FDEM numerical simulation study on deterioration characteristics of weak-hard interbedded strata landslide-anti-slide pile system under wetting-drying cycles
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摘要:
三峡库区秭归盆地广泛分布以软硬相间地层为主的易滑地层,在长期的库水浸泡冲刷、降雨等作用下,地层岩土体发生劣化损伤,成为降低滑坡稳定和影响工程安全的重要内因。以软硬相间地层岩土体为研究对象,采用有限-离散元法(finite discrete element method,FDEM)对不同干湿循环作用下软硬相间地层中硬岩和软岩的力学参数进行标定,然后通过改进的泰森多边形程序进行网格重划分,实现零厚度黏聚力单元的嵌入功能,提出并建立软硬相间地层滑坡-抗滑桩体系FDEM数值计算模型,最后对不同干湿循环作用下滑坡裂纹的形成过程和抗滑桩的嵌固机理进行研究。研究结果表明:①滑坡模拟裂纹数量随着干湿循环次数的增加而增多,裂纹宽度也逐渐增大,并与马家沟滑坡现场裂缝进行对比,模拟结果与现场基本一致;②滑坡-抗滑桩体系的模拟裂纹呈现2种演化模式,一是裂纹从桩顶侧岩土体沿着桩身向下扩展,二是裂纹从抗滑桩周围逐渐向滑体内部延伸,与横向裂纹和竖向裂纹连通,最终形成大型的贯通裂纹;③当干湿循环次数增加时,抗滑桩桩身水平位移、弯矩和剪力也随之增加;④抗滑桩嵌固段的软硬相间地层基岩内的裂纹具有局部化发育特征,而且随干湿循环次数的增加,区域内的应力逐渐减小,位移和应变则逐渐增大,相应的裂纹也愈发密集。本研究成果可为不同干湿循环作用下软硬相间地层滑坡防治提供支撑。
Abstract:Objective In Zigui Basin of the Three Gorges Reservoir region, prone-sliding strata mainly composed of weak-hard interbedded strata are widely distributed. Under the action of long-term reservoir water immersion, erosion and rainfall, the formation rock and soil bodies deteriorate and become an important internal cause of reducing landslide stability and affecting project safety.
Methods Taking rock and soil mass of weak-hard interbedded strata as the research object, finite discrete element method (FDEM) is used to calibrate the mechanical properties of hard and soft rocks in the weak-hard interbedded strata under different wetting-drying cycles. Then the mesh is redivided by the improved Tyson polygon program, and the embedding function of zero thickness cohesive force unit is realized. The FDEM numerical model of landslide-anti-slide pile system in weak-hard interbedded strata formation is proposed and established. Finally, the formation process of landslide cracks and the embedding mechanism of anti-slide piles under different wetting-drying cycles are studied.
Results The results show that: ① The number of simulated landslide cracks increases with the increase of the number of wetting-drying cycles, and the cracks width also increases gradually. The results of simulation are basically consistent with those of the site of Majiagou landslide. ② The simulated cracks of the landslide-anti-slide pile system show two evolutionary patterns: one is that the cracks spread downward from the rock mass on the top side of the pile along the pile body; the other is that the cracks gradually extend from around the anti-slide pile to the inside of the slide body, connecting with the transverse cracks and vertical cracks, and finally forming large through cracks. ③ When the number of wetting-drying cycles increases, the horizontal displacement, bending moment and shear force of anti-slide pile also increase. ④ The cracks in the weak-hard interbedded strata bedrock of the anti-slide pile have the characteristics of localized development, and with the increase of the number of wetting-drying cycles, the stress in the region gradually decreases, the displacement and strain gradually increase, and the corresponding cracks become more and more intensive.
Conclusion The results of this study can provide support for the prevention and control of landslide in weak-hard interbedded strata under different wetting-drying cycles.
