Numerical evaluation of the performance of a Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) under different loading conditions

This paper presents the results of a finite element (FE) numerical analysis that was developed to simulate the fully-instrumented Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) at the Maree Michel Bridge in Louisiana. Four different loading conditions were considered in this paper to evaluate the performance of GRS-IBS abutment due to dead loading, tandem axle truck loading, service loading, and abnormal loading. The two-dimensional FE computer program PLAXIS 2D 2016 was selected to model the GRS-IBS abutment. The hardening soil model proposed by Schanz et al., (1999) that was initially introduced by Duncan and Chang (1970) was used to simulate the granular backfill materials; a linear-elastic model with Mohr-Coulomb frictional criterion was used to simulate the interface between the geosynthetic and backfill material. Both the geosynthetic and the facing block were modeled using linear elastic model. The Mohr-Coulomb constitutive model was used to simulate the foundation soil. The FE numerical results were compared with the field measurements of monitoring program, in which a good agreement was obtained between the FE numerical results and the field measurements. The range of maximum reinforcement strain was between 0.4% and 1.5%, depending on the location of the reinforcement layer and the loading condition. The maximum lateral deformation at the face was between 2 and 9 mm (0.08%–0.4% lateral strain), depending on the loading condition. The maximum settlement of the GRS-IBS under service loading was 10 mm (0.3% vertical strain), which is about two times the field measurements (～5 mm). This is most probably due to the behavior of over consolidated soil caused by the old bridge. The axial reinforcement force predicted by FHWA (Adams et al., 2011b) design methods were 1.5–2.5 times higher than those predicted by the FE analysis and the field measurements, depending on the loading condition and reinforcement location. However, the interface shear strength between the reinforcement and the backfill materials predicted by Mohr-Coulomb method was very close to those predicted by the FE.     

Performance of a Nonwoven Geotextile Reinforced Wall with Unsaturated Fine Backfill Soil

The use of marginal backfills in GSE （geosynthetic stabilized earth） walls has not been recommended by different standards specifications. Restrictions are motivated by the poor hydraulic conductivity of fine soils that are capable of developing of water pressures. However, the use of granular materials can expend the cost of the construction. As a result, local soils, granular or not, have been increasingly used. Unsaturated conditions of fine soils may result in convenient performance even using extensible reinforcements. This paper evaluates the performance of a full scale model of a nonwoven geotextile reinforced wall constructed with fine grained soil backfill. The unsaturated condition was maintained and matric suctions, displacements and reinforcement strains were monitored during the test. Results have shown that the unsaturated condition of the backfill allowed maximum reinforcement peak strain of 0.4 %. For the case of a wrap faced wall on a firm foundation the performance and good agreement between measured strains and factors of safety from limit equilibrium analyses have shown the maintenance of unsaturated conditions as an economical alternative to the use of high quality fill.     

Numerical parametric study of geosynthetic reinforced soil integrated bridge system (GRS-IBS)

A 2-D finite flement model was developed in this study to conduct a FE parametric study on the effects of some variables in the performance of geosynthetic reinforced soil integrated bridge system (GRS-IBS). The variables investigated in this study include the effect of internal friction angle of backfill material, width of reinforced soil foundation (RSF), secondary reinforcement within bearing bed, setback distance, bearing width and length of reinforcement. Other important parameters such as reinforcement stiffness and spacing were previously investgated by the authors. The performance of GRS-IBS were investgated in terms of lateral facing displacement, strain distribution along reinforcement, and location of potential failure zone. The results showed that the internal friction angle of backfill material has a significant impact on the performance of GRS-IBS. The secondary reinforcement, setback distance, and bearing width have low impact on the performance of GRS-IBS. However, it was found that the width of RSF and length of reinforcement have negligible effect on the performance of GRS-IBS. Finally, the potential failure envelope of the GRS-IBS abutment was found to be a combination of punching shear failure envelope (top) that starts under the inner edge of strip footing and extends vertically downward to intersect with Rankine active failure envelope (bottom).     

