Evaluation of Weathering Effect on Engineering Properties of Sri Lankan Gneissic Rock

Weathering is a natural process common for all kinds of rock types that may occur due to either physical, chemical, or biological reasons. The applicability of rock in different engineering applications has a primary concern with their engineering properties that might have a significant influence from weathering effect. Characterizing such properties based on weathering effect on gneissic rocks of Sri Lanka is essential due to the wide existence and utilization of gneissic rocks. This study was conducted to understand the behavior of engineering properties such as uniaxial compressive strength, durability, hardness, pulse wave velocity, and mineralogical properties of gneissic rock with weathering effect. Engineering properties of gneissic rocks were determined using laboratory tests according to ASTM (American Society for Testing and Materials) for rocks in fresh and weathered states. Results showed that chemical weathering may have influenced gneissic rocks in both Kaduwela and Kudayala quarry sites since Mg percentage has decreased by the weathering effect. Formation of clay minerals with weathering is a significant characterictics of hornblend biotite gneiss in Kaduwela area, rather than the Garnet bearing biotite in Kudayala area. Mechanical properties such as strength and durability decrease when the fresh rocks exposed to weathering. Physical properties such as hardness, and Pulse velocity have decreased in weathered gneissic rock in both areas.