【作者】 李烨；

【导师】 殷坤龙；

【作者基本信息】 中国地质大学 ， 地质工程， 2021， 博士

【摘要】 在三峡库区中,沿库岸发育了大量滑坡,其中超过2500处受库水波动影响,这些滑坡一旦失稳入水,有可能会引发次生涌浪灾害,从而扩大灾害的影响范围,并造成更严重的灾害后果。针对库区的这类滑坡灾害链,传统的地质成因机理、工程治理技术等方面的研究,较难满足其综合防灾减灾的需求。而开展滑坡灾害链的风险研究,能够综合考虑灾害的危险性和潜在后果,进而有针对性地实施风险控制,有助于高效率、低成本地开展防治工作。论文以三峡库区单体滑坡涌浪灾害链的风险为研究对象,基于库区滑坡灾害风险计算的改进公式,结合凉水井滑坡风险管理的成功经验,通过对滑坡及涌浪灾害风险研究框架的整合与补充,构建了适合于库区单体滑坡及潜在灾害链的风险管理体系;以三峡库区重庆市云阳县凉水井滑坡为例,总结了滑坡变形的时空规律与影响因素,开展了在不同组合工况下滑坡及其次生灾害的风险定量计算,并基于滑坡的风险特征提出了四种风险控制方案,开展了方案比选与组合方案分析,探讨了灾害链风险对控制措施的反馈情况。主要研究内容和成果如下:（1）通过对灾害风险管理的理论研究,整合了滑坡和涌浪的风险研究框架,基于库区滑坡灾害风险计算改进公式,构建了适用于三峡库区单体滑坡诱发灾害链的定量化风险管理体系。该体系主要包括资料收集与风险识别、危险性分析、灾害后果分析、风险计算、风险控制五个步骤。（1）开展风险管理研究前,应收集整理研究区基础地质资料、气象水文资料、滑坡勘察与监测资料、潜在承灾体的调查资料等。并对滑坡的发育情况、变形特征、破坏模式开展研究,分析滑坡在诱发因素影响下的变形规律,从而确定定量化风险研究的工况组合。（2）以灾害的发生概率表示其危险性,基于灾种间的链式作用和发生时序关系,简化了次生涌浪灾害的发生概率计算,然后应开展滑坡运动特征分析和次生涌浪预测,从而确定灾害的影响范围和用于后续灾害强度计算的基本参数。（3）以各类承灾体易损性与其经济价值乘积的总和表示灾害后果,将承灾体按照与灾害的相对位置分为了滑坡体上的、岸边静态、水上静态和水上动态四类,通过对规范设计值、经验关系和数值模拟结果等资料的研究,针对每一类承灾体分别提出了相应的估算公式以量化其易损性值。（4）针对经典滑坡风险计算公式,补充了次生涌浪灾害的间接风险,可采用风险图谱表达滑坡灾害链中多灾种和多种类型承灾体综合风险的大小与分布情况。（5）对风险成果的应用进行研究,总结了风险决策的适用条件,可采用残余风险来衡量滑坡灾害链对风险控制方案的反馈情况,并根据主体工程的服役期与成本,将原风险与残余风险的差值视为风险收益,通过成本-效益公式对方案进行择优,构建了较为完善的库区单体滑坡涌浪灾害链的风险管理框架。（2）以重庆市云阳县凉水井滑坡为例,对其潜在的灾害链开展了较为完整的风险管理研究,从一定程度上验证了该定量化风险管理体系的有效性。（1）分析了凉水井滑坡的发育特征与变形规律。该滑坡所在的砂泥互层（J₂s）是典型的易滑岩组,基于地质资料、野外调查和监测数据,总结了其发育机制、变形特征和破坏模式,认为凉水井滑坡边界已基本贯通,中前部和右侧后缘变形相对剧烈,在2009-2014年期间变形受库水位和降雨影响较为明显;对滑坡地表位移矢量进行了理论分析,判断滑坡破坏模式更偏向于旋转破坏;通过构建滑坡地表位移与潜在诱发因素之间的相关性模型,探讨了滑坡变形的时序特征,当月库水位平均值对当月滑坡位移的贡献最大,约51%,当月累积降雨量贡献约29%,库水位越低、水位变化越快、降雨量越大时,滑坡位移增量越大。（2）开展了凉水井滑坡及其潜在次生涌浪灾害的危险性分析。基于滑坡变形对诱发因素的响应规律,构建了风险研究的工况体系,将库水位按照年度调度分为了高水位、水位下降、水位快速下降、低水位和水位上升五个阶段,基于频率分析确定了10年、20年、50年一遇对应的降雨极值;通过有限元模拟软件Geo-Studio计算了不同工况组合中凉水井滑坡的破坏概率,从而确定了灾害的发生概率,在水位快速下降阶段,滑坡的破坏概率最大,同时降雨极值越大,破坏概率越大;采用Tsunami Squares软件开展了滑坡的run-out分析与次生涌浪预测,分析了滑坡失稳后的运动特征和涌浪传播规律,发现在降雨+水位快速下降的组合工况下,滑坡速度峰值、正对岸爬坡浪峰值和沿河道的传播浪峰值均达到最大,所得结果也为后续易损性分析提供了参数基础。（3）量化了凉水井滑坡及其潜在次生涌浪灾害的承灾体易损性,完成了灾害后果评价。根据危险性分析中对滑坡及其次生灾害影响范围的预测,调查统计研究区内潜在承灾体的类型、数量、分布及经济价值等信息,确定了滑坡体上有林地和道路两种承灾体,水上静态型承灾体有两处临时码头和系泊船只,水上动态型承灾体为在长江上航行的船只;认为坡体上的承灾体易损性为1,其它类型承灾体则依据危险性分析中的涌浪预测,由相应公式分别估算其抗灾能力和灾害作用强度,从而得到易损性定量化结果;由各类承灾体易损性与其经济价值乘积的总和得到,滑坡的直接灾害后果约为235万元,其潜在次生灾害的间接后果最大约为3321万元。（4）计算与展示了凉水井滑坡的直接风险和来自潜在次生涌浪灾害的间接风险。基于前述危险性与易损性的量化结果,通过风险计算改进公式计算滑坡灾害链的总风险,结果显示,由次生涌浪引起的间接风险约是滑坡直接风险的11倍,风险表达图也清晰地显示灾害链风险主要集中在长江及沿岸,由此可见潜在次生涌浪将大大扩大滑坡灾害的影响范围、提高其威胁程度;库水位的涨落及移动的承灾体的存在,使得滑坡灾害链风险呈动态变化,在50年一遇降雨+水位快速下降阶段的组合工况中,风险值达到最大约2265万元;考虑降雨时间概率联合库水位周期性特征时,能从一定程度上反映灾害链风险的长期变化趋势,随着时间推移,凉水井滑坡灾害链的总风险将持续升高,但增幅并不明显。（5）探讨了凉水井滑坡诱发灾害链风险控制的流程与方案比选办法。根据凉水井滑坡灾害链的风险特征,即主要风险为间接风险,拟定滑坡开展降低灾害发生概率、躲避风险、减少灾害后果的风险决策,提出了抗滑桩、削方、截排水、监测预警四种独立治理方案,重新开展了灾害链风险分析计算其残余风险,其中削方方案中的残余风险最低,相比未治理时降低了约69%,抗滑桩方案中残余风险也降低了约67%,但增加抗滑桩排数并没有使残余风险显著降低,说明以抗滑桩为主体工程的传统防治方案可能存在风险控制的瓶颈;通过成本-效益公式,计算了各方案的效益成本率,其中由于削方工程能提高滑坡稳定性、降低运动速度、减少入江方量,同时是对坡体的永久改造,且成本较低,因此不论考虑封航与否都是最优方案;当将四种独立方案组合在一起时,灾害链的残余风险最低,相比未治理时降低了89%,比独立方案中残余风险降低了65～88%,而削方与排水工程相结合的组合方案是最优方案;2014年,对凉水井滑坡实际实施的主体治理方案即为削方工程,相比原定的抗滑桩工程节省了约80%的经费,且滑坡地表变形速度降低了约47%,说明从风险管理的角度对库区滑坡开展防治工作具有一定的实际意义和良好的经济效益,也从一定程度上验证了本文所提出的风险管理研究框架具有一定的有效性与实用性。更多还原

【Abstract】 In the Three Gorges Reservoir area,there are many landslides developing along the river banks.More than 2500 of the landslides are influenced by the reservoir water fluctuation.Once the landslides fail and slip into the water body,they may trigger secondary wave hazards,which can significantly expand the influence scope and result in more serious consequences,compared with independent landslide hazards.However,traditional research on geological mechanism and engineering mitigation technology is not enough to meet the needs of comprehensive prevention and mitigation of the potential hazard chains triggered by the reservoir landslides.In general,the study on geological hazard risk includes both hazard analysis of the hazard and vulnerability analysis of the potential elements at risk,and this comprehensive