海南北部玄武岩实时温度单轴拉-压强度试验研究OA北大核心CSTPCD

The north part of Hainan Province has widely distributed,abundant basaltic rocks providing a great potential for carbon geological sequestration via mineralization.Engineering practice of carbon sequestration in subsurface basalt requests to understanding of the mechanical properties of basalt at real-time temperature.In this study,Brazilian splitting and uniaxial compression experiments were performed on late Cenozoic basalt samples(mainly minerals including Augite,Al-rich,and Anorthite)collected from northern Hainan Province under real-time temperature conditions of 25-250℃,to investigate the effects of temperature on the strength and failure characteristics of the basalt samples.The Brazilian splitting tests show that the tensile strength of the basalt samples reduced from～13 MPa at room temperature to～8 MPa at 50℃,and finally to～7 MPa at 250℃,accompanied by a dominant fracture surface.The uniaxial compression experiments determine the Young's modulus and Poisson's ratio of 31.0-175.3 GPa and 0.13-0.48,respectively,having the maximum values at temperatures of 100-150℃.The compressive strength of 77.5-159.5 MPa decreases slightly with temperature but is associated with larger discreteness.The basalt samples upon uniaxial compression exhibited shear failure along a single plane at temperatures of 25-100℃,while shear failures along multi-planes at temperatures of 150-250℃.This may be attributed to the increase of the proportion of tensile microcracks upon temperature rise during the microcracking process.Combining the results from both experiments,the tensile strength reduction and the scattered uniaxial compression mechanical parameters observed at temperatures of 25-250℃are likely dominated by the thermally activated rate process,rather than the thermal damage mechanism.From a perspective of temperature-dependent mechanical properties of the collected basalt samples,this study implies that deep burial depth(higher temperature)favors the carbonation reaction of basalt and CO2,as the reduction of tensile strength may accelerate the fracturing process to enhance the reactive surface between basalt and CO2-rich fluids.Nevertheless,complex deformation and failure mechanisms caused by temperature during in-situ subsurface carbon sequestration in basalt also need serious considerations in future studies.