The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined ...The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.展开更多
Locked segments are recognized as a critical role that controls the stability of rock slopes but remain an unclear and challenging problem with respect to their role incorporated into the failure mechanism.In order to...Locked segments are recognized as a critical role that controls the stability of rock slopes but remain an unclear and challenging problem with respect to their role incorporated into the failure mechanism.In order to study the effect of the locked segments on the initial failure process of rockslides,thirty-six groups of locked segment specimens with three different lithologies were prepared,direct shear tests were carried out to obtain the accelerations caused by brittle failure of the locked segment specimens.Experiment results showed that the maximum accelerations caused by the brittle failure of locked segment specimens was 2.91 g in the horizontal direction,and 3.18 g in the vertical direction.We took the Wangjiayan rockslide in 2008 Wenchuan earthquake as an example,the critical balance condition of the sliding mass under combined effect of gravity and accelerations induced by brittle failure of locked segment was analyzed,which indicated that the initial failure process of the Wangjiayan rockslides was notably influenced by the existence of the locked segment.The departure acceleration and direction of the Wangjiayan rockslide were proposed.The study results can provide a new insight into the understanding of the initial failure mechanism of rockslides with locked segments.展开更多
The behavior of nonlinear vibration for symmetric angle-ply laminated plates including the material viscoelasticity and damage evolution is investigated. By employing the von Karman＇s nonlinear theory, strain energy ...The behavior of nonlinear vibration for symmetric angle-ply laminated plates including the material viscoelasticity and damage evolution is investigated. By employing the von Karman＇s nonlinear theory, strain energy equivalence principle and Boltzmann superposition principle, a set of governing equations of nonlinear integro-differential type are derived. By applying the finite difference method, Newmark method and iterative procedure, the governing equations are solved. The effects of loading amplitudes, exciting frequencies and different ply orientations on the critical time to failure initiation and nonlinear vibration amplitudes of the structures are discussed. Numerical results are presented for the different parameters and compared with the available data.展开更多
Objective: To conduct a hierarchical classification analysis of the nonreportable results of noninvasive prenatal testing in an attempt to reduce failure rates and provide pregnant women with accurate information to a...Objective: To conduct a hierarchical classification analysis of the nonreportable results of noninvasive prenatal testing in an attempt to reduce failure rates and provide pregnant women with accurate information to alleviate their anxiety.Methods: In this study,30,039 singleton pregnancies who underwent noninvasive prenatal testing in a single center from May 2019 to April 2022 were collected,and 811 samples with initial noninvasive prenatal testing failure were retrospectively analyzed.Grouping was based on the reasons for initial test failure;tracking the noninvasive prenatal testing results and prenatal diagnosis results(if any)of the“z-scores in the gray area”group and analyzing the possible influencing factors of the“low fetal fraction”group in the pre-experimental and experimental period by using one-way analysis of variance,Mann-Whitney U test,and χ^(2) test;and tracking the pregnancy outcomes of the test failures samples to analyze the risk of perinatal complications and adverse pregnancy outcomes of the different types of test failures.Results: None of the samples'initial inconclusive results because of z-scores in the gray area were found to have chromosomal aneuploidy.However,pregnancy complications(P=0.018)and a high likelihood of adverse pregnancy outcomes(P=0.048)may still occur.Maternal gestational age(P<0.001),body mass index(P<0.001),library concentration(P<0.001),and fetal gender(P<0.001)were considered to be the associated factors for the initial low fetal fraction results.This may be associated with pregnancy complications(P<0.001)and a high likelihood of adverse pregnancy outcomes(P=0.034).The body mass index(P=0.015)and time between draws(P=0.001)were associated with the second test’s success.The incidence of low fetal fraction samples was more frequent with blood collection tubes of the G type than with the K type(P<0.001).Conclusion: Initial inconclusive results because of z-scores in the gray area did not imply an increased risk of aneuploidy,but vigilance is needed for an increased risk of pregnancy complications and adverse pregnancy outcomes.Because of the low fetal fraction,the initial absence of results may be related to the assay method,as well as the effect of blood collection tubes and the need to be alert to the risk of pregnancy complications and adverse pregnancy outcomes.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42277165,41920104007)the Hubei Natural Science Foundation(Grant No.2023AFD217).
