Simplified Procedure to Evaluate Earthquake-Induced Residual Displacement of Geosynthetic Reinforced Soil Retaining Walls

Based on a series of shaking table model tests, it was found that the effects of 1) subsoil and backfill deformation, 2) failure plane formation in backfill, and 3) pullout resistance mobilized by the reinforcements on the seismic behaviors of the geosynthetic reinforced soil retaining walls (GRS walls) were significant. These effects cannot be taken into account in the conventional pseudo-static based limit equilibrium analyses or Newmark's rigid sliding block analogy, which are usually adopted as the seismic design procedure. Therefore, this study attempts to develop a simplified procedure to evaluate earthquake-induced residual displacement of GRS walls by reflecting the knowledge on the seismic behaviors of GRS walls obtained from the shaking table model tests. In the proposed method, 1) the deformation characteristics of subsoil and backfill are modeled based on the model test results and 2) the effect of failure plane formation is considered by using residual soil strength after the failure plane formation while the peak soil strength is used before the failure plane formation, and 3) the effect of the pullout resistance mobilized by the reinforcement is also introduced by evaluating the pullout resistance based on the results from the pullout tests of the reinforcements. By using the proposed method, simulations were performed on the shaking table model test results conducted under a wide variety of testing conditions and good agreements between the calculated and measured displacements were observed.     

Measured and Predicted Loads in Multi-Anchor Reinforced Soil Walls in Japan

More than 3000 multi-anchor walls have been built in Japan over the last decade. The paper briefly reviews a total of eight instrumented wall sections that can be used to estimate anchor loads at the end of construction. Measured loads are compared to predicted values using equations found in current design guidelines. The comparison shows that the current Japanese and UK design methods to compute anchor loads are reasonably accurate for walls with frictional backfills provided K_a is calculated using the Rankine equation. For walls with cohesive-frictional backfills, current design methods over-predict anchor loads by as much as a factor of two. The eccentricity term in current UK and Hong Kong design methods is shown to not improve the accuracy of load predictions and it is recommended that this additional complexity be removed from these equations. A new load equation is proposed and constant coefficients are back-fitted to measured anchor load data. The new method is demonstrated to give quantitatively better predictions of anchor loads based on the statistics for load bias values computed as the ratio of measured to predicted anchor loads at the end of construction.     

基于强度折减的有限差分法分析加筋土桥台的稳定性

采用基于强度折减理论的有限差分法对加筋土桥台结构的整体稳定性进行了数值计算与分析.计算得到了加筋土柔性桥台的土工格栅筋材的轴向受力分布情况,数值计算结果与实测数据相当接近;分析了加筋土筋材的受力机理以及筋材潜在的破裂面位置;讨论了有限差分程序FLAC分析加筋土柔性桥台时网格密度的选择,认为网格密度对计算结果的影响较大;并对加筋土结构的塑性区及塑性发展过程进行了一些分析和探讨.     

Evaluation of Extent of Damage to Geogrid Reinforced Soil Walls Subjected to Earthquakes

The aim of this study is to establish a simple method for evaluating the extent of damage to geogrid reinforced soil walls (GRSWs) subjected to earthquakes. Centrifuge tilting and shaking table tests were conducted to investigate the seismic behaviour of GRSWs, with special focus on the effects of the tensile stiffness of the geogrids, the pullout characteristics and the backfill materials. As a result, it was found that GRSWs showed large shear deformation in the reinforced area after shaking, that such deformation was influenced by the tensile stiffness of the geogrids, the pullout resistance and the deformation modulus of the backfill material, and that finally slip lines appeared. However, the GRSWs maintained adequate seismic stability owing to the pullout resistance of the geogrids, even after the formation of slip lines. It is considered that such slip lines appeared due to the failure of the backfill material. Since the maximum shear strain occurring in the backfill can be roughly estimated from the inclination of the facing panels, using a simple plastic theory, it is possible to evaluate whether the backfill has reached its peak state or not. The formation of slip lines observed in the centrifuge model tests could be well explained by this method. Finally, the method is proposed to estimate the failure sections in the GRSWs using a Two Wedge analysis.     

