Response Of Embankment Research Articles

An analytical method for evaluating highway embankment responses with consideration of dynamic wheel–pavement interactions

In this paper, a more realistic vehicle-road-ground coupling model is proposed to evaluate the dynamic responses of highway embankment with consideration of dynamic wheel–pavement interactions. The vehicle is modelled as a multi-degrees-of-freedom (MDOF) system, and the pavement and embankment are treated as two elastic layers resting on a poroelastic half-space soil medium. The dynamic wheel–pavement force is considered by introducing a Hertzian contact spring between the wheel and the pavement. The vehicles and the road-ground subsystem are coupled by displacement compatibility at the wheel–pavement contact area. The dynamic stiffness matrix method is developed to address the road-ground system, and priority is given to a simple formulation based on the principle of spatial Fourier transforms that are compatible with good numerical efficiency and provide quick solutions. Using a FFT (Fast Fourier Transform) algorithm, the numerical results are derived by introducing two typical vehicles. The results show that two peaks of the vertical responses can be observed with increases in the vehicle speed and the wavelength of the pavement unevenness because of resonance in the coupling system. The dynamic wheel–pavement force makes an important contribution to the responses of the embankment, and the influences of the pavement unevenness parameters and pavement rigidity on the dynamic response of the embankment are also significant.

Numerical Evaluation of Earthquake Settlements of Road Embankments and Mitigation by Preloading

AbstractThis article presents an assessment of the effects of pore water pressure generation of the soil foundation on the seismic road embankment response. Numerical simulations were carried out to study the preloading technique as an improvement method for reducing the liquefaction potential and the induced settlements in a sandy soil profile. The analyses showed that the use of preloading reduces the induced settlements mostly because of the increase in lateral confinement in the superficial soil layers that results from an increase of the coefficient of lateral earth pressure at rest (ko). The research also showed that the efficiency of the countermeasure method was limited to cases in which earthquakes produced a liquefaction zone lower than the depth of the overconsolidated soil.

Seasonal differences in seismic responses of embankment on a sloping ground in permafrost regions

Because of its direct influence on the amount of unfrozen water and on the strength of intergranular ice in a frozen soil, temperature has a significant effect on all aspects of the mechanical behavior of the active layer in which temperature fluctuates above and below 0°C. Hence seismic responses of engineering structures such as embankment on a sloping ground in permafrost regions exhibit obvious differences with seasonal alternation. To explore the distinctive seismic characteristics of a railway embankment on the sloping ground in permafrost regions, a coupled water-heat-dynamics model is built based on theories of heat transfer, soil moisture dynamics, frozen soil mechanics, soil dynamics, and so on. A well-monitored railway embankment on a sloping ground in Qinghai–Tibet Plateau is taken as an example to simulate seismic responses in four typical seasons in the 25th service year. The numerical results show that seismic acceleration, velocity and displacement responses are significantly different in four typical seasons, and the responses on October 15 are much higher among the four seasons. When the earthquake is over, there are still permanent differential deformations in the embankment and even severe damages on the left slope on October 15. Therefore, this position should be monitored closely and repaired timely to ensure safe operation. In addition, the numerical model and results may be a reference for maintenance, design and study on other embankments in permafrost regions.

Liquefaction-induced deformation of earthen embankments on non-homogeneous soil deposits under sequential ground motions

Damage of embankments during earthquakes is widely attributed to the liquefaction of foundation soil. Previous studies have investigated the dynamic response of embankments by mainly considering uniform sand foundation and a single earthquake event. However, the foundation of an embankment consists of many sublayers of soil from liquefiable sand to relatively impermeable layer, and during earthquakes a mainshock may trigger numerous aftershocks within a short time which may have the potential to cause additional damage to soil structures. Accordingly, the investigation of liquefaction-induced deformation of earthen embankments on various liquefiable foundation conditions under mainshock–aftershock sequential ground motions is carried out by a series of dynamic centrifuge tests in this study. The liquefiable foundation includes uniform sand profile, continuous layered soil profile, and non-homogeneous soil profiles. Effects of various foundation conditions on embankment deformations are compared and analyzed. From the test results, it is found that the embankment resting on non-homogeneous soil deposits suffer more damage compared to the uniform sand foundation of same relative density. The test results also suggest that the sequential ground motions have a significant effect on the accumulated deformation of embankment.

