Permanent Displacement Research Articles

Impact of Soil Properties’ Spatial Correlation Lengths and Inclination on Permanent Slope Displacements Due to Earthquake Excitation

Natural disasters, when and where they occur, often cause serious social and economic consequences, which require an urgent solution to the problem. In particular, Greece, which is characterized by a complex geological structure and intense tectonic stress, has suffered and continues to suffer the consequences of such catastrophic phenomena. Among the various destructive phenomena recorded on the Earth’s surface, two of the most important problems are landslides and land subsidence. The above phenomena may cause, in addition to the serious case of loss of human life, a threat to the social and economic fabric affecting sustainability in general, i.e., the quality of life of an area (destruction of property, filling of reservoirs, blockage of streams and rivers, etc.). In fact, landslides are a phenomenon with enormous social and economic consequences, since apart from the financial burden due to the collapse of a technical project or the interruption of transportation, they are accompanied by the loss of human life. This research examines the stochastic characteristics of a slopes’ stability to investigate the variation range of permanent earthquake movements. More specifically, the influence of inclination as well as the lengths of the spatial correlation of ground are investigated. The method in the present study follows the development of arbitrary fields of soil properties, which follow the Gaussian distribution characterized by autocorrelation lengths lx and ly in the horizontal and vertical directions, respectively, mean value μ, standard deviation σ, and cross-correlation coefficients ρij. The estimation of permanent displacements is performed by the combination of the Local Average Subdivision algorithm and the FLAC software (Fast Lagrangian Analysis of Continua) used in the parametric investigation of this work. The results of this research showed that the spatial correlation of the properties has an important impact on the permanent displacements of slopes caused by strong earthquake excitations.

On the performance-based seismic design of yielding retaining structures

This work summarises recent research on the seismic behaviour of displacing or yielding retaining structures, i.e., structures that can undergo permanent displacements during strong earthquakes without failing. For these systems, energy dissipation on shaking, leading to reduced inertia forces, can be achieved by allowing the activation of ductile plastic mechanisms. These must be correctly identified to guarantee the desired strength hierarchy, and depend on the specific retaining structure under examination. It is shown that the critical acceleration, or the smallest value of acceleration corresponding to the activation of the critical plastic mechanism, is the key ingredient for the performance-based design of yielding retaining structures. In fact, the critical acceleration controls both the maximum internal forces in the structural elements and the magnitude and trend of post-seismic permanent displacements and rotations, required for quantitative serviceability and post-earthquake operability assessment of infrastructures. Based on a clear understanding of the physical mechanisms governing the dynamic behaviour of these systems, pseudostatic limit equilibrium solutions and simplified dynamic methods can be developed for their seismic design. Theoretical predictions are validated against data from reduced scale centrifuge models and results of pseudo-static and fully dynamic numerical analyses. Finally, all the results presented in the paper, including experimental, numerical and theoretical findings, are used to provide suggestions for the performance-based design of retaining structures.

Low energy impact behavior of unidirectional and cross-ply flax/epoxy laminates and comparison with similar glass/epoxy laminates

Unidirectional (UD) and cross-ply flax and glass fiber reinforced composites (FFRC and GFRC)are tested under four out-of-plane low velocity impact loads. A hybrid flax reinforcement was used, denoted UD-mat, which is made of a UD layer of continuous flax fibers bound to a flax fiber mat layer. For the mat binder, two types of short flax fibers are considered: unmodified fibers and refined ones. The laminates made ofrefined fibers show the highest permanent and maximum displacements. Moreover,the peak load for the unidirectional FFRC with refinedfibers is lower than that with unmodified fibers, for example it is 25% lower at 11 J. When comparing with flax fiber laminates, the absorbed energy and energy absorption ratio are on average 40% lower for glass laminates but less damage is observed. Several failure modes are observed in the flax laminates, while the main failure of the glass/epoxy laminates is delamination.

A Methodology to Combine Shaking and Ground Failure Models for Forecasting Seismic Damage to Buried Pipeline Networks

ABSTRACT How does an earthquake affect buried pipeline networks? It is well known that the seismic performance of buried pipelines depends on ground failures (GFs) as well as strong ground shaking (SGS), but it is unclear how the various types of earthquake hazards should be collectively combined, as existing methodologies tend to examine each of the earthquake hazards separately. In this article, we develop a probability-based methodology to consistently combine SGS with three types of GF (surface faulting, liquefaction, and landslide) for forecasting seismic damage in buried pipeline networks from a given earthquake rupture scenario. Using a gas transmission pipeline example, we illustrate how the proposed methodology enables others (e.g., researchers, pipeline operators who manage distribution lines, and consultants) to modularly combine various models such as those for estimating probability of GF, permanent ground displacements, and pipeline fragility. Finally, we compare the proposed methodology against the Hazus methodology to explore implications from considering each hazard one at a time.

