浅埋暗挖隧道施工引起的地表沉降分桁与对策

分析了隧道施工地表沉降机理，对地表沉降的大小和分布进行了阐述，并从施工工法、施工顺序优化、辅助工法等方面对控制地表变形的施工措施进行了论述，以确保控制地面沉降达到要求。     

盾构衬砌整环破坏机理研究

以某盾构衬砌整环原型试验作为研究对象,利用提出的接头和管片破坏指数对盾构衬砌环的破坏机理进行了研究,研究表明：①接头破坏指数和管片破坏指数以及开裂弯矩等指标可以对盾构衬砌的实际受力状态进行追踪,可以阐述、解释盾构衬砌环的破坏机理;②对于本文所依据的盾构原型试验而言,盾构衬砌环破坏历程是由接头开始开裂、管片开始开裂、首个管片塑性铰形成、接头开始屈服（接头开始丧失承载力）、多个管片塑性铰形成、整环承载力丧失等阶段构成;③多个塑性铰的形成是导致盾构环承载力丧失的直接原因,塑性铰开始位置、发展顺序取决于关键截面及其排序情况。     

穿越地表建筑物浅埋隧道开挖引起的地表沉降

采用解析法研究穿越地表建筑物浅埋隧道开挖对地表沉降的影响,推导出了穿越地表建筑物浅埋隧道施工引起的地表沉降公式,依托广州地铁五号线右线区庄区间隧道穿越地表建筑物工程实例,验证了此方法的可行性,可为类似穿越已有建筑物隧道工程提供一定指导。     

隧道衬砌开裂机理研究现状

介绍了隧道衬砌裂缝的类型与特点,从外力作用、材质、施工、设计等方面分析了裂缝产生的原因,阐述了关于隧道衬砌裂缝的试验与理论研究现状,并指出只有将现场监测、室内试验与理论分析有机地结合,才能深入了解隧道衬砌开裂机理。     

基于时空关系的盾构开挖地表沉降规律

基于武汉地铁四号线某区间隧道盾构开挖引起的地表沉降数据分析,考虑地表沉降的时空关系,将地表沉降划分为无影响阶段、前期沉降阶段、通过阶段、盾尾空隙沉降阶段、工后沉降阶段,并给出了各个阶段的大致范围及其地表沉降占总沉降的比值。通过对Mindlin解引入时间参数,针对不同阶段地表沉降影响因素进行分析,在前影响距离范围内,盾构机与土体的摩擦力和地层损失对地表沉降的影响占优,在后影响距离范围内,地层损失对地表沉降起到了绝对的控制作用,前期沉降阶段的土层隆起与正面附加推力、摩擦力有关,而正面附加推力、摩擦力和注浆压力导致了工后沉降阶段的土体回弹,由此获得了实时地表沉降预测的理论公式。研究结果表明:理论预测值与实测值能较好的吻合,该公式能够较为准确地实时预测地表沉降。     

The importance of longitudinal stress effects on the static conditions of the final lining of a tunnel

The effects of stresses acting in the longitudinal direction (parallel to the tunnel axis) in certain cases take on an important role in the definition of the static conditions of the final lining, and if they are not foreseen, can lead to instabilities that often require difficult and expensive repair interventions. The case in which the final lining shows a marked irregularity of thickness along the tunnel axis is typical, for example, when the preliminary supports are of a truncated-cone type placed in advancement ahead of the excavation face. The produced anomalous stresses are basically due to the difference in transverse stiffness (and, therefore, in the radial displacements) between the adjoining lining sections. A simple calculation procedure has been set up in this work which permits the estimation of the three-dimensional stress state inside the concrete in the presence of a thickness anomaly and of a homogeneous and uniform radial load at the lining extrados. The approach followed is able to furnish the trend of the safety factor regarding the rupture of concrete, in function of the distance from the thickness anomaly, in such a way as to be able to design the lining thickness and any necessary steel reinforcements.     

