间歇型降雨对堆积层斜坡变形破坏的物理模拟研究

为研究间歇型降雨作用下缓倾堆积层斜坡的变形破坏特征,以樱桃沟滑坡为例,进行了降雨作用下斜坡变形破坏的物理模拟研究。试验结果表明：前期降雨作用下坡体变形特征表现为前缘滑移沉陷、中部滑移、后缘沉陷、坡体裂缝生成,且前缘裂缝扩张明显,后期降雨作用下坡脚区域首先发生滑塌,然后依次向后缘传递发生逐阶滑塌破坏;降雨入渗易在基岩面上储存,形成暂态地下水位、高孔隙水压力区域和坡向渗流场,基岩面附近土体饱水时间长,软化程度高,抗剪强度弱化显著,边坡易沿基覆界面土层发生滑坡;坡体滑动易发生在降雨间歇期,触发特征表现为雨后坡体暂态饱和区水分和坡表积水持续下渗,导致地下水位上升滞后于降雨,造成坡体内浮托力、渗透力和孔隙水压力增大,有效应力降低,诱发滑坡。     

强降雨条件下碎屑岩滑坡远程运动模拟分析——以牛儿湾滑坡为例

中国西南砂泥岩地层山区在强降雨条件下频发远程滑坡灾害,是防灾减灾领域亟待解决的关键问题。以2020年7月13日重庆武隆牛儿湾滑坡为例,通过无人机航飞、野外调查和地质条件分析等手段,运用PFC^3D模拟,对中国西南砂泥岩地层山区强降雨条件下流化滑坡远程运动成灾模式开展研究。研究结果显示：独特的地层结构(上部为第四系残坡积土,下部为砂泥岩)是导致滑坡顺层失稳,并远程流化运动的根本原因;强降雨条件是导致滑坡深层失稳、整体下滑,同时使表层残破积土层饱水流化远程运动的关键影响因素;顺层滑坡远程流化成灾模式主要表现出下层整体滑移、中层粗细颗粒混合和上层饱水流化的特征,流化过程可分为整体高位失稳—混合加速—运动流化堆积三个阶段。基于以上研究,认为砂泥岩地层山区的远程流化滑坡风险调查与预测过程应当充分基于滑体远程流化运动的成灾特点进行调查与评价,以此为防灾减灾提供定量化科学依据。     

Formation and characteristics of the Xiaoba landslide in Fuquan,Guizhou, China

On August 27, 2014, a large-scale landslide occurred in Fuquan, Guizhou, China. This high-speed landslide caused considerable destruction; 23 people were killed, 22 were injured, and 77 houses were damaged. Field investigations, deformation monitoring, and numerical analyses have been performed to examine the characteristics and formation processes of this landslide. In the Xiaoba area, the slope showed a two-layered structure with a hard upper layer and a soft lower layer. Dolomite of the Dengying Formation in the slope front formed a locked segment controlling slope stability. Based on deformation and failure characteristics, the landslide is divided into sliding source area A and accumulation area B. The landslide is also divided into the following stages: bedding slip, tension cracking at the slope scarp, and the appearance of the locked section at the slope toe. Numerical calculations show that excavation led to maximum shear strain concentration along the interface of siltstone and slate in the middle of the slope, which became a potential sliding surface. Stress concentration and distribution of the plastic zone of the locked segment of the Dengying Formation dolomite occurred in the slope toe. Continuous rainfall caused the groundwater level to rise in the Xiaoba slope. The unfavorable geological structure was a determinant factor, and the combined effects of excavation and continuous rainfall were triggering factors that induced the landslide. The geomechanical mode for the Xiaoba landslide is sliding tension–shear failure.     

