Elastic and -mechanical properties of Mrakotin Granite: A comprehensive laboratory study

This study presents a comprehensive laboratory analysis of the elastic and mechanical properties of Mrakotin Granite (MG), a high-quality granitic rock from the Czech Republic known for its strength, frost resistance, and low porosity.A range of experiments was conducted, including porosity and permeability tests, tensile and compressive strength measurements, ultrasonic velocity analysis, and evaluations of both static and dynamic elastic moduli.Results confirm that MG is a highly low-permeability material (Φ < 0.9 %) with high uniaxial compressive strength (UCS ≈ 180 MPa), making it highly suitable for geotechnical and geophysical applications such as hydraulic fracturing studies.Ultrasonic measurements under confining pressure revealed moderate elastic anisotropy at low pressure (ka ≈ 9 %), which decreases with increasing pressure (ka ≈ 3 % at 120 MPa), indicating microcrack closure and a transition from crack-dominated to matrix-dominated behaviour.Young's modulus increased by up to 80 % under pressure, and the measured static and dynamic elastic moduli are consistent with reported values for other granitic rocks.In conclusion, Mrakotin Granite demonstrates a highly homogeneous structure, mechanical stability, and excellent elastic properties, making it a promising material for demanding engineering purposes and advanced geophysical research.