Features of interrelations between acoustic quality factor and strength of rock salt during fatigue cyclic loadings

This study considers the results of tested rock salt (halite) samples of the Novomoskovsk deposit (Tula Region, Russia) for cyclic loads. It was established that in uniaxial compression, the acoustic quality factor Q, dynamic elasticity modulus E, and strength σr undergo a non-monotonous change depending on the number of loads N in a stress range from 2 to 5% up to a maximum level of 40, 60, 80% of the initial strength σ0. With γ = 80%, a strength minimum was observed when N = 15, with 40, 60% strength minimum observed when N = 20. The smaller value of γ corresponds to the smaller value of σr. The minimum in the quality factor Q decreased compared to the initial value by 90, 92, 86% for stresses with γ = 40, 60 and 80% respectively. Strength decreased by 42.3, 31.1, 26.5% for γ = 40, 60, 80%. For a strength decrease section with N = 20, we obtained equations relating quality factor and strength: at γ = 40% σr(Q)=4.89ln(Q)+6.91, determination coefficient R2 = 0.76; at γ = 60% σr(Q)=6.70ln(Q)+7.51, R2 = 0.83; at γ = 80% σr(Q)=13.77ln(Q)-21.45, R2 = 0.93. Additional experiments were carried out to support the credibility of the obtained results.