Mechanism and failure process of Qianjiangping landslide in the Three Gorges Reservoir,China

The Qianjiangping landslide is a large planar rock slide which occurred in July 14, 2003 shortly after the water level reached 135 m in the Three Gorges Reservoir, China. The landslide destroyed 4 factories and 129 houses, took 24 lives, and made 1,200 people homeless. Field investigation shows that the contributing factors for the landslide are the geological structure of the slope, the previous surface of rupture, the water level rise, and continuous rainfall. In order to reveal the mechanism and failure process of the landslide, numerical simulation was conducted on Qianjiangping slope before sliding. Based on the characteristics and the engineering conditions of the landslide, the topography and the geological profiles of Qianjiangping slope before sliding is reconstructed. The seepage field of Qianjiangping slope before sliding was simulated with the Geostudio software. The results show that ground water table rises and bends to the slope during the rise of water level, and the slope surface becomes partially saturated within the period of continuous rainfall. Using the ground water table obtained above, the failure process of Qianjiangping slope is simulated with the Flac3D software. The results demonstrate that the shear strain increment, displacement, and shear failure area of the slope increased greatly after the water level rose and continuous rained, and the landslide was triggered by the combined effect both of water level rise and continuous rainfall. The development of shear strain increment, displacement, and shear failure area of the slope shows that the landslide was retrogressive in the lower part of the slope and progressive in the upper part of the slope.     

陕西华县高楼村黄土滑坡泥流的成因分析

滑坡泥流具有高速远程运动的特点,一般先形成滑坡,随即转为高速泥流,虽不多见,但破坏性大。陕西华县高楼村黄土滑坡泥流是一个由于引水渠漏水引起的典型案例。对滑坡形成区后壁黄土的物理性质测试表明,可转化为泥流的滑坡具有疏松的结构,一般饱和含水率大于液限。对其在饱和状态的三轴固结不排水试验表明,试样在很小应变下发生剪缩,产生较高的超孔隙水压力,超孔隙水压力达到一定程度,使其由固态转化为流态,从而形成快速、远距离的流动。当边坡被引水渠渗漏的水浸湿,潜在滑带几乎处于饱和时,在静水压力作用下,其稳定性接近临界状态; 一旦开始破坏,剪力作用下疏松的结构发生剪缩,沿滑动带产生较高的超静孔隙水压力,导致滑带呈流态高速下滑,此时的滑带只有很低的强度,因此沿着坡度较陡的沟底保持高速流动,到沟口平坦处势能完全释放后才停滞。用Sassa K.滑坡运动模型,对该滑坡的运动过程模拟,模拟结果与现场实测滑坡发生后的地形较为一致。     

一种考虑曲面地形效应的流动性滑坡运动模型

流动性滑坡在流经曲面地形时会产生附加的离（向）心作用,而以往的研究并未充分考虑这种作用。本文以LS_RAPID模型为基础,补充了在曲面地形下滑体运动所受离（向）心力,修正LS_RAPID模型的控制方程,得到考虑曲面地形效应的流动性滑坡运动模型——LSD_T（Landslide Dynamic_Terrain）模型。运用该模型对一典型流动性滑坡——天水市大沟滑坡进行模拟,并与相同参数下LS_RAPID模型的模拟结果进行对比。结果表明:LS_RAPID模型中曲面地形对滑体运动的限制作用不明显,体现为弯道处滑体冲出沟道,不符合滑坡的实际运动情况;而LSD_T模型则能够较好的反映弯道离（向）心作用的影响,滑体在弯道处顺沟滑动,运动轨迹与实际堆积过程基本一致。     

南京市浦口区某山前缓坡滑坡复活机制再分析

南京猪头山滑坡属于典型的覆盖层滑坡,2003年5月边坡发生缓慢变形失稳,没有对周围造成很大的危害,故未引起足够重视,2016年6~7月间受强降雨的影响再次发生大规模的滑动。研究发现,该滑体的地层具有特殊地质结构,在强降雨条件下会产生暂时性承压水,在其承压水的渗透力及浮托力作用下,其稳定性将会大大下降,因此该滑坡的再滑动与降雨密切相关。本文运用数值模拟方法分析了滑坡变形过程与降雨时长及降雨强度之间的关系,结果表明猪头山山前缓坡的稳定性随降雨时长和降雨强度增大逐渐降低,且具有一定的突变性,其滑坡面的位置位于坡体填土层的下部,较好地揭示了猪头山降雨型滑坡形成的机理以及滑坡再滑动机制。这一研究为所在地区的降雨性滑坡预报和治理提供了科学依据。     

