Water

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22 pages, 4638 KiB

Open AccessArticle

The Key Parameters Involved in a Rainfall-Triggered Landslide

by Elisangela do Prado Oliveira, Andrés Miguel González Acevedo, Virnei Silva Moreira, Vitor Pereira Faro and Alessander Christopher Morales Kormann

Water 2022, 14(21), 3561; https://doi.org/10.3390/w14213561 - 5 Nov 2022

Cited by 3 | Viewed by 2470

Abstract

In addition to the intensity of precipitation, the different hydraulic and mechanical properties of a soil hill can also be responsible for landslides. More specifically, the same rainfall amount can trigger or not trigger a mass movement depending on its characteristics. This issue [...] Read more.

In addition to the intensity of precipitation, the different hydraulic and mechanical properties of a soil hill can also be responsible for landslides. More specifically, the same rainfall amount can trigger or not trigger a mass movement depending on its characteristics. This issue represents a great geotechnical hazard in mountainous regions such as Brazil, Italy, South Africa, Japan and Hong Kong. The understanding of each of the key factors involved in a rainfall-triggered landslide can be deepened and also quantified. Thus, this research defines, through a numerical model, which parameters are the key factors involved in slope stability. A homogeneous and unsaturated hill was studied. Its different hydraulic and mechanical properties were varied. Geometry and mechanical parameters were shown to exert the greatest influence on stability. Hydraulic parameters, for the same amount of rain, showed a lower influence. The fitting parameters of the soil–water characteristic curve of the materials had a low impact on stability when compared to other parameters assessed. Our conclusions can help future laboratory and field studies to focus more on the accuracy and confidentiality of the key parameters. The results are also important as they give direction to studies related to precipitation threshold definition. Full article

(This article belongs to the Special Issue Landslides Induced by Surface and Groundwater)

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12 pages, 5370 KiB

Open AccessArticle

Evaluation of Debris-Flow Vibration Signals Recorded at the Aiyuzi Stream in Shenmu Taiwan Using Machine Learning Methods

by Yi-Min Huang and Chien-Chih Chen

Water 2022, 14(21), 3518; https://doi.org/10.3390/w14213518 - 3 Nov 2022

Cited by 3 | Viewed by 1539

Abstract

In recent years, due to the frequent occurrence of extreme weather due to climate change, the Taiwan region has often suffered from landslides and debris flows in the past 20 years. This study used the ground surface vibration signals collected by the geophone [...] Read more.

In recent years, due to the frequent occurrence of extreme weather due to climate change, the Taiwan region has often suffered from landslides and debris flows in the past 20 years. This study used the ground surface vibration signals collected by the geophone from seven debris flow events in the Shenmu area. Data were processed to represent the time series of velocity and accumulated energy per second. Datasets were established for model training and validation. In this study, Support Vector Machine (SVM) and Random Forest (RF) algorithms were used for comparison. After analyzing the data through balance processing (Synthetic Minority Oversampling Technique, SMOTE), a signal model of debris flow was established. The research results showed that the models using SVM and RF training had good accuracy, recall, and AUC values when choosing input data average of every 6 s and the 10-s time interval within which the data were marked as the occurrence of debris flow. The performance of SVM was better than that of RF after validation. Through the aforementioned research, the vibration signals of debris flow can be regarded as a reference factor, and the model established by the SVM method had acceptable performance and can be used for early-warning of debris flow. Full article

(This article belongs to the Special Issue Landslides Induced by Surface and Groundwater)

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20 pages, 4095 KiB

Open AccessArticle

Different Toppling Bank Slope Failures under Hydrodynamic Action during Impoundment of the Miaowei Hydropower Station Reservoir

by Zhigang Shan, Jingqing Lv, Faming Zhang, Liang Chen, Fei Yin and Menglong Dong

Water 2022, 14(13), 2126; https://doi.org/10.3390/w14132126 - 4 Jul 2022

Cited by 3 | Viewed by 2646

Abstract

Toppling is a common deformation and failure phenomenon in the reservoir bank slopes of hydropower projects. This paper studies the genesis and evolution of different toppling bodies during water impoundment at the Miaowei Hydropower Station Reservoir on the Lancang River in southwest China. [...] Read more.

