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本文采用物理机制模型、数值模拟和理论计算相结合,分析研究了顺层斜坡滑移-弯曲变形机制,提出了顺层斜坡产生滑移-弯曲变形的地质和力学条件、临溃状态判别与早期识别标志。研究认为:岩层倾角20是滑移-弯曲变形产生的必要地质条件。斜坡前缘岩层弯曲隆起是临溃状态的早期判识标志。岩层倾角、单层厚度、临界坡长和溃屈深度之间相互制约和影响。岩层倾角越大,越易产生溃屈,且溃屈层数和深度越大;斜坡临界坡长与岩层倾角呈负幂函数变化规律;层间黏结作用产生的共弯效应影响弯曲岩层的整体抗弯刚度,从而制约溃屈深度并对斜坡最终溃屈状态起着决定性作用。该成果对于早期防范和识别地质灾害具有重要价值。 相似文献
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总结国内外实例数据发现:缓倾条件下顺层斜坡能够产生滑移-弯曲变形;同类滑坡具有隐蔽性强、体积规模巨大、滑动面后陡前缓、多层滑动、突发性、高速、滑动距离有限等特征;顺层斜坡产生滑移-弯曲变形的必要条件为岩层倾角20°～60°、岩体软硬相间、节理与裂隙发育、岩层倾角>斜坡坡角、坡长达到数百米及以上、岩体剩余下滑力大于其临界值。为了研究缓倾顺层岩质斜坡滑移-弯曲变化过程,以常吉高速公路朱雀洞滑坡为例,采用地质调查、文献查询、理论计算、物理模拟相结合。首先对滑坡基本特征及其成因机制进行细致研究,建立了滑移-弯曲变形力学模型,进行了变形条件判别、稳定性评价。在此基础上,运用物理模型试验分析方法,再现了斜坡变形破坏演化过程,进一步证实了其滑移-弯曲型变形破坏机制。 相似文献
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三峡库区基岩顺层滑坡大多以砂/泥岩或泥/泥灰岩互层滑坡为主,力学机制以顺层滑移剪切为主。新近发现的青石-抱龙段顺层灰岩库岸,岸坡岩性以灰岩、白云岩为主。在21个顺向斜坡中9个斜坡存在岩层弯曲现象,高程分布在145~175m,且大量层面有擦痕,局部岩层强烈弯曲形成了类似逆断层的现象。这些变形破坏现象受控于重力作用下沿层面的滑移-弯曲力学机制。通过连续-非连续数值分析方法研究表明,在这一带岸坡中约200m的主动平直滑移段下滑力驱动了约30m的被动弯曲隆起段变形,被动弯曲隆起段位移地形变缓、岩层增厚。当前青石-抱龙一带顺层灰岩库岸岩层隆起和松动较小,处于滑移-弯曲变形的早期阶段,主要以累进性变形为主。建议对该段库岸进行专业监测,并开展进一步的调查研究工作。 相似文献
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反倾层状边坡弯曲折断的应力及挠度判据 总被引：9，自引：6，他引：3
以地质分析为基础 ,将反倾层状边坡的任意岩层概化为受复合作用力的板梁模型 ,通过简单的力学解析 ,开展了反倾层状岩石边坡弯曲折断判据的研究。依据岩层折断时和相临岩层的瞬时关系 ,将岩层下部视为瞬时临空状态 ,考虑岩层自重荷载和上部岩层附加荷载 (上部岩层重力荷载、层间摩擦力 )的共同作用 ,基于最大拉应力准则 ,提出了岩层弯曲折断的应力判据 ;依据应力判据 ,得到了岩层弯曲折断的挠度判据 ;利用应力判据及挠度判据 ,可实现反倾层状边坡弯曲折断的现场判定及其控制设计 相似文献
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顺层岩质边坡易发生失稳破坏,当边坡中发育有顺坡向陡倾结构面时,更不利于边坡稳定。以贵州某水电站大坝左岸含陡倾结构面顺层边坡为例,在综合分析地质条件及开挖扰动的基础上,结合离散元软件UDEC,分析了边坡的变形破坏模式和稳定性。研究结果表明,边坡可能发生的变形破坏模式主要有滑移、拉裂—滑移两种;自然状况下及开挖后,边坡都有沿断层f_9、卸荷裂隙L_1及岩层面发生滑移的趋势,且工程开挖导致边坡沿该结构面发生内部滑动;对边坡采用预应力锚索加固后,变形得到有效控制,位移数值计算值与实际监测值基本吻合。 相似文献
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针对不同倾向、不同倾角条件下,边坡变形破坏特征不同但缺乏相互对比分析研究的现状,在充分考虑硬岩岩质边坡变形破坏特征的基础上,配制硬岩相似材料,采用底摩擦试验方法,分析不同倾向、不同倾角边坡变形破坏模式,并借助PIVlab技术进行分析。结果表明:顺倾和反倾边坡变形破坏模式和破坏范围有明显区别。在45°坡度条件下,当顺倾边坡倾角由30°→45°→60°→80°转换时,变形破坏模式由滑移-拉裂→轻微滑移-弯曲（或滑移-剪切）→未有明显变形（整体稳定）→浅表部倾倒-拉裂逐渐演化。在45°坡度、反倾边坡条件下,变形破坏模式由岩层倾角30°和45°条件下无明显变形,逐渐向60°和80°条件下的倾倒-拉裂演化。当岩层倾角较陡时,反倾边坡破坏范围相对顺倾边坡更大,倾倒弯曲转折端更深。PIVlab结果反映出不同结构边坡条件下,不同位置的速度和位移矢量特征不同,且与宏观观察结果相吻合。研究成果能够为同类边坡的稳定性评价和治理设计提供一定参考。 相似文献
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以往研究中倾倒变形研究在反倾边坡较多而在顺倾边坡中很少,对两种不同结构的边坡形成倾倒体的异同点更是存在较多空白。在总结大量倾倒体实例基础上,对层状反倾和顺倾边坡倾倒变形形成条件及发育规模特征进行了详细研究。结果表明,顺倾边坡若发生倾倒,通常表现为坡高 100 m,边坡坡角 35°,岩层倾角 60°,岩性为薄层或薄层与中层互层的软岩、软硬相间的岩石;反倾边坡当坡角 30°及岩层倾角 30°就可能发生倾倒,其岩性为薄层～中厚层状的软岩、硬岩及具有似层状结构的坚硬岩石均可;提出层状岩质边坡“倾倒临界倾角 ”的概念,对于顺倾边坡, 60°,当 时边坡将可能产生倾倒破坏,当 时边坡通常产生顺层面的“滑移-弯曲”或“滑移-拉裂”型破坏;反倾边坡 30°,当 时边坡才可能演化成明显倾倒变形,当 时边坡不会倾倒或倾倒不明显;对于地质条件基本相同而坡体结构不同的两种边坡,反倾边坡形成的倾倒体无论是发育分布面积还是倾倒深度通常是大于顺倾边坡的,而且一旦形成倾倒体,二者的规模通常是深层的、大型或特大型的;倾倒体的分布面积和倾倒深度均呈现一种随坡高的增加而增加的趋势,坡高 250 m时其分布面积和倾倒深度表现为陡然增加,并且反倾边坡增加幅度大于顺倾边坡。 相似文献
