Stability of Rock Slopes along Raidah Escarpment Road, Asir Area, Kingdom of Saudi Arabia (original) (raw)
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Assessment of rockfall risk along roads
Natural Hazards and Earth System Sciences, 2004
This paper contains a method for the analysis of rockfall risk along roads and motorways. The method is derived from the Rockfall Hazard Rating System (RHRS) developed by Pierson et al. (1990) at the Oregon State Highway Division. The RHRS provides a rational way to make informed decisions on where and how to spend construction funds. Exponential scoring functions are used to represent the increases, respectively, in hazard and in vulnerability that are reflected in the nine categories forming the classification. The resulting total score contains the essential elements regarding the evaluation of the degree of the exposition to the risk along roads. In the modified method, the ratings for the categories "ditch effectiveness", "geologic characteristic", "volume of rockfall/block size", "climate and water circulation" and "rockfall history" have been rendered more easy and objective. The main modifications regard the introduction of Slope Mass Rating by Romana (1985, 1988, 1991) improving the estimate of the geologic characteristics, of the volume of the potentially unstable blocks and the underground water circulation. Other modifications regard the scoring for the categories "decision sight distance" and "road geometry". For these categories, the Italian National Council's standards (Consiglio Nazionale delle Ricerche-CNR) have been used (CNR, 1980). The method must be applied in both the traffic directions because the percentage of reduction in the decision sight distance greatly affects the results. An application of the modified method to a 2 km long section of the Sorrentine road (no 145) in Southern Italy was developed. A high traffic intensity affects the entire section of the road and rockfalls periodically cause casualties, as well as a large amount of damage and traffic interruptions. The method was applied to seven cross sections of slopes adjacent to the Sorrentine road. For these slopes, the analysis shows that the risk is unacceptable and it should be reduced using urgent remedial works.
The stability of road cut cliff face along SH-121: a case study
Natural Hazards, 2013
Rockfall is one of the major concerns along highways, settlements and forests around the globe. Amboli road cut hill is one such region which is highly vulnerable and suffers from recurrent rockfall mostly in the rainy season, which blocks the State Highway 121 for considerable period of time. The steep and highly jointed slope along the road makes the zone prone to failure due to rainwater action. This road experiences heavy traffic throughout the year as it is the only road connecting Goa to Satara and Kolhapur via Sawantwadi in Maharashtra State, India. Therefore, an attempt has been made in this study to understand the stability of the cliff face. A combination of field study and 2D computer simulation was performed to assess surface characteristics of the cliff face. Bounce height, translational kinetic energy, translational velocity and factor of safety for saturated condition have been estimated. The result of this study shows that the rock face is highly unstable taking into consideration the environmental condition and daily traffic. Proper preventive measures have also been suggested to arrest the movement of falling rocks before reaching the roads or valleys. It is a belief that if proper care is taken, then further uncertain rockfall hazards can be prevented. Keywords Rockfall Á Finite element method Á Bounce height Á Coefficient of restitution 1 Introduction Slope instability is the most critical hazard in hilly areas. It includes lateral spread, topple, creep, rotational landslides, translational landslides and rockfall (Highland and Bobrowsky 2008). Rockfall is one of the most significant geological hazards in high mountainous region, but relatively fewer studies have been carried out to investigate them along highway road cuts, particularly in Amboli hills of Sahyadri region, Maharashtra, India.
Investigation of rockfall-prone road cut slope near Lengpui Airport, Mizoram, India
Journal of Rock Mechanics and Geotechnical Engineering, 2018
Rockfall is one of severe natural hazards that are frequently reported in northeast region of India. It carries rock block falling from the cliff with high velocities and energies which can result in damages to vehicles, disruption to transportation, injuries and fatalities. The massive rockfall event which occurred in April 2017 on the highway NH-44A, near Lengpui Airport, blocked the traffic for 1 d, and fortunately, no casualties were reported as the event occurred in the night. This is the only highway connecting the Aizawl city to the airport and the region is highly prone to rockfall events. Hence assessment of rockfall along this highway is necessary. In the current study, rockfall hazard assessment has been carried out on three locations by rockfall hazard rating system (RHRS). During pre-failure analysis, the result shows that most hazardous slopes have RHRS score of 639. The slopes were found to be vulnerable and later on the rockfall activity occurred. Three-dimensional (3D) stability analysis has been carried out using 3DEC software package to analyze the failure behavior and to decide the rockfall-prone zone (unstable blocks) for slope. The total displacement of 2.24 cm and velocity of 2.25 mm/s of the failed block have been observed in the numerical analysis. Further, the rockfall vulnerable zone (unstable blocks) is considered to determine the parameters such as run-out distance, bounce height and energies of the falling rock blocks. The maximum total kinetic energy of 5047 kJ has been observed in the numerical analysis with the maximum run-out distance up to 18 m.