Toppling is a common deformation and failure phenomenon in the reservoir bank slopes of hydropower projects. This paper studies the genesis and evolution of different toppling bodies during water impoundment at the Miaowei Hydropower Station Reservoir on the Lancang River in southwest China. Toppling properties were determined and second failure characteristics analyzed in different reservoir impoundment stages. Different degrees of toppling deformation were primarily affected by the transverse bending stress, while the regional tectonic stress has been shown to have a significant effect on the transverse bending of the rock layers. Combined with the on-site investigation and monitoring results, the failure mechanisms of the different toppling deformation bodies were analyzed. The second failure of the toppling rock mass caused by the reservoir impoundment process is mainly the hydrodynamic splitting along fractures, wave impaction and softening on the slope foot. The transverse bending effect of gravity is transmitted upward through joint misalignment, rotation and slip, accelerating the speed of secondary toppling failure and forming a compression-shear failure along the toppling tension crack. A model to predict the scope and time of failure in the toppling deformation banks under the action of reservoir hydrodynamics was proposed. Full article

(This article belongs to the Special Issue Landslides Induced by Surface and Groundwater)

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12 pages, 2688 KiB

Open AccessArticle

Root Functional Traits and Water Erosion-Reducing Potential of Two Indigenous C₄ Grass Species for Erosion Control of Mudstone Badlands in Taiwan

by Jung-Tai Lee, Yu-Syuan Lin, Cheng-Ying Shih and Ming-Jen Lee

Water 2022, 14(9), 1342; https://doi.org/10.3390/w14091342 - 20 Apr 2022

Viewed by 1858

Abstract

In southern Taiwan, mudstone badland accounts for over 1000 km² of the upstream region of watersheds. Rainstorms often induce interrill and surface erosion on the mudstone slopes. Furthermore, the large quantity of soils detached by surface runoff result in severe sedimentation in [...] Read more.

In southern Taiwan, mudstone badland accounts for over 1000 km² of the upstream region of watersheds. Rainstorms often induce interrill and surface erosion on the mudstone slopes. Furthermore, the large quantity of soils detached by surface runoff result in severe sedimentation in reservoirs. Thus, soil erosion control of mudstone badlands represents one of the most pressing problems in reservoir watershed management. Cynodon dactylon (L.) Pers. (Bermuda grass) and Eremochloa ophiuroides (Munro) Hack. (Centipedegrass) are two native predominant C₄ grass species appearing on mudstone badlands. They play a key role in erosion control and the revegetation of mudstone slopes. Nevertheless, their root functional traits and water erosion-reducing potential have not been investigated. In this study, the root traits were examined. Vertical pullout and tensile tests were conducted to measure root pullout resistance and root tensile strength. Hydraulic flume tests were also performed to evaluate their water erosion-reducing potentials. The results demonstrated that the root systems of C. dactylon and E. ophiuroides grasses all belonged to the fibrous M-type. C. dactylon had remarkably better root traits compared to those of E. ophiuroides. Furthermore, the root tensile resistance of C. dactylon was remarkably higher than that of E. ophiuroides. In addition, hydraulic flume tests showed that C. dactylon has remarkably smaller soil detachment rates than that of E. ophiuroides. Altogether, our data clearly show that C. dactylon has better root traits, root pullout resistance, root tensile resistance and water erosion-reducing potential than E. ophiuroides and is more suitable for erosion control of mudstone badland. Further studies on large-scale implementation techniques of these species for efficient vegetation restoration are needed. Full article

(This article belongs to the Special Issue Landslides Induced by Surface and Groundwater)

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11 pages, 3432 KiB

Open AccessArticle

Effect of Statistically Anisotropic Undrained Shear Strength on the Probability of Slope Failure

by Cheng Yu, Yukun Li, Weiya Ge, Faming Zhang, Xiaolan Hou, Zinan Li and Menglong Dong

Water 2022, 14(8), 1225; https://doi.org/10.3390/w14081225 - 11 Apr 2022

Viewed by 1706

Abstract

Due to large-scale geological deposition processes, slope structures are often stratified, which means that the spatial distribution of the parameters involved in slope reliability evaluation is statistically anisotropic. This paper studies the effect of the statistical anisotropy of undrained shear strength on the [...] Read more.

Due to large-scale geological deposition processes, slope structures are often stratified, which means that the spatial distribution of the parameters involved in slope reliability evaluation is statistically anisotropic. This paper studies the effect of the statistical anisotropy of undrained shear strength on the probability of slope failure (p_f) based on the Monte Carlo simulation. The results show that for the horizontally layered slope, the larger the horizontal correlation scale of undrained shear strength (λ_x) is, the larger p_f is, especially when λ_x is smaller than the slope length; for the vertically layered slope, the larger the vertical correlation scale (λ_y) is, the smaller p_f is, especially when λ_y is smaller than the slope height. Additionally, the mechanism of the above results is discussed by analyzing the displacement distribution at different correlation scales. The findings indicate that in the reliability evaluation of undrained slopes in stratified structures, either underestimation of λ_x or overestimation of λ_y leads to an unconservative estimate of p_f, resulting in an overestimation of the slope stability. Full article

(This article belongs to the Special Issue Landslides Induced by Surface and Groundwater)

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14 pages, 35829 KiB

Open AccessArticle

Using Fuzzy Neural Networks to Model Landslide Susceptibility at the Shihmen Reservoir Catchment in Taiwan

by Chuen-Ming Huang, Chyi-Tyi Lee, Liu-Xuan Jian, Lun-Wei Wei, Wei-Chia Chu and Hsi-Hung Lin

Water 2022, 14(8), 1196; https://doi.org/10.3390/w14081196 - 8 Apr 2022

Cited by 1 | Viewed by 1838

Abstract

Machine learning algorithms are commonly employed in landslide susceptibility assessments. Recently, algorithms that utilize artificial intelligence have come into prominence. This study attempts to adapt the most fundamental framework of deep learning and introduces fuzzy theory concepts to analyze landslide susceptibility while updating [...] Read more.