Study on the Instability Mechanisms and Monitoring Control of Stratified Rock Slope with Water-Rich Strata

Water is one of the leading factors in the sliding geological disasters of rock slope, and the harm of fissure water to slope rock mass more and more becomes one of the hotspot research problems in transportation infrastructure construction in mountainous area. Based on the current research status quo of effect of fissure water on rock mass, the interaction mechanisms of water and rock in stratified rock slope were analyzed by related theories such as rock mass mechanics, fluid mechanics and soil mechanics including softening dissolution, scour hole enlargement and padding effective stress, and the influence of water–rock interaction on slope sliding disasters. Then, the influence of rainfall on the displacement field distribution of slope was analyzed during one year of monitoring a typical,natural slope in the Sichuan–Chongqing region. Observations include surface displacement, deep displacement, water level and rainfall. Finally, a targeted reinforced disposal scheme was proposed that considered the rainfall effect. The results provide reference for the instability theory and treatment measures for a high-risk stratified slope.     

Consistent modeling of a catastrophic flowslide at the Shenzhen landfill using a hydro-elasto-plastic model with solid–fluid transition

Flow-type landslides are an important hazard that can cause great destruction due to the rapid flow velocity and large disaster area. This paper presents a catastrophic flowslide that recently occurred at a landfill in Shenzhen, China. This disaster involved an area about 1100 m in length and 630 m in maximum width, and caused the death of 77 people and the destruction of 33 buildings. The precise reason for the landfill’s failure is still unknown, and therefore we try to contribute an increased understanding of the event for future prevention. In this study, the failure mechanism of the studied slope was analyzed and described under partially saturated condition. The solid–fluid transition during the flowslide occurrence was described using a unified constitutive model. The model was used to perform the hydro-elasto-plastic modeling in the pre-failure stage, the viscous modeling in the post-failure stage, and the second-order work criterion was introduced in between to model the solid–fluid transition. The consistent evolution of the flowslide, including initiation, propagation, and deposit stages, was simulated and analyzed using the finite element method with Lagrangian integration points after careful calibration of the viscous parameters. The numerical results were compared with the real case and used to explain the failure mechanism.     

基于模拟试验的强降雨条件下花岗岩残积土斜坡滑塌破坏机理分析

以东南沿海地区花岗岩残积土为代表性土样,以土体斜坡坡度、降雨强度为控制变量,设计了降雨滑坡模拟试验方案,在大雨、暴雨、大暴雨、特大暴雨等四种不同降雨等级条件下对四种不同坡度的斜坡模型进行了强降雨模拟试验,研究降雨强度和斜坡坡度对其滑塌破坏的影响特征。结果表明:降雨强度越大,发生深层破坏或浅层整体破坏的趋势越明显,其变形跨塌滑块尺寸越大,破坏范围越集中,破坏程度增强;同时土体裂纹出现的时间越早,斜坡滑塌破坏所需的降雨时长逐渐减少。随斜坡坡度的增大,破坏形式由滑落滑坡逐步转化散落崩塌破坏,其相应斜坡滑塌破坏所需的降雨时长减少。研究结论对揭示降雨引发残积土滑坡等地质灾害发生规律具有重要的理论和现实意义。     

渗透性与降雨强度对堆积层滑坡稳定性的影响

本文基于非饱和渗流理论及非饱和土的Fredlund双应力变量强度理论,对一沿岩土接触面滑动的堆积层滑坡模型,分别进行了8种条件下的降雨入渗数值模拟试验,研究了不同土体渗透性及降雨强度对滑坡稳定性的影响。结果表明:(1)堆积层滑坡的稳定性与土体的渗透性有密切关系,在降雨后的短期内,土体渗透性越好,滑面孔隙水压力升高越明显,滑坡的稳定性降低程度越大;(2)降雨期间,埋深较浅的滑面,入渗雨水能够较快到达,对滑坡稳定性的影响较大;(3)在相同的降雨时间内,降雨强度越大,滑坡稳定性降低速率越快;(4)降雨强度影响着滑坡发生的滞后性,在降雨总量一定的条件下,若降雨强度较大,雨停后,滑坡稳定性继续下降的程度较大;(5)降雨总量控制着滑坡的最终稳定性。     