Physical model simulation of rock-support interaction for the tunnel in squeezing ground

The existence of squeezing ground conditions can lead to significant challenges in designing an adequate support system for tunnels.Numerous empirical,observational and analytical methods have been suggested over the years to design support systems in squeezing ground conditions,but all of them have some limitations.In this study,a novel experimental setup having physical model for simulating the tunnel boring machine(TBM)excavation and support installation process in squeezing clay-rich rocks is developed.The observations are made to understand better the interaction between the support and the squeezing ground.The physical model included a large true-triaxial cell,a miniature TBM,laboratoryprepared synthetic test specimen with properties similar to natural mudstone,and an instrumented cylindrical aluminum support system.Experiments were conducted at realistic in situ stress levels to study the time-dependent three-dimensional tunnel support convergence.The tunnel was excavated using the miniature TBM in the cubical rock specimen loaded in the true-triaxial cell,after which the support was installed.The confining stress was then increased in stages to values greater than the rock’s unconfined compressive strength.A model for the time-dependent longitudinal displacement profile(LDP)for the supported tunnel was proposed using the tunnel convergence measurements at different times and stress levels.The LDP formulation was then compared with the unsupported model to calculate the squeezing amount carried by the support.The increase in thrust in the support was backcalculated from an analytical solution with the assumption of linear elastic support.Based on the test results and case studies,a recommendation to optimize the support requirement for tunnels in squeezing ground is proposed.     

Analytical computation of support characteristic curve for circumferential yielding lining in tunnel design

Circumferential yielding lining is able to tolerate controlled displacements without failure,which has been proven to be an effective solution to large deformation problem in squeezing tunnels.However,up to now,there has not been a well-established design method for it.This paper aims to present a detailed analytical computation of support characteristic curve(SCC)for circumferential yielding lining,which is a significant aspect of the implementation of convergence-confinement method(CCM)in tunnel support design.Circumferential yielding lining consists of segmental shotcrete linings and highly deformable elements,and its superior performance mainly depends on the mechanical characteristic of highly deformable element.The deformation behavior of highly deformable element is firstly investigated.Its whole deforming process can be divided into three stages including elastic,yielding and compaction stages.Especially in the compaction stage of highly deformable element,a nonlinear stress-strain relationship can be observed.For mathematical convenience,the stress-strain curve in this period is processed as several linear sub-curves.Then,the reasons for closure of circumferential yielding lining in different stages are explained,and the corresponding accurate equations required for constructing the SCC are provided.Furthermore,this paper carries out two case studies illustrating the application of all equations needed to construct the SCC for circumferential yielding lining,where the reliability and feasibility of theoretical derivation are also well verified.Finally,this paper discusses the sensitivity of sub-division in element compaction stage and the influence of element length on SCC.The outcome of this paper could be used in the design of proper circumferential yielding lining.     

Deformation and mechanical characteristics of tunnel lining in tunnel intersection between subway station tunnel and construction tunnel

Deformations and stress distributions in tunnel intersection areas are more complicated than those in common tunnels. The literature on deformations and stress distributions in tunnel intersections, in which the intersecting tunnel is in a different section, is limited. The Shangxinjie subway station in Chongqing, China, was selected to investigate the deformation, stress and plastic zone responses of a tunnel intersection using numerical simulations. Based on the numerical results, the scopes of influence with respect to the deformation, stresses and possible failure modes of the tunnel lining were further studied. The numerical results show that the deformation in a section close to the tunnel intersection was larger than the deformations in distant sections. Compared with the common section, the crown settlement reached the maximum value at the tunnel intersection, and the maximum rate of increase was approximately 28%. The range of the plastic zone at the tunnel intersection was much larger than that in the other areas, and it was mainly located in the side wall and tunnel crown. In the longitudinal direction, the lengths of the scopes of influence were 2.4 B and 1.6 B with respect to the deformation and stress, respectively. The magnitudes of the internal forces in the longitudinal and circumferential directions were almost equal. The bending moments of the tunnel lining within 135° and 225° significantly changed, but the axial force decreased dramatically. Tensile and compressive failures may occur at the tunnel intersection and in a section 5 m away. Locally thickening the supporting structures is suggested to improve the stability of the tunnel.     