Effect of blast induced vibration on coal mine overburden dump slope through discrete element method

Blast induced ground vibration (BIGV) is a serious threat for the coal mine overburden (OB) dump slopes. The problem becomes intricate considering heterogeneity of the OB dump materials. The performance of an OB dump slope under BIGV is investigated considering Voronoi tessellation scheme of universal distinct element code (UDEC) for the heterogeneity of the OB materials. Variations of BIGV, expressed in terms of peak particle acceleration, velocity and displacement, with the density of explosive and the distance of OB dump slope from the blasting source are comprehensively reported considering single-benched as well as double-benched OB dump slopes. Nonlinear dynamic analyses are carried out considering the expected BIGV at the base of the OB dump slope and effects of blasting parameters on the performance of the dumps were investigated considering different monitoring points along the surface of the slope. The effects of heterogeneity on the dynamic response of OB dump slopes are also presented in comparison with the homogeneous condition. A comparative study based on the performance of single-benched and double-benched slopes under BIGV is also presented. Finally, the failure state of the OB dumps were inferred from the permanent ground displacement experienced by the slopes considering BIGV. The methodology and the presented results are supposed to be beneficial for the mining authority in framing the safety guidelines for OB dump slopes in coal mines.

Research on Effect Factors of Mechanical Response of Polyethylene Gas Pipeline in Karst Area Based on Element Birth and Death Technique

Abstract Buried gas pipelines in karst area are inevitably affected by the geotechnical activities, which is difficult to resist the permanent ground displacement caused by soil dislocation and surface damage. In this paper, abaqus finite element software has been used to establish a pipe-soil nonlinear coupling model based on element birth and death technique. The influence rules of various sensitive factors on the stress response of gas pipelines are studied. The work presented in this paper can provide a reference for the design and safety of polyethylene gas pipeline crossing the karst area.

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.

Insights into the mechanism of earthquake-triggered landslides in plastic fine-grained soils

This article seeks to investigate the cyclic behaviour of fine-grained soils and clarify the mechanism of earthquake-triggered landslides in this material. Six soils with different plasticity and mineralogy were tested in a series of undrained ring-shear experiments using different stress histories. The obtained results were analyzed in relation to the soil plasticity, clay mineralogy, and soil microfabrics to better understand the main factors leading to failure. It was found that the low-plasticity soil mixtures containing either kaolinite or illite were susceptible to liquefaction, while more plastic soil specimens that contained smectite were resistant to liquefaction. The mechanism of earthquake-triggered landslides and the factors affecting them were discussed, and it was experimentally shown that the failure in plastic fine-grained soils was not driven by the excess pore water pressure. Instead, it occurred mostly due to the large permanent shear displacements developed during cyclic loading.

Permanent displacement characteristics of landslides taking into consideration the frequency and energy behaviour of historical seismic ground motions

Landslides often occur along motorways in earthquake-prone areas, leading to casualties and the loss of property. Most previous studies have applied the simplified Newmark method to assess landslide susceptibility at a regional scale, ignoring the characteristics of local ground motions. In this study, we investigated permanent displacement characteristics of three potential landslide areas along the Dayong Expressway using the rigorous Newmark method that considers the frequency and energy characteristics of historical seismic waves. First, the frequency characteristics of historical earthquakes in the study areas were analysed using the fast Fourier transform method and were adopted as input ground motions in calculating the Newmark displacement. Next, the critical accelerations of the three study areas were computed. Parameters such as the elevation, soil layer thickness and soil strength that are required for critical acceleration calculations were obtained using high-precision ( c. 3 cm) unmanned aerial vehicle mapping technology, drilling operations and laboratory tests. Finally, the Newmark displacement was calculated and the landslide susceptibility of the study areas was evaluated. The results showed that the predominant frequency of historical seismic waves in the study areas was 0.38–3.36 Hz, indicating low-frequency characteristics. The results also indicated that the frequency and energy characteristics of the seismic ground motions significantly influenced the Newmark displacement. The maximum Newmark displacement under different waveforms at Damieju ranged from 2 to 18 cm. Under the most dangerous conditions, all three areas showed a potential for landslides. The maximum Newmark displacement positively correlated with the energy of the predominant frequency. The large-energy and low-frequency characteristics of the seismic wave correspond to a large displacement. The simplified Newmark method when used in regional landslide susceptibility analysis did not reflect this effect and may be unsuitable to determine the size of landslides.

