Instrumented impact cone penetrometer

Dayal, Umesh (1974) Instrumented impact cone penetrometer. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (39MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

This thesis deals with the formulation of an analytical model applicable to low velocity impact penetration problems of soil media and the development of an instrumented impact cone penetrometer for measuring in situ strength properties of soil targets. -- A penetration theory based on momentum considerations is developed for a cone-tipped right circular cylinder impacting on a C-o soil target. A relationship is established between the instantaneous velocity, various 'static' and 'dynamic' soil properties, penetrometer characteristics and the instantaneous depth of penetration. It is assumed that impact causes shear failure and the resistance to the motion of penetrometer is provided by the inertial resistance of the accelerated soil mass plus the dynamic soil resistive force distributed over the base and shaft of the penetrometer. The soil resistive force is calculated on the basis of plastic theory modified for 'dynamic' conditions and extending the previous analysis for the ‘static' condition. The relationship obtained , in addition to providing the velocity profile and the maximum depth of penetration, can also be used for estimating the 'static’ soil strength properties although only under idealized conditions. -- The penetrometer utilised, in addition to providing acceleration signatures (as obtained by previous investigators), is capable of recording cone thrust and local side friction simultaneously and continuously. The available test results indicate that with this system the ‘dynamic ‘strength profile, the soil type, location, and depth of different layers can be directly evaluated up to the penetrated depth. The procedure is outlined for estimating the static in situ strength profile from the 'dynamic' strength profile. The experimental results obtained in the laboratory under fully controlled conditions are in good agreement with proposed theoretical model. -- Tests conducted on terrestrial soils with a penetrometer developed for shallow depth exploration in marine environment demonstrate the potential value testing of the proposed instrument for in situ testing of marine sediments. Finally, the conceptual description of a marine impact penetrometer suitable for exploring great depths is discussed briefly.

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