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图 1 黏聚力单元的T−S准则[27]
GⅠ,GⅡ分别为Ⅰ型和Ⅱ型断裂能;Kn,Ks分别为黏聚力单元初始法向刚度和初始剪切刚度;$ \sigma_{\mathrm{n}}^0 $,$ \sigma_{\mathrm{s}}^0 $分别为黏聚力单元法向和剪切方向的峰值应力;σ为应力;$ \delta_{\mathrm{n}}^0 $,$ \delta_{\mathrm{s}}^0 $分别为$ \sigma_{\mathrm{n}}^0 $,$ \sigma_{\mathrm{s}}^0 $对应的拉伸位移和剪切位移;$ \delta\mathrm{_{nc}} $,$ \delta\mathrm{_{sc}} $,$ \delta\mathrm{_{np}} $和$ \delta\mathrm{_{sp}} $分别为黏聚力单元的拉伸损伤起始位移、剪切损伤起始位移、拉伸失效位移和剪切失效位移
Figure 1. Traction-separation law of cohesive element
表 1 不同干湿循环作用下硬岩的FDEM单轴压缩模拟输入参数
Table 1. FDEM uniaxial compression simulation input parameters of hard rock under different wetting-drying cycles
单元
类型参数 干湿循环次数n 0(天然) 1 2 3 4 5 实体
单元密度ρ/(kg·m−3) 2470 2320 2200 2190 2190 2190 弹性模量E/GPa 30 28 27 26 25 24 泊松比ν 0.28 0.28 0.28 0.28 0.28 0.28 黏聚力
单元抗拉强度ft/MPa 5 4 3.5 3 3 2.6 黏聚力c/MPa 10 9 8.5 7.6 7 6.8 内摩擦角φ/(°) 26 24.8 23.5 22.9 22.3 22 Ⅰ型断裂能GI/(J·m−2) 88 60 48 36 36 30 Ⅱ型断裂能GⅡ/(J·m−2) 176 120 96 72 72 60 初始法向刚度En/GPa 60 56 54 52 50 48 初始切向刚度Es/GPa 30 28 27 26 25 24 法向接触刚度Pn/GPa 90 90 90 90 90 90 切向接触刚度Ps/GPa 60 60 60 60 60 60 表 2 不同干湿循环作用下软岩的FDEM单轴压缩模拟输入参数
Table 2. FDEM uniaxial compression simulation input parameters of soft rock under different wetting-drying cycles
单元
类型参数 干湿循环次数n 0(天然) 1 2 3 4 5 实体
单元密度ρ/(kg·m−3) 2260 2100 2050 2030 2020 2020 弹性模量E/GPa 10 8.2 8 7.9 7.5 7 泊松比ν 0.3 0.3 0.3 0.3 0.3 0.3 黏聚力
单元抗拉强度ft/MPa 2 1.7 1.5 1.4 1.35 1.3 黏聚力c/MPa 5 4.2 3.9 3.6 3.2 3 内摩擦角φ/(°) 18 16.5 15.5 15 14.8 14.5 Ⅰ型断裂能GⅠ/(J·m−2) 40 37 30 26 25 25 Ⅱ型断裂能GⅡ/(J·m−2) 80 74 60 52 50 50 初始法向刚度En/GPa 20 16.4 16 15.8 15 14 初始切向刚度Es/GPa 10 8.2 8 7.9 7.5 7 法向接触刚度Pn/GPa 60 60 60 60 60 60 切向接触刚度Ps/GPa 30 30 30 30 30 30 表 3 计算模型中硬岩-软岩过渡区的FDEM输入参数
Table 3. Calculate FDEM input parameters of the hard-soft rock transition region in the model
单元
类型参数 干湿循环次数n 0(天然) 1 2 3 4 5 黏聚力
单元抗拉强度ft/MPa 1.5 1.4 1.3 1.2 1.1 1 黏聚力c/MPa 4 3.5 3 2.5 2 2 内摩擦角φ/(°) 15 14 13 12 11 10 Ⅰ型断裂能GⅠ/(J·m-2) 30 25 22 20 18 16 Ⅱ型断裂能GⅡ/(J·m-2) 60 50 44 40 36 32 初始法向刚度En/GPa 40 36.2 35 33.9 32.5 31 初始切向刚度Es/GPa 20 18.1 17.5 16.95 16.25 15.5 表 4 计算模型中的其他参数
Table 4. Calculate other parameters in the model
单元类型 参数 滑体 基岩 抗滑桩 实体单元 密度ρ/(kg·m−3) 2000 3000 2800 弹性模量E/GPa 4 100 25 泊松比ν 0.35 0.2 0.23 黏聚力单元 抗拉强度ft/MPa 1 − − 黏聚力c/MPa 3.5 − − 内摩擦角φ/(°) 22 − − Ⅰ型断裂能GⅠ/(J·m−2) 25 − − Ⅱ型断裂能GⅡ/(J·m−2) 50 − − 初始法向刚度En/GPa 8 − − 初始切向刚度Es/GPa 4 − − 法向接触刚度Pn/GPa 75 − − 切向接触刚度Ps/GPa 45 − − -
