Sloping Layer Research Articles

Wetting induced instabilities in layered slopes: A Material Point Method analysis

The increase of pore water pressure due to rainfall infiltration or upstream recharge is among the primary triggers of landslides, and soil layering has a significant effect on the hydromechanical behavior of the slope. The failure and post-failure behavior of heterogeneous layered slopes triggered by these phenomena are investigated in this study. In particular, a low permeability layer is embedded in a reference slope with different inclinations, and the impact of different saturation mechanisms on the post-failure behavior is assessed. To this aim, an unsaturated formulation of the Material Point Method (MPM) is used to reproduce the whole deformation process of a layered slope. The results show different failure and post-failure mechanisms and kinematics for both upstream recharge and rainfall infiltration (i.e., bottom-up and top-down saturation processes, respectively). Bottom-up saturation mechanism triggers deep failure mechanisms that barely evolve during the instability process. On the contrary, top-down saturation mechanism induces an anticipated shallow semi-planar failure limited by the location of the low permeable layer. These failures are characterized by high velocities and by a deepening of the slip surface during the post-failure process. Final displacements in both wetting mechanisms are of the same order of magnitude. The subsequent reactivation movements are observed as a result of the continuous injection of water in the system.

Variability and driving factors of the soil saturated hydraulic conductivity along the horizontal and vertical directions in the upper catchment of Benggang

Benggang is a unique soil erosion landform in the subtropical hilly granite area of South China that seriously endangers the local ecology and environment. In this study, a developing Benggang in South China was selected to explore the spatial variability and the driving factors of the soil saturated hydraulic conductivity (Ks). The results demonstrated that the soil properties of Benggang landforms varied with the soil layer depth and slope position. Only the sand content increased with decreasing distance from the collapsing wall, while the soil organic matter (SOM) content, free iron oxide (Fed) content and cation exchange capacity (CEC) exhibited the opposite trend. Particularly, these parameters exhibited the most significant variation between the middle slope (MS) and lower slope (LS) I and II positions. The Ks values at the LS positions were significantly higher than those at the upper slope (US) and middle slope (MS) positions, and the Ks values first decreased and then increased as the soil layer depth increased. Among the slope positions, the variation in Ks values followed the order of LS II > LS I > US > MS. The Ks values in different directions exhibited notable multifractal characteristics, and the heterogeneity was stronger in the vertical direction than in the horizontal direction. The soil Ks values significantly differed between the different directions at four slope positions, and the values along the vertical direction were higher than those along the horizontal direction at the US and MS sites. However, the values along the horizontal direction were higher than those along the vertical direction at the LS I and LS II sites. Especially at the LS II site, the difference in the soil Ks values between the two directions was extremely significant (P < 0.01). The correlation coefficient values between Ks and the number, area ratio and mean volume of soil macropores were > 0.8. Path analysis revealed that the mean volume of macropores was the main factor affecting the Ks variation. The difference in the soil Ks values at the LS positions could effectively explain the mechanism of headward erosion on the Benggang slope. This study provides a theoretical basis for Benggang erosion control and the prevention of soil erosion in South China.

