ISSN 1003-8035 CN 11-2852/P

    西藏山南鲁麦古滑坡发育特征与复活变形机制研究

    马海善, 吴瑞安, 赵文博, 王计博, 齐畅, 邓盼, 李英钧

    马海善,吴瑞安,赵文博,等. 西藏山南鲁麦古滑坡发育特征与复活变形机制研究[J]. 中国地质灾害与防治学报,2024,35(5): 32-41. DOI: 10.16031/j.cnki.issn.1003-8035.202403013
    引用本文: 马海善,吴瑞安,赵文博,等. 西藏山南鲁麦古滑坡发育特征与复活变形机制研究[J]. 中国地质灾害与防治学报,2024,35(5): 32-41. DOI: 10.16031/j.cnki.issn.1003-8035.202403013
    MA Haishan,WU Ruian,ZHAO Wenbo,et al. Development characteristics and reactivation deformation mechanism of the Lumai landslide in Shannan City, Xizang[J]. The Chinese Journal of Geological Hazard and Control,2024,35(5): 32-41. DOI: 10.16031/j.cnki.issn.1003-8035.202403013
    Citation: MA Haishan,WU Ruian,ZHAO Wenbo,et al. Development characteristics and reactivation deformation mechanism of the Lumai landslide in Shannan City, Xizang[J]. The Chinese Journal of Geological Hazard and Control,2024,35(5): 32-41. DOI: 10.16031/j.cnki.issn.1003-8035.202403013

    西藏山南鲁麦古滑坡发育特征与复活变形机制研究

    基金项目: 国家自然科学基金项目(42207233);青海省科技计划基础研究项目(2019-ZJ-7063)
    详细信息
      作者简介:

      马海善(1988—),男,岩土工程专业,大学本科,工程师,主要从事水工环地质调查研究。E-mail:1060956420@qq.com

      通讯作者:

      吴瑞安(1991—),男,地质工程专业,博士,副研究员,主要从事工程地质与地质灾害研究。E-mail:wuruian1991@126.com

    • 中图分类号: P642.22

    Development characteristics and reactivation deformation mechanism of the Lumai landslide in Shannan City, Xizang

    • 摘要:

      青藏高原地质条件复杂,历史上形成了大量古滑坡,近年来在极端天气和人类工程活动影响下,古滑坡复活变形呈加剧趋势,潜在危害严重。文章以西藏山南鲁麦古滑坡作为研究对象,利用野外地质调查、无人机测绘、数值模拟等技术方法,在剖析其变形特征的基础上,分析了古滑坡复活的影响因素,探究了地表水入渗与堆载作用下古滑坡复活失稳机制。研究结果表明:鲁麦古滑坡体积为2.5×106~15.1×106 m3,前缘剪出口与坡脚的当许雄曲最大高差超过200 m,最深层的滑带位于基岩与堆积体间的接触面;受地表水入渗与堆载作用影响,古滑坡复活变形目前集中分布在堆积区前部,地表发育大量地表裂缝和下错陡坎;在地表水集中入渗影响下,滑坡前缘表层岩土体多次发生局部滑动;前缘堆载增加后,滑坡前部的形变整体增加,并呈高位剪出的趋势。研究成果对深化西藏山南地区古滑坡复活机理和支撑当地防灾减灾工作具有一定意义。

      Abstract:

      The complex geological conditions of the Tibetan Plateau have historically fostered the development of numerous ancient landslides. In recent years, the reactivation of these landslides has exhibited a concerning escalation, driven by extreme weather events and human activities, thereby posing significant hazards. This study examines the Lumai ancient landslide in Shannan City, Xizang, employing a combination of field geological investigation, drone mapping, numerical simulation, and other technical methodologies. The research focuses on analysing the reactivation characteristics and influencing factors, specifically investigating the reactivation mechanism of the ancient landslide under the effects of surface water infiltration and loading. The results indicate that the Lumai ancient landslide has a volume of 2.5×106 to 15.1×106 m3. The maximum height difference between the landslide’s leading edge shear outlet and the Dangxuxiongqu River at the slope foot exceeds 200 meters, with the deepest sliding zone located at the interface between bedrock and loose deposits. Deformation is primarily concentrated in the front part of the landslide’s accumulation zone, characterized by numerous cracks and steep scarps. The reactivation is significantly influenced by surface water infiltration and overloading. Under concentrated water infiltration, localized sliding frequently occurs at the landslide front. Additionally, increased loading at the front leads to overall deformation and a tendency toward high-position shear failure. These findings enhance the understanding of reactivation mechanisms for ancient landslides in the Shannan City, Xizang, and provide valuable insights for local disaster prevention and mitigation efforts.

