Field Correlation of Soil Liquefaction with SPT and Grain Size

Two earthquakes of magnitudes 6.7 and 7.4 that occurred in 1978 off the Pacific coast of Miyagi Prefecture, Japan, provided field liquefaction data for a fairly wide range of peak ground surface acceleration from 100 to 290 gal. The range of SPT N-values was also fairly wide because special efforts were made to collect non-liquefaction data in addition to liquefaction data. Dynamic shear stress ratios adjusted for earthquake magnitudes and effective overburden pressures are plotted against N-values adjusted for effective overburden pressures. The field data are compared with two methods proposed recently, one by Seed and the other by Iwasaki et al, after a critical review of the methods and the SPT\u27s in the U.S. and Japan. The method by Seed tended to underestimate the resistance to liquefaction for small N-values, particularly for silty sands; whereas the method by Iwasaki et al tended to underestimate the resistance to liquefaction for large N-values

Nonlinear Soil Properties Estimated from Strong Motion Accelerograms

A rational procedure is developed for estimating dynamic soil properties from strong motion accelerograms obtained only at the ground surface. The method consisting of spectrum analysis and multi-reflection analysis could permit evaluation of time histories of shear modulus versus shear strain in the soil during an earthquake. The method is applied to four sites where the soil profile is relatively simple and where several strong motion records are available. The analytical results show that (1) the first predominant period of surface soil increases with an increase in shear strain developed in the soil, (2) the strain-dependent shear moduli evaluated from strong motion records are in fairly good agreement with laboratory test results in a strain range from 10-5 to 10-3, and (3) the shear modulus ratio is better correlated with peak particle velocity at the ground surface than with peak acceleration

Correlation between CPT Data and Dynamic Properties of In Situ Frozen Samples

Correlations between cone penetration resistance and liquefaction resistance of sandy soils are examined, based on high quality undisturbed samples obtained by the in situ freezing method. For this purpose, the CPT tests are conducted at six sites where in situ frozen sands with fines contents up to 30 % were sampled and their dynamic properties were determined in the laboratory. The comparison of the CPT data with the soil properties of the in situ frozen samples has shown that: (1) Robertson\u27s soil classification chart performs well for sandy soils in Japan; (2) the CPT qt-value shows a good correlation with elastic shear modulus of the in situ frozen samples; and (3) the liquefaction resistance of the in situ frozen samples is uniquely expressed if the cone penetration resistance is normalized in terms of confining pressure and minimum void ratio

Liquefaction Potential Evaluation for the Messina Straits Crossing by Field and Laboratory Testing

The method adopted for the evaluation of the soil liquefaction potential in the Messina Straits, Italy, is presented and the results are discussed. The study was carried out for the design of three submerged floating tunnels linking Sicily to the Italian mainland. The method is based on a combined approach where field measurements are used to partly re-create the original soil fabric in the specimens for cyclic laboratory tests. The method is suitable for offshore investigations where recovery of truly undisturbed samples is hardly possible. The results show that in this way a much higher resistance to liquefaction is predicted than from conventional laboratory tests. The results of indirect methods based only on CPT records or shear wave velocity measurements in the field are presented first, and their limitations that led to the selection of an improved laboratory testing program are outlined

Prediction of pile response to lateral spreading by 3-D soil-water coupled dynamic analysis: shaking in the direction of ground flow

Numerical predictions of a series of shake table tests are presented in this paper in order to examine the accuracy of a 3-D effective stress analysis in predicting the behavior of piles subjected to liquefaction-induced ground flow. For a rigorous assessment of the analysis, “Class B” predictions are reported in which numerical and constitutive model parameters were set before the event, and the target motion was used as an input motion in the analysis. Modeling of the stress-strain behavior of sand, identification of the initial stress state and critical numerical parameters in the 3-D seismic analysis of the soil-pile system are discussed in detail. Combined effects of kinematic loads due to large lateral ground movement and inertial loads on pile behavior are examined through a series of tests using different shaking direction, excitation amplitude and mass of the footing (load from the superstructure). By and large, very good agreement was obtained between the predicted and measured peak responses of the pile foundation, whereas the analysis underestimated the displacements of the sheet-pile wall and was less accurate in predicting the residual deformation of the foundation piles. Reasons for these discrepancies and limitations of the analysis method are discussed

Standard Penetration Test-Based Probabilistic and Deterministic Assessment of Seismic Soil Liquefaction Potential

This paper presents new correlations for assessment of the likelihood of initiation (or “triggering”) of soil liquefaction. These new correlations eliminate several sources of bias intrinsic to previous, similar correlations, and provide greatly reduced overall uncertainty and variance. Key elements in the development of these new correlations are (1) accumulation of a significantly expanded database of field performance case histories; (2) use of improved knowledge and understanding of factors affecting interpretation of standard penetration test data; (3) incorporation of improved understanding of factors affecting site-specific earthquake ground motions (including directivity effects, site-specific response, etc.); (4) use of improved methods for assessment of in situ cyclic shear stress ratio; (5) screening of field data case histories on a quality/uncertainty basis; and (6) use of high-order probabilistic tools (Bayesian updating). The resulting relationships not only provide greatly reduced uncertainty, they also help to resolve a number of corollary issues that have long been difficult and controversial including: (1) magnitude-correlated duration weighting factors, (2) adjustments for fines content, and (3) corrections for overburden stress

Rank of Correlation Coefficient as a Comparable Measure for Biological Significance of Gene Coexpression

Information regarding gene coexpression is useful to predict gene function. Several databases have been constructed for gene coexpression in model organisms based on a large amount of publicly available gene expression data measured by GeneChip platforms. In these databases, Pearson's correlation coefficients (PCCs) of gene expression patterns are widely used as a measure of gene coexpression. Although the coexpression measure or GeneChip summarization method affects the performance of the gene coexpression database, previous studies for these calculation procedures were tested with only a small number of samples and a particular species. To evaluate the effectiveness of coexpression measures, assessments with large-scale microarray data are required. We first examined characteristics of PCC and found that the optimal PCC threshold to retrieve functionally related genes was affected by the method of gene expression database construction and the target gene function. In addition, we found that this problem could be overcome when we used correlation ranks instead of correlation values. This observation was evaluated by large-scale gene expression data for four species: Arabidopsis, human, mouse and rat

HVOF and laser cladded Fe-Cr-B coating in simulated biomass combustion: microstructure and fireside corrosion

Biomass is often considered as a low carbon alternative to fossil fuels in the power industry. However the heat exchangers in biomass plants can suffer from chloride based aggressive fireside corrosion. A commercially available amorphous Fe-Cr-B alloy was deposited onto a stainless steel substrate by HVOF thermal spray and laser cladding. The controlled environment corrosion tests were conducted in a HCl rich environment at 700°C for 250 h with and without KCl deposits. The samples were examined with XRD, SEM and EDX mapping to understand the corrosion mechanisms. In the absence of any deposits, the amorphous HVOF coating performed very well with a thin oxide growth whereas the crystalline laser cladding suffered from ~350 μm metal loss. The scales were composed of MnWO₄, Fe₂O₃, Fe₃O₄ and Cr₂O₃. When a KCl deposit was present, the HVOF sprayed coating delaminated from the substrate and MnCl₂ was found in the scale