The use of Slope Stability Radar (SSR) in managing slope instability hazards

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.

Download Full-text

Probability Assessment of Slope Instability in Seasonally Cold Regions under Climate Change

10.21203/rs.3.rs-408312/v1 ◽

2021 ◽

Author(s):

Yulong Zhu ◽

Tatsuya Ishikawa ◽

Tomohito J. Yamada ◽

Srikrishnan Siva Subramanian

Keyword(s):

Climate Change ◽

Slope Stability ◽

Water Content ◽

Air Temperature ◽

Climate Changes ◽

Slope Instability ◽

Climate Factors ◽

Cold Regions ◽

The Past ◽

Assessment Approach

Abstract This paper proposes an effective approach for evaluating the influences of climate change on slope stability in seasonally cold regions. Firstly, to semi-quantitatively assess the effects of climate changes on the uncertainty of climate factors, this study analyzes the trend of the two main climate factors (precipitation and air temperature) by the regression analysis using the meteorological monitoring data of the past 120 years in different scales (e.g., world, country (Japan), and city (Sapporo)), and the meteorological simulation data obtained by downscaling the outputs of three different regional atmospheric models (RAMs) with lateral boundary conditions from three different general circulation models (GCMs). Next, to discuss the effects of different climate factors (air temperature, precipitation, etc.) and to determine the key climate factors on the slope instability, an assessment approach for evaluating the effects of climate changes on slope instability is proposed through the water content simulation and slope stability analysis using a 2-dimensional (2D) finite element method (FEM) homogeneous conceptual slope model with considering freeze-thaw action. Finally, to check the effectiveness of the above assessment approach, assessment of instability of an actual highway embankment slope with the local layer geometry is done by applying the past and predicted future climate data. The results indicate that affected by global warming, the air temperature rise in some cold cities is more serious. The predicted future weather will affect the shape of the normal density curve (NDC) of the distribution of slope failures in one year. The climate changes (especially the increase in precipitation) in the future will increase the infiltration during the Spring season. It will lengthen the time that the highway slope is in an unstable state due to high volumetric water content, thereby enhancing the instability of the slopes and threatening more slopes in the future.

Download Full-text

Seismic Coefficients for Simplified Deepwater Slope Stability Assessment Under Earthquake Loading

10.4043/31056-ms ◽

2021 ◽

Author(s):

Aurelian C. Trandafir

Keyword(s):

Finite Element ◽

Slope Stability ◽

Shear Strain ◽

Limit Equilibrium ◽

Slope Instability ◽

Earthquake Loading ◽

Complex Deformation ◽

Correlation Relationship ◽

Stability Analyses ◽

Seismic Coefficient

Abstract Pseudostatic limit-equilibrium based slope stability analyses are carried out on a routine basis to evaluate stability of submarine slopes under earthquake loading. For slopes in deepwater settings, a major challenge in performing pseudostatic slope stability analyses is selection of an appropriate seismic coefficient. Most published displacement-based methodologies for seismic coefficient selection were developed using simplified sliding block models for seismic slope performance evaluation that are unable to capture the complex deformation mechanism of deepwater slopes during earthquakes. To address this challenge, this study employs two-dimensional dynamic finite-element based deformation analysis to investigate the earthquake response of submarine clay slopes characterized by morphology, stratigraphic architecture and geotechnical properties representative for the deepwater environment. Finite-element computed seismic slope performance indicators, including horizontal peak ground acceleration at the seafloor and earthquake-induced maximum shear strain within the slope, along with horizontal seismic coefficients required to trigger slope instability in limit-equilibrium based pseudostatic stability analyses are used to develop a rational shear strain-based correlation relationship for deepwater slope seismic coefficient selection.

Download Full-text

Characteristics of ground motion and threshold values for colluvium slope displacement induced by heavy rainfall: a case study in northern Taiwan

Natural Hazards and Earth System Science ◽

10.5194/nhess-16-1309-2016 ◽

2016 ◽

Vol 16 (6) ◽

pp. 1309-1321 ◽

Cited By ~ 5

Author(s):

Ching-Jiang Jeng ◽

Dar-Zen Sue

Keyword(s):

Slope Stability ◽

Heavy Rainfall ◽

Slope Failure ◽

Drainage System ◽

Threshold Value ◽

Slope Instability ◽

Disaster Prevention ◽

Strain Gages ◽

Slope Displacement ◽

Northern Taiwan

Abstract. The Huafan University campus is located in the Ta-lun Shan area in northern Taiwan, which is characterized by a dip slope covered by colluvium soil of various depths. For slope disaster prevention, a monitoring system was constructed that consisted of inclinometers, tiltmeters, crack gages, groundwater level observation wells, settlement and displacement observation marks, rebar strain gages, concrete strain gages, and rain gages. The monitoring data derived from hundreds of settlement and displacement observation marks were analyzed and compared with the displacement recorded by inclinometers. The analysis results revealed that the maximum settlement and displacement were concentrated on the areas around the Hui-Tsui, Zhi-An, and Wu-Ming buildings and coincided with periods of heavy rainfall. The computer program STABL was applied for slope stability analysis and modeling of slope failure. For prevention of slope instability, a drainage system and tieback anchors with additional stability measures were proposed to discharge excess groundwater following rainfall. Finally, threshold value curves of rainfall based on slope displacement were proposed. The curves can be applied for predicting slope stability when typhoons are expected to bring heavy rainfall and should be significant in slope disaster prevention.

