Terms Of Slope Stability Research Articles

SLOPE STABILITY COEFFICIENT CALCULATION OF THE KOK-TOBE MOUNT WITH CONSIDERING SEISMIC ACTIVITY USING GEO5 PROGRAM

Modern dangerous signs are manifested in the nature of the most significant components of engineering and geological conditions, ensured by the safety of people's life, the features of industrial and abrupt construction in mountainous and foothill areas, and, consequently, in conditions of sustainable economic development. In the event of serious development processes, serious difficulties arise for the construction and use of various engineering measures that require ensuring the safety of the population and taking measures to prevent and protect the population. During the design of anti-landslide measures, when erecting structures on unstable slopes or when distributing mechanisms on slopes and sides of ravines, works must begin with assessment stability degree of the inclined earth surface. Such assessment is made by calculating the slope stability coefficient, which is characterized by the ratio of the holding forces to the shear forces of the soil mass on an inclined surface. The paper presents the results of research in Almaty city on the experimental site on the slope of mountain Kok-Tobe. The article presents calculations of slope stability coefficient in "GEO5" program, in the natural state and taking into account seismic impact. As result of the calculation, unfavorable factors and risks in terms of slope stability are identified and recommended measures are also given.

A Study on the Influence of Vegetation Growth on Slope Stability

Vegetation plays a major role in terms of slope stability. Roots of grass and trees can increase the strength properties of soil which improves the stability of slope. A natural slope consists of grass and infinite number of trees inclined in different directions along with inclined roots. The aim of the paper is to study the effects of vegetation growth on slope stability for different root reinforced soil depth by varying tree inclination (along with roots), root spread and tree spacing for different slope geometry. The study involves determination of safety factor (FOS) of natural slope existing with and without vegetation growth (such as only grass, grass and trees). GeoStudio Slope/w software with limit equilibrium method was used for stability analysis of different slope inclinations. A tree was modelled as a point load and its roots were represented as reinforced soil properties with anchors and only as root reinforced soil. When compared to the bare slope, it was observed that there was an increase in FOS of slope on both the models of vegetation. Variations in FOS by varying root reinforced soil depth, tree inclinations and spacings were reported for different slope geometry and compared. Considering all these parameters, an empirical corelation for computation of vegetation influenced FOS has been developed. This study provides a mechanical accountability of vegetation cover on the stability of slopes.

Cut slope stability assessment along forest roads using the limit equilibrium approaches and Slide software

Calculating the factor of safety (FS) as slope stability factor is necessary to prevent environmental damage. Therefore, this paper aims to (i) calculate FS using the limit equilibrium approaches and Slide software and (ii) investigate the stability of slopes according to calculated FS (Janbu and Bishop methods) and status of different sites in the study area (Hyrcanian forest of Iran). Six landslides were selected along the forest road by a field survey. Landslide dimensions including length, width, and height were measured using meters. Slope gradients were measured using the Suunto clinometer. The Slide software was used to evaluate the stability analysis of slopes. According to laboratory tests on soil samples the average of the liquid limit was recorded as 58%. The results of the direct shear test showed that the rate of soil cohesion (c) and coefficient of friction angle (φ) decreased with an increase in moisture content. According to the results, the factors of safety for landslide sites (Sites 1–6) were calculated to be 1.3, 0.65, 0.76, 0.55, 1.19 and 1.51, respectively. These calculated FS can accurately determine the slope status in terms of slope stability. According to the software classification, the status of Site 1 is “susceptible to landside”. Sites 2, 3 and 4 are “very high risk”. Also, the status of Sites 5 and 6 are “high risk” and “stable”, respectively. The instability of the slopes in studied sites is related to the drainage system (lack of culverts or ditches) as well as marlstone as bedrock. According to the calculated FS in different sites and comparison of the obtained results with the real conditions of sites, it can be concluded that the slope stability analysis in the Slide software is very accurate and it can be used to determine the factor of safety under different conditions in terms of morphology, hydrology and soil mechanics.

