开挖卸荷松弛、库水周期性升降以及气候环境因素影响，致使边坡岩体遭受的卸荷损伤作用、干湿循环作用以及季节性冻融作用，是制约水库库区高陡开挖边坡安全建设与长期稳定运营的关键问题。以库岸人工开挖边坡消落带部位的开挖卸荷岩体为研究对象，结合先期地质勘察资料、场区气候环境资料及水位调度需求，综合采用室内试验、理论分析及数值模拟相结合的研究方法。探究干湿-冻融循环条件下库岸边坡消落带开挖卸荷岩体力学特性演化规律；以损伤力学为基础建立了干湿-冻融循环损伤本构模型；以数值模拟手段对岩体尺寸效应进行研究，探究了将室内试验获取力学参数转化为工程岩体可用力学参数的方法；结合工程实例建立三维模型进行数值计算，阐释了库岸人工开挖边坡消落带部位干湿-冻融循环孕灾致灾破坏模式。主要研究成果如下：
（1） 首先研究基于卸荷岩体力学理论，通过三轴基础试验确定了60%卸荷量作为关键特征点，并分析了卸荷损伤试样力学特性。接着，根据场区水位调度需求与气候环境因素设计了干湿-冻融循环试验。结果显示，随着循环次数增加，卸荷损伤试样质量减少，孔隙率增大，纵波波速逐渐降低，峰值强度和各项力学强度参数逐渐减小。变化趋势基本呈现循环初期较为显著，后期逐渐趋于稳定，附加有冻融作用的试验组劣化进程大于仅干湿循环的试验组。
（2） 其次，研究基于损伤力学，建立了干湿-冻融循环损伤本构模型，通过数学拟合方法得到了能够反映卸荷损伤试样在干湿-冻融循环条件下力学特性的表达式。结合Mohr-Coulomb准则建立了干湿-冻融循环条件下卸荷试样损伤演化模型，并以压密阶段硬化系数对损伤演化模型进行修正，修正后的损伤演化模型与室内试验应力-应变曲线吻合度较高。
（3） 研究通过三维有限差分数值软件对不同条件下卸荷损伤试样的应力-应变过程进行了模拟。以监测模型顶面应力增量和应变增量，标记产生定量塑性应变的单元，与室内实验进行对比，发现数值模拟结果与室内试验结果具有较好的一致性，验证了宏观力学参数变化规律和数值模拟方法的合理性。同时，采用随机裂隙网络数值模拟法研究了岩体力学参数的尺寸效应。研究发现，随试样尺寸不断增加，试样裂隙节理数目增加，力学参数也不断减弱，最终逐渐趋于稳定，为工程层面岩体力学参数的确定提供了一种有效方法。
（4） 最后，以某实际水电工程典型峡谷型水库库岸人工开挖边坡为例，进行了应力应变分析和损伤分区，以尺寸效应研究研究的岩体力学参数进行了数值计算分析。计算结果表明，在干湿-冻融循环条件下，消落带浅层岩体的变形随循环次数增加而逐渐增大，更容易发生破坏，从而降低了边坡的稳定性。

