Seismic Slope Stability Research Articles

Systematic calibration of constitutive models for numerical simulation of seismic slope stability

Systematic calibration of constitutive models for numerical simulation of seismic slope stability

Dynamic reliability and seismic fragility analysis for high concrete-faced rockfill dam slopes subjected to stochastic earthquake and parameter excitation via PDEM

The randomness of material parameters and earthquake excitation greatly impacts the seismic stability of high concrete-faced rockfill dam (CFRD) slopes. However, no research has comprehensively analyzed the impacts of stochastic earthquake excitations, random parameters and their coupled effects on seismic stability of CFRD slopes and selected a multi-indicator evaluation criterion to carry out performance-based safety assessment. This paper develops a novel and comprehensive framework for evaluating the seismic stability of CFRD slopes based on the generalized probability density evolution method (GPDEM) with high efficiency and accuracy. The effects of three kinds of randomness on seismic stability of CFRD slopes were comprehensively compared and analyzed on the basis of multi-indices (safety factor (FS), cumulative slip displacement and cumulative time with FS < 1.0). Firstly, the nonlinear shear strength parameters of 40 high CFRDs were statistically collected to obtain the statistical characteristics of rockfill material strength parameters of actual CFRD projects. Secondly, three kinds of random samples were generated using generalized F-discrepancy (GF-discrepancy) method and Spectral expression-Random function (SERF) method. Then, the GPDEM was introduced to combine with three indices to perform the stochastic analysis and reliability evaluation. Finally, the fragility analysis of the CFRD slope was conducted. The results reveal that FS is more sensitive to the ground motions randomness, while cumulative slip displacement and cumulative time with FS < 1.0 are more sensitive to the material parameters randomness. The seismic safety evaluation of CFRD slopes based on multiple indices with full consideration of coupled randomness effects is necessary.

Seismic stability and failure mechanisms of gentle and steep slopes considering soil rotated anisotropy and spatial variability

The present study focuses on investigating the effects of soil rotated anisotropy and spatial variability on slope failure in seismic conditions. The random finite element method aided by subset simulation is implemented, which ensures an efficient quantification of both the probability of failure and its associated consequence of failure. Several slope angles of gentle and steep slopes and soil properties that lead to a low probability of failure were selected for parametric studies. The comprehensive parametric studies of seismic slope stability analysis consider various factors such as slope inclinations, seismic coefficients, scales of fluctuation, and orientations of the major principal scale of fluctuation (i.e., the rotation angle of random field). The results underscore the importance of considering the combined effects of soil anisotropy and the orientation of the major principal scale of fluctuation for designing both gentle and steep slopes under seismic conditions and emphasize that care must be given to ensure the worst-case scenario is considered. Visual observations of failure mechanisms of gentle and steep slopes under seismic conditions were also shown to be very helpful in interpreting the variation of probability of failure due to soil spatial variation.

Analytical Solution for Seismic Stability of 3D Rock Slope Reinforced with Prestressed Anchor Cables

Currently, the study of analytical solutions for the seismic stability of slopes under anchorage conditions is one of the hottest subjects in engineering. In this paper, an analytical solution for the seismic safety of the three-dimensional (3D) two-stage rock slope reinforced with prestressed anchor cables governed by the nonlinear Hoek–Brown criterion was deduced, in which the analyses of seismicity were performed by the latest modified pseudo-dynamic method. This method supplements the consideration of the damping effect of the rock medium on seismic waves, which is more in line with the real seismic situation. A mathematical geometric model was developed for calculating the external forces work and internal energy dissipation acting on 3D rotating rock masses reinforced with prestressed anchor cables, in which the seismic work rate was calculated using a new layer-by-layer superposition summation method. The analytical solution of the safety factor could be collated as an explicit function of several variables, and then, the optimal value was obtained by the Particle Swarm Optimization (PSO) algorithm. To corroborate the accuracy of new analytical solutions, the results were contrasted with those of the pertinent literature. The results of the two comparisons were very close. Ultimately, the sensitivity analyses and coupling effects of seismic pseudo-dynamic factors and prestressing anchorage factors were carried out. It was found that even small seismic intensities had a large effect on the stability of rock slopes with developed joints. Increasing the number of steps and prestressing anchors can effectively improve the stability of rock slopes under seismic effects. The conclusions have significant implications for the anchorage design of the 3D two-stage rock slope as seismic events occur.