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滑移-弯曲破坏是顺层岩质边坡的常见破坏模式之一。基于板裂结构顺层岩质边坡的地质成因分析,将最大拉应力强度理论引入到地质力学模型分析中;根据破坏特征,将板裂结构顺层岩质边坡的岩层带分为滑移段和弯曲段;采用能量法、Rayleigh-Ritz方法及势能驻值原理等近似模拟弯曲段的挠曲方程;运用梁板强度理论,推导了板裂结构顺层岩质边坡最大拉应力计算公式和边坡潜在破坏点预测模型;在此基础上,将理论公式程序化,通过典型滑坡算例,得到了理论预测值与实际破坏值的近似一致性;通过FLAC3D数值模拟软件分析了山阳滑坡的破坏过程,并得出：(1)滑坡体总位移的变化趋势呈现出明显的滑移-弯曲变化特征;(2)最大拉应力和张拉塑性区所在位置的数值模拟结果与理论计算结果近似一致。 相似文献
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The occurrence of foliated rock masses is common in mining environment. Methods employing continuum approximation in describing the deformation of such rock masses possess a clear advantage over methods where each rock layer and each inter‐layer interface (joint) is explicitly modelled. In devising such a continuum model it is imperative that moment (couple) stresses and internal rotations associated with the bending of the rock layers be properly incorporated in the model formulation. Such an approach will lead to a Cosserat‐type theory. In the present model, the behaviour of the intact rock layer is assumed to be linearly elastic and the joints are assumed to be elastic–perfectly plastic. Condition of slip at the interfaces are determined by a Mohr–Coulomb criterion with tension cut off at zero normal stress. The theory is valid for large deformations. The model is incorporated into the finite element program AFENA and validated against an analytical solution of elementary buckling problems of a layered medium under gravity loading. A design chart suitable for assessing the stability of slopes in foliated rock masses against flexural buckling failure has been developed. The design chart is easy to use and provides a quick estimate of critical loading factors for slopes in foliated rock masses. It is shown that the model based on Euler's buckling theory as proposed by Cavers (Rock Mechanics and Rock Engineering 1981; 14 :87–104) substantially overestimates the critical heights for a vertical slope and underestimates the same for sub‐vertical slopes. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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三峡库区在高程145~175 m之间周期性水位调控,促使库区灰岩岸坡劣化损伤加剧、稳定性衰减。本文结合巫峡段顺层灰岩岸坡“滑移-弯曲”破坏实例,基于弹塑性板翘曲模型,考虑岩体动态劣化概念,结合广义H-B准则中GSI(t)岩体参数动态指标,推导得临界挠曲段平衡方程。与传统静态计算方法相比,适用性更广,可以考虑岸坡随劣化时间t动态演化过程,更加符合工程实际。结果表明:随着劣化进行临界挠曲段lcr逐步降低,岸坡稳定状态变差,下滑推力F逐步增大,抗弯刚度K逐渐减小,也正是这两方面因素导致lcr快速降低。由于岩体劣化函数GSI(t)为指数劣化形式,故lcr呈现出快速降低并趋缓直至逼近一定值,该区段为岸坡防治的“关键区段”;随着岩层倾角α增大,lcr与相对板长比RPL快速降低,随着岩层厚度hi增大,lcr与RPL缓慢变大,α对lcr与RPL的影响明显大于hi。且岸坡lcr快速下降角α大约在40°~60°,可作为类似顺向岸坡是否容易滑移-弯曲失稳的地质判据。本文推导的考虑岩体劣化的临界平衡方程,以三峡库区青石6号岸坡为例进行了计算、论证。可为其他类似顺层岸坡损伤演化计算提供借鉴,不同之处在于确定具体岸坡损伤劣化的GSI(t)函数式。 相似文献
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含软弱层岩质边坡的动力响应研究 总被引：1，自引：0，他引：1
