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1.
黄土边坡中竖直裂隙的发育往往会对边坡稳定产生影响。相对于平面应变机制,建立三维破坏机制下边坡稳定性分析方法更能接近实际边坡失稳情况。基于塑性极限分析上限法,考虑预先存在竖直裂隙的三维黄土边坡不同破坏机制（坡面破坏、坡脚破坏和坡底破坏）,建立能量平衡方程及其无量纲临界高度值γH/c表达式,采用随机搜索法得到了临界高度的上限解。分析了约束宽度、边坡坡度、内摩擦角以及裂隙深度对三维竖直裂隙黄土边坡临界高度值的影响。结果表明：对于坡脚破坏机制,临界高度值随着裂隙深度的增加而减小,减小至临界裂隙深度 (δ /H)min后,裂隙深度的增加不再影响临界高度值;临界裂隙深度随着坡度β 的增大而增大,随着内摩擦角φ 的增大而减小。当约束宽度B/H<0.8时,大多数破坏机制为坡面破坏。当约束宽度B/H=0.8、内摩擦角φ =10° 及约束宽度B/H=0.6、内摩擦角φ =15° 时,边坡的破坏从坡面破坏机制逐渐过渡到坡脚破坏机制。存在竖直裂隙的黄土边坡比完整边坡具有更小的临界高度,约束宽度及内摩擦角会对三维黄土边坡破坏机制产生影响。 相似文献
2.
基于非线性Mohr-Coulomb破坏准则,结合极限分析上限法和拟静力分析法,建立功能方程,推导了地震效应下裂缝边坡的安全系数计算方程。采用数学规划方法,计算了不同参数组合条件下的边坡安全系数值,详细分析了非线性条件下一系列参数对边坡稳定性的影响。研究表明,边坡安全系数随非线性参数和地震效应的增大而减小。对比分析可知,在非线性破坏准则下,裂缝深度较大时,裂缝对边坡稳定性影响显著,且边坡越陡影响越大;当裂缝深度超过某个值后,临界破坏面起始端可能不穿过裂缝最底端,而是从裂缝中间某部位穿过。在地震效应作用下,非线性抗剪强度参数对安全系数影响显著。研究成果进一步完善了裂缝边坡稳定性分析内容,所列图表为边坡的设计与施工提供有益参考。 相似文献
3.
当坡体后沿产生张裂缝时,通常意味着坡体接近极限平衡状态,滑坡可能发生,若遇降雨,张裂缝充水产生的水压往往是滑坡发生的启动因素,因为水压的大小与张裂缝的深度估算有关,是边坡稳定分析的重要条件之一。建立了一个坡体后部潜在三角形极限平衡体拉张模型,导出裂缝深度公式。应用拐点的数学性质原理,解出裂缝处与内摩擦角相应的滑面倾角,计算张裂缝深度系数,绘制了应用于实际的张裂缝深度系数的数值解曲线图。解释了张裂缝发生条件:裂缝处的滑面倾角必须小于裂缝深度系数的一阶导数的极值点确定的与土层内摩擦角对应的倾角α。给出了圆弧滑面和一种非圆弧滑面发生张裂缝位置的公式。与Spencer裂缝公式进行了比较,表明本文方法具有实用价值。 相似文献
4.
开挖卸荷作用下裂隙岩体边坡的破坏模式与路径分析是边坡工程灾害研究的热点之一,准确识别边坡的潜在破裂路径对工程安全施工和支护优化设计具有重要意义。依据断裂扩展分析方法,将裂隙扩展判别的理论方法开发并应用于数值模拟分析中,通过裂隙尖端应力强度因子计算、裂隙扩展模式识别、裂隙起裂角演算、裂隙扩展交汇等技术实现了岩体中断续裂隙的起裂、扩展与贯通演化过程的快速模拟;以某高速公路沿线裂隙岩体路堑边坡为对象,采用提出的模拟方法分析了多级开挖卸荷作用下坡体裂隙的扩展机制与边坡的破坏路径。结果表明：裂隙岩体边坡从上至下多级开挖过程中,坡肩裂隙首先起裂,并通过拉张型扩展逐渐发展为优势裂隙;随着边坡下挖,优势裂隙沿坡面向下逐步发生拉张/剪切混合型扩展并与既有裂隙交汇,在边坡中上部形成阶梯状扩展破坏路径;裂隙扩展至边坡下部及坡脚后扩展模式由拉张/剪切混合型转化为剪切型,并最终以弧形剪切面从坡脚出露。研究揭示了裂隙岩体边坡多级开挖卸荷作用下上部阶梯状拉张/剪切混合型破裂-下部弧形剪切型破裂的复合破坏模式,可为边坡工程支护设计和施工稳定性控制提供新思路。 相似文献
5.