The dry-wet cycle action caused by excavation unloading relaxation and cyclical upturn and downturn of reservoir water and seasonal freeze-thaw action caused by climate and environment are the key problems that restrict the safe construction and long-term stable operation of highly-steep excavation slopes in reservoir area. Taking the excavation unloading rock mass in the hydro-fluctuation belt of the artificial excavation slope of the reservoir bank as the research object, combined with the previous geological survey data, the climate and environment data of the site and the demand of water level dispatching, the research methods of indoor test, theoretical analysis and numerical simulation are comprehensively adopted. This paper explored the evolution law of mechanical characteristics of excavated unloaded rock mass in the hydro-fluctuation belt of reservoir bank slope under the condition of dry-wet-freeze-thaw cycle; Based on damage mechanics, the damage constitutive model of dry-wet-freeze-thaw cycle was established The size effect of rock mass was studied by means of numerical simulation, and the method of transforming the mechanical parameters obtained from indoor tests into available mechanical parameters of engineering rock mass was explored. Combined with an engineering example, a three-dimensional model was established to carry out numerical calculation, and the failure mode of dry-wet-freeze-thaw cycle in the hydro-fluctuation belt of the artificial excavation slope on the reservoir bank was explained. The main research results are as follows:
（1） First of all, based on the theory of unloading rock mass mechanics, 60% unloading capacity was determined as the key characteristic point through triaxial foundation test and triaxial unloading test under constant axial pressure and confining pressure, and the unloading damage specimen was analyzed in detail. Secondly, according to the demand of water level dispatching and climate and environmental factors, the dry-wet-freeze-thaw cycle tests with different cycle times were designed and implemented. The experimental results showed that with the increase of cycle times, the mass of unloading damaged samples decreased, the porosity increased, the P-wave velocity decreased gradually, and the peak strength decreased gradually; the elastic modulus, cohesion and friction angle also decreased continuously. The change trend was obvious at the initial stage of the cycle, and gradually tended to be stable at the later stage. The deterioration process of the experimental group with freeze-thaw effect was also greater than that of the experimental group with dry-wet cycle only.
（2） Based on damage mechanics, the damage constitutive model of dry-wet-freeze-thaw cycle was established. Based on the results of laboratory tests, an expression which can reflect the mechanical properties of unloaded damaged specimens under dry-wet-freeze-thaw cycles was obtained by mathematical fitting method. The Mohr-Coulomb criterion was used to determine the Weibull probability distribution of the micro-element strength, and the damage evolution model of unloaded specimen under dry-wet-freeze-thaw cycle was established. By combining the two methods, the corresponding parameters of the damage evolution model could be calculated, and the damage evolution model could be modified by the hardening coefficient in the compaction stage. The corresponding deformation strength parameters, damage evolution model distribution parameters and compaction stage parameters could be obtained by fitting the corresponding confining pressure and cyclic action times, and the damage evolution model was consistent with the stress-strain curve of indoor test.
（3） Three-dimensional finite difference numerical software was used to simulate the stress-strain process of unloading damage samples under different dry-wet-freeze-thaw cycles under uniaxial and triaxial reloading. The stress-strain curves during reloading were obtained by monitoring the stress and strain increments on the top surface of the model, and the elements producing quantitative plastic strain were marked to analyze the failure modes. Generally speaking, the numerical simulation results were consistent with the laboratory test results, which verified the reliability of the obtained macroscopic mechanical parameters and the rationality of the numerical simulation method. The size effect of mechanical parameters of rock mass was studied by using random fracture network numerical simulation method. With the increasing of specimen size, the number of cracks and joints in the specimen increased gradually, and the mechanical parameters weakened and tended to be stable gradually, which provided an effective method for determining the mechanical parameters of rock mass in engineering layer.
（4） Finally, taking the artificial excavation slope of a typical gorge-type reservoir bank of a practical hydropower project as an example, the stress and deformation of slope excavation and support process were analyzed by numerical simulation method. Based on the calculation results, the operation characteristics of hydropower station and the climate environment of the site, the damage zoning of excavation slope was carried out. Based on the mechanical parameters of rock mass obtained from the study of size effect, the numerical calculation and analysis were carried out under the superposition of unloading excavation damage and dry-wet-freeze-thaw cyclic erosion in the hydro-fluctuation belt of reservoir bank slope considering water storage. The results showed that the deformation of shallow rock mass in hydro-fluctuation belt increased gradually with the increase of cycle times under the condition of dry-wet-freeze-thaw cycle, which made it easier to destroy, thus reducing the stability of slope.

[1]孙振刚,张岚,段中德. 我国水库工程数量及分布[J]. 中国水利, 2013, (07): 10-11.

[2]肖诗荣,胡志宇,卢树盛,等. 三峡库区水库复活型滑坡分类[J]. 长江科学院院报, 2013, 30(11): 39-44.

[3]Xia M, Ren G M, Zhu S S, et al. Relationship between landslide stability and reservoir water level variation[J]. Bulletin of Engineering Geology and the Environment, 2015, 74: 909-917.

[4]李建林．卸荷岩体力学[M]．北京：中国水利水电出版社，2003.

[5]李建林，王乐华．卸荷岩体力学原理与应用[M]．北京：科学出版社，2016.

[6]哈秋舲,李建林,张永兴,等. 节理岩体卸荷非线性岩体力学[M]. 北京:中国建筑工业出版社, 1998.

[7]刘国霖. 节理岩体的卸荷岩体力学理论要点[J]. 三峡大学学报(自然科学版), 2002, (03): 193-197.

[8]周济芳,李建林,陈兴周. 卸荷岩体力学特性研究的试验条件[J]. 三峡大学学报(自然科学版), 2004, (06): 514-516, 526.

[9]郑达,黄润秋.高边坡岩体卸荷带划分的量化研究[J].水文地质工程地质, 2006, (05): 9-12.

[10]王兰生,李文纲,孙云志. 岩体卸荷与水电工程[J]. 工程地质学报, 2008, (02): 145-154.

[11]黄润秋. 岩石高边坡发育的动力过程及其稳定性控制[J]. 岩石力学与工程学报, 2008, (08): 1525-1544.

[12]Wu F, Liu J, Liu T, et al. A method for assessment of excavation damaged zone (EDZ) of a rock mass and its application to a dam foundation case[J]. Engineering Geology, 2009, 104(3-4): 254-262.

