无面板加筋土路堤变形特征及破坏机理研究

以十房高速公路无面板加筋土路堤为研究对象,结合现场实测数据,采用有限元程序对该类型加筋土路堤的变形破坏特征和破坏模式进行计算分析。在此基础上,对加筋土路堤的加筋刚度、加筋间距进行参数分析。主要结论如下：①加筋土路堤底层填土由于圬工挡墙后部填土厚度较大而出现不均匀沉降,且不同刚度的筋材对其影响不大,施工时需保证圬工挡墙后部填土的压实度。②各层加筋体最大应变值均分布在靠近路堤坡面处,其轴力最大值位于加筋土路堤中下部。③破坏模式为内部破坏,表现为筋材拉断,破坏面靠近加筋土路堤坡面处;圬工挡墙的结构强度和基础稳定性对整个加筋土路堤的稳定性具有重要作用。④随着加筋体轴向刚度的增加和加筋间距的减小,双向位移逐渐减小,而安全系数均相应增大,但加筋体轴向刚度增加到一定程度时,其对加筋土路堤的变形稳定特征影响减弱。研究成果对山区加筋土路堤的设计计算和施工具有一定的理论和借鉴意义。     

板柱节点在剪力和反复荷载作用下的非线性有限元分析

本文对板采用四结点分层板弯曲单元,对柱采用八结六面体等参单元,建立了钢筋混凝土板柱节点有限元非线性计算模型,编制了反复荷载下钢筋混凝土非线性有限元计算程序。文中介绍了作者进行的板柱节点在反复荷载作用下的试验结果,用试验数据合流验证了所建立的有限元程序的可靠性。文反柱中节点和边节 竖向剪力和低周反复水平茶叶工共同作用下的受力性能进行了全过程计算分析。     

薄层软基上加筋垫层路堤稳定计算的简布条分法

针对薄层软土地基的特点,本文在简布条分法基础上研究建立加筋垫层路堤整体稳定性的分析方法。在一定假设条件下,根据加筋垫层的作用原理,通过对筋材受力分析和加筋垫层路堤的整体稳定极限平衡分析,推导出针对薄层软土地基的安全系数表达式和条间切向力H_i的表达式,通过迭代求解建立基于简布条分法的加筋垫层路堤整体稳定安全系数表达式。继而采用Python语言,对本文提出的加筋垫层路堤整体稳定性评价方法实现编程,并结合实际案例进行计算分析,验证所建立稳定性分析方法的可行性。     

弹性波速反映黄土加固凝聚力变化的试验研究

试验中运用骨架波速和黄土加固凝聚力的概念，将饱和度的增加引起土体密度的增加对波速的影响与水破坏加固凝聚力对波速的影响区分开来；在相似的压力和饱和度条件下采用动力作用前后分别测试弹性波速的方法，将动力荷载对加固凝聚力的破坏作用与土样自身的颗粒组分对波速的影响区分开来。初步研究了水及动力作用对黄土加固凝聚力的破坏及黄土波速的变化规律。     

Comparison of Seismic Design Codes between China and the United States for Reinforced Soil Retaining Walls

Because of its excellent seismic performance, reinforced soil retaining walls are increasingly used in civil engineering. Although many countries have published corresponding design codes, the differences between them are still relatively large. Using the FHWA Code and the Code for Seismic Design of Railway Engineering (CSDRE), stability calculations of reinforced soil retaining walls were carried out and the similarities and differences between these two design codes were analyzed. According to the comparative analysis, the following conclusions are drawn: the inertia force, the earth pressure and the tensile force of reinforcements calculated from the CSDRE are less than those from the FHWA Code, and the safety factor calculated from the former is larger. Although the M-O method is recommended to calculate the dynamic earth pressure, the FHWA Code suggests a higher action point as compared to the CSDRE.     

Quantifying lateral root reinforcement in steep slopes – from a bundle of roots to tree stands

A review of present modelling approaches for root reinforcement in vegetated steep hillslopes reveals critical gaps in consideration of plant–soil interactions at various scales of interest for shallow landslide prediction. A new framework is proposed for systematic quantification of root reinforcement at scales ranging from single root to tree root system, to a stand of trees. In addition to standard basal reinforcement considered in most approaches, the critical role of roots in stabilizing slopes through lateral reinforcement is highlighted. Primary geometrical and mechanical properties of root systems and their function in stabilizing the soil mass are reviewed. Stress–strain relationships are considered for a bundle of roots using the formalism of the fiber bundle model (FBM) that offers a natural means for upscaling mechanical behavior of root systems. An extension of the FBM is proposed, considering key root and soil parameters such as root diameter distribution, tortuosity, soil type, soil moisture and friction between soil and root surface. The spatial distribution of root mechanical reinforcement around a single tree is computed from root diameter and density distributions based on easy to measure properties. The distribution of root reinforcement for a stand of trees was obtained from spatial and mechanical superposition of individual tree values with regard to their positions on a hillslope. Potential applications of the proposed approach are illustrated in a numerical experiment of spatial strength distribution in a hypothetical slope with 1000 trees randomly distributed. The analyses result in spatial distribution of weak and strong zones within the soil where landslide triggering is expected in large and continuous zones with low reinforcement values. Mapping such zones would enhance the quality of landslide susceptibility maps and optimization of silvicultural measures in protection forests. Copyright © 2010 John Wiley & Sons, Ltd.     

谈谈建筑玻璃幕墙的防雷方法

对建筑玻璃幕墙的雷电危害及防雷措施进行分析，阐述玻璃幕墙防雷的有关做法。     

FBG传感器在碾压仿真混凝土大坝模型实验中的应用

光纤光栅传感器(FBG)具有抗电磁干扰、结构简单、测量精度高、长期稳定性好,可以实现实时、在线监测等优点,在传感器领域中得到了广泛的应用。对自行开发的管式光纤光栅应变传感器进行了混凝土梁纯弯标定实验;利用光纤光栅传感器检测了混凝土结构内部的应变变化;应用该种传感器,对在白噪声、正弦波、随机波三种动力荷载作用下碾压仿真混凝土大坝坝段模型结构各个工况下的应变进行分析。结果表明:自行开发的管式光纤光栅传感器应变测量值与电阻应变片测量值符合很好;成功监测了碾压仿真混凝土大坝坝段模型在动荷载作用下的弹性应变和启裂应变,为大坝结构在地震作用下的健康状况分析提供可靠依据。     

Performance of geosynthetic reinforced soil bridge abutments with modular block facing under fire scenarios

This paper investigates the effect of fire on the performance of geosynthetic reinforced soil bridge abutments using experimental tests and finite element analyses. Experimental programs were comprised of a series of tensile strength tests at elevated temperatures and fire resistance tests, which were performed on a physical model. Findings revealed the adverse effect of fire on geosynthetic reinforced soil bridge abutments when fire duration exceeded 60 min. Results show that the depth within the backfill affected by the fire is approximately 50 cm.     

Behavior of Reinforced Soil Retaining Wall With Limited Fill Zone Paramete

Several experiments are carried out to understand the deformation behavior of reinforced soil retaining wall with limited fill zones under vertical surcharge strip loading. Test set-up along with all the instrumentations is developed to carry out the experiments. Panel displacements and strain distribution along geogrid layers are observed. Effectiveness of the reinforced soil wall is also evaluated using a geogrid material. Finite element analysis is carried out using commercial software PLAXIS version 8 for the above problem without and with anchoring of reinforced soil retaining wall in the limited fill zone. The results are compared and reported in this present paper.