Road Cut Slopes Research Articles

Stability and sensitivity analysis of Himalayan road cut debris slopes: an investigation along NH-58, India

The complex geological environment due to active tectonics and varied lithology with multiple phases of deformation and metamorphism led to a rugged topography and large destabilization of slopes in the Himalayan region. However, the ever-rising activities due to various ongoing developmental and urbanization processes in the region are contributing to instability of slopes. The significant number of causalities and massive economic loss is deliberately endangering Himalayan ecosystem due to landslide-related phenomena. Transportation corridors within Himalayan terrain experience frequent landslides, particularly the sections manifested by debris slopes. From several decades, the national highway-58, in Uttarakhand, Himalayas, has been endangered due to diverse and incessant slope failures. The present investigation demonstrates the stability appraisal along the strategic transportation corridor. These studies incorporate the various issues and causes pertaining to debris slides from Rishikesh to Devprayag, Uttarakhand. The numerical simulation assessment was undertaken by deterministic and sensitivity analyses by conventional limit equilibrium methods which is being augmented by much advanced and robust finite element tool. Factor of safety for each slope was determined, and correspondingly, best efficient slope stabilization remedies were proposed to enhance the stability of slopes. It is recommended that such strategic slope stability assessment should be performed within different vulnerable sections of the Himalayas and likewise regions for fruitful and sustainable step toward disaster mitigation.

A BBO-based algorithm for slope stability analysis by locating critical failure surface

Determination of the critical failure surface is performed in stability evaluation process for road cut slope, embankments, dam, excavations, retaining walls and many more. Finding the critical failure surface in a rock or soil slope is very cumbersome and becomes a difficult constrained global optimization problem. Due to existence of discontinuous function and strong multiple local minima points, researchers are facing difficulties to employ trial-and-error methods in a large search space. Thus, classical optimization techniques fail to converge to a valid solution. In this study a stochastic method called biogeography-based optimization algorithm was adopted for analyzing the factor of safety. Based on the finding from the implementation and quantitative evaluation, it was found that the proposed method for locating critical failure surface in homogeneous soil slope acquires more efficient results over other implemented methods such as grid search and genetic algorithm. The validation and effectiveness of the proposed method are investigated by solving two benchmark case studies from the literature, while the simulation design for slip surfaces is carried out using ‘Rocscience slide’ software tool for comparing the results.

Reconstruction of extreme topography from UAV structure from motion photogrammetry

The development of unmanned aerial vehicle photogrammetry over the last decade has allowed terrain that is very difficult for humans to access to be captured at very high spatial and temporal resolutions. This paper deals with the application of this technique to the study of extreme topography in a near-vertical road cut-slope. Three photogrammetric projects were carried out: one derived from images taken with the camera oriented horizontally, one derived from images taken with the camera tilted at 45°, and one derived from both sets of images. Point clouds and orthophotos were generated for each of these projects. The best accuracies were achieved by the photogrammetric products derived from the combined images set, which had RMSE equal to 0.053 m, 0.070 m and 0.061 m in X, Y and Z direction, respectively. A software program was developed to generate contour lines and cross-sections derived from the point cloud, which was able to represent all terrain geometric characteristics, such as several Z coordinates for a given planimetric (X, Y) point. Furthermore, comparing the contour lines and cross-sections generated from the point cloud using the program developed in this project to those generated from the digital surface model showed that the former are capable of representing geometric terrain characteristics that the latter cannot.

Stability analysis of a recurring soil slope failure along NH-5, Himachal Himalaya, India

The repetitive soil slope failure along the National Highway (NH)-5 in Jhakri region of Himachal Pradesh, India draws frequent concern due to heavy damage and traffic disruption almost every year. Being only linking route from border district to the nearby land area, stability of the road-cut slopes along this highway is of major concern in regard to safe transportation. Absence of any previous stability investigation of this recurring slope failure calls for an integrated geotechnical and numerical approach in order to understand the instability factors. The geotechnical analysis has been performed to determine the inherent properties of soil materials which affect the stability of existing slope. An event-specific antecedent rainfall threshold has been suggested to quantify the relationship between rainfall and slope failure. A two-dimensional limit equilibrium method has also been executed to visualize the scenario of pre- and post-failure stability of the slope. On the basis of limit equilibrium analysis, it has been inferred that slope geometry is a major affecting parameter that influences the failure pattern. Moreover, preventive measures through benching and soil nailing have also been proposed and validated through limit equilibrium analysis for long-term stability and safe transportation.

