Shear Wave Velocity Measurements Research Articles

Predicting Earthquake-Induced Soil Liquefaction Based on Machine Learning Classifiers: A Comparative Multi-Dataset Study

The study and prediction of soil liquefaction is an important and complex issue in geotechnical earthquake engineering. This paper attempts to compare the predictability of soil liquefaction potential between several machine learning classification models, which includes some tree-based classifiers, multilayer perceptron (MLP) neural networks, Support Vector Machine (SVM), some state-of-the-art ensemble methods, K nearest neighbors method, classical Naive Bayesian classifier and logistic regression. Three data sets covering shear-wave velocity measurements, cone penetration testing (CPT), and real historic earthquakes cases are employed to train and evaluate the machine learning classifiers. In order to make the best use of large varieties of statistical and machine learning classification algorithms, it is necessary to give a comparative evaluation of the model performance before model selection and offer advice on a unified stable model for all sorts of collected datasets. In the comparative study, data preprocessing is first performed to ensure the dataset into all machine models is of good quality. Then all three datasets with different input features are passed into the machine learning algorithms to obtain its confusion matrix and some evaluation indices. Reliable assessment of model performance is done through a repeated sub-sampling process. Experimental results are also supported by ROC curves. The results of this study indicated that although most machine learning methods are able to represent the complex relationship between seismic proper seismic properties of soils and corresponding liquefaction potential, ensemble learning has achieved more successful results in all three datasets test and can be a fairly promising approach on prediction of earthquake-induced soil liquefaction.

Verification of Seismic Cone Penetration Test Calibration Chamber Tests on a Sand

Abstract Calibration chambers are experimental apparatuses that allow the physical modeling of an in situ testing method, such as the cone penetration test (CPT), by performing laboratory experiments on soil samples with known stress, strain, and density characteristics. Over a series of development and improvements, more recent calibration chambers and laboratory cone penetrometers have become compact and less laborious than their predecessors. This includes the focus of this study where a miniature cone penetration testing (MCPT) calibration chamber previously designed and used at Western University is upgraded to measure shear wave velocity (VS) and enable anisotropic consolidation of soil specimens using a hydraulic piston. In addition to VS, MCPT can also measure cone tip resistance, sleeve friction, and excess pore water pressure developed behind the cone tip. A full test plan using the newly upgraded MCPT calibration chamber is presented in this study. These tests are performed on Fraser River sand at various relative densities and effective stresses. Results of this testing program are validated by comparison with a series of in situ seismic CPTs in the Fraser River delta, existing correlations between VS and cone tip resistance, and several other calibration chamber tests on different sands. Through these comparisons, the overall viability of the initial MCPT calibration chamber design, modifications made to the MCPT setup, and ultimately the results produced from this device are confirmed.

Application of wave equation theory to improve dynamic cone penetration test for shallow soil characterisation

Among the geotechnical in situ tests, the dynamic penetration test (DPT) is commonly used around the world. However, DPT remains a rough technique and provides only one failure parameter: blow count or cone resistance. This paper presents an improvement of the dynamic cone penetration test (DCPT) for soil characterisation based on the wave equation theory. Implemented on an instrumented lightweight dynamic penetrometer driving with variable energy, the main process of the test involves the separation and reconstruction of the waves propagating in the rods after each blow and provides a dynamic cone load-penetration (DCLT) curve. An analytical methodology is used to analyse this curve and to estimate additional strength and deformation parameters of the soil: dynamic and pseudo-static cone resistances, deformation modulus and wave velocity. Tests carried out in the laboratory on different specimens (wood, concrete, sand and clay) in an experimental sand pit and in the field demonstrated that the resulting DCLT curve is reproducible, sensitive and reliable to the test conditions (rod length, driving energy, etc.) as well as to the soil properties (nature, density, etc.). Obtained results also showed that the method based on shock polar analysis makes it possible to evaluate mechanical impedance and wave velocity of soils, as demonstrated by the comparisons with cone penetration test (CPT) and shear wave velocity measurements made in the field. This technique improves the method and interpretation of DPT and provides reliable data for shallow foundation design.