混凝土及钢筋混凝土材料酸性土壤腐蚀规律的试验研究

本文简要介绍了混凝土及钢筋混凝土材料在不同酸性土壤中腐蚀情况的实测结果。根据实测结果及环境腐蚀因素,初步总结了不同混凝土材料在酸性土壤中的腐蚀过程与强度变化规律,分析研究了酸性土壤对混凝土材料的腐蚀机理及主要影响因素,对提高酸性地区混凝土及钢筋混凝土结构在地下的耐久性具有指导意义。     

加筋土挡墙在软土地基上的设计与应用

结合加筋土挡墙在软土地基中的应用实例 ,分析和验证了软土地基条件下加筋土挡墙的力学特性 ,并将加筋土挡墙与重力式挡墙的造价进行了对照 ,认为在软土地基条件下 ,加筋土挡墙可充分发挥软土地基的承载能力 ,是一种既合理又经济的支挡结构形式。     

某加筋土挡墙的事故分析及处理措施

分析了某钢筋混凝土加筋土挡墙事故的设计与施工原因,提出了加固处理措施。     

桩锚（撑）与加筋联合支护结构的数值模拟与设计理论研究

本文采用岩土工程数值模拟方法建立桩锚（撑）与加筋联合支护结构的计算模型，对不同土层和桩锚（撑）刚度的联合支护结构的作用机理和变形性状进行数值模拟，得到了一些有意义的研究成果。同时，总结规律并对已有的设计方法进行改进，提出一套行之有效的设计理论和方法，并成功地应用于多个工程的实践中。     

纤维塑料筋(FRP筋)在混凝土结构中的应用

为解决钢筋混凝土结构中钢筋锈蚀的问题,国内外普遍开展了纤维塑料筋（FRP筋）来代替普通钢筋的应用研究.FRP筋具有耐腐蚀、抗拉强度高、电磁绝缘性好及弹性模量低等特点,国外早已大力开展了对FRP材料的力学特性、加工工艺和结构性能研究,并将其用于钢筋混凝土结构,且在试验研究和工程应用等方面均取得了丰硕的成果.本文在对目前研究成果进行分析的基础上,主要介绍了国内外有关FRP筋的最新研究进展.     

基于BOTDA的土工格栅加筋膨胀土湿胀干缩特性试验

为了研究土工格栅加筋膨胀土湿胀干缩特性,制作了玄武岩纤维土工格栅加筋膨胀土和素膨胀土矩形槽试样,将传感光纤布设在土工格栅上和土层中,进行了湿胀干缩试验,利用布里渊光时域分析仪(BOTDA),得到素膨胀土和土工格栅加筋膨胀土试样在湿胀干缩过程中的光栅应变,对比分析两种土样应变分布特征。试验结果表明:在膨胀土湿胀干缩过程中,随着含水率的变化,加筋膨胀土平均应变变化量和变形小于未加筋膨胀土,反映了土工格栅对膨胀土体变形的约束作用和抑制裂隙发展的效果。     

FRP复合材料加固钢筋混凝土桥梁的分析探讨

从加固工艺的机理及分析计算方面,对FRP复合材料加固钢筋混凝土桥梁进行了分析与探讨,并对三种加固方法进行了分析比较,阐明了各自的加固特点,以推广表面嵌贴法与机械固定法在旧桥加固中的应用。     

碳纤维片材（CFRP）加固混凝土结构技术分析

介绍了CFRP加固技术的特点,分析了CFRP及其粘贴用树脂的材料特性,阐述了目前CFRP加固钢筋混凝土结构的常用加固形式,并对结构加固设计依据作出明确规定,以使结构加固更加合理。     

