Optical and visual measurement technology is used widely in fields that involve geometric measurements,and among such technology are laser and vision-based displacement measuring modules(LVDMMs).The displacement trans...Optical and visual measurement technology is used widely in fields that involve geometric measurements,and among such technology are laser and vision-based displacement measuring modules(LVDMMs).The displacement transformation coefficient(DTC)of an LVDMM changes with the coordinates in the camera image coordinate system during the displacement measuring process,and these changes affect the displacement measurement accuracy of LVDMMs in the full field of view(FFOV).To give LVDMMs higher accuracy in the FFOV and make them adaptable to widely varying measurement demands,a new calibration method is proposed to improve the displacement measurement accuracy of LVDMMs in the FFOV.First,an image coordinate system,a pixel measurement coordinate system,and a displacement measurement coordinate system are established on the laser receiving screen of the LVDMM.In addition,marker spots in the FFOV are selected,and the DTCs at the marker spots are obtained from calibration experiments.Also,a fitting method based on locally weighted scatterplot smoothing(LOWESS)is selected,and with this fitting method the distribution functions of the DTCs in the FFOV are obtained based on the DTCs at the marker spots.Finally,the calibrated distribution functions of the DTCs are applied to the LVDMM,and experiments conducted to verify the displacement measurement accuracies are reported.The results show that the FFOV measurement accuracies for horizontal and vertical displacements are better than±15μm and±19μm,respectively,and that for oblique displacement is better than±24μm.Compared with the traditional calibration method,the displacement measurement error in the FFOV is now 90%smaller.This research on an improved calibration method has certain significance for improving the measurement accuracy of LVDMMs in the FFOV,and it provides a new method and idea for other vision-based fields in which camera parameters must be calibrated.展开更多
The variation of in situ stress before and after earthquakes is an issue studied by geologists. In this paper, on the basis of the fault slip dislocation model of Wenchuan Ms8.0 earthquake, the changes of co-seismic d...The variation of in situ stress before and after earthquakes is an issue studied by geologists. In this paper, on the basis of the fault slip dislocation model of Wenchuan Ms8.0 earthquake, the changes of co-seismic displacement and the distribution functions of stress tensor around the Longmen Shan fault zone are calculated. The results show that the co-seismic maximum surface displacement is 4.9 m in the horizontal direction and 6.5 m in the vertical direction, which is almost consistent with the on-site survey and GPS observations. The co-seismic maximum horizontal stress in the hanging wall and footwall decreased sharply as the distance from the Longmen Shan fault zone increased. However, the vertical stress and minimum horizontal stress increased in the footwall and in some areas of the hanging wall. The study of the co-seismic displacement and stress was mainly focused on the long and narrow region along the Longmen Shan fault zone, which coincides with the distribution of the earthquake aftershocks. Therefore, the co-seismic stress only affects the aftershocks, and does not affect distant faults and seismic activities. The results are almost consistent with in situ stress measurements at the two sites before and after Wenchuan Ms8.0 earthquake. Along the fault plane, the co-seismic shear stress in the dip direction is larger than that in the strike direction, which indicates that the faulting mechanism of the Longmen Shan fault zone is a dominant thrust with minor strike-slipping. The results can be used as a reference value for future studies of earthquake mechanisms.展开更多
