Study on macro-meso damage model of sandstone with open cracks under the coupling action of freeze-thaw and load#br#
LV Siqing,ZHU Jiebing,WANG Bin,ZHU Yongsuo
(Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources,Changjiang River Scientific Research Institute,Wuhan,Hubei 430010,China)
摘要The evolution law of rock damage at macro and meso scales is the basis for evaluating the degradation process of mechanical properties of frozen rock. In this paper,the calculation method of macroscopic damage variable is proposed based on weighing method from the perspective of the volume of open fractures. Combined with the variation characteristics of rock composition and physical and mechanical properties under long-term freeze-thaw cycles,the difference of open porosity was reasonably corrected,and the meso-damage variables under freeze-thaw action were obtained. Considering the compaction characteristics of initial pores and cracks under load,a calculation model of mesoscopic damage variable under load is established by using statistical damage mechanics. The macro-meso coupling total damage is calculated by the macro-meso total damage calculation method based on Lemaitre strain equivalent hypothesis. According to the extended strain equivalence principle,the total damage constitutive model considering the influence of initial compaction section is constructed. In order to verify the rationality of the model,the prefabricated fractured sandstone samples with dip angles of 0°,30°,45°,60° and 90° and the intact sandstone samples were used to carry out the test of physical and mechanical properties after multiple freeze-thaw cycles. The research results show as follows. When the number of freeze-thaw cycles is small,the freeze-thaw damage variables increase rapidly,and the freeze-thaw damage variables gradually tend to be stable and increase slowly with the increase of the number of cycles. The influence of dip angles of fractures on the expansion of micro-pores and micro-fractures in sandstone rock samples is reflected in the different growth rates of damage variables. The increase rate of freeze-thaw damage variable of rock samples with 45° dip angle is the largest,and the expansion rate of micro-pores and micro-fractures of rock samples with 45° dip angle caused by frost heaving force is the fastest. The damage evolution curve of meso total damage model and macro-meso coupling total damage model tends to be consistent,and the coupling effect of freeze-thaw and load is the main source of damage and deterioration of sandstone samples in this test. The variation trends of macro-meso total damage test values of strains at the peak stresses are similar to those of theoretical calculation values,and the proposed theoretical model can reasonably describe the mechanisms of damage and degradation of fractured sandstone.
Abstract:The evolution law of rock damage at macro and meso scales is the basis for evaluating the degradation process of mechanical properties of frozen rock. In this paper,the calculation method of macroscopic damage variable is proposed based on weighing method from the perspective of the volume of open fractures. Combined with the variation characteristics of rock composition and physical and mechanical properties under long-term freeze-thaw cycles,the difference of open porosity was reasonably corrected,and the meso-damage variables under freeze-thaw action were obtained. Considering the compaction characteristics of initial pores and cracks under load,a calculation model of mesoscopic damage variable under load is established by using statistical damage mechanics. The macro-meso coupling total damage is calculated by the macro-meso total damage calculation method based on Lemaitre strain equivalent hypothesis. According to the extended strain equivalence principle,the total damage constitutive model considering the influence of initial compaction section is constructed. In order to verify the rationality of the model,the prefabricated fractured sandstone samples with dip angles of 0°,30°,45°,60° and 90° and the intact sandstone samples were used to carry out the test of physical and mechanical properties after multiple freeze-thaw cycles. The research results show as follows. When the number of freeze-thaw cycles is small,the freeze-thaw damage variables increase rapidly,and the freeze-thaw damage variables gradually tend to be stable and increase slowly with the increase of the number of cycles. The influence of dip angles of fractures on the expansion of micro-pores and micro-fractures in sandstone rock samples is reflected in the different growth rates of damage variables. The increase rate of freeze-thaw damage variable of rock samples with 45° dip angle is the largest,and the expansion rate of micro-pores and micro-fractures of rock samples with 45° dip angle caused by frost heaving force is the fastest. The damage evolution curve of meso total damage model and macro-meso coupling total damage model tends to be consistent,and the coupling effect of freeze-thaw and load is the main source of damage and deterioration of sandstone samples in this test. The variation trends of macro-meso total damage test values of strains at the peak stresses are similar to those of theoretical calculation values,and the proposed theoretical model can reasonably describe the mechanisms of damage and degradation of fractured sandstone.
吕思清,朱杰兵,汪 斌,祝永锁. 冻融荷载耦合作用下含开口裂隙砂岩宏细观损伤模型研究[J]. 岩石力学与工程学报, 2023, 42(5): 1124-1135.
LV Siqing,ZHU Jiebing,WANG Bin,ZHU Yongsuo. Study on macro-meso damage model of sandstone with open cracks under the coupling action of freeze-thaw and load#br#. , 2023, 42(5): 1124-1135.
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