【作者】 李宏伟；

【导师】 胡冉； 陈益峰；

【作者基本信息】 武汉大学 ， 水工结构工程， 2024， 硕士

【摘要】 我国地形地貌复杂多样,季风气候显著,在暴雨诱发和人类工程活动影响之下,滑坡灾害呈现分布广、频率高、危害大等显著特征。开展降雨条件下滑坡渗流场动态特征及其对稳定性的影响研究,对滑坡灾害防治具有重要理论意义和应用价值。本文以江坪河水电站梅家台滑坡为研究对象,以滑坡治理工程长期稳定性评价为目标,综合运用现场监测、数值模拟和反馈分析等方法,深入研究了滑坡渗流场的演变规律,揭示了开挖、加固、排水等工程治理措施对滑坡稳定性的影响,系统评价了滑坡治理工程的稳定性。主要研究工作和成果如下:(1)研究了滑坡的物质组成和地下水的赋存特征,揭示了梅家台滑坡的成因机制通过工程地质及水文地质条件分析,查明了梅家台滑坡的物质组成和地下水赋存特征,进而通过对2007年特大暴雨期间滑坡过程的分析,揭示了滑坡的类型和成因机制。研究表明,滑坡自上而下分为残坡积土体、相对完整岩体、老滑带和基岩层,老滑带具有相对阻水性,因而在后缘岩溶地下水和地表降雨入渗补给作用下,滑坡内赋存孔隙潜水、裂隙潜水和裂隙承压水三种类型的地下水;滑坡属于典型的降雨型堆积体滑坡,其后缘崩塌累积的斜坡堆积物为滑坡提供了物质条件,岩土分界面为滑坡提供了滑动镜面,而暴雨期降雨入渗和地下水位抬升则诱发了沿残坡积土体和相对完整岩体分界面的牵引式破坏。(2)开展了滑坡渗流场的数值模拟和反馈分析,揭示了梅家台滑坡渗流场的动态演变规律结合长历时的渗流监测数据,动态反演了滑坡后缘的边界水位和各地层的渗流参数,进而分析了天然状态、抢险状态和治理状态下饱和-非饱和渗流场的动态演化特征,率定了滑坡的降雨入渗补给系数;在此基础上,开展了考虑降雨入渗的滑坡三维非稳定渗流过程的计算分析,综合评价了滑坡的排水治理效果。研究表明,渗流场计算结果与孔压测点的实测值变化趋势基本一致,后缘水位的动态反演结果可靠,岩土体渗流参数取值合理;在降雨入渗和后缘动态水位的联合补给作用下,雨季坡体的地下水位显著抬升,坡脚有溢出现象,暴雨期则在中部堆积薄弱带和下部坡脚处出现大范围饱和区;随着排水措施的逐步实施,雨季坡体内地下水位下降9.2～16.5 m,水位保持较低水平,排水洞流量对降雨响应迅速,且能在暴雨期有效抑制饱和区的扩展,表明排水措施布置合理,坡体地下水位和渗流场得到有效控制。(3)揭示了自滑坡发生以来滑坡体稳定性的变化规律,定量评估了梅家台滑坡的综合治理效果基于渗流分析结果,采用极限平衡法和强度折减法,分析了天然状态、抢险状态和治理状态下滑坡稳定性的演化规律,量化了开挖清淤、支护加固和排水降压等治理措施对稳定性的贡献,进而结合滑坡监测资料综合评估了滑坡治理工程的稳定性。研究表明,天然状态下,暴雨使滑坡体的稳定系数急剧下降,滑坡前缘局部发生滑动,为滑坡创造了临空面,进而引发自下而上的牵引式滑动;抢险状态下,滑坡上部和整体仍存在滑动风险,实施综合治理措施是必要的;治理状态下,滑坡稳定系数最大增幅为0.28,其中排水措施使滑坡稳定系数增加0.16,治理效果极为明显,同时支护加固对浅层滑动的控制具有良好效果。目前滑坡的稳定系数均大于允许值值,且变形和支护应力监测结果均趋于收敛,滑坡现状稳定。研究成果对江坪河水电站的长期安全运行具有重要指导意义,对类似降雨型堆积体滑坡的安全评价和综合治理也具有重要参考价值。更多还原

