Abstract
Freezing-thawing cycles seriously affect the safety of underground engineering in cold regions. At present, most research studies focus on the effect of number and freezing temperature on freezing-thawing cycles. As another important factor, the mechanism of rock mass water content affecting freezing-thawing is less studied. This paper studied the influence of the water content on mechanical property, microstructure, and acoustic emission characteristics of sandstone. The results indicated that the uniaxial compressive strength (UCS) and elastic modulus (E) of sandstone after 20 freezing-thawing cycles decreased as the water content increased. However, the decreasing rate of UCS gradually decreased, while the decreasing rate of E gradually increased. Furthermore, the empirical formulas of UCS and E about water content were obtained. The porosity and plasticity of sandstone after 20 freezing-thawing cycles increased as the water content increased. The empirical formulas of UCS and E about water content were obtained. The porosity and plasticity of sandstone after 20 freezing-thawing cycles increased as the water content increased. The decreasing trend of UCS with porosity was the same as that of UCS with water content. The failure form of sandstone gradually changed from splitting failure to shear failure. The results of the acoustic emission test showed that the stress-strain curves combined with acoustic emission ring counting could reveal the damage evolution process of sandstone during loading.
Highlights
In cold regions such as northern China, northwestern Iran, and eastern Turkey, the effects of freezing and thawing are experienced every year, which bring huge challenges to local underground engineering
Rock mass is a kind of natural mineral aggregate, containing certain cracks, pores, gas, water, etc. e temperature change will cause the pore water in rock mass to continuously undergo water-ice phase transition. e frost heaving force caused by volume expansion makes the primary cracks and pores in rock develop continuously, fuse and connect, and generate new cracks, which destroy the internal microstructure of rock and lead to the continuous deterioration of rock properties [1, 2]. us, freezing-thawing is a primary reason for the deterioration of rock properties
Mousavi et al investigated the effect of the freezing-thawing cycles on the mechanical properties of schists and showed that the uniaxial compressive strength (UCS), elastic modulus (E), cohesive force, and internal friction angle were decreased exponentially by increasing the number of freezing-thawing cycles [3, 4]
Summary
In cold regions such as northern China, northwestern Iran, and eastern Turkey, the effects of freezing and thawing are experienced every year, which bring huge challenges to local underground engineering. Based on the Lemaitre strain equivalent principle and continuum damage mechanics theory, Lu et al deduced the damage constitutive equation under freezing-thawing cycles and loading, in which pre-existing cracks, confining pressure, freeze-thaw action, and load were considered, and established the damage model to predict the degradation of triaxial compression strength for single flaw sandstone [13]. Chen et al found that when the water content exceeded the critical saturation, the mechanical properties of red sandstone changed significantly and further obtained a model that can predict the damage of red sandstone with different water-bearing states undergoing freezing-thawing cycles [22]. E research investigated the mechanical properties, microstructure, and acoustic emission characteristics of sandstone with different water contents of 0%, 0.58%, 1.06%, 1.82%, 2.43%, and 2.80% under 20 freezing-thawing cycles. E test used 20 freezing-thawing cycles to simulate the freezing-thawing cycles experienced by the actual project during the service life. e influences of the water content on deformation and strength characteristics, pore characteristics, and AE ring count of the sandstone under the freezingthawing cycles were discussed. e research aims to explore how the bearing capacity of tunnel surrounding rock with different water contents changes after several freezingthawing cycles in cold areas and provide information and suggestions for the maintenance of the tunnel project during its use period
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