    • 顺倾岩质边坡是指坡面与岩层走向和倾角相同的边坡,主要发育在开挖后的背斜和向斜两翼[12]。边坡岩质边坡是岩质边坡的主要破坏形式,是中国最大的边坡类型。最常见的滑坡是以软弱夹层为控制性滑面[3]。由于构造面薄弱,沿地层的岩质边坡易形成大面积滑坡,不稳定,影响因素复杂,难以预测[46]。顺倾岩质边坡成为边坡工程中的重难点[7]

      许多学者对顺倾软弱夹层边坡滑动规律问题进行研究。冯君等[8]建立了层状岩质边坡岩土试验模型,获得了层状岩质边坡施工和开挖过程中岩体破坏的规律和特征。陈从新等[9]人采用地质模型试验的方法分析了层状岩质边坡的失稳变形机制和边坡在岩石倾角作用下的稳定性,认为层状岩质边坡的破坏模式主要为滑动破坏。Michael[10]对沉积岩层中顺层平行剪切带的研究表明,平行海岸线带的形成是由于因为软弱层膨胀性、软岩蠕变、滑面带渐进式破坏等因素。舒继森等[11]分析了层状岩质边坡的静水压力,推导出了结构面上的动水压力,研究发现,静水压力对层状边坡稳定性的影响大于动水压力。魏刚等[12]分析的康杨滑坡得出黄河侧蚀作用和降水入渗形成软弱滑动带可能 是诱发康杨滑坡发生的主要因素。Hoke等[13]定义了层状岩质边坡的水力分布和水力作用,提出与干边坡相比,饱和水边坡的稳定性更低。赵磊等[14]持续监测滑坡湿度、土壤含水量、地下水位等,总结出降雨入渗率经验公式。聂永鹏等[15]采用FLAC3D数值模拟方法,分析了在建筑物附加荷载下老滑坡以及地基土体的应力应变发展规律,揭示了建筑加载下老滑坡稳定性的变化趋势和建筑物变形破坏机理。田辽西等[16]分析出静水压力的变化降低了岩土体的抗剪切能力、从而导致边坡岩体失稳。

      在当前研究中,许多学者从边坡稳定性影响因素和破坏模式上对顺倾岩质边坡滑坡进行了详细研究,研究对象主要为单弱层或等厚顺倾岩质边坡。顺倾岩质边坡是以稳定性的变化为主线不断发展演化的,软弱夹层是顺倾岩质边坡稳定性的控制因素,对比含多软弱层的边坡与单弱层边坡,坡内的力学环境不同,由此其滑动演化机制也存在差异,与此同时,对顺倾软弱夹层边坡地下水及降雨入渗作用下的滑动演化机制的研究较少。论文基于抚顺西露天矿南帮滑坡工程实例,分析了地下水及降雨入渗作用下顺倾软弱夹层边坡失稳的水力学模式,采用FLAC3D软件对抚顺西露天矿南帮边坡在地下水及降雨入渗影响下,边坡变形破坏失稳动态的演化过程进行了模拟分析,找出边坡的位移场和破坏运动特征,对比体积应变增量及$x$向有效应力动态变化,分析边坡孔隙水压力的阶段积累特征,进而得到地下水及降雨入渗作用下顺倾含软弱夹层岩质边坡的滑动演化机制,为抚顺西露天矿南帮的灾害预防与治理提供参考。

      抚顺西露天矿南帮滑坡为岩质滑坡,总体坡度19°~27°,整体呈顺倾边坡。南帮边坡上部主要为出露的玄武岩,下部为凝灰岩,在坡脚堆积有矿区回填土等。在南帮滑坡后缘出现的地裂缝(图1)处,出露有花岗片麻岩、古风化壳、玄武岩夹煤线、凝灰岩等软弱破碎带等。边坡地表为杂填土层,有1~50 m厚的人工堆积矸石,上部堆积岩土以为煤矸石、风化的玄武岩、页岩碎石等为主,厚度在1~50 m;滑坡底部基岩为质地坚硬的花岗片麻岩。通过矿区钻孔资料了解南帮边坡有两层主要滑面:上层滑动面位于玄武岩夹煤线、玄武岩夹凝灰岩层中;下层滑动面位于玄武岩与花岗片麻岩之间的古风化壳中。两层滑面在坡体下部剪出,滑面后缘在坡体顶部以地裂缝形式显露,滑面倾向北,前缘在坑底及坡脚以地面鼓胀和坡脚剪出形式显露。南帮工程地质剖面如图2所示。

