Transient Surface Wave Research Articles

Deep learning-based inversion of soil and rock compaction density utilizing Falling Weight Deflectometer (FWD) and Surface Waves

Methods relying on a single dynamic parameter to estimate the material density for the compaction quality testing of earth-rock dams and roadbed projects, present certain limitations in terms of applicability, testing accuracy, and work efficiency. The theory of elastic wave propagation reveals that the compaction density of the medium results from the combined interaction of multiple material properties. This study proposes a method that utilizes the transient surface wave method and a vehicle-mounted Falling Weight Deflectometer (FWD) to jointly enhance the accuracy of soil and rock material compaction detection. The transient surface wave method is employed to extract surface wave velocity and compressional wave velocity. The analysis of the FWD signal involves extracting dynamic parameters closely related to material density, including stiffness coefficients, central frequencies, and stiffness impedances, from time-domain, frequency-domain, and mechanical impedance analyses. A fully connected deep neural network is introduced to intelligently estimate the compaction density. The deep learning model is optimized by selecting the optimal activation function and optimization algorithm, as well as additional tuning. Extensive testing shows that deep learning model produce results closely approximating the true compaction density values. The average relative errors for the wet density and the dry density are 2.9% and 2.85%, respectively, meeting the quality control requirements for density testing. The proposed approach enables rapid detection and control of the compaction quality of soil and rock materials, providing a new method for the in-situ rapid detection of compaction quality.

High-density analysis of surface wave profile imaging based on a multiple coverage common-midpoint signal-couple array

Surface wave exploration technology has been extensively used in the inspection of construction engineering quality and shallow surface surveys. To enhance the efficiency of surface wave exploration field acquisition and achieve high-precision and high-density surface wave profile imaging, a wireless distributed seismic surface wave signal acquisition system has been developed based on the principles of active source transient surface wave signal acquisition and dispersion curve calculation methods. For the purpose of achieving rapid multiple coverage signal acquisition and enhancing fieldwork efficiency, a method for rapidly configuring common-midpoint signal couples (CMCs) for multiple coverage common-shot signal acquisition has been devised, and a high-precision visualization method for dispersion curve calculation based on the CMC array has been formulated. When compared with the multichannel analysis of the surface wave method under identical conditions, the CMC array can effectively enhance surface wave dispersion curve survey station density and lateral resolution, thereby enabling high-density analysis of surface wave profile imaging. Through model analysis and field examples related to construction quality detection, including foundation compactness and earth and rock mixture compactness, it has been demonstrated that this method offers significant advantages in terms of high accuracy, high density, and a wide application range. These advantages greatly enhance the efficiency of surface wave exploration and the accuracy of profile imaging for the construction of engineering projects.

Excitation of Back‐Arc Tsunamis From Megathrust Ruptures: Theory and Application to the Sea of Japan

AbstractLarge megathrust ruptures can create notable tsunamis in tectonic back‐arc basins as was documented during the 2011 Tohoku earthquake in the Sea of Japan. We present a physical analysis of the excitation of back‐arc tsunamis by extending the fore‐arc deformation field from the earthquake centroid into the back‐arc basin and identify fault dip as the main geometrical contributor to the propagation of these events. As such, our theoretical model along with a large number of numerical simulations reveal that the dominant period of back‐arc tsunamis is different from that of the fore‐arc waves and thus they are a new class of tsunamis. Through numerical simulations and analysis of data from the 2011 Tohoku event, we show that a combination of near‐ to intermediate‐field horizontal and vertical deformation as well as transient surface waves is necessary to reconstruct the back‐arc propagation. We find that while seismic surface waves can affect coastal tsunami amplitudes in the back‐arc, their effect comes second to that of the horizontal component of deformation as manifested via bathymetric gradient. We then simulate back‐arc tsunamis and the hazard in the Sea of Japan from several potential future earthquake scenarios in the Japan Trench and Nankai Trough. Our results show that the coseismic excitation of back‐arc tsunamis can result in considerable waves close to 1 m in the Sea of Japan, near the Niigata Prefecture from megathrust earthquakes.