土工织物加筋土坡稳定的塑性极限分析法 总被引：6，自引：3，他引：6
在塑性极限分析理论的基础上，本文给出了土工织物加筋土坡稳定数的上限解。与无筋土坡的已有解比较表明，该解是可靠的，从而为土工织物加筋土坡的稳定分析提供了一个有效的方法。此外，本文的计算结果表明，各种因素对土坡稳定性的影响程度随坡角的增大而减小。 相似文献
6.
K.E.N. Tsidzi 《Geotechnical and Geological Engineering》1997,15(1):31-45
Summary Road cutting slope design in tropical terrains often tends to be conservative when based on the methods of classical slope stability analysis. This could be attributed to the difficulties encountered in the accurate characterization of tropically weathered rocks and soils, and the time-dependent improvement in soil properties resulting from haematite-hardening of the slope faces. A field-orientated approach, based on a slope performance survey of both natural and existing cutting slopes in similar geo-environmental settings, often tends to provide a more reliable alternative for the design of cutting slopes along new roads. This paper presents the results of slope performance studies carried out at selected locations in Ghana as a guide to designing cutting slopes along two proposed road projects in the southwestern sector of the country. It is recommended that slopes in competent lithologies along the proposed roads should be cut at steep inclinations of 72° and 80° while slopes in the less competent lithologies should be cut at flatter inclinations of 45°. 相似文献
7.
地震导致山体大范围开裂松动,使岩体裂缝（隙）张开、扩展进而形成危险的震裂边坡。裂缝是控制震裂边坡变形破坏的切割边界和滑移边界,为此,考虑裂缝扩展、裂缝充水和地震影响,采用极限分析上限法对汶川地震震中附近的一实地震裂边坡的稳定性变化进行分析。计算结果揭示了随裂缝扩展延伸,在雨水、地震作用影响下震裂边坡稳定性变化规律,为类似边坡的分析评价与工程治理提供了理论依据。 相似文献
8.
地震效应和坡顶超载对均质土坡稳定性影响的拟静力分析 总被引：3，自引：0，他引：3
基于强度折减技术和极限分析上限定理,假定机动容许的速度场破坏面,考虑坡顶超载、水平和竖向地震效应影响推导了边坡稳定性安全系数的计算表达式。采用序列二次规划迭代方法（和内点迭代方法）对边坡安全系数目标函数进行能量耗散最小化意义上的优化计算,与多个算例的对比验证了其方法和程序计算的正确性;对影响土质边坡动态稳定性的一些因素进行了参数分析,分析表明：随着边坡倾角?、坡顶超载q、水平和竖向地震效应影响系数的增大,边坡稳定性安全系数显著下降;随着坡顶超载q、水平地震效应影响系数kh的增大、竖向地震效应影响系数kv的减小,边坡的潜在滑动面越来越深,潜在破坏范围越来越大。竖向地震效应对边坡稳定性也有一定影响,强震条件下的设计计算必须考虑竖向地震效应的影响。 相似文献
9.