perspective helps to highly efficient and cost-effective prevention and mitigation works.The article takes the risk of landslide triggered hazard chain in the Three Gorges Reservoir area at a specific-site scale as the research object.The risk management system of an individual landslide and its triggered hazard chain in the Three Gorges Reservoir area is constructed through the integration and supplementation of the research frameworks of landslide and tsunami risk,based on the improved equation calculating landslide direct and indirect risk and the successful risk management of the Liangshuijing landslide;taking the Liangshuijing landslide in Yunyang County,Chongqing City as an example,the spatial and temporal trends and triggering factors of the landslide deformation are summarized,the direct risk of the landslide and the indirect risk of its secondary wave hazard under different scenario combinations are calculated quantitatively,then based on the landslide risk characteristics,four risk control plans are proposed and the optimal one is selected through the cost-benefit analysis,after that the feedback of potential hazard chain risks on control measures is discussed.The main contents and results are as follows:(1)Through the theoretical study of hazard risk management,the research framework of landslide and tsunami risk is integrated,and the quantitative risk management system applicable to the landslide triggered hazard chain in the Three Gorges Reservoir area is constructed based on the improved equation of classical landslide risk calculation.The system mainly includes five steps: data collection,hazard analysis,consequence analysis,risk calculation,and risk control.(1)Before the research of risk management,the basic geological data,meteorological and hydrological data,landslide investigation and monitoring data,and investigation and statistics data of potential elements at risk in the study scope should be collected.Then,the development,deformation characteristics and failure mechanism of the landslide should be analyzed,and the influence of triggering factors on landslide surface displacement should be studied,so as to determine the scenario combinations for the quantitative risk management.(2)The occurrence probability is used to represent the hazard of the landslide and secondary wave.Based on the time sequence and chain effect of hazard occurrence,the calculation of occurrence probability of the potential landslide-triggered wave is simplified.Then the landslide runout analysis and secondary wave prediction should be carried out,which will be used to outline the impact area of the hazard chain and determine the movement parameters for the hazard intensity calculation in subsequent step.(3)The hazard consequence is represented by the sum of the vulnerability of each type of element at risk multiplying its economic estimates.The elements at risk are divided into four types according to their relative positions to the hazard: on the landslide body,static on-shore,static on-water and dynamic on-water.Based on the study of normative design values,empirical relationships and numerical simulation results,the corresponding estimation equations to quantify vulnerability are proposed for all types of elements at risk.(4)The indirect risk caused by secondary wave is added to the classical landslide risk calculation equation.The magnitude and distribution of the comprehensive risk of multiple types of hazard and elements at risk can be shown on risk maps.