Determining a suitable material model for simulating embankment responses under blast loading

The results of finite element simulations for an explosive detonated 1 foot above the surface of an earthen embankment dam in New Mexico are presented in this study. The finite element model is constructed with the dynamic analysis software LS DYNA. Two LS DYNA material models (material model 14: soil and crushable foam with failure and material model 78: soil/concrete) are utilized to model the soil of the embankment dam. The responses of the embankment are compared to field values to identify a suitable material model between material model 14 and material model 78. Simulation results of pressure–time history, nodal velocity, and soil displacement are presented for both material models. The results of the simulations are also compared to previous explosive-induced soil cratering studies. It is shown that material model 78 is more suitable for embankment response characterization under blast loading.

Characteristics of dynamic response of the active layer beneath embankment in permafrost regions along the Qinghai–Tibet Railroad

Dynamic response characteristics and stability of embankment are of primary importance for railroad operation in permafrost regions. The strong motion tests are carried out on a traditional sand gravel embankment at the Beilu River segment along the Qinghai–Tibet Railroad, and the acceleration waveforms at the shoulder and the slope toe of the embankment, when passenger train and freight train pass, are collected through strong motion tests. There is an obvious attenuation effect during the waveform transfer process from the shoulder to slope toe, and the natural frequency of the embankment is between 30–40Hz. Based on the tests in situ, the nonlinear dynamic finite element analysis is applied for numerical simulations on dynamic response of the traditional sand gravel embankment to train load, and the influences of underlying active layer on the dynamic response of the embankment at different seasons are analyzed. The results show that the vibration attenuation of the train load is obvious at different seasons, which presents a linear decrease tendency in summertime, but a nonlinear decrease tendency in wintertime. Both of the two decrease tendencies mainly occur within the soil layer above the permafrost table, but the attenuation effect in summertime, when the active layer is thawed, is slightly greater than that in wintertime when the active layer is frozen. Soil deformation induced by train vibrations occurs mainly above the permafrost table in summertime, but in wintertime, it mainly occurs above the natural surface. Meanwhile, the amount of deformation at the same location in summertime is far more than that in wintertime.

Deformation Behavior and Dynamic Stress Response of High Railway Embankment under Cyclic Load

The deformation of railway embankment is strictly controlled to ensure the safety of train running. In order to study the engineering behavior of railway embankment, simulation analysis on railway embankment with height of 8 m was carried out. Dynamic loads with amplitudes of 0~50 kPa and 0~100 kPa were imposed. The deformation behavior and dynamic stress response of embankment were studied. The results show that the embankment presents attenuation effect on dynamic stress. The static earth pressure near the top of embankment is enhanced, and the static earth pressure at the bottom of embankment is released. The increase of train load will change the failure mode of embankment. The deformation mode of embankment is in subsidence mode when the amplitude of dynamic load is 0~50 kPa, and deformation mode turns sliding mode when amplitude is 0~100 kPa.

Risk-based flood zoning employing expected annual damages: the Chenab River case study

Flooding proves to be the most devastating and annihilating natural hazard in Pakistan. Existing flood management strategies are riveted primarily to the structural measures that contribute limited loss reduction capability at the national level. Non-structural measures are not part of regular practices, as the adopted design standards, which are probabilistic in nature, are unable to assess their feasibilities. An improved risk-based assessment using expected annual damages (EAD) is introduced in this article for the evaluation of combined impacts. EAD treat the probabilistic nature of losses and provide an extended visualization of risk distributions in the form of damage curves and expected annual damages distribution maps. The Chenab River floodplain was selected to study the coalesced response of embankments and flood zoning, preliminary in economic terms. In this regard, the impacts of all likely floods are considered instead of the traditional focus on a single design flood. Damage curves and maps are compiled using estimated losses and probabilities of all floods. Flood zoning for agricultural land is performed. The results support choosing a multidirectional conjunctive approach that considers multiple measures to reduce flood losses. These results can be used as a vital input for the decision-making process.

Dynamic Analysis of the Piled Embankment under Seismic Excitations

Aiming at discussing the behavior of piled embankment under seismic excitations, the numerical analysis model is built by employing ADINA. The interaction of embankment backfill with piles and subsoil is considered. And Coulomb contact pairs based on penalty algorithm is adopted to simulate the contact behavior between pile and soil. Through the varieties of relative displacement and acceleration of embankment structure acted by earthquake loads are analyzed, the weakness of structure is marked and corresponding design suggestion is proposed. It reveals that the displacement and acceleration response of embankment vary non-monotonically, and the peak value of acceleration response of pile firstly increases and then decreases with height of pile, and one of displacement response relative to pile bottom firstly increases and then decreases as well.

