Thermal effect of brittle failure for hard rock tunnel under high geostress and high ground temperature need to be studied urgently; and the calculation analysis related to brittle failure rarely considers thermal effect. Based on the method of thermal-brittle-fine mechanical calculation

the thermal effect of excavation unloading for hard rock tunnel is calculated by using a new constitutive model reflecting the brittle failure of hard rock; and the energy release rate index is also analyzed. Taking the rock pillars of APSE tunnel in Sweden for example

the mechanical response of tunnel excavation is analyzed under different ground temperatures. Then the damage degree of surrounding rock is analyzed under the action of temperature loading. The failure zone

energy release value and stress index are compared under different ground temperatures. The result shows that increased temperature will strengthen the brittle failure because temperature will make rock mass to generate additional thermal stress. The method of thermal-brittle-fine mechanical calculation can reasonably describe the progressive failure process of hard rock. The proposed method reveals the thermal effect of brittle failure for deep hard rock tunnel

and could benefit the stability evaluation for deep hard rock tunnel under high ground temperature.