Analysis on the dispersion characteristics of surface waves in a layered slope

For landslide detection and monitoring, surface wave methods (such as multichannel analysis of surface waves and array microtremor measurements), can be exploited to infer the subsurface shear-wave velocity (VS), which is a key physical parameter for calculating the soil vulnerability index and slope stability. To facilitate implementation, the seismic sources and geophones of survey lines traversing the slope of a landslide are commonly deployed along the direction of gravity. Considering that single (vertical)-geophones are extensively utilized in a variety of practical applications, it is meaningful to analyze the dispersion characteristics of the gravity-oriented component in a layered slope. Based on the stiffness matrix method and a coordinate rotation, we derive an explicit relationship for the gravity-oriented component in a layered slope. We further analyze the dispersion characteristics of the gravity-oriented component in three typical layered slopes by using a new developed tool comprising a seismic wavefield simulation and a modified frequency–Bessel transform. The results show that the dispersion spectra of the gravity-oriented component may be contaminated by Love waves, which can cause the Rayleigh wave dispersion curves to be misidentified. As the slope angle and the included angle between the survey line and dip direction increase, Love waves interfere more with the dispersion spectra of the gravity-oriented component. Numerical experiments indicate that if the slope angle is <17° or the angle between the survey line and dip direction is kept below a certain reasonable threshold, the dispersion spectra of the gravity-oriented component are determined mainly by Rayleigh waves. Moreover, we propose an azimuth filter method to suppress the interference of Love waves for passive surface wave dispersion measurements. The presented method offers useful guidance and emphasizes the great potential of surface wave methods in landslide detection and monitoring applications.

Damage evolution mechanism of rock-soil mass of bedrock and overburden layer slopes based on shaking table test

Damage evolution mechanism of rock-soil mass of bedrock and overburden layer slopes based on shaking table test

Analysis of blasting vibration signal of high steep anti-dip layered rock slope

Analysis of blasting vibration signal of high steep anti-dip layered rock slope

Slope stability machine learning predictions on spatially variable random fields with and without factor of safety calculations

Random field Monte Carlo (MC) reliability analysis is a robust stochastic method to determine the probability of failure. This method, however, requires a large number of numerical simulations demanding high computational costs. This paper explores the efficiency of machine learning (ML) models and Artificial Neural Networks used as surrogate models trained on a limited number of random field slope stability simulations in predicting the results of large datasets. The paper explores the efficiency of the predictions on the probability of failure using databases with and without factor of safety (FOS) computations. An extensive range of soil heterogeneity and anisotropy is examined on unstratified and layered slopes. On datasets requiring only the examination of failure or non-failure class of slopes (without FOSs), the performance of ML classification of the random field slope stability results generally reduces with higher anisotropy and heterogeneity of the soil. However, using the probability summation method proposed here, ML prediction of the probability of failure is shown to be highly accurate for the whole range of soil heterogeneity and anisotropy. The errors in the predicted probability of failure using 5% of MC data is only 0.46% in average for the prediction of the remaining unseen 95% of data. Offering such accuracies, the approach accelerates the computations for about 100 folds. The models also proved similarly efficient in predicting FOSs for stratified random field anisotropic heterogenous slopes.

Vertical grain-size trend of mouth bar in lacustrine fan delta: Flume experiments

Field observational previously indicated a mouth bar of a fan delta could exhibit a fining- or coarsening-upward trend, which bring a new challenge to the identification of mouth bar in subsurface studies due to the lack of morphological descriptions. Previous studies have indicated that effluent behavior in river-mouth system can affect the vertical grain-size trend of mouth bar, but the drivers and magnitude of this phenomenon are not understood. We conducted flume experiments to investigate the mechanism and controlling factors of vertical grain-size trend of mouth bar. Experiment with a steeper slope of the substrate layer, greater discharge, higher sediment/water ratio, and coarser sediment induced a fining-upward trend of mouth bar, because the effluent was dominated by strong inertia. Mouth bar in the experiment with a gentler slope of the substrate layer, smaller discharge, lower sediment/water ratio, and finer sediment exhibited a coarsening-upward trend dominated by the friction-dominated effluent. The relationship between the vertical grain-size trend of mouth bar and the gradients of foreset bedding in small-scale flume models and the cut-off of 15°–18° are applicable in natural systems. Identifying depositional setting to infer depositional process in river-mouth system and analyzing the plane geometry of sandbodies are two steps in the interpretation of ancient fan deltaic rock record.

