During the excavation and support process in deep soft rocks,complex conditions such as high stress and strong disturbance can be encountered.The complex conditions can cause failure of the support system.Aiming at st...During the excavation and support process in deep soft rocks,complex conditions such as high stress and strong disturbance can be encountered.The complex conditions can cause failure of the support system.Aiming at stability control in deep soft rocks,we proposed the excavation compensation theory.A new high strength and high toughness material was developed.The breaking load and elongation of the new material are 1.59 and 1.78 times that of common bolt materials.To overcome the problem that the CABLE element in FLAC^(3D) cannot simulate failure of support structures,the numerical model for the whole process of force-breaking-anchorage failure simulation(FBAS)for bolts(cables)was established.The numerical experiments on the excavation compensation control of deep soft rock were carried out.The excavation compensation control mechanism of high strength and high toughness material was clarified.Compared with the common support scheme,the highly prestressed support has a maximum increase of 90.24%in radial stress compensation rate and a maximum increase of 67.85%in deformation control rate.The results illustrate the rationality of the excavation compensation theory.The compensation design method of excavations in deep soft rocks was proposed and applied in a deep soft rock chamber.The monitoring indicated that the maximum surrounding rock deformation is 180 mm,reduced by 64%compared to the common support.The deformation of the chamber was controlled and the surrounding rock was stable.展开更多
In 2021,Cempaka,a tiny tropical cyclone,made landfall in China.As the TC intensified prior to landfall,the tropical cyclone size measured with precipitation decreased significantly.A numerical simulation was conducted...In 2021,Cempaka,a tiny tropical cyclone,made landfall in China.As the TC intensified prior to landfall,the tropical cyclone size measured with precipitation decreased significantly.A numerical simulation was conducted to examine the possible processes modulating the storm size.Azimuthally mean potential vorticity(PV)was found to decrease mainly in the middle to upper troposphere between 50-and 80-km radii.The PV budget results indicate that the advection and generation of mean PV associated with asymmetric processes,rather than the symmetric processes,primarily contributed to the decrease in mean PV.These asymmetric processes leading to a negative PV tendency were likely associated with inactive outer rainbands.In contrast,the tangential winds simultaneously expanded radially outward,possibly related to inner-core diabatic heating.The findings here emphasize the importance of outer rainband activity in tropical cyclone size change.展开更多
对民用航空器结构用碳纤维树脂基复合材料(CFRP)进行吸湿性能研究,测试其吸湿率随时间的变化规律,同时监测吸湿过程中试样电阻率的变化规律,对饱和吸湿试样再进行通电处理,获取脱湿率与通电电流的关系,之后对未处理、吸湿及吸湿/通电处...对民用航空器结构用碳纤维树脂基复合材料(CFRP)进行吸湿性能研究,测试其吸湿率随时间的变化规律,同时监测吸湿过程中试样电阻率的变化规律,对饱和吸湿试样再进行通电处理,获取脱湿率与通电电流的关系,之后对未处理、吸湿及吸湿/通电处理试样进行弯曲性能测试,通过观察弯曲断口处裂纹走向及断口形貌,分析湿热、湿热/电热作用对CFRP弯曲性能的影响。结果表明,试样吸湿率随吸湿时间延长呈先上升后趋于稳定的趋势,其电阻率呈先下降后稳定的变化规律,饱和吸湿试样经通电处理后,脱湿率随电流增加而增大,但试样湿含量不能降低为0。吸湿后小电流2~4 A(ρ=33.4~66.8 m A/mm^2)处理,试样弯曲性能较单纯吸湿试样有所提升,弯曲断裂后试样并未分离成两部分,吸湿后大电流5~6 A(ρ=83.6~100.2 m A/mm^2)处理,造成试样弯曲强度下降,弯曲断裂表现为脆性断裂。展开更多
Geomagnetic storms and substorms play a central role in both the daily life of mankind and in academic space physics.The profiles of storms,especially their initial phase morphology and the intensity of their substorm...Geomagnetic storms and substorms play a central role in both the daily life of mankind and in academic space physics.The profiles of storms,especially their initial phase morphology and the intensity of their substorms under different interplanetary conditions,have usually been ignored in previous studies.In this study,97 intense geomagnetic storms(Dstmin≤–100 nT)between 1998 and 2018 were studied statistically using the double superposed epoch analysis(DSEA)and normalized superposed epoch analysis(NSEA)methods.These storms are categorized into two types according to different interplanetary magnetic field(IMF)Bz orientations:geomagnetic storms whose IMF is northward,both upstream and downstream relative to the interplanetary shock,and geomagnetic storms whose upstream and downstream IMF is consistently southward.We further divide these two types into two subsets,by different geomagnetic storm profiles:Type Ⅰ/Type Ⅱ—one/two-step geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock;Type Ⅲ/TypeⅣ—one/two-step geomagnetic storms with southward IMF both upstream and downstream of the interplanetary shock.The results show that:(1)geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock have a clear initial phase;geomagnetic storms with southward IMF in both upstream and downstream of the interplanetary shock do not;(2)the IMF is an important controlling factor in affecting the intensity characteristics of substorms.When Bz is positive before and after the interplanetary shock arrival,the Auroral Electrojet(AE)index changes gently during the initial phase of geomagnetic storms,the median value of AE index is maintained at 500–1000 nT;(3)when Bz is negative before and after the interplanetary shock arrival,the AE index rises rapidly and reaches its maxmum value about one hour after storm sudden commencements(SSC),although the time is scaled between reference points and the maximum value of AE is usually greater than 1,000 nT,representing intense substorms;(4)for most cases,the Dst0 usually reaches its minimum at least one hour after Bz.These results are useful in improving contemporary space weather models,especially for those that address geomagnetic storms and substorms.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3805700)the National Natural Science Foundation of China(Grant No.42277174)the Fundamental Research Funds for the Central Universities,China(Grant No.2024JCCXSB01).