Laboratory-scale seismic CPT calibration chamber tests on Fraser River sand

Physical modeling of cone penetration testing (CPT) can be carried out under known stress, deformation, and density conditions using laboratory calibration chambers. This study presents the results of reduced-scale model CPTs (MCPT) on Fraser River sand using a calibration chamber that allows anisotropic consolidation of soil specimens, as well as the measurement of shear wave velocity (VS), using bender elements. In addition to VS, MCPT can also measure cone tip resistance (qc), sleeve friction (fs), and pore water pressure developed behind the cone tip (Δu2). The CPT model tests are performed on Fraser River sand at different effective stresses and relative densities. The CPT calibration chamber test results are comparable with those of in situ seismic cone penetration tests (SCPT) in the Fraser River delta, existing correlations between VSand qc, and calibration chamber tests on other sands. This confirms the overall feasibility of the MCPT calibration chamber design for the measurements of qc, fs, and VSin sandy soils.

Shear-Wave-Elastography in Neurofibromatosis Type I.

Ultrasound shear wave elastography (SWE) is an increasingly used imaging modality that expands clinical ultrasound by measuring the elasticity of various tissues, such as the altered elasticity of tumors. Peripheral nerve tumors are rare, have been well-characterized by B-mode-ultrasound, but have not yet been investigated with SWE. Given the lack of studies, a first step would be to investigate homogeneous peripheral nerve tumors (PNTs), histologically neurofibromas or schwannomas, which can occur in multiple in neurofibromatosis type 1 and 2 (NF1 and 2), respectively. Hence, we measured shear wave velocity (SWV) in 30 PNTs of 11 patients with NF1 within the median nerve. The SWV in PNTs ranged between 2.8 ± 0.8 m/s and correlated with their width and approximate volume but not with their length or height. Furthermore, we determined the extent to which PNTs alter the SWV of the median nerve for three positions of the wrist joint: neutral (zero-degree), individual maximal flexion and maximal extension. Here, SWV was decreased in NF1 patients compared to age- and sex-matched controls (p = 0.029) during maximal wrist extension. We speculate that the presence of PNTs may have a biomechanical impact on peripheral nerves which has not been demonstrated yet.

A method for simultaneous measurements of compressional wave and shear wave velocities in rocks and minerals at high pressure and high temperature: A modification to the combined transmission-reflection method

We present a modification to the combined transmission-reflection method, which is frequently used to measure the elastic wave velocities in rocks and minerals at high pressure and high temperature in multi-anvil apparatus. The modification mainly focuses on the adoption of dual-mode ultrasonic transducer and new backing reflector (a molybdenum foil), the former was used to simultaneously measure the travel times of compressional wave and shear wave in the sample, and the latter was used to intensify the reflection signals of the buffer rod. The correction time of the molybdenum foils was determined using the equation of state and highpressure velocities of molybdenum. In addition, the length change of sample under high pressure was also taken into account. Using this method, we simultaneously measured the compressional wave and shear wave velocities in Z-cut a-quartz single crystal to 2 GPa at room temperature, and natural mafic granulite sample to 1.4 GPa and 500�C in a multianvil apparatus. The results of this work agree well with those of previous measurements and demonstrate the feasibility of this new method. We believe that by using this method, more accurate elastic properties of rocks and minerals under high pressure and high temperature can be obtained, especially Poisson�s ratio.

Liquefaction Evaluation Based on Shear Wave Velocity Using Random Forest

Liquefaction evaluation on the sands induced by earthquake is of significance for engineers in seismic design. In this study, the random forest (RF) method is introduced and adopted to evaluate the seismic liquefaction potential of soils based on the shear wave velocity. The RF model was developed using the Andrus database as a training dataset comprising 225 sets of liquefaction performance and shear wave velocity measurements. Five training parameters are selected for RF model including seismic magnitude ( M w ), peak horizontal ground surface acceleration ( a max ), stress-corrected shear wave velocity of soil ( V s 1 ), sandy-layer buried depth (ds), and a new introduced parameter, stress ratio (k). In addition, the optimal hyperparameters for the random forest model are determined based on the minimum error rate for the out-of-bag dataset (ERROOB) such as the number of classification trees, maximum depth of trees, and maximum number of features. The established random forest model was validated using the Kayen database as testing dataset and compared with the Chinese code and the Andrus methods. The results indicated that the random forest method established based on the training dataset was credible. The random forest method gave a success rate for liquefied sites and even a total success rate for all cases higher than 80%, which is completely acceptable. By contrast, the Chinese code method and the Andrus methods gave a high success rate for liquefaction but very low for nonliquefaction which led to the increase of engineering cost. The developed RF model can provide references for engineers to evaluate liquefaction potential.