【Abstract】 The topography of China is complex and diverse,and the monsoon climate is significant.Under the influence of rainstorm and human engineering activities,landslide disasters are characterized by wide distribution,high frequency and great harm.The research on seepage dynamic behavior and its influence on stability of landslides under rainfall conditions has important theoretical significance and application value for landslide disaster prevention and control.This thesis takes Meijiatai landslide control project as the research object,aiming at long-term stability of landslide area.The evolution pattern of landslide seepage field has been studied by the methods of field monitoring,numerical simulation and inversion analysis.The influence of engineering treatment measures such as excavation,reinforcement and drainage on landslide stability has been revealed,and the stability of landslide treatment project has been evaluated systematically.The main achievements are listed as follows:(1)The material composition of landslide and the occurrence characteristics of groundwater have been identified,and the formation mechanism of landslide has been revealedThrough the analysis of engineering hydrogeological conditions,the material composition of landslide and occurrence characteristics of groundwater have been revealed.The landslide process during the rainstrom in 2007 has been analyzed to explore the type and cause mechanism of the landslide.The research shows that the landslide is divided from top to bottom into colluvial soil,relatively intact rock body,old slide layer and bedrock layer.The old slide layer has relatively water-resistant characteristic,so there are three types of groundwater in landslide under the recharge of rear margin karst groundwater and surface rainfall infiltration:pore phreatic water,fissure phreatic water and fissure confined water.The landslide is a typical rainfall accumulation landslide.The accumulation of slope deposits caused by the collapse of the rear margin provides material conditions for landslide,meanwhile,the boundary of rock and soil layer provides a sliding mirror for landslide.During rainstorm,rainfall infiltration and groundwater level rise induce traction failure along the interface between residual slope and relatively intact rock mass.(2)The numerical simulation and inversion analysis of landslide seepage field have been carried out,and the dynamic evolution pattern of landslide seepage field in Meijiatai has been revealedCombined with the long-term seepage monitoring data,the water level at the rear margin and the seepage parameters of different layers have been analyzed dynamically by inverse modeling.Subsequently,the dynamic evolution characteristics of saturated-unsaturated seepage fields in natural,emergency and treatment states have been analyzed,at the same time,the rainfall infiltration recharge coefficient of the landslide has been calibrated.Building on this foundation,three-dimensional unsteady seepage process considering rainfall infiltration has been analyzed,and the treatment effect of drainage measures has been comprehensively evaluated.The research indicates that the calculated result of the seepage field is in good agreement with the measured values of the pore pressure measurement points.The results of the dynamic inversion analysis of the rear margin water level are reliable,and the seepage parameters of rock and soil mass are reasonable.Under the recharge of rainfall infiltration and dynamic water level at the rear margin,the groundwater level rises significantly in wet season and there is seepage phenomenon at the foot of slope.Meanwhile,a large range of saturated areas appear in the central weak accumulation zone and the lower slope foot during the rainstorm.With the gradual implementation of drainage measures,the groundwater level decreased by 9.2 to 16.5 m,maintaining a relatively low level,meanwhile,the discharge of drainage holes can respond rapidly during the rainy season.At the same time,drainage measures can inhibit the development of saturated areas during rainstorm.The analysis indicates that the drainage measures are appropriately implemented,thereby effectively controlling the groundwater level and seepage field within the slope.(3)The change rule of landslide stability since the occurrence of landslide has been revealed,and the comprehensive treatment effect of Meijiatai landslide has been evaluated quantitativelyBased on the results of seepage fields,the limit equilibrium method and the strength reduction method have been used to analyze the stability evolution of natural state,emergency state and treatment state,and the effects of excavation,support reinforcement and drainage pressure reduction on the stability have been quantitatively analyzed.Subsequently,combined with the relevant monitoring data,the landslide stability state has been evaluated comprehensively.The research indicates that under the natural state,rainstorm causes sharp decrease in the stability coefficient.The local slide of the landslide front creates a free surface for the landslide,which leads to the bottom-up traction slide.Under the emergency state,there is still the risk of upper and whole sliding of landslide,and comprehensive treatment should be carried out.Under the treatment state,the maximum increase in the stability coefficient of the landslide is 0.28,with the drainage measures contributing to an increase of0.16.The effect of drainage measures is very obvious,and the support reinforcement effectively controls the shallow sliding.At present,both the monitoring of landslide deformation and support stress tend to converge,and the stability coefficients are greater than the allowable values.Therefore,the landslide is in a stable state.The research findings have significant guiding implications for the long-term safe operation of the Jiangping River Hydropower Station and also provide valuable references for the safety assessment and comprehensive management of similar rainfall-induced accumulated mass landslides.更多还原