流固耦合的多元结构深厚覆盖层透水地基的力学特性

深厚覆盖层多元结构坝基在渗流过程中各土层力学差异明显，分析时关注的具体问题也不尽相同，需要深入研究。基于比奥固结理论，考虑土体的非线性流变以及土体固结变形过程中孔隙度、渗透系数、弹性模量及泊松比的变化；借助ADINA流固耦合模块来模拟西藏达嘎水电站坝基渗流场与应力场耦合过程，分析各层力学特性及相互作用。研究表明，透水性较强的表层土体是渗流主要通道，也是渗流进出区和沉降变形体现区，应在上游采取措施提高其压缩模量，下游区域增设反滤层和排水设施；坝基中的粉细砂层是坝基沉降的主要原因，对坝基沉降起主导作用，同时应注意其液化特性对坝基的不利影响；坝基中的承压含水土层对下游上部结构产生向上顶托力，若位置较深，则破坏性较小；坝基深部土层对整个坝基的渗流破坏影响较小，但对沉降和渗流量的影响不可忽视；表层砂卵砾石层和粉细砂层的渗透系数相差较小时，土层间不会发生接触冲刷。此外，还发现坝基孔隙水压力在快速衰减阶段被消散，期间土体固结较快。垂直防渗墙能有效降低渗透坡降和渗流量，将坝基沉降变形控制在防渗墙上游区域，但上游坝基变形对防渗墙产生较大的水平推力，应加大防渗墙尺寸或者采用辅助渗控措施。     

土体固结与溶质运移三维耦合模型

考虑堆场上覆堆积体自重引起的土体固结与溶质运移的耦合效应已成为环境土工领域中的热点问题。在Biot固结理论和溶质运移理论相结合的基础上,以孔隙率作为耦合参量,将固结方程与运移方程相联系,考虑土体固结对溶质运移模型参数的影响,建立了溶质在固结变形土体中运移的三维耦合模型。采用多场耦合有限元软件COMSOL Multiphysics对模型进行了数值求解。数值模拟结果表明,土体固结变形对溶质运移过程具有较强和持久的阻滞作用,导致溶质运移深度以及污染羽范围的减小,在模拟运移20 a时,运移距离减小率已高达27.75%,且随着时间的增加而逐渐增大;溶质在水平方向的迁移距离不可忽略,随着横向水力梯度的增大而增大。     

钢筋混凝土无腹筋细长梁剪切破坏机理模型研究综述

根据现有关于钢筋混凝土无腹筋细长梁剪切破坏机理问题的研究成果,介绍了基于修正压力场理论的抗剪模型、临界剪切裂缝理论、塑性理论、压力路径理论、劈裂破坏理论和基于截面应变分析的抗剪模型的基本假设、核心观点及受剪承载力计算方法,并给出总结、归纳及评析;另一方面,利用相关试验数据和ACI-DAfStb无腹筋细长梁剪切破坏数据库,分别对不同理论模型的受剪承载力计算公式进行了设计参数的影响评估和统计评估;并展望了无腹筋细长梁剪切破坏机理研究的发展方向。研究结果表明：不同理论模型的部分假设缺少直接的试验依据支持,梁腹混凝土的受拉（劈裂）或受剪（骨料咬合）以及受压区混凝土对抵抗剪力的贡献成为抗剪机制的主要分歧;不同受剪承载力计算公式对不同影响因素的考虑方式的合理性和计算结果的准确度均有待进一步提高。后续深入研究应综合考虑剪切破坏问题的随机性和物理属性,利用先进测试技术、应力演化分析方法,进一步揭示剪切破坏机理。     

