Soil Shear Wave Velocity Research Articles

GIS based Vs30, Vsz & Dbed rock Mapping for the Shallow Sites of Islamabad, Pakistan

The location of Pakistan is in a collision zone among the Eurasian and Indian plate boundaries. The geological framework of the Northwest Himalaya makes Northern Pakistan susceptible to frequent moderate to major earthquakes. The devastating earthquake of October 8, 2005 caused 87,000 deaths, 2.8 million displacements and financial loss of 200 Billion USD equivalent to 6% GDP of Pakistan. Islamabad is in seismically active region, the studies conducted for this region addresses the poor soil conditions, non-engineering construction practices and high level of seismic shaking. However, none of these studies provided readily available ground maps (top 30m time average shear wave velocity V s30 , average soil shear wave velocity V sz & depth to bed rock D bed rock ) based on site specific geotechnical database. V s30 , V sz & D bed rock are important parameters for the evaluation of dynamic site characteristics of shallow bed rock sites. In Pakistan, Uniform Building Code (UBC-1997) is currently practiced, and the site classification are defined using site specific V s30 . In this study, geotechnical borehole database of 57 sites of Islamabad was collected to develop GIS based V s30 , V sz & D bed rock maps using Standard Penetration Test value (SPT-N). The borehole database includes, SPT-N, soil description and unit weight of soil for the Islamabad sites. In order to develop shear wave velocity (V s ) profiles, the available V s -SPT empirical correlations were evaluated where both SPT-N & V s measured data is available. The selected available correlations were applied to SPT-N database to develop representative Vs profiles. Using these V s profiles, V s30 , V sz & D bed rock GIS based maps were developed by applying Kriging interpolation in open source QGIS software. The proposed GIS maps can be used in preliminary earthquake design for seismic resilient earthquake design in Islamabad, Pakistan.

Effect of soil-structure interaction on wind-induced responses of supertall buildings with large pile groups

A simplified three-dimensional soil-structural interaction (SSI) model is established for large pile groups-supertall buildings (>300 m height) to simulate the dynamic response of the building to wind loading. The displacement and acceleration responses to wind loading at the top of the supertall building are calculated using the established model. The effects of SSI on the wind-induced mean displacement, root-mean-square (RMS) displacement and RMS acceleration are analyzed considering different values of soil shear wave velocity and material damping, and different total mass, first natural frequency and damping ratio of the superstructure as well as different terrain conditions. The results from the comprehensive parametric study are used to derive empirical equations of the mean displacement, RMS displacement and RMS acceleration SSI factors. The findings demonstrate that the mean displacement of the top of supertall building increases considering SSI. As the soil shear wave velocity decreases, the mean displacement SSI factor increases. It was also found that the mean displacement SSI factor increases with the increase in total mass and first natural frequency of the superstructure. In addition, the RMS displacement and acceleration SSI factors decrease with the increase of the soil shear wave velocity and material damping. Finally, the RMS displacement and acceleration SSI factors increase as the superstructure first damping ratio increases.

Soil surface seismic hazard maps for the proposed site of Nasser New City, West Assiut, Egypt

The objective of this paper was to develop the soil surface seismic hazard maps for the proposed site of Nasser New City, West Assiut, based on probabilistic seismic hazard assessment, mainly in terms of the mean peak ground acceleration (PGA) and spectral acceleration (SA) values. Assessment of soil surface seismic hazard maps is required for disaster preparedness, risk, and hazard mitigation decisions for the study area. To carry out this assessment, soil profile is defined based on soil shear wave velocity that is global Vs30 of USGS. These velocities are converted to site classification based upon the National Earthquake Hazards Reduction Program (NEHRP) guidelines. A seismic hazard evaluation with level hazard 10% probability of exceedance in 50 years in terms of 5% damped peak ground acceleration and spectral acceleration was carried out, PGA and SA values at bedrock, at 0.1, 0.5, 1.0, and 2.0 s spectral period, were calculated at central part of Nasser New City. Using site amplification factors corresponding to various site classes based on Vs30, spatial variation of SA at spectral periods 0.1, 0.5, 1.0, and 2.0 s for 475 years as return period is demonstrated as maps. Results of this work are important for civil engineering purposes, land use planning, and resistant structure design for earthquake.

