The Seismic Response of Two Geotechnically Similar GRS-MB Walls During the Chi-Chi Earthquake: Insights from the Finite Displacement Method

Seismically induced deformations of layered slopes with non-unique and non-planar slip surfaces

Empirical seismic displacement equations based on the Newmark sliding block method are widely used to develop seismic landslide hazard map. Most proposed equations have been developed for embankments and landfills, and do not consider the dynamic response of sliding block. Therefore, they cannot be applied to Korean mountain slopes composed of thin, uniform soil-layer underlain by an inclined bedrock parallel to the slope. In this paper, a series of two-dimensional dynamic nonlinear finite difference analyses were performed to estimate the permanent seismic slope displacement. The seismic displacement of mountain slopes was calculated using the Newmark method and the equivalent acceleration time history. The calculated seismic displacements of the mountain slopes were compared to a widely used empirical displacement model. We show that the displacement prediction is significantly enhanced if the slope is modeled as a flexible sliding mass and the amplification characteristics are accounted for. Regression equation, which uses PGA, PGV, Arias intensity of the ground motion and the fundamental period of soil layer, is shown to provide a reliable estimate of the sliding displacement. Furthermore, the empirical equation is shown to reliably predict the hazard category.

Engineers often use simplified seismic slope displacement procedures to evaluate the seismic performance of earth structures and natural slopes. Current state of practice procedures typically separate the estimation of the ground motion intensity measure ( IM) from the estimate of seismic displacement ( D), given the selected IM hazard level. Thus D is estimated based on a single IM value. A straightforward performance-based seismic slope assessment procedure is proposed, which considers the full range of potential IM values to estimate seismic slope displacements directly related to a hazard level. Seismic performance is assessed through either a Newmark-type seismic displacement estimate or a calibrated seismic coefficient that can be used in pseudostatic slope stability analyses. The procedures were developed for a wide range of earth systems for shallow crustal earthquakes and subduction zone earthquakes. Currently employed simplified slope displacement procedures do not provide consistent assessments of the actual seismic slope displacement hazard. The proposed procedures can be readily used in practice to perform rigorous performance-based seismic slope displacement hazard assessments.

Three-dimensional Seismic Displacement Analysis of Rock Slopes based on Hoek-Brown Failure Criterion

Newmark sliding block models are commonly used for seismic stability analysis of slopes. However, estimation of permanent displacements in conventional Newmark methods is based on a distinct and fixed slip surface which is usually located using a pseudostatic limit equilibrium analysis. By combining a finite element seismic analysis and dynamic programming, this paper first shows that critical slip surfaces within a slope greatly change their shapes and locations over a wide area with time during an earthquake. Then, a modified Newmark analysis is presented in order to consider the effect of variable critical slip surfaces on estimated seismic displacements of slopes. Results of analysis for a hypothetical slope and an actual slope failure caused by an earthquake indicate that the neglect of variation of critical slip surfaces during an earthquake may result in an improper sliding mass and as a result incorrect estimation of permanent displacements. It is also shown that permanent displacement may occur along a relatively wide slip band rather than a distinct slip surface.

ABSTRACTAccurately estimating seismically induced permanent displacement is essential for evaluating the dynamic stability of rock slopes. This study presents an enhanced model aimed at better evaluating the seismic displacement of jointed rock slopes by incorporating topographic amplification effects and the dynamic strength degradation of joints. A pseudodynamic analysis was utilized to model the amplified seismic force acting on the slope. The dynamic degradation law of the joint strength was characterized through the cyclic shear tests and integrated into the proposed model. Seismic displacement for the jointed slopes was obtained by solving the equations of motion, with sliding governed by the Mohr–Coulomb joint strength criterion. The performance of the prediction model was evaluated by comparing its results with those derived from the Newmark method and existing methods. Subsequently, the impact of amplified ground motions and joint strength degradation dependent on displacement and velocity on seismic displacement of jointed rock slopes was examined numerically. The results indicate that the proposed model can directly estimate reasonable seismic displacements of jointed slopes without explicitly specifying the yield acceleration, and it produces more conservative displacements compared to the Newmark method. Findings also emphasize that the amplified ground motion and the dynamic shear strength of joints significantly increase the seismic displacements, implying that neglecting them may lead to an underestimation of the permanent displacement of slopes. This study offers an alternative approach for estimating the permanent displacement of jointed rock slopes, which may provide valuable insights for the seismic design of slope engineering.

