Geotechnical Earthquake Engineering Research Articles

Inversion of permanent deformation parameters of neural network based on bee colony optimization algorithm

In this research, a method of artificial bee colony algorithm was proposed to optimize BP neural network parameters and then introduced to parameter inversion of geotechnical engineering. The method is based on the research and analysis of permanent deformation of geotechnical earthquake engineering and aimed at addressing the shortages of BP neural network which is slow to converge and may easily get minimum value. This method not only strengthens the global optimization ability of bee colony optimization algorithm, but also reflects the high accuracy of predicting nonlinear problems of BP neural network and the strong generalization ability. The proposed method also improves the prediction accuracy This new proposed method was validated by using the earthquake data of Zipingpu concrete faced rockfill dam in WenChuan earthquack. The results showed that this method can better solve the problem of permanent deformation parameters and can be extended to inversion predict of the same kind.

A constitutive model for clays and plastic silts in plane-strain earthquake engineering applications

A plasticity model for representing clays and plastic silts, as opposed to purely nonplastic silts or sand, in geotechnical earthquake engineering applications is presented. The PM4Silt model builds on the framework of the stress-ratio controlled, critical state based, bounding surface plasticity PM4Sand model, and is coded as a user defined material for use with the program FLAC. The model was developed to provide reasonable approximations of monotonic undrained shear strength, cyclic undrained shear strength, and shear modulus reduction and hysteretic damping responses. The model does not include a cap, and therefore is not suited for simulating consolidation or reconsolidation settlements (i.e., volumetric strains) or strength evolution with consolidation stress or seismic loading history. The primary input parameters are the undrained shear strength ratio (or undrained shear strength), the shear modulus coefficient, and the contraction rate parameter. All secondary input parameters are assigned default values based on a default calibration, but may be adjusted when calibrating against advanced laboratory test data or performing sensitivity studies. The calibration process is described and illustrated by calibrations for three different normally consolidated, fine-grained soils with plasticity indices ranging from 4 to 20. The model is shown to provide reasonable approximations of behaviors important to many earthquake-engineering applications and to be relatively easy to calibrate.

SPT-based liquefaction assessment with a novel ensemble model based on GMDH-type neural network

Liquefaction is one of the most complex problems in geotechnical earthquake engineering. This paper proposes a novel ensemble group method of data handling (EGMDH) model based on classification for the prediction of liquefaction potential of soils. The database used in this study consists of 451 standard penetration test (SPT)–based case records from two major earthquakes. The input parameters are selected as SPT blow numbers, percent finest content less than 75 μm, depth of groundwater table, total and effective overburden stresses, maximum peak ground acceleration, and magnitude of earthquake for the prediction models. The proposed EGMDH model results were also compared with other classifier models, particularly the results of the GMDH model. The results of this study indicated that the proposed EGMDH model has achieved more successful results on predicting the liquefaction potential of soils compared with the other classifier models by improving the prediction performance of GMDH model.

Numerical simulation and absorbing boundary conditions for wave propagation in a semi-infinite media with a linear isotropic hardening plastic model

The theory of plastic wave propagation finds its applications in many geotechnical earthquake engineering problems. In this paper, a linear isotropic hardening plastic material is chosen to investigate the plastic wave propagation in a semi-infinite media. The dynamic response of a semi-infinite bar subjected to a triangular load is first derived. The numerical modelling scheme is then proposed and verified by the existing and derived analytical solutions. Novel artificial boundary conditions (ABCs), which are designed for transient dynamic analysis of plastic dilatational wave propagation problem in the media with a linear hardening plastic property, are developed and incorporated into the numerical scheme. Numerical examples illustrate the accuracy of the ABCs in reflecting the complex phenomenon of wave interaction, and reveal good absorption of outgoing stress waves. The study outcome provides reference for developing suitable ABCs for media with complicated nonlinear mechanical properties, and will facilitate the numerical technique in solving soil-structure seismic interaction problems.

Modified Pseudo-dynamic Bearing Capacity of Shallow Strip Footing Considering Fully Log-Spiral Passive Zone with Global Center

The subject seismic bearing capacity is one of the most important aspects of geotechnical earthquake engineering. As the existing pseudo-dynamic method has certain drawbacks, this paper presents a modified pseudo-dynamic approach to evaluate the seismic bearing capacity of shallow strip footing resting on c–Φ soil considering the log-spiral failure mechanism. Since damping is present in all materials, more realistic results can be obtained by modeling the soil as a visco-elastic material. Here, the passive failure region is considered a fully log-spiral zone with an arbitrary location of the center of log-spiral. A single seismic bearing capacity coefficient (Nγe) is evaluated for the simultaneous resistance of unit weight, surcharge and cohesion, which is more practical to simulate the field failure mechanism. The effects of soil and seismic parameters are taken into account to evaluate the seismic bearing capacity of the foundation. The results obtained from the present analysis are presented in both tabular and graphical non-dimensional form. Results are thoroughly compared with the existing values in the literature, and a reasonably good agreement is found with the existing studies.

