One-dimensional Ground Response Analysis Research Articles

Geotechnical assessment of seismicity and liquefaction potential at the Banarli landfill in Tekirdag, Turkey

This study, conducted in the Banarli district of Tekirdag Province, Turkey, focuses on soil reaction analysis and liquefaction potential in an area where a landfill and an associated power plant are planned. The research was examined with a one-dimensional ground response analysis to understand seismic behaviour, revealing the varied responses of soil categories to seismic waves. Soft soil layers were found to lengthen the dominant period of oscillation rather than significantly enhancing peak acceleration during seismic events. Earthquake records specific to the region were crucial for accurate assessments. The study comprehensively assessed liquefaction potential using various estimation methods, including the probability of liquefaction (PL ), liquefaction potential index (LPI), and liquefaction risk index (IR ). Moreover, this study examined liquefaction potential based on Standard Penetration Test (SPT) results, identifying susceptibility in the clayey sand layer at a depth of 3 to 12 meters. Recommendations for soil improvement measures are made to mitigate the risk. This research highlights the need for “customized seismic protocols” and emphasizes the importance of “site-specific assessments” in construction projects. By addressing susceptibility to liquefaction and proposing targeted ground improvement strategies, we contribute to safer and more resilient infrastructure development.

The Influence of Input Motion Scaling Strategies on Nonlinear Ground Response Analyses of Soft Soil Deposits

A key issue for the estimation of ground shaking is the proper selection of input motions at the seismic bedrock. At the same time, the effect of the input motion scaling strategy on structural response is typically studied disregarding the presence of the soil deposit. In this work, different soft soil deposits are selected by varying the shear wave velocity profiles and the depth to the seismic bedrock, modelling the soil behaviour through a nonlinear constitutive model implemented into a fully coupled FE code. Seven input motions are retrieved for several selection strategies in conjunction with two seismic intensity levels. Hence, more than 300 one-dimensional ground response analyses are performed. The results of the analysed cases, which are presented in terms of spectral response at ground surface and amplification factors, indicate that: (i) the use of an advanced elasto-plastic soil constitutive model accounts for nonlinear ground response effects, including higher site amplification in the mid-period range and deamplification of the peak ground accelerations; (ii) the different scaling strategies lead to comparable mean values of the amplification factors, and (iii) the variability of the amplification factors is significantly reduced when the scaling strategy seeks the compatibility with the target spectrum over a specified period range. The research will aid the prediction of local seismic site response over large areas, particularly in the absence of the fundamental period of a structure and facilitate its use in general recommendation for quantifying and reducing uncertainty.

The Filtering Effect of Pile Foundations in Clay

This paper reports the results of a series of centrifuge experiments exploring the dynamic response of pile foundations. The model tested in a centrifuge at 50g consisted of an isolated pile and two pile groups embedded in a kaolin clay, subjected to a sequence of quasi-sinusoidal waves with different amplitudes and frequencies. The results are back-analyzed through a two-step procedure. First, a one-dimensional ground response analysis is performed, in which the small-strain shear modulus is evaluated using data from air hammer tests, while a literature model is used to account for nonlinearity of soil behavior. Second, a three-dimensional finite-element analysis of the model foundations is carried out using the mobilized soil damping ratio and shear modulus determined from the previous step. The aforementioned procedure allowed to reproduce satisfactorily the response of the model foundations tested in the centrifuge, showing that the response of these models is strongly affected by the inertial oscillation of the cap connecting piles necessary to accommodate the measurement devices and to rigidly connect the piles’ heads of the groups. The same numerical model was then adopted to evaluate the change of seismic motion due to pure kinematic interaction effects by setting the pile cap mass equal to zero. This allowed to check the prediction capability of simplified methods of analysis for the evaluation of the base excitation of pile-supported structures. In addition, a number of issues related to the execution of centrifuge tests aimed at investigating the kinematic interaction between pile and soil are highlighted and discussed.