震后坡面松散堆积体失稳水力学机理研究

为研究震后强降雨条件下沟道泥石流产生的力学机制及水力学机理,以都江堰市龙池镇银洞子泥石流沟为研究对象,构建坡面松散堆积体地下水位变化水力模型,按照水力学渗流理论,分析了震后泥石流形成区坡面松散堆积体内潜水位变化的特征和规律,定量研究了动静水压力对坡体的作用特点。根据理论分析、实例验证与物理模拟试验的研究结果,获得了对坡面松散物源启动力学机理、启动临界条件及启动模式的深刻认识：(1)在强降雨激发作用下,随着坡体内潜水位不断升高,水力条件不断恶化,最终导致坡面松散堆积体发生失稳破坏;(2)堆积体内潜水位高度是坡面面积(S)、稳态降雨强度(I),坡体几何参数、导水系数(T_D)等参数的综合函数,S、I越大,则潜水层厚度(H)越大,反之,当坡面集雨面积和稳态激发降雨强度一定时,导水系数、坡体宽度和潜水面倾角越大,则坡体内产生潜水层垂直厚度越低;(3)随着坡体内静水压力(P)增加,堆积体基底抗滑力将会降低;随着坡体内动水压力(G_d)增加,坡体下滑力将会增加;(4)根据剩余下滑力的存在形式,震后坡面松散堆积体的启动模式可分为2种,即坡体整体启动的推移式失稳...     

开挖与降雨作用下边坡失稳机理及模拟分析

边坡开挖和降雨通常是导致边坡失稳的重要原因。本文以湖南湘西山区某国道扩建开挖边坡为研究对象,基于现场边坡监测结果和数值模拟分析,研究了在边坡开挖和降雨条件下坡体变形位移的过程。结果表明:边坡的破坏是一个渐变的过程,不同的影响因素对边坡的影响不同。开挖切方是浅层坡体失稳的诱发因素,开挖切方破坏了坡体的应力平衡,使坡体的应力重新分布,并在坡体中产生浅层的滑动面。雨水的入渗是坡体深层滑动面的诱发因素,雨水沿着裂缝渗入坡体,使浅部滑动面上下土体的变形差进一步加大,进而产生浅层牵引式滑动破坏。同时雨水的入渗使碎石土和强风化页岩交界附近产生高孔隙水压力,在水-岩土共同作用逐渐形成软化的滑带土,从而形成深层滑动面。     

西南某机场高填方边坡滑塌机制分析与处理措施研究

西南某高填方机场土石方工程竣工后不久遭遇了持续半月的强降水,在一次突发暴雨后4h,边坡发生了滑塌。采用监测、检测、现场调查、原位试验、室内试验、数值模拟等手段进行综合分析。结果认为,该机场高填方边坡滑塌主要是采用含碎石黏性土填筑的土面区、边坡影响区,因强夯补强破坏了填筑体内原有的碎石排水层,造成了采用碎石填筑的道槽区入渗的降水不能及时排出而引发的高地下水压力、渗透变形、浸泡软化等共同作用所致。最后针对性地采取填筑体顶面薄膜覆盖,坡面出水点网装级配碎石反滤和引流、滑塌坡面袋装碎石回填的应急处理措施,以及填筑体顶面黏性土回填、坡面碎石换填、仰斜管排水的永久处理方法,有效地控制了边坡的进一步变形、滑塌,取得了良好的灾害治理效果。     

