Seed and idriss 1971 introduced the stress reduction factor d r as a parameter describing the ratio of cyclic stresses for a flexible soil column to the cyclic. In practice, demands are usually computed using approximate relations between surface peak acceleration and atdepth cyclic shear stress seed and idriss, 1971. For example, it is common practice to adopt in computer programs the proposed upper and lower bounds of the gg olog. Validation and application of empirical liquefaction models.
The stressbased approach for evaluating the potential for liquefaction triggering, initiated by seed and idriss 1967, has been used widely for the last 45 years e. Evaluation of liquefaction hazards in washington state. Liquefactioninduced ground deformations evaluation based on. Origin of cptbased methods all methods have similar origins. Liquefaction characteristics of infilled soil at banasree in dhaka city. The workshop basically developed the basic simplified procedure seed and idriss, 1971 1 focused on analyzing soil resistance to liquefaction hazards. Semiempirical procedures for evaluating liquefaction potential during earthquakes i. Correlation between liquefaction resistance and shear wave. However, due to the variability of the soil properties, in particular its flexibility elkahi et al. Cptbased probabilistic and deterministic assessment of in. Whether there is a natural link between these two different.
Since then, the procedure has evolved, primarily through summary papers by professor h. The procedure has been corrected and augmented periodically since that time with landmark papers by s eed 1979, seed and idriss 1982, and seed et al. Sensitivity of liquefaction triggering analysis to. The simplified procedure was first proposed by seed and idriss 1971. Finally, the study aims to evaluate the liquefaction potential in terms of. As given by the simplified procedure, two major factors are required to be determined, first, the seismic demand on a soil. Two recognition systems have been set up to estimate the. Such effort started with the simplified procedure by seed and idriss 1971. San fernando dam during the 1971 san fernando earthquake in california, just to name a few. Seed and idriss in 1971 predicts what will happen to a soil element, the il predicts the performance of the whole soil column and the consequence of liquefaction at the ground surface. Watts bar nuclear plant wbn, unit 2 final safety analysis report fsar, amendment 109, figure 2. Pdf assessment of liquefaction potential of guwahati.
Since 1971, this procedure has undergone several revisions and updates seed 1979, seed and idriss 1982, seed et al. Catastrophic failures in recent earthquakes have provided a sobering reminder that liquefaction of sandy soils as a result of earthquake ground shaking poses a major threat to the safety of civil engineering structures. Seed and idriss 1971 introduced use of a liquefaction triggering curve to relate the cyclic strength of a soil to the normalized standard penetration test spt blow count, which was used as a proxy for the dr and other factors affecting the cyclic strength of the soil. An expert committee from national research council nrc of united states under the. The second goal is to compute the csr by the simplified procedure seed and idriss, 1971. Guidelines for evaluating liquefaction resistance using shear.
After seed and idriss, 1971 snu geotechnical and geoenvironmental engineering lab. Depth reduction factor assessment for evaluation of cyclic. Pdf liquefaction characteristics of infilled soil at. Seed and idriss 1971 formulated the following equation for calculation of csr. Flow liquefaction instability as a mechanism for lower end of liquefaction charts. Seed and idriss 1971 proposed a simplified procedure for evaluation of liquefaction triggering that compare the soils resistance to liquefaction with the cyclic stress caused by an earthquake, expressed as the factor of safety against triggering liquefaction, fs liq. Following disastrous earthquakes in alaska and in niigata, japan in 1964, seed and idriss 1971 developed and published the basic simpli. The concept of the effective number of waves is then discussed and is. A new liquefaction prediction and assessment method that takes account of the influence of waveforms and durations of seismic motions is presented herein. Available field data concerning the liquefaction or nonliquefaction behavior of sands. Seed and idriss, 1971 and whitman, 1971, which, when applied regionally, can be used to estimate the combination of peak ground acceleration pga and earthquake magnitude m required to induce liquefaction at a site. Pdf flow liquefaction instability as a mechanism for.
The other principal technique, which we refer to as the magnitudebound method, uses the range of liquefaction effects i. For this purpose, the results of a comprehensive set of laboratory tests will be described first. Pdf flow liquefaction instability as a mechanism for lower. Presented also are the most widely accepted methods for evaluating the liquefaction potential of cohesionless oils in level ground, for estimating earthquakeinduced settlements and for analyzing slope stability against flow slides. The simplified method proposed by seed and idriss 1971 is the most used to evaluate the liquefaction potential in a soil deposit. Significant factors affecting the liquefaction or cyclic mobility potential of sands during earthquakes are identified, and a simplified procedure for evaluating liquefaction potential which will take these factors into account is presented. Seed and idriss 1971 introduced use of a liquefaction triggering curve to relate the cyclic strength of a soil to the normalized standard penetration test spt blow count, which was used as a proxy for the d r and other factors affecting the cyclic strength of the soil. Relationship between id and depth from seed and idriss, 1971. In many geophysical investigations, generally 35 downhole logging surveys are carried out in the. Several applications of the il have been reported by engineers in japan, taiwan, and the united states, although the index has not been evaluated extensively. Asce introduction in many cases the ground motions developed near the surface of a soil deposit during an earthquake may be attributed primarily to the upward prop agation of shear waves from an underlying rock formation. Watts bar nuclear plant, unit 2 amendment 102 to final safety analysis report fsar, miscellaneous ercw piping and ie conduit soil borings, figure 2. A comparative study between simplified and nonlinear dynamic. A simple method for evaluating liquefaction potential from.