Lithological information, rock mass fracture data and discontinuity shear strength obtained through field investigations have been used to conduct kinematic and block theory analyses for the rock slopes that exist in the dam site to evaluate the stability of the slopes. The analyses were performed using mean discontinuity set orientations for each rock mass region under gravitational loading to calculate the maximum safe slope angles (MSSA) for different cut slope directions. Results show that final MSSAs obtained from kinematic analysis are less than or equal to that obtained from block theory analysis. The following conclusions have been made based on the block theory analysis results, which are closer to the reality: (1) The final MSSA range between 30° and 47°, 44° and 70°, 47° and 69° for cut slope dip directions of 20–30°, 105–210°, and 270–355°, respectively; (2) For cut slope dip directions of 20–30°, 200–210° and 275–315°, wide ranges of values have been obtained for the final MSSA reflecting the influence of variability of fracture orientations on MSSA; (3) Apart from the region R-d-1 for slope dip directions in the range 20–30°, rest of the regions at the dam site seem to be stable for slope angles less than 40°. Detailed comparisons are given between the kinematic and block theory analyses covering both the theoretical concepts and application results. Also a brief comparison is included between the laboratory and in situ discontinuity shear strength results. 相似文献
10.
地震易发地区的锚固岩石边坡,需要研究其地震稳定性。对于锚固典型岩石边坡,在考虑水平与竖向地震力、张裂缝积水深度、坡顶超载、锚索倾角、锚索位置、锚索拉力及静水与动水压力等的条件下,运用拟静力和拟动力方法分别推导了不同工况条件下其抗滑和抗倾覆地震安全系数。分析表明,竖向向上地震力有利于锚固岩石边坡的抗滑稳定,而竖向下的地震力有利于锚固岩石边坡的抗倾覆稳定;在相同工况条件下,当岩体放大系数等于1.0时,拟动力与拟静力方法所得锚固岩石边坡地震安全系数相差无几,但是,当岩体放大系数逐渐增大时,拟动力方法所得地震安全系数越来越明显地小于拟静力方法所得地震安全系数。因此,在抗震设计当中适当的考虑岩体放大系数,将会有利于锚固岩石边坡的安全设计。 相似文献
11.
Jeongi-Gi Um Pinnaduwa H. S. W. Kulatilake 《Geotechnical and Geological Engineering》2001,19(1):21-42
The granitic rock mass that exists in the shiplock region of the Three Gorges dam site contains a number of major discontinuities and about four sets of minor discontinuities. One hundred and thirty three major discontinuities have been mapped around the shiplock covering an area of 1740×600 m. These major discontinuities were used to perform rock slope kinematic and block theory analyses. Kinematic analyses were performed under the following two cases: (1) assuming all the mapped discontinuities cross the shiplock; (2) using only discontinuities that actually intersect the shiplock. Under case (1) and case (2) the shiplock faces in the proposed permanent shiplock region in fresh rock were found to be stable up to a cut slope of about 45° and 58°, respectively. Block theory was applied to identify different block types that exist on the shiplock faces and to estimate the maximum safe slope angles on the shiplock faces. The orientations of the major discontinuities that actually intersect the shiplocks were considered in this analysis. The total length of the shiplock (1750 m) was divided into 50 m segments. From the stereo-plots, the key blocks (Type I) and/or potential key blocks (Type II) were found for only five segments of the shiplock slopes. It was found that the dip of the cut slope should be less than about 60° to avoid creation of a key block on the proposed shiplock slopes. However, it is important to keep in mind that these conclusions are based on the kinematic analyses performed using only the major discontinuities. Further kinematic as well as kinetic analyses are recommended incorporating minor discontinuities, water forces, earthquake forces etc. before making the final conclusions about the maximum safe slope angle for the shiplock region. 相似文献
12.
13.
顺层岩质边坡地震动力响应研究 总被引：1，自引：0，他引：1
地震作用下边坡的动力响应研究是边坡动力稳定分析的基础,利用FLAC3D有限差分软件建立一个顺层岩质边坡动力数值模拟模型,对其在竖向和水平向地震耦合作用下的动力响应全过程进行研究。研究表明,地震竖向和水平向耦合作用模拟比简单的模拟水平向振动更加接近实际情况,对岩土体的破坏更大;顺层岩质边坡在耦合地震作用下存在垂直放大和临空面放大作用;坡面水平向和竖向加速度均随高程增加呈增大趋势,在结构面处增大特别明显;竖向地震波产生的水平与竖向拉裂是触发斜坡体产生初期崩滑破坏的主控因素;边坡动力响应特征值的放大效应表明,其放大系数值从大到小依次是：竖向加速度＞水平加速度＞竖向速度＞水平速度;耦合地震波作用下,随着av /aH的增大,坡面监测各点横向位移基本呈增大趋势,说明竖向地震作用起了重要的破坏作用。 相似文献
14.
