Influence of Liquefaction and Adjacent Structures on Seismic Response (original) (raw)
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Recent advances in soil liquefaction engineering and seismic site response evaluation
2001
Over the past decade, major advances have occurred in both understanding and practice with regard to engineering treatment of seismic soil liquefaction and assessment of seismic site response. Seismic soil liquefaction engineering has evolved into a sub-field in its own right, and assessment and treatment of site effects affecting seismic site response has gone from a topic of controversy to a mainstream issue addressed in most modem building codes and addressed in both research and practice. This rapid evolution in the treatment of both liquefaction and site response issues has been pushed by a confluence of lessons and data provided by a series of earthquakes over the past eleven years, as well as by the research and professional/political will engendered by these major seismic events. Although the rate of progress has been laudable, further advances are occurring, and more remains to be done. As we enter a "new millenium", engineers are increasingly well able to deal with important aspects of these two seismic problem areas. This paper will highlight a few major recent and ongoing developments in each of these two important areas of seismic practice, and will offer insights regarding work/research in progress, as well as suggestions regarding further advances needed. The first part of the paper will address soil liquefaction, and the second portion will (briefly) address engineering assessment of seismic site response.
Soil-foundation modelling for vulnerability assessment of buildings in liquefied soils
2020
Recent events have demonstrated that earthquake-induced liquefaction can result in significant structural damage and human casualties. The consideration of soil liquefaction has primarily been the domain of geotechnical engineering; however, recent studies have shown a strong interaction between liquefaction-development and the superstructure loads. Not only does liquefaction lead to a change in the shaking demands on the superstructure, it also changes the flexibility of the soil-foundation-structure system. Meanwhile, the high static shear forces from the foundation loads can result in a reduction or increase in pore pressure development. This strong soil-liquefaction-foundation-structure interaction (SLFSI) is a challenge for both geotechnical and structural engineers. This paper develops an efficient numerical procedure for the vulnerability assessment of buildings with shallow foundations to the combined impacts of seismic shaking and liquefaction. The approach quantifies settl...
A study on the liquefaction risk in seismic design of foundations
Geomechanics and Engineering, 2016
A fully coupled non-linear effective stress response finite difference (FD) model is built to survey the counter-intuitive recent findings on the reliance of pore water pressure ratio on foundation contact pressure. Two alternative design scenarios for a benchmark problem are explored and contrasted in the light of construction emission rates using the EFFC-DFI methodology. A strain-hardening effective stress plasticity model is adopted to simulate the dynamic loading. A combination of input motions, contact pressure, initial vertical total pressure and distance to foundation centreline are employed, as model variables, to further investigate the control of permanent and variable actions on the residual pore pressure ratio. The model is verified against the Ghosh and Madabhushi high acceleration field test database. The outputs of this work is aimed to improve the current computer-aided seismic foundation design that relies on ground's packing state and consistency. The results confirm that on seismic excitation of shallow foundations, the likelihood of effective stress loss is greater in deeper depths and across free field. For the benchmark problem, adopting a shallow foundation system instead of piled foundation benefitted in a 75% less emission rate, a marked proportion of which is owed to reduced materials and haulage carbon cost.
Seismic liquefaction of heterogeneous soil: mechanism and effects on structural response
2008
In the current practice of liquefaction prediction analysis, horizontally layered soil (with uniform properties within distinct soil layers) is usually assumed to estimate the liquefaction susceptibility of a soil deposit. However most of the soil properties of a natural deposit not only vary in the vertical direction but they could also vary in the horizontal direction, even within the so-called 'uniform' soil layers. This soil variability can be broadly classified into two main groups. They are the lithological heterogeneity (variability due to geological layers) and the small scale spatial variability. The first source of variability (variability due to layers) is considered properly in the current practice. But the second source of soil variability (small scale spatial variability), which is the subject of this research, is not properly addressed in general. -- From recent numerical research it was observed in the case of seismically induced excess pore water pressure (E...
Assessment and mitigation of liquefaction seismic risk : numerical modeling of their effects on SSI
2016
Strong ground motions can trigger soil liquefaction that will alter the propagating signal and induce ground failure. Important damage in structures and lifelines has been evidenced after recent earthquakes such as Christchurch, New Zealand and Tohoku, Japanin 2011. Accurate prediction of the structures’ seismic risk requires a careful modeling of the nonlinear behavior of soil-structure interaction (SSI) systems. In general, seismic risk analysisis described as the convolution between the natural hazard and the vulnerability of the system. This thesis arises as a contribution to the numerical modeling of liquefaction evaluation and mitigation.For this purpose, the finite element method (FEM) in time domain is used as numerical tool. The main numerical model consists of are inforced concrete building with a shallow rigid foundation standing on saturated cohesionless soil. As the initial step on the seismic risk analysis, the first part of the thesis is consecrated to the characteriz...