Performance monitoring of Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) in Louisiana

The Geosynthetic Reinforced Soil (GRS) Integrated Bridge System (IBS) is an alternative design method to the conventional bridge support technology. Closely spaced layers of geosynthetic reinforcement and compacted granular fill material can provide direct bearing support for structural bridge members if designed and constructed properly. This new technology has a number of advantages including reduced construction time and cost, generally fewer construction difficulties, and easier maintenance over the life cycle of the structure. These advantages have led to a significant increase in the rate of construction of GRS-IBS structures in recent years. This paper presents details on the instrumentation plan, short-term behavior monitoring, and experiences gained from the implementation of the first GRS-IBS project in Louisiana. The monitoring program consisted of measuring bridge deformations, settlements, strains along the reinforcement, vertical and horizontal stresses within the abutment, and pore water pressures. In this paper, the performance of instrumentation sensors was evaluated to improve future instrumentation programs. Measurements from the instrumentations also provide valuable information to evaluate the design procedure and the performance of GRS-IBS bridges. The instrumentation readings showed that the magnitude and distribution of strains along the reinforcements vary with depth. The locus of maximum strains in the abutment varied by the surcharge load and time that did not corresponds to the (45+?/2) line, especially after the placement of steel girders. A comparison was made between the measured and theoretical value of thrust forces on the facing wall. The results indicated that the predicted loads by the bin pressure theory were close to the measured loads in the lower level of abutment. However, the bin pressure theory under predicted the thrust loads in the upper layers with reduced reinforcement spacing. In general, the overall performance of the GRS-IBS was within acceptable tolerance in terms of measured strains, stresses, settlements and deformations.     

加筋土挡墙的抗震性能研究现状

首先,简述了加筋土挡墙比天然地基及普通挡土墙具有更好的抗震性能,对加筋土挡墙抗震性能的主要影响因素进行了综述,包括:筋材长度和筋材层间距、回填土性质、地震系数等。同时也指出,加筋土挡墙在地震烈度较大时也会发生破坏。最后,根据对加筋土挡墙抗震性能研究的结果指出,可以通过进一步的研究来定量评价加筋土挡墙的抗震能力,同时了解地震过程中的筋土耦合问题,综合考虑水平地震加速度(ah)和竖向地震加速度(av)对加筋土抗震性能的影响。     

预应力长锚杆加固钢筋混凝土挡墙

结合二处挡墙的实际破坏情况 ,通过计算及方案比较 ,认为预应力长锚杆加固挡墙方案符合加固的各项要求 ,可充分利用锚杆的抗拉特性提高挡墙的稳定性 ,且经济效益显著     

周期荷载作用下钢筋混凝土双肢剪力墙弹塑性分析的有限元法

建立钢筋混凝土双肢剪力墙弹塑性分析的有限元模型,采用有旋转自由度的高精度平面单元分析墙体在周期荷载作用下混凝土开裂、屈服和钢筋屈服的变化过程,为钢筋混凝土双肢剪力墙的抗震设计提供较精确的分析方法。     

钢筋混凝土叠合墙体非线性仿真研究

介绍了一种半预制半现浇钢筋混凝土叠合墙体的应用现状、构造方式及钢筋混凝土叠合墙的低周反复试验.在试验基础上用DIANA软件,对单调加载作用下半预制半现浇钢筋混凝土叠合墙体的受力性能进行数值计算,所用的分析模型考虑了边缘纵筋,还考虑了预制部分和现浇部分结合的黏结特性.计算分析结果与试验结果符合良好.半预制钢筋混凝土墙体具有良好的抗侧性能,新老混凝土协同工作性能良好.     

市政道路工程水泥稳定粒料基层压实度评定方法之分析

通过对水泥稳定粒料基层压实度与水泥混凝土弯拉强度评定对比分析 ,求取其最佳压实度评定方法     

加筋泡沫轻质土浇筑新型直立式路堤的施工

利用水泥、粉煤灰和水、发泡剂进行混合发泡,形成一种有一定孔隙率的轻质混凝土,其具有自流平、自硬化、毋需振捣的特点,只需通过软管泵送注入安装好的模板内即可。浇筑时须竖向分层、平面分区跳仓,使竖向、平面施工缝交错布设,以减少工后施工缝的反射效应。同时,采用在泡沫轻质土中加入钢塑土工格栅、金属网等措施,抑制收缩裂缝的出现。最后在泡沫轻质土两侧施工钢筋混凝土薄壁式挡墙,构成完整的道路结构。     

某加筋碎石土边坡变形破坏模式分析

通过某加筋碎石土边坡的工程实例,现场踏勘初步分析其变形破坏的主要原因,判断其可能的几种破坏模式;采用野外钻探、原位试验及室内土工试验等手段获取边坡各岩土层的物理力学指标,利用Geo-Studio软件建立二维地质模型,并进行边坡渗流和边坡稳定性计算。从正常工况和最不利工况两个角度来验证该边坡产生变形破坏的原因及模式,最后得出结论,并预测未来边坡变性破坏的发展趋势,以期为同类型加筋碎石土边坡的设计和施工提供一些参考。     

