Soil Shear Wave Velocity Research Articles

Effect of particle size distribution on the correlation between liquefaction resistance and shear wave velocity of granular soils

Shear wave method has been increasingly popular in assessing the liquefaction potential of granular soils. Two particle-scale parameters, the inter-particle friction and the shear modulus of grains, play vital roles in correlation between Cyclic Resistance Ratio (CRR ) and shear wave velocity corrected by overburden stress (Vs1 ). Series of drained one-dimensional compression tests were simulated on samples of different inter-particle friction angles assigned during preparation stage. Uniformity coefficients of these Particle Size Distribution (PSD) curves are 2 and 4 whose average particle size d 50 are identical. The shearing results, as well as their assigned inter-particle friction angles form calibration curves for real sands. Dissimilar PSD curves result in different calibration outcomes. For Silica sand no.8, these curves give divergent inter-particle friction angles. This study calibrates particle shear modulus for Silica sand no.8 as well. Different PSD curves give divergent values of particle shear modulus. PSDs show impacts on calibrations of both vital parameters, which have converse effects on CRR-Vs1 curves. This study suggests that the CRR-Vs1 correlation should be independent of PSDs.

Evaluation of liquefaction potential of soil using the shear wave velocity in Tehran, Iran

Shear-wave velocity (VS) offers a means to determine the seismic resistance of soil to liquefaction by a fundamental soil property. Iwasaki’s (1982) method is used to measure the liquefaction potential index for both of them. It follows the general format of the Seed-Idriss (1685) simplified procedure based on standard penetration test blow count and shear wave velocity (VS) on the basis of Andrus et al. (2004) using case history data from 43 boreholes in soils ranging from fine sand, silty sand, gravely sand to profiles including silty clay layers and the average soil shear wave velocity (VS30) in the south Tehran. Liquefaction resistance curves were established by applying a modified relationship between the shear-wave velocity and cyclic stress ratio for the constant average cyclic shear strain. The study area is the south-east of Tehran and the route of Tehran Metro Line 7. It is observed that there is not a perfect agreement between the results of the two methods based on five empirical relationships assuming cemented and non-cemented condition for soils. Moreover, the liquefaction potential index (PL) value in the Standard Penetration Test (SPT) method is more than that of the VS method. Liquefaction potential index (PL) values based on shear wave velocity (VS) using five empirical relationships in two un-cemented and cemented soil show that the used relations are overestimated and most of them have shown non-liquefaction condition for soils in the studied area.

Identification method for travel time based on the time domain technique in bender element tests on sandy and clayey soils

Based on the bender element (BE) international parallel tests, conducted from 2003 to 2005 using Toyoura sand, a standard test method for BE tests was proposed by Yamashita et al. (2009). The proposed method showed that any of the different identification methods would give a comparable travel time if the frequency of the transmitted wave were approximately equal to the frequency of the received wave. The proposed test method, however, did not show any specific procedure for choosing the input frequencies or for calculating the travel time. In the present study, therefore, with reference to the results from several previous studies on BE testing, a conditional expression for determining the input frequency and a calculation formula for the travel time have been defined, and BE testing using 13 different sandy and clayey soils has been conducted. After the testing, it was confirmed that the testing method is able to determine the shear wave velocity of sandy and clayey soils having widely different stiffnesses. Furthermore, the study has found that a reevaluation of the International Parallel Test results using this method has resulted in less variation as compared to the results from the reevaluation by Yamashita et al. (2009). This method is recommended in the "Method for laboratory measurement of shear wave velocity of soils by bender element test" standardized by the Japanese Geotechnical Society (JGS) in 2011 (Japanese Geotechnical Society, 2011).

