Miniature Piezocone Test Results in Cohesive Soils   Dae-Kyu Kim Assistant Professor, Department of Civil and Environmental Engineering, Sang-Myung University, San 98-20, AnSeo-Dong, Choen-An, Korea e-mail: daekyu@smu.ac.krand and Mehmet T. Tumay Georgia Gulf Distinguished Professor, Associate Dean for Research & Graduate Studies, College of Engineeringg, Louisiana State University, Baton Rouge, LA, 70803, USA e-mail: mtumay@eng.lsu.edu
			ABSTRACT

The effects of penetration rate and filter element locations on the miniature piezocone penetration and dissipation test results were experimentally studied. Ten piezocone tests were conducted utilizing U_tip (filter element at the cone tip) and U₂ (filter element 1 mm above the cone base) miniature piezocone penetrometers. The calibration chamber tests were conducted on normally consolidated and heavily over-consolidated K33 specimens that consisted of a mixture of 33 % kaolin and 67 % fine sand, under K_o conditions. The tests were performed at penetration rates of 0.3 cm/sec, 0.6 cm/sec, and 2.0 cm/sec.

The excess pore water pressure and corrected net cone resistance increased with the increase in penetration rate. The excess pore water pressure generated during penetration at U_tip was larger than that at U2. The immediate (instantaneous) drop of excess pore water pressure at Utip and U2 locations, when penetration was arrested for pore pressure dissipation, was clearly identified using a digital oscilloscope. The magnitude of the instantaneous drop in excess pore pressure affects the so-called “initial” pore pressures, and was influenced by pore pressure element location, rate of penetration, and state of stress.

KEYWORDS: calibration chamber; miniature piezocone; penetration rate; dissipation; instantaneous pore pressure drop, granolumetry.

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