The concrete footing-soil foundation seismic interaction, strain energy and stress mechanism

The seismic stress-strain soil foundation response needs to evaluate with high quality in geotechnical earthquake engineering design. The stress and strain are controllable in soil foundation design. In the present study, the simulated near-fault ground motion has been applied on the model and the seismic resistance of concrete footing to produce shape and magnitude of seismic stress investigated. The main objective of this study is to understand, the concept of strain energy density dissipation mechanism in geotechnical earthquake engineering. The strain energy has been discussed based on results of numerical analysis and those have been reported in the literature. The results have been found that the strain energy density dissipation mechanism meaningfully effects on concrete foundation stress mechanism production and it leads to produce seismic differential settlement mechanism for concrete footing.

A novel ensemble model based on GMDH-type neural network for the prediction of CPT-based soil liquefaction

This study presents a novel ensemble group method of data handling (EGMDH) model based on classification for the prediction of liquefaction potential of soils. Liquefaction is one of the most complex problems in geotechnical earthquake engineering. The database used in this study consists of 212 CPT-based field records from eight major earthquakes. The input parameters are selected as cone tip resistance, total and effective stress, penetration depth, max peak horizontal acceleration and earthquake magnitude for the prediction models. The proposed EGMDH model results were also compared to the other classifier models, particularly the results of the group method of data handling (GMDH) model. The results of this study indicated that the proposed EGMDH model has achieved more successful results on the prediction of the liquefaction potential of soils compared to the other classifier models by improving the prediction performance of the GMDH model.

Numerical Study on the Seismic Response of Fluid-Saturated Porous Media Using the Precise Time Integration Method

The seismic response behavior of fluid-saturated porous media (FSPM) has been a critical subject in the area of soil dynamics and geotechnical earthquake engineering. In this paper, the numerical study of the seismic response of the FSPM is performed based on the u-p dynamic formulation. A time-stepping explicit algorithm for the numerical solution to the u-p dynamic formulation is developed. The precise time integration method is adopted in the algorithm to improve the computational accuracy. The transmitting artificial boundary is used to describe the energy radiative effect of the wave motion in the FSPM. The numerical results indicate that the time-stepping explicit algorithm developed in the current study is applicable and effective for the numerical solution of the dynamic problems of the FSPM based on the u-p dynamic formulation. Furthermore, parametric studies are performed to investigate the effect of the permeability coefficient, elastic modulus of the solid skeleton and porosity on the dynamic response of the FSPM. The analyses show that the permeability coefficient value has a negligible effect on the solid skeleton displacement but has a noticeable impact on the pore fluid pressure. With the decrease of the permeability coefficient value, the peak pore pressure increases remarkably. The elastic modulus of the solid skeleton has an important effect on the solid skeleton displacement and pore fluid pressure. With the decrease of the magnitude of elastic modulus, the solid skeleton displacement and pore fluid pressure increase remarkably. The porosity value has an insignificant effect on the solid skeleton displacement but has a significant impact on the pore fluid pressure. With the increase of the porosity value, the peak pore pressure decreases significantly.

Effects of Uncertainty of Dynamic Shear Modulus Ratio on Design Ground Motion

Based on numerical simulation and the statistics of fine sand layers in the Wuhan area (China), the effects of uncertainty of dynamic shear modulus (due to the limited range of current instruments) ratio on design ground motion were explored. Its effects on design seismic acceleration response spectrum, platform value of response spectrum, and characteristic period of response spectrum were analyzed quantitatively. This study could provide a guideline for the analysis of seismic response as well as theoretical study of nonlinear dynamics on geotechnical earthquake engineering.

Interpretive Structural Modeling and MICMAC Analysis for Identifying and Benchmarking Significant Factors of Seismic Soil Liquefaction

