For the combination of flexural toppling failure and other failure types circular sliding failure, plane sliding failure and wedge sliding failure, some studies have. Toppling involves rotation of rock blocks or columns around a fixed point on its base. Dec 01, 2008 read improved analytical solution for toppling stability analysis of rock slopes, international journal of rock mechanics and mining sciences on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Process analysis of toppling failure on antidip rock slopes under seismic load in southwest china article pdf available in rock mechanics and rock engineering 524 may 2019 with 580 reads. Kinematic analysis is a method used to analyze the potential for the various modes of rock slope failures plane, wedge, toppling failures, that occur due to the presence of unfavorably oriented discontinuities figure 1. Toppling failure occurred in the slate slope in south anhui in china, which was consistent with field observations and the results reported in 30, 31. New stability calculation method for rock slopes subject. The angle between the failure plane and plane normal to discontinuities. The stabilisation of rock engineering structures by rockbolts. Stability analysis of rock slopes against blockflexure toppling. The discontinuous deformation analysis method proposed by genhua is a discrete one and has a significant advantage when simulating the.
The accompanying text to the youtube video is as follows. S canada rock mechanics symposium, san francisco, june 29july 2, a poster paper. The term toppling failure, as applied to rock slopes, was. According to the results of physical model tests and field investigations of antiinclined rock slopes, most real instabilities are of the sliding or flexuraltoppling type. Toosi technical university 4 types of failure in rock slope strength curve for the rock mass and relationship between slope height and angle modified from hoek and bray, 1981 toppling failure toppling failure when a block of rock resting on an inclined planes moving downward from the face of the slope. Nomograms for the assessment of toppling failure in rock slopes. Weathering of material and expansion and contraction associated with freezethaw cycles are principle causes of raveling. Pdf process analysis of toppling failure on antidip. State key laboratory of geomechanics and geotechnical engineering, institute of rock and soil mechanics, chinese academy of sciences, wuhan 430071, hubei, china. Next prev landslides in research, theory and practice. In order to clarify mechanism of toppling failure in rock slopes and evaluation on seismic stability, 2d joint elements around each rock column is proposed to simulate the discontinuity of rock slope, which is different from goodman joint and composed with normal spring k n and shear spring k s without volume. Physical and theoretical modeling of rock slopes against. Landslide can result either from rock failure or soil failure. Toppling failures can occur in slopes cut in rock with regularly spaced.
A transfer coefficient method is developed based on goodman and brays kinematic model, by introducing two parameters. This classic handbook deals with the geotechnical problems of rock slope design. Toppling failures occur in rock masses containing a set of discontinuities that strike nearly parallel to the slope and dip into the slope, and these failures have been observed in both natural and manmade slopes. Stability analysis of rock slopes against sliding or. The insitu rock structural weaknesses, referred to herein as geostructural defects, such as naturally induced microcracks, are extremely responsive to tensile stresses. Sliding occurs due to a translation movement of a rock block or a rock mass along a plane failure surface. Failure of a brittle rock point when the rock loses all resistance to stress and crumbles. These complex mechanisms can follow overall curved paths that can be similar to those encountered in soils. Rock mechanics studies to analyse toppling failure open pdf. Abstract three case histories of toppling failures of rock slopes, and the. Since the rock slope has toppling failure potential, this load will contribute to the toppling failure. According to the results of physical model tests and field investigations of antiinclined rock slopes, most real instabilities are of the sliding or flexural toppling type. An analytical solution for block toppling failure of rock. Rock slope stability analysis ubc eoas university of british.
Thus, the most important thing to keep in mind is that strong rock is strong, weak rock isnt our first goal is to capture the essential. The results indicated that the potential toppling mode created by discontinuities can lead to directflexural toppling failure. Scribd is the worlds largest social reading and publishing site. Results show that the nmm can be used to correctly calculate the toppling safety factor, simulate the failure process of slope toppling, and accurately model the whole failure process of rock slopes with many rock bridges. Numerical simulations of the creep characteristics of the structural plane of rock mass are very useful. Limit equilibrium analysis of toppling failure must therefore consider both the possibility of. Analysis of geostructural defects in flexural toppling failure. Rock slope stability analysis utilization of advanced. Failure often initiates at the slope toe, and the failure surface is usually multiplanar rather than planar. Slope failures are essentially natural hazards that occur in many areas over the world.