Based on significant improvements in engineering materials,three advanced engineering measures have been proposed-super anchor cables,high-strength concrete anti-fault caverns,and grouting modification using high-stre...Based on significant improvements in engineering materials,three advanced engineering measures have been proposed-super anchor cables,high-strength concrete anti-fault caverns,and grouting modification using high-strength concrete-to resist fault dislocation in the surrounding rock near tunnels crossing active strike-slip faults.Moreover,single-or multiple-joint advanced engineering measures form the local rock mass-anti-fault(LRAF)method.A numerical method was used to investigate the influence of LRAF methods on the stress and displacement fields of the surrounding rock,and the anti-fault effect was evaluated.Finally,the mechanism of action of the anchor cable was verified using a three-dimensional numerical model.The numerical results indicated that the anchor cable and grouting modification reduced the displacement gradient of the local surrounding rock near the tunnels crossing fault.Furthermore,anchor cable and grouting modifications changed the stress field of the rock mass in the modified area.The tensile stress field of the rock mass in the modified anchor cable area was converted into a compressive stress field.The stress field in the modified grouting area changed from shear stress in the fault slip direction to tensile stress in the axial tunnel direction.The anti-fault cavern resisted the dislocation displacement and reduced the maximum dislocation magnitude,displacement gradient,and shear stress.Among the three advanced engineering measures,the anchor cable was the core of the three advanced engineering measures.An anchor cable,combined with other LRAF measures,can form an artificial safety island at the cross-fault position of the rock mass to protect the tunnel.The research results provide a new supporting idea for the surrounding rock of tunnels crossing active strike-slip faults.展开更多
We describe a new method for angular displacement measurements that is based on a Fabry-Perot interferometer. A measurement accuracy of 10-8 rad is obtained by use of the sinusoidal phase modulating interferometry. An...We describe a new method for angular displacement measurements that is based on a Fabry-Perot interferometer. A measurement accuracy of 10-8 rad is obtained by use of the sinusoidal phase modulating interferometry. Another Fabry-Perot interferometer is used to obtain the key initial angle of incidence.展开更多
The numerical moire method with sensitivity as high as 0.03 nm has been presented. A quantitative displacement and strain analysis program has been proposed by using this method. It is applied to an edge dislocation a...The numerical moire method with sensitivity as high as 0.03 nm has been presented. A quantitative displacement and strain analysis program has been proposed by using this method. It is applied to an edge dislocation and a stacking fault in aluminum. The measured strain of edge dislocation is compared with theoretical prediction given by Peierls-Nabarro dislocation model. The displacement of stacking fault is also obtained.展开更多
基金supported financially by the National Natural Science Foundation of China (NSFC) (Grant No.51775378)the Key Projects in Tianjin Science&Technology Support Program (Grant No.19YFZC GX00890).
文摘Optical and visual measurement technology is used widely in fields that involve geometric measurements,and among such technology are laser and vision-based displacement measuring modules(LVDMMs).The displacement transformation coefficient(DTC)of an LVDMM changes with the coordinates in the camera image coordinate system during the displacement measuring process,and these changes affect the displacement measurement accuracy of LVDMMs in the full field of view(FFOV).To give LVDMMs higher accuracy in the FFOV and make them adaptable to widely varying measurement demands,a new calibration method is proposed to improve the displacement measurement accuracy of LVDMMs in the FFOV.First,an image coordinate system,a pixel measurement coordinate system,and a displacement measurement coordinate system are established on the laser receiving screen of the LVDMM.In addition,marker spots in the FFOV are selected,and the DTCs at the marker spots are obtained from calibration experiments.Also,a fitting method based on locally weighted scatterplot smoothing(LOWESS)is selected,and with this fitting method the distribution functions of the DTCs in the FFOV are obtained based on the DTCs at the marker spots.Finally,the calibrated distribution functions of the DTCs are applied to the LVDMM,and experiments conducted to verify the displacement measurement accuracies are reported.The results show that the FFOV measurement accuracies for horizontal and vertical displacements are better than±15μm and±19μm,respectively,and that for oblique displacement is better than±24μm.Compared with the traditional calibration method,the displacement measurement error in the FFOV is now 90%smaller.This research on an improved calibration method has certain significance for improving the measurement accuracy of LVDMMs in the FFOV,and it provides a new method and idea for other vision-based fields in which camera parameters must be calibrated.
