Sloping Layer Research Articles

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.

Upper-Bound Solution for the Stability Analysis of Layered Slopes

Upper-Bound Solution for the Stability Analysis of Layered Slopes

Stability analysis of layered slopes in unsaturated soils

Stability analysis of layered slopes in unsaturated soils

Study on Mechanical Response and Stability Algorithm of Soft and Hard Rock Interbedded Slope Excavation

Based on the actual engineering geological survey, the mechanical response mechanism and sliding surface characteristics of the interbedded slope containing six layers of soft and hard rock during excavation under heavy rain conditions are studied by numerical simulation, and the composite sliding surface stability algorithm of the layered slope is established by using the penalty function. The research shows that, during the excavation, the distribution characteristics of stress, strain, plastic zone, and horizontal displacement along the bedding plane are obvious; the stress is concentrated in the hard rock layer; however, the strain and plastic zone are concentrated in the soft rock layer. When the ratio of the maximum vertical displacement to the maximum horizontal displacement is less than 1.85, the slope will slide. According to the relative position of the soft rock layer and the toe of the slope, the sliding surface of soft and hard rock interbedded slope can be divided into two types, namely, circular‐straight sliding surface and circular‐straight‐circular sliding surface. The verification shows that the composite sliding surface algorithm objectively reflects the destruction of the slope by bedding sliding and can reasonably evaluate the safety of soft and hard rock interbedded slope.

Dynamic simulation patterns and spatiotemporal analysis of land-use/land-cover changes in the Wuhan metropolitan area, China

With the rapid socioeconomic development in China, the competition for space in land-use conversion is getting fierce. The Wuhan metropolitan area, as one of the main areas of modern agriculture and manufacturing, has been significantly affected by urbanization, industrialization, and national development policies, resulting in regional man-land contradiction. In this complex region, scientifically measuring the land-use/land-cover (LULC) dynamics and exploring the spatiotemporal evolution characteristics of the LULC changes are important tasks for local officials and decision makers in the management of urban expansion and land-use planning. In this study, an integrated logistic multi-criteria evaluation (MCE) cellular automata (CA) Markov (logistic-MCE-CA-Markov) model and a geographic information system (GIS) were used to evaluate and predict the LULC changes. The analysis was based on six LULC maps at equal temporal intervals derived from land-use data for 1990, 1995, 2000, 2005, 2010, and 2015, along with topographic spatial layers (elevation and slope) derived from an ASTER digital elevation model. In addition, other spatial variables (points of interest, gross domestic product(GDP), population density, proximity to urban center, and proximity to transportation line) were incorporated in the simulation process. The simulated results obtained by the integrated logistic-MCE-CA-Markov model had a kappa coefficient of 88.582% and a figure of merit value of 27.935%. The results indicated that, under the influence of the various factors, the future land-use pattern of the Wuhan metropolitan area will be clearly transformed. From 2015 to 2025, it is predicted that the area of arable land and woodland will decrease by 1506.152 km2 and 1743.945 km2, respectively, and urban land expansion will mainly come from arable land, woodland, and other construction land. With the enhancement of the human disturbance intensity, the natural landscape patches will become segmented, and the number of individual patches will increase gradually, enhancing the spatial heterogeneity. The simulation results could not only be used to monitor future LULC trends, but could also help local decision makers to provide policy support for land-use planning and management.

Appraising groundwater potential zones using geospatial and multi-criteria decision analysis (MCDA) techniques in Andasa-Tul watershed, Upper Blue Nile basin, Ethiopia