Download Full-text

Safety Assessment of Tunnel Portals for Site Selection Based on Spatial Information Geoprocessing

Infrastructures ◽

10.3390/infrastructures4040070 ◽

2019 ◽

Vol 4 (4) ◽

pp. 70

Author(s):

Iau-Teh Wang

Keyword(s):

Information Technology ◽

Slope Stability ◽

Site Selection ◽

Spatial Information ◽

Slope Instability ◽

Geographical Information ◽

Site Evaluation ◽

The Stability ◽

Slice Method ◽

Spatial Information Technology

The evaluation of portal locations for mountain tunnels is among the most crucial considerations during route selection and structural layout planning. The development of spatial information technology has provided a more objective approach for assessing the slope stability of potential portal sites. The simulations in such studies have been performed to evaluate potential hazards and slope stability. However, potential instabilities resulting from excavation are seldom considered in these studies. Therefore, a method based on spatial information technology was developed in this study for considering the potential impact of the direction and depth of excavations on portal stability. An analysis method for an infinite slope was integrated into the geographical information system for evaluating the stability of critical wedges. The proposed method provides a reasonable estimation comparable with that provided by the conventional slice method. The results of applying this method to six mountain tunnel portals where slope instability occurred during construction indicate that the actual outcomes agreed with the predicted outcomes. For potential portal site evaluation, the proposed method facilitates the rapid estimation of safety factors for various slope designations, which is useful for site selection.

Download Full-text

Study on Slope Instability Disciplinarian on the Condition of Rainfall

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.654 ◽

2013 ◽

Vol 353-356 ◽

pp. 654-658

Author(s):

Nan Tong Zhang ◽

Xiao Chun Zhang ◽

Hua Rong Wang ◽

Chen Yan

Keyword(s):

Slope Stability ◽

Tensile Stress ◽

Rainfall Intensity ◽

Pore Water Pressure ◽

Water Pressure ◽

Road Construction ◽

Slope Instability ◽

Slope Surface ◽

Large Area ◽

Break Zone

Slope stability is one of the problems of road construction which should be faced with and solve. Rainfall can reduce the shear strength of slope soil and raise the underground water level which can lead to increase slope soil pore water pressure. The influence of rainfall infiltration on slop is mainly to change the slope seepage field, increase dynamic and hydrostatic water load on the slope soil and decrease of soil shear parameters. More abundant rainfall of typhoon area could make the road slope stability more fragile. Based on Matoushan Mountain along 104 state roads in Taizhou city, Zhejiang province, slope instability disciplinarian on the condition of rainfall is studied using the method of numerical simulation in this paper. As the results, when the rainfall intensity was 0.006 m/h and continuous rain was in 24 hours, the slope surface compressive stress tends to zero which began to appear tensile stress area on the condition of self-weight. And when the rainfall intensity was 0.01 m/h and continuous rain was in 24 hours, the large area of the slope surface was tensile stress area which means to appear break zone in slope surface and likely to landslide at the same time.

Download Full-text

The Records of Slope Reinforcement Engineering in a Loess City

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.226-228.1365 ◽

2012 ◽

Vol 226-228 ◽

pp. 1365-1370

Author(s):

Qi Xia Liu ◽

Liang Fan

Keyword(s):

Slope Stability ◽

Good Practice ◽

Stability Study ◽

Practice Effect ◽

Slope Instability ◽

Loess Landslide ◽

Loess Area ◽

Loess Slope ◽

Geological Conditions ◽

Reinforcement Measures

This article selected a typical loess slope engineering as the research object, and through the characteristics of loess landslide, landslide environmental geological conditions, the formation mechanism of the landslide study of the loess area of urban slope instability factors, loess slope stability of the calculation method and reinforcement measures. This paper adopts the theory of Morgenstern-Price to analyzing the stability of the slope, referencing with Sweden finite slice method, Simplified Bishop method, Simplify Janbu method. The reinforcement adopts the technology of possessed anchor to disposing the loess slope, and has good Practice effect. The loess slope stability study area has a large reference.

