在我国寒冷地区，岩体结构面的稳定性深受冻融循环作用的影响。岩体结构面的内部水分反复冻结消融诱发其强度折减，极易引起岩体工程地质病害。因此，探明冻融循环作用下岩体结构面的力学特性和剪切破坏机制是我国寒区工程灾变防治的关键科学问题之一。论文以不同冻融循环次数、法向应力下岩体结构面为研究对象，开展三维扫描试验、直接剪切试验和数值模拟研究。利用三维扫描技术对冻融循环下岩体结构面的粗糙度劣化进行识别；开展直接剪切试验探明冻融循环下岩体结构面的力学特性；结合模拟试验揭示不同冻融循环下岩体结构面的剪切破坏机制。文章内容为寒区岩体结构面的灾害防治提供理论参考。主要得出结论如下：

（1）通过开展不同冻融次数下岩体结构面的三维扫描试验，发现岩体结构面的表面会随冻融循环次数的增加逐渐出现局部冻融劣化。随着冻融循环的增加，局部冻融劣化的位置逐渐从右向左偏移。由于局部冻融劣化的存在，导致岩体结构面整体粗糙度随着冻融循环呈现出两个阶段的下降趋势。在冻融循环0~20次时，岩体结构面整体粗糙度的下降较快。在冻融循环20~40时，岩体结构面整体粗糙度的下降速度减缓。

（2）通过开展不同冻融循环次数、法向应力下岩体结构面的直接剪切试验，发现岩体结构面的剪切-位移曲线呈“双峰”形态。随着冻融循环次数的增加，两个峰值对应的剪切强度变化趋势不同，第一峰值的剪切强度总体呈先增大后减小的趋势，而第二峰值的剪切强度总体呈现下降趋势。在剪切强度下降阶段，两个峰值剪切强度的下降幅度随冻融次数增加而减小。此外，随着冻融循环次数的增加，两个峰值对应的剪切位移均呈上升趋势。其中，在冻融循环0~10次时，两个峰值剪切位移的上升幅度最大，而在冻融循环20~40次时，两个峰值剪切位移的上升幅度逐渐减弱。

（3）通过开展不同冻融循环次数、法向应力下体结构面的数值模拟试验，发现岩体结构面的剪切破坏机制受微凸体的倾角和冻融循环次数的影响，而法向应力仅影响其破坏规模。在未经冻融循环时，岩体结构面的剪切破坏机制为：剪切过程优先沿着倾角最大的微凸体发生剪胀现象，直到最大倾角微凸体破坏后，岩体结构面会继续沿着次大倾角微凸体进行剪切。由于冻融循环作用，倾角较小的微凸体会提前参与剪切过程，从而改变岩体结构面的剪切破坏机制。随着冻融次数的增加，倾角较小的微凸体将会更早地参与剪切过程，并且其的破坏规模也会增大。

In the cold region of China, the stability of rock joints are deeply affected by freeze-thaw cycles. The repeated freezing and melting of water in rock joints induces its strength reduction, which can easily cause engineering geological diseases of rock mass. Therefore, it is one of the key scientific problems in the prevention and control of engineering disasters in cold regions of China to explore the mechanical properties and shear failure mechanism of rock joints under freeze-thaw cycles. In this paper, three-dimensional scanning test, direct shear test and numerical simulation were carried out on rock joints under different freeze-thaw cycles and normal stress. The roughness damage of rock joints under freeze-thaw cycle is identified by three-dimensional scanning technology. The direct shear test was carried out to explore the mechanical properties of rock joints under freeze-thaw cycles. Combined with numerical simulation, the shear failure mechanism of rock joints under different freeze-thaw cycles are revealed. The content of this paper provides a theoretical reference for the disaster prevention and control of rock joints in cold regions. The main conclusions are as follows :

(1) Through the three-dimensional scanning test of rock joints under different freeze-thaw cycles, it is found that the surface of rock joints will gradually appear local freeze-thaw damage with the increase of freeze-thaw cycles. With the increase of freeze-thaw cycles, the location of local freeze-thaw damage gradually shifted from right to left. Due to the existence of local freeze-thaw damage, the overall roughness of the rock joints shows a two-stage downward trend with the freeze-thaw cycle. When the freeze-thaw cycle is 0~20 times, the overall roughness of the rock joints decreases rapidly, and when the freeze-thaw cycle is 20~40, the decrease rate of the overall roughness of the rock joints slows down.