Joint inversion of ocean-bottom pressure and GNSS data from the 2003 Tokachi-oki earthquake

When the 2003 Tokachi-oki earthquake generated a large tsunami off eastern Hokkaido, Japan, it was detected by cabled ocean-bottom pressure gauges (OBPs) installed within the seismic source region. The OBP records included characteristic features of tsunami waveforms in the source region, indicating significant offset due to the permanent sea-bottom displacement, which can provide critical information about the earthquake source. However, no studies have considered the OBP tsunami data observed in the focal region for the source inversion of the Tokachi-oki earthquake. Here, in order to better understand the 2003 Tokachi-oki earthquake source, we estimate the spatial distribution of fault slip by conducting a joint inversion using two different datasets: tsunami data from four OBPs, located in the focal region and about 300 km away to the south, as well as Global Navigation Satellite System (GNSS) data obtained throughout Hokkaido and northern Honshu. Through our joint inversion, we found that the most dominant slip peak is located 40 km northwest from the hypocenter with an abnormally large slip of sim15 m. This large slip may result from releasing a high amount of slip deficit accumulated by a stick–slip patch surrounded by stable slip regions on the southernmost Kuril subduction zone. By comparing the OBP observations and the synthetic tsunami waveforms derived from our fault model and other fault models, we conclude that the OBP tsunami data recorded within the focal region better constrained the magnitude and the location of the slip compared to other geophysical data.Graphical

Investigating the effectiveness of fluid viscous damper in reducing the effect of seismic sequence on steel bending frame designed on type c soil

Aftershocks can always cause the collapse of structures damaged by the main earthquake. In this article, the seismic performance of an 8-story steel bending frame designed in c-type soil was first subjected to the seismic sequence of an earthquake and an aftershock, and then the same building with the addition of a fluid viscous damper (Fluid Viscous Damper) was evaluated. The results showed that the seismic performance of the studied frame under the effect of severe aftershocks with the presence of a liquid viscous damper is very different from the case without FVD. For example, the maximum displacement of the structural floors was reduced by 60% compared to the case without a damper. It was also found that while most of the aftershocks in buildings without dampers cause a significant increase in the permanent displacement of the roof, in the presence of dampers, this amount has decreased significantly, although in general, the damage caused by the effect of aftershocks on the building is much more az It will be from a state in which the structure is only subjected to the main earthquake

Seismic-induced permanent displacement estimation combining acceleration and computer vision measurements

In this study, a seismic-induced permanent displacement estimation technique that combines acceleration and computer vision measurements was proposed. The proposed technique involves installing a vision camera and an accelerometer on a target building, with the vision camera capturing the change in the position of surrounding objects after a seismic event to estimate the permanent displacement of the target building. During the installation, the vision camera and accelerometer were vibrated in a controlled manner using a shaker on the target building. Then, in the absence of any artificial target or prior knowledge of the size of natural targets, an automatic scale factor map was generated, which converts a translation of an image (in pixels) into a physical displacement. After an earthquake, a displacement map was constructed to estimate the relative movement of the target building to the natural targets and then clustered using Gaussian mixture modeling. Finally, the undeformed portions of the natural targets were retrieved to estimate the permanent displacement of the target building with respect to the distribution of the natural target movement. Both indoor and outdoor experiments were conducted to validate the performance of the proposed technique. The results demonstrate the improved performance of the proposed technique compared with the previous technique.

Centrifuge and theoretical study of the seismic response of anchored steel sheet pile walls in dry sand

Displacement-based approaches have been proven to be effective for the seismic design of gravity retaining structures. However, application of these methods to embedded flexible walls, such as anchored steel sheet pile (ASSP) walls, is still an open issue, as the factors affecting the accumulation of permanent displacements of these systems are not fully understood. This paper presents the results of four dynamic centrifuge tests on small-scale models of ASSP walls in uniform dry sand. The experimental results showed that ASSP walls can experience different failure mechanisms depending on their geometry and on the magnitude of accumulated displacements. During the earthquake, the system exhibits an overall increase of its seismic capacity, caused by: (a) progressive mobilisation of the soil passive strength; (b) sand densification; (c) rotation of the walls; and (d) reduction of the retained height. Accounting for these effects in pseudo-static limit equilibrium solutions improved the predictions of both the critical failure mechanism and the maximum internal forces in the structural members. Moreover, it allowed development of an efficient analytical tool for the prediction of the seismic permanent displacements of these systems, based on Newmark's sliding block approach.

