Mechanical response and damage constitutive model of early-age cemented paste backfill after cyclic loading

Abstract

During mining operations, cemented paste backfill (CPB) is damaged in real time by different loading gradient, loading rate and loading time. And there is variability in the degree of damage and destruction of CPB by different loading conditions. This paper carries out uniaxial compression and ultrasonic velocity tests to investigate the uniaxial compressive properties and damage characteristics of CPB after cyclic loading. The results show that when the loading rate is 1.3 mm min−1, the loading gradient is σ0.5 and the loading time is 300 s, the uniaxial compressive strength (UCS) of CPB at 3, 5 and 7 days of curing age is the maximum, and the values are 1.7335, 4.0325 and 6.5301 MPa, respectively. The value of ultrasonic velocity variation is exponentially related to that of UCS. The CPB dissipation energy (DE), elastic strain energy (ESE), and unit volume strain energy (UVSE) improved with curing age raising. Under the age of 3 d, 5 d and 7 d, the failure mode of CPB is X shear- X-conjugate shear - Y shear. The correction coefficient α and coefficient of compaction η were introduced, and the two-stage damage constitutive model of CPB after cyclic loading was constructed based on the Weibull distribution, with the model validated. The magnitude of the correction coefficient α affects the peak strength and the residual stress duration strain length of the model, and has less effect on the damage development. When the value of α ranges from 0.90 to 0.92, the model curve is closer to the test curve.