The Evolution of the Area Between Valea Chintăului and Valea Caldă Following the Works Mitigating Soil Erosion

"The Evolution of the Area between Valea Chintăului and Valea Caldă Following the Works Mitigating Soil Erosion. The study area is located on the left slope of the Someșul Mic River, in the northern part of Cluj-Napoca and is bounded on the north and east by the watershed that separates it from the Valea Caldă River basin, south of the agricultural road that separates the slope from Someșul Mic floodplain and west of the orchard border. The area is called Sfântu Gheorghe Hill, the homonymous peak bordering it to the west, and Țigla Hill to the east. In 1986, the Institute for Studies and Design for Land Improvements implemented a plan to mitigate soil erosion on an area of 600 hectares within the mentioned limits. Of these, 300 hectares represented the arrangement of terraces, 200 hectares the arrangement of landslides and 100 hectares of drainage on slopes. The execution of the works mitigating soil erosion aimed at reducing the annual soil losses, the possibility of applying appropriate agrotechniques in the fruit plantations to be established. The arrangement of the slippery surfaces was done by modeling, eliminating the excess moisture, terracing, grassing or planting and had the purpose of bringing significant areas of land back in the economic circuit. Elimination of excessive water through drains was made for the proper development of future tree plantations. The purpose of this study is to analyze the temporal evolution, over a period of 30 years, of the efficiency of the arrangement works on the slope performed in 1986, first of all. The estimation of the effectiveness of the works executed at that moment was made by the comparative morphometric and morphological analysis of the landslides and the forms of deep erosion on the slopes. Second, the study examines the vulnerability of landslide risk factors in this area, in particular residential and public buildings, road infrastructure and agricultural land. The study starts from the following premises: the geomorphology of the southern slope of Sfântu Gheorghe Hill has been studied over time, as attested by bibliographical sources; 30 years ago, the destination of the lands related to the area was mainly agricultural, and the land use plans included mainly measures for agricultural development; in recent years, there has been an accelerated expansion of Cluj-Napoca, including on the northern slope of Someșul Mic, both from the base of the slope to the watershed, and along the base of the slope, to the eastern outskirts of the city. The questions that arise are: how did the landslides evolve and how did the slope evolve after the development carried out in 1986? How many of the built elements are located in areas with acceptable risk and how many are located in areas with high risk in terms of slope stability? Keywords: landscaping, soil erosion, landslides, torrents, terraces, modeling, vulnerability. "

Stability of Geogrid Reinforced Embankment on Soft Clay

The reinforcement by geotextiles or geogrids helps to improve the embankment stability and guarantee more uniform settlement. The factors effect on the stability of the reinforced embankment on soft clay, in terms of slope stability and sliding resistance has been studied using a finite element program (GEO5 program). In this paper, the effect of geogrid Spacing, the height of the first geogrid layer, unit weight of embankment fill, and the angle of internal friction was studied. The numerical model results indicated that the optimum spacing between the geogrid layers is 0.5 m. Increasing the angle of internal friction for the embankment fill causes to increase the factors of safety. Increasing the density of the embankment fill causes to decrease the factors of safety. Also, it was recommended to install the first geogrid layer between the embankment base and underlying soft clay layer without any vertical distance.

GEOTECHNICAL CHARACTERIZATION AND RISK ANALYSIS OF URBAN SLOPE INSTABILITY IN THE CITY OF ARACAJU - BRAZIL

This paper presents a risk analysis of mass movements in 16 slopes in the city of Aracaju, capital of the state of Sergipe, Brazil, using a qualitative method. Geotechnical characterization of soils from of slopes selected for analysis of stability was carried using the OptumG2® software developed by Optum Computational Engineering using the Strength Reduction Method (SRM) to obtain the safety factor. The aim of this study is to conduct a systematic analysis, associating subjective landslide risk studies with rational studies on slope stability analysis. It was found that 50% of the slopes analyzed exhibited a high or very high degree of risk, justifying the landslide risk management policies in the city. Moreover, stability analyses produced coherent results in terms of slope stability, whereby slopes with high and very high risk were classified as unstable, while the slope deemed to be stable presents medium risk of mass movements.