Stability Analysis of Seismic Slope Based on Relative Residual Displacement Increment Method

The seismic stability analysis of a slope is a complex process influenced by earthquake action characteristics and soil mechanical properties. This paper presents a novel seismic slope stability analysis method using the relative residual displacement increment method in combination with the strength reduction method (SRM) and the actual deformation characteristics of the slope. By calculating the relative displacement of the key point inside the landslide mass and the reference point outside the landslide mass after each reduction, the safety factor of the slope is determined by the strength reduction factor (SRF) corresponding to the maximum absolute value of the relative residual displacement increment that appears after a continuous plastic penetration zone. The method eliminates interference caused by significant displacement fluctuations of key points under earthquake action and reduces the subjective error that can occur when manually identifying displacement mutation points. The proposed method is validated by dynamic calculations of homogeneous and layered soil slopes and compared with three other criteria: applicability, accuracy, and stability.

Seismic stability of expansive soil slopes reinforced by anchor cables using a modified horizontal slice method

Seismic stability of expansive soil slopes reinforced by anchor cables using a modified horizontal slice method

Application of the principal component analysis–cloud model in the assessment of the seismic stability of slopes

Application of the principal component analysis–cloud model in the assessment of the seismic stability of slopes

Assessment of seismic slope stability of Rangamati Hill Tracts, Bangladesh

Slope stability is an essential aspect of geotechnical engineering. Unstable slopes or stable slopes influenced by external factors may result in a catastrophic disaster called a landslide. In seismically active areas with steep terrain, landslides commonly occur and are regarded as one of the most severe threats. Bangladesh has not suffered any destructive earthquakes in recent years but has a considerable risk of facing such earthquakes owing to its geological conditions. Although slope failures occurring in the Rangamati Hill Tracts of Bangladesh are mainly rainfall-induced, due to the seismic risk in Bangladesh, it is essential to assess earthquake-induced slope failure in vulnerable areas. In this study, the authors analyzed the seismic slope stability at three locations in the Rangamati Hill Tracts using pseudostatic approaches. The pseudostatic approach with the variation in seismic force based on the seismic coefficient was utilized to determine the critical conditions. Using Newmark’s rigid block method, the permanent displacements for various slope conditions were calculated for the Kobe earthquake. The analysis provided crucial insight into the state of the locations. One location has a low factor of safety (FS) value at a slope angle of 30° or greater, whereas the others have a risk of slope failure at a slope angle of 50° or greater. Newmark’s displacement analysis also showed that the slopes at location 3 have the highest displacement at a lower slope angle, with location 1 and location 2 showing relatively better results than location 3. Structural and bioengineered preventive measures are needed in this area to reduce the vulnerability of possible slope failure.

Shear strength and modulus of mine waste rock – Large scale laboratory testing results

This paper presents the sampling and laboratory testing results of mine waste rock consisting of limestone, siltstone, and intrusive materials collected from the Ok Tedi open pit mine in Papua New Guinea. The laboratory tests included specific gravity measurements, index testing, large-scale direct shear tests using a 720 mm square direct shear apparatus, large-scale consolidation tests using a 550 mm diameter consolidation apparatus, and shear wave velocity tests conducted on compressed waste rock samples. The obtained strength values, as well as small and larger strain modulus values, were subsequently compared with existing literature data from the literature. These findings can serve as a valuable reference for mine waste materials with similar lithology, particle size distribution, and stress condition, particularly in the context of static and seismic slope stability designs.