Integrated system of geophysical methods for shallow loose covering stratum exploration in the granite region in the northwest of Zhejiang Province, China

The major triggering factor of the collapses, landslides, and debris flow in the northwest region of Zhejiang Province in China is the shallow loose covering stratum with a thickness of dozens of centimeters to dozens of meters generated by the intensive physical weathering process of granite. Therefore, accessing a three-dimensional model of the slope structure covering by the shallow loose stratum and quantifying its thickness and spatial distribution are very important in deepening one’s understanding of the failure mechanism and distribution features and improving the efficiency of geohazard prevention and mitigation. This study applies high-density electrical method, microtremor survey, artificial transient surface wave method, and ground-penetrating radar to explore the slope structure covered by the loose stratum. By validating and comparing the results obtained through engineering geological drilling, an integrated system of the geophysical methods for the shallow loose covering stratum is proposed herein with greater precision and suitability for the granite region in the northwest of Zhejiang Province. This integrated system of methods consists of geophysical exploration, followed by drilling for validation. Each individual method in the system can be applied with suitability evaluation and recommended parameters. The proposed system could also properly void shortage when only an individual method is used. The major conclusions obtained in this study are as follows: (1) the accuracy of the high-density electrical method in the dry condition could reach 85% or above, and in the rainy season, the test should be conducted 48 h after the rainfall; (2) the microtremor survey and artificial transient surface wave methods can achieve good results in the case of a complex climate condition or a large-area detection; (3) the ground-penetrating radar method can be used to discover the loose covering layer thickness with good precision (less than 5 m); and (4) the integrated method system is more applicable when the ground slope is less than 30°.

Detection of anti-seepage effect of building stress wall structure based on transient Rayleigh surface wave method

Aiming at the problem that the traditional core drilling detection method has certain damage to the impervious body, and the detection points are limited, which leads to the limitation of the evaluation results; this paper proposes a detection method of seepage control effect of building stress wall structure based on transient Rayleigh surface wave method. The wave velocity of Rayleigh wave under plane stress is obtained by combining wave equation with plane stress. Under the three boundary conditions, it is theoretically feasible to detect the cutoff wall with transient Rayleigh surface wave technique. Therefore, based on the transient Rayleigh surface wave theory, the 24 channel broadband signal input channel and the minisis24 integrated engineering detector with advanced computer are used as the carrier to detect the anti-seepage effect of the stress wall structure. The practical engineering test shows that the permeability coefficient of the wall measured by this method is in good agreement with the core drilling method, and it is a reliable non-destructive testing method for wall anti-seepage.

An ISPH with k–ε closure for simulating turbulence under solitary waves

In this paper an Incompressible Smoothed Particle Hydrodynamics (ISPH) method solving the 2D RANS (Reynolds Averaged Navier-Stokes) equations with the k–ε turbulence closure is constructed. In the present model, the concept of “massless ISPH” utilizing the definition of “particle density” (number of computational particles within unit volume) is stressed. The skills of this numerical model are tested by applying to two laboratory experiments: (1) A non-breaking solitary wave propagating over a bottom-mounted barrier and (2) a solitary wave breaking on a 1 on 50 slope. In the former case flow separation occurs behind the barrier as the wave crest passes by and a vortex is generated, which later interacts with free surface causing breaking. In the latter case wave breaking and bottom friction both generate significant turbulence. For both cases, the effects of initial seeding of turbulent kinetic energy, required in the k–ε model, are studied and it is concluded that initial values of O (10−10) to O (10−8) m2/s2 should be used. An adaptive wall boundary condition for k–ε turbulence model is employed to avoid the unrealistic production of turbulence near the wall boundary. The numerical results, in terms of free surface profile, mean velocity field, vorticity field, turbulent kinetic energy and turbulent shear stress, are compared with experimental data. Very reasonable agreement is observed. This paper presents the first comprehensively validated 2D ISPH model with the k–ε turbulence closure, which can be applied to transient free surface wave problems.