An inventory for evaluating hazard and risk assessment of cut slopes in weak rocks along highways
Bulletin of the International Association of Engineering Geology, 1997
Several cases of instability of cut slopes along major highways in Jordan were reviewed in this study, in some detail. Emphasis was placed on the Amman-Irbid highway with the aim of establishing a wider data base of case studies and examining all possible mechanisms and factors influencing stability. The study showed that major cut slope failures were caused by the presence of weak cohesive layers (mainly clayey marl) interbedded within other, mostly stronger, formations, in addition to the steep cutting angles and unfavourable dip of strata combined with relatively high piezometric surface brought about by poor surface and subsurface drainage.
Assessment of Rockfall Hazard along the Road Cut Slopes of State Highway-72, Maharashtra, India
2013
Rockfall is a major problem in high hill slopes and rocky mountainous regions and construction of highways at these rockfall prone areas often require stable slopes. The causes of rockfall are presence of discontinuities, high angle cut slopes, heavy rainfall, and unplanned slope geometry etc. Slope geometry is one of the most triggering parameters for rockfall, when there are variations in slope angle along the profile of slope. The Present study involves rockfall hazard assessment of road cut slopes for 15 km distance starting from Mahabaleshwar town along State Highway-72 (SH-72). The vertical to sub-vertical cut slopes are prone to instability due to unfavorable orientation of discontinuities in slope face of weathered and altered basaltic rockmass. The predominant type of instability has been found as wedge type failure involving medium to large size blocks. In order to investigate the existing stability conditions, analyses were carried out at two locations under different slope conditions. The kinematic analysis was performed using stereographic projection method. RockFall 4.0 numerical simulator software was used to calculate the maximum bounce heights, total kinetic energies and translational velocities of the falling rockmass blocks, and a comparative analysis is presented with increasing the mass of blocks and height of the slope. The result of numerical analysis shows that varying slope angle geometry creates more problems as compared to the mass of blocks in the scenario of rockfall.
Arabian Journal of Geosciences, 2014
A rock fall hazard rating study was conducted along the roads of Fayfa Mountain in the Kingdom of Saudi Arabia to determine hazardous zones and to specify remediation and/or mitigation measures to improve the safety of the steep mountain roads. The mountain consists mainly of a weathered and/or fractured syenite core draped with slate, phylitic, and amphibolite rocks around the lower periphery of the mountain. Overall slopes on this mountain have an average range between 38 and 45°, with rock cuts typically 30-40-m high in places. High-value properties dot these mountain roads, and when roads are closed because of rock fall, there is significant personal and economic disruption in the area. This study was concluded in 2011, and rock fall hazards were indentified and classified according to relative hazard (likelihood of rock fall) and relative consequence (consequence of rock fall). For this purpose, the Saudi Arabia Rock Fall Hazard Rating System was developed based on existing rating systems. In addition, remediation and mitigation measures were prescribed for each identified hazardous section. Specified solutions were geared to minimize cost and to make use of local expertise and available equipment. The suggested remediation solutions are scaling of loose rock (both manual and mechanical), mechanically reshaping the slope (to remove overhangs and remove protrusions that serve to increase the horizontal velocity of bouncing and rolling rock), increasing the ditch capacity by deepening and widening the ditch (often by cutting back the lower portion of the slope), or by installing jersey barriers on the down gradient side of the ditch, using locally built stone retaining walls to stabilize the lower section of slopes and using gabion and large block barriers to stabilize small debris flow channels. In a small number of cuts, trim blasting and creating benches were specified. Some solutions were not considered due to high cost or due to the concern that local contractors could not implement them effectively. These included anchoring systems, advanced walls such as sheet pile and anchored retaining walls, draped mesh, and sacrificial fences.