基坑开挖及降水对坑外地表沉降的影响

考虑降水、支护结构变形以及基坑隆起3个因素引起的基坑周围土体的沉降,根据降水引起土体沉降的机理,运用修正的分层总和法单独计算出由降水引起的周围土体沉降。通过研究基坑开挖引起坑外土体沉降的规律,推导出由基坑开挖引起的坑外土体沉降理论公式。把降水引起的沉降及基坑开挖引起的沉降进行叠加,加入修正系数,最终以简化的理论公式合理地计算出基坑周围土体沉降。具体工程验证表明,推导的理论解析解与实测数据十分接近,能有效预估基坑周围土体沉降,为施工方案编制提供可靠的理论依据,最大限度减少基坑施工对周围环境的影响。     

降雨条件下坡积土边坡暂态饱和区形成机理及分布规律

降雨是引起坡积土边坡失稳的最常见外部因素之一。雨水的入渗在引起土体抗剪强度参数降低的同时，还将导致土体重度的增加、基质吸力的降低，最终造成边坡的失稳。开展雨水在边坡内部的渗流过程研究已成为分析边坡在降雨条件下稳定性的前提。基于有限元数值模拟方法，进行了雨水在土体中渗流过程的模拟，着眼于降雨条件下边坡暂态饱和区的形成、分布及消散特征，描述了该过程中边坡内部含水率、基质吸力、水力梯度的变化规律。结果表明：暂态饱和区形成的主要原因是土体中向湿润锋下方渗出的雨水量小于降雨入渗补给量，从而使得土体中的含水率累积升高；暂态饱和区的形成与降雨强度、降雨时间具有十分密切的关系，暂态饱和区形成时间、雨水入渗深度、土体表面体积含水率大小分别与降雨强度存在函数关系；清晰描述了暂态饱和区形成发展消散地下水位升高的全过程，从该过程看，边坡排水措施的设计值得思考。     

复合土钉支护转角有利影响范围

基坑复合土钉墙转角处有明显的空间效应，受力变形较小，对支护结构有利，但不清楚转角定量的有利影响范围，目前设计中仍按照与基坑中部一样保守设计，为在此范围内降低土钉用量，避免保守设计，对水泥土搅拌桩复合土钉支护结构建立了全尺寸整体三维有限元模型，这种模型包含基坑的转角，能考虑基坑的空间效应，通过建立接触面单元，能考虑土体和搅拌桩、土体和土钉的相互作用，量化分析了基坑转角对支护结构受力和变形的有利影响范围，计算结果表明，基坑转角对开挖面水平位移、地表沉降、坑底隆起、土钉轴力的有利影响范围分别约为1.3、1、1、1.2倍的开挖深度。经与实际工程现场实测值对比，验证了该模型分析结果的可靠性，同时分析结果优于平面二维和局部三维有限元模型，结论为复合土钉支护结构的优化设计和安全施工提供了理论依据和研究方法。     

上覆分数阶粘弹性饱和场地土位移地震放大系数

考虑土体液相和固相的耦合作用,将基岩上覆场地土视为两相饱和多孔介质。为了考虑饱和场地土的粘弹性特性,其固相土骨架的应力应变关系利用分数阶Kelvin粘弹性模型来描述,建立了上覆分数阶粘弹性饱和场地土在简谐地震波作用下的运动控制方程。运用分数导数的性质并考虑上覆场地土的边界条件和透水性条件求解了上覆分数阶粘弹性场地土在简谐地震波作用下的振动问题,得到了饱和场地土的位移地震放大系数。采用数值算例分析讨论了分数导数的阶数、液固耦合系数、土体模型参数、基岩土体剪切模量比等参数对位移地震放大系数的影响。研究结果表明,分数导数的阶数、液固耦合系数、土体模型参数、基岩土体剪切模量比对饱和场地土的地震响应有较大的影响,通过压实场地土,可以达到增大液固耦合系数减小地震响应的作用,通过增大饱和场地土的粘性和剪切模量也可以减小地震反应。     

