Abstract
The new Radio-isotope density cone penetrometer (Nuclaer Density Cone Penetrometer; ND-CP) has been developed. The gain in robustness of cone shaft is achieved by introducing special steel with high strength to avoid bending and/or broken due to encountering hard stratum with gravels. A set of inclinometers as well as thermometer have been incorporated to ND-CP to confirm the degree of vertical penetration and monitor the temperature around sensors for qc, fs and u. The effect of temperature on measured strain is large enough for the measured values to be corrected, particularly a due consideration is required for cone tip resistance, qc for very soft clays because possible error can not be ruled out for the shear strength derived from qc. The newly developed ND-CP is a so-called double probe type that facilitates an ordinary density probe unit consisting of 137Cs gamma ray source and NaI scintillation detector together with natural gamma ray (background value; BG) detection probe unit consisting only of NaI scintillation detector in one cone. Cost saving has been achieved with the new ND-CP for Tekong reclamation project in Singapore by being free from additional penetration to detect the natural gamma ray in the ground.
