【作者】 郭玉海；

【导师】 王梦恕；

【作者基本信息】 北京交通大学 ， 地下工程， 2014， 博士

【摘要】 论文依托北京地铁14号线10.22m大直径土压平衡盾构长距离掘进控制工程实例,借鉴已有盾构控制技术进行快速施工创新,采用理论分析、数值计算、紧密结合现场测试和室内试验相结合的综合研究方法,提出了大直径盾构机快速掘进及管片配制安装产生地表变形沉降规律及关键控制技术,实现了月掘进平均492m,最快641m/月的最高水平。研究将有利于促进北京地铁从“双洞双线”转向“单洞双线”线路敷设方式的转变和建设方法的革新,意义重大。主要关键技术研究内容有六项。一、大盾构引起的地表变形规律和分布特征(1)地表沉降槽曲线符合Peck曲线(Gauss公式),地表沉降最大沉降大致在12.0mm到36.4mm之间；拱顶覆粘性土时,最大沉降值在12.0mm到25.9mm之间；拱顶覆砂性土时,最大沉降大致在20.4mm到36.4mm之间。(2)地表沉降槽宽度系数i与隧道埋深z大致成正比关系,隧道拱顶为粘性土时,比例系数k约为4.7,地层损失率平均为0.40%；拱顶为砂性土时,比例系数k约为3.5,地层损失率平均为0.45%。总体看来,地层损失率大致在0.31-1.04%之间。(3)地层损失Vs与浆液注入率大致成负指数关系：地表沉降最大值和沉降槽宽度均随注浆量、土仓压力的增大而减小；数据表明,浆液注入率控制在145-175%之间时,地表沉降控制较好。二、地表变形预测方法(1)本文建立的基于LS-SVM的地表沉降最大值以及地表沉降槽宽度预测模型可以考虑盾构法关键技术参数以及隧道埋深、拱顶覆土力学特性的影响,弥补了传统预测方法在此方面的不足,更贴合工程实际,便于工程推广应用。(2)本文计算分析表明,相比线性函数和多项式核函数,RBF核函数具有较强的统计学习及更高的泛化推广能力,尤其适应地表沉降最大值和沉降槽宽度的建模分析。(3)基于LS-SVM建模分析,可以写出地表最大沉降及沉降槽宽度与相关影响因素的显式表达,从而可以更加清晰认识相关要素与地表沉降关键特征参数的作用机理。三、大盾构始发关键技术(1)大盾构成功始发的实践证明,本工程主要依据工程经验选取旋喷方法进行端头加固可行的,反力架结构推力荷载考虑2.7的安全系数是偏于安全的,通过负环管片拼装前后的控制措施保证负环管片的成型质量以及在盾构台车轨道上方铺设钢板解决了台车轮组小半径曲线转弯问题的做法是合理的,对类似工程有较好参考价值。(2)针对大直径盾构沿350m曲线半径和27‰线路纵坡的困难始发条件,文中提出的始发反力架和基座安装精度指标是合理的,满足了始发要求。(3)理论建模计算分析表明,大直径盾构始发过程中其自重与托垫间的摩擦力产生的阻滞力矩不能满足刀盘旋转切削的掘进要求,必须在其托垫和盾构壳体之间采取抗扭矩措施。四、渣土改良技术和同步注浆浆液配比(1)注入浓度为5%泡沫和浓度为8%泥浆的渣土改良方案以及针对大直径盾构渣土搅拌进行的泥浆、泡沫系统设置、管路独立布置、添加口的数量和位置的设计,特别是渣土主动搅拌装置的配备是成功的,满足了生产需要。(2)实践表明,同步注浆采用双液浆方案,浆液配比为水：水泥：泥浆：缓凝剂=1：1：0.3：0.013,以及每环浆液的注入量为14.1-15.3m3／环的做法是成功的。五、隧道内部会车浮放式道场系统(1)突破传统固定式运输车场的限制,建立一种可适应不同坡度并可在曲线段快速敷设的可移动式隧道内双道岔四轨会车浮放式道场,是实现长大隧道高效水平运输的技术关键,有助于发挥盾构技术安全、迅速和环保的优点。(2)本文建立的车场位置和运输距离模型是本工程在距始发位置1km和1.7km处设置会车浮放式道场的理论基础,对于其他行业长大隧道的建设也有重要的参考价值。六、近接施工安全控制技术(1)构建以合理盾构掘进参数选择、地层渣土改良方案优化和综合注浆控制等为核心技术的主动控制技术体系,并依据环境条件复杂状况,配合实施邻近环境条件和建(构)筑物的现状检测、施工过程的数值化仿真以及必须的地层(和)或邻近建(构)物加固措施,依然是复杂环境条件下直径10.22m大盾构地层微扰动控制技术的核心。(2)对于大直径盾构在小半径曲线上的施工,主动“铰接”功能的配备和沿曲线长度范围内的合理操作顺序至关重要,这是大盾构姿态控制和减少对周围地层扰动的关键技术措施之一。而完善的信息化施工和监测数据的及时反馈分析,是有效指导大盾构掘进施工过程控制及盾尾同步注浆和二次补浆施工,严格控制地层沉降的保证。更多还原