An Instrumented Flume for Infiltration Process Modeling, Landslide Triggering and Propagation

Rainfall is the most common cause of landslides, so it is important to know the processes underlying failure starting with the rainfall infiltration processes into the granular soils, the distribution of the water content and pore pressure in both saturated and unsaturated layers, to include their effects in terms of slope stability. Although the literature is full of simulation models, the complexity of phenomena would impose a more detailed analysis by a well-equipped flume. For that purpose, a meter-scale laboratory experiment at the University of Calabria was designed and built. It is very useful for carrying out complex tests to analyze the response of loose soils or debris in terms of stability. It is composed of two channels: the first one was adopted for analyzing the triggering mechanisms, the second one for the propagation phases. Both channels are equipped with suitable sensors for monitoring the main physical variables, i.e., spray nozzle systems to apply a specific rainfall intensity; minitensiometers and TDR (Time Domain Reflectometry) for measuring, respectively, suction values and water content; miniaturized pressure transducers for pore water pressures; and laser displacement sensors. This paper describes in detail the instrumented flume and explores its potential through the analysis of a homogeneous slope of pyroclastic soil. An experiment was carried out to reproduce landslide triggering in pyroclastic soils, evolving in mudflow, by considering a homogeneous deposit. The measurements carried out allowed testing the apparatus, describing the behavior of the soil after rainfall infiltration and better identifying factors particularly significant in the collapse mechanism and process evolution.

Three-dimensional stability of locally loaded geocell-reinforced slopes by strength reduction method

ABSTRACTIn reality, slopes rarely follow the plain strain conditions and to have a precise estimation of their stability, a 3D slope stability analysis should be conducted instead of resorting to simplistic, prevalent and more conservative 2D slope stability analysis. This is especially true for geocell-reinforced slopes for which the honeycomb structure of the geocells makes a 3D slope stability analysis inevitable. However, there has been no attempt to cover this issue so far. In this study, three-dimensional strength reduction method is employed to investigate the stability of slopes reinforced with geocells. Typical locally loaded slopes reinforced in the body with a single and three layers of geocell were modelled taking into account geocells having contact with their infill and surrounding soils. Then, effects of such contributing factors such as depth of the geocell layer placement, geocell pocket size, width of geocell layer, length of the geocell layer and slope inclination angle on the factor of safety and shape of the slip surface of slopes reinforced with a single geocell layer were studied thoroughly. Furthermore, considering three different geocell layer arrangements over the slope height, their superiority over each other in terms of slope stability was investigated.

A Probabilistic Study for the Analysis of the Risks of Slope Failure by Applying HEART Technique

During the last two decades, the cases of slope failures have soared in many parts of the world particularly in Malaysia as a result of rapidly expanding economic development, especially on hilly terrains. Extensive studies on previous slope failures unveil that, apart from rain, there are many factors that can instigate the failure in slopes. These contributing factors mainly include human errors such as lack of sufficient maintenance, incompetence during operations and incognizance of geological conditions. This study applies the tailored human error assessment and reduction technique (HEART) to determine the contributing factors of Malaysian landslides. HEART is widely used to analyse and quantify the human errors because it follows a straightforward approach that is not limited to a specific field. In this study, HEART is applied to determine the human error probability (HEP) of tasks and subtasks in the design, construction and maintenance phase of slope works that are vulnerable to human errors. An expert opinion is used for acquiring the data necessary for deducing the human error probabilities. For promoting improved slope engineering practices, this study proposes a theoretical framework to mitigate the chances of human errors in terms of slope stability.