The Influence of Gas Hydrate Morphology on Reservoir Permeability and Geophysical Shear Wave Remote Sensing

AbstractWe show that direct estimates of the permeability of hydrate‐bearing geological formations are possible from remote measurements of shear wave velocity (Vs) and attenuation (Qs−1). We measured Vs, Qs−1 and electrical resistivity at time intervals during methane hydrate formation in Berea sandstone using a laboratory ultrasonic pulse‐echo system. We observed that Vs and Qs−1 both increase with hydrate saturation Sh, with two peaks in Qs−1 at hydrate saturations of around 6% and 20% that correspond to changes in gradient of Vs. We implemented changes in permeability with hydrate saturation into well‐known Biot‐type poro‐elastic models for two‐ and three‐phases for low (Sh < 12%) and high (Sh > 12%) hydrate saturations respectively. By accounting for changes in permeability linked to hydrate morphology, the models were able to describe the Vs and Qs−1 observations. We found that the first Qs−1 peak is caused by a reduction of permeability during hydrate formation associated with a transition from pore‐floating to pore‐bridging hydrate morphology; similarly, the second Qs−1 peak is caused by a permeability reduction associated with a transition from pore‐bridging hydrate morphology to an interlocking network of hydrate in the pores. We inverted for permeability using our poro‐elastic models from Vs and Qs−1. This inverted permeability agrees with permeability obtained independently from electrical resistivity. We demonstrate a good match of our models to shear wave data at 200 Hz and 2 kHz frequencies from the literature, indicating the general applicability of the models.

Prediction of Soil Settlement using Numerical Modelling Based on Shear Wave Velocity Measurement

The method of Spectral Analysis of Surface Wave (SASW) is a seismic method that consider as a non-destructive geotechnical technique to determine the soil profile based on the shear wave velocity profile by utilizing the dispersive characteristic of Rayleigh wave through the soil medium. The shear wave velocity was found to be directly proportional to the strength of the soil. In this research, SASW measurement had been proposed to predict the soil settlements using numerical modelling. The frequency responses from SASW were acquired for shear wave profile analysis using WinSASW software. Thus, the borehole information which near to the conventional pile method and SASW were taken as the reference of the study. In obtaining the correlated N-value, equation that developed from previous research was used with the reference of N-SPT value. Hence, the correlated N-values were carried forward to obtaining the bearing capacity of foundation. Meanwhile, the numerical modelling has been developed in PLAXIS software in obtaining the soil settlement. The prediction of soil settlements of Site 1, Site 2 and Site 3 that calculated by conventional equation and modelled using PLAXIS were 0.003mm and 0.001mm, 0.002mm and 0.004mm, 0.003mm and 0.004m respectively. Based on the result obtained, this research has shown the potential used of shear wave velocity in the prediction of soil settlement.

New Approach to Concurrent VS and VP Measurements Using Bender Elements

Abstract Bender elements (BEs) have become a routine geotechnical laboratory tool for seismic wave velocity measurements. Since the 1980s, this testing technique has gained popularity, currently being available in many geotechnical laboratories worldwide in a variety of apparatuses. The advantage of simultaneously measuring small- and large-strain soil stiffnesses in each device and the easiness and low-cost implementation of BE are the main reasons for their common application. Although there is already a standardized procedure for BE testing (ASTM D8295-19, Standard Test Method for Determination of Shear Wave Velocity and Initial Shear Modulus in Soil Specimens Using Bender Elements), the use of high-frequency pulses for the simultaneous measurement of compressional (VP) and shear (VS) wave velocities is not considered. In contrast, the use of high-excitation frequencies is usually discouraged, as they tend to induce spurious participation of high-vibration modes in the BE response. However, this work shows that the use of higher vibration modes can be advantageous to evaluate P-wave velocities from standard BE testing. Thus, this paper presents a new approach for the concurrent measurements of VP and VS using a typical installation of BE. The new approach is first demonstrated by experimental measurements and subsequently validated using high-frequency laser vibrometer measurements of the actual BE deformation (nanometer scale) under different excitation frequencies. The laser vibrometer measurements show the displacements of the transmitter BE as a function of the input frequency in not only the horizontal but also in the vertical directions, demonstrating the generation of P-waves when higher vibration modes are excited. The measured VP values are shown to be in good agreement with the predicted values using Biot’s equations. Thus, the proposed methodology addresses the current knowledge gap in the use of BE for concurrent P-wave and S-wave velocity measurements. The generated wavelengths are large enough to travel through the soil skeleton instead of the pore water only.

