Measurement of Stiffness of Rock from Laboratory and Field Tests
Measurement of stiffness of rock from laboratory and field tests Naeem O. Abdulhadi & Amjad F. Barghouthi
Arab Center for Engineering Studies (ACES)
ABSTRACT
This paper compares the deformation modulus of rock measured from laboratory and field tests which were carried out as part of the site investigation works for a major project in Irbid, Jordan.
Laboratory resonant column and torsional shear tests were performed at different confining pressures whereas ultrasonic velocity tests were conducted on unconfined rock specimens. In addition, empirical relationships were used for estimating the rock mass modulus employing the results of the uniaxial compression and point load strength tests. Field measurements comprised pressuremeter testing as well as seismic geophysical methods including down-hole and crosshole techniques. The static and dynamic in-situ stiffness measurements were found to be reasonably in good agreement with the laboratory values from the dynamic tests as well as empirical methods for estimating rock mass stiffness from uniaxial compressive strength results.
INTRODUCTION
The modulus of deformation is undoubtedly the geomechanical parameter that best represents the mechanical behavior of rock mass. In particular, when it comes to underground excavations, this modulus becomes indispensable – whatever the type of design approach to be developed.
Laboratory measurements have long been the reference standard for determining the mechanical properties of geomaterials. In addition, field tests to compliment the geotechnical investigation and laboratory testing has become an expedient and cost-effective way to determine the strength and stiffness parameters over an entire site.
The main purpose of this paper is to present and compare the stiffness obtained from static and dynamic tests determined in the laboratory and field from a comprehensive and integrated site investigation which was carried out by Arab Center for Engineering
Arab Center for Engineering Studies (ACES)
ABSTRACT
This paper compares the deformation modulus of rock measured from laboratory and field tests which were carried out as part of the site investigation works for a major project in Irbid, Jordan.
Laboratory resonant column and torsional shear tests were performed at different confining pressures whereas ultrasonic velocity tests were conducted on unconfined rock specimens. In addition, empirical relationships were used for estimating the rock mass modulus employing the results of the uniaxial compression and point load strength tests. Field measurements comprised pressuremeter testing as well as seismic geophysical methods including down-hole and crosshole techniques. The static and dynamic in-situ stiffness measurements were found to be reasonably in good agreement with the laboratory values from the dynamic tests as well as empirical methods for estimating rock mass stiffness from uniaxial compressive strength results.
INTRODUCTION
The modulus of deformation is undoubtedly the geomechanical parameter that best represents the mechanical behavior of rock mass. In particular, when it comes to underground excavations, this modulus becomes indispensable – whatever the type of design approach to be developed.
Laboratory measurements have long been the reference standard for determining the mechanical properties of geomaterials. In addition, field tests to compliment the geotechnical investigation and laboratory testing has become an expedient and cost-effective way to determine the strength and stiffness parameters over an entire site.
The main purpose of this paper is to present and compare the stiffness obtained from static and dynamic tests determined in the laboratory and field from a comprehensive and integrated site investigation which was carried out by Arab Center for Engineering
References: ASTM (1997) Standard Test Method for Pulse Velocity Through Concrete, ASTM C 597-97. ASTM (2000) Standard Test Methods for Crosshole Seismic Testing, ASTM D 4428/D4428M00. West Conshohocken, PA: ASTM International. ASTM (2007) Standard Test Methods for Prebored Pressuremeter Testing in Soils, ASTM D 4719-07 BSI (1986) Code of Practice for Foundations, BS 8004:1986. Milton Keynes: British Standards Institution. BSI (1986) Testing Concrete – Part 203: Recommendations for Measurement of Velocity of Ultrasonic Pulses in Concrete, BS 1881-203:1986 Burland, J. B. (1989) Small is Beautiful: The stiffness of Soils at Small Strains. Ninth Laurits Bjerrum Lecture Clayton, C.R. (2011) Stiffness at Small Strain: Research and Practice. Fiftieth Rankine Lecture, Geotechnique, 61, No Hoek, E. & Brown, E.T. (1997) Practical Estimates of Rock Mass Strength. International Journal of Rock Mechanics and Mining Science, 34(8), 1165-1186.