(2) Through the direct shear test of rock joints under different freeze-thaw cycles and normal stress, it is found that the shear-displacement curve of rock joints is in the form of “double peak”. As the number of freeze-thaw cycles increases, the shear strength corresponding to the two peaks changes differently. The shear strength of the first peak generally increases first and then decreases, while the shear strength of the second peak generally shows a downward trend. In the stage of shear strength decrease, the decrease of two peak shear strength decreases with the increase of freeze-thaw cycles. In addition, with the increase of the number of freeze-thaw cycles, the shear displacement corresponding to the two peaks shows an upward trend. Among them, when the freeze-thaw cycle is 0~10 times, the increase of the two peak shear displacements is the largest, and when the freeze-thaw cycle is 20~40 times, the increase of the two peak shear displacements gradually weakens.

(3) Through the numerical simulation test of body structural plane under different freeze-thaw cycles and normal stress, it is found that the shear failure mechanism of rock joints is influenced by the inclination angle of micro convex bodies and the number of freeze-thaw cycles, while normal stress only affects their failure scale. When not subjected to freeze-thaw cycles, the shear failure mechanism of the rock joints is that the shear process preferentially occurs along the micro convex body with the highest inclination angle, and until the micro convex body with the highest inclination angle is destroyed, the rock joints will continue to shear along the sub large inclination micro convex body. Due to the freeze-thaw cycle, micro convexities with smaller inclination angles participate in the shear process in advance, thereby changing the shear failure mechanism of the rock joints. As the number of freeze-thaw cycles increases, micro convex bodies with smaller inclination angles will participate in the shear process earlier, and their failure scale will also increase.

[1] 周幼吾, 郭东信, 邱国庆, 等. 中国冻土[M]. 北京: 科学出版社, 2000.

[2] 徐学祖, 王家澄, 张立新. 冻土物理学[M]. 北京: 科学出版社, 2001.

[3] 乔国文.天山山区边坡冻融成灾机理及岩体质量评价体系研究[D].成都理工大学,2019.

[4] 彭建兵,崔鹏,庄建琦.川藏铁路对工程地质提出的挑战[J].岩石力学与工程学报,2020,39(12):2377-2389.

[5] 郭长宝,王保弟,刘建康,等.川藏铁路交通廊道地质调查工程主要进展与成果[J].中国地质调查,2020,7(06):1-12.

[6] 谷德振. 岩体工程地质力学基础[M]. 北京: 科学出版社, 1979.

[7] 王思敬. 坝基岩体工程地质力学分析[M]. 北京: 科学出版社, 1990.

[8] 黄润秋. 岩石高边坡稳定性工程地质分析[M]. 北京: 科学出版社, 2012.

[9] 杨更社,申艳军,贾海梁,等.冻融环境下岩体损伤力学特性多尺度研究及进展[J].岩石力学与工程学报,2018,37(03):545-563.

[10]Davies M C R, Hamza O, Harris C. The effect of rise in mean annual temperature on the stability of rock slopes containing ice‐filled discontinuities[J]. Permafrost and periglacial processes, 2001, 12(1): 137-144.

[11]Krautblatter M, Funk D, Günzel F K. Why permafrost rocks become unstable: a rock–ice‐mechanical model in time and space[J]. Earth Surface Processes and Landforms, 2013, 38(8): 876-887.

[12]蒲成志.岩体断裂与蠕变损伤破坏机理研究[D].中南大学,2014.

