Correlation Of Shear Wave Velocity Research Articles

Influence of spatial variability of soil shear-wave velocity considering intralayer correlation on seismic response of engineering site

Shear-wave velocity uncertainty significantly impacts seismic response analysis at engineering sites. Previous studies focused on the correlations of shear-wave velocities within soil layers. However, the influence of the vertical spatial variability of shear-wave velocity within individual soil layers was not considered. This study selected a typical Site Class II engineering site to investigate this influence based on the equivalent linear seismic response analysis method of layered soil deposits. Existing field test data on shear-wave velocity were used to discretize the shear-wave velocity within soil layers into a one-dimensional (1D) random field through covariance matrix decomposition and local average process theory. Monte Carlo simulations generated random shear-wave velocity profiles with different vertical correlation distances. Three artificial records with different earthquake return periods were used as input motions at the engineering bedrock for the 1D free-field model. Considering soil shear-wave velocity uncertainty, the peak shear strain increased by 19–27% with the input ground motion amplitude. Moreover, the site peak shear strain variability increased by 25–34% with the vertical correlation distance. The proposed 1D random field model effectively simulated the interlayer correlation and spatial variability of shear-wave velocity within soil layers, demonstrating its significance in seismic response analysis.

Development of empirical CPTu-Vs correlations for post-glacial sediments in Southern Quebec, Canada, in consideration of soil type and geological setting

The correlation of shear wave velocity (Vs) with piezocone penetration test (CPTu) parameters is investigated in post-glacial sediments along the St. Lawrence and Saguenay rivers, Southern Quebec, Canada. The compiled database includes 991 CPTu-Vs measurements at 40 sites. The objectives are to examine the applicability of existing CPTu-Vs correlations, identify the main CPTu parameters and develop specific CPTu-Vs correlations that account for the effects of soil type (sandy or clayey) and geological setting (Champlain or Laflamme sea sediments). Results reveal that the application of existing correlations is biased in varying degrees, denoting a need for site-specific correlations for the study area. Multivariate regression analyses confirm the importance of cone tip resistance and depth as Vs predictors assisted by normalised pore pressure and soil behaviour type index. Consideration of soil type and geological setting helps reduce uncertainties in CPTu-Vs correlations for fine-grained soils.

Critical insights in laboratory shear wave velocity correlations of clays

Shear wave velocity, Vs, is an important mechanical–dynamic parameter allowing the characterization of a soil in the elastic range (γ < 10–3%). Thirty-five existing Gmax or Vs laboratory correlations were examined in this study and are grouped into different general forms based on their geotechnical properties. A database of 11 eastern Canadian clay deposits was selected and used for the critical insights. The effect of the coefficient of earth pressure at rest, K0, was also examined. A range of variation for each general form of correlation was determined to take the plasticity index and void ratio values of investigated sites into account. The analysis shows a significant scatter in Vs1 values predicted by existing correlations and raises questions on the applicability of these correlations, especially for eastern Canadian clays. New correlations are proposed for Champlain clays based on laboratory measurement of Vs using the piezoelectric ring-actuator technique, P-RAT, incorporated in consolidation cells. An analysis of P-RAT results reveals the sample disturbance effect and suggests an approach to correct the effect of disturbance on laboratory Vs measurements. The applicability of the proposed correlations, including the disturbance correction, is validated by comparison with in situ measurements using multi-modal analysis of surface waves (MMASW).

Correlation of Shear Wave Velocity with Spt-n for A Tower- Building Site at Erbil City

Measurement of shear wave velocity (Vs) plays a crucial role in ground movements around geotechnical structures such as building foundations in the urban area and tunnels. Basically, measuring Vs often requires when seismic properties of soils are essential to be calculated, such as elastic shear modulus. Multichannel analysis of surface wave (MASW) is one of the seismic methods which employs surface waves to measure Vs. It is often not available along with site investigation due to high cost, complicated technical analysis, noise pollution, space constraints, etc. Hence, it is essential to predict Vs through correlating it to other soil parameters such as standard penetration test blows count (SPT-N). Therefore, the main focus in the current study was to correlate between Vs and SPT-N using an empirical equation likely applied for clay soils. A complementary subsoil investigation was performed of a tower-building at Erbil City, including SPT-N values for three boreholes and their corresponding MASW measurements. These data were, in turn, used to estimate Vs from corrected SPT-N. The currently proposed equation compared with the existing ones in the literature. The comparison shows that the proposed equation predicts the values of Vs as good as those available in the literature for both of the datasets in the current and the previous studies.