滑坡降雨阈值模型的应用

在数字高程模型（DEM）的基础上,运用滑坡降雨阈值模型,以楚雄丁家坟一斜坡作为试验研究工点,结合现场勘察、监测数据以及斜坡岩土体主要特性、地形地貌、降雨强度与降雨持续时间、地下水位等因素,模拟斜坡单元产生潜在滑动时的临界降雨量,研究降雨对滑坡发生、分布的影响。研究结果表明：各斜坡单元产生潜在滑动时的临界降雨量各不相同,在不同的降雨量及地下水位条件下滑坡降雨阈值模型模拟的潜在滑坡位置主要位于楚勐公路下边坡处,与实际发生滑坡的位置吻合率达80%以上,滑坡降雨阈值模型可实现对斜坡稳定性进行可视化分析与预测,为降雨型滑坡提供一种有效的预测与分析方法。     

浅层地震勘探在滑坡勘查中应用

下 垢 坪 斜 坡 是 长 江 三 峡 库 区 内 正 在 变 形 的 斜 坡 之 一 ,本 区 雨 量 充 沛 ,降 雨 相 对 比 较 集 中 ,结 构 特 征 属 于 碎屑 岩 层 状 结 构 斜 坡 和 松 散 堆 积 斜 坡 ,如 斜 坡 存 在 滑 动 面 ,其 滑 坡 隐 患 将 危 及 长 江 航 道 。 为 此 利 用 瞬 态 瑞 雷 波 法 、地震 反 射 波 法 、地 震 折 射 波 法 等 浅 层 地 震 勘 探 方 法 ,结 合 电 法 、钻 探 资 料 ,对 三 峡 库 区 下 垢 坪 变 形 坡 体 的 稳 定 性 进 行了 评 价 。 结 果 表 明 斜 坡 为 多 级 阶 地 特 征 ,在 没 有 外 界 动 力 的 作 用 下 ,斜 坡 坡 体 重 力 作 用 不 足 以 使 斜 坡 产 生 滑 动 。     

Characteristics,mechanisms, and post-disaster lessons of the delayed semi-diagenetic landslide in Hanyuan,Sichuan, China

Landslides following rainfall occurrence are a widespread phenomenon. The neglect of this phenomenon leads to serious loss of life when disasters occur. At 03:45 (GMT?+?8) on August 21, 2020, a semi-diagenetic landslide occurred in Zhonghai Village, Hanyuan County, China, which occurred 42 h after earlier rainfall. Nine people privately returned to their homes after evacuation of the dangerous area. In this disaster, eight people were lost and one injured. This study explores the failure characteristics, inducement, and mechanisms of the landslide via field investigations, resident interviews, multi-temporal images, field drilling, and geotechnical tests. Hydrological numerical calculations were also performed to uncover the seepage and transfer processes of the groundwater in the slope. Finally, problems in the current community early warning system were analyzed and corresponding suggestions put forward. The results show that the maximum sliding depth of the landslide was 27.5 m, the total area was 80,000 m², and the sliding volume was about 58,0000 m³, making it a medium-sized deep landslide. In addition to the vertical seepage of rainfall in the landslide area, the downward movement of rainfall in the back and upper catchment areas along the silt sand strata also affected the stability of the landslide. More needs to be done to make the population aware of this lag phenomenon to achieve scientific disaster reduction. This study not only provides a case study of a lagging semi-diagenetic landslide, but also provides insight into hydrological boundary determination and landslide early warning system construction.

     

降雨对花岗岩风化层路堑边坡滑动模式影响

降雨引起路堑边坡的浅层局部滑动是工程中常见的现象,但其内在原因的研究尚不充分。为此,以福建省云平高速云霄段花岗岩风化层中的某两级路堑边坡为例,采用饱和和非饱和土抗剪强度理论,按照强度折减有限元方法分析了该边坡在一般工况、地下水渗流工况和降雨入渗工况下的滑动模式。结果表明:一般工况下该边坡滑动模式为深层整体滑动;地下水渗流作用可使边坡由深层滑动模式向浅层滑动模式转化;长时小或中等降雨作用下坡体内出现三道滑动面,且一级边坡内滑动面最先贯通,滑坡模式由深层整体滑动向浅层局部滑动演化。短时强降雨作用下仅在一级边坡内出现贯通的滑动面,即由整体滑动模式完全转变为浅层局部滑动模式。降雨工况越不利表现越为明显,与实际滑坡现象相吻合,且安全系数不满足规范要求,从而从理论上验证了该路堑边坡发生浅层局部滑动的必然性。此外,为避免花岗岩风化层路堑边坡在降雨入渗下发生浅层局部滑动,对假设的不同放坡方案进行了数值模拟分析。结果表明,适当放缓坡率可使一级边坡内不出现滑动面,滑坡模式仍为较深位置的整体滑动,且安全系数可得到有效提高,使其满足规范要求。因此,实践中,采用文中方法对设计的类似地层中的路堑边坡事先进行降雨入渗影响下的模拟分析极为必要。将使放坡坡率更为科学合理,可在确保边坡整体稳定性的同时,极大降低其发生浅层局部滑动的可能性。     