Linear and Equivalent-Linear Direct Transfer of Bedrock Response Spectrum to Free Surface

The aim of this study is to develop a method based on a theoretical background that can evaluate directly the response spectrum of a soil profile at the surface from a specified bedrock response spectrum. One-dimensional ground response analysis is mainly performed using linear (L) and equivalent linear (EQL) method. The interesting feature of this method is its possibility to evaluate, directly, the response spectrum of a soil profile at the surface, without the need of using the power spectral density or the Fourier amplitude spectrum. The results of the proposed method showed a good agreement compared with those obtained from the Shake software and from the random vibration theory (RVT) used in the Strata software.

Analysis of Multilayered Ground Amplification Characteristics by Scaled-Down Model Tests

During an earthquake, seismic waves travel through different media through the source to reach the surface. It is very necessary to study the dynamic characteristics of soil between different layers during earthquake. In order to explore the dynamic characteristics of soil under the action of ground seismic input motion, scaled-down model tests were carried out through 1 g shaking table tests based on a laminar shear box. After creating a dense lower ground with a sample of mixed silica and silty soil, and a loose upper ground with sand, the acceleration was measured by applying seismic loading through the 1 g shaking table test. Through the Peak ground acceleration, Spectral acceleration and Spectral acceleration amplification factors, the magnification variation and differences of each depth of the model and the dynamic characteristics of soil between different layers were displayed. In order to verify the reliability of the experimental data, a one-dimensional ground response analysis was carried out using DEEPSOIL software. The approximate results obtained by comparing each other can provide a basis for the accuracy of the experimental results.

How well can we predict earthquake site response so far? Site-specific approaches

Earthquake site responses or site effects are the modifications of surface geology to seismic waves. How well can we predict the site effects (average over many earthquakes) at individual sites so far? To address this question, we tested and compared the effectiveness of different estimation techniques in predicting the outcrop Fourier site responses separated using the general inversion technique (GIT) from recordings. Techniques being evaluated are (a) the empirical correction to the horizontal-to-vertical spectral ratio of earthquakes (c-HVSR), (b) one-dimensional ground response analysis (GRA), and (c) the square-root-impedance (SRI) method (also called the quarter-wavelength approach). Our results show that c-HVSR can capture significantly more site-specific features in site responses than both GRA and SRI in the aggregate, especially at relatively high frequencies. c-HVSR achieves a “good match” in spectral shape at ∼80%–90% of 145 testing sites, whereas GRA and SRI fail at most sites. GRA and SRI results have a high level of parametric and/or modeling errors which can be constrained, to some extent, by collecting on-site recordings.

Closure to “Epistemic Uncertainty in Site Response as Derived from One-Dimensional Ground Response Analyses” by Jonathan P. Stewart and Kioumars Afshari

Closure to “Epistemic Uncertainty in Site Response as Derived from One-Dimensional Ground Response Analyses” by Jonathan P. Stewart and Kioumars Afshari

Discussion of “Epistemic Uncertainty in Site Response as Derived from One-Dimensional Ground Response Analyses” by Jonathan P. Stewart and Kioumars Afshari

Discussion of “Epistemic Uncertainty in Site Response as Derived from One-Dimensional Ground Response Analyses” by Jonathan P. Stewart and Kioumars Afshari

Epistemic Uncertainty in Site Response as Derived from One-Dimensional Ground Response Analyses

One-dimensional ground response analyses (GRAs) are often used with an expectation that they provide unbiased estimates of site effects. Under that hypothesis, epistemic uncertainty in site response arises mainly from uncertain soil properties. This approach has dominated practice for projects where site-specific site response is estimated for use in probabilistic seismic hazard analyses. We extend the uncertainty framework to also consider modeling errors (i.e., inability of GRAs to model site response for some sites). We quantify this epistemic uncertainty using vertical array data in which the downhole motion is input to GRAs to predict ground motions at the surface. Residuals (i.e., difference between observed and predicted ground motion intensity measures in natural log units) are partitioned into between- and within-site components. After correcting for overprediction bias near the site period, we quantify epistemic uncertainty using between-site standard deviation, which ranges from 0.2 to 0.35 using California data. A Japan data set analyzed in the literature provides similar results. This dispersion is only modestly smaller than the site-to-site variability from ergodic models for active tectonic regions, which limits the apparent benefits of site-specific GRAs. Dispersion results are not appreciably affected by varying damping models, although a model informed by site-specific observations minimizes bias relative to alternative models based on geotechnical laboratory tests and seismological crustal attenuation studies.