[13]刘泉声,康永水,黄兴,等.裂隙岩体冻融损伤关键问题及研究状况[J].岩土力学,2012,33(04):971-978.

[14]Mu J, Pei X, Huang R, et al. Degradation characteristics of shear strength of joints in three rock types due to cyclic freezing and thawing[J]. Cold Regions Science and Technology, 2017, 138: 91-97.

[15]Zhang H, Meng X, Yang G. A study on mechanical properties and damage model of rock subjected to freeze-thaw cycles and confining pressure[J]. Cold Regions Science and Technology, 2020, 174: 103056.

[16]Tang L, Du Y, Liu L, et al. Effect mechanism of unfrozen water on the frozen soil-structure interface during the freezing-thawing process[J]. Geomechanics and Engineering, 2020, 22(3): 245-254.

[17]Winkler E M. Frost damage to stone and concrete: geological considerations[J]. Engineering Geology, 1968, 2(5): 315-323.

[18]Matsuoka N. Mechanisms of rock breakdown by frost action: An experimental approach[J]. Cold Regions Science and Technology, 1990, 17(3): 253-270.

[19]徐光苗,刘泉声.岩石冻融破坏机理分析及冻融力学试验研究[J].岩石力学与工程学报,2005(17):3076-3082.

[20]张慧梅,杨更社.冻融与荷载耦合作用下岩石损伤模型的研究[J].岩石力学与工程学报,2010,29(03):471-476.

[21]罗学东,黄成林,肜增湘,等.冻融循环作用下蒙库铁矿边坡岩体物理力学特性研究[J].岩土力学,2011,32(S1):155-159.

[22]Bayram F. Predicting mechanical strength loss of natural stones after freeze–thaw in cold regions[J]. Cold Regions Science and Technology, 2012, 83: 98-102.

[23]Altindag R, Alyildiz I S, Onargan T. Mechanical property degradation of ignimbrite subjected to recurrent freeze–thaw cycles[J]. International journal of rock mechanics and mining sciences, 2004, 41(6): 1023-1028.

[24]Aoki K, Hibiya K, Yoshida T. Storage of refrigerated liquefied gases in rock caverns: characteristics of rock under very low temperatures[J]. Tunnelling and underground space technology, 1990, 5(4): 319-325.

[25]Wang F, Cao P, Wang Y, et al. Combined effects of cyclic load and temperature fluctuation on the mechanical behavior of porous sandstones[J]. Engineering Geology, 2020, 266: 105466.

[26]Takarli M, Prince W, Siddique R. Damage in granite under heating/cooling cycles and water freeze–thaw condition[J]. International Journal of Rock Mechanics and Mining Sciences, 2008, 45(7): 1164-1175.

[27]Khanlari G, Abdilor Y. Influence of wet–dry, freeze–thaw, and heat–cool cycles on the physical and mechanical properties of Upper Red sandstones in central Iran[J]. Bulletin of Engineering Geology and the Environment, 2015, 74: 1287-1300.

[28]Momeni A, Khanlari G R, Heidari M, et al. Assessment of physical weathering effects on granitic ancient monuments, Hamedan, Iran[J]. Environmental earth sciences, 2015, 74: 5181-5190.

[29]Ince I, Fener M. A prediction model for uniaxial compressive strength of deteriorated pyroclastic rocks due to freeze–thaw cycle[J]. Journal of African Earth Sciences, 2016, 120: 134-140.

[30]Weng L, Wu Z, Taheri A, et al. Deterioration of dynamic mechanical properties of granite due to freeze-thaw weathering: Considering the effects of moisture conditions[J]. Cold Regions Science and Technology, 2020, 176: 103092.

[31]Liu B, Sun Y, Yuan Y, et al. Strength characteristics of frozen sandstone with different water content and its strengthening mechanism[J]. J. China Univ. Min. Technol, 2020, 49(06): 1085-1093.

[32]Wang Q, Fu Q. Research on mechanical properties of port rock under different water conditions[J]. Journal of Coastal Research, 2020, 105(SI): 223-227.