An integrated approach of remote sensing, geographic information system and multicriteria decision analysis of analytical hierarchical process (AHP) were applied to delineate groundwater potential (GWP) zones in Andasa-Tul watershed, Upper Blue Nile Basin, Ethiopia with an area of 1872 km2. Nine GWP influencing thematic layers comprising lithology, lineament density, geomorphology, slope, soil, drainage density, land use/land cover, rainfall and depth to groundwater level prepared from conventional and satellite data were used. The thematic layers and classes within them were given scale values based on literature and experts’ decision by using Satty’s AHP. The thematic layers have been integrated via their weights/rates using weighted overlay spatial function tool of ArcGIS to provide GWP map. The result shows that GWP map comprises 250.8 km2 (13.4%) very good, 132.9 km2 (7.1%) good, 441.8 km2 (23.6%) moderate, 662.7 km2 (35.4%) poor and 383.8 km2 (20.5%) very poor zones. Validation of the GWP map with existing boreholes and springs yield shows 83.8% agreement indicating good accuracy of the method. The map removal sensitivity analysis result reveals that GWP is more sensitive to lithology (mean variation index, 1.92%) and less sensitive to geomorphology (mean variation index, 0.59%). Similarly, from the single layer sensitivity analysis, lithology and slope are found to be more effective parameters, whereas rainfall and depth to groundwater level are less effective variables. The generated GWP map in the study region can be used as important guideline for locating GWP areas for further exploration, planning and management of the groundwater resources.

Study of parameters of nonlinear slope deformation under the action of power and natural factors

Construction planning in complex engineering and geological conditions, which include landslide-prone areas, requires a detailed analysis of the existing state of the slope and the forecast of its behavior depending on changes in natural and technogenic factors. This possibility can be provided only by modeling deformation processes using numerical calculation methods.
 On the example of construction of a three-storey cottage on a landslide-prone slope, the analysis of the operating conditions of existing anti-landslide structures was carried out and their role in ensuring the slope stability was determined.
 The preliminary calculation of the slope stability was performed by the method of round cylindrical sliding surfaces for soils of natural humidity and in water-saturated state. The method of round cylindrical surfaces is a simplified method of calculating the slopes stability, which in the conditions of heterogeneous layered slope leads to the overestimation of its stability. Therefore, to determine the actual NSDT of the slope, the calculation profile was developed, on which several formulations of the above problem were performed.
 The calculation was performed on the basis of the developed methodology presented in the works of the article authors. The stress-strain state (SSS) of the slope is considered using the finite element method (FEM) and its torque circuit. The base is presented in the form of a modified model of fortified soils with the criterion of the limit state of Mises-Schleicher-Botkin. In numerical implementation, the slope on the basis of engineering surveys was presented as a finite-element discrete model with an elemental grid, a fragment of which is a separate engineering-geological element.
 The considered in the article example of the method of calculation of the system «supporting structure-nonlinear base-house» gives the opportunity to give a reliable assessment of the territory state and offer a number of rational measures for its engineering protection, which ensures reliable operation of buildings and structures.

Experimental study of fan delta evolution: Autogenic cycles of fully confined channelized flow and small secondary channelized flows

Fan deltas grow largely through repeated cycles of lobe construction and channel erosion during the period of channelized flow. Although previous studies suggest that variable flood discharge may play a key role in strong erosion and related fully confined main channel formation in fan deltas, analog experiments with constant discharge and sediment supply showed that strong erosional events were cyclic. Understanding erosion cycles is important for land management and flood hazard mitigation. Here, we present flume experiments to investigate the mechanism and controlling factors of fully confined main channel-related erosion under constant discharge conditions. The results reveal that: (1) fully confined main channel-related erosion is triggered by turbulence within stratified fluid in hydraulic jump process. When the topography difference of the fan delta is sufficiently small, the flow direction changed from steeper flanks to the centerline. The flow velocity along centerline increase due to weak viscosity and steep slope of fan delta, changing the subcritical flow to supercritical flow. Supercritical flow transports sediment to the shoreline and is resisted by the standing body of water in the basin, causing the decrease of flow velocity accompanied by hydraulic jump. The turbulence formed in hydraulic jump process triggers the formation of scour hole which erodes the fan delta. (2) Input conditions control the range of the critical slope and frequency of erosion cycles. The critical slope is inversely related to the slope of the discharge and grain size of sediments, whereas it is directly related to the sediment/water ratio. The frequency of erosion cycles is directly related to the slope of substrate layer, discharge and sediment/water ratio. (3) The fan delta evolves under the interaction between the deposition process and topography. Moreover, dynamic equilibrium of experiments including main channel-related erosions and autogenic slope adjustments can be found in natural fan deltas.

