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。     

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.     

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。     

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。     

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。     

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。     

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。     

Failure mechanisms of tubular CHS joints with complete overlap of braces

This paper presents the experimental and numerical results of the ultimate load behaviour of tubular circular hollow section (CHS) joints with complete overlap of braces. A completely overlapped tubular CHS joint specimen is tested to failure under lap brace static incremental axial loading. The failure behaviour of the joint is carefully observed and the test result is used for the verification of finite element (FE) model. A detailed parametric study is subsequently conducted based on 1296 FE models to examine the failure modes and the load-deformation characteristics of the joint. The analytical results showed that there are four possible failure modes of the joint under lap brace axial compression namely the through brace wall plastification, the lap brace yielding, the lap brace local buckling and the lap brace member failure. A combination of these failure modes can be occurred depending on the geometrical parameters of the joints. Among these failure modes, the through brace wall plastification in contact with the lap brace is found to be the most common type of failure behaviour for joints with complete overlapped of braces at high lap brace-to-through brace wall thickness ratio.     

路基拓宽不均匀沉降观测与分析

介绍了太沙基固结理论,以某道路拓宽改造工程为例,对该工程试验路段布置了不均匀沉降观测设施,论述了观测试验的设备布置和观测过程,通过对监测数据的分析,揭示了新老路基沉降发展特点,对类似路基拓宽工程具有指导意义。     

探地雷达在高速公路隧道检测中的应用

以广贺高速公路某隧道建设为例,详细介绍了探地雷达在隧道衬砌施工质量检测中的成功应用,指出利用探地雷达对隧道衬砌检测是能够实现的,探地雷达适合大面积快速检测。     

软土地基沉降预测方法比较分析

对工程中软土地基沉降的四种预测方法进行了分析比较,从预测曲线和实测曲线以及误差曲线的比较可以看出,每种方法既有优点也有缺点,预测方法的选用要结合具体的工程实际。本文为软土地基沉降预测方法的选用提供了参考。     

界面效应对隧道拱顶下沉规律的影响分析

采用接触问题的拉格朗日乘子算法对隧道围岩与支护结构之间的界面效应进行了分析,对不同开挖步序下实际监测、考虑接触算法的FEM、不考虑接触算法的FEM三种方法所得拱顶下沉结果进行了对比分析,结果和实际现场的综合分析结论是一致的。     

地铁施工中地面沉降的预测方法与实例分析

对地铁施工中引起的地面沉降的预测方法进行了介绍,结合实例进行分析,从而得出在车站施工中最合适的地面沉降预测方法,并论证了预测方法的科学性和可行性。     

城市地面沉降成因机制以及对策的探讨

针对我国城市地区地面沉降的现状,主要探讨了我国城市地区地面沉降的成因机制和影响因素,从灾害研究角度论述了地面沉降造成的严重危害,并就应采取的相应措施提出了几点建议,从而杜绝地面沉降的发生。     

探地雷达在路面沉降检测中的应用

分析了探地雷达的基本原理,以某高速公路基层施工为例,阐述了使用探地雷达进行路面检测的检测方案、检测参数及检测数据,探测了路面沉降发生的原因,检测结果表明,探地雷达能快速定位路面以下病害分布位置和影响深度。     

多种软基处理的沉降和信息化施工试验研究

通过采用粉喷桩、浆喷桩、砂桩超载预压等方法处理高速铁路软土地基的现场试验,对不同方法处理软土地基沉降计算、沉降推算、信息化施工等方面进行了试验研究。试验表明,各种地基的理论计算沉降与实测推算的沉降有一定的差异,两者的比值在0．64—1．26之间。     

Buckling of cylindrical shells with longitudinal joints under external pressure

In this article, the bucking of cylindrical shells with longitudinal joint has been investigated through the experimental and numerical analysis. It was clarified that the buckling behavior of cylindrical shells with longitudinal joints under lateral external pressure is not only related to its dimension, but also longitudinal joint and an imperfection. The buckling of cylindrical shells with rigid joint buckles only once and in multi-lobe buckling, whereas one with flexible joints buckles twice and firstly in single-lobe buckling in the vicinity of the joint, secondly in multi-lobe buckling in remaining un-deformed area. And the more flexible the longitudinal joint, the lower the critical pressure, with respect to the same dimension of jointed cylindrical shells and imperfection condition. Moreover the numerical analysis approaches were also presented and verified, by which the imperfection can greatly enlarge the effect of joint on buckling has been demonstrated.     

Analytical algorithm for longitudinal deformation profile of a deep tunnel

To investigate the longitudinal deformation profile(LDP) of a deep tunnel in non-hydrostatic condition,an analytical model is proposed in our study.In this model,the problem is considered as a superposition of two partial models,and the displacement field of the second partial model is the same as that of the concerned problem.Therefore,the problem can be solved by a model with simple boundary conditions.We obtain the solutions for the stress and displacement fields of an infinite body caused by arbitrary surface tractions on the boundary of the coming tunnel(zone inside the tunnel before excavation) by integrating the extended Kelvin solution over the boundary.The obtained stress solution is used to solve the specific surface tractions,which can satisfy the boundary conditions of the second partial model,on the boundary of the coming tunnel in an infinite body.Then,the specific surface tractions are substituted into the obtained displacement solution to solve the displacement on the wall and face of the tunnel.Therefore,the LDP can also be calculated.The proposed solution is verified by both numerical simulation and the LDP functions recommended by other researchers.The major advantage of our analytical model is that it can consider the effects of the axial and horizontal lateral pressure coefficients.It is revealed that the horizontal lateral pressure coefficient majorly affects the LDP behind the tunnel face,while the axial lateral pressure coefficient dominates the LDP ahead of the tunnel face.Furthermore,the deformation characteristics of the LDPs ahead of the face and the unexcavated core are investigated.The axial displacements of the excavation face can be used to predict the crown displacements ahead of the face.     

Numerical analysis of tunnel thermal plume control using longitudinal ventilation

A CFD model of the 4th Beijing subway line was used to study the effect of longitudinal ventilation on heat and smoke plume movement in the tunnel. The critical ventilation velocity is correlated with the heat release rate for both a simplified heat fire source model and a complete combustion fire source model with methane gas as fuel. The influences of the heat source length and the fuel gas inlet geometry on the critical velocity are investigated for both fire source models. The results show that the influences of the combustion process and fire source area variation are not included in models based on Froude number preservation theory. Thus, Ri is no longer suitable as a dimensionless number for the critical ventilation velocity when the fire geometry or combustion conditions influence the results. The back-layering air temperature above the front of the fire source can be used to explain the different critical velocity variation regimes for all the simulation conditions.