Establishing region-specific N – V relationships through hierarchical Bayesian modeling

The blow count ( N ) measured from the standard penetration test is widely used to predict the shear wave velocity ( V s ) of soils. As the N - V s relationships vary from one region to another, the N - V s relationship in a region is often determined based on the regional data. When there is no region-specific data or when the region-specific data is limited, such methods can hardly be applicable. In this study, a hierarchical Bayesian model based method is suggested to develop region-specific N - V s relationships which is applicable to regions without region-specific data and regions with limited region-specific data. The validity of the suggested method is verified using new data that has not been used for model calibration. It is found that the suggested method can be used to predict V s for a region with no region-specific data, but the uncertainty associated with V s could be large. On the other hand, a few region-specific data can significantly reduce the uncertainty associated with V s . When the amount of region-specific data is small, the N - V s relationship developed based on the method suggested in this paper is more reliable than the N - V s relationships developed based on two alternative methods. When the amount of region-specific data is large, a comparison between the N - V s relationship established by the suggested method and that developed based on regression analyses of the regional data may help identify the risk that the region-specific data may not be representative. • A database containing 2433 N - V s data pairs from 16 regions worldwide is compiled. • A method based on hierarchical Bayesian model is suggested to develop region-specific N - V s relationships. • The suggested method can be applied to regions without region-specific data. • The suggested method can be applied to regions with limited region-specific data. • The suggested method is superior totwo alternative methods.

Effects of soil–structure interaction on seismic performance of a low-rise R/C moment frame considering material uncertainties

This study investigated the effects of soil–structure interaction (SSI) on the performance of low-rise reinforced concrete (R/C) structures subjected to earthquakes. The uncertainty of material properties, such as steel yield and concrete compressive strengths, was addressed using the Monte Carlo simulation with Latin hypercube sampling. A planar R/C moment frame of three bays and three stories was subjected to 20 selected ground motions for this purpose. In the flexible-base models, the soil was modeled with springs and dashpots, and the mass and moment of inertia of the footing were lumped at the bottom of the column. In contrast, for the fixed-base model, the bottoms of the columns were fixed in all translational and rotational directions. A parametric study was conducted for the shear wave velocity of soil, varying from 1000 to 50 m/s. The responses of the flexible-base and fixed-base models were compared in terms of the ductility, maximum interstory drift, and maximum total drift (ratio of top displacement to building height) for three performance levels in ASCE 41-17: intermediate occupancy (IO), life safety (LS), and collapse prevention (CP). The pushover analysis results indicate that a higher shear wave velocity leads to a higher ductility capacity. The uncertainty of the material properties produces an extensive range of ductility factors. The seismic drift responses of the flexible-base models are larger than those of the fixed-base model, particularly in the range of shear wave velocities less than 180 m/s (i.e., soft soil). From the failure probability analyses, the threshold shear wave velocity below which the effects of SSI should be considered is approximately 180 m/s for IO and 100 m/s for both LS and CP.

A Methodology for Estimating the Position of the Engineering Bedrock for Offshore Wind Farm Seismic Demand in Taiwan

Taiwan lies in the circum-Pacific earthquake zone. The seabed soil of offshore wind farms in Taiwan is mainly composed of loose silty sand and soft, low-plasticity clay. The seismic demand for offshore wind turbines has been given by the local code. Ground-motion analysis is required to consider the site effects of the soil liquefaction potential evaluation and the foundation design of offshore wind turbines. However, the depth of the engineering bedrock for ground motion analysis is not presented in the local code. In this study, we develop a three-dimensional ground model of an offshore wind farm in the Changhua area, through use of collected in situ borehole and PS (P wave (compression) and S (shear) wave velocities) logging test data. The engineering bedrock is the sediment at the depth where the average shear wave velocity of soil within 30 m, Vsd30, is larger than 360 m/s. In this ground model, the shear wave velocity of each type of soil is quantified using the seismic empirical formulation developed in this study. The results indicate that the engineering bedrock lies at least 49.5–83 m beneath the seabed at the Changhua offshore wind farm. Based on these findings, it is recommended that drilling more than 100 m below the seabed be done to obtain shear wave velocity data for a ground response analysis of the seismic force assessment of offshore wind farm foundation designs.

Semi-empirical correlation of shear wave velocity prediction in the Yellow River Delta based on CPT

The Yellow River Delta is one of the most abundant offshore energy areas in China, and the construction of offshore projects is rapidly developing. In this paper, four typical regions of the Yellow River Delta in different periods were selected as research objects. In-situ cone penetration tests (CPTs), geotechnical testing, electron microscope scanning testing, and soil type indexing (Ic) was used to classify and identify the soil layers. At the same time, a modified calculation model based on CPT for the shear wave velocity of fine-grained seabed soil was sought and verified with the measured values. The results showed that: (1) the obtained soil layers are mainly classified by clay and silty soil, which is in line with the conclusions of previous scholars on the classification of the Yellow River Delta soil layer. (2) The measured shear wave velocity is generally between 100 m/s and 250 m/s, and it gradually increases with depth. (3) The depth, cone resistance, and soil behavior index are directly related to the calculation of the shear wave velocity in this area. (4) Discrete analysis of measured and calculated shear wave velocity provides theoretical support for the change of shear wave velocity under different conditions.

