Automatic and efficient ground penetrating radar (GPR) data analysis remains a bottleneck, especially restricting applications in real-time monitoring systems. Deep learning approaches have good ...practice in automatic object identification, but their intensive data requirement has reduced their applicability. This paper developed a machine learning framework based on wavelet scattering networks to analyze GPR data for subsurface pipeline identification. Wavelet scattering network is functionally equivalent to convolutional neural networks, and its null-parameter property is intended for non-intensive datasets. A double-channel framework is designed with wavelet scattering networks followed by support vector machines to determine the existence of pipelines on vertical and horizontal traces separately. Classification accuracy rates arrive around 98% and 95% for datasets without and with noises, respectively, as well as 97% for considering surface roughness. Pipeline locations and diameters are convenient to determine from the reconstructed profiles of both simulated and practical GPR signals. However, the results of 5 cm pipelines are sensitive to noises. Nonetheless, the developed machine learning approach presents promising applicability in subsurface pipeline identification.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
► Cavitating flow around a twisted hydrofoil is studied by PANS method. ► Evolution of cavitation patterns are well predicted compared to experiments. ► The reasons for the primary and secondary ...shedding are discussed. ► The mechanism of cavitating horse-shoe vortex production is illustrated.
Cavitating turbulent flow around hydrofoils was simulated using the Partially-Averaged Navier–Stokes (PANS) method and a mass transfer cavitation model with the maximum density ratio (ρl/ρv,clip) effect between the liquid and the vapor. The predicted cavity length and thickness of stable cavities as well as the pressure distribution along the suction surface of a NACA66(MOD) hydrofoil compare well with experimental data when using the actual maximum density ratio (ρl/ρv,clip=43391) at room temperature. The unsteady cavitation patterns and their evolution around a Delft twisted hydrofoil were then simulated. The numerical results indicate that the cavity volume fluctuates dramatically as the cavitating flow develops with cavity growth, destabilization, and collapse. The predicted three dimensional cavity structures due to the variation of attack angle in the span-wise direction and the shedding cycle as well as its frequency agree fairly well with experimental observations. The distinct side-lobes of the attached cavity and the shedding U-shaped horse-shoe vortex are well captured. Furthermore, it is shown that the shedding horse-shoe vortex includes a primary U-shaped vapor cloud and two secondary U-shaped vapor clouds originating from the primary shedding at the cavity center and the secondary shedding at both cavity sides. The primary shedding is related to the collision of a radially-diverging re-entrant jet and the attached cavity surface, while the secondary shedding is due to the collision of side-entrant jets and the radially-diverging re-entrant jet. The local flow fields show that the interaction between the circulating flow and the shedding vapor cloud may be the main mechanism producing the cavitating horse-shoe vortex. Two side views described by iso-surfaces of the vapor volume fraction for a 10% vapor volume, and a non-dimensional Q-criterion equal to 200 are used to illustrate the formation, roll-up and transport of the shedding horse-shoe vortex. The predicted height of the shedding horse-shoe vortex increases as the vortex moves downstream. It is shown that the shape of the horse-shoe vortex for the non-dimensional Q-criterion is more complicated than that of the 10% vapor fraction iso-surface and is more consistent with the experiments. Further, though the time-averaged lift coefficient predicted by the PANS calculation is about 12% lower than the experimental value, it is better than other predictions based on RANS solvers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
•Amplitude gain function aims to handle attenuation of electromagnetic wave signals.•Elimination methods aims to handle superimposed reflected waves.•Two test scenario and a real field measurement ...were investigated.•Proposed method can identify the underground abnormal rock masses effectively.
Surrounding rock quality of underground caverns, which determines the safety and stability, is of great importance in geological engineering. Ground penetrating radar (GPR) has potential to accurately image the subterranean profile. Against two major issues that affect GPR detection, a new method to process GPR data for abnormal underground rocks identification was investigated. An improved amplitude gain function and an elimination method were proposed, which can amplify weak signals and separate true signals from superimposed waveforms, and it was further developed into real-time algorithm. In field measurements, after processing the GPR data of two pre-buried pipelines, the imaging profile can accurately present their locations. Surrounding rock quality of a subterranean cavern was detected by GPR, and the elimination results can clearly show the multi-joint areas. The real-time algorithm has capacity to discover abnormal places during the survey instead of afterwards, which can improve the engineer efficiency.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The quality of the surrounding rock is crucial to the stability of underground caverns, thereby requiring an effective monitoring technology. Ground-penetrating radar (GPR) can reconstruct the ...subterranean profile by electromagnetic waves, but two significant issues, called clutter and hyperbola tails, affect the signal quality. We propose an approach to identify fractured rocks using 2D Wavelet transform (WT) and F-K migration. F-K migration can handle the hyperbola using Fourier analysis. WT can mitigate clutter, distinguish signal discontinuity, and provide signals with a good time-frequency resolution for F-K migration. In the simulation, the migration result from horizontal detail coefficients highlight the crack locations and reduce the scattering signals. Noise has been separated by 2D WT. Hyperbola tails are decomposed to vertical and diagonal detail coefficients. Similar promising results have been achieved in the field measurement. Therefore, the proposed approach can process GPR signals for identifying fractured rock areas.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Surrounding rock quality of underground caverns is crucial to structural safety and stability in geological engineering. Classic measures for rock quality investigation are destructive and time ...consuming, and therefore technology evolution for efficiently evaluating rock quality is significantly required. In this paper, the non-destructive technology ground penetrating radar (GPR) assisted by an ensemble empirical mode decomposition (EEMD)-based signal processing approach is investigated for identifying unstable subsurface rock structures. By decomposing the pre-processed GPR signals into multiple intrinsic mode functions (IMFs) and residues, one typical IMF can preserve the distinct local modes and is considered to reconstruct the subterranean profile. Promising results have been achieved in simple scenarios and filed measurements. The reconstructed profiles can accurately illustrate the subsurface interfaces and eliminate the interference signals. Unstable rock structures have been identified in further field applications. Therefore, the developed approach is efficient in unstable rock structure identification.