含软弱层岩质边坡的动力响应研究已成为边坡工程稳定性分析中的一个重要问题。为研究软弱层的特性对岩质边坡动力响应的影响,提供动力荷载作用下边坡防灾减灾的指导依据,运用UDEC离散元软件模拟地震力作用下含软弱层岩质边坡的动力响应系统地分析软弱层的倾角、埋深、弹性模量、厚度、泊松比和剪切刚度等因素对地震波放大现象的影响,得出边坡坡顶放大系数的变化规律,即随着软弱层倾角的增大,放大系数呈现出增大→减小→再增大→再减小,并出现地震响应减弱的现象;放大系数随软弱层埋深和厚度的增加而增大,但随弹性模量、剪切刚度的增大而减小,随泊松比的增加几乎不变。结合非重复性试验二元方差分析评价理论,对所得的放大系数进行计算分析,得出软弱层的特性因素对边坡放大作用的影响强度为软弱层的倾角＞埋深＞弹性模量＞剪切刚度＞厚度＞泊松比。研究结果有助于进一步揭示地震作用下边坡的失稳机制, 对震区边坡灾害的防治有一定的指导意义。 相似文献
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倾倒变形常见于反倾结构边坡,特别在具有软硬互层结构边坡中,甚至可发育为深度上百米的大型滑坡。为进一步探明此类反倾边坡倾倒变形的破坏机制,以及边坡形态结构及岩体力学参数等因素的影响规律,以离心模型试验为原型,结合离散元数值模拟,分析了倾倒变形的形成过程以及在外界扰动下的破坏机制。并通过单因素分析法、正交设计法等,研究了多种因素对反倾边坡倾例变形的影响,通过极差分析获得了各因素的敏感性。通过在岩层内预置大量多边形随机裂隙,数值模拟较好地实现了对破裂面起裂及延展规律的模拟。结果表明:离心模型试验可较好地还原倾倒变形过程,而离散元数值模拟则可对实验结果进行有效的重现与扩展,两者吻合度良好;岩体变形过程存在3个阶段,即起始变形、稳态变形和失稳破坏等阶段;破裂面呈弧形,在变形积累到一定程度后快速形成;边坡可自下而上形成多级破裂面,并伴随岩层的强烈弯曲变形,在外界扰动下,倾倒变形体将由外到内沿不同破裂面形成渐进后退式破坏;多种影响因素中,边坡形态结构影响最大,层面参数次之,软硬岩岩石力学参数的差异影响较小;具体而言,边坡形态与坡体结构对倾倒变形的影响性大小表现为坡角＞倾角＞坡高＞坡形＞层厚比＞层厚,坡角、倾角、坡高越大,坡形越外凸,软硬岩层厚差越小,倾倒变形越容易发生;边坡变形规模主要受形态结构因素控制,倾角和坡角影响最显著。 相似文献
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反倾层状岩体斜坡弯曲-拉裂两种失稳破坏之判据探讨 总被引：11，自引：4，他引：7
对反倾层状岩体斜坡弯曲-拉裂的失稳破坏判据,已有研究分别基于两种力学模型进行推导,即竖直压杆弹性屈曲稳定和平直梁弯折破坏模型,但对层间错动阻力及挠度产生附加弯矩等因素未加以考虑,不尽合理。在反倾斜坡岩层受力分析基础上,建立考虑了板侧层间错动阻力的下端嵌固、上端自由的斜置等厚弹性悬臂板梁模型,统一地通过瑞利-里兹能量方法,推导了弹性屈曲临界条件和嵌固端弯折破坏临界条件。实例计算及讨论表明,弹性屈曲判据适用于陡立岩层;而中-陡反倾岩层应主要为弯折破坏,但层间的力学性质对弯折临界判据值具有较大影响。 相似文献
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In this study, two types of small-scale physical modeling tests have considered the impact of the infiltration of rainfall and groundwater level in order to investigate the processes involved in rock slope deformation and failure. The study conducted the physical tests under controlled conditions of groundwater level with rock block shape for two rock slope types (cataclinal and anaclinal slopes). Observations obtained during each stage of deformation and failure were used to explain how gravity deformation varies with groundwater conditions on cataclinal and anaclinal slopes, and infer how rainfall and groundwater influence slope failure. Our results indicate that groundwater level is a crucial factor in the deformation failure of slopes. The failure mechanisms of cataclinal slopes differ considerably from those of anaclinal slopes. The infiltration of surface water and groundwater can have a significant influence on rock layer deformation and the speed of failure. Different shapes of rock block have two toppling types of rock slope, the spherical rock model relatively close to flexural toppling type and the triangular rock model relatively similar to block flexural toppling type, respectively. Details of the failure characteristics of cataclinal and anaclinal slope models are discussed in this paper. 相似文献