Implementation of Machine Learning Algorithms in Spectral Analysis of Surface Waves (SASW) Inversion

One of the complex processes in spectral analysis of surface waves (SASW) data analysis is the inversion procedure. An initial soil profile needs to be assumed at the beginning of the inversion analysis, which involves calculating the theoretical dispersion curve. If the assumption of the starting soil profile model is not reasonably close, the iteration process might lead to nonconvergence or take too long to be converged. Automating the inversion procedure will allow us to evaluate the soil stiffness properties conveniently and rapidly by means of the SASW method. Multilayer perceptron (MLP), random forest (RF), support vector regression (SVR), and linear regression (LR) algorithms were implemented in order to automate the inversion. For this purpose, the dispersion curves obtained from 50 field tests were used as input data for all of the algorithms. The results illustrated that SVR algorithms could potentially be used to estimate the shear wave velocity of soil.

Monitoring the strength properties of electrokinetically treated soil by bender elements to determine the treatment period

Bender elements have been used as a non-destructive soil investigation technique by many researchers and have proven to be effective in predicting the shear strength of various soils. In this paper, electrokinetic treatment tests were performed with embedded bender elements to monitor the increase in the shear strength of a soft sandy clay during the treatment. The bender element system, designed and assembled for this study, was integrated into the electrokinetic treatment process in order to quell a common uncertainty associated with this form of soil improvement technique, namely: when is the treatment completed? The cross-correlation and first-peak arrival times were used to measure the shear wave velocity of a clayey soil under the treatment of electrokinetics using bender elements. To determine shear wave velocity before and during treatment, a variety of shear wave tests were performed every hour of treatment using frequencies ranging from 100 Hz to 2500 Hz via the use of bender element. The results show that monitoring the soil improvement during the treatment by bender elements can shorten the treatment time by 43% and reduce the energy consumption, which is a major expenditure in an electrokinetic treatment process, by 33% while consistently improving the shear strength and the load capacity by approximately 200% and 300%, respectively.

Transmitting Characteristics of Seismic Motion in Super-Deep Overburden Layer Ground

Dynamic response characteristics and antiseismic performance of the structures which were constructed on the super-deep overburden layer are affected obviously by the seismic motion characteristics of the super-deep overburden layer foundation. In this paper, the seismic motion characteristics of horizontally stratified super-deep overburdenIn this paper, the seismic motion characteristics of horizontally stratified super-deep overburden based on the research results of on-site in situ tests and indoor material property tests, the horizontal shear layer method that can consider the nonlinear characteristics of dynamic soil deformation and the characteristics of seismic wave propagation in the soil is used to study the characteristics of ground motions of super-deep and thick overburden level of an earth-rock dam in China. The influence law of input ground motion characteristics and input ground motion position on seismic response analysis results of overburden ground is studied. Taking the uniform overburden layer model as an example, the coupling influence analysis of soil layer thickness and shear velocity on ground motion response are carried out, and the coupling influence law is proposed. The study shows that the seismic motion propagating characteristics of the earthquake in super-deep overburden layer is involved, inputting location of the seismic motion affects the results of ground seismic response greatly; super-deep overburden layer thickness and the soil shear wave velocity on influence law of ground motion characteristics have coupling. When the shear wave velocity of the soil layer is constant, the surface acceleration response has an inflection point with the change of the soil layer thickness; when the thickness of overburden is constant, the surface acceleration response also has an inflection point with the change of shear wave velocity of the soil layer; these inflexion values are influenced by both soil thickness and shear wave velocity.

Piezoelectric Ring Bender for Characterization of Shear Waves in Compacted Sandy Soils.

Shear wave velocity and small-strain shear modulus are widely used as the mechanical properties of soil. The objective of this study is to develop a new shear wave monitoring system using a pair of piezoelectric ring benders (RBs) and to evaluate the suitability of RB in compacted soils compared with the bender element and ultrasonic transducer. The RB is a multilayered piezoelectric actuator, which can generate shear waves without disturbing soils. For five compacted soil specimens, the shear waves are monitored by using three different piezoelectric transducers. Results of time-domain response show that the output signals measured from the RB vary according to the water content of the specimen and the frequency of the input signal. Except at the water content of 9.3%, the difference in the resonant frequencies between the three transducers is not significant. The shear wave velocities for the RB are slightly greater than those for the other transducers. For the RB, the exponential relationship between the shear wave velocity and dry unit weight is better established compared with that of the other transducers. The newly proposed piezoelectric transducer RB may be useful for the evaluation of the shear wave velocity and small-strain shear modulus of compacted soils.