Seismic soil liquefaction is considered as one of the most complex geotechnical earthquake engineering problems owing to the uncertainty and complexity involved in soil parameters, seismic parameters, and site condition factors. Each one of these parameters contains a variety of factors that trigger liquefaction and have varying degrees of importance. However, estimating accurate and reliable liquefaction-induced hazards requires identification and benchmarking of the most influential factors that control soil liquefaction. Seismic soil liquefaction factors were identified by Systematic Literature Review (SLR) approach and analyzed through Interpretive Structural Modeling (ISM) and the Cross-Impact Matrix Multiplication Applied to Classification (MICMAC) methodologies. The ISM model presented the relationships between fifteen seismic soil liquefaction factors and their benchmarking position from higher to lower-level significant factors in hierarchy. MICMAC is used to examine the strength of the relationship between seismic soil liquefaction significant factors based on their driving and dependence power. This research characterizes the identification and benchmarking of the seismic soil liquefaction factors and their relationships. The results show that the factors—duration of earthquake, peak ground acceleration, drainage condition, and standard penetration test (SPT) blow counts—influence seismic soil liquefaction directly and soil type is the governing factor that forms the base of the ISM hierarchy and consequently triggers seismic soil liquefaction. The results provide a more accurate way of selecting significant factors for establishment of seismic soil liquefaction potential and liquefaction-induced hazards risk assessment models.

Analytical solution for vertical site response analysis and its validation

Existing studies for site response analysis in geotechnical earthquake engineering have widely concentrated on the horizontal component of the ground motion. However, strong vertical ground motions have been repeatedly observed, resulting in significant vertical compression damage of engineering structures. Furthermore, for the seismic design of critical structures (e.g. large-scale dams and nuclear power plants), the ground motions in all three directions should be considered. Therefore, there is a need to investigate the site response subjected to the vertical component of the ground motion, especially for the seismic design of critical structures. Consequently, in this study, a numerical program for vertical site response analysis is proposed based on the commonly used analytical transfer function method. The proposed program is then validated against well-documented case studies obtained from the Japanese KiK-net (Kiban Kyoshin network) downhole array monitoring system. Results show that the response spectra at the ground surface are well predicted in the low frequency range (<5 Hz), while discrepancies are observed in the high frequency range. However, the high frequency discrepancies do not significantly affect the overall prediction accuracy, as the overall seismic response of geotechnical structures are usually dominated by low frequency vibrations. Furthermore, the limitations in the analysis are also discussed.

Energy-based evaluation of liquefaction potential of uniform sands

Since behaviors of loose, dense, silty sands vary under seismic loading, understanding the liquefaction mechanism of sandy soils continues to be an important challenges of geotechnical earthquake engineering. In this study, 36 deformation controlled cyclic simple shear tests were performed and the liquefaction potential of the sands was investigated using three different relative densities (40, 55, 70%), four different effective stresses (25, 50, 100, 150 kPa) and three different shear strain amplitudes (2, 3.5, 5%) by using energy based approach. Experiments revealed the relationship between per unit volume dissipated energy with effective stress, relative density and shear strain. The dissipate energy per unit volume was much less affected by shear strain than effective stress and relative density. In other words, the dissipated energy is strongly dependent on relative density and effective stress. These results show that the dissipated energy per unit volume is very useful and may contain the non-uniform loading conditions of the earthquake spectrum. When multiple regression analysis is performed on experiment results, a relationship is proposed that gives liquefaction energy of sandy soils depending on relative density and effective stress parameters.

ЗАБЕЗПЕЧЕННЯ НАДІЙНОЇ ЕКСПЛУАТАЦІЇ НАФТОВИХ РЕЗЕРВУАРІВ У СКЛАДНИХ ГЕОТЕХНІЧНИХ УМОВАХ ПРИ СЕЙСМІЧНИХ ВПЛИВАХ

ЗАБЕЗПЕЧЕННЯ НАДІЙНОЇ ЕКСПЛУАТАЦІЇ НАФТОВИХ РЕЗЕРВУАРІВ У СКЛАДНИХ ГЕОТЕХНІЧНИХ УМОВАХ ПРИ СЕЙСМІЧНИХ ВПЛИВАХ

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.

Effect of the confining method on the cyclic undrained behaviours of sand

Cyclic Simple Shear (CSS) test is widely considered to best simulate vertically propagating shear waves and in-situ stress conditions. CSS test is always performed to generate reliable laboratory data for development and calibration of models in Geotechnical Earthquake Engineering design. Soil sample is laterally confined to simulate in-situ stress condition (k0). Stacked rings (SR) and Wire-reinforced membranes (WR) are the two widely used confining methods. Studies have been conducted on the effect of the two confinement methods on the static behavior of soil. In this paper, the effect of the SR and WR confinement methods on the dynamic soil behavior is studied. Undrained cyclic stress controlled tests were performed on loose and medium dense samples of Ottawa sand laterally confined by SR and WR. The comparison of the tests results showed that the dynamic behavior of the two confinement methods is mostly similar.