Stability assessment of Himalayan road cut slopes along National Highway 58, India

Himalaya is one of the most tectonically and seismically active mountain chains in the world having complex geological and geotechnical conditions. The Himalayan region experiences frequent slope failure posed due to various natural and anthropogenic causes. Slope instability issues have consequent effects on the socio-economic development of the people and the region in a large scale. In the present study, stability analysis of vulnerable road cut slopes along NH-58 from Rishikesh to Devprayag in the Lesser Himalayas has been conducted. Critical slopes were identified by considering the geological and the geotechnical complexities within the region. Rock mass characterisation techniques have been employed for slope stability assessment. Rock mass rating (RMR), slope mass rating (SMR) and continuous slope mass rating (CSMR) methods have been applied to evaluate different stability levels of rock mass along the highway. Spatial variation of stability classes using RMR, SMR and CSMR techniques has been analysed on geographic information system (GIS) tool. Kinematic analysis technique was also employed to identify the different modes of structurally controlled failures in jointed rock mass. Accordingly remedial measures have been suggested to improve slope stability.

Numerical Simulation of a Road Cut Slope along SH-72, Mahableshwar, Maharashtra, India

Numerical Simulation of a Road Cut Slope along SH-72, Mahableshwar, Maharashtra, India

Effects of image orientation and ground control points distribution on unmanned aerial vehicle photogrammetry projects on a road cut slope

The morphology of road cut slopes, such as length and high slopes, is one of the most prevalent causes of landslides and terrain stability troubles. Digital elevation models (DEMs) and orthoimages are used for land management purposes. Two flights with different orientations with respect to the target surface were planned, and four photogrammetric projects were carried out during these flights to study the image orientation effects. Orthogonal images oriented to the cut slope with only sidelaps were compared to the classical vertical orientation, with sidelapping, endlapping, and both types of overlapping simultaneously. DEM and orthoimages obtained from the orthogonal project showed smaller errors than those obtained from the other three photogrammetric projects, with the first one being much easier to manage. One additional flight and six photogrammetric projects were used to establish an objective criterion to locate the three ground control points for georeferencing and rectification DEMs and orthoimages. All possible sources of errors were evaluated in the DEMs and orthoimages.

Geotechnical Characterization of Road Cut Hill Slope Forming Unconsolidated Geo-materials: A Case Study

Geotechnical characterization of the unconsolidated geo-materials (which are mainly soils) is one of the major concerns for geotechnical engineers, administration and city planners. Recently, large scale highway projects in hilly regions leads to increase the road cut hill slope (RCHS) frequency. The slope failure along these RCHS is an uninterrupted source of suffering for human habitants and keeping human life in danger. The stability of these cut slopes mainly depends upon the geotechnical characterization of slope forming geo-materials. The present study was carried out to evaluate the geotechnical properties of unconsolidated geo-materials (i.e. basaltic soils) of Malshej Ghat, located in Maharashtra, India. Malshej Ghat is one of the most vulnerable hilly region, composed of basaltic rock and soils of Deccan plateau and suffers frequent RCHS failures, which block the National Highway-222 very frequently. A number of tests such as natural moisture content (NMC), specific gravity, grain size analysis, Atterberg limits, compaction, unconfined compressive strength and triaxial compression test were conducted to evaluate the geotechnical properties of unconsolidated geo-materials. The result of these tests indicates that the soils collected from five representative locations show high variability in geotechnical properties. Thus, the parameters from one location are not sufficient for the characterization and analyses of complete section of RCHS. For the quantification and numerical modeling of the RCHS, the geotechnical parameters of each location needs to be analyzed scientifically.

