CONE PENETRATION IN VERY WEAKLY CEMENTED SAND

Cone penetration testing in very weakly cemented sands with unconfined compressive strengths of 60 kPa or less is investigated in a calibration chamber. Monterey 0/30 sand is artificially cemented with 1% and 2% portland cement. A miniature electric cone penetrometer that gives a diameter ratio of 42 is used in the chamber. Boundary conditions with zero lateral volumetric strains and a constant vertical stress are used. The tip resistance and the sleeve friction are both found to increase with cementation. The friction ratio is found to be indifferent to the increase in cementation at very weak cementation levels and vertical effective stresses of 50-300 kPa. Tip-resistance values at vertical effective stresses of less than 100 kPa increase over two times and over four times the uncemented values at peak cohesion intercepts of 10 kPa and 30 kPa, respectively. Although the effect of confinement gradually overshadows the influence of any weak cementation, tip resistance at a vertical stress of 300 kPa can still be 15-25% and 40-45% more than the uncemented values at peak cohesion intercepts of 10 kPa and 30 kPa, respectively.