桥梁基坑在承压水作用下的渗流分析

文章以某桥梁基坑为例,总结了地下承压水对明挖基坑工程的危害,分析了承压水渗流对桥梁明挖基坑工程的影响。通过有限元程序计算承压水影响下的基坑周边和坑内土体的渗流场,表明在承压水的影响下,坑内土体的有效应力会降低,从而导致基坑整体安全系数降低。     

矩形顶管施工引起地表变形的实测分析

顶管施工会对周围土体产生扰动,引起土体移动。而相对于圆形顶管,矩形顶管对周围土体的扰动更大,从而引起的地表变形也更大。文章结合工程实例,对矩形顶管施工引起的地表变形规律进行了探讨,分析矩形顶管施工引起土体移动的影响因素,为同类工程的设计与施工提供参考。     

桥下新建高填方道路对桥墩的影响及保护措施分析

在既有立交和桥梁下新建道路、停车场及回填土方等,会导致桥墩在回填后受到土体沉降产生的负摩阻力及土体变形等不利因素的影响而形成安全隐患。文章结合重庆五里店立交桥工程实例,提出了采用"砌筑环形条石挡墙"的方式对桥墩进行保护,并通过有限元数值计算分析了高填方对桥梁墩柱的影响,为桥梁结构的安全设计和施工提供依据。     

城市地铁越江隧道上浮引起的土体变形分析

文章基于盾构隧道统一土体移动模型基本假定,建立了隧道上浮作用下的两圆顶部相切土体移动模型;利用Melan公式计算得出了隧道上浮引起的土体变形(上浮力作用下的土体变形,再叠加土体损失引起的土体变形)二维解;应用ABAQUS有限元分析软件,结合在建南昌地铁1号线抚河桥区段工程,建立计算模型,对隧道上浮引起的土体变形进行了模拟计算。结果表明,推导的土体变形二维解与数值模拟结果比较吻合;越江隧道上浮引起的土体变形规律是河底表面呈"倒沉降槽"形,深层土体呈"双弓"形,且其幅度随距隧道轴线距离增大而减小。     

土体力学参数随隧道施工动态变化对地层扰动影响的研究

文章基于土的三相体系,并依据隧道施工对土体扰动区域的划分,推导得出土体孔隙比与体应变的关系;运用有限元法计算不同区域的体应变,参考土体力学参数与孔隙比的关系,计算扰动土体力学参数在隧道开挖前后的变化,进而研究考虑土体力学参数变化与否对地层扰动的影响差异。计算实例分析表明:相对于假设隧道开挖过程中土体力学参数恒定的情况,在考虑土体力学参数改变情况下地表最大沉降增大8.1%,塑性区域范围面积增大55.6%。     

盾壳摩擦对周围土体工作性状影响的研究

文章以天津地铁二号线东南角站至建国道站区间左线盾构掘进项目为依托,采用ABAQUS对盾构掘进过程产生的地表沉降进行了计算,并结合工程实测结果对其进行验证,并进一步分析了在一定掌子面推力下的盾构掘进过程中,不同盾壳摩擦作用对周围土体变形与受力的影响。研究结果表明:盾壳摩擦作用对土体沿掘进方向的水平位移和附加应力影响较大,且影响最敏感区域位于盾构机头和盾尾附近;当距离隧道超过一倍隧道直径时,盾壳摩擦产生的土体附加应力衰减至可被忽略的程度。     

多因素下双线盾构隧道施工引起的土体变形研究

考虑多因素(土体损失、正面附加推力、盾壳摩擦力、附加注浆力)的作用下,文章首先提出了改进统一土体移动模型的方法,其次建立了力学计算模型,对双线水平平行盾构隧道施工引起的土体变形计算方法进行研究。根据弹性力学Mindlin解,对多因素中后3个因素引起的土体变形理论解进行计算,基于统一土体移动模型解对土体损失引起的土体变形理论解进行计算,最后叠加得到多因素下总的土体变形理论解。采用该方法对杭州地铁1号线的纵向地表沉降、纵向水平位移及不同深度处的土体竖向位移进行计算,研究其变化规律;同时对水平位移变化的影响因素进行分析。研究结果表明:随深度改变,在最大沉降量附近10~13 m横向范围内的土体沉降会产生改变;土体水平位移方向随计算点和隧道的位置关系变化而发生改变;随着两隧道间距J的增大,双线隧道深度附近的土体水平位移减小,地表附近处的水平位移值变化值不大。     

