Vibrocoring technique in the nearshore placer exploration programme along Konkan Coast, Maharashtra

Abstract

As a part of nearshore placer exploration along Konkan Coast, Maharashtra (west coast of India) a detailed vibrocoring was carried out using different types of vibrocorers on vessels each equipped with different handling capabilities to map the subsurface zones of placer-rich sands. However, the results are average due to compact nature of sediment, which affected vibrocoring operations and operational limitations of the vessel to cover shallow water stations where most of the placer-rich sand exists. The problems faced during the operations are reviewed and some suggestions are put forth regarding potential modifications for increasing the efficiency of the equipment. An improved model is suggested with frames of two different sizes to tackle different operational water depths (3-8 m and 8-20 m). Special features of the suggested model are stabilizing fins mounted on the base frame to stabilize the vibrocorer against local currents; and an underwater winch for efficient pull-out of the core pipe from the sediment. Advantages gainEd. by using pistons with either cup washers of 'O' rings together with shear pins and a core catcher with length of leaf 1.4 times the diameter of liner to collect undisturbed sediment are stated