      图  1  抚顺西露天矿南帮坡顶地裂缝
      Figure  1.  Site photo of ground cracks on the southern slope top of Fushun west open pit mine
      图  2  抚顺西露天矿南帮工程地质剖面图
      Figure  2.  Geological cross-section of the southern slope of Fushun west open pit mine

      通过对抚顺西露矿区水文地质资料的收集发现,抚顺地区雨量充沛,主要为海洋性气候,降水大部分在夏季7—8月份以暴雨形式出现,最大日降雨量为185.9 mm。南帮边坡内地下水埋藏较深,基岩裂隙水赋存于因风化形成的基岩裂隙中,含水岩层以玄武岩和凝灰岩为主。

      自然状态下,饱和及非饱和状态常同时存在于坡内,降雨入渗过程就是非饱和—饱和的转化过程[17]

      饱和土的抗剪强度通过Mohr-Coulomb破坏准则[18]和Terzaghi有效应力原理[19],可得:

      $$ \tau = c' + \left( {\sigma - {\mu _{\rm{w}} }} \right)\tan \varphi ' $$ (1)

      式中:$ \tau $——破坏时破坏面上的剪应力/Pa;

      $ c' $——有效黏聚力/Pa;

      $\sigma $——破坏面上有效应力/Pa;

      $ {\mu _{\rm{w}} } $——孔隙水压力/Pa;

      $ \varphi ' $——有效内摩擦角/(°)。

      而非饱和土的抗剪强度为:

      $$ \tau = c' + \left( {\sigma - {\mu _{\rm{a}} }} \right)\tan \varphi ' + \left( {{\mu _{\rm{a}} } - {\mu _{\rm{w}} }} \right)\tan {\varphi ^{\rm{b}}} $$ (2)

      其中:$ {\mu _{\rm{a}} } $——孔隙中的气压/Pa;

      $\mu _\alpha - {\mu _\omega }$——破坏时破坏面上的基质吸力,当气压为 0时,吸力为负的孔隙水压力/Pa;

      ${\varphi ^{\rm{b}}}$——抗剪强度随基质吸力而增加的速率/(m·s−1)。

      二维饱和—非饱和的渗流控制方程可根据达西定律得:

      $$ \frac{\partial }{{\partial x}}\left( {{k_x}\frac{{\partial h}}{{\partial x}}} \right) + \frac{\partial }{{\partial \textit{z}}}\left( {{k_\textit{z}}\frac{{\partial h}}{{\partial \textit{z}}}} \right) + S = \frac{{\partial \theta }}{{\partial t}} $$ (3)

      式中:$ {k_x} $、$ {k_{\textit{z}}} $——$ x $和z方向的渗透系数/(m·d−1);

      $ h $——某点测压管水头/m;

      $ S $——源汇项;

      $ \theta $——含水率/%;

      $ t $——时间/s。

      孔隙水压力,也称静水压力,是降雨诱发滑坡的主要机制[20]。降雨入渗和地下水的流动增加孔隙水压力,降低有效应力,最终会削弱岩土体的物理力学指标,改变岩土体的力学性质,降低边坡稳定性。

      对抚顺西露天矿南帮滑坡形成机制的研究,提出水与重力作用下南帮滑坡形成机制的概念模型,模拟选取抚顺西露天矿E1200南帮典型地质剖面为研究对象,南帮边坡模型见图3,数值模拟图见图4,其中模型长1300 m,宽500 m,高510 m。根据矿区试验资料及工程类比法,对南北帮岩土的物理力学参数进行参考,以确定算例计算参数。岩土力学参数取值见表1