人工冻结法单管冻结引起周围土体温度场变化的研究

为了研究人工冻结法单管冻结引起周围土体温度场的瞬态变化,文章根据冻结峰面将土体分为冻结区及降温区,并构建了相应的人工冻结相变温度场模型;采用变量代换的方法求解了单管冻结相变热传导控制方程,得出了用指数积分函数表示的冻结管周围土体温度瞬态变化的解析表达式;将指数积分函数级数展开式取有限项,计算得出了冻结管周围土体冻结区及降温区温度场分布的解析表达式;结合一工程算例探讨了土体冻结温差、冻结管吸热系数、单位体积土体的结冰潜热等因素变化对人工冻结温度场的影响。研究结果表明:土体冻结温差越大,冻结峰面半径发展速度越慢;冻结管吸热系数越大,土体冻结锋面半径的发展速度越快;土体的结冰潜热越小,其冻结峰面半径发展速度越快。并且,这三个影响因素与冻结峰面半径的发展近似呈线性关系。     

搅拌桩坑内加固施工挤土效应研究

深基坑工程利用深层搅拌桩进行地基加固时,周围土体挤出效应不容忽视。结合实际工程的施工情况和监测结果,分析搅拌桩施工过程中土体水平位移、竖向位移的变化规律及影响因素,提出有效控制土体挤出变形的合理施工流程。     

基坑开挖对邻近地铁结构基础的影响研究

对于新建基坑工程来说,在确保其自身结构安全性的同时,同样需要充分考虑到由于基坑施工所引发的土体位移因素,为邻近地铁的运营安全性提供保障条件。以某工程为例,从假定模型、材料参数、施工模拟以及计算点与变形控制标准布置4个角度构建数值分析模型,并展开对计算结果的分析,阐述基坑与隧道水平净距以及基坑支护结构所造成的影响,希望能够为同行业工作者提供一些帮助。     

高速公路改扩建工程水土保持监测与评价

开展水土流失监测是水土保持监管的重要手段。文章以广西沿海高速公路改扩建工程一期工程水土保持监测实践为例,分析了工程建设水土流失特点,介绍了水土保持监测技术和方法,并通过对工程实例监测结果的分析评价,提出了水土保持监测工作中易出现的问题及相应的解决方案。     

论高速公路边坡水土保持植物防护设计

通过对高速公路边坡水土保持的研究,主要论述边坡水土保持植物防护设计的应用,从高速公路水路流失的特点出发,指出边坡为公路水土流失重灾区。进行植物防护设计不仅能够达到防护效果,还有利于恢复植被,改善生态环境,有效地防止水土流失,并介绍了高速公路边坡水土流失植物防护技术设计原则。最后通过实践分析,对植物防护做出具体设计,为今后同类工程的水土保持措施布局提供参考和借鉴。     

Soil Body Deformation Caused by Construction of a Double-Line Shield Tunnel with Multiple Factors北大核心CSCD

Considering the influence of many factors (soil loss, frontal additional thrust, the friction force of the shield shell and the additional grouting force), a method for improving the uniform soil body movement model is pro-posed, and a mechanical calculation model is established to study the calculation method for soil body deformation caused by double-line parallel shield driving. Based on the Mindlin solutions of elastic mechanics, the theoretical solutions for soil body deformations caused by the last three factors are calculated; considering the uniform soil body movement model, the theoretical solutions for soil body deformations caused by soil loss are calculated, then the to-tal theoretical solutions for soil body deformations under multiple factors are obtained by means of superposition. The vertical surface settlement, vertical horizontal displacement, and vertical displacements of the soil body at different depths of Hangzhou Metro Line 1 are calculated to analyze the variation laws. Meanwhile the influential factors for horizontal displacement variation are studied. The research shows that with a change of depth, the settlement of the soil body changes within the scope of 10 to 13 m in the horizontal direction near where the maximum settlement occurs;the direction of the horizontal displacement of the soil body changes with a change of the positional relationship be-tween the calculation points and the tunnel; and with an increase of interval J for the two tunnels, the horizontal dis-placement of the soil body of a deep double-line tunnel decreases while the displacement near the surface changes slightly. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

