冻融循环作用下危岩体滑移破坏数值优化分析_舒佳军.pdf

复杂艰险山区重大工程与环境DOI:10.15961/j.jsuese.202200696冻融循环作用下危岩体滑移破坏数值优化分析舒佳军1，邓正定1*，黄晶柱1，伍冰妮2，张兴秋1(1.江西理工大学 江西省环境岩土与工程灾害控制重点实验室，江西 赣州 341000；2.华东交通大学 省部共建轨道交通基础设施性能监测与保障国家重点实验室，江西 南昌 330013)摘要：冻融循环作用是寒区危岩体崩塌失稳的主要诱因，对寒区危岩体滑移破坏的孕灾因素进行数值优化分析尤为重要。首先，基于极限平衡理论，考虑危岩体贯通段结构面冻胀力、未贯通段岩石黏聚力劣化及冻结深度演化，建立冻融循环作用下滑移式危岩体稳定性分析模型；其次，基于岩石冻胀理论，考虑冻结过程中水分迁移推导得到贯通段冻胀力计算方法；再次，将岩石细观孔隙抽象为无数圆形孔洞，根据圆孔扩张理论和莫尔库伦屈服准则分析孔隙冻胀破坏过程，构建冻融循环作用下未贯通段岩石黏聚力细观劣化模型；最后，通过改进Stephan经验公式得到未贯通段岩石冻结深度随冻融循环次数演化的计算方法。结合工程算例分析各敏感参数对危岩体稳定性的影响发现：滑移式危岩体稳定性随冻融循环次数的增加呈先快后缓的下降趋势；危岩体稳定性系数与冻结温度呈正相关，相同冻结温度下，危岩体稳定性系数的下降随冻融循环次数增加出现明显的边际递减效应；危岩体稳定性系数与岩屑流失比呈负相关，且岩屑流失比会同时改变稳定性劣化趋势和劣化程度，控制岩屑流失比有利于寒区危岩体的长期稳定性。关键词：冻融循环；极限平衡；冻胀力；细观劣化；冻结深度；岩屑流失中图分类号：TU45文献标志码：A文章编号：2096-3246（2023）02-0059-11Numerical Optimization Analyses of Dangerous Rock Mass Sliding Failure Under Freeze-thaw CyclesSHU Jiajun1，DENG Zhengding1*，HUANG Jingzhu1，WU Bingni2，ZHANG Xingqiu1(1.Jiangxi Province Key Lab.of Environmental Geotechnical Eng.and Hazards Control,Jiangxi Univ.of Sci.and Technol.,Ganzhou 341000,China;2.State Key Lab.for Performance Monitoring and Guarantee of Rail Transportation Infrastructure,East China Jiaotong Univ.,Nanchang 330013,China)Abstract:The action of freeze-thaw(FT)cycles is the main inducement for the collapse and instability of dangerous rock mass in cold regions,and it is particularly important to carry out numerical optimization analysis on the disaster pregnant factors of sliding failure of dangerous rockmass in cold regions.Firstly,based on the limit equilibrium theory,the stability analysis model of sliding dangerous rock mass under the action ofFT cycles was established by considering the frost heave force of through section structural plane,the deterioration of the cohesive force of thelocked section,and the evolution of the freezing depth.Secondly,based on the theory of rock frost heave and considering the water migration dur-ing the freezing process,the calculation method of the frost heave force of the through structural plane section was derived.Thirdly,the meso-scopic defects of rock were simplified to numerous circular pores.According to the expansion theory of circular pores and the MohrCoulombyield criterion,the process of pore frost heave failure was analyzed,and the meso degradation model of rock cohesion in the non-penetrated sec-tion under the action of the freeze-thaw cycle was constructed.Finally,the calculation method of the evolution of the rock freezing depth of thelocked section with the number of FT cycles was obtained by improving Stephans empirical formula.Combined with the engineering calcula-收稿日期:2022 07 07基金项目:江西省自然科学基金项目（20202BAB214025；20224BAB213045）；江西省教育厅科研技术项目（GJJ200871）；江西理工大学高层次人才启动项目（205200100486）；江西省研究生创新专项资金项目（XY2021S025）作者简介:舒佳军（1998），男，硕士生.