Evaluation of the effects of three European forest types on slope stability by field and probabilistic analyses and their implications for forest management

It is well known that forests play a crucial role in preventing soil erosion and landslides; however, forests are also subjected to dynamic evolution driven by natural processes and anthropogenic factors. This dynamic evolution affects spruce and chestnut forests in some European regions (e.g., Italian Alps, central and northern Europe), where these species have been forced by management practice to establish over long periods where other species, such as European beech, would be expected to occur as a result of natural processes.Using a large dataset of field and laboratory measurements of root density and root mechanical properties, the performances of Norway spruce, Sweet chestnut and European beech are analyzed from a slope stability perspective by using a model based on the limit equilibrium principle within a probabilistic framework.The results showed differences and similarities between the root systems of the analyzed species, both in terms of root distribution and mechanical properties. However, the probabilistic distribution that better fits the root reinforcement values obtained by the experimental work is, in all cases, a lognormal function.The developed method can be used to estimate the factor of safety for several combinations of geotechnical and hydrological parameters and different root reinforcement probability distributions using Monte Carlo techniques. The obtained values have been evaluated in terms of probability to have a factor of safety of less than 1 for increasing values of slope steepness.Although each single hillslope should be studied individually to account for local stand conditions that strongly affect root system performance, European beech is generally more efficient than Sweet chestnut and Norway spruce in terms of enhancing slope stability.Based on our results, in all cases where the stability of slopes represents a concern and spruce and chestnut communities are perishing, the natural colonization by European beech should be evaluated positively and possibly promoted by forest managers. Moreover, the developed method provides a general framework that could be applied to other species and conditions to define the consequences of different forest management scenarios in terms of slope stability.

수치해석을 이용한 토목섬유망 네일의 사면보강에 대한 적용성 연구

In this study, the applicability of geotextile mesh soil nails on slopes was evaluated by numerical analysis to reduce environmental problems which a general soil nailing might produce and to improve its economical efficiency and construction convenience. To this end, in situ pull-out tests were conducted for both general soil nail and geotextile mesh soil nail and their pull-out characteristics were analyzed. Also, finite difference method was used to verify the suitability of numerical simulation. Parameters for nail and ground conditions were selected and sensitivity analysis was performed for the evaluation of slope stability. In addition, analysis was performed by limit equilibrium method which is widely used for slope stability analysis in practice. As a result, if the nail diameter was same, there is no big difference between geotextile mesh soil nails and general soil nails in terms of slope stability. Therefore it can be expected that geotextile mesh soil nails could be effective for slope reinforcement since they could keep a slope as stable as general soil nails and give better economical efficiency and construction convenience than general soil nails.

Discrete Element Modelling of Complex Failure Mechanism at Quarry Slope

Road cutting, open pit mining, quarrying and various other constructions in hilly terrain demand special attention in terms of slope stability. The analysis of slope stability is of great significance not only for ensuring safe design of excavated slope, but also for preventing potential hazards. This research was undertaken to identify the controlling parameters affecting the slope instability. As the rock slope behaviour is mostly governed by discontinuities, discontinuum numerical technique such as Discrete Element Method (DEM) which has the ability to address discontinuity controlled instability is well suited for this case. This study investigated the failure pattern and its responsible factors leading to failure of a slope at a slate quarry situated in Wales, United Kingdom as a case study. The research work consisted of field investigation, laboratory experiments and parametric analysis by powerful and renowned distinct element computational tool Universal Discrete Element Code (UDEC). Evidence showed that complex failure mechanism involving distinct planar sliding surface along with block-flexural toppling contributed to the instability at the studied slate quarry. Dip of discontinuity, presence of water, weathering state and slope angle were the significant factors found in this study to have profound impact on controlling rock slope instability. The modelling results also indicated that the influence of structurally dipping at 78° of cleavage in slate and the water filling in the crack which developed excess water pressure have triggered the failure.

