双圆盾构隧道土体地表沉降特性

介绍了双圆盾构隧道这种新型隧道形式,与圆形盾构隧道相比,双圆盾构隧道具有占用地下空间小、施工效率高、掘削土量少等优点,但双圆盾构隧道引起的土体位移相对较大,影响范围也比较广。基于双圆盾构隧道的施工特点,通过计算圆形盾构的土体地表沉降,运用土体位移叠加法,研究了双圆盾构隧道引起的土体地表沉降的特性,建立了双圆盾构隧道直径、埋深和地层损失等因素与土体地表沉降的关系。结果表明:双圆盾构隧道的地表沉降槽的形态与圆形盾构隧道相似;双圆盾构隧道的地表沉降量大,影响范围广;双圆盾构隧道的地表沉降与埋深和直径之比有关。     

双圆盾构同步注浆系统的运用与地面沉降控制技术

在上海轨道交通2号线8A标双圆盾构隧道施工中,通过采用置换工法,有效的解决了盾构机背土现象,使得双圆盾构在软土地层施工过程中的地表沉降得到有效控制。     

富水地层盾构施工引起的沉降实测分析

盾构隧道开挖受地质影响较大,不同地区不同土层开挖会导致其盾构施工引起的地层损失率η和地表沉降槽宽度系数K也不同,导致其施工经验难以完全借鉴.文中以杭州地铁8号线一期SG8-2标中文桥区间风井-桥头堡站盾构区间为工程背景,对该地区的盾构施工引起的实测数据进行分析,得到该地区的地层损失率η和地表沉降槽宽度系数K;并对盾构施...     

上软下硬地层下盾构法施工的Peck预测公式修正

以青岛地铁一号线某区间地表沉降实测数据为基础,采用回归分析方法并引入最大地表沉降修正系数、沉降槽宽度修正系数对Peck预测公式进行修正,得出适用于该区间上软下硬地层盾构法施工的Peck预测公式,研究表明:对该区间进行回归分析得到的沉降规律与实测数据较吻合,说明采用线性回归方法能较好预测该区间盾构隧道施工引起的地表沉降规律,当α在0.2～0.5区间,β在0.9～1.3区间时,所得到的修正Peck预测公式可以较准确预测该区间盾构隧道施工引起的地表沉降。     

单曲线隧道地表不均匀沉降计算方法

以某地铁区间隧道盾构施工项目为背景,对盾构推进过程中产生的地表沉降及各种影响因素进行了深入研究,得出了一套适合于隧道曲线段盾构施工地表沉降的预测及计算方法。     

双圆盾构隧道施工土体扰动特性及实测分析

以上海轨道交通6^#线双圆盾构区间隧道工程为背景，通过动态监测双圆盾构施工引起土体分层沉降、水平位移、孔隙水压变化、海鸥块背土挤土现象，总结归纳双圆盾构掘进土体扰动的基本规律，提出了双圆盾构施工土体扰动的区域性、时段性特征。     

盾构机二次掘进对地表沉降的影响

以北京地铁8号线15标段六营门站—五福堂站盾构区间作为研究项目,通过对区间隧道盾构开挖因故暂停后再次掘进所引起的地表沉降监测数据进行统计分析,得出土体变形位移和地表沉降的变化规律,再根据变形监测的数据以及变形发展趋势采取了有效工法和措施控制施工进度,确保了工程的施工安全,对今后隧道盾构法施工提供了一定的借鉴。     

广州地铁四号线车黄区间盾构施工参数优化与地表沉降控制

为提高盾构隧道施工技术水平,控制地表沉降,本文以广州地铁四号线北延段车陂至南村站区间盾构隧道工程为背景,分析了盾构隧道引起地表沉降的主要施工参数并进行了相关的优化,通过分析地表沉降的时间规律,研究提出了控制盾构掌子面、盾体通过和盾尾脱出时三个阶段地表沉降的可行技术工艺。     

双圆盾构掘进中的地面沉降控制技术

采用双圆盾构施工地铁隧道是解决地下工程空间利用的有效途径。介绍了上海市轨道交通10号线3标同济大学站—大连路站—邮电新村站区间隧道采用双圆盾构施工的方案。重点叙述了引起地面沉降的原因及控制地面沉降的措施。通过工程实际,测得双圆盾构施工中累计的最大沉降量为49mm。     

