scholarly journals Influence of Soil Parameters on Detecting Voids behind a Tunnel Lining Using an Impact Echo Method

2019 ◽  
Vol 9 (24) ◽  
pp. 5403
Author(s):  
Meng Ma ◽  
Rongning Cao ◽  
Chao Niu ◽  
Hougui Zhang ◽  
Weining Liu
Keyword(s):  
Element Model ◽  
Tunnel Lining ◽  
Parameter Analysis ◽  
Soil Parameters ◽  
Impact Echo ◽  
Time Frequency ◽  
Box Counting ◽  
Box Counting Dimension ◽  
Frequency Domains ◽  
The Impact

Tunnel lining cavities are a common problem that may affect the bearing capacity of the tunnel-supporting structure, as well as the tunnel service life. The impact echo (IE) method can be used to detect voids behind tunnel linings. For a long tunnel, the surrounding rocks/soils are inhomogeneous and anisotropic, with parameters that vary with tunnel mileages. It is interesting to analyse whether alterations of the soil parameters affect the non-destructive test results. A laboratory experiment was performed in this study, in which voids behind a concrete plate, representing the tunnel lining, were designed to model the ineffective contact between the soil and the tunnel. The IE method was employed to inspect the existence of the void using different signal analysis approaches in the time, frequency and time–frequency domains. Furthermore, the fractal box-counting dimension was calculated for the purpose of quantitative evaluation. Different soil parameters and void sizes were considered, and finally, a finite element model was built and parameter analysis was accomplished using the software ABAQUS. The results demonstrated that: (1) A comprehensive analysis of vibration signals in the time, frequency and time–frequency domains was useful for identifying voids, while the box-counting dimension was useful for evaluating voids quantitatively. (2) Soils with large density and Young’s modulus differences had a certain influence on void detection, while those with large water content and Poisson’s ratio differences had little influence. (3) The box-counting dimension value was stable within the area where the void existed behind the tunnel; when the detection point was beyond twice that of the void dimension, it was difficult to locate the void.

scholarly journals Detecting the Void behind the Tunnel Lining by Impact-Echo Methods with Different Signal Analysis Approaches

2019 ◽  
Vol 9 (16) ◽  
pp. 3280 ◽  
Author(s):  
Rongning Cao ◽  
Meng Ma ◽  
Ruihua Liang ◽  
Chao Niu
Keyword(s):  
Frequency Domain ◽  
Signal Analysis ◽  
Dynamic Stiffness ◽  
Tunnel Lining ◽  
Impact Echo ◽  
Time Frequency ◽  
Void Detection ◽  
Wavelet Transform Analysis ◽  
The Time Domain ◽  
The Impact

A void behind the lining in a tunnel is considered to be a critical condition as it can significantly impair the tunnel service life. In this study, we adopted the impact-echo (IE) method to detect the voids. We designed two test conditions (tunnel lining with and without a void) for our experiments performed in a laboratory environment. The influences of void size and impact-void position were analysed using numerical simulations. The vibration response signals were analysed in the time, frequency, and time–frequency domains using various signal analysis approaches. The results were comparatively analysed to determine the best approach for void detection. The study helped establish that a tunnel void can be evaluated through the vibration energy (amplitude and duration) in the time domain, the resonance frequency and dynamic stiffness in the frequency domain, and the energy distribution in time–frequency domain. The wavelet transform analysis is the most appropriate method to observe the energy flow during the state changing and the dynamic stiffness method can determine the void position precisely.

scholarly journals An impact echo method to detect cavities between railway track slabs and soil foundation

2021 ◽  
Vol 68 (1) ◽  
Author(s):  
Pierre Anthyme Bahati ◽  
Viet Dinh Le ◽  
Yujin Lim
Keyword(s):  
Open Space ◽  
Concrete Slab ◽  
Test Methods ◽  
Railway Track ◽  
Element Analysis ◽  
Impact Echo ◽  
Time Frequency ◽  
Railway Tracks ◽  
Soil Foundation ◽  
The Impact