Site Classification and Design Response Spectra for Seismic Code Provisions - (II) Proposal

In the companion paper (I - Database and Site Response Analyses), site-specific response analyses were performed at more than 300 domestic sites. In this study, a new site classification system and design response spectra are proposed using results of the site-specific response analyses. Depth to bedrock (H) and average shear wave velocity of soil above the bedrock () were adopted as parameters to classify the sites into sub-categories because these two factors mostly affect site amplification, especially for shallow bedrock region. The 20 m of depth to bedrock was selected as the initial parameter for site classification based on the trend of site coefficients obtained from the site-specific response analyses. The sites having less than 20 m of depth to bedrock (H1 sites) are sub-divided into two site classes using 260 m/s of while the sites having greater than 20 m of depth to bedrock (H2 sites) are sub-divided into two site classes at equal to 180 m/s. The integration interval of 0.4 ~ 1.5 sec period range was adopted to calculate the long-period site coefficients () for reflecting the amplification characteristics of Korean geological condition. In addition, the frequency distribution of depth to bedrock reported for Korean sites was also considered in calculating the site coefficients for H2 sites to incorporate sites having greater than 30 m of depth to bedrock. The relationships between the site coefficients and rock shaking intensity were proposed and then subsequently compared with the site coefficients of similar site classes suggested in other codes.

Dependencies of Shear Wave Velocity and Shear Modulus of Soil on Saturation

AbstractShear wave propagation in soil is a physical phenomenon and has been used widely for monitoring and seismic property assessment in geotechnical engineering. Shear wave velocity Vs and small-strain shear modulus G0 are the key parameters in defining material response to various dynamic loadings. To date, the dependencies of Vs and G0 on saturation, especially in high suction range, are still not well understood because of the limited testing methodology and experimental evidence. In this study, the authors present a new laboratory instrumentation of measuring shear wave propagation in different types of unsaturated soils. Low relative humidity and water mist injection environment are used for measuring shear wave velocity under both drying and wetting conditions. Bender element technique was used to measure the shear wave responses. Step function was used as excitation, and determination of a first arrival time was identified and consistently used for all shear wave measurements. Shear wave evoluti...

Prediction of peak ground acceleration using ϵ-SVR, ν-SVR and Ls-SVR algorithm

ABSTRACTIn this paper, a prediction model is developed using support vector machine for forecasting the parameter associated with ground motion of a seismic signal. The prediction model is developed using three learning algorithms, ϵ-support vector regression, ν-support vector regression and least square-support vector regression (Ls-SVR) for forecasting peak ground acceleration (PGA), a parameter associated with ground motion of a seismic signal. The prediction model is developed for each of the algorithms with different kernel functions, namely linear kernel, polynomial kernel and radial basis function kernel. The ground motion parameter is related to four seismic parameters, namely faulting mechanism, average soil shear wave velocity, earthquake magnitude and source to site distance. The database used for modelling is NGA flatfile released by Pacific Earthquake Engineering Research Center. The experimental results show that the optimal prediction model for forecasting PGA is Ls-SVR with RBF kernel. It is observed that the developed prediction model is better compared to the existing conventional models and benchmark models in the same database. This paper further compares the three variations of SVR algorithm for ground motion parameter prediction model. The learning effectiveness of each algorithm is measured in terms of accuracy, testing error and overfitness measure.

Small-strain shear modulus of volcanic granular soil: An experimental investigation

While volcanic soils exist in many places around the world, their mechanical behavior is however less extensively studied as compared to the conventional soil type such as quartz sand and clay. This paper presents an experimental study investigating the small-strain shear modulus (G0) and associated shear wave velocity (Vs) of a volcanic granular soil collected from the northeast of Japan that was affected by the devastating 2011 Tohoku earthquake. Reconstituted soil specimens were tested at different packing densities and confining stress levels by using the resonant column technique, and the pressure and density dependence of shear modulus was established for the soil. The study showed that under otherwise similar conditions, the G0 value of the volcanic soil was markedly lower than that of clean quartz sands, but it tended to increase significantly when the fine particles in the soil were removed. This finding suggests that the presence of fines plays an important role in the mechanical behavior of volcanic soils. A practical model accounting for the influence of fines and the pressure and density dependence is proposed and it is shown to provide reasonable estimates of G0 for both volcanic soils and clean quartz sands studied.

Seismic ground motion amplification pattern induced by a subway tunnel: Shaking table testing and numerical simulation

A series of 1g shaking table tests, followed by the numerical simulations, is performed to investigate the effect of a circular subway tunnel on the ground motion amplification pattern. Effects of various parameters, including shear wave velocity of soil, frequency content of input motion, flexibility ratio and tunnel depth on the amplification pattern is investigated. Experimental study revealed that the tunnel did not affect free field response at dimensionless period greater than 10. Subsequent parametric study demonstrated that the amount of amplifications were mainly controlled by dimensionless period, dimensionless depth and flexibility ratio. Tunnel effect on the amplification pattern is more prominent for dimensionless period between 3 to 10, flexibility ratio greater than 1 and dimensionless depth less than 3. The study revealed that subway tunnel influences the seismic response of low period buildings, constructed above the tunnel.

