Karst caves are among the most common and critical geological hazards in karst regions.Due to their marked differences in physical properties compared to the surrounding rock,they can be detected using various geophys...Karst caves are among the most common and critical geological hazards in karst regions.Due to their marked differences in physical properties compared to the surrounding rock,they can be detected using various geophysical techniques.Karsts have developed on the surface of the Qingshuitang Wollastonite Mining Area in Huangtian Town,Hezhou City,Guangxi Province.In line with mine safety production requirements,a professional assessment of the potential development of karst caves must be conducted within 150 m of the mining area’s surface.Following an on-site investiga-tion and comparison with traditional geophysical methods,seismic frequency resonance technology(Seismic FRT)was selected for detection due to its convenience,flexibility,cost-effectiveness,and rapid data acquisition capabilities.Contour maps of the apparent wave impedance and geological profiles along the survey lines were obtained through data collection and processing.In combination with surface karst and mining geology,32 karst caves(hidden danger points)and 15 karst development zones were identified.Drilling verification was conducted at the A428 and B122 anomalous points on the A1# and B1# survey lines.The verification results were consistent with the inferred depths and maximum apparent wave impedance anomalies,confirming that Seismic FRT is a feasible and effective method for detecting hid-den karst development areas in mines.展开更多
An experimental study is presented on the non-Gaussian statistics of random unidirectional laboratory wave fields described by JONSWAP spectra.Relationships between statistical parameters indicative of the occurrence ...An experimental study is presented on the non-Gaussian statistics of random unidirectional laboratory wave fields described by JONSWAP spectra.Relationships between statistical parameters indicative of the occurrence of largeamplitude waves are discussed in the context of the initial steepness of the waves combined with the effect of spectral peakedness.The spatial evolution of the relevant statistical and spectral parameters and features is also considered.It is demonstrated that over the distance the spectra exhibit features typical for developing nonlinear instabilities,such as spectral broadening and downshift of the peak,along with lowering of the high-frequency tail and decrease of the peak magnitude.The wave fields clearly show an increase of third-order nonlinearity with the distance,which can be significant,depending on the input wave environment.The steeper initial conditions,however,while favouring the occurrence of extremely large waves,also increase the chances of wave breaking and loss of energy due to dissipation,which results in lower extreme crests and wave heights.The applied Miche-Stokes-type criteria do confirm that some of the wave extremes exceed the limiting individual steepness.Eventually,this result agrees with the observation that the largest number of abnormal waves is recorded in sea states with moderate steepness.展开更多
Detecting stress concentration, especially critical stress state leading to structure damage or failure, is one of the most important tasks of equipment diagnosis. Metal magnetic memory technique needs further researc...Detecting stress concentration, especially critical stress state leading to structure damage or failure, is one of the most important tasks of equipment diagnosis. Metal magnetic memory technique needs further research to evaluate stress concentration quantitatively due to ambiguous physical mechanism, though it has potential to detect early defects in ferromagnetic materials. Mild Q235 steel defective specimens in demagnetization state were loaded in tension up to visible necking, with magnetic memory signals measurement made at increasing stress levels. Magnetic signals varied greatly under first several loadings and subsequently tended to stability in the elastic region, which showed that the magnetization always approaches the anhysteretic magnetization curve and was explained by the theory of magnetomechanical effect. In the plastic stage, an abnormal wave occurred in the stress concentration zone and its height value was sensitive to plastic deformation levels and dependent on the distance between the probe and defect, in accordance with the simulation results based on the magnetic dipole model. Different magnetic signal characteristics in the elastic-plastic region indicate that the magnetic memory technique can identify macroyielding and early damage, which is of profound significance for ensuring safe operation of equipment in service.展开更多
基金supported by the General Project of Guangxi Natural Science Foundation grant number[2020GXNSFAA297088]the Hezhou Science Research and Development Plan Project grant number[2024143]the Basic Research Ability Enhancement Project for Young and Middle-aged Teachers at Guangxi Universities grant number[2024KY1877].
文摘Karst caves are among the most common and critical geological hazards in karst regions.Due to their marked differences in physical properties compared to the surrounding rock,they can be detected using various geophysical techniques.Karsts have developed on the surface of the Qingshuitang Wollastonite Mining Area in Huangtian Town,Hezhou City,Guangxi Province.In line with mine safety production requirements,a professional assessment of the potential development of karst caves must be conducted within 150 m of the mining area’s surface.Following an on-site investiga-tion and comparison with traditional geophysical methods,seismic frequency resonance technology(Seismic FRT)was selected for detection due to its convenience,flexibility,cost-effectiveness,and rapid data acquisition capabilities.Contour maps of the apparent wave impedance and geological profiles along the survey lines were obtained through data collection and processing.In combination with surface karst and mining geology,32 karst caves(hidden danger points)and 15 karst development zones were identified.Drilling verification was conducted at the A428 and B122 anomalous points on the A1# and B1# survey lines.The verification results were consistent with the inferred depths and maximum apparent wave impedance anomalies,confirming that Seismic FRT is a feasible and effective method for detecting hid-den karst development areas in mines.
基金the Portuguese Foundation for Science and Technology (Fundação para a Ciência e Tecnologia-FCT) under contract UIDB/UIDP/00134/2020The experiments at Lab Oceano were supported by the National Petroleum Agency of Brazil (ANP)
文摘An experimental study is presented on the non-Gaussian statistics of random unidirectional laboratory wave fields described by JONSWAP spectra.Relationships between statistical parameters indicative of the occurrence of largeamplitude waves are discussed in the context of the initial steepness of the waves combined with the effect of spectral peakedness.The spatial evolution of the relevant statistical and spectral parameters and features is also considered.It is demonstrated that over the distance the spectra exhibit features typical for developing nonlinear instabilities,such as spectral broadening and downshift of the peak,along with lowering of the high-frequency tail and decrease of the peak magnitude.The wave fields clearly show an increase of third-order nonlinearity with the distance,which can be significant,depending on the input wave environment.The steeper initial conditions,however,while favouring the occurrence of extremely large waves,also increase the chances of wave breaking and loss of energy due to dissipation,which results in lower extreme crests and wave heights.The applied Miche-Stokes-type criteria do confirm that some of the wave extremes exceed the limiting individual steepness.Eventually,this result agrees with the observation that the largest number of abnormal waves is recorded in sea states with moderate steepness.
基金supported by National Natural Science Foundation of China(Grant No. 10772061)Heilongjiang Provincial Natural Science Foundation of China(Grant No. A200907)Specialized Research Fundfor the Doctoral Program of Higher Education of China(Grant No.20092322120001)
文摘Detecting stress concentration, especially critical stress state leading to structure damage or failure, is one of the most important tasks of equipment diagnosis. Metal magnetic memory technique needs further research to evaluate stress concentration quantitatively due to ambiguous physical mechanism, though it has potential to detect early defects in ferromagnetic materials. Mild Q235 steel defective specimens in demagnetization state were loaded in tension up to visible necking, with magnetic memory signals measurement made at increasing stress levels. Magnetic signals varied greatly under first several loadings and subsequently tended to stability in the elastic region, which showed that the magnetization always approaches the anhysteretic magnetization curve and was explained by the theory of magnetomechanical effect. In the plastic stage, an abnormal wave occurred in the stress concentration zone and its height value was sensitive to plastic deformation levels and dependent on the distance between the probe and defect, in accordance with the simulation results based on the magnetic dipole model. Different magnetic signal characteristics in the elastic-plastic region indicate that the magnetic memory technique can identify macroyielding and early damage, which is of profound significance for ensuring safe operation of equipment in service.