Influence of Loess–Mudstone Strata Structure on Slope Seismic Stability of Loess Plateau in China

The widely distributed loess–mudstone strata structure in the Loess Plateau of China is one of the fundamental reasons for the susceptibility and group occurrence of seismic landslides in the area. This study took the loess landslides induced by the Haiyuan earthquake as a case study. Through extensive field investigations, the loess cover thickness, mudstone dip angle, slope height, and slope angle were chosen as the influencing factors. Together with mathematical statistics and geotechnical tests, two models, one of a loess–mudstone slope and the other of a pure loess slope, were constructed. Their seismic stabilities under different slope angles and slope heights were compared to analyze the influence of the underlying mudstone strata on the loess slope seismic stability. Meanwhile, a sensitivity analysis of these strata factors affecting the seismic stability of the loess–mudstone slope was carried out based on the orthogonal test. The results showed that ignoring the underlying mudstone strata would lead to smaller calculation results than the actual situation. The sensitivity influence of the factors on the loess–mudstone slope seismic stability comprised the slope angle, loess cover thickness, slope height, and mudstone dip angle from high to low.

Parametric Study on the Stability of Slopes Subjected to Earthquake Forces

For thousands of years, engineers have been grappling with slope instability as an issue in geotechnical and geological engineering. Earthquake loading has a great impact in slope stability. The present study is to investigate the impact of various soil properties and slope geometry on FOS in the presence as well as in the absence of seismic loading. Here, pseudo-static methods are used to analyses seismic slope stability under earthquake loading. From parametric studies, present work concluded that the FOS values start to decline drastically with earthquake impact. Moreover, various prediction models have been developed using Multiple Linear Regression (MLR) & Multiple Non-Linear Regression (MNLR) considering all the data. The input data of slope stability estimation consists of the values of soil parameter, slope parameter and earthquake loading parameters. As an output, MLR and MNLR predict FOS values as a function of these parameters. The model is then checked by comparing the results to another ten actual situations. It was found that the predicted FOS using MNLR gives satisfactory results.

Seismic stability analysis of CSG dams considering the effect of tension crack based on genetic algorithm with an improved initial population strategy

CSG dams, which combine the characteristics of both gravity and rockfill dams, have traditionally been evaluated for seismic failure only in terms of tensile failure mode, similar to concrete gravity dams. However, recent studies have indicated that CSG dams may also be vulnerable to slope instability during earthquakes, which has not been sufficiently investigated. This study proposed a method to evaluate the seismic slope stability of CSG dams, which considered the impact of seismic tension cracks. In addition, an initial population strategy for the genetic algorithm (GA) was proposed to improve the process of seismic stability analysis of CSG dams. Using a 100 m high CSG dam as a case study, the seismic slope stability of CSG dams was studied under different ground motions with the proposed method. The results show that there is a potential risk of instability when the ground motion intensity reaches a certain level and the most dangerous slip surface could develop along the seismic tension crack on upstream dam surface. Additionally, the results also indicates that the proposed initial population strategy of GA can improve both efficiency and accuracy of stability analysis for CSG dams.

Seismic Stability and Permanent Displacement of 3D Slopes with Tension Cutoff

Seismic Stability and Permanent Displacement of 3D Slopes with Tension Cutoff

Kinematical Analysis of 3D Seismic Stability of Slopes in Unsaturated and Inhomogeneous Soils Using a Pseudodynamic Method

Kinematical Analysis of 3D Seismic Stability of Slopes in Unsaturated and Inhomogeneous Soils Using a Pseudodynamic Method

Probabilistic seismic slope stability analysis using swarm response surfaces and rotational Newmark sliding model with primary sliding direction