High-power laser has been considered as a potential method of rock breakage through melting. However, high energy consumption and low efficiency are the main restrictions for applying laser ...technology in rock excavation and fragmentation. A new rock breakage method which combines pulsed laser and induced cavitation is described in this paper, with potentially low energy consumption and high efficiency in rock fracturing. Cavitation is the rapid formation and collapse of vapour bubbles within a liquid. The irradiation of a pulsed laser beam with the energy density beyond the breakdown threshold of a liquid could induce cavitation bubbles in the liquid. The energy of the laser beam converts into highly pressurised cavitation bubbles. When the cavitation bubbles explode near rock surface, the explosions induce dynamic force to break the rock. In this paper, a series of tests using continuous and pulsed laser beams to break rocks in both air and water are presented. It is found that the pulsed laser in water produced the best rock-breaking efficiency without melting the rocks. Further analysis of the crater morphology and mechanical properties suggests the dynamic force at cavitation bubble explosion is the main cause of rock fracturing. The study leads to the conclusion that the pulsed laser induced cavitation in water is potentially an effective way for laser rock cutting technology with industrial applications.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The spoil area for wastes of underground engineering is featured with large scale, loose accumulations, high and steep slopes, and no roads. Traditional contact monitoring methods are difficult to ...operate, and representative points are difficult to choose to characterize the overall deformation of the slope. In this case, this paper attempts to apply the GB-InSAR system to carry out on-site monitoring and experimental research based on China's first large-scale groundwater storage and storage waste rock yard. The research results show that: (1) GB-InSAR full-field scanning can effectively solve the problem in selecting representative points on the side slope surface to present the overall deformation of the slope; (2) 4 different modes of the slope's -0.5mm equal displacement cross-sectional area are shown over time; (3) The final maximum landslide area of type B1 are 0.56 times at most of the cross-sectional area of -0.5mm equal displacement before the landslide, and type B2 are at most 0.96 times.
SUMMARY
This paper presents a systematic and efficient method, namely the generalized transfer matrix method, for evaluating the dispersion curves and eigenfunctions of surface waves in multilayered ...azimuthally anisotropic half‐space. Apart from avoiding the well‐known numerical difficulties associated with the existing Thomson–Haskell method, the generalized transfer matrix method possesses the robust determination of independent polarization vectors by using the singular value decomposition (SVD) approach, the explicit inversion of the 6 × 6 eigencolumn matrix without any resort to numerical inversion and the efficient computation of eigenfunctions for layered azimuthally anisotropic media. By means of straightforward transformations, the generalized transfer matrix method leads to a twofold recursive algorithm: (1) for the recursive computation of phase velocities it starts from the bottom half‐space to the top layer and (2) for the recursive solution of eigenfunctions it starts from the top layer to the bottom half‐space. While keeping the simplicity of the Thomson–Haskell transfer matrix method, the generalized transfer matrix method is of unconditional stability and computational efficiency. The related numerical examples demonstrate that the generalized transfer matrix method is a powerful and robust tool for simulating the propagation of elastic surface waves in the layered azimuthally anisotropic half‐space.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
•Modified sulfoaluminate grouting material is developed for water-sealed underground caverns.•Its property transformation under pressure circulation is found and studied.•Its effectiveness and ...practicability are verified in grouting of underground caverns.
Water-sealed underground oil caverns are quite different from conventional underground projects because of the harsher conditions. For one of the largest such caverns in China, conventional grouting materials could not meet the project standard. Therefore, the authors invented a new grouting material based on sulfoaluminate cement (SAC) and studied its properties under pressure circulation. During circulation, the time to the hydration exothermic peak time was reduced, and the peak temperature increased with the pressure. The compressive strength decreased during circulation and with the circulation time. These results were important for grouting during the project.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
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