Taxonomy for evaluating the site-specific applicability of one-dimensional ground response analysis

Because one-dimensional (1D) ground response analysis remains the state-of-practice for geotechnical earthquake engineering, one crucial task is to identify whether the response of a site can be modeled well by 1D analysis. In this study, ground response analyses incorporating 1D transfer functions (TF) and the H/V Spectral Ratio (HVSR) technique are carried out for 34 downhole array sites and used to develop a taxonomy that assesses the suitability of 1D analysis for a site. The empirical HVSR is used to identify the first-mode resonant frequency of the site, and the within and outcrop TF are used to distinguish true outcrop-resonances from pseudo-resonances. The taxonomy is focused on capturing outcrop-resonances rather than pseudo-resonances because pseudo-resonances are an artifact of downhole array sites and are not present in the outcropping analysis of non-downhole array sites. Using the proposed taxonomy, 69% of the sites are considered suitable for 1D analysis, which is a much larger percentage than found in other studies. This more favorable result is a direct result of considering only true-resonances in the assessment of 1D applicability. This taxonomy system is developed using downhole array data but it can be applied to any site (even non-downhole array sites) in which the empirical HVSR curve and shear wave velocity profile are measured, making it easily applied in engineering practice.

Seismic behaviour of soft clay and its influence on the response of friction pile foundations

In recent years, much of the research in geotechnical earthquake engineering has focused on liquefaction of loose, saturated sands and silts. However, the dynamic behaviour of soft, clayey soils and their interaction with pile foundations during the earthquakes have received relatively little attention. In this study, an attempt is made to investigate the dynamic behaviour of soft clay and its interaction with pile foundations during earthquakes using high gravity centrifuge testing. A model single pile and two sets of 3 × 1 row model pile groups with different pile spacing were embedded in soft kaolin clay and tested under the action of model earthquakes at 50 times the earth’s gravity. The strength and stiffness of clay were evaluated using a T-bar test and an air hammer device respectively. The focus of this research is to investigate the dynamic response of friction piles in soft clay. However, this depends on the dynamic response of the soft clay layer around the pile. To this end, one-dimensional ground response analysis was performed using DEEPSOIL software to emphasise the importance of non-linear analysis in characterising the seismic behaviour of soft clays. It will be shown that clay response depends both on the earthquake intensity and the shear strength and stiffness of the clay layer. This has a direct bearing on the response of single piles and pile groups, with larger amplification occurring for small intensity earthquakes and attenuation occurring for stronger earthquakes.

Analysis of seismic ground response caused during strong earthquake in Northern Thailand

This paper presents a site-specific analysis of ground response during the Tarlay Earthquake on March 24, 2011 in Northern Thailand. In this study, the NGA (Next Generation Attenuation) models were selected to predict ground motions due to the earthquake event. The equivalent linear and non-linear approaches were employed in the one-dimensional ground response analysis. Furthermore, the spectral responses produced by the equivalent linear and non-linear approaches were compared with the seismic design code of Thailand. The results showed that the ground motion from the NGA models agree with the strong motion parameters of Tarlay Earthquake. Peak ground acceleration (PGA) at ground surface obtained from both equivalent linear and non-linear approaches certainly results in the high amplification factor. In general, the study results could bring an attention to the local engineer to consider the seismic design value for Northern Thailand, particularly if the stronger earthquake happens in the future.

Ground Response Analysis of Cemented Alluviums Using Non-Recursive Algorithm

ABSTRACT Natural or artificial cementation strongly affects stiffness and damping characteristics of soil deposits. In this paper, it is tried to figure out cementation effects on the spectral response using one-dimensional ground response analysis. A constitutive model is applied which is based on separating the mechanical behavior of cemented soil into two distinct parts, soil matrix and cemented bonds. A non-recursive algorithm was used to calculate the nonlinear behavior of horizontally multilayered soil in frequency domain. The model was verified based on recorded acceleration time histories at sites with cemented alluviums and the results showed good consistency.