The paper develops an effective and efficient swarm response surfaces to locate the slip surface with minimum critical acceleration, based on which the rotational Newmark sliding displacement is calculated. The corresponding primary sliding direction is determined using the identical critical acceleration from rotational Newmark sliding model. The proposed method is validated against the full search where the slip surface with minimum critical acceleration is located by a large number of trials through a homogeneous soil slope and a spatially variable soil slope. The comparative results have demonstrated that the proposed swarm response surfaces act as an efficient surrogate model with only 0.1% of time effort compared with full search method. Although the critical slip surfaces determined using step-wise procedure and simultaneous procedure can lead to agreeable probability density functions (PDFs) of rotational Newmark sliding displacement D compared to the proposed method, the significant discrepancies in sliding area and primary sliding directions among the three methods have been observed even for homogeneous soil slope. The variations of critical slip surfaces, the sliding area A and primary sliding direction αm should be properly accounted for in seismic slope risk assessment using the swarm response surfaces.

Reliability Analysis of Seismic Slope Incorporating Interactions among Multiple Sliding Blocks Using Imbalance Thrust Force Method in Primary Sliding Direction

This paper proposes a methodology for reliability analysis of seismic slope stability that incorporates interactions among multiple sliding blocks. The primary sliding direction is first determined using the vector sum method and then the imbalance thrust force along the primary sliding direction is calculated using the slice-wise strategy and, finally, the double integration strategy is adopted to calculate the accumulated sliding displacement within the earthquake duration. The interactions among multiple sliding blocks are incorporated by checking the potential of occurrence for each of the multiple sliding modes. The proposed method is applied to a soil slope with two sliding surfaces. The comparative studies demonstrate that the mean and standard deviation of the sliding displacement considering the interaction of multiple sliding blocks are approximately three times larger than that of a single sliding mode, and the COV (mean value divided by standard deviation) of the two are slightly different. For the single sliding mode, the mean and standard deviation of the sliding displacement calculated using the proposed method are about 1/2 of the traditional Newmark sliding block model, and the failure probability obtained by the proposed method is lower than that from the traditional Newmark sliding block model owing to the difference in the sliding direction. The Peak Ground Acceleration (PGA) exhibits a significant effect on the statistics of 10,000 sliding displacements. The interactions among multiple sliding blocks and the PGA are required to be properly considered in seismic slope reliability analysis.

A modified Newmark block method for determining the seismic displacement of a slope reinforced by prestressed anchors

The seismic permanent displacement is an essential aspect to evaluate the seismic stability of slope. The conventional Newmark block method commonly adopts a constant yield acceleration to determine the seismic permanent displacement of slope. In order to reflect a more realistic behavior of seismic displacement, the dynamic kinetic failure mechanism and the instant displacement model of slope reinforced by prestressed anchors in infinitesimal time are established. The time-dependent formula for dynamic yield acceleration is deduced based on upper bound method. A modified method is proposed to determine the seismic permanent displacement within the framework of Newmark block theory. The results are compared with the existing work with regard to the yield acceleration and seismic permanent displacement. Three typical seismic ground motions are performed to study the responses of the anchor force, the dynamic yield acceleration and the seismic permanent displacement. Results show that the anchor force, the dynamic yield acceleration and the seismic displacement all increase continuously during the excitation of seismic ground motion. The anchor causes the yield acceleration to increase, and the seismic permanent displacement to decrease significantly. The conventional method adopting a constant yield acceleration greatly overestimates the seismic permanent displacement.

Seismic dynamic stability of double-slider rock slopes containing tension cracks

Seismic dynamic stability of double-slider rock slopes containing tension cracks

On the seismic response and earthquake-triggered failures of subaqueous slopes in Swiss lakes