用水平层法求加筋土桥台主动土压力

用水平层法求解加筋土体作用于桥台的主动土压力,首先,通过分析加筋土体水平薄层滑楔体的受力特征,建立极限平衡方程,推导出加筋桥台主动土压力的计算公式;然后,改变参数取值,来分析加筋土体主动土压力的影响因素。研究认为土压力沿桥台高度呈现明显的非线性分布特征;填料的性能对台背土压力的影响显著,填料内摩擦角越大,土压力越小;填料黏聚力越大,土压力越小;填料的重度越大,土压力越大;加筋后相当于增加了填料的黏聚力,材料强度的发挥程度越大,台背上部受拉区的范围越深,台背土压力越小。     

Analysis of the Performance of Sand Cushions Reinforced with Horizontal Geosynthetic Elements

Soil Mechanics and Foundation Engineering - The problem of improving foundation bases in strongly deformable and structurally unstable soils is examined. A design is proposed for a sand cushion...     

配筋混凝土砌块砌体在挡土墙上的应用——某工程物料库墙体设计介绍

介绍采用混凝土砌块方法设计的某一挡土墙工程。该工程采用普通混凝土砌块墙体取代原钢混凝土墙体,取得了较好的技术经济效果。     

复杂地层条件TRD水泥土搅拌墙抗渗性能分析

超深等厚度水泥土搅拌墙作为深基坑隔水帷幕,墙体抗渗性能和强度的好坏是确保基坑安全实施和周边环境安全的关键。基于多项复杂地质条件和环境条件下等厚度水泥土搅拌墙的基坑工程实践,通过室内试验或现场原位试验对不同深度水泥土搅拌墙墙体抗渗性能进行系统的统计分析研究,并从实施效果角度进一步验证各种地层中墙体的成墙质量和隔水效果。试验结果表明,墙体渗透系数较原状土层尤其是粉土和砂土层降低显著,在深厚粉土和砂性土层中墙体渗透系数均达到10~(-6) cm/s~10~(-8) cm/s数量级;实施效果也表明,采用等厚度水泥土搅拌墙作为深基坑隔水帷幕,有效隔断坑内外地下水尤其是深厚砂层承压水的水力联系,水泥土搅拌墙抗渗性能良好。     

高强材料置换混凝土墙体表层加固方法的研究与应用

对于实际强度明显不满足设计要求的混凝土墙体,用高强材料置换其表层截面是一种简便、实用的加固方法,对所形成的墙体组合截面的弹性应力进行了解析分析,根据等强等截面、等强增大截面、超强等截面、超强增大截面四种墙体加固情况,分别推导了置换表层厚度计算方法,给出了计算例题和应用实例,可作为相关试验研究与加固设计的参考。     

钢筋混凝土框架结构抗震评估的新方法

本文阐述了基于Push-over分析的抗震评估方法,提出使用层间位移角以及结构在大震下的塑性铰转角来评估框架结构的抗震性能,给出了新的抗震性能评估的步骤.使用本文所推荐的方法对一实际工程进行了抗震性能评估,并且与现行建筑抗震鉴定标准所推荐的方法对比,结论一致.结果表明,该方法从结构整体性能分析出发,可以快速有效地评估结构的抗震性能,该方法也可以为结构加固后的抗震性能评估奠定基础.     

水平加筋砌块墙的抗弯性能

介绍了国外水平跨缝配筋的砌块墙体，在平面外单侧荷载作用下的性能所作的试验研究。总共试验万块足尺的墙体，用以测定水平钢筋的数量与种类，以及砌合方式（顺砌与顶砌）对墙体性能的影响，其中包括裂缝弯矩、荷载-挠度关系和抗弯强度。     

钢筋混凝土联肢剪力墙弹塑性分析

利用三维非线性分析程序CANNY中的纤维模型模拟墙肢、单轴弹簧模型模拟连梁,对钢筋混凝土联肢剪力墙进行了弹塑性分析;在与试验结果进行对比分析的基础上,选取了用于钢筋混凝土剪力墙非线性分析的三线型骨架滞回模型和合适材料的应力-应变关系进行建模;通过数值计算分析了轴压比、墙体分布钢筋配筋率、边缘构件配筋率、连梁纵筋配筋率对钢筋混凝土联肢剪力墙的承载力、延性、破坏形态等的影响。结果表明:轴压比、墙体分布钢筋配筋率、边缘构件配筋率对钢筋混凝土联肢剪力墙的受力性能影响较大,连梁的纵筋配筋率影响较小;所选模型具有有效性。