地铁盾构隧道管片防水技术措施探索

本文通过结合某地铁盾构隧道施工实例,针对该隧道管片施工环节,提出采取可行的防水技术措施,从管片安装、管片自防水、环形间隙注浆体作为隧道防水的加强层等措施分别探讨管片防水的实现,旨在能为同类工程提供有价值的参考。     

盾构隧道管片扭转原因分析及应对措施

在盾构法隧道施工中,由于受刀盘扭矩的影响,拼装成型的管片会产生一定角度的扭转,通过北京市南水北调配套南干渠工程盾构施工实例,对部分地段管片扭转产生的原因进行了分析,提出了应对管片扭转的一些措施,对今后类似工程提供一定的借鉴。     

盾构隧道管片纵缝错台的影响分析

采用有限元软件ABAQUS建立存在10mm既有纵缝错台的盾构管片与螺栓的三维非连续-接触计算模型,分析错台对管片的影响,并与现场实测值进行对比分析。研究结果显示：管片错台使错台拼装块与邻近拼装块之间产生附加的接触压力。由于错台发生在管片环中的具体位置不同,轴力值最小增加幅度为101%,最大增加幅度为281%;弯矩值最小增加幅度为78%,最大增加幅度为275%。相对于无既有错台工况,受既有错台影响,盾构管片两侧拱腰的弯矩值均有所减小。采用正常使用极限状态方法计算得出管片在错台附近的最大裂缝宽度为0.21mm。通过模拟计算与现场实测数据可以得出：盾构管片错台会引起局部管片内力增大以及破损,在盾构施工与设计工作中应当引起足够的重视。     

大直径盾构负环管片拆除及隧道换装技术

通过对北京铁路地下直径线2标工程的研究,确定在刀盘改造期间进行负环管片拆除的一系列工作,重点如部分反力架的拆除方法、负环管片的详细拆除方法以及拆除反力架后临时支撑的架设方法,同时就泥水盾构隧道的换装技术进行了叙述,最终在7d之内成功拆除了7环负环管片,节约了工期,保证了后继施工的材料运输速度。     

深部复合地层管片衬砌与可压缩层联合支护技术研究

深埋盾构隧道所受围岩压力主要为围岩挤压型大变形产生的形变压力,其主要特点是变形持续时间长且具有重复性,支护完成后围岩压力仍将持续增大,企图通过增加支护刚度来抑制围岩变形是不现实的,采用让压支护是解决问题的一个方向。同时,深部围岩赋存条件复杂,岩体结构复杂多变,盾构隧道穿越复合地层不可避免。以国内两座大埋深盾构煤矿斜井为背景,采用相似模型试验和有限元数值计算手段,对比分析不同复合地层条件下管片衬砌+可压缩层联合支护时管片衬砌的力学性能。研究结果表明：在模型正确建立且参数取值合理的前提下,有限元数值计算结果可以和相似模型试验结果很好的吻合。均一地层条件下可压缩层可使管片最大弯矩减小12.5%~19.9%,最大轴力减小14.2%。复合地层使管片弯矩量值和分布均产生明显变化,但对管片轴力的影响则不明显,管片弯矩对复合地层抗力更为敏感,而轴力对复合地层抗力不敏感。有可压缩层情况下,复合地层中管片内力分布更加均匀,轴力的变化不明显。复合地层相对厚度对管片最大正弯矩的影响较为稳定,对管片最大负弯矩影响显著,使其产生位置偏向相对较软一侧的地层,且相对厚度越大偏移越明显。\     

盾构管片UHPC加固技术及力学性能分析

针对盾构隧道运行期管片破损问题,提出了利用具有优异的力学性能和耐久性能的超高性能混凝土（UHPC）材料加固管片的方法。建立了UHPC加固通缝拼装管片的三维非线性有限元模型,讨论了加固前后管片力学特性和变形行为,揭示了UHPC加固的承载机理和破坏模式。在此基础上,探讨了不同厚度、配筋率的UHPC加固层对加固效果的影响。研究表明,UHPC加固盾构隧道不仅能有效控制管片变形,提高结构承载力,并且在满足抗裂性能的条件下,顶底相对位移继续发展的容许值可以达到厘米级。该文研究将为隧道管片加固提供新思路。     

复合地层海底隧道盾构岩石控制爆破技术

为解决厦门市地铁3号线五缘湾站-刘五店站海底隧道盾构岩石处理难题和保护该海域的中华白海豚,采用水下深孔爆破预处理风化状岩体(孤石)、基岩的复合地层。结果表明:此施工技术获得较好的岩石破碎效果,不仅提高了盾构掘进效率,还使爆破有害效应得到有效控制,确保了中华白海豚的安全,为今后类似海域环境下盾构岩石处理提供了参考和借鉴。     