      图  3  南帮滑坡形成机制模型
      Figure  3.  Model of formation mechanism of the southern slope of Fushun west open pit mine
      图  4  数值模拟图
      Figure  4.  Numerical simulation diagram
      表  1  岩土体的物理力学参数取值[2125]
      Table  1.  The physical and mechanical properties of the rock and soil mass [2125]
      地层岩性密度
      /(kg·m−3
      弹性模量
      /GPa
      泊松比黏聚力
      /MPa
      抗拉强度
      /MPa
      内摩擦角/(°)渗透系数
      /(m2·Pa−1·s−1
      凝灰岩2590100.2432459E-10
      凝灰岩(弱化)259010.240.30.2409E-10
      玄武岩2800250.2332409E-10
      玄武岩(弱化)28002.50.230.30.2359E-10
      14001.20.240.450.15309E-10
      煤(弱化)14001.20.240.450.24353E-9
      弱层2100150.242.51.75489E-10
      弱层(弱化)21000.0180.40.0030.01109E-10
      花岗片麻岩2800350.2243458E-9
      回填土18600.270.30.20.1259E-10
      回填土(弱化)18600.0270.30.020.01209E-10
      断层泥18000.010.40.180.273E-9
      油页岩255050.220.150.35359E-10
      下载: 导出CSV 
      | 显示表格

      通过对现场地质条件调查,边坡中的弱层1(古风化壳)、弱层2(玄武岩夹煤线)为相对强透水层,弱层1与弱层2之间的玄武岩和弱层2以上岩层为弱透水层,基底岩层花岗片麻岩为相对隔水层,取比奥系数为1。本次数值模拟利用FLAC3D有限元仿真计算平台进行动力与渗流的耦合分析,对抚顺西露天矿南帮顺倾软弱夹层边坡进行分析。分析过程中,考虑降雨及地下水对南帮边坡演化过程的影响,初始阶段采用Mohr-Coulomb模型在模型成型后,确定边界条件,地下水设置左侧水头高410 m,右侧水头高160 m,重力固结模型,稳定后模型整体位移清零,重新定义材料为Finn模型,距坡表50 m距离的表土参数调整为弱化参数,设定坑底地面以下初始含水状态为饱水,在边坡顶部及坡面施加降雨入渗边界,入渗速率为185.9 mm/24 h,进行水−岩之间的渗流耦合分析,对地下水及降雨入渗作用下顺倾多软弱夹层边坡滑动过程进行演化模拟。

      图5显示边坡在地下水及降雨作用下总位移变化图。图5(a)在地下水及降雨入渗作用下的初始阶段,坡体的最大位移主要出现在玄武岩弱层2及坡脚回填土附近,由于地下水的作用使玄武岩弱层2处首先发生蠕动变形,最大总位移量值约为0.60 m,坡角处最大总位移约为0.26 m,凝灰岩具有吸水性优良、导水性差的特性,含水量快速提升,导致回填土层在入渗初期破坏变形区域在边界面迅速发展,最大总位移约为0.25 m。

      图  5  坡体随循环步长增加的总位移变化情况
      Figure  5.  The variation of the cumulative displacement of the slope with increasing cycle steps

      图5(b)显示随循环步长增加的第一阶段,地表雨水不断入渗,地下水位提升,导致土壤饱和度增加、抗剪强度减小、有效应力降低、体积应变增大、孔隙水压力上升,玄武岩最大变形区域沿弱层2向坡顶发展,降雨期间凝灰岩岩层含水量持续增加,边坡表面裸露的松散杂填土发生小型剥落,最大总位移约为0.8 m。降雨期间坡脚裸露煤层抗压强度降低,上部岩体重力产生的压应力导致煤层被挤出不断向外鼓胀。

      图5(c)显示随着降雨和地下水的持续作用的第二阶段,玄武岩最大变形区域沿弱层2向坡顶发展并贯通,使坡顶产生裂缝,加速雨水入渗,抗剪强度减小,弱层2附近的岩体节理逐渐张开和错动,为地表水渗透和地下水的运移提供通道,弱层1处下部的岩体变形加剧,最大总位移约为0.88 m。弱层2上部形成明显的滑移面,最大总位移约为0.94 m。回填土滑移范围不断增大扩展至凝灰岩岩层,最大总位移约为0.90 m。

      图5(d)表明第三阶段,边坡上部玄武岩发生二次垮塌,坡体最大变形区域集中到表层玄武岩中,最大总位移约为1.27 m。这意味着斜坡内的应力场在降雨和地下水的持续作用下迅速变化,形成了承压和潜水含水层混合水力模型。入渗过程中弱层土体强度降低,有效应力降低,孔压增大,边坡最大总位移增大,导致边坡稳定性显著降低。