基于诱发机理的降雨型滑坡预警研究——以花岗岩风化壳二元结构斜坡为例

降雨型滑坡是我国主要的滑坡灾害类型,具有区域群集发生的特点,滑坡预警研究是防灾减灾的重要途径。传统的区域降雨型滑坡预报模型多采用统计结果建立降雨参数模型,对降雨诱发机理和斜坡失稳的力学机制考虑不足,预报可靠性和精度有限。本文以花岗岩风化壳地区某典型二元结构斜坡为原型,以实际勘查数据为基础,提取该斜坡结构特征,基于饱和-非饱和渗流理论,分析研究降雨入渗过程和斜坡失稳机制,建立典型斜坡的预警判据。1花岗岩风化壳地区典型二元结构斜坡为类土质斜坡,覆盖土层较厚,剖面上可分为两层,上层为坡积黏性土,土质松散,透水性强,下层为残积黏性土,土质相对致密,透水性较差。2采用不同降雨工况模拟分析降雨入渗过程。以50mm·d-1雨强为例,降雨持时30h以内时,降雨入渗主要集中在上层的坡积黏性土,斜坡前缘优先饱和,滑带开始出现积水现象;降雨持时40～50h时,斜坡表面降水持续入渗,在坡体后缘拉裂缝处,雨水沿着裂缝快速入渗坡体形成静水压力,增加坡体重量,增大下滑力,坡脚渗透路径短,最先饱和破坏,造成斜坡失稳。3监测斜坡不同部位（坡脚、中部、后缘）的孔隙水压力情况,随降雨入渗,斜坡土体孔隙水压力持续增大,由负趋近于零到大于零,斜坡土体由非饱和状态向饱和状态过渡,坡脚最先饱和,中部持续入渗,后缘土体饱和后,裂缝扩大致使大量雨水进入,使本已大量积水的滑带变形错动,斜坡失稳。4模拟分析得到斜坡失稳的不同降雨条件:中雨雨强（10mm·d-1）,历时约13d;大雨雨强（25mm·d-1）,历时约5d;暴雨雨强（50mm·d-1）,历时约2.2d;特大暴雨雨强（100mm·d-1）,历时约1.1d。在暴雨雨强时,降雨对该类斜坡的滞后作用约为5h。最后,建立了该类斜坡的临界降雨判据（I-D曲线）。     

降雨入渗条件下软岩边坡稳定性分析

降雨条件下软岩边坡的失稳模式是进行边坡处治的基本依据之一。为研究软岩边坡在降雨条件下的稳定性,提出了一种既能考虑渗流场对边坡稳定性的影响,又能体现岩石软化效应对边坡失稳所带来的不利作用的新方法。运用二维渗流数值计算方法,对降雨条件下的边坡孔隙水压力大小及暂态饱和区面积在空间及时间上的分布进行了模拟。并将渗流场计算结果与暂态饱和区岩石软化试验所得岩石物理力学参数随时间的取值相结合,采用强度折减法分析软岩边坡在降雨入渗条件下的稳定性。对算例边坡的研究表明：降雨入渗条件下软岩边坡的失稳在降雨初期表现为边坡表层局部分层垮塌。随着降雨历时的增长,失稳形式则表现为局部分层垮塌与整体滑移相结合。降雨停止后,边坡负孔隙水压力的消散,对软岩边坡安全系数的继续降低具有一定的延缓作用。