Seismic Amplification of Soil Ground with Spatially Varying Shear Wave Velocity Using 2D Spectral Element Method

ABSTRACT Spatial variability of soils can have a profound effect on seismic site amplification, which cannot be reasonably captured using conventional one-dimensional analyses. In this study, the shear-wave velocity of soils is modelled as a 2D spatially correlated random field. Extensive simulations are conducted to quantify the influence of spatial variability of soils on site amplification using 2D Spectral Element Method. Key influential factors include variation and spatial correlation of shear wave velocity in both horizontal and vertical directions. Numerical simulations show that site amplification at resonance frequencies is subdued, and its variation depends on these influential factors. Spatial correlations of site amplification are also investigated, showing that the correlation range of site amplification is frequency dependent. The correlation range is much longer at low frequencies than that at high frequencies. The analyses imply that length scales of both soil heterogeneity and wavelength should be considered simultaneously when quantifying the spatial variability of ground motion amplification.

Intra-event spatial correlation model for the vertical component of response spectral accelerations

Seismic risk assessment of lifeline networks or building portfolios requires the quantification of spatial correlation of ground motion intensity over a region during an earthquake event. In this paper, the spatial correlation of vertical spectral accelerations (SAs) at single and multiple periods is studied. In the first part, the spatial correlations of vertical SAs at eight periods in the range of 0.0–3.0 s are investigated. The geostatistical analysis is performed to compute the spatial correlations of SAs using records compiled from ten earthquake events occurred in California, Japan, Taiwan, and Mexico. The results show that the spatial correlations of the vertical SAs at short periods are dependent on the regional site conditions indicated with the spatial correlation of shear wave velocity in the top of 30 m (Vs30). However, the effect of the correlation of Vs30 on the correlation of the vertical SAs decreases as the spectral period increases. A simple predictive model is proposed to quantify the correlation ranges of the vertical SAs considering regional site conditions. The proposed model is compared with the models presented for horizontal SAs. The comparison shows that the correlation ranges of horizontal SAs are generally larger than those of the vertical ones. As an illustrative example, seismic performance of a hypothetical bridge network is studied with different ranges of spatial correlations. The results indicate that ignoring spatial correlation may significantly affect the exceedance probability for spatially distributed engineering demand parameters of bridges in the network. In the second part, the multivariate spatial correlation is investigated using linear model of coregionalization (LMC) approach. Based on the correlation estimates obtained from geostatistical analysis, a predictive model is proposed to simulate vertical SAs at multiple periods and different sites.

Empirical Correlation between Geotechnical and Geophysical Parameters in a Landslide Zone (Case Study: Nargeschal Landslide)

Today, geotechnical and geophysical techniques are used for landslide evaluation. Geotechnical methods provide accurate data, but are time consuming and costly. Geophysical techniques, however, are fast and inexpensive, yet their accuracy is lower than that of the geotechnical methods. Therefore, simultaneous use of geotechnical and geophysical methods provides a suitable solution for landslide evaluation. Availability of geotechnical and geophysical data makes it possible to investigate correlation between different parameters. Correlating geotechnical and geophysical parameters ends up lowering field investigation costs and enhancing subsurface survey speed in a landslide zone. In the present study, in order to evaluate Nargeschal landslide in Iran, ambient noise measurement, ERT survey, and geotechnical investigations were used. Once finished with data processing, the data obtained from geotechnical and geophysical investigations were correlated. These included SPT-N – electrical resistivity, soil moisture content – electrical resistivity, and SPT-N – shear wave velocity correlations. The correlations were examined using two methods, namely Spearman’s coefficient test and least square regression analysis. The results obtained from the two methods were in good agreement with one another. The correlations obtained in this study were of moderate to very strong strength and fell in the range of the results of previous studies. Investigation of the results indicated significant influences of ground water on electrical resistivity and soil stiffness on shear wave velocity. Results of this study can be used for soil classification and determination of mechanical and seismic characteristics of soil across various areas.

