格栅条带式加筋胎面挡土墙变形性能数值计算

采用土工格栅加筋的方法提高废旧轮胎挡墙的承载性能,促进废旧轮胎挡墙的推广应用,通过数值计算方法分析了不同墙顶荷载下有无土工格栅加筋的废旧轮胎挡墙的水平变形与竖向沉降反应特征,得出铺设土工格栅加筋的方法可显著减小墙体的水平变形和竖向沉降,提高废旧轮胎挡墙结构的承载能力,随着外荷载的增加,墙体变形模式依次呈凹凸微小变化型、“弯弓”型、“似弯弓”型和“鼓腮”型和直线型。考虑土工格栅的加筋长度、竖向加筋间距以及格栅加筋刚度3种因素对废旧轮胎+土工格栅加筋土挡墙的水平变形的影响,得出在废旧轮胎加筋土挡墙设计中,建议土工格栅的加筋长度选取范围为0.5H～0.7H,土工格栅竖向间距的选取范围为0.4 m~0.7 m,格栅刚度不宜大于5 000 kN/m。     

基于正交设计方法的加筋土挡墙侧向变形影响因素敏感性分析

以某座玻璃纤维土工格栅加筋土挡墙为依托,基于正交设计的科学方法,利用大型有限差分软件FLAC3D对该加筋环挡墙进行数值计算,得到了侧向水平位移沿挡墙高度方向的分布规律,计算结果表明,填料摩擦角、筋材间距、面板厚度、加筋长度对加筋土支挡结构侧向水平位移的影响程度依次递减;最大侧向位移值随加筋长度、面板厚度、填料内摩擦角增大而减小,随竖向加筋间距的增加而递增。研究成果可为加筋土挡墙设计及后续研究提供一定参考。     

基于ABAQUS有限元的土工格栅加筋路堤边坡稳定性研究

运用通用ABAQUS有限元程序,结合某路堤断面对路堤加筋效果进行数值模拟,研究在交通荷载下土工格栅加筋作用对路堤稳定性的影响.采用拟静力法,分析路堤在加筋、未加筋两种情况下的路堤边坡稳定性.研究表明:在简化交通荷载下,加筋不仅可提高路堤稳定安全系数,有效减少路堤侧向位移,并能极大缓解路堤边坡在超过临界状态时产生的位移突变情况,通过计算得到路堤合理加筋层间距为1m.     

返包式加筋土挡墙的数值模拟研究

返包式加筋土结构由于重量轻,成本低,基础适应性强,已被广泛应用于公路、水运、水利、铁路等各类土建工程的支挡结构中。文章采用FLAC3D数值计算软件,研究一个22 m高的返包式加筋土挡墙,其上部为8 m高的未加筋路肩,下部为14 m高的土工格栅加筋路堤。研究发现,加筋前后挡墙的侧向变形均呈现沿坡面中部向结构内部逐渐减小的趋势,出现明显的"鼓肚";在挡墙中铺设土工格栅能够显著降低路基的侧向变形;筋带可以改善挡墙内部剪应力分布,筋土之间的传递分散作用能够减少剪应力集中;采用强度折减法对未加筋挡墙和加筋挡墙的安全系数进行求解,发现加筋后挡墙稳定性明显提高。     

土工格栅加筋石灰土挡墙工程特性试验研究

以河北省保（定）沧（州）高速公路模块式土工格栅加筋石灰土挡墙为工程依托,以现场原型试验为手段,系统研究了该结构工作状态下的基底竖向土压力、墙面板背部侧向土压力和土工格栅拉筋应变分布规律。试验结果表明：基底竖向土压力沿筋长近似呈梯形分布,其大小一般小于理论值,最大值发生在墙背附近,且随竣工后时间的延续有下降的趋势;实测墙背侧向土压力沿墙高呈非线性增长分布,数值小于主动土压力;实测拉筋应变沿筋长呈单峰值分布,且数值均小于0.6%。试验结果可以为类似工程的设计、研究提供参考。     

土工格栅加筋土地基载荷试验的数值模拟

采用FALC^3D对土工格栅加筋土地基载荷试验进行了进一步的数值模拟分析。根据计算结果,针对原型试验中难以量测的试坑变形及筋土界面摩阻力分布特征进行了讨论。利用数值模拟技术的优势,求解加筋地基的应变场,研究了加筋地基的破坏模式。结果表明:在竖向荷载作用下,试坑会发生侧向位移,通过加筋能有效减小试坑的侧向位移;筋土界面摩阻力的分布与筋土之间的相对位移直接相关;加筋地基的破坏机构因筋材的存在而发生改变,“深基础”效应以及“扩散层”效应都是加筋地基的增强机理,但地基的破坏模式随筋材的布置形式改变而有所不同。     

