Utilizing Cone Penetration Tests for Landslide Evaluation

Abstract

AbstractPore pressure and shear strength are two important parameters that control the stability of slopes. These parameters can be derived in-situ by cone penetration testing (CPT) with pore pressure measurements. This paper presents the results from three static, vibratory and dissipation CPT profiles deployed into a landslide headwall at Pyes Pa, Bay of Plenty, New Zealand. The landslide strata consist of volcanic ashes and ignimbrites. Studying the stability of slopes in this area using in-situ geotechnical testing is of societal-economic importance since several other landslides within comparable strata caused considerable property damage. Three CPT profiles were collected across the headwall of the slide scar with 2 m spacing in undisturbed sediments using static, vibratory and dissipation test modes. Static CPT results are used to evaluate soil grain size variations, geotechnical parameters of sediments such as shear resistance, probable slip surface and sensitivity of sediments. Liquefaction potential of sediments is assessed using vibratory CPT results. For dissipation tests, the cone remained stationary in the sediment for ∼60 min to monitor pore pressure dissipation at the depths of 6, 9 and 11 m. With the use of pore pressure dissipation data, values of soil horizontal permeability are calculated. The liquefaction probability from static CPT results is compared to liquefaction potential evaluation from vibratory CPT. Last but not least, an unstable soil layer is defined based on static CPT, vibratory CPT and dissipation results.KeywordsCPTLandslideStaticVibratoryDissipation