文摘During the excavation and support process in deep soft rocks,complex conditions such as high stress and strong disturbance can be encountered.The complex conditions can cause failure of the support system.Aiming at stability control in deep soft rocks,we proposed the excavation compensation theory.A new high strength and high toughness material was developed.The breaking load and elongation of the new material are 1.59 and 1.78 times that of common bolt materials.To overcome the problem that the CABLE element in FLAC^(3D) cannot simulate failure of support structures,the numerical model for the whole process of force-breaking-anchorage failure simulation(FBAS)for bolts(cables)was established.The numerical experiments on the excavation compensation control of deep soft rock were carried out.The excavation compensation control mechanism of high strength and high toughness material was clarified.Compared with the common support scheme,the highly prestressed support has a maximum increase of 90.24%in radial stress compensation rate and a maximum increase of 67.85%in deformation control rate.The results illustrate the rationality of the excavation compensation theory.The compensation design method of excavations in deep soft rocks was proposed and applied in a deep soft rock chamber.The monitoring indicated that the maximum surrounding rock deformation is 180 mm,reduced by 64%compared to the common support.The deformation of the chamber was controlled and the surrounding rock was stable.
基金jointly supported by the National Natural Science Foundation of China[grant numbers U2342202 and 42175005]the Qing Lan Project[grant number R2023Q06]。
文摘In 2021,Cempaka,a tiny tropical cyclone,made landfall in China.As the TC intensified prior to landfall,the tropical cyclone size measured with precipitation decreased significantly.A numerical simulation was conducted to examine the possible processes modulating the storm size.Azimuthally mean potential vorticity(PV)was found to decrease mainly in the middle to upper troposphere between 50-and 80-km radii.The PV budget results indicate that the advection and generation of mean PV associated with asymmetric processes,rather than the symmetric processes,primarily contributed to the decrease in mean PV.These asymmetric processes leading to a negative PV tendency were likely associated with inactive outer rainbands.In contrast,the tangential winds simultaneously expanded radially outward,possibly related to inner-core diabatic heating.The findings here emphasize the importance of outer rainband activity in tropical cyclone size change.
文摘对民用航空器结构用碳纤维树脂基复合材料(CFRP)进行吸湿性能研究,测试其吸湿率随时间的变化规律,同时监测吸湿过程中试样电阻率的变化规律,对饱和吸湿试样再进行通电处理,获取脱湿率与通电电流的关系,之后对未处理、吸湿及吸湿/通电处理试样进行弯曲性能测试,通过观察弯曲断口处裂纹走向及断口形貌,分析湿热、湿热/电热作用对CFRP弯曲性能的影响。结果表明,试样吸湿率随吸湿时间延长呈先上升后趋于稳定的趋势,其电阻率呈先下降后稳定的变化规律,饱和吸湿试样经通电处理后,脱湿率随电流增加而增大,但试样湿含量不能降低为0。吸湿后小电流2~4 A(ρ=33.4~66.8 m A/mm^2)处理,试样弯曲性能较单纯吸湿试样有所提升,弯曲断裂后试样并未分离成两部分,吸湿后大电流5~6 A(ρ=83.6~100.2 m A/mm^2)处理,造成试样弯曲强度下降,弯曲断裂表现为脆性断裂。
文摘Geomagnetic storms and substorms play a central role in both the daily life of mankind and in academic space physics.The profiles of storms,especially their initial phase morphology and the intensity of their substorms under different interplanetary conditions,have usually been ignored in previous studies.In this study,97 intense geomagnetic storms(Dstmin≤–100 nT)between 1998 and 2018 were studied statistically using the double superposed epoch analysis(DSEA)and normalized superposed epoch analysis(NSEA)methods.These storms are categorized into two types according to different interplanetary magnetic field(IMF)Bz orientations:geomagnetic storms whose IMF is northward,both upstream and downstream relative to the interplanetary shock,and geomagnetic storms whose upstream and downstream IMF is consistently southward.We further divide these two types into two subsets,by different geomagnetic storm profiles:Type Ⅰ/Type Ⅱ—one/two-step geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock;Type Ⅲ/TypeⅣ—one/two-step geomagnetic storms with southward IMF both upstream and downstream of the interplanetary shock.The results show that:(1)geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock have a clear initial phase;geomagnetic storms with southward IMF in both upstream and downstream of the interplanetary shock do not;(2)the IMF is an important controlling factor in affecting the intensity characteristics of substorms.When Bz is positive before and after the interplanetary shock arrival,the Auroral Electrojet(AE)index changes gently during the initial phase of geomagnetic storms,the median value of AE index is maintained at 500–1000 nT;(3)when Bz is negative before and after the interplanetary shock arrival,the AE index rises rapidly and reaches its maxmum value about one hour after storm sudden commencements(SSC),although the time is scaled between reference points and the maximum value of AE is usually greater than 1,000 nT,representing intense substorms;(4)for most cases,the Dst0 usually reaches its minimum at least one hour after Bz.These results are useful in improving contemporary space weather models,especially for those that address geomagnetic storms and substorms.