Hazard assessment in rockfall-prone Himalayan slopes along National Highway-58, India: rating and simulation

A massive disaster occurred in June 2013 in Kedarnath, India, due to cloudburst and extremely heavy rain along the Chorabari glacier. The resulting flash floods further aggravated the instability of natural and hill cut slopes at different places on the downstream side. The village Rambara that existed in close proximity of Kedarnath was swept away under flow of debris and water. The immediate surrounding area, which housed over a hundred and fifty shops and hotels, was completely washed away leaving no trace of civilization. This calamity in Uttarakhand is considered as India’s worst natural disasters after the tsunami in December 2004. On the downstream of the affected areas lie other pilgrim destinations that witness innumerable footfalls every year. Investigation of the health of the slopes on the routes to these destinations is therefore very important to ensure minimal damage to humans and machinery. The Himalayan terrain is a tectonically active mountain belt, having a large number of unstable natural and road cut slopes. Such slopes with rugged topography lie in the high seismic vulnerability zone. Further, the instability is aggravated by natural and anthropogenic activities increasing at a rapid and uncontrollable rate. In the light of the Kedarnath tragedy, more advanced research is being conducted along the National Highways to monitor and prevent slope/structure failures. This study was conducted to evaluate the hazard potential along National Highway-58, near Saknidhar village of Devprayag district by analysing rockfall using hazard rating systems and numerical simulation. Rockfall hazard rating systems were applied to evaluate the conditions of the slopes and to identify the associated risks. Based on the field and laboratory analyses, the parameters required for numerical models were determined. The bounce height, roll-out distance, kinetic energy and speed of the detached blocks were determined by using a competent rockfall simulator. The results obtained were used to identify rockfall risk in the region. Optimization strategies were applied during investigation by modifying the slope angle, ditch width and ditch angle to assess the possibility of a hazard to occur in different scenarios. The simulation studies revealed that an increasing slope angle could significantly increase the kinetic energy of the rock blocks. However, an increase in the ditch angle and the ditch width reduces the energy of moving blocks. The maximum bounce height above the slope varied from 0.003 m to 0.8 m for 10-kg blocks, whereas the maximum velocity and the maximum kinetic energy under such circumstances were 7.882 m/s and 379.89 J, respectively. The barrier capacity was found to be 233.18 J for 10-kg falling blocks at a height of 10.02 m. From the optimization studies, it was found that the risk can be reduced by up to 13 % if the slope of 70° has a ditch angle of 15° while on a flat ditch, the maximum risk will be at an angle of 65°. If the ditch angle is increased, the vertical component of the falling blocks is more effective than that in case of a flat ditch. These optimization studies lay foundation for advanced research for mitigation of rockfall hazards in similar potential areas.

A Hybrid FEM–ANN Approach for Slope Instability Prediction

Assessment of slope stability is one of the most critical aspects for the life of a slope. In any slope vulnerability appraisal, Factor Of Safety (FOS) is the widely accepted index to understand, how close or far a slope from the failure. In this work, an attempt has been made to simulate a road cut slope in a landslide prone area in Rudrapryag, Uttarakhand, India which lies near Himalayan geodynamic mountain belt. A combination of Finite Element Method (FEM) and Artificial Neural Network (ANN) has been adopted to predict FOS of the slope. In ANN, a three layer, feed- forward back-propagation neural network with one input layer and one hidden layer with three neurons and one output layer has been considered and trained using datasets generated from numerical analysis of the slope and validated with new set of field slope data. Mean absolute percentage error estimated as 1.04 with coefficient of correlation between the FOS of FEM and ANN as 0.973, which indicates that the system is very vigorous and fast to predict FOS for any slope.

Automatic extraction of discontinuity orientation from rock mass surface 3D point cloud

This paper presents a new method for extracting discontinuity orientation automatically from rock mass surface 3D point cloud. The proposed method consists of four steps: (1) automatic grouping of discontinuity sets using an improved K-means clustering method, (2) discontinuity segmentation and optimization, (3) discontinuity plane fitting using Random Sample Consensus (RANSAC) method, and (4) coordinate transformation of discontinuity plane. The method is first validated by the point cloud of a small piece of a rock slope acquired by photogrammetry. The extracted discontinuity orientations are compared with measured ones in the field. Then it is applied to a publicly available LiDAR data of a road cut rock slope at Rockbench repository. The extracted discontinuity orientations are compared with the method proposed by Riquelme et al. (2014). The results show that the presented method is reliable and of high accuracy, and can meet the engineering needs.