      图6为地下水及降雨作用下坡体随循环步长增加塑性区变化状态,图6(a)表明,在地下水及降雨入渗作用下的初始阶段,边坡顶部、玄武岩弱层2及回填土层均出现了拉张破坏。在坡体中部弱层2周围的玄武岩及凝灰岩岩层处存在大量的剪切破坏区。

      图  6  坡体随循环步长增加发展的塑性区变化情况
      注:none为无变化单元;shear-n为当前循环中出现剪切破坏单元;shear-p为以前循环中出现剪切破坏单元;tension-n为当前循环中出现张拉破坏单元;tension-p为以前循环中出现张拉破坏单元。
      Figure  6.  Changes in the plastic zone developed by the slope with increasing cycle step

      图6(b)表明边坡坡体产生的拉张破坏贯通坡顶,残余节理由于存在拉伸破坏逐渐张开,形成常见的后缘拉张裂缝,为降雨的入渗提供了良好的通道。回填土上部及沿凝灰岩边界区域产生拉张破坏,上部松散杂填土发生小型滑移。坡脚地面表层的拉张破坏会导致底鼓,这与抚顺西露天矿南帮现场滑坡后缘出现的地裂缝和坑底鼓胀破坏现象是一致的。

      图6(c)表明,第二阶段时,随着降雨及地下水的持续作用,边坡体中当前发生剪切破坏的区域逐渐扩展延伸至坡体弱层2上方玄武岩处,剪切破坏区基本连通,预示着潜在滑面的形成。坡脚附近的破坏状态转变为当前剪坏状态,意味着滑坡将在坡脚剪出。

      图6(d)表明,坡顶弱层1处出现拉张破坏,边坡体中剪切破坏的区域基本扩展至坡体弱层2上方整个玄武岩处,坡底出现剪切破坏,表明滑体将在坡脚部位剪出,最终堆积在坡底。由于边坡后缘孔隙水压力和动水压力的相互作用以及滑动面上承压含水层的承载力,边坡在雨季易发生失稳破坏。

      为了便于更好地绘制南坡随时间推移的变形分布和发展情况,在南帮边坡设置监测点,具体位置如图7所示。

      图  7  监测点位置示意图
      Figure  7.  Schematic diagram of the location of the monitoring points

      根据上述设置的边坡监测点对边坡变形演化过程进行跟踪监测,绘制如图8所示各监测点体积应变增量变化曲线及图9所示x方向有效应力变化曲线。

      图  8  监测点体积应变增量随时间的发展演化情况
      Figure  8.  Evolution of the development of volumetric strain increments over time at monitoring points
      图  9  监测点x向有效应力随时间的发展演化情况
      Figure  9.  Evolution of the development of the effective stress in the x-direction over time at monitoring points

      根据图表可以看出,监测点A3和A4体积应变增量在初始阶段持续变大,坡顶x向有效应力总体出现减小趋势,说明坡顶回填土中存在许多微裂缝,渗透性强,加速雨水渗透,点A3处形成裂隙与坡体内弱层2贯通,雨水径流汇入裂隙产生渗透压力,导致边坡土体含水量增大,孔隙压力加速累积,抗剪强度减小,表层不断破碎滑落,导致孔隙压力减小,有效压力增大。点A2体积应变量在发展第三阶段减小,点A1在第二阶段x轴反向压应力快速减小,表明点A1在降雨过程中含水量增大,岩体不断滑落外移,土体相对松散,孔隙压力随之增大,使滑动面上的有效应力及抗剪强度减低,导致滑坡失稳。B区与C区为边坡内部监测区域,体积应变量和x方向有效应力变化趋势相似,点B3和C3为弱层2内选取的监测点,点B5和C5为边坡表层选取的监测点,降雨期间边坡表层有限深度产生饱和区,孔隙压力增长速度快,雨水径流渗入裂隙与弱层贯通,导致弱层含水量增大,孔隙压力增大,岩体损伤破坏,形成潜在滑面。图8中点D1位于玄武岩底部,在第一阶段体积应变增量变大,点D2和D3在第三阶段体积应变量增长速率较快,图9中点D1、D2、D5的x向应力增大,第一阶段D3、D4有效应力快速降低,坡脚回填土在入渗初期迅速发展,体积应变增大,孔隙压力随之增大,表层松散土产生小型剥落,坡脚向外鼓胀。