As the lifespan of many anchored slope reinforcements in China approaches its end, there is an increased need for secondary reinforcement. This study addresses the interaction between new and existing anchors, a critical but challenging aspect. The study introduces the Anchor Rod Modified Newmark Sliding Block Method (AMNB), which enhances the traditional Newmark Sliding Block Method (NSBM) by incorporating maximum anchor rod tension, dynamic tension changes, and group anchor effects. This improvement enhances the prediction of seismic displacement in slopes with multiple anchors. The AMNB method represents an innovation in slope stability analysis, as it is the first to integrate these dynamic and interactive factors into a unified framework. Validation through comparison with established seismic permanent displacement calculations and the analysis of three typical seismic motions show the AMNB’s effectiveness in capturing dynamic behaviors under seismic excitation. Additionally, numerical simulations using FLAC3D were conducted to validate the proposed method. The results indicate that considering group anchor effects and dynamic tension changes reduces the predicted seismic permanent displacement by up to 10% compared to traditional methods. The proposed AMNB method aligns more closely with the numerical simulation results. The findings indicate that group anchor effects negatively impact anchor forces, dynamic yield accelerations, and seismic displacements, leading to lower anchor tensions and dynamic yield accelerations. This, in turn, results in larger final slope permanent displacements under the same conditions.

The earthquake‐induced displacement of sloping soil mass is an important indicator of co‐seismic landslide initiation. In this paper, an improved Newmark displacement model that considers the accumulation of dynamic pore water pressure (DPWP) in the soil caused by both vertical and horizontal ground motions is proposed. The model can quantitatively describe the dynamic changes of the seismic yield acceleration of near‐saturated infinite soil slopes. Three different types of ground motion time histories are selected to compare the performance of the proposed Newmark displacement model, and the influence of DPWP accumulation on the slope yield acceleration and on the seismic displacement is obtained. The seismic slope displacement analyses indicate that the weakening effect of slope yield acceleration caused by bidirectional earthquake excitation‐induced DPWP is more obvious than when only considering the horizontal ground motion, when the slip surface soils are in near‐saturated state. The effect of initial saturation (Sr0) on the DPWP accumulation caused by vertical ground motion is also investigated. Furthermore, the accumulated seismic displacement can be reasonably explained by the frequency distribution characteristics of the ground motions. Finally, the numerical results of this paper show that the seismic displacement model seldomly considering the effect of DPWP, or only considering the DPWP induced by horizontal ground motion, can significantly underestimate the displacement value when the slip surface soils are in a near‐saturated state.

For the seismic behavior of a rock slope or more specifically a rock wedge, the limit equilibrium method is frequently utilized to determine the static and pseudo-static safety factor, and the Newmark method is usually applied to estimate the permanent dynamic displacement. However, the two methods are relatively complex, which negatively affects their usage in engineering practice. A new idea to analyze the static and dynamic stability of a complex rock slope was provided in this paper by combing the rigid discrete element method (DEM), shear strength reduction (SSR) method, and Newmark method. The research results show that (1) by setting the joint contact stiffness to a very large magnitude, the joint displacement caused by the reduction of joint contact stiffness during the SSR calculation process can be considered ignorable, making the contact behavior between the respective two joints approximately satisfy the rigid-plastic assumption. In this manner, it is feasible to calculate the static and pseudo-static safety factor (SF) and the permanent dynamic displacement of a rock wedge with the rigid DEM. (2) The SF and sliding forces of wedges can be directly calculated by this new method without any auxiliary assumption of motion direction or sliding type. Additionally, the new method is suitable for complex wedges, which is important to practical design. (3) The rigid DEM can be realized in 3DEC, which is testified in this paper by 5 classic static examples and 3 typical dynamic examples. (4) The effect of some important parameters, such as the excitation acceleration amplitude and dip of intersection line between two joints, on the dynamic displacement and SF under dynamic excitation was analyzed. The parameter analysis revealed that evaluating the seismic performance of a rock slope only with the pseudo-static SF would potentially underestimate the seismic displacement, under some special conditions. (5) An example case was presented in this paper that the seismic stability assessment of a block was performed with the proposed approach in terms of seismic displacement. And the slope reinforcement scheme was suggested with respect to exceedance probability. It is noted that the reinforcement scheme obtained from the rigid DEM has a better cost-saving benefit under the same SF. Overall, the knowledge gained in this paper may offer a new idea for the static and dynamic analysis to the rock slope stability.

