Others have worked on seafloor penetrometers. Sandia Laboratories 

 began development of one in 1970 (Colp, et al. , 1975) and Scott (1970) 

 reported on a mechanical accelerometer for use with an ocean penetrometer. 

 Delco Electronics developed an expendable soil bearing meter for use in 

 the ocean that was similar to an expendable bathythermograph (Robertson, 

 1965). None of these devices was found suitable for the intended use 

 of the expendable penetrometer proposed. Their sizes are too small for 

 the penetration required, and they are not operable to the required 

 water depth. A new approach to obtain the necessary penetration and to 

 function at water depths to 20,000 feet was necessary. 



Approach and Scope 



The development of an expendable penetrometer involved design of 

 two components: a vehicle to transport an instrument to and into the 

 seafloor and an instrument to gather data as the vehicle penetrated into 

 the seafloor. In each of these designs, cost played an important role 

 because the penetrometer was to be expendable. Design of the vehicle 

 was based on theories of hydrodynamics and soil penetration to obtain a 

 size and shape consistent with operational goals. Design of the instrument 

 system was primarily concerned with conceiving the best instrument for 

 gathering data about the vehicle as it penetrated the seafloor and 

 getting the data back to the surface vessel'. 



This report provides a description of the expendable penetrometer, 

 presents its theory of operation, outlines the process of its develop- 

 ment, and documents the results of initial testing. Also presented are 

 discussions of data quality, factors that can affect the data, and plans 

 for additional testing and evaluation. 



DESCRIPTION OF EQUIPMENT 



The tool developed - the Expendable Doppler Penetrometer - utilizes 

 the Doppler principle: a sound source moves in relation to the receiver 

 of the sound emitted. Thus, the velocity of the penetrometer can be 

 measured. The penetrometer consists of two components (Figure 1): 

 (1) a heavy, hydrodynamic, shaped vehicle for speeding the penetrometer 

 to the seafloor and providing the impetus to penetrate the soil, and (2) 

 an accurately controlled sound source system for data measurement. 



The vehicle is a lead-filled, 8-foot-long, 3-1 /2-inch-outside- 

 diameter pipe. A steel hemisphere is welded to the lower end of the 

 pipe forming an efficient hydrodynamic nose. Welded to the upper end of 

 the pipe is a circular steel plate with a center stud for attaching the 

 sound source system. Three equally spaced fins are attached to the pipe 

 at the upper end to provide stability for the falling penetrometer. The 

 total weight of the vehicle is about 355 pounds. 