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Progressive failure in long natural clay slopes with an underlying weak shear zone is studied. The clay slope is assumed to be elastic–perfectly plastic, whereas the shear zone may have an elastic–plastic strain softening behaviour. The failure will occur due to the development of large shear deformations in the weak zone. The general behaviour, including the possibility of progressive failure, can be studied by the use of a one-dimensional finite element model. Other interesting matters which can be studied are critical load, critical disturbance and critical length of the slope. Numerical examples show the overall behaviour due to different residual shear strengths of the weak layer, end disturbance or change of pore pressure in the weak layer. Although simple, the proposed finite element model provides a practically applicable tool for the prediction of whether progressive failure will occur and in which manner the local failure will propagate. 相似文献
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S. Sreekumar 《Journal of the Geological Society of India》2009,73(6):813-820
The occurrences of slope failures are frequent in Idukki district of Kerala state particularly along the road cuttings and
hill slopes causing disruption in traffic, loss of lives and property. This demands a critical evaluation of stability of
slopes along the hill roads. This paper deals with stability analysis of a typical hard rock profile at Chuzhappu and a lateritic
profile at Kumili along the road connecting Kottayam and Kumili. A large number of factors have been examined and studied;
the orientation of discontinuities has been identified as one of the major inherent factors influencing slope instability
along Chuzhappu hard rock profile. These have been analysed carefully using stereographic/equal area projection technique
in order to determine the vulnerability to slope failure and to understand the type of rock slide that can occur in this profile.
The buoyant force of water acting along the discontinuities after heavy rain storm further aids the down slope movement. As
the laterite slope is mostly homogeneous, Bishops method and Swedish method were adopted for stability analysis of laterite
slope at Kumili. The study also examines the efficacy and applicability of the different methods employed in soil mechanics
to assess the stability of laterite slope.The results obtained by this method are compared by actual field conditions. The
stability assessment indicates that two sectors at Chuzhappu and one sector at Kumili profile are at the geo-technical threshold
of failure, when piezometric head rises during rainstorm. The study indicates that these methods are highly useful in determining
the Factor of Safety in profiles with similar geological setting. 相似文献