Download Full-text

Modelling the effect of Nature Based Solutions on slope instability

10.5194/egusphere-egu2020-9867 ◽

2020 ◽

Author(s):

Stefano Tinti ◽

Glauco Gallotti ◽

Thomas Zieher ◽

Jan Pfeiffer ◽

Filippo Zaniboni ◽

...

Keyword(s):

Slope Stability ◽

Land Use Planning ◽

Groundwater Level ◽

Numerical Models ◽

Slope Instability ◽

Seismic Load ◽

Technical Parameters ◽

Hydrological System ◽

The Stability ◽

Open Air Laboratories

<p>In the framework of the OPERANDUM (OPEn-air laboRAtories for Nature baseD solUtions to Manage environmental risks) project, modelling the effect of the Nature Based Solutions (NBS) on selected open-air laboratories plays a determinant role. In this work, we focus the attention on the V&#246;gelsberg (Tyrol, Austria) landslide case study, located in the municipality of Wattens. The 0.25&#160;km<sup>2</sup> active part of the slope shows annual movement rates in the order of 3.5-6&#160;cm/a. Recent studies provided evidence that the motion is mainly driven by variations of the groundwater level. The latter are related to prolonged moist periods during which excessive rainfall or snow melt water can infiltrate and act on the geo-hydrological system. With the aim of enhancing the slope stability employing NBS, a detailed analysis of the hydrogeology and the slope characteristics have been carried out, obtaining the required technical parameters describing the involved soil material. Furthermore, a slope stability analysis by means of different numerical models has been performed. Results prove that variations of the groundwater level in the range of 1-2 m can strongly affect the stability of the slope. Thus, specific NBS should aim at reducing the amount of infiltrating water. Examples of such NBS include the adaptation of forest management and land use planning, the introduction and re-activation of drainage channels and the sealing of leaky streams and channels. Beside the effects of the variation of the groundwater level, results have proved that the slope could fail under the action of a moderate seismic load. In this scenario, it is likely that the effects of the NBS would be insufficient to maintain the slope intact.</p>

Download Full-text

Study on the Effects of the Rainwater Seepage on Slope Stability

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.580-583.729 ◽

2014 ◽

Vol 580-583 ◽

pp. 729-732

Author(s):

Ju Sheng Xun ◽

Xiang Tian Xu ◽

Rui Qiang Bai

Keyword(s):

Moisture Content ◽

Slope Stability ◽

Safety Factor ◽

Slope Instability ◽

Rain Intensity ◽

Work Condition ◽

Mountainous Regions ◽

Bishop’S Method ◽

Coulomb Criterion ◽

Road Slope

The work condition of the highway, which is usually built in mountainous regions, is complex relative to the ordinary road. Slope instability accident caused by the seepage of rainwater usually occurred in the rainy season. The mechanism for seepage failure of slope was investigated by used the Mohr-Coulomb criterion and the principle of effective stress. The effect of rain intensity on slope stability was equivalently instead by the effect of moisture content on slope stability. The influence of moisture content on the safety factor of slope stability was further calculated according to the Bishop’s method. The degeneration of safety factor follow to the moisture content was presented in the percentage.

Download Full-text

Slope instability and valley formation in Canadian soft clay deposits

Canadian Geotechnical Journal ◽

10.1139/t86-039 ◽

1986 ◽

Vol 23 (3) ◽

pp. 261-270 ◽

Cited By ~ 18

Author(s):

Guy Lefebvre

Keyword(s):

Slope Stability ◽

Soft Clay ◽

Slope Instability ◽

Coarse Grained ◽

Stability Conditions ◽

Geological Time ◽

Eastern Canada ◽

Valley Bottom ◽

Clay Deposits ◽

Groundwater Regime

The purposes of the paper are to examine the deepening of valleys in clay deposits of Eastern Canada and in particular to look at the changes in the groundwater regime and slope stability conditions during valley formation. Field observations and laboratory testing indicate that the rate of valley deepening in Champlain clay deposits is of the order of only a few millimetres a year, owing to the low erodibility of the intact clay. The clay banks are, however, more erodible, owing to alteration and fissuration.The stratigraphy of Eastern Canadian clay deposits can be simplified by considering it to be a stratum of low permeabilityconfined between two boundary layers of relatively high permeability, which are the till layer at the base and a weathered crust or coarse-grained layer at the top. As the valley bottom get closer to the bottom till layer, the groundwater regime, and consequently the stability conditions, are modified. During the process of valley formation, the groundwater regime passes through astage where the conditions are rather detrimental to slope stability as it evolves toward conditions that enhance bank stability. Those changes in stability conditions happen over geological time more rapidly or less, depending on clay erodibility. Key words: soft clay, valley formation, slope stability, groundwater, erosion, erodibility.

Download Full-text