SUMMARY Seismically triggered subaqueous mass movements in lakes may generate tsunamis that can cause significant damage on the shore. In this study, we assess the seismic response and stability of subaqueous slopes in Swiss lakes based on recorded seismological data, historical and geological information and geotechnical surveys. We performed seismic investigations at multiple locations in Lake Lucerne using Ocean Bottom Seismometers (OBS). For these locations, we derived ground-motion amplification functions from local and regional earthquakes and horizontal-to-vertical spectral ratios (H/V) from the earthquake and ambient vibration recordings. The results show (1) very high amplification levels, often exceeding values of 50–100 in the frequency range between 1 and 10 Hz, (2) the fundamental frequency of resonance in the range of 0.5–3.5 Hz and (3) laterally variable site response even for closely located stations. We sought also the signatures of non-linear site response in the H/V curves or ground-motion amplification functions but found only weak indicative effects and no clear evidence. This is most likely due to the low levels of ground motion recorded during the OBS campaigns. We conducted back analyses of historical earthquakes in Switzerland with available documental and/or geological evidence of induced (tsunamigenic) subaqueous slope failures in Swiss lakes. The data set of historical events was complemented with a selection of instrumentally recorded earthquakes in Switzerland. For the analyses, we selected multiple sites in Swiss lakes which failed in the past or are prone to failure in the future. We modelled the ground motion at these locations assuming Swiss standard reference rock conditions (vs30 = 1105 m s−1). The modelled ground motion intensity measures (IM) included peak ground acceleration (PGA), peak ground velocity (PGV) and pseudospectral acceleration (PSA) at 0.3, 1 and 2 s. We estimated the minimum ground motion and macroseismic intensity at reference rock conditions required to trigger the failures of subaqueous slopes. In addition, we defined a threshold for the seismic triggering of such failures in terms of moment magnitude (Mw) and epicentral distance (Re) as: $$\begin{eqnarray} M_{\rm w}=2.891+1.904\log_{10}(R_e+5.166)\: {\rm for}\: R_e\ge 3.7\: {\rm km}. \end{eqnarray}$$ Our results are consistent with previous studies based on worldwide observations. Furthermore, we related the modelled ground motions to the Swiss seismic hazard products and estimated the return period of critical ground shaking responsible for triggering subaqueous slope failures (with potential for tsunami generation) to be in the range of 36–224 yr. Finally, based on previously collected geotechnical data (in situ Cone Penetration Testing and laboratory sediment analysis), we determined the most likely values of the seismic coefficient k to be used with the ground motion IMs modelled at reference rock conditions in infinite slope stability analyses to estimate the factor of safety (FS). For PGA, we found a k = 1; for PGV, k = 2; for PSA0.3s, k = 0.6; for PSA1s, k = 2 and for PSA2s, k = 5.5. These estimates are conservative and affected by the trade-off between the thickness of unconsolidated sediments and the slope angle. Thus, we recommend applying them to slopes with a low-to-moderate gradient (&amp;lt;15°) and sediment thickness of more than 2 m.

A general kinematic approach to the seismic stability assessment of slopes

Most of the current studies concerning slope stability assume a toe failure mechanism, which fails to capture the full complexity of slope collapse. In this study, a more comprehensive approach is developed for analyzing seismic slope stability by defining an instability behavior coefficient that considers different failure patterns, including toe, face, and base failure. The proposed coefficient is integrated with a kinematic method of limit analysis to establish a three-dimensional (3D) collapse mechanism that can describe all possible instability behaviors. The impact of earthquake forces on instability behaviors and slope stability is assessed in a modified pseudodynamic manner, which is capable of accounting for the spatiotemporal feature of seismic acceleration. A horizontal slice method is executed for calculating earthquake-induced work rates, as well as a double integral technique to compute dissipation rates due to soil resistance along the sliding surface and work rates generated by soil weight. By applying the principle of energy conservation, the lower-bound solutions of stability numbers are derived, and a further critical solution can be obtained by the combination of the Marine Predators Algorithm and the Nelder-Mead Simplex Algorithm. The proposed method is confirmed to be accurate and effective through comparisons with previous solutions. In addition, a parametric study reveals the effect of the dynamic characteristics of seismic waves on slope stability and instability behaviors. The general approach developed in this study offers a more comprehensive and accurate way to assess seismic slope stability.