Mechanical behavior and constitutive model of shotcrete–rock interface subjected to heat damage and variable temperature curing conditions

Abstract

The hydration of shotcrete under a high curing temperature is usually accompanied by the evolution of internal defects and microdamages. To study the physical and mechanical properties and the performance of the bond between shotcrete and rock in a high and changing temperature environment in tunnel construction, shear experiments on shotcrete-rock specimens under different initial curing conditions (60 ℃, 80 ℃, 100 ℃ with relative humidity of 55%) were conducted. The results indicated that the shotcrete used in a high geothermal tunnel was actually cured under high and variable temperature, which caused the damage in the micro-unit of shotcrete near the contact face and, to different extents, the reduction in strength of the interface. The main reason is that high temperatures have a significant impact on the quantity and distribution of the shotcrete hydrates, and they also lead to the formation and increase of micro cracks. However, the increase in normal stress had a certain inhibitoryeffect on the damage caused by the high temperature. Specimens under different normal stresses and initial curing temperatures exhibited two typical failure modes. Moreover, the stress–strain curves were also obtained and used to calibrate the parameters of the proposed thermal damage constitutive model. The research results may provide some supports for the design and analysis of underground engineering affected by high geothermal.