Shear wave velocity measurements obtained in different regions are repeatable for presumed normal canine lymph nodes: A pilot study.

Shear wave elastography (SWE) has been applied as a noninvasive method for predicting regional lymph node (LN) metastases in human and veterinary patients. However, published studies describing standardized protocols and repeatability of this technique are currently lacking. The objective of this prospective, pilot, observer agreement study was to determine whether different shear wave velocity (SWV) measurements obtained in different regions of presumed normal canine LNs would be repeatable. Two imagers consecutively performed shear wave elastography of submandibular, superficial inguinal, and popliteal LNs in 10, clinically healthy adult dogs. Ten elastograms of each LN were acquired by each imager. In each adequate elastogram, three regions of interest (ROIs) were placed in the softest and stiffest region of the LN. Additionally, one ROI was drawn covering the entire LN. In each ROI, mean, median, and maximum SWVs were calculated. Mean values for the mean, median, and maximum SWVs varied from 2.33 to 3.10 m/s, 2.32 to 3.10 m/s, and 2.61 to 4.09 m/s, respectively. Intra- and interobserver agreements were acceptable. Superficial inguinal LNs demonstrated the highest intra- and interobserver agreement, followed by the popliteal and the submandibular LNs, respectively. Using the different measurements (mean, median, or maximum SWVs) had no significant effect on the intra- and interobserver variability, neither did the region (softest, stiffest, or entire LN). Findings indicated that all evaluated measurements and regions could be used to obtain reliable elastography data of presumed normal canine LNs. Clinical trials in dogs with cancer are necessary to compare SWVs of metastatic LNs with the reported SWVs and evaluate whether various measurements and regions can also be used in metastatic LNs.

Changes in placental elastography in the third trimester - Analysis using a linear mixed effect model.

Research into the role of ultrasound elastography to assess compromised placental tissue is ongoing. There is particular interest in evaluating its potential in the investigation of changes associated with uteroplacental dysfunction. To date, there is limited data on how different maternal and fetal considerations, such as advancing gestational age, amniotic fluid Index (AFI) and maternal body mass index (BMI) may influence shear wave velocity (SWV) measurements. This study aimed to evaluate longitudinal changes in SWV throughout gestation and model these changes with other developing fetal and maternal physiological and biological characteristics. The study utilised 238 singleton pregnancies and collected longitudinal data at repeated intervals in the 3rd trimester representing 629 individual data points. Linear mixed model regression analysis was used to identify significant predictors for SWV. From a total of ten variables selected for modelling, only gestational age, AFI, BMI, and sample depth were found to be significant predictors of placental SWV, and gestational age and AFI were found to have only a minimal impact on SWV. Sophisticated statistical modelling demonstrates that many of the expected maternal and fetal changes in the 3rd trimester have no or minimal impact on placental SWV. Understanding which factors influence placental SWV is essential to ascertain the technique's utility in managing pregnancies complicated by placental dysfunction in the future.

Bidirectional Shear Wave Velocity Measurements to Track Fabric Anisotropy Evolution of a Crushed Silica Sand during Shearing

AbstractContinuous bidirectional shear wave velocity measurements were performed in the vertical (V) and horizontal (H) directions to characterize fabric evolution of triaxial soil specimens during...