Prediction of ground motion parameters using randomized ANFIS (RANFIS)

In this paper, a novel neuro-fuzzy learning machine called randomized adaptive neuro-fuzzy inference system (RANFIS) is proposed for predicting the parameters of ground motion associated with seismic signals. This advanced learning machine integrates the explicit knowledge of the fuzzy systems with the learning capabilities of neural networks, as in the case of conventional adaptive neuro-fuzzy inference system (ANFIS). In RANFIS, to accelerate the learning speed without compromising the generalization capability, the fuzzy layer parameters are not tuned. The three time domain ground motion parameters which are predicted by the model are peak ground acceleration (PGA), peak ground velocity (PGV) and peak ground displacement (PGD). The model is developed using the database released by PEER (Pacific Earthquake Engineering Research Center). Each ground motion parameter is related to mainly to four seismic parameters, namely earthquake magnitude, faulting mechanism, source to site distance and average soil shear wave velocity. The experimental results validate the improved performance of the machine, with lesser computation time compared to prior studies.

Dynamic earth pressure on rigid retaining walls induced by a neighboring machine foundation, by the meshless local Petrov-Galerkin method

Dynamic earth pressure induced by machine foundations on a neighboring retaining wall is analyzed with emphasis on factors which control the intensity and location of the design forces. The meshless local Petrov-Galerkin (MLPG) method is used to analyze the problem for a variety of retaining wall and machine foundation geometries. The soil medium is assumed to be homogeneous and visco-elastic. The machine foundation is idealized as a harmonic sinusoidal dynamic force often encountered in practice. A number of analyses have been made to reveal the effect of the loading frequency, the location and size of the foundation and the soil shear wave velocity on the distribution and magnitude of the dynamic earth pressure. Results indicate that there is a critical frequency and a critical location for which the passive pressure takes the maxima in the entire duration of the dynamic load.

Predictive equations for soil shear-wave velocities of Hungarian soils based on MASW and CPT measurements around Győr

Determination of shear-wave (S-wave) velocity profiles is the first step in seismic hazard assessment of a town, because the dynamic parameters of local soil types are vital for seismic response analysis of a specific area in order to determine the local soil effect in a case of a seismic event for seismic risk analysis. S-wave velocity profiles have been determined for many areas within Győr. Extensive use of historical boring logs allowed for correlations and reasonable extrapolation of soil performance throughout the area. This has led to a pattern of soil layer distributions and delineates several different soil zones for Győr.

Damage analysis of cut-and-cover tunnel structures under seismic loading

Damage analyses of rectangular cut-and-cover tunnels are performed to define the damage states and corresponding damage indices (DIs) under seismic loading. Single, double, and triple box structures designed for metro subway systems in South Korea are used. The tunnel structures are modeled by nonlinear frame elements attached to a series of normal and shear springs to simulate the soil–tunnel interaction. Pushover analyses are performed to develop the capacity curves and to monitor the development of plastic hinges. Parallel elastic analyses are also performed to determine the elastic moments at which plastic hinges form. For each tunnel and site condition, three damage states, which are minor, moderate, and extensive, are defined in terms of number of plastic hinges that form at the corners of the tunnel structure. Each damage state is linked to the corresponding DI, which is defined as the ratio of the elastic moment to the yield moment and free-field shear strain. DI for the single box tunnel is shown to be mostly independent of the shear wave velocity of soil. The values of DIs for single, double, and triple box tunnels range from 1.0 to 2.0. It is highlighted that the proposed damage state associated with DI and shear strain provide an enhanced estimate of the seismically induced damage of box tunnels and can be easily utilized in a performance-based design.