复合地层海底隧道盾构岩石控制爆破技术

为解决厦门市地铁3号线五缘湾站-刘五店站海底隧道盾构岩石处理难题和保护该海域的中华白海豚,采用水下深孔爆破预处理风化状岩体(孤石)、基岩的复合地层。结果表明:此施工技术获得较好的岩石破碎效果,不仅提高了盾构掘进效率,还使爆破有害效应得到有效控制,确保了中华白海豚的安全,为今后类似海域环境下盾构岩石处理提供了参考和借鉴。     

氯离子及迷流共同作用下持荷盾构管片钢筋锈层形态

针对盾构隧道结构在服役期间可能出现钢筋锈蚀的问题,考虑杂散电流、氯离子及外部荷载共同作用,建立了电-化-力三场耦合的三维管片数值模型,分析了多因素作用下拱腰部位管片钢筋的锈蚀率变化规律及锈层分布形态。研究表明： 1）靠近管片外侧钢筋的锈蚀率比内侧的大,不同区域的钢筋出现最大锈蚀率的位置与连心线的夹角在0°~52°之间。2）在荷载作用下管片钢筋的锈蚀率与体积应变有关,管片中部的锈蚀率大于两端的锈蚀率。3）在钢筋脱钝情况下,管片钢筋的锈蚀率随阴阳极电势差增大呈线性增加,随氯离子含量增大呈对数增加。4）在三种因素共同作用下管片钢筋的锈层分布呈偏心圆形态,且偏心圆圆心坐标及半径的大小与钢筋不均匀锈蚀系数及最大腐蚀电流密度有关。     

富水砂卵石地层中大直径泥水盾构同步注浆技术

通过统计分析盾构掘进相关技术资料,综合考虑富水砂卵石地层中泥水盾构掘进参数、泥浆参数、盾构姿态、地层变形机理等信息,确定泥水盾构在砂卵石地层中掘进时,同步注浆主要技术参数间的经验公式,指导类似工程施工。     

多晶硅硅棒裂纹产生原因分析及控制方法

对多晶硅还原工艺中硅芯机加工、硅芯清洗、硅芯安装、还原炉气体置换、硅芯沉积生长过程、以及停炉过程等操作环节中硅棒裂纹产生的原因进行了分析,并提出了硅棒裂纹控制方法。     

Correction to the Crack Extension Direction in Numerical Modelling of Mixed Mode Crack Paths

In order to avoid introduction of an error when a local crack growth criterion is used in an incremental crack growth formulation, each straight crack extension would have to be infinitesimal or have its direction corrected. In this paper a new procedure to correct the crack extension direction is proposed in connection with crack growth analyzed by the Dual Boundary Element Method (DBEM). The proposed correction procedure and a reference correction procedure already described in the literature are evaluated by solving two different computational crack growth examples. In the two examples it is found that analyses of the crack paths performed with the proposed crack correction procedure using big increments of crack extension are in excellent agreement with analyses of the crack paths performed by using very small increments of crack extension. Furthermore, it is shown that the reference correction procedure has a tendency to overcorrect the crack growth direction if the stop criterion for the iterative correction procedure is not calibrated in each new crack growth analysis.     

Typical Underwater Tunnels in the Mainland of China and Related Tunneling Technologies

In the past decades, many underwater tunnels have been constructed in the mainland of China, and great progress has been made in related tunneling technologies. This paper presents the history and state of the art of underwater tunnels in the mainland of China in terms of shield-bored tunnels, drill-and-blast tunnels, and immersed tunnels. Typical underwater tunnels of these types in the mainland of China are described, along with innovative technologies regarding comprehensive geological prediction, grouting-based consolidation, the design and construction of large cross-sectional tunnels with shallow cover in weak strata, cutting tool replacement under limited drainage and reduced pressure conditions, the detection and treatment of boulders, the construction of underwater tunnels in areas with high seismic intensity, and the treatment of serious sedimentation in a foundation channel of immersed tunnels. Some suggestions are made regarding the three potential great strait-crossing tunnels—the Qiongzhou Strait-Crossing Tunnel, Bohai Strait-Crossing Tunnel, and Taiwan Strait-Crossing Tunnel—and issues related to these great strait-crossing tunnels that need further study are proposed.     

岩石爆破裂纹的起裂,扩展,分岔与止裂

为研究断裂控制爆破,有效地控制裂纹的发生位置,传播方向,开裂长度,本文总结和探讨爆破岩石纹起裂,扩展,分岔和止裂的规律,并用裂力学研究其作用机制。     

Ultrasonic Self-Focusing on the Edge of a Surface-Breaking Crack: Experiment and Modeling

An adaptive time-delay self-focusing technique has been used to focus ultrasound on the edge (tip) of a surface-breaking crack emanating from the opposite side of a plate. The diffraction of the focused signal has been measured with the array. Simulation of the self-focusing process and the diffraction by the crack edge has been carried out to obtain numerical results for the edge diffraction. Ray tracing has been used to determine the incident wave field in the plate. Comparisons between the numerical results and the measured data show good agreement. The results have been used to determine the depth of the crack.     