Stability evaluation method for assessing bedrock and overburden layer slope (BOLS) under seismic load

Seismic load is a type of dynamic load that can easily induce the failure of the foundation slope. Using the continuum-based discrete element method in continuum mechanics, herein, the rupture degree and permanent displacement are defined and their evaluation steps are proposed. The sensitivity of rupture degree and the permanent displacement of overburden under seismic force are also analyzed. A new stability evaluation method for an overburden layer under seismic load, which considers rupture degree and permanent displacement, is established. The results showed that the overburden layer and the interface between bedrock and overburden are damaged to a certain extent under the action of a small-intensity earthquake (a peak = 0.03–0.06 g), although the overburden surface is not damaged. With the increase of seismic frequency and slope height, the permanent displacement of overburden decreases, although it increases with the increase of peak acceleration and slope angle. Furthermore, duration has little to no influence on the permanent displacement of the overburden under the condition of a small or moderate earthquake. In the case of a large earthquake, the permanent displacement of overburden increases linearly with the increase in duration.

Influence analysis of irregular bedrock surface on failure characteristics of bedrock and overburden layer slope by material point method

Influence analysis of irregular bedrock surface on failure characteristics of bedrock and overburden layer slope by material point method

Dynamic response law and instability mechanism of steep inclined soft-hard interphase bedding slope under strong earthquakes

China has a vast land area with complex topography and landforms, of which the mountain area accounts for more than 60% of the total area. China is located between the Pacific Rim seismic zone and the Mediterranean-Himalayan earthquake zone, causing frequent earthquake disasters. Earthquake-linked secondary disasters cause far greater damage than themselves, and often cause geological disasters such as landslides and slope collapses in mountainous areas. The secondary disaster caused by the earthquake is closely related to the dynamic response of the slope and the dynamic characteristics of the slope. Geological structure of different slopes and the conditions of ground motion loading have different influences on the pressure and stability of the steep layer between soft and hard phases. Therefore, the purpose of this article is to explore the main modes and processes of slope instability induced by strong earthquakes based on the dynamic response characteristics and laws of slopes, to explore the model deformation and failure phenomena during the test, and to analyze the different results of different lithological slope bodies. This article will use the research methods of specific problems and specific analysis to compare the data and draw conclusions. The research results show that under the common slope body, the acceleration of the falling object is different with different angle and height. Therefore, combined with the investigation of the deformation and failure of the slope in the earthquake zone, the dynamic response law of the rock slope is obtained, which provides a reasonable explanation for the collapse of many large landslides during the earthquake, and provides a theoretical basis for the future design of seismic structures and field slope monitoring and protection against disaster. Combined with physical simulation and numerical simulation methods, the instability and damage characteristics and mechanism of layered slopes under strong earthquake conditions are analyzed and demonstrated.

An anisotropic elastoplastic Cosserat continuum model for shear failure in stratified geomaterials

In this article, we formulate an anisotropic elastoplastic Cosserat continua model for shear failure in stratified geomaterials. Considering the dip angle between local and global coordinates of a formation, a Cosserat elastic anisotropy constitutive matrix under plane strain condition is derived, and cohesion anisotropy is reflected using a microstructural tensor combined-stress invariant method. A Cosserat continuum finite element model and consistent algorithm are developed to consider the characteristics of elastic anisotropy, strength anisotropy, and strain softening. The simulation of a stratified geomaterial sample under uniaxial compression condition shows that the elastic anisotropy has an evident influence on the deformation pattern. It is also demonstrated that dip angle could significantly impact macroscopic failure modes, uniaxial compressive strength, and macroscopic equivalent elastic modulus. The stability analysis of a layered slope demonstrates that the strength anisotropy has a considerable influence on the overload safety factor of the slope and can be a trigger of the formation of shear bands in such slopes. Furthermore, the dip angle of the structural plane also affects the stability of the stratified slope, which is controlled by both the block and structural surface. By comparing the numerical results of the classical continuum model and the Cosserat continuum model, it is proved that the numerical model considering the elastoplastic anisotropy and strain softening under the Cosserat continuum theory overcomes the ill-posedness of mesh sensitivity and maintains the well-posedness of the strain localization problem. Thus, the proposed model is useful for modeling shear failure in stratified geomaterials.

