Land-based Vibracoring and Vibracore Analysis: Tips, Tricks, and Traps

Abstract

"INTRODUCTION: Vibracorers have seen increasing since they were introduced in the 1960's. Once a tool of research vessels and institutions along ocean coastlines (Pierce and Howard, 1969; Lanesky and others, 1979; Hoyt and Demarest, 1981; Finkelstein and Prins, 1981), small, portable vibracorers are now used on coastlines throughout the world and in many nonmarine settings (Smith, 1984). Their proliferation is a result of the vibracorers' low construction, field cost, and portability, the relatively undisturbed samples they obtain and moderate depths to which they penetrate.

Most vibracorers are based on the design of Lanesky and others (1979) and Finkelstein and Prins (1981). Both designs use a concrete vibrator to set up an oscillation in a piece of aluminum irrigation pipe. The base of the core tube liquifies the underlying sediment, and the core tube sinks into the ground under its own or added weight. All vibracoring systems require the water table to be at or near the ground surface. Consequently, most vibracorers are used at the margins of water bodies, and in or near wetlands along floodplains and coasts.

Personnel at the Indiana Geological Survey (IGS) have used a vibracorer since 1985. More than 200 cores have been collected in coastal, fluvial, and wetland sediments of northwestern Indiana. The cores constitute a valuable data set for describing the shallow subsurface geology of the area and determining the depositional history of Lake Michigan (Thompson, in press). Other cores of slurry-pond sediments have been collected in southwestern Indiana. There, the vibracorer was used to sample fine-grained coal refuse and to install shallow monitoring water wells.

This paper describes the IGS vibracorer and vibracoring techniques. Most vibracorers can collect an undisturbed sample of a variety of sediment types, including sand, silt, and peat, in a range of depths from 10 to 25 feet. Problems encountered with vibracorers (poor penetration and recovery) can be overcome. We present numerous tips and pitfalls in constructing a vibracorer and maximizing core recovery."