穿越正断层埋地管线的破坏模式分析

在正断层引起的地面永久性大变形作用下,埋地管线可能会发生拉伸、剪切等形式的强度破坏,亦可能在局部受压区发生屈曲破坏。利用ABAQUS有限元分析软件,建立穿越正断层埋地管线的空间有限元分析模型,采用非线性接触分析方法模拟正断层引起的地表永久性大变形作用下管线-土体间的相互作用,分析了不同管径、跨越角对管线破坏模式的影响。依据算例分析可知:小口径埋地管线易发生拉伸强度破坏,大口径薄壁管线易发生屈曲失效,口径0.65 m是管线从发生强度破坏到发生屈曲破坏的临界值;当跨越角大于90°时,角度越大越易发生屈曲失效,跨越角为100°是埋地管线发生强度破坏与屈曲失效的分界点。     

再生粗骨料混凝土碳化分析的多场耦合模型及验证

再生粗骨料混凝土的碳化是一个复杂的物理扩散和化学反应过程，其分析和预测较为困难。鉴于此，基于再生粗骨料混凝土的碳化机理，结合再生粗骨料混凝土中CO₂的扩散定律和可碳化物质的质量守恒定律，综合考虑再生粗骨料混凝土中CO₂的有效扩散系数、碳化反应速率系数、可碳化物质的量、再生粗骨料的表面附着砂浆等重要参数的影响，建立了再生粗骨料混凝土碳化分析的多场耦合模型，并通过试验数据验证了模型的有效性和适用性。     

限制性剪切蠕变的渐进式破坏发育模式与本构方程分析

以标准红砂岩方形试样为研究对象,运用自行研制开发的软弱煤岩剪切蠕变试验设备和煤岩细观力学特性测控软件、超声波检测设备,对红砂岩限制性剪切、限制性剪切蠕变过程的破坏过程、破坏模式、渐变特性进行了分析。结果表明：红砂岩试样在限制性剪切、限制性剪切蠕变条件下表现出明显的渐变破坏特性;大部分试验过程中试样内部的超声波速减小幅度较小,仅在临近破坏处有明显减小;红砂岩限制性剪切蠕变破坏发育过程表现为先形成主控破裂面,又在其附近区域形成丰富微裂隙,并发育、相互贯通,最后克服剪切面摩擦力并发生突发式破坏,且伴有较大断裂声;其破坏模式发育过程呈渐进式,破坏模式呈突发式;建立了一种可以表征红砂岩剪切蠕变渐进式破坏发育过程的本构模型。     

Settlement Analysis on Building near Retaining Pile of Deep Foundation Pit

The building settlement near a foundation pit project in Yanzhou is calculated by using calculation method related to settlement of the soil near a foundation pit, Comparing and analyzing calculated settlement values with measured settlement ,the reason for the gap between theoretically calculated values and measured settlement values is pointed out, On the foundation of careful research and analysis of the measured building settlement values ,the factors influencing the settlement of building near the foundation pit are summarized. Finally, according to practical measured values and influ- encing factors, how the settlement of building near the foundation pit is influenced was carefully analyzed. A conclusion that has practical role in Engineering is presented,which can serve reasonably for instructing foundation pit retaining design.     

对称式基坑渗流涌水量的计算方法

随着地铁、越江隧道等地下工程的日益增多，涌现出了大量的对称式基坑。基于共形映射理论，推导了对称式基坑涌水量计算表达式，并对其计算参数进行分析。研究表明，对称式基坑的单宽涌水量与渗透系数、基坑内外水头差成正比，与（相对）隔水层层顶到坑底的距离和基坑两侧止水帷幕间距的比值、止水帷幕嵌固深度和（相对）隔水层层顶到坑底距离的比值、基坑内外水头差和（相对）隔水层层顶到坑底距离的比值成反相关。     

Feature and risk identification of super karst water burst in deeply buried karst tunnel

With the acceleration of tunnel construction, emerging issue of high-pressure karst water burst becomes more and more complex, and the study subject of analyzing and grasping its features and taking effective risk control measures is still a world-class long-standing puzzle. Based on the feature analysis of the karst water burst disaster during the construction of karst tunnels at home and abroad, the special water burst accompanied with high pressure water burst, earth burst and rock burst is defined as super karst water burst. With the analysis of super karst water burst which happened in Maluqing Tunnel of Yi-Wan Railway, five basic characteristics of super karst water burst are obtained, and its risk sources are also identified from the respects both of geology and human engineering activities. Based on the theoretical analysis, numerical simulation and on-site engineering experience, several threshold conditions for the occurrence of super karst water are identified. In response to implementation plan of risk identification, the method of advanced horizontal drilling with drainage test and closed water test is also proposed.     