AbstractThe impact echo technique is one of the most useful non-destructive test methods for determining the thickness of concrete or detecting possible cracks or cavities in the internal parts of a concrete structure without damaging the surface. Many types of unstable conditions in railway tracks, including various modes of irregularities, may occur when cavities are generated directly under a concrete slab track or when a slight open space is made under a loose sleeper. In this study, we developed a nondestructive testing (NDT) system for detecting abnormalities in concrete tracks and performed 3D numerical simulations using the ABAQUS finite element analysis (FEA) program to investigate the impact echo response from a concrete track slab with different sizes of cavities. Sections of concrete slab were simulated as solid body masses under the railway tracks with gaps in the bodies themselves or with cavities existing between the track concrete layer (TCL) and the hydraulically stabilized base (HSB). We investigated the locations and depths of the cavities and gaps in the model concrete slab using the acoustic impact echo response based on the frequency response of the elastic waves generated in the slab. In addition, a Short-time Fourier Transform (STFT) and a wavelet technique were adopted for a time frequency analysis. Our study demonstrated that the impact echo technique developed in this study by FEA and NDT can measure and confirm the location and depth of cavities in concrete slabs.

scholarly journals Spillover effects from news to travel and leisure stocks during the COVID-19 pandemic: Evidence from the time and frequency domains

2021 ◽  
pp. 135481662110584
Author(s):  
Ying Wang ◽  
Hongwei Zhang ◽  
Wang Gao ◽  
Cai Yang
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Spillover Effects ◽  
Short Term ◽  
Time Frequency ◽  
Frequency Domains ◽  
Media Hype ◽  
The Time Domain ◽  
The Impact

The impact of the COVID-19 pandemic on tourism has received general attention in the literature, while the role of news during the pandemic has been ignored. Using a time-frequency connectedness approach, this paper focuses on the spillover effects of COVID-19-related news on the return and volatility of four regional travel and leisure (T&L) stocks. The results in the time domain reveal significant spillovers from news to T&L stocks. Specifically, in the return system, T&L stocks are mainly affected by media hype, while in the volatility system, they are mainly affected by panic sentiment. This paper also finds two risk contagion paths. The contagion index and Global T&L stock are the sources of these paths. The results in the frequency domain indicate that the shocks in the T&L industry are mainly driven by short-term fluctuations. The spillovers from news to T&L stocks and among these T&L stocks are stronger within 1 month.

Research of Pure Tone Detection for Faulted On-Vehicle Loudspeakers Based on Image Fractal

2014 ◽  
Vol 494-495 ◽  
pp. 171-174 ◽  
Author(s):  
Gui Ling Tan ◽  
Yu Ming Qi ◽  
San Peng Deng ◽  
De Hua Miao ◽  
Wen Hua Gao
Keyword(s):  
Pure Tone ◽  
Wavelet Packet ◽  
Detection Accuracy ◽  
Monitoring Method ◽  
Time Frequency ◽  
Two Dimensional Image ◽  
Box Counting ◽  
Fault Recognition ◽  
Box Counting Dimension ◽  
Tone Detection

At present, the detection accuracy of monitoring method by human ears is not satisfying in the pure tone detection of on-vehicle loudspeakers. To solve this problem, a new method is proposed to convert vehicle loudspeakers response signals into a two-dimensional image signal via wavelet packet analysis, which can increase the time-frequency of malfunction information. Through image binaryzation and pretreatment image-edge detection, the resulting signal would be recognized with box-counting dimension acquired in the process of gaining time-frequency image through fractal dimension as malfunctioned indications. Experiments show a rate of fault recognition as high as 95% , which meet the requirements of online vehicle loudspeaker detection.

scholarly journals Performance Evaluation of Epileptic Seizure Prediction Using Time, Frequency, and Time–Frequency Domain Measures