重叠隧道施工数值分析

以佛山地铁莲塘-张槎盾构区间重叠隧道为工程依托,运用MIDAS/GTS有限元程序模拟盾构开挖的全过程,采用不加固和地面加固两种施工工况,分析不同工况下重叠隧道施工对地表沉降和盾构管片内力影响,结果表明:地层受盾构施工的影响范围都逐步扩展,地表沉降曲线符合Peck沉降槽规律。地面加固后地表最大沉降量约为18.8mm,未加固地表最大沉降量约为102.3mm。洞内注浆加固后能够减小盾构管片内力。     

Soil deformation induced by Double-O-Tube shield tunneling with rolling based on stochastic medium theory

The prediction of soil deformation during tunneling is very difficult for Double-O-Tube (DOT) shield tunnel construction, especially for the shield rolling. According to the characteristics of DOT shield tunneling and rolling, a calculation model of soil deformation due to tunneling-induced ground loss was established. Based on the stochastic medium theory, the theoretical solutions of soil deformations considering the rolling of DOT shield machine were derived by polar coordinate transformation and multi-subdomain integral method. The predicted surface settlement from the proposed solution is better agreement with the observed data than those obtained by the two previous methods (namely the equivalent excavated-area method (EAM) and the simple superstition method (SM)). In addition, only ground surface settlement can be estimated under no rolling of DOT shield machine using the two previous methods, while this proposed solution owns great progress in solving the subsoil deformation and the influences of rolling. In order to further study the influence of DOT shield rolling angle on soil deformation under different engineering conditions, the parameter sensitivity analyses regarding the tunnel depth h, the ground loss parameter ɛ and the influence zone angle β₀ were extensionally discussed.     

Double-O-tube shield tunneling technology in the Shanghai Rail Transit Project

Double-O-tube (DOT) shield tunneling technology characteristics and research are described. Taking the construction of the DOT shield tunnel in the Shanghai Rail Transit Project as a case study, the sophisticated techniques and knowledge applied to soft soil DOT shield tunneling are summarized, creating a firm foundation for the broad application of DOT shield tunneling technology in the future.     

Lessons learnt from unusual ground settlement during Double-O-Tube tunnelling in soft ground

The DOT (Double-O-Tube) tunnelling method has been adopted in the construction of various types of tunnels in soft ground both in Japan and in China. Recently, an unexpected ground surface settlement of approximately 0.8 m was observed in a DOT construction site in Shanghai, China. The backfill grouting injection rate had to be increased by up to 500% to control the settlement. In order to find out the reasons for the large settlement, and to reduce it to an acceptable level, in-situ monitoring, including surface settlement and subsurface settlement, was undertaken to obtain the change in ground deformation during DOT machine driving. It was found that the conventional settlement control methods, such as adjusting the earth pressure balance on the cutter face, and simultaneous backfill grouting at a normally acceptable injection rate, could not reduce the large settlement. It was also noticed that the settlement started as the DOT machine was passing, as well as after the tail had passed through. Subsequent field investigations found cement accumulation attaching to the skin plate. This was due to improper backfill grouting at the early construction stage, and the concave shape of the DOT machine. The mechanism for large settlements due to improper immediate backfill grouting was analysed. After taking countermeasures, the ground settlement was reduced to approximately 0.02 m.     

双圆隧道盾构推进对周围环境影响的现场监测

结合中国第一条双圆隧道工程施工,对双圆隧道盾构推进对周围环境影响的现场监测方法进行了论述.文章以双圆盾构隧道区间施工为实例给出了双圆盾构推进过程中周围土体的变形、土压力、水压力变化的监测方法与测点布置方案,据此监测方案,可以详细监测与分析盾构推进过程中周围土体的地表变形、深层土体变形及土体中的土压力、水压力的变化,从而揭示盾构推进对周围的土体环境的扰动影响规律.     

