EFFECT OF STRONG STRUCTURE ON CPTU TEST RESULTS OF ZHANJIANG CLAY AREA

Laboratory consolidation test and CPTU test were conducted to test the effect of soil structure on CPTU test results of Zhanjiang clay area. To do that, response characteristic of CPTU was obtained and the difference between consolidation coefficients evaluated from consolidation test and CPTU test was comparatively analyzed. The results showed that penetration indexes of Zhanjiang clay were relatively high, for instance, qc=(2.5~3.0)MPa, and the average Rf was approximately 1%. High accuracy may be achieved in soil horizon division if CPTU test result was used in areas of strong structured clay. Affected by strong structure, the pore water pressure dissipation time decreased and consolidation coefficient increased with the increase of buried depth of soil. Shear dilatation appeared in the initial stage of pore water pressure dissipation during the test. The Cv evaluated from Zhanjiang clay before structure failure was approximately 10 times the value of the one from remolded soil in laboratory test. Permeability of soil mass around the probe reduced rapidly and index distortion was observed due to the structural damage during the penetration process, consequently, the Cv of undisturbed soil evaluated from CPTU test was much less than that from laboratory test. Taking structure into consideration, a method for estimating Cv of structured clay was proposed based on the CPTU data. The study provided a reasonable scientific basis for accurately obtaining design parameters of foundation treatment in structured clay.