Soil Erosion in Steep Road Cut Slopes in Palencia (Spain)

AbstractConstruction associated to land development, such as roads and railroads, promote severe land degradation. Cutslope sediment yield is one of the major pollutants on waters close to the road and railroad network. To estimate road impact, soil erosion (E), sediment yield (SY) and morphological evolution of a railroad cut in Palencia (Spain), were studied using erosion nails, during the periods 1998–1999, 1999–2000 and 2000–2010. Data from two sample plots were analyzed by an ANOVA for repeated measures. Slope morphological evolution was estimated using a cubic polynomial regression, while E and SY were calculated by integration. The top and the toe of the slope eroded and accumulated 0·5 m respectively, evolving into a concave/convex slope profile. The mean measured E was 220 Mg ha−1 y−1. SY was 31 Mg ha−1 y−1, ranging from 109 Mg ha−1 y−1 to 24 Mg ha−1 y−1. Sediment yield was 4·5 times higher during the first year, than in all subsequent years. Results showed a decreasing trend and a stabilization in E and SY rates. However, both rates remain high and critical over the analyzed time, with regards to soil formation, water protection, land degradation and infrastructure maintenance. Copyright © 2015 John Wiley & Sons, Ltd.

Analysis Gabion Works in Cut-slopes Characteristics and Scenic Preference

This study was carried out to assess the characteristics of gabion on road cut-slopes, and analyze the scenic view preference for the gabion in Korea. 97 gabion sites from road cut-slopes were selected and were classified into 10 application types of gabion. The classification types of gabion were mostly related to the erosion and collapse prevention across road cut-slope. Gabion work sites in this study were classified into 30 sites (31%) for below 10% gradient, followed by 31 sites (32%) for 11~30% gradient, 20 sites (21%) for 31~50% gradient, and 16 sites (16%) for 51~80% gradient. Gabion works were constructed mostly in low gradient than in high gradient. 34 gabion sites (35%) among 97 sites were not covered by vegetation and 52 gabion sites (54%) showed vegetation cover rates of 1~30%. On the scenic preference analysis, public groups understood that the scenic view of gabion in cutting slope can be improved by vegetation cover, whereas expert groups prefer to scenic view of gabion only. However, expert groups encouraged subsequently vegetation covering to improve scenic view during gabion works in cutting slope.

Effects of forest roads on the hydrological response of a small‐scale mountain watershed in Greece

AbstractThe effects of land use changes on the ecology and hydrology of natural watersheds have long been debated. However, less attention has been given to the hydrological effects of forest roads. Although less studied, several researchers have claimed that streamflow changes related to forest roads can cause a persistent and pervasive effect on hillslope hydrology and the functioning of the channel system. The main potential direct effects of forest roads on natural watersheds hydrologic response are runoff production on roads surfaces due to reduced infiltration rates, interruption of subsurface flow by road cutslopes and rapid transfer of the produced runoff to the stream network through roadside ditches. The aforementioned effects may significantly modify the total volume and timing of the hillslope flow to the stream network. This study uses detailed field data, spatial data, hydro‐meteorological records, as well as numerical simulation to investigate the effects of forest roads on the hydrological response of a small‐scale mountain experimental watershed, which is situated in the east side of Penteli Mountain, Attica, Greece. The results of this study highlight the possible effects of forest roads on the watersheds hydrological response that may significantly influence direct runoff depths and peak flow rates. It is demonstrated that these effects can be very important in permeable watersheds and that more emphasis should be given on the impact of roads on the watersheds hydrological response. Copyright © 2014 John Wiley & Sons, Ltd.

Assessment of Slope Instability and Risk Analysis of Road Cut Slopes in Lashotor Pass, Iran

Assessment of the stability of natural and artificial rock slopes is an important topic in the rock mechanics sciences. One of the most widely used methods for this purpose is the classification of the slope rock mass. In the recent decades, several rock slope classification systems are presented by many researchers. Each one of these rock mass classification systems uses different parameters and rating systems. These differences are due to the diversity of affecting parameters and the degree of influence on the rock slope stability. Another important point in rock slope stability is appraisal hazard and risk analysis. In the risk analysis, the degree of danger of rock slope instability is determined. The Lashotor pass is located in the Shiraz-Isfahan highway in Iran. Field surveys indicate that there are high potentialities of instability in the road cut slopes of the Lashotor pass. In the current paper, the stability of the rock slopes in the Lashotor pass is studied comprehensively with different classification methods. For risk analyses, we estimated dangerous area by use of the RocFall software. Furthermore, the dangers of falling rocks for the vehicles passing the Lashotor pass are estimated according to rockfall hazard rating system.