      综合稳定性计算分析结果和监测成果可知,抚顺西露天矿南帮顺倾含软弱夹层边坡在地下水及降雨入渗作用下稳定性较差,形成多次级滑块滑动,兼具后缘推移与前缘牵引特点,整体呈现混合式滑坡,这与郭富赟等[26]分析舟曲滑坡结论一致。第一阶段坡体顶部发生变形,产生裂隙为降雨入渗提供通道,第二阶段坡脚变形渐进向后发展,坡顶发生小型垮落,中后部滑移面贯通,推动滑体前缘,引起滑移-隆起-整体下滑破坏,滑坡后缘利于雨水入渗,第三阶段在降雨入渗、积聚作用下,边坡后部变形破坏,再次形成贯通滑动面,整体发生滑移-拉裂-剪断破坏。

      在雨水入渗和地下水的双重作用下,边坡岩石破碎,稳定性低。持续发展的滑坡将影响露天矿的安全。因此,采取在边坡上修建排水沟、减小边坡角、覆盖人工植被等有效方法和措施,以提高边坡的结构稳定性。滑坡未采取抗桩、锚索等加固措施的原因主要是边坡岩石松动,边坡表面很难为锚索提供足够的锚固力。为了满足锚固强度的要求,就有必要延长锚链段的长度,从而增加成本。调整边坡角和坡脚进行回填压脚措施均能提高边坡稳定性,但回填压脚措施可增加排土场收容量,同时缩短压脚区域运动距离。故结合地质环境等因素,最终提出在坡脚进行回填压脚措施的治理措施。

      对边坡进行压脚措施主要是保证边坡高度不变。采用土石等材料堆填在滑坡前缘,以确保边坡高度不变,控制边坡防护的稳定性满足安全要求。具体治理方案:在现状边坡基础上进行压脚,堆填高度设计方案为41 m(1/10坡高),82 m(1/5坡高),103 m(1/4坡高),137 m(1/3坡高),206.5 m(1/2坡高),246 m(3/5坡高),274(2/3坡高),309.5 m(3/4坡高)。采用极限平衡法,计算不同压脚方案的边坡稳定性系数,分析滑坡稳定性(表2)。

      表  2  边坡防治方案稳定性评价结果
      Table  2.  Stability evaluation results of slope control scheme
      工况防治方案剖面图边坡总位移变化云图安全系数稳定性分析
      现状1.22稳定
      降雨0.71不稳定
      回填1/10
      坡高
      0.89不稳定
      回填1/5
      坡高
      0.96不稳定
      回填1/4
      坡高
      1.02欠稳定
      回填1/3
      坡高
      1.08欠稳定
      回填1/2
      坡高
      1.15稳定
      回填3/5
      坡高
      1.21稳定
      回填2/3
      坡高
      1.42稳定
      回填3/4
      坡高
      1.36稳定
      下载: 导出CSV 
      | 显示表格

      根据表2可知,边坡安全系数>1.1时,坡体稳定性较好;安全系数处于1.0~1.1间,坡体处于欠稳定状态;安全系数<1.0时,边坡即发生破坏。该边坡在自然条件下基本稳定,降雨后边坡处于失稳状态,安全系数降低了0.51,因此可认为降雨影响是边坡发生失稳的主要原因。在8种不同压脚高度的防治方案中,回填1/10坡高和回填1/5坡高的方案对边坡安全系数有所提高,但未起到明显防治效果;回填1/4坡高和回填1/3坡高的方案对固坡护坡产生一定的作用,边坡从不稳定状态转至欠稳定状态;回填1/2坡高和回填3/5坡高的防治方案起到了显著效果,两种方案中边坡弱层均发生蠕动变形,却未形成贯通剪切滑移面;回填2/3坡高和回填3/4坡高的防治方案对提高边坡稳定性同样起到显著效果,但需耗费大量回填物料,不符合工程措施的经济合理性。