Machine learning algorithms are commonly employed in landslide susceptibility assessments. Recently, algorithms that utilize artificial intelligence have come into prominence. This study attempts to adapt the most fundamental framework of deep learning and introduces fuzzy theory concepts to analyze landslide susceptibility while updating the network parameters with trial-and-error methods. The final analysis results will compare with those of logistic regression (LR). In order to assess the ability of the model to identify landslides in a more objective way, two typhoon events were used as a training event and a validation event, respectively. The results of the analysis show that the area under the curve (AUC) of the fuzzy neural network (FNN) for the training event is 0.915, but the AUC for the validation event drops to 0.746. Although the results of the FNN for training events were better than those of LR, they did not differ much from those of LR in predicting future events. The reason for this is that the difference between the landslide distributions of the training and validation events is too large, making the model biased in its identification. Overall, FNN is still a recommended method for analyzing landslide potential and can be used as a reference for LR. Full article

(This article belongs to the Special Issue Landslides Induced by Surface and Groundwater)

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18 pages, 5708 KiB

Open AccessArticle

Rainfall-Induced or Lake-Water-Level-Controlled Landslide? An Example from the Steep Slopes of Lake Balaton, Hungary

by Fruzsina Kápolnainé Nagy-Göde and Ákos Török

Water 2022, 14(7), 1169; https://doi.org/10.3390/w14071169 - 6 Apr 2022

Cited by 6 | Viewed by 3084

Abstract

The present paper provides a case study and an overview of the stability of high banks bordering the eastern basin of the largest central European lake, Lake Balaton, in Hungary. External factors such as rain, lake-water level, or pore water pressure are considered [...] Read more.

The present paper provides a case study and an overview of the stability of high banks bordering the eastern basin of the largest central European lake, Lake Balaton, in Hungary. External factors such as rain, lake-water level, or pore water pressure are considered in the stability analysis. The slope stability was assessed using two software with different approximations and calculation methods. The results of the models using Plaxis and Rocscience Slide2 are compared. One of the major identified failure scenarios is the deep-seating rotational landslides that are triggered by rain and elevated groundwater table. The modeled slip surfaces are in good agreement with the inclinometer monitoring data of the site; meanwhile, the top of the slope failures is not influenced by water level. Full article

(This article belongs to the Special Issue Landslides Induced by Surface and Groundwater)

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20 pages, 4455 KiB

Open AccessFeature PaperArticle

A Novel Radial Basis Function Approach for Infiltration-Induced Landslides in Unsaturated Soils

by Cheng-Yu Ku, Chih-Yu Liu and Frank T.-C. Tsai

Water 2022, 14(7), 1036; https://doi.org/10.3390/w14071036 - 25 Mar 2022

Cited by 3 | Viewed by 2180

Abstract

In this article, the modeling of infiltration--induced landslides, in unsaturated soils using the radial basis function (RBF) method, is presented. A novel approach based on the RBF method is proposed to deal with the nonlinear hydrological process in the unsaturated zone. The RBF [...] Read more.

In this article, the modeling of infiltration--induced landslides, in unsaturated soils using the radial basis function (RBF) method, is presented. A novel approach based on the RBF method is proposed to deal with the nonlinear hydrological process in the unsaturated zone. The RBF is first adopted for curve fitting to build the representation of the soil water characteristic curve (SWCC) that corresponds to the best estimate of the relationship between volumetric water content and matric suction. The meshless method with the RBF is then applied to solve the nonlinear Richards equation with the infiltration boundary conditions. Additionally, the fictitious time integration method is adopted in the meshless method with the RBF for tackling the nonlinearity. To model the stability of the landslide, the stability analysis of infinite slope coupled with the nonlinear Richards equation considering the fluctuation of transient pore water pressure is developed. The validation of the proposed approach is accomplished by comparing with exact solutions. The comparative analysis of the factor of safety using the Gardner model, the van Genuchten model and the proposed RBF model is provided. Results illustrate that the RBF is advantageous for reconstructing the SWCC with better estimation of the relationship than conventional parametric Gardner and van Genuchten models. We also found that the computed safety factors significantly depend on the representation of the SWCC. Finally, the stability of landslides is highly affected by matric potential in unsaturated soils during the infiltration process. Full article

(This article belongs to the Special Issue Landslides Induced by Surface and Groundwater)

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