wedge failure in rock slopes

International Symposium on Stability of Rock Slopes in Open Pit Mining and Civil Engineering Ian de Bruyn _____ Page 560 Figure 2: 3-D illustration of wedge failure Other modes of failure common in hard rock slopes, such as planar and toppling failure, have not been analysed. Failure of a rock slope on one or two plane surfaces is the simplest but at the same time the most important type of sliding failure and forms the basis for the stability analysis of rock slopes. Types of Slope Failure. The wedge failure phe-nomena in a rock slope. The present work focuses on the study of the wedge failure, which occurs as sliding of a mass of rock on two intersecting planes, generally discontinuity planes. Overall stability is usually controlled by rock mass strength and structure, especially in large open pits. 4.2.2 The plane wedge failure occurs under gravity alone when a rock-mass rests on an lnclined geologiml discontlnuity, such as bedding/weakness plane that daylights into the free slope face that is 1-I-ff > WP [see Fig. Wedge Failure This kind of failure causes a rock mass to slide along two intersecting discontinuities. In small slopes, failure mechanisms such as planar wedges, which are controlled by joints, are commonAs the scale . x�b```f``z��U� �� @16�T' g�Cβb,ڜ�*q��?ӥ�L��6��h�y�.p�v-6��IP�Q�vf��D�9��T�y- �e9E��|�Y��J� b�[y��1�i�\��=�.#�69e"Pd�� ƀe ��x� The required criteria for wedge failure … failure, buckling failure and circular failure, are often observed. PDF | On Jun 20, 2008, Mohamed Fadlelmula and others published Reliability-Based Modeling of Wedge Failure in Rock Slopes | Find, read and cite all the research you need on ResearchGate 0000005398 00000 n The wedge failure analysis is based on satisfying the equilibrium conditions of the wedge. 0000038963 00000 n E-mail: Professor, Dept. (1972) A useful technique for estimating the stability of rock slopes when the rigid wedge sliding type of failure is expected. The stability of the rock wedge is controlled by: joint sets dip and dip direction, slope geometry and direction, external forces (including water pressure and earthquake) and rock and joints mechanical properties. 1). Wedges are defined by two intersecting discontinuity planes, the slope surface and an optional tension crack. The paper i ntroduces a series of guidelines for interpretation of the results of rock slopes. While performing kinematic analysis for wedge failure of rock slope in Dips 6.0 software (RocScience), it indicates region of secondary wedge failure envelop (marked by yellow by default). One of the structurally controlled modes of failure in jointed rock slopes is wedge failure. Translational slides in rock masses are dependent upon the spatial arrangement of the discontinuities within the mass and their relationship to the geometry of the slope. (20 marks) (d) Using the planar failure mode equation, calculate the required anchor bars to stabilize the entire rock slope to factor of safety 2. Imp Coll Sci Technol Rock Mech Res Rep 19: 1-10. The wedge failure had developed in a rock cut 21 m ( 7 O ft) high that had a face angle of 7 5 °. Block or wedge slides occur when a soil mass is shattered along joints, seams, fissures, and weak zones by forces emanating from adjacent soils. xref 45-03 Building 406 Of 202. <]>> Although, field observations may provide valuable clues the about It is more similar to translational failure but the difference is that translational failure only occurs in case of infinite slopes but wedge failure can occur in both infinite and finite slopes. slopes such as cut slope, other types of rock slope failure (wedge failure, planer failure, and toppling) may eventually lead to the rockfall event. Thus, the stability assessment method has to be capable of coping with this uncertainty. In many cases, spatially in vertical slopes or very steep slopes such as cut slope, other types of rock slope failure (wedge failure, planer failure, and toppling) may eventually lead to the rockfall event. A thermally induced wedging–ratcheting mechanism for slope stability is investigated using a large-scale physical model and using a three-dimensional version of the numerical Distinct Element Method (3DEC). The results of the stereographic projection show that wedge, plane and toppling Among these mechanisms, the wedge failure is one of the most common ways of failure in rock slopes. Basic Geometry of a Surface and a Rock Face 3D geometry of the evaluated rock slope (terrain) and excavation pit (rock face) is to be set up in a frame named “Geometry“. trailer This mode of failure needs the dip angle of at least one joint intersection to be greater than the angle of friction of the joint surface. In many cases, rock mass slope stability is controlled by discontinuities, which determine the most likely mechanism of failure, depending on joints and slope geometry. The only difference between the translational failure and the wedge failure is that translational failure only occurs in case of infinite slopes but wedge failure can occur in both infinite and finite slopes. 1. 0000001244 00000 n DUNCAN C. WYLLIE A wedge failure in a rock slope 21 m (70 ft) high was stabilized by unloading the top third of the failure, constructing a concrete wall to reinforce the … NOTE: Stability analyses of known failures can be used to help constrain parameter values such as friction angles, that can then be used in analyses of other slopes to help assess the potential of future rock slope failures. Introduction. Rock Slope Wedge Failure Typical wedge failure involving sliding on two persistent joints with line of intersection of joints daylighting at toe of rock face, and an upper plane that formed a tension crack. 