The Effect of Weathered Layer Thickness and Slope on Potential Areas of Landslides in Gerbosari Village, Samigaluh District, Kulonprogo Regency, Indonesia

Gerbosari Village has a history of landslides with intensity and risk of 56 occurrences over 5 years. Gerbosari Village, Samigaluh District, Kulonprogo Regency is located at geographic coordinates 7◦ 38 '45.33 "- 7◦ 41' 35.24" LS and 100◦ 9 '20.80 "- 110◦ 11' 16.52" BT with topographic conditions at an altitude around 500 - 1000 mdpl. This study aims to determine the subsurface structure of landslide-prone areas in the form of weathered layer thickness and the effect of slope in landslide-prone areas so that it can be used in making micro zonation maps of landslide-prone areas. This study uses 43 microtremor data with a distance between points of 650 m. The microtremor signal was analysed using the horizontal to vertical spectrum ratio ( HVSR) method. From the measurement results, it is obtained that the value of the dominant frequency ranges from 1 - 22 Hz, the value of the amplification factor is obtained in the range of 1 - 10.5, the value of the peak ground acceleration ranges from 60 - 300 cm/s2, the thickness of the weathered layer is obtained in the range of 12 - 22 meters. Based on the results of the slope analysis, the study area is on a slope classified as a bit steep - very steep.

Morphometric Analysis for Sustainable Development of Watersheds Using Multisensor Satellite Data: A Case Study from Shiriya River Basin

Objectives: The goal of this research is to calculate, compare and analyze the morphometric drainage parameters of Shiriya River Basin (SRB), Kasaragod, Kerala, using DEMs acquired by different satellite sensors and topographic data (SOI toposheet) for sustainable watershed development. Methods: The Arc GIS 10.3.1 software was used to measure linear, relief, and areal aspects of morphometry. The input data used for deriving the drainage network of the SRB were SOI toposheet (1:50000 scale), SRTM DEM (90m), Cartosat, ASTER and ALOS PALSAR DEM of resolution 30 m each. The relative error percentage of basic parameters derived from DEMs concerning the toposheet is calculated. A groundwater potential map is prepared using weighted overlay analysis of thematic layers (geology, geomorphology, slope, drainage density, lineament density and depth to water level). Findings: Present study revealed that the parameters derived from SRTM DEM data are more similar to those derived from toposheet. Most of the parameters obtained from each input DEM are more or less equal, and the minor variation may be due to varied data collecting and processing methodologies used for DEM creation. SRB is characterized by 6 th order stream with a dendritic drainage pattern, which is elongated and less susceptible to soil erosion. SRB has an intermediate texture and is in a mature stage of geomorphic evolution. Inference from the ground water potential zonation map indicates that major portion of the SRB has moderate ground water potential. Application/improvement: The study would be a valuable source for identifying water recharge sites, basin modelling, and groundwater prospect mapping. Novelty:This research has attempted to compare and analyze the morphometric parameters’ results from multisensor satellite data for sustainable watershed management. An attempt has been done to understand the relation between morphometric parameters and ground water potential of SRB using Groundwater potential zonation map. Keywords: Drainage morphometry; Shiriya River basin; GIS; Karnataka; Kerala

Numerical Modelling of a One-dimensional Dam Break Using a Slope-Limiting Positivity-Preserving Discontinuous Galerkin Method

The shallow water equations have been widely used to simulate dam-break problem. Due to the nonlinear and discontinuous nature of the event, application of numerical methods is often plagued with problem such as oscillation and unphysical solutions. The aim of this paper is to simulate a one-dimensional dam break using an improved Discontinuous Galerkin Method. The governing equation is discretized using linear shape function and explicit third-order Runge-Kutta. Problem with negative water depth due to wetting and drying is treated using a combination of thin water layer and min-mod slope limiting techniques. The use of these techniques prevents solution blow-out and oscillation especially at the wet-dry interface. Comparison with available analytical solution shows excellent agreement without under and over-shooting of the solution. Convergence study demonstrate that the overall accuracy of the method is consistent with the shape function order. The method is promising as it can easily be extended to higher order and can be used as an alternative to typical method such as Finite Volume.