Liquefaction and Residential Foundations: Lessons Learned from Past Earthquakes
IFCEE 2015, 2015
For more than 50 years, engineers have recognized that seismicallyinduced soil liquefaction can cause significant damage to structural foundations, particularly shallow foundations. As a result, many modern building codes such as the International Building Code require geotechnical engineers to analyze and address liquefaction and its potential effects when designing new structures in seismic-prone areas. However, potential liquefaction hazard is often ignored for new residential structures in many parts of the United States, which are often designed in accordance with the International Residential Code. This article presents some of the inconsistencies and dangers associated with neglecting liquefaction hazard mitigation for residential structures. Lessons learned from past liquefaction case histories involving residential structures are reviewed. Commonly observed reasons that engineers and building inspectors often give for neglecting liquefaction mitigation for residential structures are discussed, with concerns over cost identified as the most common reason for this neglect. A comparative study is presented in which two forms of liquefaction mitigation are considered for a hypothetical new residential development. The results of the study show that the cost to structurally strengthen the foundation of each house was only 21% of the cost to improve the soil for each house through the installation of stone columns.
International Journal of Engineering & Technology
Liquefaction is generally defined as the loss of contact between soil particles during shaking (earthquakes), and it usually occurs in saturated loose sandy soils where the timescale is insufficient for the water to drain from the pores, thus increasing the excess pore pressure, and thereby floating the sand particles. For regular structures with shallow foundations, liquefaction normally leads to loss of soil strength, which leads to settlement of foundations. On the other hand, bridges are usually supported with piles foundation, which introduces additional effects during liquefaction. Therefore, this paper examines the possible effects of liquefaction on the structural performance of bridges during earthquakes. Furthermore, the failure of Showa Bridge during the 1964 Nagata earthquake was also discussed and analyzed as an example of the catastrophic effects of liquefaction. The analysis shows that the most influential effect during liquefaction is the increase in the unsupported ...
Elucidation of Seismic Soil Liquefaction Significant Factors
Earthquakes - From Tectonics to Buildings, 2021
The paper develops a framework to analyze the interactions among seismic soil liquefaction significant factors using the interpretive structural model (ISM) approach based on cone penetration test. To identify the contextual relationships among the significant factors, systematic literature review approach was used bearing in mind the selection principle. Since multiple factors influence seismic soil liquefaction, determining all factors in soil liquefaction would be extremely difficult, as even a few seismic soil liquefaction factors are not easy to deal with. This study highlighted two main characteristics of seismic soil liquefaction factors. First, the seismic soil liquefaction factors–peak ground acceleration F2 (amax), equivalent clean sand penetration resistance F5 (qc1Ncs), and thickness of soil layer F11 (Ts) influenced soil liquefaction directly and were located at level 2 (top level) in the ISM model, meaning they require additional seismic soil liquefaction factors excep...
Numerical Analyses of Interaction Between Adjacent Structures on Liquefied Soil
2016
In all major earthquakes, structures in the proximity of rivers and coastal plains, are often affected by substantial excess pore-water pressure which may lead to soil liquefaction. The excess pore-water pressure will lead to soil softening and change in structural response. However, in the few cases where soil-structure interaction is considered during the analysis process almost always a linear model of the soil and structure is employed. While this model is simple and therefore convenient, the analyses are a poor representation of real soil behaviour. Additionally, in major urban areas most structures are closely adjacent. Therefore, the situation is more complex than free-field condition or just a stand-alone structure. The analysis of a single structure cannot capture the major characteristics of the seismic response of closely adjacent structures. In this work an elasto-plastic multi-mechanism model was used to represent soil behaviour. A coupled solid-liquid phase formulation...
Soil liquefaction induced settlements with interaction of earthquake hazard analysis
on the Asian side with an uninterrupted, modern, high-capacity commuter rail system. Railway tracks in both sides of Istanbul Strait will be connected to each other through a railway tunnel connection under the Istanbul Strait. The line goes underground at Yedikule, continues through the Yenikapi and Sirkeci new underground stations, passes under the Istanbul Strait, connects to the Üsküdar new underground station and emerges at Sögütlüçesme. This project is one of the major transportation infrastructure projects in the world at present. The entire upgraded and new railway system will be approximately 76 km long. In this study, by using CPT data and acceleration and magnitude data (obtained seismic hazard analysis of Marmara Region), settlement analysis were carried out for Marmaray Project. As it is known, liquefaction is a soil behavior of saturated sandy soils under the earthquake/dynamic effects. In the first phase of the study, 'cyclic stress ratio approach' was applied to all data to analysis of soil liquefaction. In the second phase of the study, by using Isihara and Yoshimine (1992) approach, possible soil settlements for several design earthquakes (for several acceleration and magnitude values) were estimated.