基于PFC^(3D)的裂隙红砂岩冻融破坏特征研究  

Research on freeze-thaw failure characteristics of fractured red sandstone using PFC^(3D)

作　　者：白杰 BAI Jie(China Railway 20th Bureau Group Co.,Ltd.,Xi’an 710016,China;College of Science,Xi’an University of Science and Technology,Xi’an 710054,China)

机构地区：[1]中铁二十局集团有限公司,陕西西安710016 [2]西安科技大学理学院,陕西西安710054

出　　处：《煤炭工程》2025年第2期171-179,共9页Coal Engineering

基　　金：国家自然科学基金青年项目(42401163);陕西省自然科学基金青年项目(2024JC-YBQN-0273)。

摘　　要：为探究冻融与荷载耦合作用下裂隙岩体的损伤劣化机理,针对具有不同裂隙长度的岩石开展了不同冻融循环次数的三轴压缩试验,借助PFC^(3D)数值模拟软件再现室内试验过程,同时对模拟的可靠性加以验证。结果表明:在冻融过程中,小孔的相对含量先增加后减少,大孔的相对含量呈现先减少后增加趋势;围压与预制裂隙对试样力学性能的作用相反,10、20和30 mm预制裂隙对红砂岩承载能力的削弱程度分别为25%、66%、80%;冻融循环导致试样微裂隙扩张,在围压作用下这些裂隙更易在预制裂隙处汇聚。完整试样的破坏形态由张拉破坏向剪切破坏转变,随着围压增加,裂隙岩体均表现为剪切破坏,且裂隙长度不会改变岩体破坏模式;通过引入水颗粒随温度变化的体积本构方程,再现了室内冻融循环试验的全损伤过程。在冻融循环达40次时,岩石内部被充分损伤,裂纹数量成倍增加;PFC^(3D)计算结果显示,完整试样的破坏点首先出现在加载点处,裂隙试样则首先出现在加载点及预制裂隙处,裂纹曲线整体呈“S”形,可分为“缓-陡-缓”三个阶段。预制裂隙长度越长,试样损伤程度越大,抵抗破坏的能力越弱。To explore the mechanism of damage and deterioration of fractured rock mass under the coupling effect of freeze-thaw and load,triaxial compression tests were conducted on rocks with different crack lengths and freeze-thaw cycles.The indoor test process was reproduced using PFC^(3D)numerical simulation software and the reliability of the simulation was verified.The results show that during the freeze-thaw process,the relative content of small pores first increases and then decreases,while the relative content of large pores shows a trend of first decreasing and then increasing;The effect of confining pressure and prefabricated cracks on the mechanical properties of rock samples is opposite.The weakening effect of prefabricated cracks of 10 mm,20 mm,and 30 mm on the bearing capacity of red sandstone is 25%,66%,and 80%;The freeze-thaw cycle leads to the expansion of microcracks in the rock sample,making it easier to converge at the prefabricated cracks under confining pressure.The failure mode of the complete rock sample changes from tension to shear,and as the confining pressure increases,the fractured rock mass exhibits a shear failure mode,and the length of the cracks does not change the failure mode of the rock mass;By introducing the volume constitutive equation of water particles changing with temperature,the entire process of indoor freeze-thaw cycle test damage is reproduced.After 40 freeze-thaw cycles,the interior of the rock is fully damaged,and the number of cracks increases exponentially;PFC^(3D)calculation shows that the failure point of the complete rock sample first appears at the loading point,while the fractured rock sample first appears at the loading point and the prefabricated crack.The overall crack curve presents an“S”shape,which can be divided into three stages:gentle,steep,and gentle.The longer the prefabricated crack length,the greater the damage to the rock sample,leading to a weaker ability of the rock sample to resist failure.

关 键 词：冻融损伤 三轴压缩 预制裂隙 PFC^(3D) 破坏演化 

分 类 号：TD313[矿业工程—矿井建设] TU452[建筑科学—岩土工程]