(5)The practical application of risk results is studied,and the applicable conditions of different risk decisions are summarized.The residual risk can be used to measure the feedback of the landslide hazard chain on the risk control plan.Then based on the service period and cost of main project,the optimization of risk control plan is carried out through the improved cost-benefit analysis where the risk benefit is represented by difference between the original and residual risk values.Thus,a relatively complete risk management research system of landslide triggered hazard chain in the Three Gorges Reservoir area at a specific-site scale has been constructed.(2)Taking the Liangshuijing landslide in Yunyang County,Chongqing City as an example,a relatively complete risk management research of its triggered hazard chain is carried out,which has verified the effectiveness of the improved quantitative risk management framework to a certain extent.(1)The analysis of the development characteristics and deformation trends of the Liangshuijing landslide.The landslide is located in the interbedded sandstone and mudstone of the middle Jurassic Shaximiao formation which is one of the typical rock formations being prone to slip.Based on the geological data,investigation and monitoring data,the development,deformation characteristics and failure mechanism of the landslide are analyzed.The landslide boundary had been generally formed,the cumulative surface displacements of the middle front and right part near the landslide head were larger than those of other parts,and during 2009-2014 the landslide deformation was obviously affected by the reservoir level and rainfall.The theoretical analysis of the cumulative displacement vectors indicates that the landslide follows a rotational failure mechanism.Based on the correlation analysis between landslide displacement and triggering factors,the time-series characteristics of the landslide deformation were analyzed.The results show that the averaged reservoir water level in the current month contributes about 51 %(the most)to the displacement in the current month,while the cumulative precipitation in the current month contributes about 29 %.The lower the reservoir level,the faster the reservoir level change and the larger the precipitation,the greater the increment of the landslide displacement.(2)The hazard analysis of the Liangshuijing landslide and its potential secondary wave hazard.Based on the response regulations of the landslide deformation to the triggering factors,the scenario system for quantitative risk management is constructed,where the reservoir level is divided into five stages(high water level,drawdown,rapid drawdown,low water level,and rising stage)and the rainfall conditions are corresponding rainfall extremes of 10,20,and 50 years.The failure probability of the landslide under different scenarios is calculated by the finite element numerical simulation software Geo Studio,and the results show that in the rapid drawdown stage the failure probability has a maximum and the greater the rainfall the larger the failure probability.Based on the runout analysis of the landslide and the prediction of the potential landslide-triggered wave simulated by the Tsunami Squares software,the landslide movement characteristics and wave propagation are analyzed,and the results show that in the combination scenario of rainfall + rapid drawdown stage,the peak values of landslide velocity,the run-ups on the shore directly opposite the landslide and the wave heights in the navigation channel are all reached the maximum.(3)The quantitative vulnerability analysis of the elements at risk and consequence analysis of the Liangshuijing landslide and its potential secondary wave.According to the prediction of the impact area of the landslide and its secondary wave in the earlier hazard analysis,the investigation of the type,quantity,location and economic value of the potential elements at risk are conducted.There are a piece of forest land and a road on the landslide body.Two temporary piers and the moored vessels are static on-water,and the vessels moving on the river with uncertain spatial and temporal distributions are dynamic on-water.To quantify the vulnerability of the elements at risk,that of the elements at risk on the landslide body is regarded as 1,while that of other types are estimated through the corresponding equations calculating the resistance and hazard intensity based on the prediction of the wave propagation.The direct consequence of the landslide is about 2.35 million RMB,and the maximum indirect consequence of its potential secondary wave is about 33.21 million RMB.