How to Get Geotechnical Informations Making Use of Submarine Drills

Development of Investigation Methods with a Simple Device

Abstract

In this paper, we describe some experimental studies of investigation methods for submarine drills. The experiments were tried with a simple one-bit-run type electrodrill built as a trial in the writers'laboratory.
Mainly two methods are available to get some geotechnical informations making use of these drills.One important method is concerned with core sampling and testing.A rubber sleeve sampler was designed in order to get undisturbed and high recovery cores efficiently in a process of submarine drilling and “double sleeve cores” were obtained.The unique core test system with these cores including X ray radiography, triaxial compression test and ultrasonic velocity measurement was tried and the value for practical usage was well recognized.
The other method is concerned with drilling response.Some measurements for submarine drills were tried in situ.This method is so to speak mechanical logging or sounding.Strength of the foundation can be correlated from penetration rate and coefficient of deformation is estimated from the strength by mutual relation in the soil to soft rock foundation.This value shows only a kind of index for mechanical properties in the hard rock foundation.But this method becomes a very useful especially in weathered or fractured rock foundation which little cores can be obtained.