Abstract
Dynamic resistance, which can be used to express strength in the unit of stress and improve the reliability of the dynamic cone penetration test (DCPT), has been estimated by numerous methods. This study aims to compare different dynamic resistance estimation methods by using an instrumented dynamic cone penetrometer (IDCP). DCPTs are conducted using a standard dynamic cone penetrometer (DCP) and IDCP in the laboratory and field. Dynamic responses are obtained from the strain gauges and an accelerometer installed at the cone tip of the IDCP. The test results show that dynamic resistance is more efficient in distinguishing profiles than the dynamic cone penetration index. Among the methods to estimate the dynamic resistance at the cone tip, the force-velocity integration method and force integration method are more related to the conventional dynamic resistance considering the potential energy of the hammer than the force squared integration method. Additionally, the dynamic resistance estimated for a longer time period is more reliable, particularly for small driving rod lengths. Regarding the limitation of the dynamic response from an accelerometer in a previous study, the force-based dynamic resistance estimated for a longer time period can be used as the most reliable approach for further soil strength characterization.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
This study mainly considered an instrumented dynamic cone penetrometer (IDCP) to compare the dynamic resistances estimated by different methods
Strain gauges and an accelerometer were installed at the cone tip of the IDCP
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The dynamic cone penetration index (DCPI), which is a strength profiling index from the DCP test, has been widely correlated with several engineering properties such as the California bearing ratio (CBR) and deflection modulus [6,7]. Previous studies examined the factors of energy loss and explored methods to obtain more reliable profiling results [12,13]. Byun and Lee [2] reported that the energy transferred at the cone tip could be evaluated by installing an energy module composed of strain gauges and an accelerometer. Kianirad et al [18] installed strain gauges at the cone tip to obtain the force signal, and to estimate the dynamic resistance. This study compares different dynamic resistance estimation methods during DCP tests. The estimated dynamic resistances are compared to investigate the effect of each factor, which are assessed by correlation analysis to determine the reliability
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