加筋垫层路堤有限元分析

结合工程实例,采用有限元软件Plaxis,分析了土工格栅加筋和未加筋时的稳定性和变形情况,计算结果表明,在路堤底部设置土工合成材料加筋垫层可以减小路基的沉降、不均匀沉降及侧向位移,提高路堤的整体稳定性。     

土工格栅加筋高路堤与超载预压排水固结非线性有限元分析

土工格栅是一种常用的路堤加筋材料,可有效地减少路堤沉降和侧向位移。超载预压排水固结是常用的地基处理方法。采用DP模型模拟土体的非线性、面—面接触单元考虑筋、土界面的非线性,并由若干个桁架单元通过在与土接触点处铰接连接来模拟土工格栅,通过有限元程序分析了加筋前后高路堤的竖向位移和侧向位移。从计算结果显示出,对于填筑高度在10~15 m左右的高路堤,加筋路堤能有效减少竖向位移20%,减少侧向位移50%,并较填筑高度为5 m左右的加筋路堤对减少路堤竖向位移与水平位移的效果显著。分析结果与实测结果基本吻合。     

粉煤灰加筋路堤模型试验研究

为充分利用粉煤灰这一工业废物,探讨了土工格栅加筋机理,对无筋、一层加筋、二层加筋的粉煤灰路堤进行了室内模型试验,模拟现场加筋路堤的变形情况,定性测定了在试验过程中所施加的竖向压力P与坡顶沉降值S的关系曲线;在模型路堤的不同位置布置测试点,量测加筋路堤在荷载作用下各测试点位移情况,内部应力分布、发展情况,定性分析了加筋路堤内部的变形性状,为粉煤灰加筋路堤的应用提供指导。     

土工格栅加筋土挡墙侧向位移控制分析

以山东省某高速公路高密段土工格栅加筋土挡墙为工程背景,采用理论分析与数值模拟相结合,对土工格栅加筋土挡墙侧向位移控制进行优化分析,为类似工程提供借鉴与参考。可得以下结论:1加筋土挡墙变形模式为中部位移大、两头位移小的鼓状变形;2土工格栅与路基填料相互摩擦,有效改善了竖向土压力的分布;3土工格栅拉筋所受最大拉力随着填筑高度的增大的先增大后减小,格栅轴力最大值与挡墙鼓出变形的不利位置相一致。     

静动载下筋材变化对加筋土挡墙性能影响分析

为了研究动静荷载下,加筋长度及筋材类型变化对加筋土挡墙工作性能的影响,进行了7种工况下的加筋土挡墙模型试验,对比分析了加筋土挡墙的水平土压力、水平土压力系数、墙面水平位移和加载板竖向沉降及筋材应变等参数的发展规律。试验结果表明:动载下加筋土挡墙筋材应变随着加载时间的增长、加筋长度的减小、位置高度的增加而增大,且顶层筋材应变远远大于其他层;加筋长度及筋材横肋的减少明显降低挡墙的承载性能,格栅横肋减少导致挡墙极限承载力降低18% ,加筋长度减少使面板水平位移最大增大了2.2倍;与静载作用下相比,动载下土工格栅的侧向约束作用及网兜效应能够得到更好地发挥。     

Behaviour of geogrid reinforced soil retaining wall with concrete-rigid facing

Monitoring was carried out during construction of a cast-in-situ concrete-rigid facing geogrid reinforced soil retaining wall in the Gan (Zhou)-Long (Yan) railway main line of China. The monitoring included the vertical foundation pressure and lateral earth pressure of the reinforced soil wall facing, the tensile strain in the reinforcement and the horizontal deformation of the facing. The vertical foundation pressure of reinforced soil retaining wall is non-linear along the reinforcement length, and the maximum value is at the middle of the reinforcement length, moreover the value reduces gradually at top and bottom. The measured lateral earth pressure within the reinforced soil wall is non-linear along the height and the value is less than the active lateral earth pressure. The distribution of tensile strain in the geogrid reinforcements within the upper portion of the wall is single-peak value, but the distribution of tensile strain in the reinforcements within the lower portion of the wall has double-peak values. The potential failure plane within the upper portion of the wall is similar to “0.3H method”, whereas the potential failure plane within portion of the lower wall is closer to the active Rankine earth pressure theory. The position of the maximum lateral displacement of the wall face during construction is within portion of the lower wall, moreover the position of the maximum lateral displacement of the wall face post-construction is within the portion of the top wall. These monitoring results of the behaviour of the wall can be used as a reference for future study and design of geogrid reinforced soil retaining wall systems.     