[33]Prick A. Critical degree of saturation as a threshold moisture level in frost weathering of limestones[J]. Permafrost and Periglacial Processes, 1997, 8(1): 91-99.

[34]周科平,李杰林,许玉娟,等.冻融循环条件下岩石核磁共振特性的试验研究[J].岩石力学与工程学报,2012,31(04):731-737.

[35]李杰林,周科平,柯波.冻融后花岗岩孔隙发育特征与单轴抗压强度的关联分析[J].煤炭学报,2015,40(08):1783-1789.

[36]Li J, Kaunda R B, Zhou K. Experimental investigations on the effects of ambient freeze-thaw cycling on dynamic properties and rock pore structure deterioration of sandstone[J]. Cold Regions Science and Technology, 2018, 154: 133-141.

[37]Jia H, Ding S, Zi F, et al. Evolution in sandstone pore structures with freeze-thaw cycling and interpretation of damage mechanisms in saturated porous rocks[J]. Catena, 2020, 195: 104915.

[38]Liu T, Zhang C, Li J, et al. Detecting freeze–thaw damage degradation of sandstone with initial damage using NMR technology[J]. Bulletin of Engineering Geology and the Environment, 2021, 80: 4529-4545.

[39]Park J, Hyun C U, Park H D. Changes in microstructure and physical properties of rocks caused by artificial freeze–thaw action[J]. Bulletin of Engineering Geology and the Environment, 2015, 74: 555-565.

[40]贾海梁,项伟,谭龙,等.砂岩冻融损伤机制的理论分析和试验验证[J].岩石力学与工程学报,2016,35(05):879-895.

[41]Zhou X P, Li C Q, Zhou L S. The effect of microstructural evolution on the permeability of sandstone under freeze-thaw cycles[J]. Cold Regions Science and Technology, 2020, 177: 103119.

[42]田镇,张君岳,王贵宾,等.冻融红砂岩微观结构损伤试验研究[J].矿业研究与开发,2021,41(10):61-66.

[43]张娜,赵伟征,罗水亮,等.基于单轴压缩与扫描电镜试验的冻融红砂岩损伤特性研究[J].建筑科学与工程学报,2023,40(04):153-162.

[44]杨更社,张全胜,蒲毅彬.冻融条件下岩石损伤扩展特性研究(英文)[J].岩土工程学报,2004(06):838-842.

[45]De Argandona V G R, Rey A R, Celorio C, et al. Characterization by computed X-ray tomography of the evolution of the pore structure of a dolomite rock during freeze-thaw cyclic tests[J]. Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy, 1999, 24(7): 633-637.

[46]杨鸿锐,刘平,孙博,等.冻融循环对麦积山石窟砂砾岩微观结构损伤机制研究[J].岩石力学与工程学报,2021,40(03):545-555.

[47]刘慧,杨更社,任建喜.基于数字图像处理的冻融页岩温度场的数值分析方法[J].岩石力学与工程学报,2007(08):1678-1683.

[48]谭皓,宋勇军,郭玺玺,等.冻融裂隙砂岩细观损伤与应变局部化研究[J].岩石力学与工程学报,2022,41(12):2485-2496.

[49]Patton F D. Multiple modes of shear failure in rock[C]//ISRM Congress. ISRM, 1966: ISRM-1CONGRESS-1966-087.

[50]Ladanyi B, Archambault G. Simulation of shear behavior of a jointed rock mass[C]//ARMA US Rock Mechanics/Geomechanics Symposium. ARMA, 1969: ARMA-69-0105.

[51]Barton N. Review of a new shear-strength criterion for rock joints[J]. Engineering geology, 1973, 7(4): 287-332.

[52]Barton N. The shear strength of rock and rock joints[C]//International Journal of rock mechanics and mining sciences & Geomechanics abstracts. Pergamon, 1976, 13(9): 255-279.

[53]Barton N, Choubey V. The shear strength of rock joints in theory and practice[J]. Rock mechanics, 1977, 10: 1-54.