[1] 杨顺安,晏同珍. 预测滑坡学概要[J]. 中国地质灾害与防治学报,1998,9(增刊1):4-9.YANG S A,YAN T Z. Summary of prediction landslideology[J]. The Chinese Journal of Geological Hazard and Control,1998,9(S1):4-9. (in Chinese with English abstract [2] 汪发武,宋琨. 库水位涨落条件下不同结构边坡的变形破坏机制分析:以千将坪滑坡和树坪滑坡为例[J]. 工程地质学报,2021,29(3):575-582.WANG F W,SONG K. Analysis of deformation and failure mechanism of bank slopes with different structures under reservoir water level fluctuation:Taking Qianjiangping landslide and Shuping landslide as examples[J]. Journal of Engineering Geology,2021,29(3):575-582. (in Chinese with English abstract [3] 李长冬,谭钦文. 动水驱动型滑坡物理启滑能够预测吗?[J]. 地球科学,2022,47(10):3908-3910.LI C D,TAN Q W. Can the physical start-up of hydrodynamic landslide be predicted?[J]. Earth Science,2022,47(10):3908-3910. (in Chinese with English abstract [4] 丰月华,罗晓娟,李俊良,等. 上硬下软地层中h型桩与滑坡相互作用机理模型试验研究[J]. 地质科技通报,2022,41(6):242-252.FENG Y H,LUO X J,LI J L,et al. Physical model tests on the interaction of h-type stabilizing piles and landslides in bedrock with upper hard and lower weak strata[J]. Bulletin of Geological Science and Technology,2022,41(6):242-252. (in Chinese with English abstract [5] 王贵华,李长冬,贺鑫,等. 不同布锚方式对锚索抗滑桩受力与变形影响的物理模型试验研究[J]. 地质科技通报,2022,41(6):262-277.WANG G H,LI C D,HE X,et al. Physical model test on the effect of different anchoring methods on the mechanical and deformation characteristics of anchored slide-resistant piles[J]. Bulletin of Geological Science and Technology,2022,41(6):262-277. (in Chinese with English abstract [6] 王贵华,李长冬,陈文强,等. 复合多层滑床条件下锚索抗滑桩受力特征研究[J]. 岩石力学与工程学报,2019,38(11):2219-2230.WANG G H,LI C D,CHEN W Q,et al. Mechanical characteristics of anchored slide-resistant piles under the condition of composite multilayer sliding bed[J]. Chinese Journal of Rock Mechanics and Engineering,2019,38(11):2219-2230. (in Chinese with English abstract [7] 罗晓娟,寇桓嘉,祝国强,等. 断层破碎带条件下组合式圆截面抗滑桩加固边坡效果研究[J]. 地质科技通报,2022,41(6):253-261.LUO X J,KOU H J,ZHU G Q,et al. Effect of combined anti-slide piles with circular section to reinforce the slope containing the fault crushed zone[J]. Bulletin of Geological Science and Technology,2022,41(6):253-261. (in Chinese with English abstract [8] 王旋,胡新丽,周昌,等. 基于物理模型试验的滑坡-抗滑桩位移场变化特征[J]. 地质科技通报,2020,39(4):103-108.WANG X,HU X L,ZHOU C,et al. Model test on the displacement field characteristics of the landslide stabilizing piles[J]. Bulletin of Geological Science and Technology,2020,39(4):103-108. (in Chinese with English abstract [9] 唐雅婷,谭杰,李长冬,等. 基于模型试验的动水驱动型顺层岩质滑坡启滑机制初探[J]. 地质科技通报,2022,41(6):137-148.TANG Y T,TAN J,LI C D,et al. Preliminary study on the initiation mechanism of hydrodynamic-driven bedding rock landslides based on physical model tests[J]. Bulletin of Geological Science and Technology,2022,41(6):137-148. (in Chinese with English abstract [10] 叶海林,郑颖人,黄润秋,等. 强度折减动力分析法在滑坡抗滑桩抗震设计中的应用研究[J]. 