In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confine...In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confined water on the limit support pressure of the tunnel face.This study employed the finite element method(FEM)to analyze the limit support pressure of shield tunnel face instability within a pressurized water-containing layer.Subsequently,a multiple linear regression approach was applied to derive a concise solution formula for the limit support pressure,incorporating various influencing factors.The analysis yields the following conclusions:1)The influence of confined water on the instability mode of the tunnel face in soft soil layers makes the displacement response of the strata not significant when the face is unstable;2)The limit support pressure increases approximately linearly with the pressure head,shield tunnel diameter,and tunnel burial depth.And inversely proportional to the thickness of the impermeable layer,soil cohesion and internal friction angle;3)Through an engineering case study analysis,the results align well with those obtained from traditional theoretical methods,thereby validating the rationality of the equations proposed in this paper.Furthermore,the proposed equations overcome the limitation of traditional theoretical approaches considering the influence of changes in impermeable layer thickness.It can accurately depict the dynamic variation in the required limit support pressure to maintain the stability of the tunnel face during shield tunneling,thus better reflecting engineering reality.展开更多
具有乳头样核特征的非浸润性甲状腺滤泡性肿瘤(noninvasive follicular thyroid neoplasm with papillary-like nuclear features,NIFTP),原名为非浸润性包裹型甲状腺乳头状癌滤泡亚型(noninvasive encapsulated follicular variant of ...具有乳头样核特征的非浸润性甲状腺滤泡性肿瘤(noninvasive follicular thyroid neoplasm with papillary-like nuclear features,NIFTP),原名为非浸润性包裹型甲状腺乳头状癌滤泡亚型(noninvasive encapsulated follicular variant of papillary carcinoma of the thyroid,EFVPTC),呈滤泡状生长,被膜完整,无侵袭性但具有乳头状癌核特征[1]。展开更多
This paper presents a case study of water inrush and mud burst occurring in a migmatite tunnel to study its formation mechanisms. The geological investigation and mineralogical analysis showed that water inrush and mu...This paper presents a case study of water inrush and mud burst occurring in a migmatite tunnel to study its formation mechanisms. The geological investigation and mineralogical analysis showed that water inrush and mud burst in the migmatite was closely related to the component of the host rock. High content of soluble minerals,e.g.,calcite and dolomite,would make the migmatite rock prone to be fragmentized,isintegrated and eventually form different sorts of connected or semi-connected veins. The field exploration revealed most cavities in the magmatite tunnel were eroded by groundwater and formed large interconnected networks. The two faults and the dike in the magmatite tunnel became the preferred paths and provided great convenience for plenty of precipitation and mud slurry. Due to high water pressure and blast disturbance,the cavities can soon connect each other as well as all sorts of veins,forming a complex ground channel for water inrush and mud burst. To estimate the potential occurrenceof water inrush and mud burst,the water bursting coefficient was employed. The results showed the water bursting coefficient of the magmatite tunnel was much bigger than the threshold values and it can be used to explain the accident of water inrush and mud burst occurring in the magmatite tunnel.展开更多
若补偿干涉仪对外界环境的抗噪性能差,将会提高系统的相位噪声本底,降低传感器的探测性能。从结构设计角度对干涉仪进行相关设计,包括隔声设计、减振设计及吸声设计。试验发现采用新型结构补偿光纤干涉仪,整个系统的本底噪声得到了降低,...若补偿干涉仪对外界环境的抗噪性能差,将会提高系统的相位噪声本底,降低传感器的探测性能。从结构设计角度对干涉仪进行相关设计,包括隔声设计、减振设计及吸声设计。试验发现采用新型结构补偿光纤干涉仪,整个系统的本底噪声得到了降低,1 k Hz位置降低了约16 d B,100 Hz位置降低了约15 d B,提高了系统的探测性能。展开更多
基金Project(ZDRW-ZS-2021-3)supported by the Key Deployment Projects of Chinese Academy of SciencesProjects(52179116,51991392)supported by the National Natural Science Foundation of China。
文摘In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confined water on the limit support pressure of the tunnel face.This study employed the finite element method(FEM)to analyze the limit support pressure of shield tunnel face instability within a pressurized water-containing layer.Subsequently,a multiple linear regression approach was applied to derive a concise solution formula for the limit support pressure,incorporating various influencing factors.The analysis yields the following conclusions:1)The influence of confined water on the instability mode of the tunnel face in soft soil layers makes the displacement response of the strata not significant when the face is unstable;2)The limit support pressure increases approximately linearly with the pressure head,shield tunnel diameter,and tunnel burial depth.And inversely proportional to the thickness of the impermeable layer,soil cohesion and internal friction angle;3)Through an engineering case study analysis,the results align well with those obtained from traditional theoretical methods,thereby validating the rationality of the equations proposed in this paper.Furthermore,the proposed equations overcome the limitation of traditional theoretical approaches considering the influence of changes in impermeable layer thickness.It can accurately depict the dynamic variation in the required limit support pressure to maintain the stability of the tunnel face during shield tunneling,thus better reflecting engineering reality.
文摘具有乳头样核特征的非浸润性甲状腺滤泡性肿瘤(noninvasive follicular thyroid neoplasm with papillary-like nuclear features,NIFTP),原名为非浸润性包裹型甲状腺乳头状癌滤泡亚型(noninvasive encapsulated follicular variant of papillary carcinoma of the thyroid,EFVPTC),呈滤泡状生长,被膜完整,无侵袭性但具有乳头状癌核特征[1]。
基金support of the National Natural Science Foundation of China (Grant Nos.51379007,41130742)the support of the Chinese Fundamental Research (973)Program through the Grant No.2013CB036006
文摘This paper presents a case study of water inrush and mud burst occurring in a migmatite tunnel to study its formation mechanisms. The geological investigation and mineralogical analysis showed that water inrush and mud burst in the migmatite was closely related to the component of the host rock. High content of soluble minerals,e.g.,calcite and dolomite,would make the migmatite rock prone to be fragmentized,isintegrated and eventually form different sorts of connected or semi-connected veins. The field exploration revealed most cavities in the magmatite tunnel were eroded by groundwater and formed large interconnected networks. The two faults and the dike in the magmatite tunnel became the preferred paths and provided great convenience for plenty of precipitation and mud slurry. Due to high water pressure and blast disturbance,the cavities can soon connect each other as well as all sorts of veins,forming a complex ground channel for water inrush and mud burst. To estimate the potential occurrenceof water inrush and mud burst,the water bursting coefficient was employed. The results showed the water bursting coefficient of the magmatite tunnel was much bigger than the threshold values and it can be used to explain the accident of water inrush and mud burst occurring in the magmatite tunnel.
文摘若补偿干涉仪对外界环境的抗噪性能差,将会提高系统的相位噪声本底,降低传感器的探测性能。从结构设计角度对干涉仪进行相关设计,包括隔声设计、减振设计及吸声设计。试验发现采用新型结构补偿光纤干涉仪,整个系统的本底噪声得到了降低,1 k Hz位置降低了约16 d B,100 Hz位置降低了约15 d B,提高了系统的探测性能。