Wedge failure on two planar failure in rock in which a intersecting discontinuities with discontinuity daylights the a line of intersection which slope face daylights the slope figure 151 facing pages types of rock slope failures. Kinematic analyses of sliding and toppling failure of. Here the column of rock rotates about a fixed point at the base of the slope. Theoretical and numerical study on the blockflexure.
In the third failure, the top 8 m of a single 12 m high toppling block was removed by blasting to prevent further rotational movement. Feb 01, 2011 the insitu rock structural weaknesses, referred to herein as geostructural defects, such as naturally induced microcracks, are extremely responsive to tensile stresses. It could be that this is area of rock is failing in a spectacular fashion, generating the dust. In the present study, a threedimensional 3d dda method was. When is a rock engineering design acceptable introduction. However, most existing simulation methods are based on continuum mechanics and hence are unsuitable in the case of large displacements and deformations. Blockflexure is the most common mode of toppling failure in natural and excavated rock slopes. However, the shear failure occurred near the slope toe, the effects of the cohesion of the discontinuities on the stability of the slope, and the. Toppling failure involves rotation of jointed columns about pivot points.
When is a rock engineering design acceptable 6 during the construction of the mica and revelstoke dams on the columbia river in british columbia, canada, several potential slides were investigated. In such failure, some rock blocks break due to tensile stresses and some overturn under their own weights and then all of them topple together. According to the results of the physical model tests, the failure plane of an anaclinal layered rock slope was a lineartype plane at an angle above the plane normal to the discontinuities, and the failure mode of rock strata was bending tension. Nevertheless, it is difficult to make the quantitative evaluation of the mechanism and failure process of toppling in discontinuous rock slopes with such a method founded by continum mechanics, while the conventional numerical methods such as the finite element method fem and the boundary element method bem have been frequently used to. A solution is developed, based on a limit equilibrium approach, for analysing the toppling stability of rock slopes, which are characterized by blocks whose thickness is significantly smaller than the height of the block at the crest. Kinematic analyses of sliding and toppling failure of double free face rock mass slopes.
Blockflexure is the most common type of toppling failure in rock slopes. Pdf probabilistic stability analysis of block toppling. Flexural toppling failure occurs by tensile stress caused by the moment due to the weight of the inclined superimposed cantileverlike rock columns. While discrete element models may give some indication of the overall mechanics of this type of slope deformation, there is no way in which a factor. Plane failure a rock slope undergoes this mode of failure when combinations of discontinuities in the rock mass form blocks or wedges within the rock which are free to move. Development of a quantitative model for the mechanism of raveling failure in highway rock slopes using lidar 5. It is commonly referred that the failure modes in rock slopes are sliding and toppling. As a discrete numerical method, discontinuous deformation analysis dda is wellsuited for simulating the movement process, contact transformation, and large displacement and deformation of rock block systems, which are formed in jointed rock masses. This type of slope failure may be further categorized depend on the mode such as. Stability analysis of slopes against combined circular. Introduction toppling failures can occur in slopes cut in rock with regularly spaced fractures which strike parallel to the slope, and dip into the face. May 18, 2017 toppling is a mode of failure that may occur in a wide range of layered rock strata in rock slopes. Analytical study on blockflexure toppling failure of rock slopes subjected to seismic loads.
This toppling action is due to the columns center of gravity lying outside the base dimensions. Probabilistic analysis of toppling failure in rock slopes. What is the response of rocks under dynamic earthquake type loading. Lectures on rock mechanicslectures on rock mechanics.
Stability analysis of rock slopes against sliding or flexural. Pdf process analysis of toppling failure on antidip rock slopes. Apr 25, 2017 the removal of overburden and the confining rock, as is the case in mining excavations, can result in a partial relief of the constraining stresses within the rock structure, resulting in a toppling failure. Toppling and columnar flexural bending or buckling are other failure mechanisms that can occur with increasing slope scale. What is the bearing capacity of rock on surface an at depths. Improved analytical solution for toppling stability. Improved analytical solution for toppling stability analysis. A common block toppling mode is adopted for analysing toppling stability of rock slopes.
Analytical study on blockflexure toppling failure of rock. Variation of failure mechanisms of slopes in jointed rock. An optimization of the analytical method for determining. Analysis of geostructural defects in flexural toppling. An optimization of the analytical method for determining the.
