The Freeze-Sealing Pipe-Roof(FSPR)method,which has been applied for the first time in the Gongbei Tunnel of the Hong Kong-Zhuhai-Macao Bridge,is a new approach of tunnel pre-support that allows flexible adjustment of ...The Freeze-Sealing Pipe-Roof(FSPR)method,which has been applied for the first time in the Gongbei Tunnel of the Hong Kong-Zhuhai-Macao Bridge,is a new approach of tunnel pre-support that allows flexible adjustment of freeze tube arrangement and can be adapted to different environmental conditions.When the FSPR method is used to construct shallow burial submerged tunnels,the frozen wall to hold back groundwater during excavation will be weakened by air and water flows inside and outside the tunnel,and its waterproof performance needs to be further investigated.In this paper,a two-dimensional numerical model of the temperature field considering excavation and moving water boundary is established based on the preliminary design scheme and in-situ conditions and is used to analyze the variation in frozen curtain properties with various active freezing times during excavation.The results show that excavation has a weakening effect on both sides of the frozen wall,with a greater effect on the inner side,and a positive temperature appears in the local area inside the jacked pipe.The concrete fill in the jacked pipe obviously improves the freezing efficiency,and the tunnel excavation after 60 days of active freezing in the interval filling mode can ensure that the frozen soil thickness at the thinnest segment exceeds 2 m,i.e.,the design requirement.In practice,the active freezing time can be extended appropriately to reduce the influence of river water flow above the tunnel.The study serves as a technical reference for the design and implementation of similar projects.展开更多
超大断面隧道(断面面积大于100 m 2)开挖面积大,围岩扰动性强,因此常常需要进行超前支护控制隧道施工安全,管棚注浆加固是一种常见的隧道超前支护方式,其主要通过在隧道围岩上方形成注浆加固圈从而控制围岩应力和变形大小。在进行数值...超大断面隧道(断面面积大于100 m 2)开挖面积大,围岩扰动性强,因此常常需要进行超前支护控制隧道施工安全,管棚注浆加固是一种常见的隧道超前支护方式,其主要通过在隧道围岩上方形成注浆加固圈从而控制围岩应力和变形大小。在进行数值模拟计算过程中,注浆加固圈厚度是计算结果准确的关键。依托渝黔铁路张家山隧道工程,考虑管棚外插角和搭接长度对注浆加固圈厚度的影响,对传统计算公式进行优化,采用FLAC3D对比分析未使用管棚注浆加固和使用管棚注浆加固两种计算工况。结果表明:①优化后的注浆加固圈厚度计算公式与管棚外插角、浆液扩散半径、管棚长度、管棚纵向间距和环向间距5个参数相关,且使用优化后计算公式得到的数值模拟结果与现场监测数据更接近,计算结果更准确;②相较于未使用超前管棚注浆支护,使用超前管棚注浆支护拱顶沉降位移为12.65 mm,减小31.06%;③管棚注浆支护能够降低围岩竖向最大压应力20.72%和最大竖向拉应力44.68%,同时能够降低初期支护结构最大主压应力15.87%和最大主拉应力23.81%;④管棚注浆加固的地表沉降最大值为8.95 mm,较未使用管棚注浆加固减少24.25%;⑤管棚注浆加固效果与浆液扩散半径、管棚外插角和管棚长度呈正相关,与管棚纵向间距和环向间距呈负相关,其中浆液扩散半径影响效果最显著,管棚外插角影响最小。展开更多
基金This research was supported by the National Natural Science Foundation of China(No.52108386)。
文摘The Freeze-Sealing Pipe-Roof(FSPR)method,which has been applied for the first time in the Gongbei Tunnel of the Hong Kong-Zhuhai-Macao Bridge,is a new approach of tunnel pre-support that allows flexible adjustment of freeze tube arrangement and can be adapted to different environmental conditions.When the FSPR method is used to construct shallow burial submerged tunnels,the frozen wall to hold back groundwater during excavation will be weakened by air and water flows inside and outside the tunnel,and its waterproof performance needs to be further investigated.In this paper,a two-dimensional numerical model of the temperature field considering excavation and moving water boundary is established based on the preliminary design scheme and in-situ conditions and is used to analyze the variation in frozen curtain properties with various active freezing times during excavation.The results show that excavation has a weakening effect on both sides of the frozen wall,with a greater effect on the inner side,and a positive temperature appears in the local area inside the jacked pipe.The concrete fill in the jacked pipe obviously improves the freezing efficiency,and the tunnel excavation after 60 days of active freezing in the interval filling mode can ensure that the frozen soil thickness at the thinnest segment exceeds 2 m,i.e.,the design requirement.In practice,the active freezing time can be extended appropriately to reduce the influence of river water flow above the tunnel.The study serves as a technical reference for the design and implementation of similar projects.
文摘超大断面隧道(断面面积大于100 m 2)开挖面积大,围岩扰动性强,因此常常需要进行超前支护控制隧道施工安全,管棚注浆加固是一种常见的隧道超前支护方式,其主要通过在隧道围岩上方形成注浆加固圈从而控制围岩应力和变形大小。在进行数值模拟计算过程中,注浆加固圈厚度是计算结果准确的关键。依托渝黔铁路张家山隧道工程,考虑管棚外插角和搭接长度对注浆加固圈厚度的影响,对传统计算公式进行优化,采用FLAC3D对比分析未使用管棚注浆加固和使用管棚注浆加固两种计算工况。结果表明:①优化后的注浆加固圈厚度计算公式与管棚外插角、浆液扩散半径、管棚长度、管棚纵向间距和环向间距5个参数相关,且使用优化后计算公式得到的数值模拟结果与现场监测数据更接近,计算结果更准确;②相较于未使用超前管棚注浆支护,使用超前管棚注浆支护拱顶沉降位移为12.65 mm,减小31.06%;③管棚注浆支护能够降低围岩竖向最大压应力20.72%和最大竖向拉应力44.68%,同时能够降低初期支护结构最大主压应力15.87%和最大主拉应力23.81%;④管棚注浆加固的地表沉降最大值为8.95 mm,较未使用管棚注浆加固减少24.25%;⑤管棚注浆加固效果与浆液扩散半径、管棚外插角和管棚长度呈正相关,与管棚纵向间距和环向间距呈负相关,其中浆液扩散半径影响效果最显著,管棚外插角影响最小。
