水中沉井下沉期间刃脚空间受力试验

以沪通大桥沉井为背景,设计完成了深水大截面沉井下沉模拟试验。模拟了沉井在水中不排水吸泥下沉的过程,并分析了沉井在下沉过程中刃脚踏面和斜面应力在空间上的分布规律,得出沉井角点处应力最大,长边中点处最小,短边平均应力大于长边的结论。以长边中点为基准应力,确定了长宽比为1.33时刃脚全截面的应力系数。刃脚斜面上应力除受空间位置影响外还与泥面高度相关,且变化规律与踏面应力相反。当泥面高度确定后,用三次函数确定其应力分布。讨论了倾斜、翻砂突沉对刃脚受力的影响,得出两者均会引起刃脚空间受力分布的改变。发现沉井翻砂和突沉前后刃脚踏面应力、斜面应力、刃脚处水力梯度均会发生明显的变化,且变化趋势均早于沉井翻砂和突沉的发生,对沉井翻砂和突沉的预警有重要意义。     

松软煤层穿层孔挠性钻具强造斜机理与过程研究

增加松软煤层穿层孔煤孔段的长度可以提高穿层孔单孔瓦斯抽采效果,利用挠性钻具组合施工煤孔段可以达到延长煤孔段的目的。本文建立了挠性钻具施工的力学模型,研究了强造斜的运动学特征,并提出了造斜过程的运动学曲线;根据力学模型及运动学特征,研究了强造斜钻进工艺,尽可能增加钻孔煤层钻遇率。     

组合桩在唐山沿海地区的试验应用

唐山沿海地区由于自然历史原因造成土体结构与内陆地区相差甚远,土体结构多层,且上部以软弱粘性土、砂类土为主,使得单一桩型成本较高、效率低、施工难度大且易造成环境污染。针对这些问题并结合本地区地层,设计试验了一套粉喷桩和预应力混凝土管桩相结合的柔刚组合桩施工方法,降低了施工难度、提高了效率、降低了成本,实现桩基施工无泥浆排放的节能环保示范,为类似地区地基基础工程施工提供了借鉴和参考。     

非黏结柔性立管疲劳损伤特性分析

对柔性立管的疲劳损伤特性进行分析,探究抗拉层与抗压层的疲劳特性,并分析弯曲加强器的存在与否对柔性立管疲劳损伤的影响。研究表明:柔性立管最内层抗拉层上的疲劳损伤最大,从内到外,抗拉层的疲劳损伤依次减小;抗压层受到的疲劳损伤远小于抗拉层的疲劳损伤;弯曲加强器的存在可以减小立管的疲劳损伤,并改变抗拉层疲劳危险点的位置。     

公路路基地基承载力的离心模型试验与分析

公路路基由于基底的柔性和荷载分布为梯形,路基地基的破坏模式和确定方法与刚性基础地基有所差异,对公路路基地基承载力的研究具有重要的理论意义和实用价值。通过柔性条形基础、梯形路基以及模拟沟谷地形的柔性条形基础等3组离心模型试验,对公路路基地基的破坏机制和极限承载力进行了研究,并采用关联流动的Mohr-Coulomb内切圆屈服准则对试验结果进行了数值模拟和对比分析,研究结果表明,公路路基地基由于基底的柔性和较高的离心加速度,很难产生理想的整体剪切破坏形式;与刚柔性条形基础相比,梯形路基作用下的基底中心点沉降更大;沟谷地形对柔性条形基础基底中心点的沉降有一定的影响,但并不明显影响地基极限承载力。     

Response of underground pipeline through fault fracture zone to random ground motion

It is assumed that a pipeline is laid through a vertical fault fracture zone, and is excited by seismic ground motion modelled as stationary stochastic process. For horizontal incidence of waves, the cross-PSD (Power Spectral Density) function is developed using wave propagation theory, while for vertical incidence of waves the cross-PSD function is composed by auto-PSD model, coherence model and site response model. As the seismic input, the cross-PSD function is used to calculate the the axial and lateral seismic responses of underground pipeline through the fracture zone. The results show that the incident directions of seismic waves, width and soil property of the fracture zone have great influence on underground pipeline. It is suggested that the flexible joints with appropriate stiffness should be added into the pipeline near the interfaces between the fracture zone and the surrounded media.     

Flexible support of a pile embedded in unsaturated soil under Rayleigh waves

Under the action of Rayleigh waves, pile head is easy to rotate with a concrete pile cap, and pure fixed-head condition is rarely achieved, which is a common phenomenon for it usually occurs on the precast piles with insufficient anchorage. In addition, the propagation characteristics of Rayleigh wave have been changed significantly due to the existence of capillary pressure and the coupling between phases in unsaturated soil, which significantly affects the pile-soil interaction. In order to study the above problems, a coupled vibration model of unsaturated soil–pile system subjected to Rayleigh waves is established on the basis that the pile cap is equivalent to a rigid mass block. Meanwhile, the soil constitution is simplified to linear-elastic and small deformations are assumed to occur during the vibration phase of soil–pile system. Then, the horizontal dynamic response of a homogeneous free-field unsaturated soil caused by propagating Rayleigh waves is obtained by using operator decomposition theory and variable separation method. The dynamic equilibrium equation of a pile is established by using the dynamic Winkler model and the Timoshenko beam theory, and the analytical solutions of the horizontal displacement, rotation angle, bending moment and shear force of pile body are derived according to the boundary conditions of flexible constraint of pile top. Based on the present solutions, the rationality of the proposed model is verified by comparing with the previous research results. Through parametric study, the influence of rotational stiffness and yield bending moment of pile top on the horizontal dynamic characteristics of Rayleigh waves induced pile is investigated in detailed. The analysis results can be utilized for the seismic design of pile foundation under Rayleigh waves.     

柔性仿金枪鱼月牙形尾鳍水动力分析

为研究鱼类高速游动机理,以金枪鱼月牙形尾鳍为对象,采用面元法计算分析了其非定常水动力性能。假设尾鳍在横移和摇摆的同时,以某一匀速向前运动,并假设其在弦向和展向以某一给定规律发生变形,以模仿柔性变形。探讨了前进速度、横移和摇摆的幅度、频率及其相位差对柔性尾鳍推进性能的影响,并与做相应运动的刚性尾鳍进行了对比。     

土石混填料台背回填柔性加筋注浆技术加固试验研究

通过采用柔性加筋注浆技术处理台后回填土现场试验研究并结合室内试验的方式,研究了柔性加筋注浆新技术处理湘西红砂岩土石混填台背的施工工艺特性、加固实现机制和加固效果。现场试验及质量测试表明,水平柔性加筋注浆新技术处理湘西红砂岩土石混填台背施工工艺简单、加固效果良好,具有较好的开发应用价值。同时,现场试验过程取得大量施工参数和试验数据,为改进该新技术的设计计算及施工参数、完善施工工艺获得素材; 对有效预防和减少桥头跳车现象的发生,保证行车的舒适和安全也提供了可供选择的新方式。     

斜坡坡面地质灾害SNS柔性防护系统概论

在简单分析评价国内现有坡面地质灾害防治现状的基础上 ,介绍了以钢丝绳网为主要构成材料的 SNS( Safty Netting System)主动覆盖和被动拦截柔性防护系统的基本构成和功能特征 ,从而阐明了该项新技术在防护功能、标准化设计与施工作业以及对复杂地形的适应性和安全可靠性等方面的技术经济优势。