Stability investigation of road cut slope in basaltic rockmass, Mahabaleshwar, India

Slope failures along hill cut road slopes are the major nuisance for commuters and highway planners as they put the human lives at huge risk, coupled with immense monetary losses. Analysis of these vulnerable cut slopes entails the assessment and estimation of the suitable material strength input parameters to be used in the numerical models to accomplish a holistic stability examination. For the present study a 60 m high, basaltic and lateritic road cut hill slope in Mahabaleshwar, India, has been considered. A number of samples of both basalt and laterite, in their natural state were tested in the laboratory and the evaluated maximum, minimum and mean strength parameters were employed for the three cases in a distinct element numerical model. The Mohr-Coulomb failure criterion has been incorporated in the numerical model for the material as well as the joints. The numerical investigation offered the factor of safety and insights into the probable deformational mechanism for the three cases. Beside, several critical parameters have also been judged from the study viz., mode of failure, factor of safety, shear strain rate, displacement magnitudes etc. The result of this analysis shows that the studied section is prone to recurrent failures due to the capping of a substantially thick layer of weaker lateritic material above the high strength basaltic rock mass. External triggering mechanisms like heavy precipitation and earthquake may also accelerate the slope failure in this area. The study also suggests employing instant preventive measures to avert the further risk of damage.

Stability evaluation of road-cut slopes in the Lesser Himalaya of Uttarakhand, India: conventional and numerical approaches

The hilly terrains of Himalaya are among the most vulnerable of the regions of India due to natural hazards. Different kinds of landslides occur frequently in the tectonically and geodynamically active region of Himalaya. Transportation, public networks, and all kinds of socioeconomic activities that occur in the high hills of the Lesser Himalaya are entirely dependent upon the local road and highway network in this region. However, the stability of the slopes that have been cut to construct and/or widen roads and highways is a major concern in hilly regions. Unplanned excavations performed by blasting have resulted in these cut slopes that are on the verge of instability. Such slopes become vulnerable under the influence of factors such as heavy rainfall, seismic activity, dynamic loading, and/or various kinds of human intervention. Any kind of slope failure can lead to disruption of traffic, losses of property and lives, injuries, as well as environmental degradation. In the present study, a slope stability analysis was performed of road-cut slopes along about 20 km of NH-109 from Rudraprayag to Agastmuni in the state of Uttarakhand in India. Based on field observations and variations in geological and geotechnical conditions, five locations were chosen for detailed study, including a laboratory study and numerical analysis. The two-dimensional conventional limit equilibrium method and a numerical technique based on the finite element method were used to analyze the cut slopes. This comparative analysis of slope stability provided a deeper understanding of this issue. The results of the analyses performed using both methods aided in identifying potentially vulnerable slopes and enabled us to compare the two methods.

Rock mass assessment along the right bank of river Sutlej, Luhri, Himachal Pradesh, India

The study involves the characterization of rock mass along the right bank of river Sutlej, Luhri, Himachal Pradesh. This road connects to several important locations and therefore blockage due to slope failure may cause several problems. Lack of proper geotechnical/geological investigations has led to cutting of the natural hill slopes with improper design. The subsequent road cut slope has made this zone highly vulnerable and a threat to local commuters. The concerned area has varying lithology which are highly jointed and exposed all along the road cuts. The unrestrained slope in this zone is prone to recurrent failures due to high precipitation and seismicity, eventually causing loss of life and property. Therefore, the study helps in understanding the behaviour and mode of failure of the cut slope through geometrical relationship between structural discontinuities and surface topography. Several important parameters were determined to quantify the region based on available and widely used rockmass characterization techniques to develop a proper understanding. This will ultimately help in designing appropriate remedial measures to such vulnerable zones that will prevent further slope failure and resulting damage.

