In the evaluation of road roughness and its effects on vehicles response in terms of ride quality, loads induced on pavement, drivers＇ comfort, etc., it is very common to generate road profles based on the equation p...In the evaluation of road roughness and its effects on vehicles response in terms of ride quality, loads induced on pavement, drivers＇ comfort, etc., it is very common to generate road profles based on the equation provided by ISO 8608 standard, according to which it is possible to group road surface profiles into eight different classes. However, real profiles are significantly different from the artificial ones because of the non-stationary fea- ture of the first ones and the not full capability of the ISO 8608 equation to correctly describe the frequency content of real road profiles. In this paper, the international roughness index, the frequency-weighted vertical acceleration awz according to ISO 2631, and the dynamic load index are applied both on artificial and real profiles, highlighting the different results obtained. The analysis carried out in this work has highlighted some limitation of the ISO 8608 approach in the description of performance and conditions of real pavement profiles. Furthermore, the different sensitivity of the various indices to the fitted power spectral density parameters is shown, which should be taken into account when performing analysis using artificial profiles.展开更多
The dynamic frictional behaviors of natural discontinuities(joints,fractures,faults)play an important role in geohazards assessment;however,the mechanisms of the dynamic fault weakening/strengthening are still unclear...The dynamic frictional behaviors of natural discontinuities(joints,fractures,faults)play an important role in geohazards assessment;however,the mechanisms of the dynamic fault weakening/strengthening are still unclear.In this paper,a dynamic shear box was used to perform direct shear tests on saw-cut(planar)and natural(rough)granite fractures,with different normal load oscillation amplitudes.Based on the recorded shear forces and normal displacements,the shear forces,apparent friction coefficients and normal displacements are found to change periodically with oscillated normal loads and are characterized by a series of time shifts.The observed changing patterns are similar for the rough and planar fractures.Compared with the test data under constant normal load(CNL),small/large normal load oscillation amplitude enhances/reduces the peak shear strength,with a critical point.The magnitude of critical normal load oscillation for the rough fractures is smaller than the planer fractures.The results imply that dynamic fault weakening/strengthening can be achieved by both normal load oscillation amplitudes and slip surface topography.The rough fractures with larger normal oscillation amplitude can easily cause frictional weakening under stress disturbance.展开更多
文摘In the evaluation of road roughness and its effects on vehicles response in terms of ride quality, loads induced on pavement, drivers＇ comfort, etc., it is very common to generate road profles based on the equation provided by ISO 8608 standard, according to which it is possible to group road surface profiles into eight different classes. However, real profiles are significantly different from the artificial ones because of the non-stationary fea- ture of the first ones and the not full capability of the ISO 8608 equation to correctly describe the frequency content of real road profiles. In this paper, the international roughness index, the frequency-weighted vertical acceleration awz according to ISO 2631, and the dynamic load index are applied both on artificial and real profiles, highlighting the different results obtained. The analysis carried out in this work has highlighted some limitation of the ISO 8608 approach in the description of performance and conditions of real pavement profiles. Furthermore, the different sensitivity of the various indices to the fitted power spectral density parameters is shown, which should be taken into account when performing analysis using artificial profiles.
基金the funding support from the National Natural Science Foundation of China (Grant No. 51904359)the Guangdong Provincial Department of Science and Technology (Grant No. 2019ZT08G090)the Open Research Fund of the State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology (CUMT) (Grant No. SKLCRSM20KF002)
文摘The dynamic frictional behaviors of natural discontinuities(joints,fractures,faults)play an important role in geohazards assessment;however,the mechanisms of the dynamic fault weakening/strengthening are still unclear.In this paper,a dynamic shear box was used to perform direct shear tests on saw-cut(planar)and natural(rough)granite fractures,with different normal load oscillation amplitudes.Based on the recorded shear forces and normal displacements,the shear forces,apparent friction coefficients and normal displacements are found to change periodically with oscillated normal loads and are characterized by a series of time shifts.The observed changing patterns are similar for the rough and planar fractures.Compared with the test data under constant normal load(CNL),small/large normal load oscillation amplitude enhances/reduces the peak shear strength,with a critical point.The magnitude of critical normal load oscillation for the rough fractures is smaller than the planer fractures.The results imply that dynamic fault weakening/strengthening can be achieved by both normal load oscillation amplitudes and slip surface topography.The rough fractures with larger normal oscillation amplitude can easily cause frictional weakening under stress disturbance.