防止高层建筑主楼与裙房基础不均匀沉降措施

对于高层建筑主楼与裙房高差悬殊,上部结构荷载分布很不均匀,导致基础发生过大的不均匀沉降,从设置沉降缝、沉降后浇带、整体基础方面进行了论述,从而控制过大不均匀沉降的发生,避免房屋墙体开裂,结构整体或局部倾斜甚至倒塌情况的出现。     

The study of seepage forces acting on the tunnel lining and tunnel face in shallow tunnels

In this paper, the seepage force problems arising from the flow of groundwater into a tunnel were studied. Firstly, the effect of seepage forces acting on the tunnel lining was studied for the case of shallow drainage-type tunnels and these results were compared with the lining stresses developed for waterproof-type tunnels. This model was then reviewed through a comparison with an actual case study of the Seoul Subway Line No. 5. Secondly, the effect of seepage forces on the tunnel face stability was studied. In this study, two factors were considered simultaneously. The first factor considered was the effective stresses acting on the tunnel face, calculated from the upper bound solution of limit analysis and the other factor was the seepage forces, calculated from a numerical analysis under a steady-state of groundwater flow conditions. Consequently, reasonable design concepts applicable to the design of tunnel lining and to the evaluation of the support pressure required for maintaining the stability of the tunnel face were suggested for underwater tunnels.     

公路隧道衬砌裂纹扩展机理

公路隧道衬砌裂缝作为公路隧道的主要病害,其问题日益突出,尤其是带裂纹工作衬砌的等级评价略显不足。为研究公路隧道带裂缝二次衬砌在受荷载作用下裂纹扩展规律,用离散元PFC软件对衬砌裂纹扩展规律进行数值模拟研究,揭示隧道衬砌中裂纹开裂的灾演机理,根据衬砌开裂状态进行病理灾害分析,并建立了相应的预测模型。衬砌的整体安全性受预置裂纹的影响,预置裂纹处往往是衬砌中较危险的位置;预置裂纹的深度对裂纹贯通时间有较大影响,随着预置裂纹深度的增加,预置裂纹贯通衬砌的时间逐渐减小;预置裂纹的深度对裂纹张开度的变化有较大影响,随着预置裂纹深度的增加,预置裂纹张开度逐渐增大,并在贯通衬砌时有明显的突变,这样便于确定衬砌治理时机。     

圆形隧道装配式衬砌接头刚度模型研究

接头刚度Kθ是装配式衬砌结构设计的一个重要参数。目前 ,Kθ的取值尚无现成的公式或图表可循 ,一般是根据接头受力试验确定。本文通过试验建立了接头的力学模型 ,该模型将接头衬垫和连接螺栓抽象成弹簧 ,根据衬垫材料的压缩回弹曲线 ,建立了接头受力和变形的非线性方程式。为了避免应用中求解非线性方程组 ,本文推导了接头刚度的简化计算公式。应用所建立的模型可以求解接头转角、接缝张开量、螺栓拉力等参数 ,通过与接头受力试验实测数据对比 ,证明计算值和实测值是吻合的。文中还应用模型对各种因素对接头刚度的影响规律进行了模拟 ,所得结果是合理的。     