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 682
Author(s):  
Debiao Ma ◽  
Junteng Zheng ◽  
Lizhi Peng
Keyword(s):  
Epileptic Seizures ◽  
Forward Selection ◽  
Time Frequency ◽  
Frequency Domains ◽  
Minimal Redundancy ◽  
Detailed List ◽  
Complete Set ◽  
Maximal Relevance ◽  
Sequential Forward Selection ◽  
The Impact

The prediction of epileptic seizures is crucial to aid patients in gaining early warning and taking effective intervention. Several features have been explored to predict the onset via electroencephalography signals, which are typically non-stationary, dynamic, and varying from person-to-person. In the former literature, features applied in the classification have shared similar contributions to all patients. Therefore, in this paper, we analyze the impact of the specific combination of feature and channel from time, frequency, and time–frequency domains on prediction performance of disparate patients. Based on the minimal-redundancy-maximal-relevance criterion, the proposed framework uses a sequential forward selection approach to individually find the optimal features and channels. Trained models could discriminate the pre-ictal and inter-ictal electroencephalography with a sensitivity of 90.2% and a false prediction rate of 0.096/h. We also present the comparison between the classification accuracy obtained by the optimal features, several features summarized from optimal features, and the complete set of features from three domains. The results indicate that various patient interpretations have a certain specificity in the selection of feature-channel. Furthermore, the detailed list of optimal features and summarized features are proffered for reference to those who research the corresponding database.

Study on Simplification Conditions of Curved Regular Bridges under Seismic Effect

2014 ◽  
Vol 580-583 ◽  
pp. 1723-1728
Author(s):  
Tai Yu Song ◽  
Yin Shen ◽  
Guo Ping Li
Keyword(s):  
Seismic Response ◽  
Element Model ◽  
B Value ◽  
Seismic Effect ◽  
Parameter Analysis ◽  
Radius Of Curvature ◽  
R Value ◽  
The Difference ◽  
Girder Bridge ◽  
The Impact

A radius of curvature 20 times greater than the deck width of the bridge (R≥20b) is required as a specification in the regular bridge simplification conditions of the seismic response of curved girder bridges. Selecting benchmark bridges and employing parameter analysis method, this article studies on the effect of R/B value of the curved girder bridge on the response ratio of the seismic response calculated using the finite element model and that using a regular girder bridge. This study shows that on conditions that the deck width of the bridge is constant, the smaller the radius of curvature and the larger the B/R value (i.e., the smaller the R/B value) of the curved girder bridge are, the greater the difference between the seismic response of the curved girder bridge and the result calculated with a regular girder bridge is, and the difference is more significant under traverse seismic effect than that of longitudinal seismic effect. On conditions that the radius of curvature is constant, the impact of the change of B/R value due to the deck width change of the bridge on the difference between the seismic response of the curved girder bridge and the result calculated with a regular girder bridge is insignificant. Compared with the deck width of the bridge, the difference between the seismic response of the curved girder bridge and the result calculated with a regular girder bridge is more sensitive to the radius of curvature.

scholarly journals Ground vibrations and airborne sounds generated by motion of rock in a river bed

2008 ◽  
Vol 8 (5) ◽  
pp. 1139-1147 ◽  
Author(s):  
C.-J. Huang ◽  
C.-H. Yeh ◽  
C.-Y. Chen ◽  
S.-T. Chang
Keyword(s):  
Decay Rate ◽  
High Frequency ◽  
Debris Flows ◽  
Spatial Decay ◽  
High Frequency Band ◽  
Ground Vibrations ◽  
Time Frequency ◽  
River Bed ◽  
Frequency Domains ◽  
The Impact

