Determination of the coefficient of consolidation from independent measurements of permeability and compressibility

One of the important aspects of laboratory consolidation testing is the estimation of coefficient of consolidation (C-v) from which the rate of settlement can be predicted. Several researchers have proposed various graphical methods for obtaining estimates of C-v from laboratory oedometer tests. Literature suggests that the various graphical methods estimate different values for C-v for the same data and hence the only rational way to estimate the C-v value is based on the measured coefficient of volume compressibility (m(v)) and the coefficient of permeability (k). Guided by these considerations, an attempt has been made to establish the feasibilty of estimating C-v using stress-state-permeability relationships. Using these relationships, it is possible to estimate the coefficient of volume compressibility as well as the coefficient of permeability

California bearing ratio test simplified

Due to the large volume of soil sample material and effort involved, the conventional California bearing ratio (CBR) tests are laborious and time consuming. Hence, an attempt was made to use the Proctor mold itself with a proportionately smaller plunger to estimate the CBR values. The good agreement between the CBR values obtained using the conventional mold and plunger and the Proctor mold and a smaller plunger (with a correction factor) suggests the feasibility of this approach, especially for fine-grained soils. The recommended minitest apparatus and procedure make the CBR test much simpler

Permeability and Compressibility Behavior of Bentonite-Sand/Soil Mixes

As a seepage barrier slurry trench material should have a relatively low coefficient of permeability, in the range of 10(-7) cm/s, and at the same time should be compatible with surrounding material with regard to compressibility. Although bentonite-sand/soil mixes are used widely, there is no specific engineering approach to proportion these mixes that satisfies the above practical requirements. In this paper, a generalized approach is presented for predicting the permeability and compressibility characteristics of mixes with minimum input parameters. This approach will be helpful in proportioning mixes and predicting corresponding changes in engineering behavior. It is possible to proportion a mix to arrive at the required compressibility without affecting the permeability. This is explained using an illustrative example