0000001383 00000 n This type of failure occurs when there are fissures, joints, or weak soil layers in slope, or when a slope is made of two different materials. Toppling failure is one of the most common modes of failure of rock slopes in layered rock strata. increases more complex mechanisms such as step-path failuresand rotational shear failure , which Calculated factor of safety = 0.4. Among these mechanisms, the wedge failure is one of the most common ways of failure in rock slopes. The aim of the investigation is to determine the influence of the main … For rock slopes usually two free surfaces (lower outcrop and upper outcrop) are present, ﬁgure 2. of Civil and Agricultural Engineering, National Univ. The stability analyses of tetrahedral wedges in rock slopes are commonly conducted using the versatile sequential vectorial operations or stereographic projection methods. Fourth Geo-China International Conference. Failure of a slope along a weak zone of soil is called a translational slide (Figure 16.2a). Two arrangements are considered: Plane failure A wedge failure in a rock slope 21 m (70 ft) high was stabilized by unloading the top third of the failure, constructing a concrete wall to reinforce the toe, and installing tensioned rock anchors. 45-03 Building 406 Of 402. With this framework, this work presents a reliability assessment of wedge stability in rock slopes by random sets, considering the joints geometry and strength parameters as random uncertain variables. %PDF-1.3 %�� Eng Geol 202: 55-61 Figure 2 shows the wedge failure phenomena in a rock slope. This type of failure occurs when there are fissures, joints, or weak soil layers in slope, or when a slope is made of two different materials. Among these mechanisms, the wedge failure is one of the most common ways of failure in rock slopes. The site is located in a highly active seismic zone. A planar wedge can be defined by: • a sliding plane • the slope face • the upper ground surface • an optional tension crack as shown in the following figure. 0000004993 00000 n It is also known as block failure or plane failure. In this code only one mode that is plane wedge failure ls described (see Fig. joints, foliation surfaces, bedding planes or faults. 0000005569 00000 n IS 14448 (1997): Code of practice for reinforcement of rock slopes with plane wedge failure 2nd Quarter 2005 C over Story Figure 3. Wedge Failure Wedge failure can occur in rock mass with two or more sets of discontinuities whose lines of intersection are approximately perpendicular to the strike of the slope and dip towards the plane of the slope. Planar failure … The determination of representative values for the analysis is therefore crucial. Markland JT. Rock slope stability analyses are routinely performed and directed towards assessing the safe and functional design of excavated slopes (e.g. 0000000016 00000 n This paper presents an alternative approach using closed-form equations, for cases where the upper ground surface dips in the same direction as the slope face. The wedge failure is quite similar to a translational failure. Block or Wedge Slide. Translational Slide. Stability-charts-for-rock-slopes-based-on-the-Hoek-Brown-failure-criterion These failure modes pro-vide a basis for the formulation of limit state functions so the prob-lem of stability of individual wedges in rock slopes is considered. The movement of the failure body may occur in any several modes: translational sliding, rotational sliding, toppling, falling or a combination of modes. (2016) A method for assessing discontinuity poles for potential wedge sliding. Plane mode of failure generally occurs in slope formed by stratified sedimentary and meta-sedimentary rock formations. While performing kinematic analysis for wedge failure of rock slope in Dips 6.0 software (RocScience), it indicates region of secondary wedge failure envelop (marked by yellow by default). It happens that in some places rock slope failures were so heavy at one spot, and it took place on both sides of the road and blocked it (Fig. Stability Analysis of Rock Slopes with Plane and Wedge Failure by Means of a Pocket Calculator The limiting equilibrium methods for slopes under various conditions against wedge failure have been previously proposed by several investigators. The results indicated the potential for both planar … This type of failure is commonly seen in slopes of up to 20 or 30 m high in hard jointed rock masses. 0 It is believed that the study can enhance the way for stability analysis and monitoring of the potential failure of jointed rock slopes.Keywords: Wedge failure; Joint persistence; Groundwater; Rock … Natural events include failure due to flash flood, excessive seepage, pore pressure, seismic event, presence of weak discontinuities across the rock slope, shear zones, toe cutting of slope by meandering river leading to unstable slope due to change in slope geometry. Wedge Failure Wedge failure can occur in rock mass with two or more sets of discontinuities whose lines of intersection are approximately perpendicular to the strike of the slope and dip towards the plane of the slope. Because the rock mass behavior is significantly governed by the presence of joints or other discontinuities, several types of slope failure, such as plane failure, wedge failure, toppling failure, buckling failure and circular failure, are often observed. Major wedge failure in granite rock slope. This paper presents the results of the slope failure analyses from fracture distributions and their relation to tectonic activity; the analytical results have indicated that the phenomena of plane failure, wedge failure and toppling failure can occur at almost of the survey sites within the study area. This type of failure occurs when there are fissures, joints, or weak soil layers in slope, or when a slope is made of two different materials. 