[54]Barton N, Bandis S. Effects of block size on the shear behavior of jointed rock[C]//ARMA US Rock Mechanics/Geomechanics Symposium. ARMA, 1982: ARMA-82-739.

[55]赵坚.岩石节理剪切强度的JRC-JMC新模型[J].岩石力学与工程学报,1998,(04):1-9.

[56]Asadollahi P, Tonon F. Constitutive model for rock fractures: Revisiting Barton's empirical model[J]. Engineering Geology, 2010, 113(1-4): 11-32.

[57]McWilliams P C, Kekering J C, Miller S M. Estimation of shear strength using fractals as a measure of rock fracture roughness[M]. US Department of the Interior, Bureau of Mines, 1993.

[58]Kulatilake P, Shou G, Huang T H, et al. New peak shear strength criteria for anisotropic rock joints[C]//International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. Pergamon, 1995, 32(7): 673-697.

[59]Um J. Accurate quantification of rock joint roughness and development of a new peak shear strength criterion for joints[M]. The University of Arizona, 1997.

[60]Zhang X, Jiang Q, Chen N, et al. Laboratory investigation on shear behavior of rock joints and a new peak shear strength criterion[J]. Rock Mechanics and Rock Engineering, 2016, 49: 3495-3512.

[61]Homand F, Belem T, Souley M. Friction and degradation of rock joint surfaces under shear loads[J]. International Journal for Numerical and Analytical Methods in Geomechanics, 2001, 25(10): 973-999.

[62]Grasselli G, Egger P. Constitutive law for the shear strength of rock joints based on three-dimensional surface parameters[J]. International Journal of Rock Mechanics and Mining Sciences, 2003, 40(1): 25-40.

[63]Grasselli G. Manuel Rocha medal recipient shear strength of rock joints based on quantified surface description[J]. Rock Mechanics and Rock Engineering, 2006, 39(4): 295-314.

[64]Xia C C, Tang Z C, Xiao W M, et al. New peak shear strength criterion of rock joints based on quantified surface description[J]. Rock Mechanics and Rock Engineering, 2014, 47(2): 387-400.

[65]Tatone B S A, Grasselli G. A new 2D discontinuity roughness parameter and its correlation with JRC[J]. International Journal of Rock Mechanics and Mining Sciences, 2010, 47(8): 1391-1400.

[66]夏才初.岩石结构面表面形貌的波纹度特征及其力学效应[J].同济大学学报(自然科学版),1993,(03):371-377.

[67]Gao Y, Wong L N Y. A modified correlation between roughness parameter Z2 and the JRC[J]. Rock mechanics and rock engineering, 2015, 48: 387-396.

[68]Liu X G, Zhu W C, Yu Q L, et al. Estimation of the joint roughness coefficient of rock joints by consideration of two-order asperity and its application in double-joint shear tests[J]. Engineering Geology, 2017, 220: 243-255.

[69]Muralha J, Grasselli G, Tatone B, et al. ISRM suggested method for laboratory determination of the shear strength of rock joints: revised version[J]. Rock Mechanics and Rock Engineering, 2014, 47: 291-302.

[70]Maerz N H, Franklin J A, Bennett C P. Joint roughness measurement using shadow profilometry[C]//International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. Pergamon, 1990, 27(5): 329-343.

[71]Kodikara J K, Johnston I W. Shear behaviour of irregular triangular rock-concrete joints[C]//International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. Pergamon, 1994, 31(4): 313-322.

[72]Wakabayashi N, Fukushige I. Experimental study on the relation between fractal dimension and shear strength[C]//Fractured and jointed rock masses. 1995: 119-124.

[73]Beer A J, Stead D, Coggan J S. Technical note estimation of the joint roughness coefficient (JRC) by visual comparison[J]. 2002.

[74]Jang H S, Jang B A. New method for shear strength determination of unfilled, unweathered rock joint[J]. Rock Mechanics and Rock Engineering, 2015, 48: 1515-1534.