基金supported by the Sinoprobe Deep Exploration in China(SinoProbe-07)research funds of the Institute of Geomechanics,Chinese Academy of Geological Sciences(Grant No.DZLXJK201105)National Basic Research Program of China(973 Program)(Grant No.2008CB425702)
文摘The variation of in situ stress before and after earthquakes is an issue studied by geologists. In this paper, on the basis of the fault slip dislocation model of Wenchuan Ms8.0 earthquake, the changes of co-seismic displacement and the distribution functions of stress tensor around the Longmen Shan fault zone are calculated. The results show that the co-seismic maximum surface displacement is 4.9 m in the horizontal direction and 6.5 m in the vertical direction, which is almost consistent with the on-site survey and GPS observations. The co-seismic maximum horizontal stress in the hanging wall and footwall decreased sharply as the distance from the Longmen Shan fault zone increased. However, the vertical stress and minimum horizontal stress increased in the footwall and in some areas of the hanging wall. The study of the co-seismic displacement and stress was mainly focused on the long and narrow region along the Longmen Shan fault zone, which coincides with the distribution of the earthquake aftershocks. Therefore, the co-seismic stress only affects the aftershocks, and does not affect distant faults and seismic activities. The results are almost consistent with in situ stress measurements at the two sites before and after Wenchuan Ms8.0 earthquake. Along the fault plane, the co-seismic shear stress in the dip direction is larger than that in the strike direction, which indicates that the faulting mechanism of the Longmen Shan fault zone is a dominant thrust with minor strike-slipping. The results can be used as a reference value for future studies of earthquake mechanisms.
基金supported by the National Natural Science Foundation of China(Grant No.41941018)Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.YJKYYQ20200040)+1 种基金Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(No.ZDBS-LY-DQC022)Knowledge Innovation Program of Wuhan-Basic Research(No.2022010801010160).
文摘Based on significant improvements in engineering materials,three advanced engineering measures have been proposed-super anchor cables,high-strength concrete anti-fault caverns,and grouting modification using high-strength concrete-to resist fault dislocation in the surrounding rock near tunnels crossing active strike-slip faults.Moreover,single-or multiple-joint advanced engineering measures form the local rock mass-anti-fault(LRAF)method.A numerical method was used to investigate the influence of LRAF methods on the stress and displacement fields of the surrounding rock,and the anti-fault effect was evaluated.Finally,the mechanism of action of the anchor cable was verified using a three-dimensional numerical model.The numerical results indicated that the anchor cable and grouting modification reduced the displacement gradient of the local surrounding rock near the tunnels crossing fault.Furthermore,anchor cable and grouting modifications changed the stress field of the rock mass in the modified area.The tensile stress field of the rock mass in the modified anchor cable area was converted into a compressive stress field.The stress field in the modified grouting area changed from shear stress in the fault slip direction to tensile stress in the axial tunnel direction.The anti-fault cavern resisted the dislocation displacement and reduced the maximum dislocation magnitude,displacement gradient,and shear stress.Among the three advanced engineering measures,the anchor cable was the core of the three advanced engineering measures.An anchor cable,combined with other LRAF measures,can form an artificial safety island at the cross-fault position of the rock mass to protect the tunnel.The research results provide a new supporting idea for the surrounding rock of tunnels crossing active strike-slip faults.
基金This work was supported by the National High Tech-nology Development 863 Program(2002aa404050)of China and the Foundation for Development of science of Shanghai(0114nm013),
文摘We describe a new method for angular displacement measurements that is based on a Fabry-Perot interferometer. A measurement accuracy of 10-8 rad is obtained by use of the sinusoidal phase modulating interferometry. Another Fabry-Perot interferometer is used to obtain the key initial angle of incidence.
基金the National Natural Science Foundation of China under Grants No.10562003 and 10272054
文摘The numerical moire method with sensitivity as high as 0.03 nm has been presented. A quantitative displacement and strain analysis program has been proposed by using this method. It is applied to an edge dislocation and a stacking fault in aluminum. The measured strain of edge dislocation is compared with theoretical prediction given by Peierls-Nabarro dislocation model. The displacement of stacking fault is also obtained.