干燥细砂破坏形式试验分析

土体破坏不是偶然的现象,受控于多种因素,而这些因素均为变量,不能精确地知道它们的数值。土体的结构是指土颗粒或集合体的大小和形状、表面特征、排列形式及它们之间的连接特征,也是影响土体破坏的多种因素之一。文章通过模型试验发现细砂的破坏是多种形式的综合体,其中土体的密实度、颗粒大小、级配等均是影响土体破坏形式的重要因素。     

Runoff and soil erosion from highway construction spoil deposits: A rainfall simulation study

To measure soil loss from these road construction spoils, 30 rainfall simulations involving five rainfall intensities were conducted to study runoff and soil erosion processes on a road in China. Twenty-five of the rainfall simulations were carried out on loose materials five different slopes. Another five rainfall simulations were conducted on compacted road materials with a slope of 30.6%. The results show that soil bulk density has a positive effect on runoff rate, and the effect of slope on runoff rate changes with rainfall intensity. Higher soil bulk density increases soil loss under low rainfall intensity, but decreases soil loss when rainfall intensity is high. Soil loss is positively related to slope, but the relationship differs from that in prior studied of croplands and disturbed lands. Equations for predicting soil erosion from loose materials and compacted road are developed.     

浅谈南友公路膨胀土路堤的研究

文章针对广西南宁-友谊关公路宁明段膨胀土的工程地质和土性特征,分析该路路堤出现膨胀土病害的原因,提出膨胀土路堤试验的修筑方法,为膨胀土路堤的设计提供参考。     

膨胀土路堤物理处治技术的应用研究

文章通过对南宁外环高速公路沿线膨胀土的物理力学特性进行试验研究,分析了膨胀土填筑路基的可行性,介绍了膨胀土路堤的相关设计参数及物理处治技术的施工与质量标准,并评述了膨胀土路堤物理处治技术的应用效果。     

Analysis of Responses of Pile Groups Due to Tunnelling during Excavation and Operation Periods Considering Rheological Behavior of Soft Soils北大核心CSCD

The additional pile responses due to the rheological behavior of the soil in the construction and operation periods of tunnelling are disadvantageous to the safety of the pile. However, among the current studies concerning with the rheological behavior of soft soil, the pile responses induced by the long-term settlement of 3D soil are seldom investigated. This paper mainly utilizes the finite difference software FLAC to discuss the pile response during excavation and operation periods considering rheological behavior of soft soil based on twostage analysis method. At the first stage, the displacement controlled method (DCM) is applied to simulate the short-time movement of soil during excavation period, the simulation results such as the shape of trough, pile responses such as pile deflection, settlement, axial force and bending moment are compared with the results of existing studies, and the numerical model is verified to be acceptable. At the second stage, the rheological behavior of soft soil is considered to estimate the long-term settlement of soil, the additional pile response is analyzed based on the CVISC model. Then, the influences of the four rheological mechanical parameters on the long-term soil settlement and pile responses are discussed and a fitting equation is proposed to estimate the long-term settlement of soil during the operation period. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

车辆载荷碾压作用下管道的安全性测试与分析

通过对重车碾压的土层压力进行试验,总结计算出了车辆载荷引起土层应力的分布规律,综合土层应力的分布规律、土层参数和钢材参数,建立了重车碾压对管道应力影响的有限元分析模型,提出了应力在土壤中沿深度方向变化的计算公式,通过静载和动载分析,计算出了管道安全的最低埋设深度,对埋深大于1．5m且管道上覆土层均匀密实的管道,由车辆载荷而导致的管道附加应力与管道强度及管道内气压相比,不会危及管道安全,也不会造成管道的疲劳破坏。     

Runoff and water erosion on road side-slopes: Effects of rainfall characteristics and slope length

To investigate the effects of rainfall and slope length on water erosion on road side-slopes, runoff and soil loss are measured from natural runoff plots along the Qinghai-Tibet highway near Tuotuo River. Rainfall erosivity used in the revised universal soil loss equation is a good predictor for runoff and soil loss from road side-slopes. Runoff depth, sediment concentration and soil loss decreases as slope length increases.