软土地基加筋土挡墙数值模拟及稳定性探讨

 对一软土地基加筋土挡墙建立二维数值模型,模拟其在分级堆载情况下挡墙和地基内的沉降、水平位移、土压力,以及土工格栅轴向应变的变化规律,模拟结果与现场实测结果基本吻合。采用有限元强度折减法计算的挡墙稳定性和滑裂面位置与实测情况一致,表现为深层滑动失稳。模拟和实测的各层筋材最大应变出现在距墙面4～6 m的位置,与目前土工合成材料加筋挡墙设计理论的朗肯破坏面位置不同,其原因是目前的挡墙设计理论基于刚性地基假定,未考虑地基变形对筋材应变分布及稳定性的影响。采用该数值模型探讨加长挡墙底部筋材对其稳定性的影响,得出挡墙稳定性与底部筋材加长长度和层数关系密切。得到的挡墙稳定性与筋材加长长度和层数的关系曲线,对于软土地基加筋土挡墙设计有指导意义。     

土工格栅加筋挡土墙支护性能敏感参数分析

对某工程土工格栅加筋挡土墙支护结构采用分离式有限元法建立模型,对加筋挡土墙进行计算,对影响加筋挡土墙工作性能的填土性质、加筋间距、加筋长度和筋材弹性模量等敏感参数进行分析,通过计算并和实际监测数据进行对比分析,得出其侧向变形敏感参数对其侧向变形的影响规律,为相关工程土工格栅加筋挡土墙的设计和施工提供参考依据。     

土工格栅加筋土挡墙现场试验分析

通过埋设水平土压力盒、柔性位移计,对模块式土工格栅加筋土挡土墙墙后的水平土压力和格栅水平变形进行了系统监测,采用加筋组合法对加筋土挡墙的土压力进行了计算,与实测、交系数法所得数据对比分析,得出采用该方法计算的土压力更能合理地解释工作状态下加筋土挡墙的土压力分布规律;对比分析了施工阶段和竣工后格栅的应变,得出拉筋应变主要发生在施工阶段,工后应变较小,并结合试验结果,提出了关于施工控制的相关建议.     

暴雨条件下自嵌式加筋挡土墙稳定性数值模拟分析

结合具体工程,对暴雨条件下自嵌式加筋挡土墙存在的变形、受力特征和稳定性进行了有限元数值模拟,并与一般气候条件下进行对比。结果表明:在暴雨条件下,墙体将产生较大的侧向变形;墙背土压力在加筋处明显增大;挡土墙内部筋材之间局部出现拉应力区,筋材断裂后拉应力区明显扩大,存在墙面倾覆的趋势。该结论在对特大暴雨后加筋挡土墙局部破坏事故的现场调查后得到了验证。     

Static structural behavior of geogrid reinforced soil retaining walls with a deformation buffer zone

To understand the structural behavior of geogrid reinforced soil retaining walls (GRSW) with a deformation buffer zone (DBZ) under static loads, the model tests and the numerical simulations were conducted to obtain the wall face horizontal displacement, vertical and horizontal soil pressures, and geogrid strains. Results showed that compared with the common GRSW, the horizontal displacement of GRSW with DBZ decreased, and the horizontal soil pressure acting on the face panel of GRSW with DBZ increased. The vertical and horizontal soil pressures showed a nonlinear distribution along the reinforcement length, and the value was smaller near the face panel. The horizontal soil pressure acting on the face panel of GRSW with DBZ was greater than that of the common GRSW in the middle portion. The cumulative strain of the geogrid had a single-peak distribution along its length; the maximum strain of the geogrid was 0.45%, the maximum tension was approximately 29.12% of ultimate tensile strength.     

Post-construction performance of a two-tiered geogrid reinforced soil wall backfilled with soil-rock mixture

There have been very few studies on the application of soil-rock mixtures as the backfills of geogrid reinforced soil retaining walls with due concern for their long-term performance and safety. In this study, a 17-m high two-tiered reinforced soil wall backfilled with soil-rock mixture was instrumented for its performance under gravity load after construction. The instrumentation continued for 15 months. It is found that soil-rock mixtures with small rock content (<30%) have the potential to be used as the backfill materials of geogrid-reinforced retaining walls, but special attentions should be given to compaction quality, backfill–geogrid interaction, and installation damage to geogrids. Reinforcement slippage is possible because of the large particles, but it was small in this case and ceased to develop nine months after the end of construction. Compressibility difference between reinforced and unreinforced backfill might led to rotation of the upper tier. Using the estimated soil strength, the predictions of reinforcement loads by the FHWA methods were 100% higher than the estimated ones from measured strains.