最近邻抽样回归模型在纵向地表沉降预测中的应用

针对传统方法在盾构法施工地表沉降预测中过于形式化和数学化的缺点,本文引入最近邻抽样回归模型(NNBR)。将盾构法施工引起地表沉降的因素分为三类:结构类、地质类和施工参数类,结合NNBR模型的计算特点对不同种类的因素采取不同的处理措施:结构类因素视为常量;按照能否形成免压拱将地质土层分为两类,计算距离系数时同类地层中的地质类因素视为常量;施工参数类因素的影响近似用隧道埋深和盾构平均掘进速度来衡量。由于NNBR模型对纵向地表沉降进行预测时可忽略常量因素,从而大大简化诸多次要因素对预测结果的影响,最终可以隧道埋深和盾构平均掘进速度为预测因子来预测纵向地表沉降。结合工程实例,证明预测因子选择的合理性以及NNBR模型在纵向地表沉降预测中的实用性。     

钢筋混凝土框架变梁中节点破坏机理研究

根据10个梁高不等的钢筋混凝土框架中节点试件在低周反复荷载作用下的试验结果,重点分析了该类非常规节点的破坏过程和破坏特点。试验结果表明：变梁中节点试件通裂阶段与极限阶段非常接近,试件达到通裂阶段后,剪切变形急剧增大,强度、刚度退化显著加剧,试件破坏时节点区斜裂缝主要集中在大核心区(柱与大梁构成的区域)平行对角线方向的2/3范围内,按常规节点设计的变梁中节点不能满足刚性节点的要求。在斜压杆机构和桁架机构的基础上,结合该类非常规节点核心区两侧梁高不等的特性提出变梁中节点的等效斜压杆破坏机理,并应用等效斜压杆机理对变梁中节点的受剪性能进行理论分析,计算得到的节点区剪应力-剪切变形曲线与试验结果吻合良好。     

盾构施工不同中线问距对地表沉降的影响

以成都地铁一号线桐梓林站至火车南站区间段为背景,采用FLAC3D数值模拟的手段,对成都市特有地质条件下双线盾构隧道施工不同中线间距引起的地表沉降进行了研究,得出了一些具有指导意义的结论。     

Numerical parametric study on stability and deformation of tunnel face reinforced with face bolts

Although face bolting has been used as a stabilisation technique in open-face tunnelling for decades, there is still a lack of systematic ways for determining the optimum parameters of face bolts. To optimise design for face bolting in soft ground, it is necessary to understand the influences of each parameter associated with face bolting on ground response. In this note, five series of numerical parametric studies are carried out, to investigate the effects of length, density, reinforcement area, axial rigidity of face bolts and strength of soil on tunnel face stability and deformation in soft rock. Based on the ground condition, geometries of tunnel and configurations of face bolts simulated, the optimum length, density and axial rigidity of face bolts are found to be 0.6H (H = height of tunnel), 1 bolt/m² and 195 MN, respectively. The optimum axial rigidity of face bolt appears to be independent of the bolt density. The computed results also reveal that it is more effective to reduce face deformation by installing face bolts around the tunnel periphery, than installing them near the central area of the tunnel face.     

地基沉降量计算方法分析研究

对目前采用的最终沉降量计算方法进行了分析比较，通过工程实例，验证了割线模量法计算最终沉降量的可行性，提出了宜采用割线模量法估计最终沉降置的建议。     

基坑开挖引起的地面沉降估算

基于4种不同的围护结构基本变形模式,对上海地区典型土层分布状况进行了多种工况下的基坑开挖数值模拟计算。计算结果发现,在4种不同的围护结构基本变形模式下,墙后最大沉降量和基坑围护结构最大侧向位移之间呈线性关系,墙后的地面沉降曲线呈明显的正态函数分布,并可拟合得到其正态函数曲线表达式。在此基础上,提出了基于围护结构变形模式的地面沉降估算方法。工程实例验证表明,该方法具有一定的实用性和可靠性,不失为一种方便实用的估算基坑开挖引起墙后地面沉降的方法。     

隧道施工引起地层移动及变形分析

简述了城市隧道施工的有关要求,探讨了地表变形与沉降对建筑物的影响,采用数值模拟和理论分析相结合对地表沉降进行了定性和定量分析,以确保地下工程建设质量。