(4)The risk calculation and mapping of the Liangshuijing landslide and its secondary wave.The total risk of the landslide triggered hazard chain is calculated by the improved risk equation.The results show that the indirect risk due to the secondary wave is about11 times of the direct risk due to the landslide itself,and the risk maps also clearly show that the risk of the hazard chain is mainly concentrated in the Yangtze River and along the river bank.The potential secondary wave can greatly expand the influence area of the landslide and increase it threat level.The fluctuation of the reservoir level and the existence of moving elements at risk make the risk of the landslide triggered hazard chain change dynamically.The total risk has a maximum of 22.65 million RMB in the combined scenario of rainstorm once in 50-year and rapid drawdown stage of the reservoir water level.Considering the temporal probability of rainfall and periodic characteristics of the reservoir water level in the risk analysis can reflected the long-term trend of hazard chain risk to a certain extent.The total risk of the landslide triggered hazard chain continues to rise over time,but at a smaller rate.(5)The re-analysis of the landslide triggered hazard chain under different risk control plans and plan comparison through a cost-benefit analysis.According to the risk characteristics of the Liangshuijing landslide triggered hazard chain,i.e.,the main risk is indirect risk,the risk decision of decreasing the occurrence probability,avoiding the risk and reducing the hazard consequence is made,and four mitigation projects(anti-slip piles,cutting,drainage,and monitoring)are proposed to control the risk.The results of the re-analysis of the hazard chain risk show that,the residual risk of hazard chain after being taken the cutting project is reduced by about 69 %compared with the original total risk is the lowest,while that after being taken the antislip piles project is reduced by about 67 %.However,increasing the number of pile rows does not significantly reduce the risk,indicating that the traditional mitigation plan with anti-slip piles as the main project may have a bottleneck of risk control effect.Through the cost-benefit equation,the benefit-cost ratio of each plan is calculated.Conducting the cutting project can improve the landslide stability,reduce the volume sliding into the water body,and transform the slope shape almost permanently,meanwhile the cost is relatively low,thus it is the optimal plan whether navigation closure is considered or not.Additionally,the residual risk of the hazard chain is the lowest after being taken the combination of the four independent projects,with a reduction of about 89 % and 65 ～88 % compared to the original total risk and the residual risk under the four independent projects,respectively.In fact,the Liangshuijing landslide was conducting cutting project in 2014,which saved about 80 % of the cost compared with the original anti-slip project.After mitigation,the surface velocity is reduced by about 47 %.Therefore,it is of practical significance and economic benefits to carry out landslide prevention work in the reservoir area from the perspective of risk management,and the effectiveness and practicality of the improved risk management framework are verified to some extent.更多还原