A Study to Evaluate the Seismic Response of Road Embankments

A crucial matter related to roads in seismic areas is to ensure viability during the post-seismic stages, especially if the road represents an important or unique way to reach towns that may be potentially hit by strong earthquakes. Verification of road viability under seismic actions requires not only safety assessment of the failure mechanisms which may jeopardize single road components (embankment, viaduct, bridge, etc.) but also evaluation of performance. Viability of a road may be compromised by an unsatisfactory response of road embankments. The vehicle flux may be, in fact, inhibited or reduced if a road embankment suffers global instability mechanisms or significant permanent displacements mainly at the contact with structural elements (e.g., viaducts, bridges) that do not move significantly. In this case the embankment permanent displacements turn out into steps or separations. The paper accounts for the different stages followed to study the seismic performance of the road embankments located along a sample road branch of about 5 km. Preliminary activities consisted in characterizing the geological area of the sample road, in selecting the potentially vulnerable embankments and in carrying out in-situ investigations to properly characterize the physical and mechanical properties of the embankments and foundation soils. A seismological study of the sample area was performed in order to characterize the reference seismic actions needed for the numerical analyses. The seismic response of the embankments was evaluated by a pseudo-dynamic approach and an advanced dynamic model. In the latter, the equations describing dynamic equilibrium and compatibility were merged with an elastoplastic combined-hardening constitutive law that properly models soil response under cyclic loads. The embankment's seismic performance was predicted in terms of permanent settlements at the embankment top surface versus the peak acceleration of the reference input motions.

Comparison between responses of reinforced and unreinforced embankments due to road widening

The objective of this work is to compare the responses of geosynthetically-reinforced embankment and unreinforced embankment due to road widening by using the centrifuge model tests and a two-dimensional (2D) finite element (FE) model. The measured and calculated responses of the embankment and foundation exposed to road widening include the settlement, horizontal displacement, pore water pressure, and shear stresses. It is found that the road widening changed the transverse slope of the original pavement surface resulting from the nonuniform settlements. The maximum horizontal movement is found to be located at the shoulder of the original embankment. Although the difference is small, it is clearly seen that the geosynthetic reinforcement reduces the nonuniform settlements and horizontal movements due to road widening. Thus the reinforcement reduces the potential of pavement cracking and increases the stability of the embankment on soft ground in road widening.

Centrifuge modelling of climatic effects on clay embankments

This paper presents an experimental methodology using a geotechnical centrifuge and an environmental chamber to explore long-term embankment performance in light of the more severe conditions expected due to global climate change. The environmental chamber applies water and air input to control inundation and evaporation conditions at the soil surface. Example results show that a well-compacted intermediate-plasticity model embankment performs well when subjected to 19 years of alternating wet and dry periods. Finally, the paper reports an experimental methodology that will allow further model tests to be conducted to examine how different climate scenarios, soil types and compaction levels may affect long-term embankment response.

Simulating the seismic response of embankments via artificial neural networks

Geotechnical earthquake engineering may generally be considered as an “imprecise” scientific area due to the unavoidable uncertainties and the simplifications adopted during the design process of geostructures. Therefore, relatively accurate predictions using advanced soft computing (SC) techniques can be tolerated rather than solving a problem conventionally. Artificial neural networks (ANNs), being one of the most popular SC techniques, have been used in many fields of science and technology, as well as, into an increasing number of earthquake engineering applications on structures and infrastructures. In this work the implementation of ANNs is focused on the simulation of the seismic response of a typical embankment. The dynamic response of the embankment is evaluated utilizing the finite-element method, where the nonlinear behavior of the geo-materials can be taken into account by an equivalent-linear procedure. In the present study, this extremely time-consuming process is replaced by properly trained ANNs.

Seismic analysis of embankment of Qinghai–Tibet railway

Abstract As far as the railway embankment in permafrost regions is concerned, its mechanical properties are closely related to soil temperature. Especially for the embankment in the warm permafrost regions (mean annual ground temperatures range from 0–− 1.5 °C), its stability will change greatly with minor temperature variations. The Qinghai–Tibet Railway (QTR) is approximately 1142 km long, of which 275 km are underlain by warm permafrost. Furthermore, the Qinghai–Tibet Plateau (QTP) is in an active seismic zone. Thus, the seismic stability, liquefaction, and deformation of the embankment of QTR are critical issues on safe operation. However, there are few papers concerning about the seismic response of railway embankment in permafrost regions. This paper will propose a thermal-dynamic coupled model, and the model and its specific analytical procedure can be described as follows. Firstly, based on the governing differential equations of transient temperature field with phase change, the temperature distributions of railway embankment are computed and analyzed by numerical method. Then, since the mechanical properties of frozen soil are effected by temperature, the dynamic consolidation equations of Biot, whose parameters are relative to temperature, are deduced in detail by adopting dynamic consolidation theory. Lastly, by using this numerical model, the seismic response of the QTR embankment is simulated, and the characteristics of seismic response, such as excess pore water pressure, stress and displacement, are analyzed in detail. Meanwhile, the seismic stability of this embankment is evaluated. The results show that this numerical model is able to simulate seismic response of embankment in permafrost regions.