Determination of shear wave velocity of Yangtze Delta sediments using seismic piezocone tests

Abstract Shear wave velocity is one of the most important parameters in the evaluation of soil dynamic behavior and seismic design of geotechnical structures. In this study, a comprehensive geotechnical in situ and laboratory investigation into the predominantly intermediate soils deposited in the upper Quaternary basin of the Yangtze Delta (YD) was carried out. It is indicated that uncertainty may be introduced when applying existing empirical shear wave velocity correlations from the literatures due to the heterogeneous and highly stratified nature of such sediments, and the issue of change of drained, partially drained and undrained conditions during penetration. The applicability of six existing CPT-V s correlations for YD mixed soils, relied on direct CPT measured data or other indirect parameters incorporated, has been first compared and evaluated. The results show that all the selected correlations tend to be biased to varying degrees, demonstrating the need for a YD-specific V s prediction correlation. Hence, new prediction models are proposed through multiple linear regression based on the YD SCPTU database, which relies on CPT-based variables (q t , f s , B q , I c , z) and additional laboratory data. The performance of these models is evaluated through comparisons of predicted and measured V s values. Moreover, several significant influencing factors are analyzed including the initial effective stress, void ratio and pore pressure ratio. It is found that the coefficients of determination are generally larger when cone resistance, overburden stress, void ratio or pore pressure ratio are considered in the regression equations rather than cone resistance solely. Additionally, an appropriate CPT-V s model is suggested from a practical standpoint, which depends on terms directly measured by the CPT (q t or q c , f s and z). Although situated in the Chinese context, the proposed correlations can be helpful in preliminary estimate of the stiffness at small strain of similar deltaic deposits encountered in other countries.

Ultrasound shear wave elastography in the assessment of passive biceps brachii muscle stiffness: influences of sex and elbow position

ObjectiveTo assess differences in biceps brachii muscle (BBM) stiffness as evaluated by ultrasound shear wave elastography (SWE). MethodsThe passive stiffness of the BBM was quantified with shear wave velocity (SWV) measurements obtained from 10 healthy volunteers (5 men and 5 women, mean age 50years, age range 42–63 years) with the elbow at full extension and 30° flexion in this IRB-approved study. Potential differences between two depths within the muscle, two elbow positions, the two arms, and sexes were assessed by using two-tailed t-test. The reproducibility of SWV measurements was tested by using intraclass correlation coefficient (ICC). ResultsSignificantly higher passive BBM stiffness was found at full elbow extension compared to 30° of flexion (p≤0.00006 for both arms). Significantly higher passive stiffness in women was seen for the right arm (p=0.04 for both elbow positions). Good correlation of shear wave velocity measured at the different depths. The ICC for interobserver and intraobserver variation was high. ConclusionsSWE is a reliable quantitative tool for assessing BBM stiffness, with differences in stiffness based on elbow position demonstrated and based on sex suggested.

Empirical correlation of shear wave velocity (vs) with spt of soils in Madrid

Empirical correlations are usually used as a predictive tool in geotechnical engineering. However, equations calculated for soils very different to the ones to be characterized are frequently used, and so they are not representative of their mechanical properties. This fact, added to the increasing interest of civil engineering in knowing the shear wave velocity (Vs) of the ground, has led to the calculation of different empirical equations to predict the Vs value of the soils of Madrid. In this study this has been achieved by calculating the empirical correlations between the Vs value obtained through the ReMi (Refraction Microtremor) technique and the Standard Penetration Test (500 NSPT values). The empirical correlations proposed are applicable to the whole metropolitan area of Madrid, and have an excellent predictive capability owing to the incorporation of the measurement depth to the equations, which has an important influence in the resistance properties of soils. It is always better to have data collected in the studied site. But often there are too many difficulties to carry out some of these surveys. It may also happen that the surveys take too long or are too expensive to carry out. In these situations, empiric equations can be used to estimate this data. In geotechnical engineering, these empiric correlations are used frequently as a predictive tool, especially in the project’s design primary phases, when vast extensions of terrain are to be characterized in a short period of time, and to define if the soil fits a specific purpose. Because of this factor, there are plenty of estimations published that link between them different types of mechanical properties and geotechnical parameters.