Stormquakes: Tracing the path of ocean storms through the solid earth

We have discovered a new geophysical phenomenon involving the coupling of the atmosphere-ocean and solid Earth using a novel array method. An analysis of ten years of seismic data recorded in the continental United States, mainly at the USArray, shows that large storms such as hurricanes and Nor’easters can excite transient seismic surface waves in the 20–50 s band with amplitudes equivalent to those excited by M3.5 earthquakes. These sources, which we label stormquakes, can produce transcontinental coherent Rayleigh wave packets observable in the time domain and are thus fundamentally different from previously reported atmosphere-ocean solid Earth couplings that produce incoherent seismic noise. We present unique observations and methods to pinpoint the source locations and timing, which clearly shows that these seismic waves are from interactions of seafloor bathymetry and ocean waves that are energized by large storms. Stormquakes migrate along continental shelfbreak, tracking the leading edge of large storms. We have documented features and identified a possible physical mechanism explaining the stormquake excitation. Stormquakes have potential use in oceanography and meteorology as a remote monitoring tool with high spatial and temporal resolution with which to investigate ocean wave dynamics during large storms.

Filed test on 25,000 kN•m ultra high energy level dynamic consolidation on large thickness gravel foundation

A new airport is under construction at somewhere in northern China. The airport is located on an artificial island which is filled with gravel. Because the foundation is filled at one time and the thickness exceeds 22m, it should be consolidated. The designer supposed to use dynamic compaction method. The dynamic compaction energy may exceeds 15,000kN•m which is called ultra high energy level dynamic consolidation. However, the research of ultra high energy level dynamic consolidation and engineering examples available for reference are very few. Therefore, field test is necessary before formal construction to determine the reinforcement energy level and reinforcement effect. A series of dynamic compaction field tests with different energy levels were carried out. In this paper, dynamic compaction field tests of 25,000kN•m were introduced. In the test, flat load test was carried out to determine the bearing capacity of reinforced foundation, and deep settlement monitoring, layered settlement monitoring, ultra-heavy dynamic penetration test and multi-channel transient surface wave test were carried out before and after the consolidation to reflect the dynamic compaction reinforcement effect. The field test result shows that after dynamic consolidation of 25,000kN•m, the characteristic value of foundation bearing capacity is much larger than 150kpa, which meets the design requirements. Deep settlement monitoring, layered settlement monitoring, ultra-heavy dynamic penetration test and multi-channel transient surface wave test all can reflect the dynamic compaction reinforcement effect, and the monitoring results are very similar. After dynamic consolidation of 25,000kN•m, the reinforcement effect is not obvious in the range of 4m on the surface layer of the foundation, but obvious in the range of 4m to 16m, and still exists at 22m depth.

Construction summary of karst grouting treatment for Railway Subgrade

The karst is one of the main bad geological problems, which determines the design of the subgrade treatment plan and the safety of the engineering construction.This paper summarizes the key technology of grouting in karst roadbed regulation, and the following factors should be considered in grouting scheme selection: grouting method, technology, material, equipment, grouting control and detection means and standard of grouting effect.Through the use of high density electrical method, transient surface wave method, core drilling method, pressure water test method and so on, study the targeted detection methods for different coverage karst types and different remediation methods.

Construction summary of karst grouting treatment for Railway Subgrade

The karst is one of the main bad geological problems, which determines the design of the subgrade treatment plan and the safety of the engineering construction.This paper summarizes the key technology of grouting in karst roadbed regulation, and the following factors should be considered in grouting scheme selection: grouting method, technology, material, equipment, grouting control and detection means and standard of grouting effect.Through the use of high density electrical method, transient surface wave method, core drilling method, pressure water test method and so on, study the targeted detection methods for different coverage karst types and different remediation methods.

Analysis of the transient surface wave propagation in soft-solid elastic plates.

In dynamic elastography, the goal is to estimate the Young's modulus from audio-frequency wave propagation in soft-tissues. Within this frequency range, the shear wavelength is centimeter-sized while the compressional wavelength is meter-sized. Thus, the experimental data are usually collected in the near-field of the source. Near-field effects have been widely studied for bulk wave propagation. However, the near- and transient-fields of surface and guided waves have received less attention. In this work, the transient surface displacement field in soft-solid elastic plates in vacuum is analyzed. Due to the high Poisson's ratio, mode conversion has special characteristics in soft-solids. They are analyzed through this work where it is shown that the transient-field over the surface can be interpreted by tracing a few reflections. The authors show the existence of a critical distance needed for the formation of Rayleigh-Lamb modes. Below this distance, only direct surface waves propagate without contribution from reflected waves. Thus, the dispersion curve differs from that predicted by Rayleigh-Lamb modes. Instead, the authors propose a model based on the interference of surface waves, which agree with the experimental data. In addition, the conditions needed in order to retrieve the shear wave phase velocity from the surface field are given.