Thermo-mechanical coupling analysis of dual-steel-disc of wet multi-disk clutch

To solve the failure problem of power transmission caused by warping, crackle on dual-steel-disc of wet multi-disk clutch, a shipborne wet multi-disk clutch is taken as a research object, models of generation and distribution of friction heat flux are built and numerical methods to solve temperature field and coupled stress field are put forward. Research methods of thermo-mechanical coupling problem of wet multi-disk clutch are proposed. The thermo-mechanical coupling phenomenon of dual-steel-disc is investigated, and the failure mechanism of dual-steel-disc of wet multi-disk clutch is revealed. In the engagement process, the results of temperature field show that the temperature of the dual-steel-disc gradually increases from the inner edge to the outer edge, and the temperature of friction surface reaches the highest at 2.6 s in the 3-second-engagement. The rules of thermal stress distribution are attained that the circumferential tensile thermal stress appears in the region close to the inner edge, while the radial tensile thermal stress appears in the region close to the outer edge. The theoretical basis to solve the thermal failure problem of dual-steel-disc of wet multi-disk clutch is provided.     

Analysis of Solid Fluid Coupling for Tunnel Excavation in Complicated Fractured Rock Masses

When tunnels are through water bearing section of fractured rock mass, a complex interaction process between rock mass deformation and fluid transportation is one of the most important reasons for water gushing, water bursting and mud bursting.To study the rock mass deformation and fluid transportation in tunnel excavation under complex geological conditions, a hydraulic model of complex crack rock mass was established from the relationship between the crack growth degree of surrounding rock in deep buried tunnel and the engineering scale, with which fracture network of different levels in rock mass could be considered simultaneously.Furthermore,a computer Fortran program was put forward to simulate the solid fluid coupling of excavation process of a deep buried tunnel.And it was found that the principal fractures had strong flowing action and network fractures had storage function and lag effect in seepage area.And the yield area of surrounding rock was increased under the coupling of seepage field and stress field.     

Deflection and Stress Analysis of a Pavement Slab under Temperature Gradient and Axial Loading Coupling

It has been established that a pavement slab will curl up if a temperature gradient exists across the depth of a slab. A negative temperature gradient causes the slab edge to curl up while a positive temperature gradient curls up the slab center. Temperature stress in slabs is induced by self-weight and other slab constraints. At present in P. R. China, the total stress considered in cement concrete pavement design includes the load stress plus the temperature stress, and only transverse cracking from bottom to top is considered for concrete pavement. Slab responses under axial loads and temperature gradient coupling are not included. We modeled a single slab with a frictionless interface between the slab and foundation using the finite element method. Slab deflection and stress were calculated under axial loads at different slab positions and negative or positive temperature gradient coupling. The calculated results show that the different conditions of axial loads and temperature gradient coupling will change the maximum tension and cause various types of cracks in a slab.     

作物水氮耦合效应的研究进展

为了解现阶段作物水氮耦合效应研究进展，给之后深入研究水氮耦合效应机制提供理论基础，本文总结了水氮耦合效应对土壤物理性状、营养元素在土壤中的有效性、土壤酶活性、光合性能、生理代谢、植株地上及地下部分生长发育及产质量等方面的影响，并指出了现阶段水氮耦合效应研究存在的不足，包括水氮耦合受生态环境的影响、水氮利用效率差异机制、水氮调控生理及分子机制，以及水氮耦合高效管理模型等方面均有待于进一步深入研究，同时对今后在本领域的研究工作进行了展望，以期为日后加强节水节肥技术的应用提供参考。