Rock mechanics studies to analyse toppling failure authors. Theoretical and numerical study on the blockflexure toppling. Discontinuities are geologic breaks such as joints, faults, bedding planes, foliation, and shear zones that can. Development of a quantitative model for the mechanism of. Toppling is a representative failure mode of discontinuitycontrolled rock slopes. Manual em 111021902, department of the army, corps of engineers, washington, dc. This toppling action is due to the columns center of gravity lying outside. Types of slope failures there are main four types of failures which are. Toppling failure of rock slopes can be roughly differentiated into three. The method is general in form and is applicable to a range of discontinuity geometries. On the other hand, topplingsliding failure can occur in. In this study, the determination of the transition position from toppling. Rock slope engineering civil engineering i am menglim. Stability of rock slopes, modes of failure, plane failure, wedge failure, circular failure, toppling failure.
Nonassociative limit analysis of the topplingsliding failure of rock slopes ahmed faysal a. Thus, by increasing the normal force across a shear surface by adding tensioned rock bolts. Surface toppling can cause rock falls, but deep toppling seldom fails suddenly. Pdf toppling failure is one of the most common modes of failure of rock slopes in layered rock. Jun 19, 2015 rock mechanics studies to analyse toppling failure open pdf.
Failure mechanisms of toppling rock slopes using a three. Finally, a real case study is used for the practical verification of the suggested method. Mechanical model and analytical solution to toppling slope failure. The removal of overburden and the confining rock, as is the case in mining excavations, can result in a partial relief of the constraining stresses within the rock structure, resulting in a toppling failure. Rock mechanics problemsrock mechanics problems how will rock react when put to mens use.
So the entire slope has a combination of circulartoppling failure potential, as shown in fig. Using the proposed method developed in this paper, the final results were presented as follows. New stability calculation method for rock slopes subject to. Strength in plastic materials is defined as the level of stress at failure. Using solid mechanics and fracture mechanics approaches, the flexural toppling problems of rock slopes with geostructural defects were investigated by majdi and amini 2011. Finally, the topping failure of left bank of one high dam is simulated. Probabilistic analysis of rock slopes against block. Toppling failures involve slabs or columns of rock. Shear creep simulation of structural plane of rock mass. In the first stage, due to rock columns deformation, soil mass moves slightly and enters into an active mode. It has been written for the nonspecialist mining or civil engineer, with worked examples, design charts, coverage of more detailed analytical methods, and of the collection and interpretation of geological and groundwater information and tests for the mechanical properties of rock. A new video has appeared on youtube showing a time lapse sequence of photographs of a toppling failure that occurred at 12. Introduction toppling failure is one of the most probable instabilities of layered rock slopes.
Then, the physical and mechanical properties of experimental. A study of the mechanism of flexural toppling failure of. Methods to improve rock mass responses, grouting in rocks, rock bolting, rock anchors. The mechanism of flexural toppling failure of jointed rock slopes has been investigated through a series of centrifuge experiments conducted on models manufactured from two types of materials brittle. Nonassociative limit analysis of the topplingsliding. Further, attempts have not been made to consider the in. The basal failure plane observed in the centrifuge models, has been found to emanate from the toe of the slope, and orient at an angle. In plastic material, specific point of failure difficult to identify because deformation continues indefinitely at a constant level of stress. Jul 18, 20 my immediate hypothesis would be that during the toppling failure the lower block is pivoting on a small area of rock and debris in this region, which as a result must be under huge compressive stress. Results show that the nmm can be used to correctly calculate the toppling safety factor, simulate the failure process of slope toppling, and accurately model the whole failure process of rock slopes with many rockbridges. In such failure, some rock blocks break due to tensile stresses. Popularly known as landslides, slope failures describe a wide variety of mechanisms that cause the outward or downward movement of slopeforming materials like rock, soil or landfills.
Zhang haina 1,2, chen congxin 1, zheng yun 1, zhou yichao 3, deng yangyang 1,2. In view of this, probabilistic analysis of a rock slope against toppling. Toppling is a mode of failure that may occur in a wide range of layered rock strata in rock slopes. Stability analysis of rock slopes against blockflexure toppling failure m amini, a majdi, ma veshadi rock mechanics and rock engineering 45 4, 519532, 2012. A study of the mechanism of flexural toppling failure of rock slopes. Pure toppling failure only occurs in very steep or overhanging slopes. This type of failure generally produces small rockfalls, not massive failures. Rock mechanics studies to analyse toppling failure. The stability of slopes and underground openings against flexural. Hence, geostructural defects that may naturally exist in rock columns are. A transfer coefficient method for rock slope toppling.
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