Numerical simulation of layered anti-inclined mining slopes based on different free face characteristics

Numerical simulation of layered anti-inclined mining slopes based on different free face characteristics

Feasibility Analysis on the Support of Rock Slopes Against Flexural Toppling Failure Using the DDA Method-A Case Study

As a typical and complex failure type of rock slopes, flexural toppling failure has increasingly received attention, mainly focused on its failure mechanism and introducing a proper numerical method to reproduce the failure phenomena. However, there are few studies related to the supporting mechanism against flexural toppling failure. This study attempted to make a preliminary analysis on the research gap. For this purpose, an anti-dip layered rock slope supported with anchor cables that failed owning to flexural toppling was taken as an example, and the numerical method discontinuous deformation analysis (DDA) was taken as the major analytical tool. Firstly, the rationality of DDA was verified by correctly simulating the failure state of the anti-layered rock slope and the underlying failure mechanism was studied. The results indicated that the lack of the support from slope toe is the crucial factor inducing the flexural toppling failure, which posed a great obstacle to the further excavation of the open-pit mine. Secondly, by introducing the anchor cable support to the slope toe in the DDA model, the interaction mechanism between the anchor cables and the rock slope was investigated. the results indicated that the supporting system of the ordinary anchor cables is very sensitive to the inhomogeneous flexural toppling deformation. The tension values of the anchor cables are very inhomogeneous, and once some of anchor cables beyond their tension limit, the anchor cables failed, which will greatly threaten the safety of the adjacent anchor cables and even the stability of the whole slope. Meanwhile, a novel anchor cable called constant-resistance-large-deformation (CRLD) anchor cable was introduced for a comparative study using DDA. just replacing the anchor cables of the original slope with the CRLD anchor cables, the slope can reach stable state eventually even without the slope toe being enhanced. In addition, the CRLD anchor cables were able to support the slope well against the inhomogeneous deformation, because they can provide high constant resistances and withstand large deformations. This study can provide a deeper insight into the support mechanism for the snit-layered rock slope against flexural toppling failure and introduce a novel supporting method for such slopes.

Time-Varying Effect of Ductile Flexural Toppling Failure on Antidip Layered Rock Slope

Ductile flexural toppling failure is a common form of toppling failure, and it is the product of long-term geological history and shows the characteristics of long-term deformation and progressive failure. The creep characteristics of rock mass have been seldom considered in the current research on toppling, especially interlayer creep of rock layers in the process of toppling. Based on the thought of deformation stability analysis, the flexural toppling failure was divided into the following four stages: start-up, rapid deformation, transient stability, and long-term creep stages. Combined with mechanical analysis, the developmental conditions of the start-up, transient stability, and long-term creep development stages are discussed respectively. Finally, several cases were selected to analyze the stage and the stability of the toppling deformation body, as well as to verify the rationality of the mechanical analysis condition. Study results show that the start-up conditions meet Equation 2, the rock layer inclination and slope angle is 0.5π−φ in the transient stability stage, and that angle is the infinite 0.5π in the long-term creep stage. Other external forces (such as water pressure) will intensify the development of ductile flexural toppling failure, so that the angle between the toppled bedding surface and the slope surface increases. It is of great significance to analyze the development stage of the ductile flexural toppling, comprehensively analyze and evaluate the stability of the ductile flexural toppling, reasonably develop and utilize its self-stability ability, and set up support measures.