Research on Detection Standard of Karst Roadbed Grouting Effect Based on the Geophysical Methods

To study the grouting detection standard of Karst roadbed based on resistivity method, transient Surface wave method and electromagnetic wave CT, the typical test areas in the Karst roadbed of NANNING-GUANGZHOU railway are selected, and the field test research of grouting detection standard of Karst roadbed was studied by the above three geophysical methods. The grouting qualified Karst roadbed was determined by multiple methods of borehole coring and field water pressure after grouting, and the test results of Karst roadbed grouting qualified was confirmed effective sample. The difference value of resistivity, surface wave velocity and electromagnetic wave absorption coefficient of limestone layer, clay, pebble soil and Karst cave was statistical analyzed based on the effective test data, and preliminarily obtained the detection standard of Karst roadbed grouting effect based on the above three geophysical methods.

On effective characteristic of Rayleigh surface wave propagation in porous fluid-saturated media at low frequencies

The analytical dispersion and waveform solutions of Rayleigh surface wave for the Biot fluid-saturated model are obtained at low frequencies for a homogeneous half space. The equivalent solution is also obtained by the equivalent-viscoelastic representation of the fluid-saturated model based on a single viscoelastic element for each wave modulus. The effective characteristics of the validations and limitations for the equivalent-viscoelastic model are analyzed by comparison of the numerical solutions of the fluid-saturated model and the equivalent model for the surface wave propagations. Our calculations show that the free boundary effects on the frequency dependent dispersion and time dependent dynamical waveforms of the surface wave in the Biot model are well fitted in a relative narrow low frequency band by the Zener elements in case of the frequency is much lower than the critical frequency fc of the porous material. The effective characteristics for air filled cases with a higher fc show a better result. Furthermore, if the critical frequency fc is low, always with high permeability κ under near surface condition, at low frequencies (e.g. the seismic frequency band <200Hz) the surface fluid drainage conditions influence Rayleigh-wave propagations obviously. The frequency range must hence be carefully checked for the viscoelastic representations. When the validated frequency range is defined, the viscoelastic elements can solve the transient surface wave propagation in porous media effectively. The convolution integral in wave modeling can be replaced by memory variables, which makes the field quantities calculated at every time step need not be stored. The effective representation saves the consumptions of computer time and storages, and supplies a more convenient approach to apply the surface wave considering poroelasticity.

A focused air-pulse system for optical-coherence-tomography-based measurements of tissue elasticity

Accurate non-invasive assessment of tissue elasticity in vivo is required for early diagnostics of many tissue abnormalities. We have developed a focused air-pulse system that produces a low-pressure and short-duration air stream, which can be used to excite transient surface waves (SWs) in soft tissues. System characteristics were studied using a high-resolution analog pressure transducer to describe the excitation pressure. Results indicate that the excitation pressure provided by the air-pulse system can be easily controlled by the air source pressure, the angle of delivery, and the distance between the tissue surface and the port of the air-pulse system. Furthermore, we integrated this focused air-pulse system with phase-sensitive optical coherence tomography (PhS-OCT) to make non-contact measurements of tissue elasticity. The PhS-OCT system is used to assess the group velocity of SW propagation, which can be used to determine Young’s modulus. Pilot experiments were performed on gelatin phantoms with different concentrations (10%, 12% and 14% w/w). The results demonstrate the feasibility of using this focused air-pulse system combined with PhS-OCT to estimate tissue elasticity. This easily controlled non-contact technique is potentially useful to study the biomechanical properties of ocular and other tissues in vivo.

The 2012 Mw 8.6 Sumatra earthquake: Evidence of westward sequential seismic ruptures associated to the reactivation of a N‐S ocean fabric

The 11 April 2012 Mw 8.6 earthquake offshore Sumatra is the largest of the rare great intraplate earthquakes of the instrumental era. This major strike‐slip event occurred in the diffuse zone of deformation that accommodates differential rotation between Indian and Australian plates. We perform a back projection analysis – calibrated with well‐located aftershocks – of short‐period teleseismic P‐waves recorded by the European array to image the rupture process during the mainshock. In complement, a Love wave analysis is conducted for tracking azimuthal change in the apparent global source duration due to the source spatio‐temporal extent. The combined analysis reveals a complex rupture pattern, characterized by three main episodes of energy release, the latest being located 370 km west of the epicenter, on the Ninety East Ridge, with a delay of 120 s. We interpret the 11 April 2012 Mw 8.6 offshore Sumatra earthquake as a complex westward‐propagating sequence of dynamically triggered strike‐slip fault ruptures, associated to the reactivation of the inherited NNE–striking sea floor fabric. The dynamic triggering mechanism could result from the interaction between transient surface wave stress perturbations and fluids.