Quantitative Assessment of Shear Wave Velocity Correlations in the Shallow Bedrock Sites

In this study shear wave velocity (V s ) and standard penetration test (SPT) N values up to the bedrock have been measured by multichannel analysis of surface wave and drilling of boreholes at 51 locations in shallow bedrock sites of South India, as part of the intraplate seismic region of India. Testing covers the major cities as Bangalore, Chennai, Coimbatore, and Vizag in South India. Drilling of boreholes in the above locations shows that the top surface consists of soft to very dense soil followed by very hard Granitic rock. N values are measured up to 100 and values beyond 100 were reported as rebound. Soil thickness of these locations varies from 1 m to about 20 m. The measured N and V s values are used to generate correlations between N and V s values for each city and also for the combined data by excluding and including SPT N of 100 for rebound layer. Further the applicability of the V s and N correlations developed for a particular site to other sites in the same region has been studied and it has been found that the site specific correlations are more accurate. The correlations developed for other cities display high percentages of error, even though the sites are similar in geology and soil type. Additionally, the developed empirical correlations have been compared with the existing worldwide correlations using logarithmic Euclidian distance (logED). The logED value has been estimated between the measured and calculated lower logED respectively for different cities and arrived the best suitable predictive equations for the four cities. Lower logED value between the measured and calculated V s corresponds to better empirical relationship.

Correlation of shear wave velocity with liquefaction resistance for silty sand based on laboratory study

Correlation of shear wave velocity with liquefaction resistance for silty sand based on laboratory study

Applicability of existing empirical shear wave velocity correlations to seismic cone penetration test data in Christchurch New Zealand

Seismic piezocone (SCPTu) data compiled from 86 sites in the greater Christchurch, New Zealand area are used to evaluate several existing empirical correlations for predicting shear wave velocity from cone penetration test (CPT) data. It is shown that all the considered prediction models are biased towards overestimation of the shear wave velocity of the Christchurch soil deposits, demonstrating the need for a Christchurch-specific shear wave velocity prediction model (McGann et al., 2014) [1]. It is hypothesized that the unique depositional environment of the considered soils and the potential loss of soil ageing effects brought about by the 2010–2011 Canterbury earthquake sequence are the primary source of the observed prediction bias.

Evaluation of Shear Wave Velocity Correlations and Development of New Correlation Using Cross-hole Data

Seismic microzonation studies are being proposed in Pakistan. In addition, a downhole array of accelerometers was planned to be installed in the University of Engineering and Technology, Mardan Campus. Therefore, extensive geotechnical and geophysical tests were conducted. Shear wave velocity (Vs) is a fundamental parameter required for these microzontation studies. It is feasible in terms of cost and space to determine Vs from Standard Penetration Test (SPT) or Cone Penetration Test (CPT) results through empirical correlations. The purpose of this paper is to explore the applicability and predictability of these correlations to the data collected from the area where downhole array is planned. Data from these surveys was used to evaluate relevant correlations selected from literature. Predicted shear wave velocity values from these correlations were compared with measured shear wave velocity values from seismic crosshole tests. Most SPT-Vs correlations evaluated showed low predictability. The SPT-Vs correlation that showed highest degree of fitness to the dataset was the one developed for Lucknow, India, a city with similar geological setting, workmanship and SPT method employed. Site specific SPT-Vs correlation was also proposed. Most of the CPT-Vs correlations evaluated showed considerable predictive capability compared to the SPT-Vs correlations.

Dynamic Site Characterization and Correlation of Shear Wave Velocity with Standard Penetration Test ‘N’ Values for the City of Agartala, Tripura State, India

Seismic site characterization is the basic requirement for seismic microzonation and site response studies of an area. Site characterization helps to gauge the average dynamic properties of soil deposits and thus helps to evaluate the surface level response. This paper presents a seismic site characterization of Agartala city, the capital of Tripura state, in the northeast of India. Seismically, Agartala city is situated in the Bengal Basin zone which is classified as a highly active seismic zone, assigned by Indian seismic code BIS-1893, Indian Standard Criteria for Earthquake Resistant Design of Structures, Part-1 General Provisions and Buildings. According to the Bureau of Indian Standards, New Delhi (2002), it is the highest seismic level (zone-V) in the country. The city is very close to the Sylhet fault (Bangladesh) where two major earthquakes (M w > 7) have occurred in the past and affected severely this city and the whole of northeast India. In order to perform site response evaluation, a series of geophysical tests at 27 locations were conducted using the multichannel analysis of surface waves (MASW) technique, which is an advanced method for obtaining shear wave velocity (V s) profiles from in situ measurements. Similarly, standard penetration test (SPT-N) bore log data sets have been obtained from the Urban Development Department, Govt. of Tripura. In the collected data sets, out of 50 bore logs, 27 were selected which are close to the MASW test locations and used for further study. Both the data sets (V s profiles with depth and SPT-N bore log profiles) have been used to calculate the average shear wave velocity (V s30) and average SPT-N values for the upper 30 m depth of the subsurface soil profiles. These were used for site classification of the study area recommended by the National Earthquake Hazard Reduction Program (NEHRP) manual. The average V s30 and SPT-N classified the study area as seismic site class D and E categories, indicating that the city is susceptible to site effects and liquefaction. Further, the different data set combinations between V s and SPT-N (corrected and uncorrected) values have been used to develop site-specific correlation equations by statistical regression, as ‘V s’ is a function of SPT-N value (corrected and uncorrected), considered with or without depth. However, after considering the data set pairs, a probabilistic approach has also been presented to develop a correlation using a quantile–quantile (Q–Q) plot. A comparison has also been made with the well known published correlations (for all soils) available in the literature. The present correlations closely agree with the other equations, but, comparatively, the correlation of shear wave velocity with the variation of depth and uncorrected SPT-N values provides a more suitable predicting model. Also the Q–Q plot agrees with all the other equations. In the absence of in situ measurements, the present correlations could be used to measure V s profiles of the study area for site response studies.