0000000656 00000 n 0000001203 00000 n From a rock slope design perspective, the most important characteristic of a discontinuity is its (a) Wedge failure on two Planar failure in rock in which a intersecting discontinuities with discontinuity 'daylights" the a line of intersection which slope face Rock slope stability analyses are routinely performed and directed towards assessing the safe and functional design of excavated slopes (e.g. 93 18 0000003821 00000 n Note: The application Rock Slope can evaluate a broken rock wall by a shear failure (rock slides) using a planar and/or a polygonal shear plane and a rock wedge. The stability of a particular rock slope is governed by three main engineering geologic factors, We will introduce a few types of slope failure that are common in soils. Recently, the factor of safety of rock slopes against the wedge failure … Random sets arise as a powerful tool to deal with uncertainty, even when limited information of inputs is available. Types of slope/ground failure 2 Planar failure 3 Wedge failure 4 Toppling failure 5 Circular failure 6 3 Controls for ground failure 7 Catch bunds 8 Exclusion zones 9 4 Design of benches and faces 10 ... is weak rock, bedding, joints, structures, blast damage, vehicle vibrations, Because the rock mass behavior is significantly governed by the presence of joints or other discontinuities, several types of slope failure, such as plane failure, wedge failure, toppling failure, buckling failure and circular failure, are often observed. It can be improved by providing a berm below the … [22] Smith JV. Circular failure generally is observed in slope of soil, mine dump, weak rock and highly jointed rock mass. Dilatancy in a rock mass is unconstrained near slopes as normal stress on joints is small due to weight of the wedge. Plane failure; Wedge failure. Therefore, the failure of a rock mass occurs partially along joints and partially in non-jointed portions, such as in solid rocks, but in massive rocks, it occurs entirely in solid rocks. However, due to the geological origin of rock masses, these inputs are uncertain. Overall stability is always checked for the possibility of deep-seated failure through the rock mass and the method of slices is usually the tool of choice. and rock strengths are the factors controlling failure through the rock mass. 0000005774 00000 n 0000008177 00000 n CHAPTER 5.0: CIRCULAR FAILURE ANALYSIS . The analysis technique chosen depends on both site The toe of the cut was within 6 m (20 ft) of the railway, so even a minor slope failure could reach the track. The limiting equilibrium methods for slopes under various conditions against wedge failure have been previously proposed by several investigators. Wedge Failure Wedge failure, also known as block failure or plane failure, generates a failure plane that is inclined. 4). of Civil and Agricultural Engineering, National Univ. The proposed techniques arguably result in an improved level of confidence in the design of rock slopes susceptible to wedge failure. ); can analyse factor of safety sensitivity to changes in slope g eometry and material properties; more Abstract: The failure mechanisms of hard rock slopes are usually dominated by the joint and fault system of the rock mass, the properties of which show an inherent spread. 0000002658 00000 n (10 marks) (c) Calculate the factor of safety for wedge failure mode using the formula in Figure Q1(e) when the rock slope is in wet conditions (the student must demonstrate its calculation). 5.1 Introduction . Translational slip in rock slopes. In rock slopes the potential failure bodies are usually (but not necessarily) bounded by discontinuities i.e. In rock slopes plane, wedge, toppling and rock fall are common modes of failures (Tang et al., 2016, Lee and Wang, 2011, Yoon et al., 2002, Hoek and Bray, 1981, Hocking, 1976). The design of such slopes can sometimes be based upon an analysis of simple wedge failure. The rock type was a very competent, massive granite Slope stability in mining and civil engineering projects is always a problem of great concern. 1. The analysis and design of rock slopes susceptible to wedge failure is of interest to both civil and mining engineering. and/or the equilibrium conditions of natural slopes. %%EOF 0000024197 00000 n Failure of a rock slope on one or two plane surfaces is the simplest but at the same time the most important type of sliding failure and forms the basis for the stability analysis of rock slopes. If sliding distance of rock block or rock mass that detached by sliding, toppling, or falling was negligible to descending distance through air, it is dened as open pit mining, road cuts, etc.) Wedges are defined by two intersecting discontinuity planes, the slope surface and an optional tension crack. In d l d k l f l ll d d a moderately jointed rock mass, slope failure is generally dictated directly by the presence of discontinuities, which act as planes of weakness within the rock mass. Daylighting sheet joint with large perched block in grade III zone or granite rock slope 23 to contend with different geological features or instability problems. Slope stability in mining and civil engineering projects is always a problem of great concern. ��.�9�rWȅ̦�@�s-��q��(E�P�� E�ä�g��A�10it`� 820�i~ V�(1�1ȰM. The stability assessment according to block theory on the contrary follows a deterministic procedure. KEYWORDS Static and seismic slope stability analysis confirmed the global stability of the slope. SWedge is a quick, interactive and simple-to-use analysis tool for evaluating the geometry and stability of surface wedges in rock slopes. An extract from Stability Analysis of Rock Slopes for Plane & Wedge Failure with the Aid of a programmable Pocket Calculator, K. Kovari and P. Fritz, Federal Institute of Technology Zurich, Switzerland Institute of Highways and Underground Structures, Department of Rock Mechanics, 10 pgs. " the study of the wedge failure, which occurs as sliding of a mass of rock on two intersecting planes, generally discontinuity planes. ¶The stability of slopes during and after excavation is always of great concern in the field of rock engineering. 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