【Abstract】 Based on the long-distance tunneling practice of a10.22-m diameter earth pressure balance (EPB) shield on Beijing subway Line14, and making good use of the existing shield tunneling technologies and experiences, the ground surface movement law and corresponding control technologies of rapid tunneling of the big diameter shield was studied by means of theoretical analysis, numerical calculations, in-situ measurements and indoor tests. The highest level attained of the big diameter EPB shield tunneling is641m per month and on average the driving length is492m per month. The finding presented are of great significance and helpful to the innovation of line layout and construction method of Beijing subway from the traditional "double-tube-double-line" to the "single-tube-double-line". The six main technologies involved are as follows.1) The big diameter shield tunneling induced ground surface movement(1) The ground surface settlement trough conforms to the Peck curve (Gauss curve). The maximum settlement of ground surface is about12.0-36.4mm, which is12.0-25.9mm in case of clayey roof soil, and20.4-36.4mm in case of sandy roof soil.(2) The ground surface settlement trough width coefficient is proportional to the tunnel depth, and the coefficient of proportionality k is about4.7and the ground loss ratio0.40%on average in case of the clayey roof soil; and the coefficient k is about3.5and the ground loss ratio0.45%on average in case of the sandy roof soil. Overall the ground loss ratio is around0.31-1.04%.(3) There approximately exists the expositional relation between the ground loss Vs and the grout injection ratio; the ground surface maximum settlement and the settlement trough width decrease with the increase of the grout injection amount and the earth chamber pressure field observations show the grout injection ratio of145-175%attains a good control of the ground surface settlement.2) The ground surface movement prediction method(1) Based on the least square support vector machine (LS-SVM), the model was set up to predict the ground surface maximum settlement and the ground surface settlement trough width. Different from the traditional prediction methods the LS-SVM model, convenient for engineering applications, can take into account the effects of the crucial technical parameters of shield tunneling, the tunnel depth and mechanical properties of the roof soil on ground surface settlement.(2) Calculation results show the RBF kernel possesses the higher statistical learning and generalization ability in comparison with the linear and the polynomial kernels, and it is especially suitable to the modeling analysis of the ground surface maximum settlement and the settlement trough width.(3) Using the LS-SVM model, the explicit expressions of the ground surface maximum settlement (the settlement trough width) and relevant influence factors can be gotten. Therefore, the action mechanism between the important characteristic parameters of the ground surface settlement and corresponding influence factors can be more clearly displayed.3) The key start technologies of the big diameter shield(1) The successful launch of the big diameter shield shows that using jet grouting to reinforce ground is feasible mainly according to the engineering experiences and the safety factor of2.7for the thrust load of the reaction frame is on the safe side. It is sensible that adopting measures before assembling the partial segments to guarantee the erection quality of the segments, and that laying out steel plates on tracks to allow trolleys turning along the small radius curve. The above ways of doing provide good references for similar engineering projects.(2) The setting installment precisions of the starting reaction frame and the base are reasonable for the difficult launch conditions of the350-m radius curve and the27%o longitudinal slope, which meet the demand of the big diameter shield starting.(3) Theoretical modeling and calculations show the reverse torque from the friction between the shield and the base can’t meet the demand of rotary cutting of the cutter head during the big diameter shield starting, and measures against turning around of the shield body must be taken.4) Technologies of soil conditioning and mix ratio of simultaneous backfilling grouting(1) The schemes and methodologies for soil conditioning and backfilling grouting meet the demand of convenient for engineering applications and are successful, including the soil conditioning plan with foam of5%concentration and slurry of8%concentration, and the equipment of slurry and foam device for mixing the conditioned soil, the separate layout of the pipelines, and the amount and locations of the additive injection ports.(2)The practice shows it is successful that the simultaneous backfilling grouting plan using the two-liquid type grout with mix ratio of water:cement:slurry:retarder=1:1:0.3:0.013, together with the injection amount per ring of14.1-15.3m3.5) In-tunnel movable trolley station system(1) Breaking through the limitations of the traditional fixed stations, a new type of in-tunnel movable double-turnout-four-track station, fitting for different slopes and easy for quick erection and crucial to the higher efficient in-tunnel horizontal transport, was put forward and help realize the advantages of safety, high-speed and environment protection of the big diameter shield tunneling.(2) The models for station locations and transport distance provide the results of station locations of1km and1.7km away from the starting shaft, which give good references for building long and big tunnels of other types.6) Control technologies of adjacent construction(1) The core of small disturbance of the10.22-m diameter shield tunneling centers on the active control system consisting of reasonable selection of shield driving parameters, well prepared plan of soil conditioning, comprehensive grouting and etc., together with performing status detections of nearby surroundings and adjacent structures, numerical simulation of the construction process, and taking necessary measures to reinforce the ground and structures in close proximity, according to complexities of the surrounding conditions.(2) The equipped function of the active articulation and reasonable manipulation of the shield machine is of paramount importance when tunneling along a small radius curve, which is one of the key technologies of the big diameter shield attitude control and of reducing tunneling induced ground disturbance. While perfect information construction and timely feedback of measured data are the guarantee of strict control of ground settlement by means of the simultaneous backfilling grouting and the secondary grout injection through segment holes.更多还原