Performance based design in geotechnical earthquake engineering

The key elements of performance-based design will be illustrated and discussed in the context of designing cost effective remedial measures for embankment dams with liquefiable materials in the foundation. This situation is considered one of the more challenging areas of performance based design. Some of the key elements that will be considered will be the selection of performance criteria, selection of an appropriately validated analysis program and calibrating the constitutive model to represent material properties in the field. Major elements of performance based seismic design will be explored using typical case histories from practice such as Sardis Dam in Mississippi, Mormon Island Auxiliary Dam in California, and Flood Protection Dikes in Hokkaido, Japan. A primary source of concern about performance based design based on the results of finite element or finite difference methods of analysis is the reliability of the analyses. Reliability is enhanced by due diligence in the selection of a well-validated program and an appropriately calibrated constituted constitutive model. These issues are discussed in the paper, but there remains a residual concern because there is no field response data on large dams by which our real capability can be assessed.

Design and Performance of a Single Axis Shake Table and a Laminar Soil Container

Correct evaluation of shear modulus and damping characteristics in soils under dynamic loading is one of the most important topics in geotechnical engineering. Shaking tables are used for physical modelling in earthquake geotechnical engineering and is key to the fundamental understanding and practical application of soil behaviour. The shaking table test is realistic and clear when the response of geotechnical problems such as liquefaction, post-earthquake settlement, foundation response and soil-structure interaction and lateral earth pressure problems, during an earthquake is discussed. This paper describes various components of the uniaxial shaking table at university of Guilan, Iran. Also, the construction of the laminar shear box is described. A laminar shear box is a flexible container that can be placed on a shaking table to simulate vertical shear-wave propagation during earthquakes through a soil layer of finite thickness. Typical model tests on sandy soil conducted on the shaking table and the results obtained are also presented. Appropriate evaluation of shear modulus and damping characteristics of soils subjected to dynamic loading is key to accurate seismic response analysis and soil modelling programs. The estimated modulus reduction and damping ratio were compared to with Seed and Idriss’s benchmark curves.

Analytical expressions for determining the stability of cohesionless soil slope under generalized seismic conditions

In recent major earthquakes, the researchers have found the need for consideration of vertical seismic acceleration for the stability analysis of the man-made and natural slopes. However, in most past studies, the performance of slopes has been assessed by accounting only the horizontal seismic component of the ground motion, without giving due weightage to the effect of vertical component. In the present study, analytical expressions are derived to determine the factor of safety, yield seismic coefficient and consequently the seismic displacement of cohesionless soil slope under combined horizontal and vertical components of the ground motion. The derivation uses the Newmark’s sliding block approach, in which the soil slope with a planar failure surface within the framework of conventional pseudo-static analysis is assumed to follow the Mohr-Coulomb failure criterion. The effects of vertical seismic coefficient on the stability of cohesionless slope have been studied through a set of graphical presentations for a specific range of soil parameters. It is observed that overlooking the effect of the vertical component of the ground motion on factor of safety and the displacement while designing the slope may be detrimental, resulting in the slope failure. The general expressions presented in this paper may be highly useful in the field of earthquake geotechnical engineering practice for designing the cohesionless soil slopes under combined horizontal and vertical seismic loads.

A generalized VS–N correlation using various regression analysis and genetic algorithm

Shear wave velocity (VS) is an important parameter from geotechnical earthquake engineering perspective. In the absence of the direct measurement of VS, VS–N correlation serves an alternative for evaluating the shear wave velocity (VS) from standard penetration resistance value (SPT-N) at a particular region. In the present study, an attempt has been made to propose generalized VS–N correlation from the globally available correlations for all soil and specific soil type using various regression procedures and genetic algorithm (GA). Various regression procedures along with GA have been used to assess the sensitivity of generalized VS–N correlations in connection with regression methodology. 1D ground response analysis has been carried out at two bore-hole locations in Kolkata city using the VS obtained from generated correlations and site specific response spectra have been generated at those two locations. Finally, performance of some typical buildings have been studied by nonlinear static analysis procedure using those site specific response spectra developed for proposed VS–N relationships for all type of soil and specific type of soil. The performance of the considered typical buildings has been represented in terms of base shear and roof displacement. Chi square ( $$ \chi^{2} $$ ) test has also been conducted to check the confidence level of base shear and roof displacement obtained by using various developed VS–N relationships varies with the results obtained using available site specific relationships proposed by Nath (2016), and it reveals that VS–N relationships developed by GA perform better than the VS–N relationships developed by other regression method.

Development of 1-D Shake Table Testing Facility for Liquefaction Studies

One of the major challenges researchers face in the field of earthquake geotechnical engineering in India is the high cost of laboratory infrastructure. Developing a reliable and low cost experimental set up is attempted in this research. The paper details the design and development of a uniaxial shake table and the data acquisition system with accelerometers and pore water pressure sensors which can be used for liquefaction studies.