Influence of the Displacement Predictive Relationships on the Probabilistic Seismic Analysis of Slopes

Seismically induced landslides can often cause severe human and economic losses. Therefore, it is worth assessing the seismic performance of slopes through a reliable quantification of the permanent displacements induced by seismic loading. This paper presents a new semiempirical relationship linking the permanent earthquake-induced displacements of slopes to one or two synthetic ground motion parameters developed considering the Italian seismicity, and a comparison with existing simplified displacement models is illustrated. Once combined with a fully probabilistic approach, these relationships provide a useful tool for practicing engineers and national agencies for a preliminary estimate of the seismic performance of a slope. In this perspective, the predictive capability of different semiempirical relationships is analyzed with reference to the permanent displacements evaluated for the Italian seismicity assimilating the slope to a rigid body and adopting the Newmark integration approach. The consequences of the adoption of these relationships on the results of the probabilistic approach are illustrated in terms of displacement hazard curves and hazard maps for different slope scenarios.

Development of Hybrid Machine Learning Models for Predicting Permanent Transverse Displacement of Circular Hollow Section Steel Members under Impact Loads

The impact effect is a crucial issue in civil engineering and has received considerable attention for decades. For the first time, this study develops hybrid machine learning models that integrate the novel Extreme Gradient Boosting (XGB) model with Particle Swam Optimization (PSO), Grey Wolf Optimizer (GWO), Moth Flame Optimizer (MFO), Jaya (JA), and Multi-Verse Optimizer (MVO) algorithms for predicting the permanent transverse displacement of circular hollow section (CHS) steel members under impact loads. The hybrid machine learning models are developed using data collected from 357 impact tests of CHS steel members. The efficacy of hybrid machine learning models is evaluated using three performance metrics. The results show that the GWO-XGB model achieves high accuracy and outperforms the other models. The values of R2, RMSE, and MAE obtained from the GWO-XGB model for the test set are 0.981, 2.835 mm, and 1.906 mm, respectively. The SHAP-based model explanation shows that the initial impact velocity of the indenter, the impact mass, and the ratio of impact position to the member length are the most sensitive parameters, followed by the yield strength of the steel member and the member length; meanwhile, member diameter and member thickness are the parameters least sensitive to the permanent transverse displacement of CHS steel members. Finally, this study develops a web application tool to help rapidly estimate the permanent transverse displacement of CHS steel members under impact loads.

One simplified method for seismic stability analysis of an unsaturated slope considering seismic amplification effect

Seismic amplification effect in soil slope is not considered by traditional Newmark method; therefore, there will be some deviation in soil slope seismic stability analysis. In order to determine the effect of seismic amplification effect, a simplified method for unsaturated slope stability evaluation is proposed by coupling the Sweden slice method and Newmark method. Research results show that the seismic amplification effect has a great influence on yield acceleration of the slope while it exerts a little influence on critical slip surface shape; if the seismic amplification effect is not considered, permanent displacement of the slope will be underestimated, and there is potential danger in seismic design of slope engineering. Finally, an unsaturated slope model with 1:20 scale is designed through derivation of similarity law, and progressive failure process of the slope under seismic action is simulated. The results of our proposed method are in good agreement with experimental results, which proves the feasibility of our proposed method. This study can provide a simple and reliable method for evaluating the seismic stability of an unsaturated slope.

Predictive model for seismic displacements of flexible sliding block subjected to near-fault pulse-like ground motions

A post investigation of landslides induced by strong earthquake events in recent years shows that near-fault pulse-like ground motions have a considerable impact on slopes. Accurate evaluation of the stability of slopes under near-fault earthquakes has become a crucial issue in seismic-prone areas. Permanent displacement is widely recognized as an effective index for evaluating the stability of slope. Based on the coupled analysis, an empirical earthquake-induced permanent displacement prediction model was developed. A displacement database of 318 pulse-like ground motions from 50 earthquake events was established. The proposed predictive model is a function of the maximum seismic coefficient-time history (kmax), maximum velocity coefficient of velocity-time history of the k-time history (kv-max), yield acceleration (ky), and period ratio (ratio of the natural period of the slope to the mean period of input motion, Ts/Tm). The dynamic responses (kmax and kv-max) are represented by two different functions. At small period ratios (Ts/Tm≤1.8), it is a function of peak ground acceleration (PGA), peak ground velocity (PGV) and ky. At large period ratios (Ts/Tm > 1.8), it is a function of PGV, Ts and ky. It successfully captured the velocity pulse and long period characteristics of pulse-like ground motions. Compared to the existing model, it is found that the model is more accurate when considering pulse-like ground motions. This prediction model can be used not only for the preliminary evaluation of slope stability but also for probabilistic seismic demand analysis of flexible slopes considering pulse-like ground motion in near-fault regions.