Mapping surface motion parameters and liquefaction susceptibility in Tribhuvan International Airport, Nepal

ABSTRACTLocal site effects and liquefaction are major causes of building and lifeline damage in Kathmandu Valley as depicted by several historical earthquakes including recent 2015 Gorkha earthquake (Mw 7.8). Critical facilities like airports play important role in post-earthquake relief, response and recovery efforts. Tribhuvan International Airport (TIA) is the only international airport in Nepal that is located in alluvial soil deposit regarded as Gokarna formation. To assess the site effects and liquefaction occurrence in TIA, this study performs one-dimensional ground response analysis as well as liquefaction susceptibility analysis using shallow borehole logs. Surface motion parameters estimated from one-dimensional ground response analysis are mapped for 0.3g and 0.5g peak ground acceleration inputs. In addition to this, qualitative liquefaction susceptibility map is prepared considering the liquefaction potential index estimated for each borehole log.

Seismic active earth pressure on bilinear retaining walls using a modified pseudo-dynamic method

BackgroundProper understanding of seismic behavior of retaining structures is crucial during a strong earthquake event. In particular, response of retaining walls with bilinear backface, where a sudden change in the inclination along its depth make the problem more complex. This study focuses on estimating the seismic earth pressure coefficients of a retaining wall with bilinear backface using a modified pseudo-dynamic method.MethodsIn this method, the backfill soil is modeled as a visco-elastic Kelvin–Voigt material. A frequency-dependant amplification function is derived for the waves traveling along the backfill using well-established one-dimensional ground response analysis theory. A rigorous parametric study has been carried out to understand the effect of various parameters such as amplitude of base acceleration, direction of vertical acceleration, soil shear resistance angle, soil-wall friction angle, wall inclination, frequency ratio, and damping ratio on the seismic active earth pressure.ResultsIt has been observed that the damping ratio of the backfill soil plays an important role, particularly when the frequency of wave is close to the natural frequency of the backfill. Further, the seismic active thrust is found to increase in both upper and lower segments of the wall when the frequency of the primary wave is greater than that of the shear wave. Comparison of results with the previous studies indicates that the conventional pseudo-dynamic methods significantly underestimate the seismic coefficients and seismic pressures, particularly for the high-intensity motions.ConclusionsThe results of the study show that the natural frequency and damping of the backfill soil have significant effect on the seismic active earth pressure coefficients. Comparison with conventional pseudo-static and pseudo-dynamic methods indicates that the previous methods largely underestimate seismic coefficients and seismic pressures (as much as 48%). This under-estimation is more prominent for higher-intensity motions and less-damped soil, where the soil amplification effects pose most importance. This modified pseudo-dynamic approach can further be used for design of bilinear retaining structures.

DEVELOPMENT OF SEISMIC MICROZONATION MAPS OF SEMARANG, INDONESIA

The new Indonesian Code for seismic resistance design for building has been issued recently. It follows the concept of Risk-Targeted Maximum Considered Earthquake (MCER). Seismic risk microzonation of Semarang is analyzed using the new concept.  Seismic risk microzonation study for hazard mitigation is also performed for the whole city based on deterministic approach, considering the closes distance fault (Lasem Fault). Interpretation of local site effects is performed by carrying one-dimensional ground response analysis. Depth of bedrock is estimated based on single station feedback seismometer measurement. Geotechnical parameters are interpreted from recent and previous measurements. The result of deterministic microzonation study includes the distribution of surface peak ground acceleration (PGA) and spectral acceleration due to Lasem Fault. The obtained results are compared with the distribution of surface PGA and spectral acceleration obtained through new code. 

Seismic microzonation of a nuclear power plant site with detailed geotechnical, geophysical and site effect studies