岩土力学,2010,31(增刊1):317-323.YE H L,ZHENG Y R,HUANG R Q,et al. Study of application of strength reduction dynamic analysis method to aseismic design of anti-slide piles for landslide[J]. Rock and Soil Mechanics,2010,31(S1):317-323. (in Chinese with English abstract [11] 周云涛,石胜伟,蔡强,等. 基于能量损失的抗滑桩损伤模型及其应用[J]. 地质力学学报,2019,25(6):1107-1115.ZHOU Y T,SHI S W,CAI Q,et al. Damage model of anti-slide pile based on energy loss and its application[J]. Journal of Geomechanics,2019,25(6):1107-1115. (in Chinese with English abstract [12] 咸玉建,陈学军,汪志刚,等. 基于有限元强度折减系数法岩土边坡稳定性分析与抗滑桩设计[J]. 地质科技情报,2015,34(4):176-182.XIAN Y J,CHEN X J,WANG Z G,et al. Geotechnical slope stability analysis and the design of anti-slide pile based on strength reduction FEM[J]. Geological Science and Technology Information,2015,34(4):176-182. (in Chinese with English abstract [13] 张晓平,王思敬,王幼明,等. 二维离散元模拟抗滑桩的折算方法研究[J]. 岩土工程学报,2010,32(2):271-278.ZHANG X P,WANG S J,WANG Y M,et al. Conversion of anti-sliding piles into 2-dimensional discrete element simulation[J]. Chinese Journal of Geotechnical Engineering,2010,32(2):271-278. (in Chinese with English abstract [14] 赵健,杨立,邓冬梅,等. 基于3DEC对某输电线路新建铁塔岩质边坡的稳定性评价[J]. 安全与环境工程,2018,25(2):55-60.ZHAO J,YANG L,DENG D M,et al. Stability evaluation with 3DEC for the rock slope under a newly-built transmission line tower[J]. Safety and Environmental Engineering,2018,25(2):55-60. (in Chinese with English abstract [15] MAHABADI O K,LISJAK A,MUNJIZA A,et al. Y-geo:New combined finite-discrete element numerical code for geomechanical applications[J]. International Journal of Geomechanics,2012,12(6):676-688. doi: 10.1061/(ASCE)GM.1943-5622.0000216 [16] ELMO D,STEAD D,EBERHARDT E,et al. Applications of finite/discrete element modeling to rock engineering problems[J]. International Journal of Geomechanics,2013,13(5):565-580. doi: 10.1061/(ASCE)GM.1943-5622.0000238 [17] MUNJIZA A. The combined finite-discrete element method[M]. New York:John Wiley & Sons,2004. [18] LEI Q H,LATHAM J P,XIANG J S. Implementation of an empirical joint constitutive model into finite-discrete element analysis of the geomechanical behaviour of fractured rocks[J]. Rock Mechanics and Rock Engineering,2016,49(12):4799-4816. doi: 10.1007/s00603-016-1064-3 [19] WU Z J,ZHANG P L,FAN L F,et al. Numerical study of the effect of confining pressure on the rock breakage efficiency and fragment size distribution of a TBM cutter using a coupled FEM-DEM method[J]. Tunnelling and Underground Space Technology,2019,88:260-275. doi: 10.1016/j.tust.2019.03.012 [20] YAN C Z,ZHENG H. FDEM-flow3D:A 3D hydro-mechanical coupled model considering the pore seepage of rock matrix for simulating three-dimensional hydraulic fracturing[J]. Computers and Geotechnics,2017,81:212-228. doi: 10.1016/j.compgeo.2016.08.014 [21] 陶志刚,张海江,尹利洁,等. 