Laboratory And Centrifuge Model Tests Study On Full Flow Penetrometers

As a new type of strength investigation tool risen in recent years, the full-flow penetrometer was widely used in foreign marine soft soil in situ tests and centrifuge model test. The research status of full-flow penetrometers and the development history of centrifuge model tests were reviewed and summarized. Based on the basic principles of full-flow penetrometers and geotechnical centrifuge model tests, laboratory floor tests and centrifuge model penetration tests are performed to compare the full flow penetrometer with other strength testing techniques in the soft soil. The study analyzed the difference between homemade and foreign full-flow penetrometers, the effects of the penetration rate and the probe size on penetration resistance and a variety of penetrometer resistance factor ranges. The result suggested as followed:(1) The homemade strain-gauge full-flow penetrometer needs to be improved considering its discrete test results, and the foreign full-flow penetrometer can be replaced by the loadcell penetrometer on account of both consistent results in centrifuge model tests.(2) Contrast to different undrained shear strength tests, the result of full-flow penetrome-ters showing a high stability and accuracy is closer to micro-penetrometer’s. larger than the shear strength of cone penetrometer test followed by direct shear test and triaxial compression test and smaller than vane shear strength.(3) Centrifuge model test results show that:The penetration resistance of the full-flow penetrometer increases with the increasing penetration rate and decreasing probe size; Cone penetration resistance is significantly affected by the penetration rate and probe size, respectively, measured more accurately at the penetrometer rate of lmm/s or the cone diameter of19.5mm.(4) The experimental solution ranges of T-bar and spherical full-flow penetrometer resistance factors are9.8to10.6and10.7to11.1respectively, which is smaller than the cone factor’s, with smaller degree of scatter. It is of utmost importance and necessity to summarize and analyze resistance factors of different shapes of penetrometers, in order to evaluate effectively the characteristics of the regional soft soil when guiding the penetration tests to compute the shear strength.