Incorporating dwelling mounds into induced seismic risk analysis for the Groningen gas field in the Netherlands

In order to inform decision-making regarding measures to mitigate the impact of induced seismicity in the Groningen gas field in the Netherlands, a comprehensive seismic risk model has been developed. Starting with gas production scenarios and the consequent reservoir compaction, the model generates synthetic earthquake catalogues which are deployed in Monte Carlo analyses, predicting ground motions at a buried reference rock horizon that are combined with nonlinear amplification factors to estimate response spectral accelerations at the surface. These motions are combined with fragility functions defined for the exposed buildings throughout the region to estimate damage levels, which in turn are transformed to risk in terms of injury through consequence functions. Several older and potentially vulnerable buildings are located on dwelling mounds that were constructed from soils and organic material as a flood defence. These anthropogenic structures are not included in the soil profile models used to develop the amplification factors and hence their influence has not been included in the risk analyses to date. To address this gap in the model, concerted studies have been identified to characterize the dwelling mounds. These include new shear-wave velocity measurements that have enabled dynamic site response analyses to determine the modification of ground shaking due to the presence of the mound. A scheme has then been developed to incorporate the dwelling mounds into the risk calculations, which included an assessment of whether the soil-structure interaction effects for buildings founded on the mounds required modification of the seismic fragility functions.

Evolution of the optimum ultrasonic testing frequency of alkali-activated soil–ash

Monitoring the curing process of mixtures produced by soil, fly ash and alkaline solution can be effectively performed by ultrasonic measurements of compression and shear wave velocities. These measurements detect the evolution of stiffness with time, as a result of alkali-activated ash reactions. Conventionally, ultrasonic testing relies on the use of a fixed input frequency, corresponding to the nominal frequency of the transducer, for which a maximum response is expected from the transducers. This procedure, however, has shown some limitations especially when applied to materials under curing, in which stiffness is changing with time. To overcome these limitations, a wide range of frequencies, from 24 to 200 kHz, was used at each of the selected curing periods for determining wave travel time, instead of a single frequency reading. The results show a clear increase in the optimum frequency with curing time, indicating that the ultrasound testing frequency should be adjusted to account for the stiffness increase due to curing. Additionally, the use of frequencies other than the nominal frequency of the ultrasonic transducers generated clearer signals, particularly at early curing periods.

Cyclic shearing behavior and dynamic characteristics of a fibrous peat

Cyclic shearing behavior, dynamic characteristics, and post-cyclic volume change of a peat sublayer from the Port Lands area of Toronto (Ontario, Canada) are investigated in this study. Laboratory specimens are trimmed from block samples collected from a depth of about 4.0 to 4.5 m. Constant-volume cyclic direct simple shear tests indicate an initial reduction of effective stress with number of stress cycles. However, the corresponding excess pore pressure ratios do not exceed 60%, indicating a cyclic mobility behavior in the peat specimens. Maximum shear moduli of the peat samples are also determined from shear wave velocity measurements. Post-cyclic volumetric strain, as well as the variations of secant modulus, modulus reduction, and damping ratio of the peat, are presented in terms of cyclic shear strain and compared with other studies. Empirical relationships are proposed for characterizing the shear modulus and damping ratio of Toronto peat.

Effect of Soft Viscoelastic Biopolymer on the Undrained Shear Behavior of Loose Sands

Soft viscoelastic biological products such as biopolymers and biofilms have recently garnered significant interest as alternative biogrout materials for ground improvement because of their nontoxic and biodegradable characteristics. However, the impact of soft gel-like viscoelastic pore fillers on the undrained response of treated soils remains poorly understood. This study involves undrained triaxial compression tests with concurrent shear wave velocity measurements of loose contractive sands treated with soft gelatin. The specimens experience two distinct loading-gelation sequences, either consolidation before gelation (CbG) or confinement after gelation (CaG). Results reveal that the shear wave velocity can be used as an indicator of the effective stress carried by the granular skeleton. The inclusion of the viscoelastic biopolymer hinders the contractive tendency, diminishes postpeak softening, and increases the undrained shear strength of loose contractive sands. These effects become more pronounced for stiffer biopolymers because they provide an enhanced skeletal support against chain buckling and contraction. The presence of biopolymers increases the normalized undrained shear strength from Su/σo′=∼0.1 to ∼1.4, particularly at low effective confining stress. The biopolymers alter the terminal state in the p′-q-e space. Therefore, critical states should be reconsidered for biopolymer-treated sands. The confinement-gelation sequence affects the effective stress supported by the granular frame and thus has pronounced effects on the undrained shear strength. This suggests the potential use of viscoelastic pore fillers as an effective treatment of loose sands prone to liquefaction.