Transportation corridors in a great deal of regions are often liable to undergo rockfalls, which cause a major hazard for motorists as well as a large amount of damage and injuries. Over the last two decades, several qualitative and quantitative risk procedures have been proposed in order to reduce the potential consequences of rockfalls. Generally, qualitative methods use crude exponential scoring patterns, and the total score reflecting the risk derives from the summation of scores of factors of different categories, such as: the slope height, ditch effectiveness, traffic, geological characteristics, failure magnitude and consequence. In quantitative approaches, the exposure to risk is given by the annual probability of rockfall failure, the vehicle being spatially in the path of the event when it occurs, the vehicle being temporally in the path of the event when it occurs and one or more occupants of the vehicle being killed as a result. The quantitative risk assessment is an ess...
Evaluation of Rockfall Hazard Along Brazil Roads
The Brazilian road network is constructed in a highly heterogeneous geological environment and some stretches cross through discontinuous rock masses that have uncertain or even ignored geotechnical characteristics. Rock slopes are potentially unstable surfaces and as such are susceptible to rockfalls that affect the highway's user safety, transportation infrastructure and surrounding environment. The geomechanical behavior of rock masses and also the geometric and traffic conditions of highways are fundamental aspects of rockfall evaluation. This research presents a case study of rockfall evaluation for slopes bordering highway sections, aiming to classify them and determine a hierarchy for intervention, based on defined criteria. The presented method could be used as a first step in the study of stabilization techniques for problems caused by rockfalls from highway slopes. In order to use this approach, field investigations including geomechanical classification of rock mass are necessary. In this context, twelve slope sections containing rock slopes in Espirito Santo's road network were investigated. The slopes were analyzed individually and the influence of each parameter in the global rating was evaluated. Parameter effectiveness in the proposed method was also evaluated. The slopes were classified to define priority measures to minimize roadway problems in each place.
Rockfall hazard management on traffic facilities in Croatia
Along the Croatian side of the Adriatic Coast some large rockfall on the steep limestone slopes occurred during last decade and caused serious damage on buildings and traffic facilities with injured persons. The main reasons for rockfall in limestone slopes near railways and roads occurring are unfavorable rock mass characteristics, rock mass weathering in combination with heavy rainfalls so as men influence during the facility constructions. The applied technologies of the slopes construction were very conservative and attained safety factors are very low. The technologies of rockfall protections during construction of the new roads in the last decades are significantly improved. The rockfall protection started with using of netting techniques with very low quality of the wire material. After some time, the double twisted netting with galvanic protection occurred as the most common type of the rockfall slope protection. On the more demanding slopes the shotcrete was used and still is regarding the quality of the rock mass in the slope that is needed to be protected. The new technologies are applied throughout construction of the support system including high load bearing meshes with reinforced geotechnical self-drilled anchors in combination with high performance rockfall barriers. After rockfall phenomena occurring on some particular locations, the projects of rockfall protection were conducted to ensure human lives and facilities from further rockfall occurrences. The process of rockfall protection started with rockfall hazard analyses to identify potential of rockfall occurrence so as possible accidental consequences, e.g. rockfall risk. On locations where hazard with related risk was determined the detailed field investigations were provided. Based on identified characteristics of possible unstable rock mass blocks analyses of motion and resulting paths were conducted. Trajectories, impact energy and height of bouncing are depending of slope geometry, slope surface roughness and rockfall block characteristics. Depending on these analyses rockfall protection measures were designed. Two design approaches were adopted, prevention of rockfall by removing of potentially unstable rock mass or by rock mass support system installation and by suspending of running rock fall mass with rockfall protection barriers. In this paper we will present experiences on rock fall hazard determination and rockfall protection design so as installation of rock fall system protection on some location on limestone slopes near the traffic facilities in Croatia.