Numerical Estimation of the Fundamental Frequency of Improved Sites with Stone Columns

Background/Objectives: Installation of stone columns is one of the appropriate techniques for the improvement of soft soils. However, the seismic behavior of this reinforcing elements has been limitedly studied. Methods/Statistical Analysis: In this paper, effects of stone column construction on the fundamental frequency of the sites are studied numerically. Finite element analysis was performed using ABAQUS. The performed analysis was a modal analysis through the calculation of eigenvalues to determine of the fundamental frequency of improved sites with stone columns. The analyses was carried out in 3D and 2D in some cases. Findings: The results demonstrated that constructing the stone columns can increase the fundamental frequency of the site up to three times. Based on the performed analyses, the fundamental frequency amplification factor of the site (α) can be defined according to the dimensionless parameters including stone column to soil shear wave velocity, stone column height to its diameter, stone column distance to its diameter, and stone column arrangements. The results indicated that α decreased with a rise in the ratio of the stone column height to its diameter. A comparison of the stone column arrangements demonstrated that, in a triangle arrangement, the value of α was greater than the corresponding value in square arrangement. The results indicate that, in floating stone columns the effects of stone columns on the soil mass due to the absence of the bottom of the column with respect to the condition where the stone column was end bearing was considerably insignificant. Application/Improvements: Based on the results, α was presented for the square and triangle arrangements according to the dimensionless parameters and finally a 2D equivalent method was presented for the simplification of the 3D actual problem.

Correlation between liquefaction resistance and shear wave velocity of granular soils: a micromechanical perspective

The shear wave velocity method has become an increasingly popular means to evaluate the liquefaction potential of granular soils. Understanding the fundamental mechanism underlying existing empirical or semi-empirical relationships is important for better assessing their reliability. This paper presents a particle-scale study of the correlation between cyclic resistance ratio (CRR) and the shear wave velocity corrected for overburden stress (Vs1). The discrete-element method was used to simulate a series of undrained stress-controlled cyclic triaxial tests together with shear wave velocity (Vs) measurements. Discrete-element method modelling with various relative densities, confining pressures and micro-parameters was performed under various cyclic stress ratios (CSRs), and the onset of liquefaction was illustrated through both macroscopic and microscopic responses, for example, inferred excess pore-water pressure, mechanical coordination number and redundancy index. The inter-particle friction was identified as the key micro-parameter that governs the liquefaction resistance of granular soils. A micro-scale CRR–Vs1correlation considering two independent micro-parameters, inter-particle friction and particle shear modulus, was then obtained and further validated with the outcomes from three dynamic centrifuge model tests performed on silica sand no. 8. This study demonstrates that the CRR–Vs1correlation is particle specific, thus soil specific, and the particle mechanical properties should be included in the Vs-based method for future liquefaction evaluation of granular soils.

Development of an empirical correlation for predicting shear wave velocity of Christchurch soils from cone penetration test data

Following the companion study of McGann et al. [1], seismic piezocone (SCPTu) data compiled from sites in Christchurch, New Zealand area are used with multiple linear regression to develop a Christchurch-specific empirical correlation for use in predicting soil shear wave velocities, Vs, from cone penetration test (CPT) data. An appropriate regression functional form is selected through an evaluation of the residuals for regression models developed with the Christchurch SCPTu database using functional forms adopted by previous empirical correlations between Vs and CPT data. An examination of how the residuals for the chosen regression form vary with the predictor variables identifies the need for non-constant depth variance in the regression model. The performance of the model is assessed through comparisons of predicted and observed Vs profiles and through forward predictions with synthetic CPT data. The new CPT–Vs correlation provides a method to estimate Vs from CPT data that is specific to the non-gravel soils of the Christchurch region in their current state (caution should be used for western portions of the Springston Formation where SCPTu data were sparse). The correlation also enables the utilization of the large, high-density database of CPT logs (>15,000 as of 1/1/2014) in the Christchurch region for the development of both site-specific and region-wide models of surficial Vs for use in site characterization and site response analysis.

Determination of Shear Wave Velocity Using Multi-channel Analysis of Surface Wave Method and Shear Modulus Estimation of Peat Soil at Western Johore

Shear wave velocity and shear modulus is common for geotechnical and geophysics engineer to the determine interaction of soil dynamic properties. Both of the dynamic properties were often related to dynamic loading such as earthquake, moving traffic, machineries and bomb blasting. The study was conducted at western part of Johore such as Parit Sulong and Pontian where deposition of peat soil were exists and recognised as problematic soils to the engineers. This study was carried out to determine the shear wave velocity of peat soil using Multi-channel Analysis of Surface Wave (MASW) method and estimation shear modulus of peat using empirical formula. To use the empirical formula, the density of peat soil was also needed thus using the peat sampler for every 0.5 meter depth to obtain the density. From the MASW test for both test sites, the shear velocity of peat at Parit Sulong is between 40 m/s and 55 m/s until depth of 1.5 m meanwhile at Pontian, the shear wave velocity between 21 m/s and 67 m/s until 2.5 m depth. Using shear velocity, shear modulus of peat were estimated for Parit Sulong are ranged between 1575kPa – 3514kPa and Pontian are ranged between 385kPa – 5117kPa. The shear velocity and shear modulus of peat are very low due to the unique characteristics of peat soils compared with other typical soil.