Mechanisms and Stabilization Measures of Layered Slope: A Study Case of a Layered Slope in Sichuan, China

Mechanisms and Stabilization Measures of Layered Slope: A Study Case of a Layered Slope in Sichuan, China

A way Analyzing Oxide Layer on an Irradiated CANDU-PHWR Pressure Tube Using an EPMA and X-ray Image Mapping

The oxide layer in samples taken from an irradiated Zr-2.5Nb pressure tube from a CANDU-PHWR reactor was analyzed using electron probe microanalysis (EPMA). The examined tube had been exposed to temperatures ranging from 264 to 306 ℃ and a neutron fluence of 8.9 × 1021 n/㎠ (E > 1 MeV) for the maximum 10 effective full-power years in a nuclear power plant. Measuring oxide layer thickness generally employs optical microscopy. However, in this study, analysis of the oxide layer from the irradiated pressure tube components was undertaken through X-ray image mapping obtained using EPMA. The oxide layer characteristics were analyzed by X-ray image mapping with 256 × 256 pixels using EPMA. In addition, the slope of the oxide layer was measured for each location. A particular advantage of this study was that backscattered electrons and X-ray image mapping were obtained at a magnification of 9,000 when 20 kV volts and 30 uA of current were applied to radiation-shielded EPMA. The results of this study should usefully contribute to the study of the oxide layer properties of various types of metallic materials irradiated by high radiation in nuclear power plants.

A Sensitivity Analysis of the Anisotropy of Hydraulic Conductivity to the Seepage, Deformation and Stability of Anti-dipping Layered Rock Slopes: A Case Study of the Pulang Area in Southwestern China

In this paper, in order to study the influence of anisotropy ratios and anisotropy directions on the seepage, deformations and stability of the anti-dipping layered rock slopes, Geo-studio software was used in this study for the numerical analysis of carbonaceous slate slopes on the unsaturated seepage, fluid–solid coupling, and stability theory in Pulang area. The results showed that the maximum surface water content of the layered rock slopes gradually decreased with increases of the water conductivity anisotropy ratio and decreases in the anisotropy angle of the anti-dipping layered rock slopes. In addition, the rainfall infiltration depths in the middle sections of the slopes were observed to be the most affected by the anisotropy ratio and dip angles of the rock formations. Meanwhile, the bottom sections of slopes were the least affected by the anisotropy ratio and the dip angles of the rock formations. In regard to the anti-dipping rock slopes, it was found that the anisotropy ratio and rock layer dip angles should be considered in the deformation and stability analyses. When the seepage of an anti-dipping layered slope was considered to be isotropic, the safety factors often were overestimated. As the anisotropy ratio decreases and the anti-dipping angles of the layered planes increases, the safety factors of the slopes will gradually decrease. This study provided a feasible scheme for evaluating the seepage, deformations and stability of the anti-dipping layered rock slopes in southwest China’s Pulang area.