Abstract. This study investigates how ground vibrations (underground sounds) and airborne sounds that are produced by rocks in a river bed differ from each other. Airborne and underground sounds were simultaneously received at three microphones and three geophones, respectively. These sound signals were then analyzed using both the Fast Fourier Transform and the Gabor Transform to represent them in both the frequency and time-frequency domains. Experimental data indicate that the frequency of both airborne and underground sounds produced by the impact of rocks against the river bed is in the range 10–150 Hz. Furthermore, the high-frequency band of underground sounds decays much more rapidly than that of airborne sounds. The spatial decay rate of airborne sounds was also determined and compared with theoretical values. The lower spatial decay rate of airborne sounds than that of underground sounds suggests that monitoring of airborne sounds may be more efficient in the detection of debris flows or other natural hazards that generate both airborne and underground sounds.

scholarly journals Deep Neural Network and Polynomial Chaos Expansion-Based Surrogate Models for Sensitivity and Uncertainty Propagation: An Application to a Rockfill Dam

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1830
Author(s):  
Gullnaz Shahzadi ◽  
Azzeddine Soulaïmani
Keyword(s):  
Polynomial Chaos ◽  
Complex Structure ◽  
Uncertainty Propagation ◽  
Surrogate Models ◽  
Polynomial Chaos Expansion ◽  
Soil Parameters ◽  
Chaos Expansion ◽  
Rockfill Dam ◽  
Parametric Studies ◽  
The Impact

Computational modeling plays a significant role in the design of rockfill dams. Various constitutive soil parameters are used to design such models, which often involve high uncertainties due to the complex structure of rockfill dams comprising various zones of different soil parameters. This study performs an uncertainty analysis and a global sensitivity analysis to assess the effect of constitutive soil parameters on the behavior of a rockfill dam. A Finite Element code (Plaxis) is utilized for the structure analysis. A database of the computed displacements at inclinometers installed in the dam is generated and compared to in situ measurements. Surrogate models are significant tools for approximating the relationship between input soil parameters and displacements and thereby reducing the computational costs of parametric studies. Polynomial chaos expansion and deep neural networks are used to build surrogate models to compute the Sobol indices required to identify the impact of soil parameters on dam behavior.

An improved method to estimate Q based on the logarithmic spectrum of moving peak points

2019 ◽  
Vol 7 (2) ◽  
pp. T255-T263 ◽  
Author(s):  
Yanli Liu ◽  
Zhenchun Li ◽  
Guoquan Yang ◽  
Qiang Liu
Keyword(s):  
Seismic Waves ◽  
Wave Attenuation ◽  
Real Data ◽  
Peak Frequency ◽  
Seismic Reflection Data ◽  
The Real ◽  
Time Frequency ◽  
Reflection Data ◽  
Text Filtering ◽  
The Impact

The quality factor ([Formula: see text]) is an important parameter for measuring the attenuation of seismic waves. Reliable [Formula: see text] estimation and stable inverse [Formula: see text] filtering are expected to improve the resolution of seismic data and deep-layer energy. Many methods of estimating [Formula: see text] are based on an individual wavelet. However, it is difficult to extract the individual wavelet precisely from seismic reflection data. To avoid this problem, we have developed a method of directly estimating [Formula: see text] from reflection data. The core of the methodology is selecting the peak-frequency points to linear fit their logarithmic spectrum and time-frequency product. Then, we calculated [Formula: see text] according to the relationship between [Formula: see text] and the optimized slope. First, to get the peak frequency points at different times, we use the generalized S transform to produce the 2D high-precision time-frequency spectrum. According to the seismic wave attenuation mechanism, the logarithmic spectrum attenuates linearly with the product of frequency and time. Thus, the second step of the method is transforming a 2D spectrum into 1D by variable substitution. In the process of transformation, we only selected the peak frequency points to participate in the fitting process, which can reduce the impact of the interference on the spectrum. Third, we obtain the optimized slope by least-squares fitting. To demonstrate the reliability of our method, we applied it to a constant [Formula: see text] model and the real data of a work area. For the real data, we calculated the [Formula: see text] curve of the seismic trace near a well and we get the high-resolution section by using stable inverse [Formula: see text] filtering. The model and real data indicate that our method is effective and reliable for estimating the [Formula: see text] value.

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