Acoustic radiation force impulse elastography findings of achilles tendon in patients with hypothyroidism

Introduction
 The aim of our study was to investigate the effect of thyroid dysfunction on tendons and the contribution of Acoustic Radiation Force Impulse (ARFI) elastography to the diagnosis of tendinopathy.
 Methods
 Eighty Achilles tendons of 40 patients under levothyroxine treatment, who had previously known hypothyroidism but high serum thyroid stimulating hormone levels, and 80 Achilles tendons of 40 healthy individuals were evaluated with ARFI (Virtual Touch Quantification®). 19 of 40 of the patients with hypotiroidism’ Achilles tendons were re-evaluated after thyroid stimulating hormone levels reached to normal limits following the adjustments in thyroid hormone replacement therapy. The middle portion of the each Achilles tendon was chosen for the examination. Every examination consisted of three to five independent measurements (shear wave velocity- meters per second). The mean shear wave velocity value was calculated for each tendon, and used for statistical analysis.
 Results
 The stiffness values of both left and right Achilles tendons, represented as shear wave velocity, were similar in patients with hypothyroidism and control group. There was no significant difference between the Achilles tendon shear wave velocity measurements of 19 of 40 hypothyroidism patients who were re-evaluated after the adjustments in thyroid hormone replacement therapy.
 Conclusions
 The lack of significant difference in Achilles tendon stiffness between non-naive hypothyroid patients and the control group may be explained as a positive clinical effect of thyroid hormone replacement therapy.

The course and prognostic value of increased pancreas stiffness detected by ultrasound elastography during acute pancreatitis

BackgroundIn this study, we determined the pancreatic stiffness (PS) changes in the course of acute pancreatitis (AP) by ultrasound elastography and evaluated its relation with prognosis. Material/methodsPancreatic shear wave velocity measurements (SWM) were evaluated at the time of admission to the hospital, following clinical improvement, and one-month after for AP patients and compared to healthy volunteers. Its relationship with clinical severity indexes was evaluated. ResultsThe pancreatic SWM value in the healthy group was 7.72 ± 2.50 kPa, and in AP group was 10.97 ± 2.26 kPa (p = 0.000). There was no difference between mild and severe pancreatitis. The mean SWM was 8.96 ± 1.53 kPa after disease remission, and 8.83 ± 1.24 kPa after 1-month. ConclusionsPS increases significantly during AP and decreases with clinical improvement, but this was still higher than controls, and it kept its elevation after 1-month. We think that larger, long-term studies are needed to determine the clinicopathological significance of this.

Ultrasound Shear Wave Elastography of the Tongue during Selective Hypoglossal Nerve Stimulation in Patients with Obstructive Sleep Apnea Syndrome

Currently, there is no established technique to directly measure extrinsic tongue muscle activation during selective hypoglossal stimulation therapy (sHNS) in patients with obstructive sleep apnea syndrome (OSAS) in a simple, non-invasive clinical setting. Ultrasound shear-wave elastography (US-SWE) enables quantitative measurement of tissue stiffness. We investigated whether US-SWE is able to detect changes in muscle stiffness of the tongue during sHNS. Patients with OSAS treated with sHNS were prospectively enrolled. A standardized US-SWE protocol was used to selectively measure tissue stiffness of the geniohyoid muscle (GH) and genioglossus (GG) muscles on the side of stimulator implantation (sGH, sGG) and on the contralateral side (nGH, nGG) without and with sHNS. Eighteen patients were included (median age = 62 years, interquartile range: 56–65, 83.3% male). Median shear-wave velocity (SWV) increased during contraction with each patient's clinically prescribed therapeutic regimen in the sGH (+19%, p = 0.020) and sGG (+81%, p < 0.001) and decreased during contraction in the nGH (–8%, p = 0.107) and nGG (–8%, p = 0.396). Differences in SWV during contraction were significant only on the side of stimulation (sGG +81%, sGH +19%). SWE measurements had excellent reliability as reflected by a Cronbach α value ≥0.9 for all target muscles pre- and post-contraction and an item–total correlation ≥0.5. US-SWE allows reliable measurement of SWV as an indicator of muscle stiffness of extrinsic tongue muscles. This non-invasive method provides new possibilities to distinguish and characterize responders from non-responders in hypoglossal stimulation therapy. Compared with the regular visual assessment of tongue movement, US-SWE of individual muscle groups provides a new non-invasive imaging tool in patients with OSAS.