Stress analysis of subsea risers under the combined action of wave force and seismic wave

The operational safety of subsea risers is challenged due to the complex environmental loads such as a current and seismic wave. This paper presents a comprehensive stress analysis of subsea risers under the combined action of wave and seismic waves. Considering the effect of wave and seismic wave load on maximum axial stress and bending stress of subsea risers, the force and the restraint on subsea risers are simplified. The time-dependent wave force on subsea risers is calculated, and the motion equation of subsea risers passing through a strong seismic zone is obtained. Then, the influencing factors of maximum axial stress and bending stress on subsea risers are studied using the finite-element model. The influence of subsea riser stress on shear wave velocity, diameter, wall thickness, bending angle, and properties of subsea soil is investigated. The results exhibit that the maximum stress appears at the elbow of the riser in the combined effect and the axial stress becomes greater than Mises stress. It is observed that the outcome can provide technical support for site construction in a specific area, and it is of great significance for pipe selection and optimization of subsea riser geometry.

Analysis of Coefficient of Dynamic Horizontal Subgrade Reaction and Correlation Factor (α) Considering Shear Wave Velocity of Soil

Analysis of Coefficient of Dynamic Horizontal Subgrade Reaction and Correlation Factor (α) Considering Shear Wave Velocity of Soil

Piezoelectric Ring-Actuator Technique: In-Depth Scrutiny of Interpretation Method

Abstract The piezoelectric ring-actuator technique (P-RAT) is a recent laboratory technique for the measurement of shear wave velocity (Vs) of soils. The measurement is based on transmission of a mechanical signal through the soil specimen with source and receiver transducers capsulated, for instance, in the end platens of an oedometer cell. An interpretative framework of the signals produced in the P-RAT has also been developed to minimize the subjectivity of the process and provide a consistent approach to Vs determination. However, there are some issues that would potentially affect the quality of the signals; consequently, biases of the velocity determination have not yet been explicitly discussed, such as the effects of sample and sensor characteristics as well as the signals used to excite the P-RAT sensors. P-RAT experiments on two different soils using different sensors, input signals, and oedometer cells are implemented in this study. The main purpose of the tests is not to elicit definitive information about the tested materials but to allow the P-RAT interpretation methodology to be revealed. The results suggest that this interpretation method can be beneficially used with other piezoelectric techniques (e.g., BE).

Global sensitivity analysis of probabilistic tunnel seismic deformations using sparse polynomial chaos expansions

There is an increasing interest in utilizing surrogate models to perform the global sensitivity analysis (GSA) for the uncertainty quantification since they allow to quantify efficiently the relative importance of each input parameter with relatively small computational costs. This paper aims at investigating the feasibility of applying this method to a stochastic soil-tunnel system in seismic conditions. An advanced technique named sparse polynomial chaos expansions (SPCE) is introduced to build a surrogate model that allows performing a GSA combined with the Sobol’ indices. The accuracy and efficiency of the SPCE-GSA method are validated by comparison with the true numerical predictions and Monte Carlo simulations. Parametric sensitivity analyses are performed for a wide range of the soil shear wave velocities, ground motion intensities, probability distribution types, and coefficients of variation, assuming a nonlinear soil behavior. The influences of the sampling size, polynomial degree, and ground motion characteristics on the variability in the sensitivity indices are evaluated. The results show that the soil shear wave velocity and modulus reduction factor are the two variables that significantly affect the seismic deformations of tunnels.

Measuring soil bulk density from shear wave velocity using piezoelectric sensors

Bulk density and soil stiffness moduli are vital physical parameters related to soil compaction, porosity, moisture storage capacity, soil penetration resistance and structural integrity. Conventional methods for measuring soil density and stiffness moduli are destructive, time-consuming, complex, expensive and often require skilled operators to conduct the tests. A new soil density and stiffness moduli measurement technique that can evaluate soil density and stiffness moduli more rapidly, efficiently and precisely, at a low cost is introduced here. This study evaluated the use of shear wave velocity measurements using the piezoelectric extender and bender elements as a viable alternative to measure soil density and stiffness moduli of soil. To test this idea, soda-lime glass beads of <0.002, 0.04–0.07 and 1.00–1.30 mm in diameter were used to develop the empirical relationship between the shear wave velocity and the bulk density of soil in laboratory conditions. These empirical equations were then tested on sands and clayey soils for validation. Accuracy in terms of coefficient of determination (R2) and root mean squared error (RMSE) from the current and existing studies ranged within 0.91–0.93 and 0.073–0.177 g cm–3 respectively. Both shear and Young moduli were compared with the shear wave velocity of soil, with R2 and RMSE of 0.96–0.97 and 0.48–3.5 MPa respectively. The major advantage of this technique is that input and output signal data can be stored in a computer that can be used to calculate soil density and stiffness moduli automatically. This technique could play a vital role in improving crop yield and soil management practices.

