m INEXPENSIVE, PQRTABLE VIBRACORING SYSTEM 

 FOR SHALLOW-WATER AND LAND APPLICATION 



by 

 Kenneth Finkelstein and Dennis Prins 



1 . INTRODUCTION 



Vibratory coring devices have been used for the past three decades to 

 obtain relatively undisturbed cores of unconsolidated sediments. Initially, 

 pneumatic coring systems deployed from ships and barges were designed to obtain 

 cores on the Inner Continental Shelf (Tirey, 1972; Meisburger and Williams, 

 1980). Several smaller portable vibrating coring devices have been developed 

 that successfully recover cores in beach and back-barrier environments by small 

 boat or vehicle. Sanders and Imbrie (1963) and Pierce and Howard (1969) de- 

 signed systems that recover cores less than 12 feet (3.6 meters) long. Hoyt 

 (1979) and Lanesky, Logan, and Hine (1979) developed efficient portable coring 

 apparatuses to obtain cores up to 36 and 43 feet (11 and 13 meters) long, 

 respectively. 



To improve efficiency and safety, the Coastal Engineering Research Center 

 (CERC) used modifications of existing coring systems to design a portable 

 vibrating coring system for use in a sedimentation study of barrier islands. 

 The essential components (see Table for equipment specifications) typify other 

 portable vibrating coring designs: a gasoline-powered concrete vibrator, a 

 3-inch-diam.eter (7.6 centimeters) aluminum irrigation pipe 33 feet (10 meters) 

 long, a 14-foot- high (4.3 meters) tripod with two come-alongs, and a gas-main 

 sealer plug. The advantages of this design over previous systems include the 

 easy assembly and the sturdiness of the tripod, which permits efficient, safe, 

 yet rapid extraction of cores 33 feet or greater in length, and a quick fasten- 

 release clamp to attach the vibrator head to the coring pipe. A method was 

 also devised to extract less than 10-foot (3 meters) cores without the use of 

 the 14-foot tripod. The entire coring system weighs about 220 pounds (100 kilo- 

 grams) , and the total cost to fabricate and assemble the apparatus and purchase 

 the core tubes is less than $1,000 discounting labor. The coring procedure may 

 be accomplished entirely by two individuals, though three are desirable. This 

 system is not intended for subsurface strength or density tests. 



II. PRIMARY COMPONENTS 



1. Vibrator . 



A Briggs and Stratton 4-horsepower 4-cycle gasoline engine designed for use 

 as a concrete vibrator is used as the power source of the coring system (see 

 the Table for equipment specifications). The engine vibrator unit (Fig. 1) 

 weighs 110 pounds (50 kilograms) and is assembled on a 360° swivel base. A 

 13-foot-long (4 meters) flexible shaft leading to the vibrator head is a stand- 

 ard attachment to the engine. However, an extra 13 feet of extension shaft 

 is recommended so that the vibrator head can be attached as high as possible on 

 the 33-foot coring pipe. This improves the system in two ways: (a) The vibra- 

 tor head does not need to be moved up the core barrel until about 20 feet (6 

 meters) of pipe has penetrated the sediment. Momentum is very important in 

 retrieving long cores. Reattaching the vibrator head one time is usually 

 unavoidable, but making several reattachments is detrimental to achieving deep 