Stability Analysis of Layered Soil Slope Using Truncated Pile with Numerical Solution

Stability Analysis of Layered Soil Slope Using Truncated Pile with Numerical Solution

Effects of the undecomposed layer and semi‐decomposed layer of Quercus variabilis litter on the soil erosion process and the eroded sediment particle size distribution

AbstractSimulated rainfall experiments were performed on bare, undecomposed litter layer and semi‐decomposed litter layer slopes with litter biomasses of 0, 50, 100 and 150 g m−2, respectively, to evaluate the effect of the undecomposed layer and semi‐decomposed layer of Quercus variabilis litter on the soil erosion process and the particle size distribution of eroded sediment. The undecomposed layer and semi‐decomposed layer of litter reduced the runoff rate by 10.91–27.04% and 12.91–36.05%, respectively, and the erosion rate by 13.35–40.98% and 17.16–59.46%, respectively. The percentage of smaller particles (clay and fine silt particles) decreased and the percentage of larger particles (coarse silt and sand particles) increased with an increased rainfall duration on all treated slopes, while the extent of the eroded sediment particle content varied among the treated slopes with the rainfall duration, with bare slopes exhibiting the largest variability, followed by undecomposed litter layer slopes and finally semi‐decomposed litter layer slopes. The clay and sand particles were transported as aggregates, and fine silt and coarse silt particles were transported as primary particles. Compared with the original soil, sediment eroded from all treated slopes was mainly enriched in smaller particles. Furthermore, the loss of the smaller particles from the undecomposed litter layer slopes was lower than that from the semi‐decomposed litter layer slopes, indicating that the undecomposed litter layer alleviated soil coarsening to some extent. The findings from this study improve our understanding of how litter regulates slope erosion and provide a reference for effectively controlling soil erosion.

The Influence of Water Balance for Slope Stability on the High Mine Waste Dump

One of the vital parts of mining activity is optimizing the mine waste dump. It means that the capacity needs to be conserved by the various aspects of feasibility study. Hydrogeology is one of the main aspects of mine waste stability that needs to be controlled to ensure slope stability. The research aims to determine the influence of water balance toward mine waste dump stability, especially for inclined basement. The analysis was carried out by distributing the constituent material grain size, mapping of permeability value, determining the water balance behaviour between recharge and discharge, and watering behaviour inside mine waste dump material. It was also about the fragmentation analysis that was carried out to determine the layer of porosity value, while the permeability test was used to examine the rainfall infiltration rate. It is important to decide on the equilibrium water flow between the recharge and the discharge rates to ensure no water accumulates to mine waste dump. The fragmentation analysis results showed that the top layer of the waste is composed of sand-boulder-sized material with porosity towards the contact zone and a little clay. The hydraulic conductivity material values range from 6 × 10–6 m/s and 3 × 10–2 m/s at the top and the bottom layers of mine waste dump. The rainfall and the seepage are interrelated because a rise follows an increase in rainfall in seepage debit. The large permeability difference between the in-situ material and the layer slope is approximately 14°, therefore, the water tends to flow following the contact zone and forms a seepage. Pore pressure can be minimized, and stability of the mine waste dump slope maintained.

A generalized seismic sliding model of slopes with multiple slip surfaces

AbstractEarthquake‐induced permanent displacements of slopes are generally evaluated through the simplified sliding block analyses of a singular coherent mass on a predefined failure plane. However, coseismic landslides may exhibit multiple slip surfaces as a result of earthquake shaking. This study presents a generalized seismic sliding analysis using a column of sliding blocks to model seismic slope failures with multiple slip surfaces. The formulation of the sliding mode equations of the block system is obtained by a rigorous theoretical derivation. Both a rigid soil column associated with an acceleration–time series that is constant with depth, and a flexible soil column considering an acceleration–time series that varies throughout the sliding mass is presented. The conditional yield accelerations and the equivalent seismic accelerations are defined to characterize the complex interplay of the sliding block assemblies. The approach is applied to model the seismic sliding behavior of layered slopes in which failures would likely occur at the interfaces between soil layers with different shear strengths. The effects of input ground motions and soil deposits on the sliding patterns of slopes are investigated. The developed generalized model provides a promising means for evaluating the seismic slope stability by combining a number of seismic failure locations within slopes.

Physical model experiment on failure mechanism and NPR anchor cable control effect of layered counter-tilted slope

Physical model experiment on failure mechanism and NPR anchor cable control effect of layered counter-tilted slope