourrait siattendre ‡ trouver dans des structures ‡ pleine Ochelle. Les rOsultats de liOtude paramOtrique ont OtO utilisOs pour illustrer le mOcanisme du systme et aussi pour dOvelopper des abaques qui peuvent Œtre utilisOes directement dans la conception. En particulier, les rOsultats illustrent que la rOsistance au cisaillement de liargile a une influence importante sur les mOcanismes de rOpartition de la charge ‡ liintOrieur du remblai. Mots clOs : capacitO portante, sols multicouches, analyse numOrique. (Traduit par la rOdaction)