Features and Formation Mechanism of the Jiaopenba Landslide, Southwestern Sichuan Province, China

The Jiaopenba landslide, which represents a typical large basalt high-speed remote landslide, is located in Emeishan City, southwestern Sichuan province, China. Based on the field investigation, the characteristics of the Jiaopenba landslide have been revealed. The Jiaopenba landslide occurred on the steep Mount Emei. Landslide materials with a volume of approximately 6.75×108 m3 slid down from a high position, forming a large-scale high-speed remote debris flow, with the farthest sliding distance of about 7.5 km. The landslide area is located in the west wing of the Emeishan anticline, which is cut by faults to form a monoclinal fault-block mountain. Although the shear outlet of the landslide is near the slope toe and does not have good free conditions, there are faults passing through the slope toe of the bedding slope of the fault hanging wall, the landslide is affected by the fault activity, and the integrity of the layered slope is poor. When the foot of the slope is empty, the fault zone is compressed and plastic extrusion, which leads to bedding slip of the slope rock mass and greatly weakens the interlayer bonding force. When coupled with long structural planes on both sides to form side crack planes, a large-scale inclined plate structure is formed. Under the action of a strong earthquake and other external forces, the rock mass near the fault can be damaged by tension, and a large-scale high-position landslide can be formed by the mode of compression-slip-tension fracture.

A Reinforcement Learning approach to the location of the non-circular critical slip surface of slopes

We propose a numerical procedure to locate the critical slip surface of slopes with the method of slices. We employ the Deep-Q Learning algorithm with experience replay and target memory to determine a non-circular slip surface. The overall stability analysis is performed with Janbu’s simplified method. Our approach, however, is flexible and can accommodate other Limit Equilibrium Methods. The accuracy of the method is demonstrated by using typical verification examples and comparing the results to the search methods implemented in SLOPE/W and Slide2. It is demonstrated that the Deep-Q learning algorithm can be efficiently applied to layered slopes.

Experimental study on the evolution law of mining‐induced fractures and deformation rock mass structure of gently inclined layered slope

AbstractLandslide induced by underground mining is the main type of geological disaster in Guizhou Province. The spatial position of the mined‐out area is the key factor affecting the deformation evolution of mining landslides. Three typical mining‐induced slopes in western Guizhou Province are selected to establish the engineering geological model. The orthogonal experimental design is carried out with the position of the mined‐out area relative to the slope shoulder (PM) and the slope height (SH) as variables, and the discrete element simulation test is carried out. The influence of the two variables on the evolution of overlying strata fractures and the structure of slope surface deformed rock mass is analyzed by gray relational method. The results show that under the effect of mining, the overlying strata rock on the mined‐out area gradually collapses and produces cracks through the surface. The force chain arch gradually develops from the lower part to the surface rock layer, and the slope surface rock layer is transformed from a cantilever beam embedded at one end to a multisegment articulated beam. Depending on the number of segments of the articulated beam structure, it can be divided into three categories, and the rock mass where the slope collapse occurs is mainly concentrated at the end of the multisegment articulated beam. The central subsidence of the subsidence basin, the length of the end of the articulated beam, the position of the fulcrum, and the rotation angle of the beam structure are the key indicators affecting the stability of the multisegment articulated beam. Gray relational analysis shows that PM is the primary factor to control the output of these indicators. The multiple linear regression model of gray relational degree between PM and SH was constructed, and the prediction formula of gray relational grade was obtained, which realized the multiobjective prediction of the overlying strata rock structure model under the same slope parameters. The results provide the theoretical basis for disaster prevention and mitigation of gently inclined layered mining slopes.

Influence of a Dominant Fault on the Deformation and Failure Mode of Anti-dip Layered Rock Slopes

Toppling is a kind of failure mode that commonly exists in anti-dip rock slopes. Toppling deformation has a great influence on the stability of rock slopes, which often leads to geological disasters such as sliding and collapse of anti-dip slopes. However, a large number of faults and other structural planes will be produced in many rock slopes due to the action of geological structure movement. In the investigation, it is found that there are not only toppling deformation, but also faults and other geological structures in the toppling deformation rock slope. Previous studies have calculated the depth of toppling deformation, which is considered from the development characteristics of toppling deformation itself. In this paper, based on the field investigation of the anti-dip rock slope with bedding faults, the relationship between the depth of toppling deformation and the location of faults is analyzed by three-dimensional discrete element method. When the dominant structural plane and toppling fracture surface exist at the same time, the main factors affecting the failure of the reverse dip rock slope can be obtained by determining the different depths of the two planes. The final failure depth and failure mode of the toppling deformation in an anti-dip rock slope with a dominant structural plane can be preliminarily determined.