This paper highlights the seismic microzonation carried out for a nuclear power plant site. Nuclear power plants are considered to be one of the most important and critical structures designed to withstand all natural disasters. Seismic microzonation is a process of demarcating a region into individual areas having different levels of various seismic hazards. This will help in identifying regions having high seismic hazard which is vital for engineering design and land-use planning. The main objective of this paper is to carry out the seismic microzonation of a nuclear power plant site situated in the east coast of South India, based on the spatial distribution of the hazard index value. The hazard index represents the consolidated effect of all major earthquake hazards and hazard influencing parameters. The present work will provide new directions for assessing the seismic hazards of new power plant sites in the country. Major seismic hazards considered for the evaluation of the hazard index are (1) intensity of ground shaking at bedrock, (2) site amplification, (3) liquefaction potential and (4) the predominant frequency of the earthquake motion at the surface. The intensity of ground shaking in terms of peak horizontal acceleration (PHA) was estimated for the study area using both deterministic and probabilistic approaches with logic tree methodology. The site characterization of the study area has been carried out using the multichannel analysis of surface waves test and available borehole data. One-dimensional ground response analysis was carried out at major locations within the study area for evaluating PHA and spectral accelerations at the ground surface. Based on the standard penetration test data, deterministic as well as probabilistic liquefaction hazard analysis has been carried out for the entire study area. Finally, all the major earthquake hazards estimated above, and other significant parameters representing local geology were integrated using the analytic hierarchy process and hazard index map for the study area was prepared. Maps showing the spatial variation of seismic hazards (intensity of ground shaking, liquefaction potential and predominant frequency) and hazard index are presented in this work.

Elastic and Large-Strain Nonlinear Seismic Site Response from Analysis of Vertical Array Recordings

AbstractStrong ground motions from the Mw=6.6 2007 Niigata-ken Chuetsu-oki earthquake were recorded by a free-field downhole array at a nuclear power plant. Site conditions consist of about 70 m of medium-dense sands overlying clayey bedrock, with groundwater located at 45 m. Ground shaking at the bedrock level had a geometric mean peak acceleration of 0.55g, which reduced to 0.4g at the ground surface, indicating nonlinear site response. One-dimensional ground response analysis of relatively weak motion aftershock data provides good matches of the observed resonant site frequencies and amplification levels, provided small-strain damping levels somewhat larger than those from laboratory tests are applied. Nonlinear ground response analyses of strong-motion data using laboratory-based modulus reduction and damping relations valid up to moderate strain levels (<∼0.5%) produce unrealistic strain localization at a velocity contrast. A procedure is presented to more realistically represent the large-strain por...

Seismic hazard assessment of Chennai city considering local site effects

Chennai city suffered moderate tremors during the 2001 Bhuj and Pondicherry earthquakes and the 2004 Sumatra earthquake. After the Bhuj earthquake, Indian Standard IS: 1893 was revised and Chennai city was upgraded from zone II to zone III which leads to a substantial increase of the design ground motion parameters. Therefore, a comprehensive study is carried out to assess the seismic hazard of Chennai city based on a deterministic approach. The seismicity and seismotectonic details within a 100 km radius of the study area have been considered. The one-dimensional ground response analysis was carried out for 38 representative sites by the equivalent linear method using the SHAKE91 program to estimate the ground motion parameters considering the local site effects. The shear wave velocity profile was inferred from the corrected blow counts and it was verified with the Multichannel Analysis of Surface Wave (MASW) test performed for a representative site. The seismic hazard is represented in terms of characteristic site period and Spectral Acceleration Ratio (SAR) contours for the entire city. It is found that structures with low natural period undergo significant amplification mostly in the central and southern parts of Chennai city due to the presence of deep soil sites with clayey or sandy deposits and the remaining parts undergo marginal amplification.

Constitutive Model for 1-D Cyclic Soil Behaviour Applied to Seismic Analysis of Layered Deposits

ABSTRACT A phenomenological constitutive model, 'BWGG', is developed for the non-linear one-dimensional ground response analysis of layered sites. The model reproduces the nonlinear hysteretic behaviour of a variety of soils, and possesses considerable flexibility to represent complex patterns of cyclic behaviour such as stiffness decay and loss of strength due to build-up of pore-water pressure, cyclic mobility, and load induced anisotropy. It also has the ability of simultaneously generating realistic modulus and damping versus strain curves, by a simple calibration of only three of its parameters. The model is implemented through an explicit finite-difference algorithm into a computer code which perform integration of the wave equations to obtain the nonlinear response of the soil. The code, 'NL-DYAS', is then applied to study the seismic response of a soft marine normally-consolidated clay. The results are compared with those of widely used codes. Finally, the records of the Port Island array during the Kobe 1995 earthquake, are utilized, and the model is shown to “predict” the observed response with sufficient accuracy.