[13]陈强,聂德新,潘思祎,等. 渗透系数作为岩体卸荷分带量化指标的研究[J]. 水文地质工程地质, 2011, 38(04): 48-53.

[14]孙云志. 边坡卸荷带岩体渗透特性分析——以三峡永久船闸高边坡为例[J]. 人民长江, 2011, 42(03): 20-22.

[15]Meng L, Li T, Xu J, et al. Deformation and failure mechanism of phyllite under the effects of THM coupling and unloading[J]. Journal of Mountain Science, 2012, 9(6).

[16]黄达,谭清,黄润秋. 高应力下脆性岩石卸荷力学特性及数值模拟[J]. 重庆大学学报, 2012, 35(06): 72-79.

[17]胡政,刘佑荣,武尚,等. 高地应力区砂岩在卸荷条件下的变形参数劣化试验研究[J]. 岩土力学, 2014, 35(S1): 78-84.

[18]Qiu S L, Feng X T, Xiao J Q, et al. An experimental study on the pre-peak unloading damage evolution of marble[J]. Rock Mechanics and Rock Engineering, 2014, 47: 401-419.

[19]Zhuang D Y, Tang C A, Liang Z Z, et al. Effects of excavation unloading on the energy-release patterns and stability of underground water-sealed oil storage caverns[J]. Tunnelling and Underground Space Technology, 2017, 61: 122-133.

[20]Xie S, Lin H, Wang Y, et al. A statistical damage constitutive model considering whole joint shear deformation[J]. International Journal of Damage Mechanics, 2020, 29(6): 988-1008.

[21]Ren H, Zhu Y, Wang P, et al. Experimental study on mechanical characteristics of unloaded damaged white sandstone before peak[J]. Arabian Journal of Geosciences, 2020, 13: 1-10.

[22]王士天,刘汉超,张倬元,等. 大型水域水岩相互作用及其环境效应研究[J]. 地质灾害与环境保护, 1997, (01): 70-90.

[23]C.W.Badger,A.D.Cummings,R.L.Whitmore. The disintegration of shale[J] Journal ofthe Institute of Fuel,1956,29,417-423.

[24]Terzaghi K, Peck R B, Mesri G. Soil mechanics in engineering practice[M]. John wiley & sons, 1996.

[25]M.F.Kennard,J.L.Knill. Reservoirs and limestones, with particular reference to the CowGreen Scheme[J]. Journal of the Institute of Water Engineers. 1968,（23）:87-113.

[26]Jeng F S, Lin M L, Huang T H. Wetting deterioration of soft sandstone-microscopic insights[C]//ISRM International Symposium. OnePetro, 2000.

[27]邓华锋,李建林,刘杰,等. 浸泡-风干循环作用对砂岩变形及破坏特征影响研究[J]. 岩土工程学报, 2012, 34(09): 1620-1626.

[28]邓华锋,罗骞,李建林,等. 浸泡-风干循环作用下砂岩动力特性劣化规律研究[J]. 岩土力学, 2013, 34(09): 2468-2474.

[29]邓华锋,原先凡,李建林,等. 饱水度对砂岩纵波波速及强度影响的试验研究[J]. 岩石力学与工程学报, 2013, 32(08): 1625-1631.

[30]邓华锋,李建林,朱敏,等. 饱水-风干循环作用下砂岩强度劣化规律试验研究[J]. 岩土力学, 2012, 33(11): 3306-3312.

[31]王新刚. 饱水—失水循环劣化作用下库岸高边坡岩石流变机理及工程应用研究[D]. 中国地质大学, 2014

[32]刘新荣,王子娟,傅晏,等. 考虑干湿循环作用泥质砂岩的强度与破坏准则研究[J]. 岩土力学, 2017, 38(12): 3395-3401.

[33]王伟,龚传根,朱鹏辉,等. 大理岩干湿循环力学特性试验研究[J]. 水利学报, 2017, 48(10): 1175-1184.

[34]杨有贞,何贤元,康亚明,等. 干湿循环作用下贺兰山岩画载体砂岩风化特征[J]. 科学技术与工程, 2018, 18(07): 31-37.

[35]刘新荣,袁文,傅晏,等. 干湿循环作用下砂岩溶蚀的孔隙度演化规律[J]. 岩土工程学报, 2018, 40(03): 527-532.

[36]徐志华,张国栋,孙钱程,等. 干湿循环作用下红砂岩强度劣化特性试验[J]. 中国公路学报, 2018, 31(02): 226-233.

[37]刘新喜,李玉,范子坚,等. 干湿循环作用下单裂隙炭质页岩能量演化与破坏特征研究[J]. 岩土力学, 2022, 43(07): 1761-1771.