[75]Hsiung S M, Ghosh A, Ahola M P, et al. Assessment of conventional methodologies for joint roughness coefficient determination[C]//ARMA US Rock Mechanics/Geomechanics Symposium. ARMA, 1993: ARMA-93-0661.

[76]Barton N. Modelling Rock Joint Behavior Form in Situ Block Tests: Implications for Nuclear Waste Repository Design: Technical Report[M]. Office of Nuclear Waste Isolation, Battelle Project Management Division, 1982.

[77]Barton N. Shear strength criteria for rock, rock joints, rockfill and rock masses: Problems and some solutions[J]. Journal of Rock Mechanics and Geotechnical Engineering, 2013, 5(4): 249-261.

[78]杜时贵,陈禹,樊良本.JRC修正直边法的数学表达[J].工程地质学报,1996,(02):36-43.

[79]胡晓飞,杜时贵.结构面粗糙度系数Barton直边法的简明公式[J].工程地质学报,2008,(02):196-200.

[80]Myers N O. Characterization of surface roughness[J]. Wear, 1962, 5(3): 182-189.

[81]Tse R, Cruden D M. Estimating joint roughness coefficients[C]//International journal of rock mechanics and mining sciences & geomechanics abstracts. Pergamon, 1979, 16(5): 303-307.

[82]Yu X, Vayssade B. Joint profiles and their roughness parameters[C]//International journal of rock mechanics and mining sciences & geomechanics abstracts. Pergamon, 1991, 28(4): 333-336.

[83]Yang Z Y, Lo S C, Di C C. Reassessing the joint roughness coefficient (JRC) estimation using Z2[J]. Rock mechanics and rock engineering, 2001, 34: 243-251.

[84]Barton N, de Quadros E F. Joint aperture and roughness in the prediction of flow and groutability of rock masses[J]. International Journal of Rock Mechanics and Mining Sciences, 1997, 34(3-4): 252. e1-252. e14.

[85]Jang H S, Kang S S, Jang B A. Determination of joint roughness coefficients using roughness parameters[J]. Rock mechanics and rock engineering, 2014, 47: 2061-2073.

[86]Abolfazli M, Fahimifar A. An investigation on the correlation between the joint roughness coefficient (JRC) and joint roughness parameters[J]. Construction and Building Materials, 2020, 259: 120415.

[87]Hong E S, Lee J S, Lee I M. Underestimation of roughness in rough rock joints[J]. International Journal for Numerical and Analytical Methods in Geomechanics, 2008, 32(11): 1385-1403.

[88]王岐.用伸长率R确定岩石节理粗糙度系数的研究[C]//中国岩石力学与工程学会.地下工程经验交流会论文选集.白银矿冶研究所;,1982:6.

[89]Zhang G, Karakus M, Tang H, et al. A new method estimating the 2D joint roughness coefficient for discontinuity surfaces in rock masses[J]. International Journal of Rock Mechanics and Mining Sciences, 2014, 72: 191-198.

[90]Magsipoc E, Zhao Q, Grasselli G. 2D and 3D Roughness Characterization[J]. Rock Mechanics and Rock Engineering, 2020, 53(3): 1495-1519.

[91]Ban L, Du W, Qi C, et al. Modified 2D roughness parameters for rock joints at two different scales and their correlation with JRC[J]. International Journal of Rock Mechanics and Mining Sciences, 2021, 137: 104549.

[92]Li Y, Zhang Y. Quantitative estimation of joint roughness coefficient using statistical parameters[J]. International Journal of Rock Mechanics and Mining Sciences, 2015, 77: 27-35.

[93]周辉,程广坦,朱勇,等.大理岩规则齿形结构面剪切特性试验研究[J].岩土力学,2019,40(03):852-860.

[94]孙盛玥,李迎春,唐春安,等.天然岩石节理双阶粗糙度分形特征研究[J].岩石力学与工程学报,2019,38(12):2502-2511.