Effects of Slope Angle on Toppling Deformation of Anti-Dip Layered Rock Slopes: A Centrifuge Study

To reveal the impact of slope angle change on toppling deformation, this paper takes the dam toppling deformation of Gushui Hydropower Station based at Lancang River as an example, based on which three groups of models with different slope angles are conceptualized and designed. Through the centrifuge test, the evolution of toppling deformation of a counter-tilt layered slope under different slope angles was simulated. The research results show that: (1) The steeper the slope angle, the shorter the cumulative time required for such deformation is, the larger the toppling deformation will be, and it is more likely that multi-stage fracture zones will occur during the toppling process. (2) The toppling deformation process can be summarized as four stages. (3) The toppling deformation mainly occurs above the datum surface of the toppling fracture; the angle between the datum surface and the normal of the layer is between 12° to 16°. This value shall not change as the slope angle changes. (4) The lesser the slope angle is, the more likely the toppling deformed slope will be experience overall slipping instability. while the steeper the slope angle is, the greater the possibility of collapse after the rock mass falls.

Experimental Study of 3D Concrete Printing Configurations Based on the Buildability Evaluation

Different formulations for 3D printable cementitious composites have been developed for extrusion-based printing. However, there is a lack of configuration guides for actual printing operations, which integrate one printable material and one printing system closely. Three testing methods for configuration determination were proposed and tested with three material proportions, with initial setting times of 2, 8, and 13 min, respectively. The building index (BI) measures the layer stacking stability based on the material, scale, and device. The height reduction test (HRT) quantifies the shortening in the height of the printed filaments. The leaning angle (LA) refers to the maximum slope of the stacked layers. In this study, results showed the critical values were (a) 0.167 for the height reduction ratio (HRR), (b) 40° for LA, and (c) 0~19.1, 0~61.1, and 0~99.4 for BI of the three mixtures. They were the meta parameters used to guide the CAD sketching, material development, and printing configurations, including the printing speed and layer height.

Seismic response of stratified rock slopes due to incident P and SV waves using a semi-analytical approach

Based on the theory of elastodynamics and the concept of wave-field separation, a semi-analytical method for the scattering and diffraction of P-SV waves by stratified rock slopes is proposed in this study. The total wave fields are decomposed into the free field with no irregularity and the scattered wave field generated by slope topography. The former is solved directly with the aid of a dynamic stiffness matrix, and the latter is modeled by applying the inclined and horizontal fictitious distributed loads on the corresponding boundaries. Since the methodology is derived from the exact wave equations and the non-singular frequency-domain Green's functions, it can be applied to seismic dynamic response problems for layered slopes with arbitrary incident waves and layer thicknesses, and the presented solutions are high-precision and well-converged. Using a Ricker wavelet as input, the accuracy and effectiveness of the proposed method for both vertically and obliquely incident P and SV waves are fully verified. Taking three actual earthquake records including Taft wave, El Centro wave, and Loma Prieta wave as inputs, several analysis examples are presented. The parametric studies demonstrate that a significant elevation amplification effect can be seen in the ground motion of rock slopes due to the interaction of the upper slope feature with the underlying bedrock half-space. The PGA amplification factor, Fourier spectrum and standard spectral ratio of rock slopes are evidently affected by the slope height, slope angle and shear velocity of the medium. Subsequently, sensitivity analyses are performed on model slopes with varying incident wave frequencies and incident angles to illustrate the broad applicability of the proposed method. Finally, a case study is presented to evaluate the practicality of the presented procedure and highlight the benefits of performing a rapid semi-analytical solution to assess potential hazards of earthquake-induced rock slides.