Local Failures of Embankments During Earthquakes

Seismic damage to embankments has sometimes been found to take place at locally-limited spots even though the foundation conditions are almost the same along their axes. A few studies related to this kind of local failure have been conducted, however the reason why local failures of embankments take place is not known. This paper aims to study the influence of the three-dimensional response of embankments on their local failures. A series of shaking table tests were conducted. Test results revealed that local failures occurred despite the fact that the model base was shaken uniformly. It was also found that the interval of local failures depends on the frequency of input motion and the stiffness of the embankments. Thus, an equation to calculate the intervals of local failures was derived, and this was found to agree well with the seismic damage to the Kushiro River Dike.

Numerical assessment of the seismic response of an earth embankment on liquefiable soils

This study presents a numerical assessment of the seismic behaviour of an earth embankment founded on liquefiable foundation soils during earthquake loading. Analysis was carried out using an effective stress-based, fully coupled, finite element method. The behaviour of the sandy soil is described by means of a cyclic elastoplastic constitutive model which was developed within the framework of the Armstrong–Frederick type non-linear kinematic hardening concept. The numerical method and the analysis procedure are briefly outlined and as an example, the seismic response of an earth embankment on a saturated sand foundation is assessed. Based on the numerical results, the distinctive patterns of seismic response of the embankment are discussed. Special emphasis is given to the computed results of excess pore water pressures, co-seismic and post-seismic deformations, and accelerations during the seismic excitation. It has been found that the numerical model can capture fundamental liquefaction aspects of the embankment foundation system and produce preliminary results for its seismic assessment.

Factors Contributing to Bridge–Embankment Interaction

Seismic analyses typically neglect four important phenomena that contribute to the complex interaction between bridges and approach embankments: three-dimensional embankment response, nonlinear soil behavior, soil-structure interaction, and embankment scattering. To identify the importance of each phenomena, a modeling approach was adopted that can be implemented with commonly available soil and structure properties, and whose computational demands are sufficiently low to perform numerous dynamic analyses. The accuracy of the methodology was established by comparing measured and computed abutment acceleration response histories, response spectra, structural periods, damping ratios, and abutment stiffnesses for several bridges. Parametric studies indicated that, to maintain accuracy over a range of earthquake intensities, it is important to consider three-dimensional embankment effects and to specify soil properties accurately. In contrast, the computed response was nearly insensitive to the effects of embankment scattering and changes in embankment geometry, including the embankment height.

６．地震の力学問題 側方地盤との動的相互作用を考慮した盛土‐支持地盤系の１次元震動解析法

The objective of this paper is to propose a one dimensional analysis method to evaluate the dynamic response of the embankment and support ground system. The system is formulated by the stiffness matrix method. The dynamic interaction with side layered ground is modeled to consider the equilibrium of nodal forces at the interface between the support ground of embankment and the side layered ground. In order to verify the accuracy of the proposed method, seismic response analysis for two dimensional FE model of embankment and support ground is carried out to compare with each analyitical results. It is found that the dynamic interaction is very important to evaluate the dynamic response of embankment.

Performance of Two Reservoirs during 1994 Northridge Earthquake

The 1994 Northridge Earthquake affected two geotechnical structures of the Van Norman Complex, the Los Angeles Reservoir (LAR) and the Power Plant Tailrace, in different ways. Both the Los Angeles Dam and North Dike of the LAR slightly moved and settled, and sustained small superficial cracks. The North Dike underwent a noticeable increase in seepage, without significantly impeding normal reservoir operations. The Northridge Earthquake uplifted and shifted the foundation of the LAR by 30 cm, and provided us with a unique example of tectonic effects on embankments. In contrast to the LAR, which performed well, the nearby rolled fill dike of the Power Plant Tailrace slowly failed by piping due to transverse cracks and differential lateral spreading induced by liquefaction. Both case studies yield valuable information about the response of embankments subjected to near-source ground motion.

Static and dynamic behaviour of soils: a rational approach to quantitative solutions. II. Semi-saturated problems

Negative pore pressures existing in semi-saturated conditions provide a substantial ‘cohesion’ of the soil. This cohesion is of importance in the dynamic response of embankments and dams. The paper extends the formulation presented in part I to problems of semi-saturated behaviour with the assumption of free air ingress. An approximate reconstruction of the failure of the lower San Fernando dam during the 1971 earthquake is presented.