降雨持时较长且雨强较大时,雨水的入渗不仅会增大孔隙水压力,且易使张裂缝充水形成静水压力,对边坡稳定不利。结合降雨条件下饱和-非饱和渗流分析,考虑降雨过程中的瞬态孔隙水压力场与瞬态强度场,并同时考虑张裂缝充水时的静水压力,对边坡临界滑动场法进行改进,提出降雨条件下具有张裂缝边坡临界滑动场数值模拟方法,且对其进行了验证。将该方法用于一个典型均质黏土边坡算例,结果表明,（1）文中方法可考虑张裂缝具体位置、深度及其充水状态下对边坡稳定性的影响,并能搜索出任意形状危险滑面,计算结果合理可靠;（2）降雨条件下张裂缝中静水压力对边坡稳定性及滑面形状有较大影响;（3）降雨条件下张裂缝位置对边坡稳定有较大影响,距坡肩越近,张裂缝对边坡稳定性影响越大;（4）张裂缝处在最不利位置且充水时存在一个最不利深度。 相似文献
15.
V. K. Singh D. G. Rao M. Prasad A. Sinha 《Geotechnical and Geological Engineering》1995,13(3):143-156
Summary The present study represents an attempt to optimize the overall slope angle of a lead-zinc mine in Rajasthan state, which could extend to a depth of 170 m during the first phase of mining. Detailed geotechnical investigations were conducted. These included geotechnical mapping, determination of the physio-mechanical properties of intact rock, determination of the rock mass rating and estimation of rock mass properties. Information was collected from mapping of benches and borehole logs. Based on these data, limit equilibrium and numerical simulation techniques were applied in order to assess the stability of the slopes and determine an optimum slope angle. From these investigations it has been inferred that the overall footwall and hangingwall slopes should be 42° and 48° respectively. 相似文献
16.
Pushpendra Sharma Amit Kumar Verma Anil Negi Manish Kumar Jha Pradeep Gautam 《Arabian Journal of Geosciences》2018,11(15):431
Thermoelastic deformation of rock significantly affects the stability of rock slope because thermoelastic strains may cause fracture propagation under favorable condition of failure. Rock slope stability depends on the balance between shear stress and shear resistance along the plane of weakness. Due to warming of rock slopes by heat transfer phenomena, viz. conduction and convection, considerable change in induced stresses (normal and shear) and resistance takes place which further causes instability in rock slope. In this paper, a two-dimensional finite element model has been used to simulate the stability of jointed rock slope containing crack in its upper surface. Four different cases have been simulated on the basis of infilling material (air, water, ice, water and ice) in the crack. Stability of rock slope is examined in terms of shear displacement and factor of safety for different thermal conditions of slope surface. A comparative study has been done for the four cases of infilling material in the crack. The various affecting parameters, viz. shear displacement, factor of safety, shear strength along the joint, and different surface temperature conditions, are illustrated by means of graphs. It has been found that the values of horizontal and vertical displacements are in the range of millimeters. The maximum values of horizontal and vertical displacements are 2.17 mm. Moreover, the maximum values of vertical compressive and tensile stresses are 15.4 MPa and 4.45 MPa respectively for the said four cases. According to the infilling material in the crack, the stability of the rock slope for the given geometry of slope is found in the following order: crack filled with ice < crack filled with ice and water < crack filled with water < empty crack. Validations of numerical results have been done from previous studies, and it has been found that the trends of normal stress, shear strength, and shear displacement along the joint are well matched. 相似文献
17.
