This paper presents recent in situ and laboratory tests performed on shotcrete liners and test samples. The test were performed with a nondestructive microseismic method called Impact-Echo. Initial investigations at INCO Ltd's Stobie Mine in Sudbury, Ontario, Canada, confirmed the need for the development of a quick and efficient device capable of determining the thickness of the thin liners. The field study shows that the P-wave velocity in shotcrete is critical for the correct assessment of the liner thickness. Laboratory tests were performed on shotcrete samples at McGill University. The in situ tests concentrate on the liner thickness measurements and the laboratory tests focus on the change in P-wave velocity and acoustic impedance over time.