Experimental study and numerical simulation on dynamic soil‐structure interaction under earthquake excitations

Soil-structure interaction (SSI) phenomena subjected to seismic loadings are investigated in this study. Firstly, shaking table tests on dynamic soil‐structure interaction subjected to seismic loadings are carried out, and SSI effects are analyzed through a comparative study between the soil-structure system and the rigid foundation condition. Then, a corresponding numerical model on the SSI tests is presented. In the finite element model, a bounding surface plasticity model and an equivalent linear method are separately used for simulating the nonlinear behavior of soil. It turns out that the calculated results by the bounding surface plasticity model agree much better with the experimental results. Finally, the effects of different soil types and structural properties on soil-structure interaction are discussed by numerical parametric study. The results show that SSI effects noticeably mitigate the dynamic response of structure, and the closer the frequency of superstructure to the soil frequency, the more obvious the effect of soil-structure interaction. With increased shear wave velocity of soil, the impact of soil-structure interaction weakens. It is important for studying the impact of SSI on structural responses and practical engineering design purposes.

Characteristics of spatial variability of shear wave velocity on seismic response of slopes

The soil shear wave velocity has long been recognized as an effective parameter in the assessment of the seismic response of slopes. However, most seismic analyses have been carried out by deterministic models considering just a single realization of soil shear wave velocity. In other words, only a small number of researchers have explored the spatial variability effects of soil shear wave velocity on the seismic response of slopes. This paper investigates this phenomenon stochastically, and the auto-correlation matrix decomposition method based on Monte Carlo Simulation was applied to generate the stationary random fields in order to simulate the spatial variability of soil shear wave velocity. This framework includes interpreting the coefficient of the soil shear modulus variation and auto-correlation length effected on maximum horizontal equivalent acceleration. The results showed that the spatial variation of shear wave velocity might have a significant effect on the dynamic response of the sliding mass if slopes were subjected to weak ground motions. By contrast, it could have a significant effect on maximum horizontal equivalent acceleration induced in slopes subjected to intense ground motions.

Effects of soil dynamic response on post-earthquake deformation of slopes based on nested Newmark model

Nested Newmark model (NNM) can obtain the post-earthquake profile of the slopes in limit equilibrium or limit analysis method. The purpose of this study is to extend the NNM from the limit equilibrium method to a limit analysis method, and then involve the dynamic response of slopes into the prediction of the permanent displacement based on decoupled analysis. Parametric studies are carried out to further investigate the influences of slope height, soil shear wave velocity and input ground motion. The calculated results indicate that neglecting the dynamic response of slopes can underestimate the post-earthquake displacements. As the slope height increases or shear wave velocity reduces, the underestimation is more significant. At the fundamental natural period of the site, the underestimation is particularly remarkable. For induced earthquake waves with a small value of mean period, the influence of the dynamic response can be ignored when the fundamental period deviates from the mean period.

Experimental study on soil improvement using local microorganisms

Bio-mediated soil improvement has been recently introduced as a novel link between biotechnology and geotechnical engineering. Microbial induced carbonate precipitation (MICP) is one of the most promising bio-mediated methods which have been developed based on biologically driven urea hydrolysis. In the present study, an indigenous bacterium that can be used in MICP is identified in the native soil of Sirjan, Southern Iran. This bacterium, called Acinetobacter calcoaceticus Nima (ACN), was compared with the standard Sporosarcina pasteurii (SP), with respect to their performance in the improvement of the mechanical properties of biologically treated soil samples. During a 40-day period of the experiment, direct shear and shear wave velocity tests were conducted to investigate the influence of the treatments on soil properties. Also, stereo microscope images were used to investigate the precipitation on the inter-particle contacts. It was observed that the bio-mediated techniques can significantly improve the mechanical properties of the soil samples. For instance, while the shear wave velocity of the bacteria-free soil was measured as 175 m/s, SP-treated soil has the shear wave velocity of 526 m/s. This value was even higher for the ACN-treated samples (588 m/s) indicating that the local bacteria performed considerably better than the standard SP when used for the native soil.