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In order to ascertain the effectiveness of the California bearing ratio test also known as the CBR test on saturated clays, an analysis has been carried out using finite element analysis.
The CBR Test is basically a penetration test and the aim was to evaluate if the test correlated consistently with stiffness or strength of the clays.
It has been shown that the CBR test does not consistently correlate with either stiffness or strength and the CBR only reflects undrained strength.
There are however problems using finite element analysis to predict the bearing capacity as the estimate obtained is neither an upper or lower value and can be inaccurate due to the presents of locking. To reduce inaccuracies, it is advised to avoid using low order formulations unless combined with selective integration.
The final bearing capacity of a footing resting on a sand layer placed over clay obey an associated flow rule and the finite element solutions presented results that fell inline within +/- 10%
If you have a high-water content in the clay it can be necessary to stabilise the cays mechanical properties with the addition of slaked lime. It was found that the addition of around 4% lime produced the best results with CBR value going from 6.3 to 8.7
The CBR values also increase over time with curing having an increased effect after 28 days to 175 days.
Adding lime as a stabiliser increased the CBR value of Clay significantly more than that of soil and curing times over 28 days increased this further.