Their fundamental mechanisms are still open to question. Pdf assessment of liquefaction potential of guwahati city. Evaluation of liquefaction potential of sabkha soil in. On level ground, lifelines may fail and buildings sink or topple due to differential settlements and massive land slides can be induced on sloping ground. Normalized shear modulus reduction and damping ratio curves. By obtaining factor of safety fs by different approaches we access liquefaction potential of soil at a certain depth in soil layer. Simplified liquefaction prediction and assessment method. Guidelines for evaluating liquefaction resistance using.
Idriss 1971 developed and published the basic simplified procedure. Evaluation of liquefaction potential of sabkha soil in aziziyah area, khobar, ksa. First, the shear wave velocity measurements are made at small strains, whereas porewater pressure buildup and liquefaction are mediumtohighstrain phenomena roy et al. Owing to devastation from japan earthquake seed and idriss 4 proposed frameworks for sptnbased assessments of liquefaction potential in simplified way. Smallstrain shear wave velocity measurements provide a promising supplement and in some cases, where only geophysical measurements are possible, may be the only alternative to the penetrationbased approach. It is a globally recognized standard which has been modified and improved through seed 1979 2, seed and idriss 1982 3, seed et al. Analyses of case histories for sites that had liquefied and those that did not, but could. Approaches for estimating liquefaction potential of soils. May 17, 2010 the simplified procedure using shear wave velocity measurements is increasingly used to evaluate the seismic liquefaction potential of soils. A total of 35 boreholes depth 2535 m have been drilled. Idriss in the late 1960s using blow count from the standard penetration test. Liquefactioninduced ground deformations evaluation based. Using the simplified procedure presented by seed and idriss 1971, the liquefaction is estimated based on the factor of safety against the triggering of liquefaction. Pdf cyclic liquefaction and its evaluation based on spt and cpt.
This report describes the results of a detailed investigation of improved procedures for evaluation of liquefaction hazards in washington state, and describes the development and use of a computer program, wsliq, that allows rapid and convenient performance of improved analyses. The following section discusses the simplified procedure as proposed by the 1996 nceer and 1998 nceernsf workshops youd, et al. Historically, seed and coworkers started the correlation with spt n values. Chapter 7 commentary foundation design requirements. Seed and idriss 1971 first published the widely used simplified procedure utilizing the standard penetration test spt. Liquefaction hazard mappingstatistical and spatial. Alaska and niigata, japan in 1964, seed and idriss 1971 developed and published the basic simplified procedure. Rather than 10 subsurface borings over a square kilometer, 1,000. Except for initial liquefaction, both a flow deformation require. This procedure is based on finding the boundary separating the liquefaction and nonliquefaction cases through the analysis of liquefaction case histories, following the general format of the seed idriss simplified procedure based on standard penetration.
When regional liquefaction hazard mapping is attempted in a city, numerous locations of subsurface data are often available. Guide for shearwavebased liquefaction potential evaluation. Journal of the soil mechanics and foundations division, 97, 12491273. Pdf liquefaction resistance evaluation of soils using standard. Following disastrous earthquakes in alaska and in niigata, japan in 1964, seed and.
International journal of innovative research in science. There had been an unfortunate inconsistency involved in the treatment of k 1 effects in all prior correlations, as a result of the history of their development, and this would. In the deterministic approach, the value of a hazard parameter of interest is estimated for a specified earthquake magnitude assumed to occur at a fixed sourcestosite distance e. Seismic soil liquefaction for deterministic and probabilistic. Seed and idriss 1971 formulated the following equation for calculating the cyclic. Idriss 1967, has been used widely for the last 45 years e. The seed idriss 1971 simplified procedure is used to estimate the cyclic shear stress ratios csr induced by earthquake ground motions, at a depth z below the ground surface, using the following expression. The procedure has evolved over time and still been used worldwide to analyze liquefaction resistance of soil. Presented also are the most widely accepted methods for evaluating the liquefaction potential of cohesionless oils in level ground, for estimating earthquakeinduced settlements and.
The paper describes a performancebased approach to the evaluation of liquefaction potential, and shows how it can be used. This research presents the results of studies in babol city to develop the depth reduction factor based on equivalent linear analysis of the study area for evaluation of cyclic stress ratio. Since 1971, this procedure has been revised and developed for other in situ tests, such as the cpt and v s seed et al. Simplified procedure for evaluating soil liquefaction potential. Liquefaction phenomenon could also be evaluated by other empirical correlations based essentially on comparison of grain size distribution of the site to the grain size envelope of sites that have liquefied in the past. The simplified procedure using shear wave velocity measurements is increasingly used to evaluate the seismic liquefaction potential of soils. Seed and idriss 1971 1 published a methodology based on empirical work termed as simplified procedure. Simplified procedure for evaluating soil liquefaction. Rather than 10 subsurface borings over a square kilometer, 1,000 subsurface borings are available.