      相比边坡现状工况下,采用不同坡高高度回填压脚防护的边坡具有较高的安全系数。随着压脚高度提升边坡表面最大总位移量呈现出减小趋势,坡内部滑移区域分布相对稳定,安全系数增大,稳定性提高。说明边坡防治措施可以有效改善边坡应力场,控制边坡整体变形,提高边坡稳定性,为类似滑坡防护治理技术提供参考。最终考虑工程实际综合比较不同防治方案,在降雨影响下,回填压脚至1/2坡高高度防治效果更好,边坡较稳定。

      (1)地下水及降雨入渗作用下,边坡形成多阶段滑坡,坡面产生最大变形区域的总位移约为1.27 m,滑坡整体兼具后缘推移与前缘牵引特点,呈现混合式滑坡。

      (2)边坡变形破坏期间,在坡体内部的弱层首先发生蠕动变形,产生剪切破坏面,坡顶地面出现两级错动式地裂缝,呈现典型多滑面特点,为地表水渗透和地下水运移提供了通道,进一步加速了边坡变形。

      (3)边坡土体失稳的过程中离不开孔隙水压力的作用,边坡内部土体随耦合作用含水率累积增加,体积应变增量降低,有效应力降低,孔压呈现阶段累积上升趋势,边坡形成滑动面启动后孔隙水压力具有瞬态爬升特点。

      (4)在边坡稳定性分析成果基础上,提出了坡脚进行回填压脚的边坡防治措施,随着压脚高度提升边坡表面最大总位移量呈现出减小趋势,坡内部滑移区域分布相对稳定,安全系数增大,稳定性提高。

    • 图  1   西藏山南措美县鲁麦古滑坡地质背景图

      1—下白垩统拉康组一段;2—下白垩统拉康组二段;3—下侏罗统日当组;4—侏罗系中~下统陆热组;5—中侏罗统遮拉组;6—灰岩脉体;7—辉绿玢岩脉;8—二云母二长花岗岩;9—鲁麦古滑坡;10—河流;11—滑坡边界;12—岩层产状;13—平移断层;14—正断层;15—逆断层

      Figure  1.   Geological background map of the Lumai ancient landslide in Cuomei County, Shannan City, Xizang

      图  3   西藏山南措美县鲁麦古滑坡工程地质剖面(A—A’)

      1—泥岩;2—粉质黏土夹碎石;3—砂岩;4—第四系松散滑坡堆积层;5—下白垩统拉康组下段层;6—滑带;7—推测原始地形线;8—前缘堆载区;9—钻孔

      Figure  3.   Engineering geological profile (A-A’) of the Lumai ancient landslide in Cuomei County, Shannan City, Xizang

      图  2   西藏山南措美县鲁麦古滑坡遥感影像图

      Figure  2.   Remote sensing image of the Lumai ancient landslide in Cuomei County, Shannan City, Xizang

      图  4   西藏山南措美县鲁麦古滑坡复活变形特征

      Figure  4.   Reactivation and deformation characteristics of the Lumai ancient landslide in Cuomei County, Shannan City, Xizang

      图  5   西藏山南措美县鲁麦古滑坡多期影像特征

      Figure  5.   Multi-stage image characteristics of the Lumai ancient landslide in Cuomei County, Shannan City, Xizang

      图  6   西藏山南措美县鲁麦古滑坡数值计算模型

      Figure  6.   Numerical Calculation model of the Luma ancient landslide in Cuomei County, Shannan City,Xizang

      图  7   不同工况下鲁麦古滑坡水平位移云图

      Figure  7.   Horizontal displacement contour map of the Lumai ancient landslide under different conditions

      图  8   不同工况下鲁麦古滑坡剪应变增量云图

      Figure  8.   Shear strain increment contour map of the Lumai ancient landslide under different conditions

      表  1   鲁麦古滑坡数值模拟参数取值

      Table  1   Numerical simulation parameter values for the Lumai ancient landslide

      岩性 体积模量
      /MPa
      剪切模量
      /MPa
      天然工况 地表水入渗工况
      内聚力
      /kPa
      内摩擦角
      /(°)
      内聚力
      /kPa
      内摩擦角
      /(°)
      泥岩 5.4 3.8 50.0 32.0 40.0 25.6
      粉质黏土
      夹碎石
      4.2 2.1 12.0 15.0 9.6 12
      下载: 导出CSV
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    • 收稿日期:  2024-03-08
    • 修回日期:  2024-07-19
    • 录用日期:  2024-08-19
    • 网络出版日期:  2024-08-28
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