VARIATION OF ULTRASONIC WAVE VELOCITY WITH SOME ENGINEERING PROPERTIES OF LIMESTONE; A LABORATORY STUDY IN SRI LANKA

Miocene limestone which covers northern and north-western coastal belt of the Island is used as a raw material for various industries but only cement and lime are being used for the construction industry. The author carried out a series of laboratory tests to find out the mechanical properties of limestone in Sri Lanka with the aim of providing literature for the construction industry. The objective of this paper is to indicate the possibility to find out the uniaxial compressive strength of porous limestone using ultrasonic wave velocity. Borehole samples (NX) of limestone were obtained from various drilling sites in Northern Province of Sri Lanka and selected samples were prepared for different laboratory tests after visual observations. The tests were carried out according to ASTM Standards at the geotechnical and materials testing laboratories. The range (and average result) for each property can be mentioned here as porosity 1-15 (6.7) %, ultrasonic P wave velocity 4480-6338 (5730) m/s and uniaxial compressive strength 11-92 (35)MPa. The ultrasonic wave velocity and uniaxial compressive strength of limestone vary with the porosity. Therefore the ultrasonic wave velocity (P wave) of the limestone bedrock measured in the field using seismic methods for short distances can be used to determine the porosity and uniaxial compressive strength indirectly using the relationships. This gives a preliminary idea about limestone bedrock before commence detail investigation for any construction. Ultrasonic wave velocity indicates that limestone in some locations are highly compacted and solid. According to the compressive strength of solid limestone a few story buildings can be constructed on it after a detail investigation. Key words: Limestone, Engineering properties, ultrasonic P-wave velocity, porosity, uniaxial compressive strength, construction.