Macro-and meso-scale study on dynamic mechanical properties of shaft lining concrete exposed to high water pressure

Abstract

This study presents the impact dynamic properties and pore structure characteristics of shaft lining concrete after exposure to various water pressure levels and durations, which provides guidance for design and utilization of supporting materials at ingate. The maximum impact pressure was 0.55 MPa, the highest water pressure was 10 MPa and the longest duration was 14 days. Research found that impact pressure remained constant, and water pressure lasted for 1 day, impact strength increased with increasing water pressure, whereas impact strength exhibited a decreasing trend with increasing water pressure when water pressure lasted for a longer time. Water pressure remained unchanged, impact strength exhibited an increasing trend as the impact pressure increased, which was due to strength enhancement of the Stefan effect, inertia effect, and excess pore water pressure formed by water in the specimens under impact load. However, impact strength decreased significantly under the same impact pressure as the water pressure lasted longer. After exposure to water pressure, internal pores of specimens were dominated by micropores and small pores, accounting for more than 88.39%. With the increase in water pressure and its duration, the proportion of macropores gradually increased, and the total number of pores increased rapidly, because pressure water applied splitting load to microcracks and micropores in the specimens to promote their further expansion, accompanied by the generation of new flaws. Results show that impact strength increases when the damage effect induced by microcracks and micropores expansion under water pressure is less than the enhancement benefit under impact dynamic load, and vice versa.