Neuro-fuzzy reaping of shear wave velocity correlations derived by hybrid genetic algorithm-pattern search technique

AbstractShear wave velocity is a critical physical property of rock, which provides significant data for geomechanical and geophysical studies. This study proposes a multi-step strategy to construct a model estimating shear wave velocity from conventional well log data. During the first stage, three correlation structures, including power law, exponential, and trigonometric were designed to formulate conventional well log data into shear wave velocity. Then, a Genetic Algorithm-Pattern Search tool was used to find the optimal coefficients of these correlations. Due to the different natures of these correlations, they might overestimate/underestimate in some regions relative to each other. Therefore, a neuro-fuzzy algorithm is employed to combine results of intelligently derived formulas. Neuro-fuzzy technique can compensate the effect of overestimation/underestimation to some extent, through the use of fuzzy rules. One set of data points was used for constructing the model and another set of unseen data points was employed to assess the reliability of the propounded model. Results have shown that the hybrid genetic algorithm-pattern search technique is a robust tool for finding the most appropriate form of correlations, which are meant to estimate shear wave velocity. Furthermore, neuro-fuzzy combination of derived correlations was capable of improving the accuracy of the final prediction significantly.

Statistical correlations of shear wave velocity and penetration resistance for soils

In this paper, the correlation between shear wave velocity and standard penetration test blow counts (SPT-N) is investigated. The study focused primarily on the correlation of SPT-N and shear wave velocity (Vs) for several soil categories: all soils, sand, silt and clay-type soils. New empirical formulae are suggested to correlate SPT-N and Vs, based on a dataset collected in a part of Eskişehir settlement in the western central Anatolia region of Turkey. The formulae are based on geotechnical soundings and active and passive seismic experiments. The new and previously suggested formulae showing correlations between uncorrected SPT-N and Vs have been compared and evaluated by using the same dataset. The results suggest that better correlations in estimation of Vs are acquired when the uncorrected blow counts are used. The blow count is a major parameter and the soil type has no significant influence on the results. In cohesive soils, the plasticity contents and, in non-cohesive soils except for gravels, the graded contents have no significant effect on the estimation of Vs. The results support most of the conclusions of earlier studies. These practical relationships developed between SPT-N and Vs should be used with caution in geotechnical engineering and should be checked against measured Vs.

Correlation of shear wave velocity with liquefaction resistance based on laboratory tests

According to the results of cyclic triaxial tests on Hangzhou sands, a correlation is presented between liquefaction resistance and elastic shear modulus. Material-dependent but independent of confining stress, shows the linear relation of ( σ d/2) 1/2 with G max. For its application to different soils, a method proposed by Tokimatsu [Tokimatsu K, Uchida A. Correlation between liquefaction resistance and shear wave velocity. Soils Found 1990:30(2):33–42] is utilized to normalize the shear modulus with respect to minimum void ratio. A simplified equation is established to evaluate the liquefaction potential by shear-wave velocity. The critical shear-wave velocity of liquefaction is in linear relation with 1/4 power of depth and the peak horizontal ground surface acceleration during earthquakes. The equation proposed in this paper is compared with previous methods especially the procedure proposed by Andrus [RD Andrus, KH Stokoe. Liquefaction resistance of soils from shear-wave velocity. J Geotech Geoenviron Eng 2000:126(11):1015–25]. The results show its simplicity and effectiveness when applied to sands, but more validation or modification is needed for its application to sand with higher fines content.