Modelling changes in suspended sediment from forest road surfaces in a coastal watershed of British Columbia

Erosion from logging road surfaces, cut slopes, banks, and ditches represents a chronic source of sediment input to streams that can degrade aquatic habitats. Road surface erosion is of particular concern because the magnitude of sediment generation when traffic levels are high can be large. Current models for predicting sediment production from roads require information on area-specific sediment delivery, which is not often available. Here, we developed a model to quantify suspended sediment concentrations (SSC) generated by forest roads surfaces under different conditions of use and density. This model is designed for a typical medium-size coastal watershed of British Columbia or the American Pacific Northwest, and was applied to the Chilliwack River watershed as a case study. The results illustrate that intensive use of forest roads combined with high road density can increase the number of extreme sedimentation events over a predetermined threshold. A comparison of the effects of road density and the level of road use suggests that the level of road use is more important than the road density for the generation of fine sediment from road surfaces. However, the model omits the impact of roads on mass movements in a watershed, which represent a major source of sediment in steep watersheds, so the effect of road density is likely more substantial than the model predicts. The model is an attempt to overcome field data limitations by using an empirical relation between SSC and traffic variables, and presents a starting point for more intensive field studies that could be used to validate it. Copyright © 2013 John Wiley & Sons, Ltd.

임도비탈면에 시공한 식생기반재돌망태의 침식방지 및 녹화효과 분석

이 연구는 식생기반재 돌망태의 침식억지효과 및 녹화효과를 분석하는데 있다. 이 연구를 통하여 얻은 결론은 다음과 같다. 조사기간 중 평균침식량을 분석해 본 결과, 침식량이 가장 많은 순으로 보면 곡선부에서의 일반돌망태시공지(5,840 <TEX>$cm^3$</TEX>)>대조구(5,833 <TEX>$cm^3$</TEX>)>직선부의 일반돌망태 시공지(5,621 <TEX>$cm^3$</TEX>)>곡선부의 식생기반재돌망태시공지(4,298 <TEX>$cm^3$</TEX>)> 직선부의 식생기반재돌망태시공지(4,117 <TEX>$cm^3$</TEX>)의 순으로 나타나 식생기반재 돌망태를 시공한 것이 임도절토비탈면의 침식을 저감하는데 효과적인 것으로 분석되었다. 아울러 임도 곡선부의 식생기반재돌망태 및 일반돌망태시공지의 토양침식억지효과가 직선부보다 낮게 나타나 이러한 구조물은 곡선부보다는 직선부에 설치하는 것이 효과적일 것으로 사료된다. 조사기간 중 평균식생피복률은 곡선부에서 45(28~65)%로 나타나 동일한 기간 직선부 식생기반재돌망태시공지의 평균피복률 56(30~85)% 보다 약 11(2~20)% 낮은 값을 나타내어 직선부에서의 식생피복률이 높게 나타났다. 또한 임도절토비탈면에 시공한 식생기반재돌망태는 안정화된 이후 임도 절토 비탈면의 토양침식을 억지하는 효과로 인해 식생피복률이 증가하는데 기여하는 것으로 분석되었다. Analysis of new approaches to achieve naturally good ecological potential of forest road cut-slope by making the best use of advantages of gabion systems with vegetation base materials to prevent slope failure and erosion, in the area with highly erodible soil. Existing gabion systems can be divided into monolithic and modular system and can be divided into ten subtypes according to the purpose of establishment and combination of other measures. As a result on the monitoring of erosion amount from forest road cut-slopes in the test applications, the order of erosion amount from largest to smallest is as follows: the curved road cut-slope site where normal gabion system was established 5,840 <TEX>$cm^3$</TEX>; the control site 5,833 <TEX>$cm^3$</TEX>; the straight road cut-slope site where normal gabion system was established 5,621 <TEX>$cm^3$</TEX>; the curved road cut-slope site where the new gabion system was established 4,298 <TEX>$cm^3$</TEX>; and the straight road cut-slope site where the new gabion system 4,117 <TEX>$cm^3$</TEX>. Therefore, the result shows that the new gabion system is more effective than the normal gabion system to reduce erosion amount from forest road cut-slopes. During the study period, vegetation coverages of the straight and curved road cut-slope site where the new gabion system was established were about 56(30~85)% and about 45(28~65)%, so average vegetation coverage of the sites where the new gabion systems was established was higher than the sites where the normal gabion systems was established. Therefore, it was concluded that the new gabion system can be more effective for cut-slope revegetation.