Application of the Comprehensive Geophysical Prospecting Techniques in Hidden Trouble Detection of Tailings Dam

Geophysical detecting methods are used widely in hidden trouble exploration of embankments and dams because of their portability and efficiency. The high-density resistivity method and the transient state surface wave method are used to investigate the mine tailings dam, combining the hidden trouble characteristic and feature of the mine tailings dam, the distribution range, the defect feature and the density of the dam material are found out by using the comprehensive methods. The techniques would be offering reference for controlling mine tailings dam seepage and stability and safety evaluation.

Transient space-time surface waves characterization using Gabor analysis

Laser ultrasonics allow the observation of transient surface waves along their propagation media and their interaction with encountered objects like cracks, holes, borders. In order to characterize and localize these transient aspects in the Space-Time-Wave number-Frequency domains, the 1D, 2D and 3D Gabor transforms are presented. The Gabor transform enables the identification of several properties of the local wavefronts such as their shape, wavelength, frequency, attenuation, group velocity and the full conversion sequence along propagation. The ability of local properties identification by Gabor transform is illustrated by two experimental studies: Lamb waves generated by an annular source on a circular quartz and Lamb wave interaction with a fluid droplet. In both cases, results obtained with Gabor transform enable ones to identify the observed local waves.

Acoustic emission from a surface-breaking crack under cyclic loading

An isotropic, homogeneous, elastic half-space is subjected to a uniform stress system composed of a constant tensile stress with a superimposed cyclic tensile stress, both parallel to the free surface. The cyclic stresses are assumed to generate a surface-breaking crack of length l(t) which propagates normal to the surface. The unloading of the crack faces generates acoustic emission, which is primarily composed of surface waves. The elastodynamic reciprocity theorem for time-harmonic waves is used to determine the radiated system of transient and steady state surface waves.

Transient behavior of surface plasmon polaritons scattered at a subwavelength groove

We present a numerical study and analytical model of the optical near field diffracted in the vicinity of subwavelength grooves milled in silver surfaces. The Green's tensor approach permits the computation of the phase and amplitude dependence of the diffracted wave as a function of the groove geometry. It is shown that the field diffracted along the interface by the groove is equivalent to replacing the groove by an oscillating dipolar line source. An analytic expression is derived from the Green's function formalism, which reproduces well the asymptotic surface plasmon polariton (SPP) wave as well as the transient surface wave in the near zone close to the groove. The agreement between this model and the full simulation is very good, showing that the transient ``near-zone'' regime does not depend on the precise shape of the groove. Finally, it is shown that a composite diffractive evanescent wave model that includes the asymptotic SPP can describe the wavelength evolution in this transient near zone. Such a semianalytical model may be useful for the design and optimization of more elaborate photonic circuits, whose behavior in a large part will be controlled by surface waves.

Application of the reciprocity theorem to determine line-load-generated surface waves on an inhomogeneous transversely isotropic half-space

Free and forced time-harmonic surface waves are investigated for a half-space of transversely isotropic elastic material, where the axis normal to the free surface (the z-axis) is the axis of symmetry. In addition, the elastic constants and the mass density depend on the distance from the free surface. A surface wave is considered as being composed of a carrier wave that propagates over the free surface as it would over a membrane, while it carries along a system of depth-dependent motions. For free surface waves the analytical details, i.e., the calculation of the wave speed of the free surface waves, are worked out for the case that the elastic constants and the mass density vary exponentially with depth. For forced motion by a time-harmonic line load, the far-field surface wave motion is determined by an application of the reciprocity theorem for elastodynamics. Numerical results for displacements and stresses are graphically displayed. Fourier superposition has been used to determine the transient surface wave response to a pulse-type normal line-load.