土钉墙及桩锚支护结构在复杂基坑支护中的应用

针对某基坑工程,综合对比各种支护形式及基坑的工程地质条件,并通过稳定性验算,确定基坑上部4.85m以1:0.7放坡并以土钉墙护坡,下部6m采用人工挖孔桩并以两排锚杆稳定桩体的形式支护,同时,采用信息化施工监测,对施工中出现的薄弱环节及时采取相应的补强措施,保证了基坑的安全及工期要求。     

软土地区基坑开挖监测的实践与应用

软土因其高含水量、高压缩性而工程性能差,给软土地区的基坑开挖提出了更高的要求。通过对某软土基坑开挖的监测实例,探讨了软土基坑开挖的全过程系统监测,及时反馈基坑及周边环境的变形情况,实现信息化施工,以保证基坑稳定和周边环境的安全。     

放坡竹筋土钉墙在软土地区的应用

放坡竹筋土钉墙作为一种新型支护结构形式,已成功地运用于开挖深度为5 m~6 m的软土地区基坑工程。文章分析了毛竹材料作为土钉在软土地区的适用性及放坡竹筋土钉墙的作用机理,总结了竹筋土钉墙的设计要点,结合实际工程案例,验证了该支护结构形式的适用性及合理性,推动了新型环保材料、新型支护技术在岩土工程中的应用,可供今后类似工程借鉴。     

Numerical investigation of reinforcement pullout resistance effects on behavior of geosynthetic-reinforced soil (GRS) piers

In this study, three-dimensional numerical analyses were carried out to investigate the effects of reinforcement pullout resistance including facing connection strength on the behavior of geosynthetic-reinforced soil (GRS) piers under a service load condition. Three different piers were investigated in this study, which simulated different levels of reinforcement pullout resistance. Each pier had two cases with different reinforcement stiffness J and reinforcement spacing S_v but the same ratio of J/S_v. Numerical results showed that reinforcement pullout resistance had a significant effect on the behavior of GRS piers. When the pullout mode prevailed, the case with small S_v and low J had smaller lateral facing displacements and vertical strain of the pier under the same applied pressure as compared to the case with large S_v and high J when the ratio of J/S_v was kept constant. When the pullout mode did not prevail, two cases with the same ratio of J/S_v showed similar performance despite different combinations of S_v and J were used. To more effectively mobilize reinforcement strength and improve GRS pier performance, small reinforcement spacing or high-strength facing connection should be considered when sufficient reinforcement pullout resistance cannot be guaranteed otherwise.     

钢筋混凝土在滨海盐土地区腐蚀规律试验研究

根据钢筋混凝土桩在天津大港腐蚀试验站进行大气土壤综合腐蚀八年的检测结果,论述了钢筋混凝土材料在盐土地区遭受腐蚀的特征、混凝土强度和中性化变化规律,环境土壤及混凝土中SO3含量分析结果表明,土壤中SO4^2-离子通过混凝土内毛细管进入到混凝土内部,干混作用部位的混凝土遭受化学腐蚀与盐类结晶侵蚀,腐蚀破坏比较严重。     

预应力格栅在加筋土挡墙中的应用与研究

结合湖南长沙潇湘大道上一路堤式加筋土挡墙,计算了不同筋材间距情况下相应的初始应变。同时计算了在相同条件下,未施加预应力与施加预应力墙面侧向位移的差异。研究表明:适当调整筋材间距和控制预张拉筋材初始应变是一种十分经济有效的方法。     

桥梁施工过程中软土地基的处理

本文对桥梁施工过程中的软土地基的处理方法进行了探讨,旨在提高施工效率的同时,尽量避免安全质量事故的发生。     

加筋土挡墙在建筑高边坡中的应用分析

本文详细介绍土工格栅加筋土挡墙在某一高陡建筑边坡中的应用,既节省了工程投资,又有效节约用地,获得较大的经济利益。     

桥梁施工过程中软土地基的处理

本文对桥梁施工过程中的软土地基的处理方法进行了探讨,旨在提高施工效率的同时,尽量避免安全质量事故的发生。