The control of large deformation problems in layered soft rock tunnels needs to solve urgently.The roof problem is particularly severe among the deformation issues in tunnels.This study first analyzes the asymmetric d...The control of large deformation problems in layered soft rock tunnels needs to solve urgently.The roof problem is particularly severe among the deformation issues in tunnels.This study first analyzes the asymmetric deformation modes in layered soft rock tunnels with large deformations.Subsequently,we construct a mechanical model under ideal conditions for controlling the roof of layered soft rock tunnels through high preload with the support of NPR anchor cables.The prominent roles of long and short NPR anchor cables in the support system are also analyzed.The results indicate the significance of high preload in controlling the roof of layered soft rock tunnels.The short NPR anchor cables effectively improve the integrity of the stratified soft rock layers,while the long NPR anchor cables effectively mobilize the self-bearing capacity of deep-stable rock layers.Finally,the high-preload support method with NPR anchor cables is validated to have a good effect on controlling large deformations in layered soft rock tunnels through field monitoring data.展开更多
真空预压作为一种常见的处理高含水率饱和软土的地基加固方式,在大面积围海造陆工程中应用广泛。但是在许多真空预压加固饱和软土的工程案例中存在加固后地基承载力偏低,尤其是深层土体强度提高幅度有限的情况。大量研究表明,真空预压...真空预压作为一种常见的处理高含水率饱和软土的地基加固方式,在大面积围海造陆工程中应用广泛。但是在许多真空预压加固饱和软土的工程案例中存在加固后地基承载力偏低,尤其是深层土体强度提高幅度有限的情况。大量研究表明,真空预压的加固效果受限于两个核心因素:真空度随深度的衰减效应以及细颗粒在排水板附近的富集对水流路径的阻塞作用。针对上述问题,依托乐清湾北港区吹填工程,提出在真空预压加固后期,采用电渗联合真空预压(electro-osmosis with vacuum preloading,简称EVP)进行短期加固以研究土体强度增长规律。试验通过采用大尺寸模型试验池的方式,先按正常的真空预压步骤抽气108 d,待沉降曲线稳定后,开启电渗联合真空预压加固。该阶段分为两个小的阶段,第1阶段持续11 d,然后对阴阳极进行互换开启第2阶段电渗联合真空预压试验,第2阶段持续6.5 d,共进行17.5 d电渗联合真空预压加固。经电渗联合真空预压加固后,20、60、100 cm 3个深度的土体含水率分别降低4.2%、4.84%、2.34%,十字板强度分别提高32%、75%、61.1%。试验结果表明:真空预压后期通过叠加电渗法,可在含水率降幅小于5%的情况下,实现十字板强度较大幅度的提升,特别是对于原先强度较低,单纯真空预压法加固困难的深层土体,强度提升了61%~75%,具有较好的加固效果。展开更多
基金financial support from the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0708)the National Natural Science Foundation of China(No.41941018)the Special Fund of Yueqi Scholars(No.800015Z1207).
文摘The control of large deformation problems in layered soft rock tunnels needs to solve urgently.The roof problem is particularly severe among the deformation issues in tunnels.This study first analyzes the asymmetric deformation modes in layered soft rock tunnels with large deformations.Subsequently,we construct a mechanical model under ideal conditions for controlling the roof of layered soft rock tunnels through high preload with the support of NPR anchor cables.The prominent roles of long and short NPR anchor cables in the support system are also analyzed.The results indicate the significance of high preload in controlling the roof of layered soft rock tunnels.The short NPR anchor cables effectively improve the integrity of the stratified soft rock layers,while the long NPR anchor cables effectively mobilize the self-bearing capacity of deep-stable rock layers.Finally,the high-preload support method with NPR anchor cables is validated to have a good effect on controlling large deformations in layered soft rock tunnels through field monitoring data.
文摘真空预压作为一种常见的处理高含水率饱和软土的地基加固方式,在大面积围海造陆工程中应用广泛。但是在许多真空预压加固饱和软土的工程案例中存在加固后地基承载力偏低,尤其是深层土体强度提高幅度有限的情况。大量研究表明,真空预压的加固效果受限于两个核心因素:真空度随深度的衰减效应以及细颗粒在排水板附近的富集对水流路径的阻塞作用。针对上述问题,依托乐清湾北港区吹填工程,提出在真空预压加固后期,采用电渗联合真空预压(electro-osmosis with vacuum preloading,简称EVP)进行短期加固以研究土体强度增长规律。试验通过采用大尺寸模型试验池的方式,先按正常的真空预压步骤抽气108 d,待沉降曲线稳定后,开启电渗联合真空预压加固。该阶段分为两个小的阶段,第1阶段持续11 d,然后对阴阳极进行互换开启第2阶段电渗联合真空预压试验,第2阶段持续6.5 d,共进行17.5 d电渗联合真空预压加固。经电渗联合真空预压加固后,20、60、100 cm 3个深度的土体含水率分别降低4.2%、4.84%、2.34%,十字板强度分别提高32%、75%、61.1%。试验结果表明:真空预压后期通过叠加电渗法,可在含水率降幅小于5%的情况下,实现十字板强度较大幅度的提升,特别是对于原先强度较低,单纯真空预压法加固困难的深层土体,强度提升了61%~75%,具有较好的加固效果。