水力和超载条件下锚固岩石边坡动态稳定性拟静力分析 总被引：1，自引：0，他引：1
基于极限平衡理论,综合考虑水力条件、坡顶超载、地震荷载效应和锚固效应对岩石边坡进行了全面的稳定性分析。计算给出了多影响因素条件下岩石边坡稳定性安全系数的表达式,并重点分析了几种相关参数组合对岩石边坡稳定性的影响。分析表明,坡顶张拉裂缝积水、地下水渗流作用、滑面出流缝被堵塞、地震影响效应不利于岩石边坡抗滑稳定性,而锚索锚固效应则对提高边坡抗滑稳定性有积极作用;坡顶张拉裂缝积水、滑面出流缝被堵塞、水平向地震影响效应都不利于岩石边坡抗倾覆稳定性,但锚索锚固效应、坡顶超载、与竖直方向地震效应则对提高边坡抗倾覆稳定性有益。最后针对工程实际,提出了相应的工程建议。 相似文献
18.
Most classical approaches for evaluating the stability of soil slopes with cracks are performed under two-dimensional (2D) condition. Three-dimensional (3D) effect and suction-induced effect of unsaturated soils are generally neglected in assessing the slope stability. This paper develops a 3D limit analysis method to evaluate the stability of an unsaturated soil slope with tension cracks under steady infiltrations. The boundary-value problem is formulated based on the 3D rotational failure mechanism by taking the effects of suction, effective unit weight, and tension crack into account. A simplified method is proposed to calculate the work rate of unsaturated soil weight. A layer-wise summation method is developed based on the divergence theorem to calculate the internal energy dissipation rate. Detailed discussions are conducted to investigate the effects of suction and Poisson's ratio on the stability of unsaturated soil slopes. Examples are given to illustrate the 3D effect, the suction-induced effect as well as the effects of infiltration and water in cracks on the slope stability. 相似文献
19.
Successive applications of two-dimensional circular slip limit equilibrium analysis of slices have been made to the three sections of the Cox's Bazar Coastal Cliff. These three sections have been found to be stable (S), quasistable (QS), and unstable (U) with factors of safety (Fs) of 1.269 ± 0.01, 1.13 ± 0.0504, and 1.01 ± 0.058, respectively. In the quasistable and unstable sections, the slopes suffered shallow slidings with slip circles parallel to the surface of slopes.The main causes of these slidings are steepness of slopes, lack of vegetation cover, erosion of toe accumulations by run-off water and waves during high tides. The influence of the slope geometry and the material's strength properties of slopes on safety factors are evaluated. The steeper cliffs reach an unstable condition faster than the more gentle cliffs as their heights change by an equal amount. Again, the high cliffs reach an unstable condition faster than the lower cliffs as slope inclinations change by an equal amount. The safety factor increases with a corresponding increase of friction angle (ø°) and vice versa.Abbreviations BK
Bahar chara to Kalatali chara
- KR
Kalatali chara to Reju khal
- RI
Reju khal to Boro Inani khal
- Fs
Factor of Safety
- S
Stable
- QS
Quasistable (semistable)
- US
Unstable 相似文献
20.
层状岩质边坡破坏模式及稳定性的数值分析 总被引：3，自引：0，他引：3
运用FLAC3D模拟层状岩质边坡的破坏模式,并采用强度折减法分析结构面倾角与稳定性之间的关系。结果表明:①水平层状边坡坡顶变形破坏早于坡面和坡脚,形成拉破坏区。当结构面倾角较小时,顺倾向层状边坡主要发生滑移破坏;当结构面倾角较大时,发生弯折-溃曲破坏。直立层状边坡主要发生弯曲-板间拉裂-塌落破坏。逆倾向层状边坡的破坏形式为对于小倾角为滑移破坏,对于陡倾角为倾倒破坏。②对于顺倾向边坡,整体安全系数随结构面倾角先减小后增大,呈现两头高、中间低的形态,在倾角为30°时安全系数最小;对于逆倾向边坡,曲线呈现增大-减小-增大的态势,并且大部分高于顺倾向边坡曲线,符合实际情况。③所采用的低强度弹塑性单元能够比较真实地模拟软弱结构面的变形。 相似文献