Correlation between standard penetration (N SPT) and shear wave velocity (V S) for young coastal sands of the Caspian Sea

Nowadays, the dynamic properties of soil and study of its dynamic response in connection with the designing of the structures resistant against earthquake seems more critical day by day along with the increase of the structures’ height and specialization of the civil operations. Since geophysical tests are often costly and time consuming, applying other tests results for estimation of Shear wave velocity is extremely useful. For this purpose, this paper focuses on determining and offering a relationship between the results of standard penetration test (SPT), which is highly quick, cost-effective, and common test, with shear wave velocity of soil. For this end, several boreholes with different depths were drilled in several coastal cities of the Caspian Sea, and SPT was carried out in them. Then downhole test for calculating shear wave velocity profile was performed in all the studied sites using the same borehole and, in some cases, by drilling a new borehole. After that, the data were analyzed for determining the correlation via a suitable statistical method. The results indicated that the obtained relationship is suitably compatible with the universal practical relationships presented for sandy soils and stands approximately in the upper limit of the relationships. It is noteworthy that although applying these relationships for the estimation of shear wave velocity in the coastal sands of the Caspian Sea for small projects and the initial phases of the average and big projects is recommended, it must be considered that direct geophysical methods must be employed in cases where this parameter seems more critical.

Seismic Mechanics and Engineering Application Analysis of Shear Wave Velocity Inferring

The soil shear wave velocity is the key parameter in site seismic response analysis. And it is also one of the important parameters in evaluation of seismic safety for engineering sites or the seismic microzonation. Normally, the parameter is obtained through the field testing. Sometimes shear wave velocity testing could not arrive at technical requirement or the technical requirements due to the actual condition. Then it is necessary to develop the parameter inferring method. In this paper, the data of shear wave velocity of soils at 46 typical boreholes in Dongying are selected for regressive statistic analysis. Based on the data, the formulas of shear wave velocity with linear function and power function are obtained. Considering the influence of the soil classification to the soil shear wave velocity, the new inferring formulas are obtained. Then the inferring formulas of the shear wave velocity are applied at 4 boreholes in one residential building. It is shown that the calculation results conform well with the site testing results, and the formulas are applicable for engineering with sufficient accuracy.

Measurement of soil shear wave velocity using in situ and laboratory seismic methods – some methodological aspects

This article presents the results of seismic shear wave velocity (V S ) measurements using the CSWS/SAWS ( Continuous Surface Wave System/Spectral Analysis of Surface Waves ) and SDMT ( seismic flat dilatometer ) methods, as well as BET ( Bender Elements Test ), on an experimental test site (and samples taken from it). The test site, a geologically relatively uniform alluvial sand formation area, was carefully chosen and checked for uniformity by means of drillings and soundings. The research aimed to determine how results from indirect, non-invasive surface geophysical tests (SASW and CSWS) correspond with those from SDMT penetration tests as well as the BET laboratory seismic method, and how some methodological aspects can influence them. Different wave sources and frequency were examined as the main factors for interpretation. The influence of other examined factors is also discussed.

Estimation Study on Shear Wave Velocity of Seabed Using GRNN

Characterization of the shear wave velocity of soils is an integral component of various seismic analysis, including site classification, hazard analysis, site response analysis, and soil-structure interaction. Shear wave velocity at offshore sites of the coastal regions can be measured by the suspension logging method according to the economic applicability. The study presents some methods for estimating the shear wave velocity profiles in the absence of site-specific shear wave velocity data. By applying generalized regression neural network (GRNN) for the estimation of in-situ shear wave velocity, it shows good performances. Therefore, this estimation method is worthy of being recommended in the later engineering practice.