基于地层损失的盾构隧道地面沉降控制

依据盾构推进各阶段特征,分析了盾构推进引发地面沉降的机理。基于地层损失,建立了盾构隧道地面沉降控制体系。该体系综合了土层特性和盾构隧道设计参数,通过设定地层损失率,利用经验公式对隧道纵横两个方向的地面沉降做出预测,基于沉降控制指标反算需要控制的地层损失率,用于控制沉降;利用数值模拟分析隧道施工过程,基于地面沉降三维曲面,分析地层损失及施工控制参数对地面沉降的影响。对比分析设定地层损失率计算结果与现场监测数据,建立地面沉降—地层损失率—施工参数之间的联系,通过施工参数控制实现地面沉降的控制。     

富水地层中重叠隧道施工引起土体变形研究

重叠隧道施工易产生隧道结构不稳定和地层变形等问题。重叠隧道富水地层施工时,土层开挖应力释放和地下水渗流共同作用使得地层和隧道变形问题显得更加突出,增加了施工难度。以深圳地铁5号线重叠隧道为背景,采用数值方法研究了开挖应力释放和渗流作用在重叠隧道施工不同阶段对隧道结构和土层变形的影响,得到富水地层重叠隧道施工土层变形规律,同时提出了控制地层变形措施。重叠隧道下洞施工时,采用设置超前注浆支护能有效控制开挖应力释放引起拱顶沉降,开挖完成后隧道拱顶在渗流作用下沉降稳定,而隧道上覆土层因失水固结产生较大工后沉降,同时地表沉降槽深度和半径在渗流作用下不断增大;为避免下洞隧道在渗流作用引起上洞隧道整体沉降,上洞在下洞施工引起土体变形稳定后进行施工。上洞开挖应力释放引起较大地层沉降,开挖应力释放引起较大地层沉降,渗流因素引起地层工后变形较小,地表沉降槽深度迅速增大而影响半径保持稳定。     

基于能量法的双圆盾构施工引起管线沉降计算

引入隧道与开挖面的相对位置系数α,研究双圆盾构施工在不同工况下引起的深层土体沉降计算公式,以土体沉降计算公式为基础建立能量变分方程,得到双圆盾构施工引起地下管线沉降的计算方法。通过算例对比分析4种典型工况下管线沉降的分布规律,验证公式推导结果正确性,并进一步分析了管线埋深和土体损失率等因素对管线最大沉降的影响规律。研究结果表明:本文方法计算3种正常工况下的管线沉降曲线满足正态分布,旋转工况下管线沉降分布不均匀,最大沉降向下沉隧道侧偏移,另一侧的沉降量则相对较小;土体损失率对管线的沉降有较大影响,而管线埋深对管线沉降的影响则相对较小。     

Ground movement induced by triple stacked tunneling with different construction sequences

This study tried to explore the ground movement induced by triple stacked tunneling(TST) with different construction sequences. A case study in Tianjin, China was used to investigate the ground movement during the TST(upper tunneling(UT)). For this, a modified Peck formula was proposed to predict the surface settlement induced by TST. Next, three sets of finite element analyses(FEA) were used to compare the effects of construction sequences(i.e. UT, middle tunneling(MT), and lower tunneling(LT))...     

黏土地层盾构掘进速度对地表沉降影响研究

对盾构掘进速度的控制是盾构施工控制的重要环节,但针对盾构掘进速度与地表沉降关系的研究较少,文章以常州地铁2号线盾构区间施工为背景,分析了常州黏土地层下盾构掘进速度对表沉降的影响特点。通过对其地表监测数据的整理分析,结合盾构掘进施工日志,提出一种可对同步注浆、二次注浆、土舱压力、盾构掘进速度等进行定量分析的数值模拟方法,设计模拟工况对盾构全过程进行模拟研究,得到STEP计算步数与盾构掘进速度之间的对应关系,建立常州黏土地层下盾构掘进施工的掘进速度造成地表沉降预测曲线。研究结果表明：掘进速度较快时其造成的地表沉降更小,且当掘进速度在20～50mm/min时利用数值模拟得到黏土地层下掘进速度v—地表沉降h关系的预测曲线：h=6.5/{1+86.2［(v-19.5)/27842.7］0.464},其预测效果较好。