Seismic slope displacement analyses are crucial for assessing the performance of earth systems and natural slopes under earthquake loading. Input ground motions are important components of such analyses and represent one of the main sources of variability in estimated values of slope displacement. Most studies on seismic slope displacement analyses have been conducted using shallow crustal earthquake motions. However, ground motions from subduction zones are known to have comparatively longer durations. This study proposes a framework to quantify the effects of ground-motion duration on slope displacements using short- and long-duration ground-motion suites from subduction zone earthquakes. Challenges in isolating duration effects from those associated with the amplitude and frequency content of ground motions are overcome by creating sets of ground motions with the same amplitude and similar spectral shape, but with different significant durations. These equivalent short- and long-duration suites of motions are then utilized in nonlinear finite-element analyses to evaluate their impact on slope displacement. The finite-element model is developed to numerically simulate the strength and stiffness degradation of soils under cyclic loading from strong ground shaking. We find that the long-duration motions in our dataset can cause larger permanent displacements compared to their short-duration counterparts (with similar spectral shape but different duration), especially at higher ground shaking intensity levels that can trigger nonlinear soil behavior. Comparisons with simplified analyses show that the simplified methods can result in biased estimates of permanent displacements from the long-duration motions in our study. This study provides a framework to develop ground motion sets that can enable more in-depth investigations of the role of duration on seismic slope displacements and the damage potential of ground motions, particularly from subduction events.

Seismic performance assessment of base-isolated tall pier bridges using friction pendulum bearings achieving resilient design

Nonlinear site‐response analyses are becoming an increasingly important component of simulated ground motions for engineering applications. For regional‐scale problems for which geotechnical data are sparse, the challenge lies in computing site response using a very small number of input parameters. We developed a nonlinear soil model that, using only the shear‐wave velocity profile, captures both the low‐strain stiffness and large‐strain strength of soils and yields reliable predictions of soil response to weak and strong shaking. We here present the formulation of the model and an extensive validation study based on downhole array recordings, with peak ground acceleration (PGA) ranging from 0.01g to 0.9g. We also show that our model, referred to as hybrid hyperbolic (HH), outperforms existing nonlinear formulations and simplified site‐response analyses widely used in practice for ground motions that induce more than 0.04% of soil strain (roughly equivalent to PGA higher than 0.05g). In addition to site‐specific response predictions at sites with limited site characterization, the HH model can help improve site amplification factors of ground‐motion prediction equations (GMPEs) by complementing the empirical data with simulated site‐response analyses for very strong ground shaking, as well as physics‐based ground‐motion simulations, particularly for deeper sedimentary sites with low resonant frequencies.

A fully nonlinear coupled seismic displacement model for earth slope with multiple slip surfaces

Seismic safety analysis of Kukuan underground power cavern

The paper discusses the seismic behaviour assessment of a masonry clustered building, which is a prevalent typology in historical centres, particularly focusing on a case study located in a small town in Southern Italy. Following the introduction about the historical centre, the main architectural and structural features of the selected aggregate are outlined, based on the CARTIS Form, which was developed as part of the DPC – ReLUIS Italian research project. After establishing the characteristics of the building, its seismic assessment is conducted. Non-linear analyses reveal inadequate seismic behaviour in both longitudinal and transverse directions. A consolidating intervention which foresees the application of a seismic coating system is proposed. This integrated approach aims to improve both the seismic and energy performance of the aggregate. In the final part of the work, a comparison is made between the results obtained before and after the intervention. This includes the evaluation of the seismic safety index, as well as the examination of the fragility curves. The objective is to assess the effectiveness of the coating system on the structural units of the aggregate, thereby determining the overall improvement in seismic performance following the intervention.