The contribution of chestnut coppice forests on slope stability in abandoned territory: a case study

Sweet chestnut has been for many centuries fundamental for the Italian mountainous economies, where this kind of forest was traditionally managed in short rotation to rapidly produce wood biomass. Due to the social and economic changes, which made such management scheme unprofitable especially on the steep and remote slopes, such practice has been mainly abandoned and most of chestnut forests became over-aged and very dense, causing an increase of localized slope instability. In this work the effect of over-aged chestnut coppice forests on shallow landslides was analysed by evaluating and comparing mechanical contribution to soil shear strength provided by root systems in differently managed chestnut stands. The study area is located in Valcuvia (Lombardy Prealps) where three different stands, one managed and the others abandoned (over 40 year aged), established on cohesionless slopes (quaternary moraine deposits) were chosen having care to select homogeneous conditions in terms of substrate, aspect and elevation. As slope steepness strongly affects forestry practices and steeper stands are more frequently abandoned, the considered stands have different terrain inclination, 30-35° in abandoned stands and 13° in the managed one. Slope stability of the three sites was evaluated by applying the infinite slope approach accounting for additional root cohesion and tree surcharge. Additional root cohesion was estimated through the Fiber Boundle Model approach by collecting roots in the field and measuring their resistance in laboratory, and by measuring root diameter and density distribution with depth by the wall technique method. The results, as expected, showed that over-aging does not affect root mechanical properties, whereas it significantly affects root distribution within the soil. In terms of slope stability, when steepness exceeds 35°, instability phenomena can be triggered by high level of soil saturation in the case of over-aged forests, whereas for less extreme cases chestnut forests, although over-aged, are able and fundamental to guarantee safe conditions.

The contribution of chestnut coppice forests on slope stability in abandoned territory: a case study

Sweet chestnut has been for many centuries fundamental for the Italian mountainous economies, where this kind of forest was traditionally managed in short rotation to rapidly produce wood biomass. Due to the social and economic changes, which made such management scheme unprofitable especially on the steep and remote slopes, such practice has been mainly abandoned and most of chestnut forests became over-aged and very dense, causing an increase of localized slope instability. In this work the effect of over-aged chestnut coppice forests on shallow landslides was analysed by evaluating and comparing mechanical contribution to soil shear strength provided by root systems in differently managed chestnut stands. The study area is located in Valcuvia (Lombardy Prealps) where three different stands, one managed and the others abandoned (over 40 year aged), established on cohesionless slopes (quaternary moraine deposits) were chosen having care to select homogeneous conditions in terms of substrate, aspect and elevation. As slope steepness strongly affects forestry practices and steeper stands are more frequently abandoned, the considered stands have different terrain inclination, 30-35° in abandoned stands and 13° in the managed one. Slope stability of the three sites was evaluated by applying the infinite slope approach accounting for additional root cohesion and tree surcharge. Additional root cohesion was estimated through the Fiber Boundle Model approach by collecting roots in the field and measuring their resistance in laboratory, and by measuring root diameter and density distribution with depth by the wall technique method. The results, as expected, showed that over-aging does not affect root mechanical properties, whereas it significantly affects root distribution within the soil. In terms of slope stability, when steepness exceeds 35°, instability phenomena can be triggered by high level of soil saturation in the case of over-aged forests, whereas for less extreme cases chestnut forests, although over-aged, are able and fundamental to guarantee safe conditions.

