Estimation of the compression behaviour of reconstituted clays
Abstract The void index is a relative quantity measuring the position of the current void ratio of a clay against the void ratios of the clay at two specific vertical effective stresses (i.e., σv′ = 100 kPa and σv′ = 1000 kPa). Based on this concept, a simple systematic tool is proposed for estimating the compression behaviour of reconstituted clays over a wide range of stresses and water contents. Following the practice of geotechnical engineering computation, the compression behaviour of clays is idealised as linear segments in the Iv ~ lnp′ (or the void index and the mean effective stress) space. Considering the variation in the available data, there are three related but independent models for describing the compression behaviour of reconstituted clays. The accuracy of estimation increases with the level of available data. The proposed estimation is used to simulate the behaviour of a variety of reconstituted clays over a wide range of stresses and water contents. With different levels of available data, the estimation is evaluated on the basis of these simulations. The proposed estimation can take maximum use of available data and provide a simple yet practical tool for calculating the compression behaviour of reconstituted clays and a basic parameter for geotechnical engineering computations, the compression index. An empirical equation for the initial compression index is also suggested and verified.
Modeling compression behavior of cement-treated zinc-contaminated clayey soils
Abstract In this paper, the compression behavior of cement-treated soil with various cement contents and zinc concentrations is presented and modeled by the destructuring framework and the concept of the Intrinsic Compression Line (ICL). The void ratio of a cement-treated sample with Zn contamination is the sum of the void ratio sustained by the intrinsic soil fabric (destructured void ratio) and the additional void ratio due to cementation. The compression index at the pre-yield state, Cs, increases as the Zn concentration increases or as the cement content decreases. At the post-yield state, the additional void ratio is inversely proportional to the effective vertical stress. The rate of reduction in the additional void ratio is controlled by the destructuring index, b. The values for b and yield stress are mainly dependent upon the degree of cementation, which is controlled by the cement content and the Zn concentration. Based on a critical analysis of the test data, a practical (simple and rational) method for assessing the compressibility of cement-treated soil with various Zn concentrations is suggested. The proposed predictive method is useful not only for quickly determining compression curves, with acceptable errors, but also for examining the results of tests on cement-treated zinc-contaminated soil.
Regional strategies for the minerals industries of the states of the SADCC
The SADCC has been in existence for eleven years but little progress has been made in regional coordination of the minerals sector even though this sector is the most important exporter of the region. There is however scope for minerals development at the regional level.