[38]刘新喜,李玉,王玮玮,等. 干湿循环作用下预制裂隙炭质页岩力学特性及强度准则研究[J]. 岩石力学与工程学报, 2022, 41(02): 228-239.

[39]刘成禹,何满潮,王树仁,等. 花岗岩低温冻融损伤特性的实验研究[J]. 湖南科技大学学报(自然科学版), 2005, (01): 37-40.

[40]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.

[41]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.

[42]陈有亮,王朋,张学伟,等. 花岗岩在化学溶蚀和冻融循环后的力学性能试验研究[J]. 岩土工程学报, 2014, 36(12): 2226-2235.

[43]吴安杰,邓建华,顾乡,等. 冻融循环作用下泥质白云岩力学特性及损伤演化规律研究[J]. 岩土力学, 2014, 35(11): 3065-3072.

[44]Özbek A. Investigation of the effects of wetting–drying and freezing–thawing cycles on some physical and mechanical properties of selected ignimbrites[J]. Bulletin of Engineering Geology and the Environment, 2014, 73(2): 595-609.

[45]刘波,马永君,盛海龙,等. 白垩系红砂岩冻结融化后的力学性质试验研究[J]. 岩土力学, 2019, 40(S1): 161-171.

[46]刘杰,张瀚,王瑞红,等. 冻融循环作用下砂岩层进式损伤劣化规律研究[J]. 岩土力学, 2021, 42(05): 1381-1394.

[47]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.

[48]Nicholson D T, Nicholson F H. Physical deterioration of sedimentary rocks subjected to experimental freeze–thaw weathering[J]. Earth Surface Processes and Landforms: The Journal of the British Geomorphological Research Group, 2000, 25(12): 1295-1307.

[49]贾蓬,毛松泽,孙占阳,等. 冻融损伤砂岩的能量演化及分段本构模型[J]. 中南大学学报(自然科学版), 2023, 54(03): 908-919.

[50]Wei L, Hudson J A. A hybrid discrete-continuum approach to model hydro-mechanical behaviour of jointed rocks[J]. Engineering geology, 1998, 49(3-4): 317-325.

[51]Yao Z H, Yuan M W, Shi G. Applications of discontinuous deformation analysis (DDA) to rock engineering[C]//Computational Mechanics: Proceedings of “International Symposium on Computational Mechanics” July 30–August 1, 2007, Beijing, China. Springer Berlin Heidelberg, 2009: 136-147.

[52]周济芳,李建林,邓华锋,等. 岩体卸荷力学特性的数值仿真研究[J]. 岩土力学, 2008, 29(S1): 524-528.

[53]王乐华,李建林,陈星,等. 卸荷岩体尺寸效应数值模拟研究[J]. 水电能源科学, 2011, 29(02): 82-84, 52.

[54]蔡健,刘杰. 某水电站边坡卸荷岩体宏观力学参数反演对比研究[J]. 水力发电, 2013, 39(11): 20-23.

[55]Kaya A. Geotechnical assessment of a slope stability problem in the Citlakkale residential area (Giresun, NE Turkey)[J]. Bulletin of engineering geology and the environment, 2017, 76: 875-889.

[56]Zhou X P, Zhang X Q. The 3D numerical simulation of damage localization of rocks using general particle dynamics[J]. Engineering Geology, 2017, 224: 29-42.

[57]Qian Z G, Li A J, Lyamin A V, et al. Parametric studies of disturbed rock slope stability based on finite element limit analysis methods[J]. Computers and Geotechnics, 2017, 81: 155-166.

[58]向力,王乐华,陈招军,等. 干湿循环作用下砂岩的劣化及破坏特性研究[J]. 水利水电技术, 2017, 48(05): 142-147.

[59]胡田飞,杜升涛,师亚龙. 基于偏应力增量的边坡开挖松动区的确定方法[J]. 防灾减灾工程学报, 2017, 37(06): 892-899.

[60]陈勇,崔宪东,赵强,等. 干湿循环对边坡动力稳定性的影响及模拟[J]. 武汉大学学报(工学版), 2021, 54(09): 795-800.

[61]Zhang H, Wang L, Li J, et al. Mechanical properties of sandstones under initial unloading damage[J]. Advances in Civil Engineering, 2021, 2021: 1-12.

[62]Zhang Y, Liu S, Kou M, et al. 3-D numerical study on progressive failure characteristics of marbles under unloading conditions[J]. Applied Sciences, 2020, 10(11): 3875.

[63]Kachanov L. Introduction to continuum damage mechanics[M]. Springer Science & Business Media, 1986.

[64]Lemaitre J. A continuous damage mechanics model for ductile fracture[J]. 1985.

[65]尤明庆,邹友峰. 关于岩石非均质性与强度尺寸效应的讨论[J]. 岩石力学与工程学报, 2000, (03): 391-395.