Predicting driving transferred energy: case studies of steel piles

ABSTRACT This paper application of a method developed in Brazil for predicting driving transferred energy. The method was recently developed in Brazil and was used in short piles in 2019. In this more recent paper, it was sought to extend the application of the method to long piles (Pile length > 30 m) in soils of different characteristics. It is based on the pile measurements of permanent and elastic displacements during driving and calibration of the site-specific λ coefficient. The article validates the methodology in a case study of two sites with 159 dynamic tests of steel-driven piles in the cities of Santos (SP) and Itaguaí (RJ). Through calibration of λ, the energy predictions showed a good correlation to those obtained from the dynamic tests. There is an additional contribution to the original author’s analysis – increasing the previous testing database – about the correlation between λ and the pile length, as the study includes piles from 36 to 60 m in length – a range that was not included during the author’s first method evaluation. Its major advantage is allowing effective energy estimations in non‑instrumented piles as it is not practical to monitor every single pile of a construction driving site to assess the transferred energy. The presented method is useful in the practice of driven foundation and its quality control.

Enhanced predictive method for pipeline strain demand subject to permanent ground displacements with internal pressure & temperature: a finite difference approach

Pipelines subject to ground deformations generated by geohazard loads carry high importance on pipeline analysis, design, and assessment due to risk of structural damage or failure. Additionally, internal pressure and temperature variation within an operating pipe induce additional strains in combination with pipe strains generated by ground displacement. In this study, an enhanced predictive method is proposed founded upon methods employed by Zheng et al. (2022) to assess pipeline behaviour subject to permanent ground displacement, while considering effects of internal operating pressure and temperature variation. The finite difference-based method previously proposed for strain analysis of buried steel pipes subject to ground movement ignores the effects of internal pressure and/or temperature loading, limiting the applicability of this approach to exclude the operating conditions of pipelines. To address this limitation, the proposed enhanced method accounts for the initial thermal strains and biaxial stress state in the pipe due to hoop stress generated by internal pressure. These additional strains are considered within the expressions of internal axial force and bending moment, derived based on the actual stress distribution on the pipe cross-section. The accuracy of the proposed method is validated against the finite element method (FEM) with respect to results of strain and deformation demand using several indicative case studies. This research provides an effective method of incorporating temperature and internal pressure loads of pipelines subject to permanent ground displacements of varying types, magnitudes, and directions.

Dynamic Reliability Analysis of Layered Slope Considering Soil Spatial Variability Subjected to Mainshock–Aftershock Sequence

The slope instability brought on by earthquakes frequently results in significant property damage and casualties. At present, the research on displacement response of a slope under earthquake has mainly emphasized the action of the mainshock, without accounting for the impact of an aftershock, and the spatial variability of material parameters is often neglected. The spatial variability of parameters is fully accounted for in this paper, and dynamic reliability of permanent displacement (DP) of a slope produced by the mainshock–aftershock sequence (MAS) is studied. A slope reliability analysis method is proposed based on the Newmark displacement method and the generalized probability density evolution method (GPDEM) to quantify the effect of the spatial variability of materials parameters on dynamic reliability. Firstly, the parameter random field is generated based on the spectral representation method, and the randomly generated parameters are assigned to the finite element model (FEM). In addition, the random simulation method of MAS considering the correlation between aftershock and mainshock is adopted based on the Copula function to generate the MAS. Then, the DP of slopes caused by the MAS considering the spatial variability is calculated based on the Newmark method. The impacts of the coefficient of variation (COV) and aftershock on the DP of slope is analyzed by means of mean values. Finally, the effect of COV and aftershock on the reliability of DP is explained from a probabilistic point of view based on the GPDEM. The results revealed that with the increase in the COV, the mean of the DP of the slope shows a trend of increasing gradually. The DP of slope is more sensitive to the coefficient of variation of friction angle (COVF). The mean DP of the slope induced by the MAS is larger compared to the single mainshock, and the PGA has a significant impact on the DP.