研究方向：边坡稳定性.E-mail：*通信作者:邓正定，讲师，E-mail：网络出版时间:2023 02 06 11:19:33 网络出版地址:https:/ http:/http:/ 第 55 卷 第 2 期工 程 科 学 与 技 术Vol.55 No.22023 年 3 月ADVANCED ENGINEERING SCIENCESMar.2023tion example to analyze the influence of each sensitive parameter on the stability of the dangerous rock body,it was found that the stability of slid-ing dangerous rock mass showed a fast and then slowly declined with the increase of the number of FT cycles.The stability coefficient of slid-ing dangerous rock mass was positively correlated with the freezing temperature.At the same freezing temperature,the stability coefficient de-creased with the increase of the number of FT cycles with a significant marginal decreasing effect.The stability of dangerous rock mass was neg-atively correlated with the rock debris loss ratio,and the rock debris loss ratio changed both the trend of stability deterioration and the degree ofdeterioration.Controlling the rock debris loss ratio was conducive to the long-term stability of the dangerous rock mass in cold regions.Key words:freeze-thaw cycles;limit equilibrium;frost heave force;mesoscopic deterioration;freezing depth;rock debris loss 中国冻土区域面积约为国土面积的3/4，是世界上寒区分布最广的国家之一。冻融循环引起的危岩体滑移破坏是寒区主要地质灾害之一，如：西藏甲玛矿山边坡由于冻融损伤致使岩体劣化失稳，引起200多万立方米的边坡岩体塌方1；新疆西北部山区遭受强烈的冻融循环作用，山体岩石破碎严重，进而出现落石、滑移等不良地质现象2。评价危岩体稳定性的核心问题是建立能够反映危岩体当前力学状态及后续发展规律的理论模型。Chen等34根据危岩体失稳破坏模式，将其分为滑移式、倾倒式和坠落式3类，并通过极限平衡理论分析了不同工况下危岩体稳定性变化规律。根据极限平衡理论可知，危岩体破坏的实质是结构面及岩石抵抗力与破坏力的博弈56。因此，揭示结构面及岩块在冻融循环作用下力学性能的劣化机理对寒区危岩体稳定性合理评价至关重要。Heinze等7认为冻融循环作用导致岩石平衡态被破坏时，会出现传热现象，将传热系数表征为计算参数是解决危岩体冻融问题的关键。Chen等8发现滑移式危岩体稳定性劣化主要源于岩块部分黏聚力的劣化，黏聚力随冻融循环次数的增加呈指数形式降低。Chen等9在冻融循环试验中发现危岩体岩块损伤主要由表面缺陷组成，在冻融作用下缺陷长期发展，导致载荷能力逐渐降低进而引起危岩体崩塌破坏。Qiao等10通过力学分析和冻融循环试验研究了危岩体锁固段岩石的破坏机理，认为危岩体稳定性与结构面两侧的岩石刚度比相关，并建立了危岩体尖点突变预测模型。Yang等11选取鸭绿江公路边坡危岩进行冻融循环试验和数值分析研究，发现冻融循环对岩石力学性能的折减是危岩体长期稳定性劣化的主要因素。目前，对冻融循环作用下危岩体的稳定性分析主要集中在对危岩体进行现场监测1213，或对局部岩块试样进行室内冻融试验1416，在理论机制上对寒区危岩体稳定性的分析值得进一步探索。因此，本文在前人基础上，将圆孔扩张理论与莫尔库伦屈服准则相结合，考虑结构面冻胀力、未贯通段岩石黏聚力劣化、冻结深度演化等参数影响，建立冻融循环作用下的滑移式危岩稳定性系数计算方法，并对相关敏感参数进行优化分析，研究成果可为寒区危岩体工程安全与防治提供理论参考。1 冻融循环下滑移式危岩体稳定性力学模型寒区危岩体中普遍存在岩体冻融现象，岩体内部的水分在气温交替变化下不断冻结及融化。实际上，裸露在危岩体表面并与外界接触的岩石均存在冻结区，但滑移式危岩体的稳定性主要由其主控面控制，故本文仅考虑主控面处岩体冻结深度的影响。因此，冻融循环对危岩体的破坏主要作用在其主控面上，具体表现为在贯通段产生冻胀力、在未贯通段弱化岩体力学性能及加剧岩石冻结深度，如图1所示。基于极限平