文摘The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.
基金supported by the National Natural Science Foundation of China (Grant No. 41672295)
文摘Locked segments are recognized as a critical role that controls the stability of rock slopes but remain an unclear and challenging problem with respect to their role incorporated into the failure mechanism.In order to study the effect of the locked segments on the initial failure process of rockslides,thirty-six groups of locked segment specimens with three different lithologies were prepared,direct shear tests were carried out to obtain the accelerations caused by brittle failure of the locked segment specimens.Experiment results showed that the maximum accelerations caused by the brittle failure of locked segment specimens was 2.91 g in the horizontal direction,and 3.18 g in the vertical direction.We took the Wangjiayan rockslide in 2008 Wenchuan earthquake as an example,the critical balance condition of the sliding mass under combined effect of gravity and accelerations induced by brittle failure of locked segment was analyzed,which indicated that the initial failure process of the Wangjiayan rockslides was notably influenced by the existence of the locked segment.The departure acceleration and direction of the Wangjiayan rockslide were proposed.The study results can provide a new insight into the understanding of the initial failure mechanism of rockslides with locked segments.
基金The project supported by the National Natural Science Foundation of China(10272042)the Special Science Fund of the Doctoral Discipline of the Ministry of Education.China(20020532018)
文摘The behavior of nonlinear vibration for symmetric angle-ply laminated plates including the material viscoelasticity and damage evolution is investigated. By employing the von Karman＇s nonlinear theory, strain energy equivalence principle and Boltzmann superposition principle, a set of governing equations of nonlinear integro-differential type are derived. By applying the finite difference method, Newmark method and iterative procedure, the governing equations are solved. The effects of loading amplitudes, exciting frequencies and different ply orientations on the critical time to failure initiation and nonlinear vibration amplitudes of the structures are discussed. Numerical results are presented for the different parameters and compared with the available data.
基金funded by the Key Project on Science and Technology Program of Fujian Health Commission(No.2021ZD01002)the Natural Science Foundation of Xiamen,China(Grant No.3502Z20227299)+1 种基金the General Science and Technology Project of Xiamen,China(Grant No.3502Z20224014)the Medical Innovation Project of Fujian Province(Grant No.2021CXB025).
文摘Objective: To conduct a hierarchical classification analysis of the nonreportable results of noninvasive prenatal testing in an attempt to reduce failure rates and provide pregnant women with accurate information to alleviate their anxiety.Methods: In this study,30,039 singleton pregnancies who underwent noninvasive prenatal testing in a single center from May 2019 to April 2022 were collected,and 811 samples with initial noninvasive prenatal testing failure were retrospectively analyzed.Grouping was based on the reasons for initial test failure;tracking the noninvasive prenatal testing results and prenatal diagnosis results(if any)of the“z-scores in the gray area”group and analyzing the possible influencing factors of the“low fetal fraction”group in the pre-experimental and experimental period by using one-way analysis of variance,Mann-Whitney U test,and χ^(2) test;and tracking the pregnancy outcomes of the test failures samples to analyze the risk of perinatal complications and adverse pregnancy outcomes of the different types of test failures.Results: None of the samples'initial inconclusive results because of z-scores in the gray area were found to have chromosomal aneuploidy.However,pregnancy complications(P=0.018)and a high likelihood of adverse pregnancy outcomes(P=0.048)may still occur.Maternal gestational age(P<0.001),body mass index(P<0.001),library concentration(P<0.001),and fetal gender(P<0.001)were considered to be the associated factors for the initial low fetal fraction results.This may be associated with pregnancy complications(P<0.001)and a high likelihood of adverse pregnancy outcomes(P=0.034).The body mass index(P=0.015)and time between draws(P=0.001)were associated with the second test’s success.The incidence of low fetal fraction samples was more frequent with blood collection tubes of the G type than with the K type(P<0.001).Conclusion: Initial inconclusive results because of z-scores in the gray area did not imply an increased risk of aneuploidy,but vigilance is needed for an increased risk of pregnancy complications and adverse pregnancy outcomes.Because of the low fetal fraction,the initial absence of results may be related to the assay method,as well as the effect of blood collection tubes and the need to be alert to the risk of pregnancy complications and adverse pregnancy outcomes.
