A suction caisson can be extracted by applying reverse pumping water,which cannot be regarded as the reverse process of installation because of the dramatically different soil−structure interaction behavior.Model test...A suction caisson can be extracted by applying reverse pumping water,which cannot be regarded as the reverse process of installation because of the dramatically different soil−structure interaction behavior.Model tests were first carried out in this study to investigate the extraction behavior of the modified suction caisson(MSC)and the regular suction caisson(RSC)in sand by reverse pumping water.The effects of the installation ways(suction-assisted or jacking installation)and the reverse pumping rate on the variations of the over-pressure resulting form reverse pumping water were investigated.It was found that neither the RSC nor the MSC can be fully extracted from sand.When the maximum extraction displacement is obtained,the hydraulic gradient of the sand in the suction caisson reaches the critical value,leading to seepage failure.In addition,the maximum extraction displacement decreases with the increasing reverse pumping rate.Under the same reverse pumping rate,the final extraction displacements for the RSC and MSC installed by suction are lower than those for the RSC and MSC installed by jacking.The final extraction displacement of MSC is almost equal to that of the RSC with the same internal compartment length.Based on the force equilibrium,a method of estimating the maximum extraction displacement is proposed.It has been proved that the proposed method can rationally predict the maximum extraction displacement and the corresponding over-pressure.展开更多
Stereo-digital image correlation(Stereo-DIC)has been widely explored for modal analysis in plate-type structures due to its noncontact and full-field advantages.However,when the traditional stereo-DIC is adopted to ca...Stereo-digital image correlation(Stereo-DIC)has been widely explored for modal analysis in plate-type structures due to its noncontact and full-field advantages.However,when the traditional stereo-DIC is adopted to capture the out-of-plane displacements,several challenging issues exist such as the development of surface speckles,asynchronous camera recording,and efficiency and accuracy degradation due to high computation costs.Moreover,with the captured out-of-plane displacements,effective and efficient evaluation of the high spatial resolution mode shapes and their application to damage localization are also critical problems.To tackle these issues,a speckle-projection DIC technique using a single high‐speed camera is proposed to obtain the out-of-plane vibration displacements.Moreover,an enhanced peak-picking modal analysis method is adopted to enhance the estimation accuracy and efficiency of mode shapes.In addition,the low‐rank property of mode shapes in an intact state and the spatial sparse property of damage locations are harnessed for the detection of damage positions without requiring reference data on the healthy state.Finally,the modal analysis and damage localization results based on the proposed speckle-projection DIC are compared with those of the traditional two-camera stereo-DIC technique to verify its feasibility and effectiveness.It is found that the differences in the identified resonant frequencies between these two methods are smaller than 1%for higher modes.Moreover,the proposed speckle-projection DIC has the same accuracy as the traditional two-camera stereo-DIC in terms of measurement accuracy,mode shape estimation,and damage localization.展开更多
基金This study was financially supported by the National Natural Science Foundation of China(Grant Nos.51879044 and 51639002)the Shandong Natural Fund(Grant No.ZR2019BEE007)+1 种基金SDUST Research Fund(Grant No.2015TDJH104)the Project oce and Technology Program(Grant No.J18KA184).
文摘A suction caisson can be extracted by applying reverse pumping water,which cannot be regarded as the reverse process of installation because of the dramatically different soil−structure interaction behavior.Model tests were first carried out in this study to investigate the extraction behavior of the modified suction caisson(MSC)and the regular suction caisson(RSC)in sand by reverse pumping water.The effects of the installation ways(suction-assisted or jacking installation)and the reverse pumping rate on the variations of the over-pressure resulting form reverse pumping water were investigated.It was found that neither the RSC nor the MSC can be fully extracted from sand.When the maximum extraction displacement is obtained,the hydraulic gradient of the sand in the suction caisson reaches the critical value,leading to seepage failure.In addition,the maximum extraction displacement decreases with the increasing reverse pumping rate.Under the same reverse pumping rate,the final extraction displacements for the RSC and MSC installed by suction are lower than those for the RSC and MSC installed by jacking.The final extraction displacement of MSC is almost equal to that of the RSC with the same internal compartment length.Based on the force equilibrium,a method of estimating the maximum extraction displacement is proposed.It has been proved that the proposed method can rationally predict the maximum extraction displacement and the corresponding over-pressure.
基金This study was funded by the National Natural Science Foundation of China(No.12102346).
文摘Stereo-digital image correlation(Stereo-DIC)has been widely explored for modal analysis in plate-type structures due to its noncontact and full-field advantages.However,when the traditional stereo-DIC is adopted to capture the out-of-plane displacements,several challenging issues exist such as the development of surface speckles,asynchronous camera recording,and efficiency and accuracy degradation due to high computation costs.Moreover,with the captured out-of-plane displacements,effective and efficient evaluation of the high spatial resolution mode shapes and their application to damage localization are also critical problems.To tackle these issues,a speckle-projection DIC technique using a single high‐speed camera is proposed to obtain the out-of-plane vibration displacements.Moreover,an enhanced peak-picking modal analysis method is adopted to enhance the estimation accuracy and efficiency of mode shapes.In addition,the low‐rank property of mode shapes in an intact state and the spatial sparse property of damage locations are harnessed for the detection of damage positions without requiring reference data on the healthy state.Finally,the modal analysis and damage localization results based on the proposed speckle-projection DIC are compared with those of the traditional two-camera stereo-DIC technique to verify its feasibility and effectiveness.It is found that the differences in the identified resonant frequencies between these two methods are smaller than 1%for higher modes.Moreover,the proposed speckle-projection DIC has the same accuracy as the traditional two-camera stereo-DIC in terms of measurement accuracy,mode shape estimation,and damage localization.