Experimental and numerical investigation of slope stabilization by stone columns

In this study, an investigation has been performed on a small-scaled laboratory model and its numerical model by the code of PLAXIS to see the effect of stone columns (SCs) placed vertically in a soft soil slope in terms of slope stability, bearing capacity, and settlements. Also, several hypothetical cases have been examined by the code. Effect of s/D ratios (distance between the vertical axes of SCs/diameter of SCs) was also investigated on slope stability, ultimate bearing capacity, and settlement of a footing rested on top of the slope on the laboratory model. Firstly, ultimate bearing capacity and settlement properties of soil were determined for unreinforced soil that is no SCs were considered. Then, some values of soil were determined after the installation of stone columns with various ratios of s/D. The ratios of s/D were 2, 3, 3.5, and 4. The tests carried out on the laboratory model were simulated and numerically analyzed in two dimensions under plain-strain conditions by Mohr–Coulomb model. In the analyses, PLAXIS computer code, which is based on finite elements method, has been employed. Then, a parametric investigation was carried out to see the effect of SCs on the stability of the slope. In the parametric investigation, several hypothetical cases that were one layer of soil and two layers of soil with the presence of water in the reservoir side of the slopes were examined. The analyses in the investigation were performed by the PLAXIS code for various slope angles β, ratios of c/(γH), and ratios of s/D. From the test results of the laboratory model, and the results obtained from the numerical analyses, it was observed that the bearing capacity of the footing constructed on the top of the slope in soft soil was increased; settlements were decreased after the improvement with SCs. From the analyses performed, it was found that the SCs increased the stability of slope 1.18- to 1.62-fold as a relative effect of different parameters.

Geomorphological and geotechnical causes of anthropogenically induced rock‐mass falls in the wachau‐danube valley (bohemian massif, lower austria)

Laimer, H.J. and M¨llegger, M., 2012. Geomorphological and geotechnical causes of anthropogenically induced rockmass falls in theWachau‐Danube Valley (Bohemian Massif, Lower Austria). Geografiska Annaler: Series A, Physical Geography, 94, 157–174. doi:10.1111/j.1468‐0459.2012.00451.xABSTRACTThe Wachau‐Danube Valley represents a transverse valley, intersecting the Variscian Bohemian Massif. Weakened rocks along fault structures led to accelerated river erosion, forming relatively steep rock slopes. The exceptional cultural position of the region generated an increasing demand for building materials. Over the centuries quarrying had a sizeable impact on slope morphology. Interdependences between quarrying and construction caused unstable rock slopes and four rock‐mass falls have occurred at two quarries near Spitz (1961, 1984, 2002) and Dürnstein (2009). Rock mechanical analysis at these quarries has shown that the combination of existing geological discontinuities and artificially modified morphology is fatal in terms of slope stability. In Spitz the bedding planes within the marble had been undercut by the mining face. Additionally, two conjugated, steeply dipping joint sets formed large scale blocks sliding on bedding planes. In three major rockslides/rock‐mass falls, each triggered by heavy rainfalls, a total mass of 170-000m3 of rock failed. At the quarry near Dürnstein the geotechnical characteristics of the gneiss are also unfavourable in relation to the exposition of the mining face. After several rockfalls, 65-000m3 were blasted away in 1909 to remove unstable rock slopes. The residual rock face was destabilized and rockfall activities culminated in an event with a total volume of approximately 15-000m3. Remedial measures for both locations are essential to maintain transport infrastructure. Sufficiently stable conditions can only be achieved by extensive reshaping of the mining faces, which involves adapting slope geometries to naturally stable joint faces.

The relationship between the performance of soil conditions and damage following an earthquake: a case study in Istanbul, Turkey

Abstract. Istanbul city has experienced many strong earthquakes throughout its history and suffered extensive damage. The old Istanbul (Fatih and Eminonu districts), one of the most densely populated locations of Istanbul city, is a commercial centre and has many significant historical buildings. In this study, the data pertaining to the damage sustained by historical artifacts and structures from past earthquakes, are examined along with the soil amplification of the region, the liquefaction and slope stability risk in relation to the seismic microzonation maps which were prepared using geographic information system techniques. The relationship between soil behaviour and the damage resulting from previous earthquakes. The structural damage observed in the region was in accordance with the microzonation maps. Since the area does not have a high risk in terms of slope stability, this does not have much impact on the level of damage. However, it was found that soil amplification and partial liquefaction contributed to the damage to historical artifacts and structures.