Crack propagation from a pre-existing flaw at a notch root – II: Detailed form of the stress intensity factors at the initial crack tip and conclusion.

This paper pursues the study of crack kinking from a pre-existing crack emanating from some notch root. It was shown in Part I that the stress intensity factors at the tip of the small initial crack are given by universal (that is, applicable in all situations, whatever the geometry of the body and the loading) formulae; they depend only on the `stress intensity factor of the notch' (the multiplicative coefficient of the singular stress field near the apex of the notch in the absence of the crack), the length of the crack, the aperture angle of the notch and the angle between its bisecting line and the direction of the crack. Here we identify the universal functions of the two angles just mentioned which appear in these formulae, by considering the model problem of an infinite body endowed with a notch with straight boundaries and a straight crack of unit length. The treatment uses Muskhelishvili's complex potentials formalism combined with some conformal mapping. The solution is expressed in the form of an infinite series involving an integral operator, which is evaluated numerically. Application of Goldstein and Salganik's principle of local symmetry then leads to prediction of the kink angle of the crack extension. It is found that although the direction of the crack is closer to that of the bisecting line of the notch after kinking than before it, the kink angle is not large enough for the crack tip to get closer to this line after kinking, except perhaps in some special situations.     

A dislocation and point force approach to the boundary element method for mixed mode crack analysis of plane anisotropic solids

Abstract

This study investigates the feasibility of enhancing steam‐driven ejector performance. Initially, a one‐dimensional ejector theory is used to examine the effects on ejector performance of three isentropic efficiencies: nozzle efficiency η_m , mixing efficiency η_m, and diffuser efficiency η_m . Theoretical analysis demonstrates that mixing efficiency profoundly affects ejector performance, but that the other two efficiencies have slightly influenced ejector performance. This finding suggests that efficient mixing can promote ejector performance. This study also attempts to improve mixing efficiency using a petal nozzle. The behavior and characteristics of a petal nozzle are investigated by testing the nozzle under various operating conditions, i.e. primary pressure, secondary pressure, and back pressure. In addition, the study compares the experimental and theoretical results. These results prove that using a petal nozzle can improve ejector performance. The shadowgraph method was used to visualize the inner flow field of an ejector. The flow patterns observed should help to further improve ejector performance.     

同向回转双机传动振动系统相位差的模糊监督控制

通过机械系统动力学分析和计算机仿真结果相结合,提出了同向回转双机传动振动系统中两个偏心转子的相位差的模糊监督控制方法。利用机械动力学分析和计算机模拟相结合获得模糊控制规则的方法,为具有复杂数学模型的非线性系统的模糊控制提供了一条新途径,丰富了控制规则的来源。     

Crack path selection in adhesively bonded joints: the roles of external loads and speciment geometry

This paper investigates the roles of external loads and specimen geometry on crack path selection in adhesively bonded joints. First, the effect of mixed mode fracture on crack path selection is studied. Using epoxy as an adhesive and aluminum as the adherends, double cantilever beam (DCB) specimens with various T-stress levels are prepared and tested under mixed mode fracture loading. Post-failure analyses on the failure surfaces using X-ray photoelectron spectroscopy (XPS) suggest that the failure tends to be more interfacial as the mode II fracture component in the loading increases. This fracture mode dependence of the locus of failure demonstrates that the locus of failure is closely related to the direction of crack propagation in adhesive bonds. Through analyzing the crack trajectories in failed specimens, the effect of mixed mode fracture on the directional stability of cracks is also investigated. The results indicate that the direction of the crack propagation is mostly stabilized when more than 3% of mode II fracture component is present at the crack tip regardless of the T-stress levels in the specimens for the material system studied. Second, using a high-speed camera to monitor the fracture sequence in both quasi-static and low-speed impact tests, the effect of debond rate on the locus of failure and directional stability of cracks is investigated. Post-failure analyses including XPS, Auger electron spectroscopic depth profile, and scanning electron microscopy indicate that as the crack propagation rate increases, the failure tends to be more cohesive and the cracks tend to be directionally unstable. Last, as indicated by the finite element analyses results, the T-stresses, and therefore the directional stability of cracks in adhesive bonds, are closely related to the thickness of the adhesive layer and also the thickness of adherend. This specimen geometry dependence of crack path selection is studied analytically and is verified experimentally.