基于FDEM的戒台寺古滑体开裂破坏过程数值模拟[J]. 水文地质工程地质,2017,44(3):105-112.TAO Z G,ZHANG H J,YIN L J,et al. Numerical modeling of cracking for the Jietai temple ancient landslide with the combined finite-discrete element method[J]. Hydrogeology & Engineering Geology,2017,44(3):105-112. (in Chinese with English abstract [22] SUN L,LIU Q S,ABDELAZIZ A,et al. Simulating the entire progressive failure process of rock slopes using the combined finite-discrete element method[J]. Computers and Geotechnics,2022,141:104557. doi: 10.1016/j.compgeo.2021.104557 [23] WANG J G,WANG S,SU A J,et al. Simulating landslide-induced tsunamis in the Yangtze River at the Three Gorges in China[J]. Acta Geotechnica,2021,16(8):2487-2503. doi: 10.1007/s11440-020-01131-3 [24] CHEN X D,WANG H F. Slope failure of noncohesive media modelled with the combined finite–discrete element method[J]. Applied Sciences,2019,9(3):579. doi: 10.3390/app9030579 [25] BAO Y D,CHEN J P,SU L J,et al. A novel numerical approach for rock slide blocking river based on the CEFDEM model:A case study from the Samaoding paleolandslide blocking river event[J]. Engineering Geology,2023,312:106949. doi: 10.1016/j.enggeo.2022.106949 [26] 张柏楠,韩勃,代松,等. 基于FDEM的大型海上风机嵌岩单桩基础水平承载特性研究[J]. 岩石力学与工程学报,2023,42(增刊1):3309-3323.ZHANG B N,HAN B,DAI S,et al. Research on the lateral capacity characteristics of rock-socketed single-pile foundation for large offshore wind turbines based on FDEM[J]. Chinese Journal of Rock Mechanics and Engineering,2023,42(S1):3309-3323. (in Chinese with English abstract [27] 刘洋,吴志军,储昭飞,等. 基于FDEM的围压条件下机械冲击破岩机理研究[J]. 中南大学学报(自然科学版),2023,54(3):866-879.LIU Y,WU Z J,CHU Z F,et al. Rock breaking mechanism with mechanical impact under confining pressure based on FDEM[J]. Journal of Central South University(Science and Technology),2023,54(3):866-879. (in Chinese with English abstract [28] GRIFFITH A A. The phenomena of rupture and flow in solids[J]. Philosophical Transactions of the Royal Society of London Series A,Containing Papers of a Mathematical or Physical Character,1921,221:163-198. [29] 孙秋荣. 基于FDEM的混凝土开裂破坏过程的数值模拟[J]. 水利水电技术(中英文),2021,52(7):192-199.SUN Q R. Numerical simulation of cracking and failure process of concrete based on FDEM[J]. Water Resources and Hydropower Engineering,2021,52(7):192-199. (in Chinese with English abstract [30] 程树范,曾亚武,高睿,等. 黏土岩中水泥锚固体滑脱的有限-离散元模型初探[J]. 岩土工程学报,2023,45(12):2594-2603.CHENG S F,ZENG Y W,GAO R,et al. Finite-discrete element model for slip debonding of cement anchors in clay rock[J]. Chinese Journal of Geotechnical Engineering,2023,45(12):2594-2603. (in Chinese with English abstract [31] TATONE B S A,GRASSELLI G. A calibration procedure for two-dimensional laboratory-scale hybrid finite-discrete element simulations[J]. International Journal of Rock Mechanics and Mining Sciences,2015,75:56-72. doi: 10.1016/j.ijrmms.2015.01.011 [32] LIU Q S,DENG P H. A numerical investigation of element size and loading/unloading rate for intact rock in laboratory-scale and field-scale based on the combined finite-discrete element method[J]. Engineering Fracture Mechanics,2019,211:442-462. doi: 10.1016/j.engfracmech.2019.02.007 [33] LISJAK A,GRASSELLI G,VIETOR T. Continuum-discontinuum analysis of failure mechanisms around unsupported circular excavations in anisotropic clay shales[J]. International Journal of Rock Mechanics and Mining Sciences,2014,65:96-115. doi: 10.1016/j.ijrmms.2013.10.006 [34] 邓鹏海,刘泉声,黄兴. 基于Weibull分布的非均质隧洞围岩破裂碎胀FDEM数值模拟研究[J]. 工程力学,2024,41(7):40-59.DENG P H,LIU Q S,HUANG X. Fdem numerical study on the fracture and swelling deformation of heterogeneous rock mass around tunnel based on weibull distribution[J]. Engineering Mechanics,2024,41(7):40-59. (in Chinese with English abstract [35] 姚文敏. 基于水致岩体劣化的三峡库区侏罗系地层水库滑坡抗滑桩嵌固机理及其优化研究[D]. 武汉:中国地质大学(武汉),2020.YAO W M. Embedded mechanism and optimization of stabilizing piles for reservoir landslides in Jurassic strata of Three Gorges Reservoir region considering water induced deterioration of rock mass[D]. Wuhan:China University of Geosciences(Wuhan),2020. (in Chinese with English abstract [36] YAO W M,LI C D,ZHAN H B,et al. Multiscale study of physical and mechanical properties of sandstone in Three Gorges Reservoir Region subjected to cyclic wetting-drying of Yangtze River water[J]. Rock Mechanics and Rock Engineering,2020,53(5):2215-2231. doi: 10.1007/s00603-019-02037-7 [37] 董曼曼,王亮清,葛云峰,等. 考虑滑床复合倾斜岩体综合地基系数的抗滑桩受力特征研究[J]. 岩土力学,2017,38(10):3000-3008.DONG M M,WANG L Q,GE Y F,et al. Mechanical characteristics of anti-sliding pile considering comprehensive foundation coefficient of sliding bed on composite inclined rock mass[J]. Rock and Soil Mechanics,2017,38(10):3000-3008. (in Chinese with English abstract [38] 唐辉明,李长冬,龚文平,等. 滑坡演化的基本属性与研究途径[J]. 地球科学,2022,47(12):4596-4608.TANG H M,LI C D,GONG W P,et al. Fundamental attribute and research approach of landslide evolution[J]. Earth Science,2022,47(12):4596-4608. (in Chinese with English abstract [39] 吴丹丹,胡新丽,雍睿,等. 三峡库区马家沟滑坡模型形态概化[J]. 地球科学,2014,39(11):1693-1698.WU D D,HU X L,YONG R,et al. Generalizability method of physical model shape for Majiagou landslide in Three Gorges Reservoir area[J]. Earth Science,2014,39(11):1693-1698. (in Chinese with English abstract -