土工格室处理高填方新旧路堤施工技术

结合山区公路改扩建工程,指出山区高填方新旧路堤容易出现不均匀沉降等问题,根据数值分析结果和现场实际情况,提出采取土工格室处理方案,重点分析了现场施工控制方法与检测标准,并进行了现场新旧路堤搭接段深层侧向位移和沉降观测数据分析.结果表明,严格控制现场施工质量,可保证土工格室所在结构层发挥立体加筋效果,有助于提高新旧路堤的搭接稳定性,降低新旧路堤的不均匀沉降.     

土工格室加筋砂土地基沉降试验研究

土工合成材料可以有效提高地基的承载力与减小地基的表面沉降差异。在静荷载作用下,采用室内模型试验方法对纯砂地基和土工格室加筋地基的地基承载力和沉降情况进行了对比分析,研究了格室埋深、格室高度及筋材层数对距离基础不同远近处地基沉降的影响。研究结果表明,在荷载较小时,土工格室加筋地基作用效果相近;在荷载较大时,土工格室加筋效果提高显著;土工格室加筋地基不仅有效控制了基础沉降,而且减小了基础附近地基的沉降差异;筋材调节地基不均匀沉降的加筋效果随筋材埋深减小、筋材层数增加、格室高度增加而有不同程度的提高。     

应用土工格室处治路基不均匀沉降

在分析路基不均匀沉降成因的基础上,通过对现有路基不均匀沉降处治措施的分析与评价,提出了土工格室处治路基不均匀沉降的方法,研究表明,土工格室复合体限制了周围土体的侧向变形,减小了路堤本身的压缩变形,是处治路基不均匀沉降的一种有效方法.     

条形荷载下土工格室加筋砂土路堤模型试验研究

为了探讨不同土工格室加筋方式对路堤应力变形特性和不均匀沉降的控制效果,分别对纯砂路堤边坡和土工格室加筋路堤进行多组模型试验,研究了土工格室焊距、埋深、加筋层数以及压实度对路堤承载力特性和变形特性的影响,同时结合土工格室材料应变的变化规律和加筋路堤的坡面变形状态分析了土工格室加筋路堤的破坏模式。试验结果表明:格室加筋效果随着焊距、加筋深度的减小而增加,随着压实度、加筋层数的增加而增加;土工格室加筋路堤承载力是纯砂的2.5倍左右,提高了路堤的极限承载力,减小了路堤沉降,并且土工格室加筋路堤坡面侧向位移比纯砂路堤减小了75%。     

土工格室处理高速公路拓宽部有限元分析

为研究三维柔性结构———土工格室加固路基拓宽部的效果,运用ABAQUS有限元软件,采用基于Coulomb定律摩擦模型模拟土工格室复合板体及其填料的非线性接触,模拟分析铺于新老路基结合处底层不同宽度、伸入老路基不同深度的土工格室时的路基顶面的竖向位移、侧向位移和相对差异沉降等。结果表明:土工格室的铺设使路基内应力分布趋于均匀,有效地协调新老路基的不均匀沉降,但加固效果并不随铺设格室的宽度、伸入老地基的深度而成线性增加。     

考虑填料–土工格室相互作用的加筋路堤力学响应研究

针对有砟轨道加筋路堤计算分析中难以考虑土工格室对碎石填料嵌锁及摩擦作用的现状,在大比尺直剪试验基础上建立考虑填料–格室相互作用的三维计算模型。通过室内模型试验验证该计算的可靠度和优越性,进而系统地分析有/无加筋情况下,填料强度、土工格室刚度及地基压缩性等参数对路堤力学响应的影响。结果表明:土工格室的嵌锁作用使得加筋对路堤响应的影响在其布设层发挥程度更大,该影响通过填料与格室及填料内的摩擦作用向周围传递且不断衰减;填料强度较低或地基较软时能加强土工格室对路堤响应的影响,对于填料内摩擦角为20°和地基变形模量为5 MPa的工况而言,加筋后基床侧向位移峰值分别降低60%和72%,应力峰值亦显著降低且分布区域明显扩大;土工格室弹性模量为0.2~2.5 GPa时,路堤力学响应受其影响较大。     

土工格室对路堤沉降影响的有限元分析

通过研究土工格室如何对软土路堤进行加筋,并且应用ANSYS有限元软件来数值模拟土工格室增强土体的强度。通过添加土工格室前后情况对比,改变土工格室的添加层数进行分析,研究了铺设土工格室对软土路堤的沉降影响以及最优的铺设层数。结果表明,添加土工格室能限制路堤的沉降,使土体稳定性整体提高。     

轮胎与格室加筋路堤性能及承载力研究

为研究废旧轮胎与土工格室加筋路堤边坡的性能,分别对废旧轮胎、土工格室加筋路堤边坡开展了室内模型试验,并考虑了填料两种不同相对密度的影响。试验结果表明:相对素土路堤而言,废旧轮胎和土工格室加筋路堤均能有效地提高承载力,增强其稳定性,减小不均匀沉降。加筋后均有效地增大了附加应力的扩散角,使得附加应力分布更为均匀,并且素土路堤与加筋路堤中轴线上附加应力差值随路堤深度增大而减小。中轴线以外的质点侧向位移随路堤深度的增加,呈现出先增大后减小的趋势,几种路堤中,废旧轮胎加筋路堤侧向位移最小。加筋效果随相对密度增大而减小,在低相对密度条件下,加筋后承载力能达到素土路堤2倍以上,而在高相对密度下却不足2倍。最后根据土工格室加筋地基承载力计算方法及对废旧轮胎加筋机理分析,提出了关于废旧轮胎加筋地基承载力计算方法。     

土工格室于砂土之承载能力及动态特性试验研究

在沙漠地带中,在路基材料缺乏的状况下,利用土工格室与现场砂土可有效提高沙漠道路的承载力,并能达到经济效益与路基的设计要求。为了解土工格室于砂土路基的加筋行为,分别进行了静态承载板载重试验与动态载重试验,探讨土工格室加筋后的承载能力与动态特性。与未加筋砂土比较,土工格室发挥良好之加筋效果,其能提高砂土的承载能力;于静态承载试验中,承载能力随着土工格室高度增加而提升,并有效减少沉降量之产生。在动态试验指出,土工格室加筋于砂土受动态反复作用下,增加土工格室高度,并不相对能提升加筋的承载成效。以动态载重试验反应公路的反复载重条件,对于沙漠公路设计使用土工格室加固路基时,得以选择具有经济效益的优化方案。     

炉渣加筋的大型直剪试验研究

炉渣为城市生活垃圾焚烧后的产物,具有砂性材料类似的性质,可作为路基填料。通过大型土工直剪仪分别对纯炉渣、双向土工格栅与炉渣加筋、土工格室与炉渣加筋在不同垂压下进行直剪试验,对比几种筋材的加筋效果,并研究分析其加筋机理。试验结果表明:炉渣加筋的抗剪强度明显大于纯炉渣的抗剪强度,筋材的加筋效果显著;土工格室加筋效果优于双向土工格栅,加筋后的内摩擦角与纯炉渣基本接近,而黏聚力提高显著,炉渣加筋主要是通过提高黏聚力提高抗剪强度。     

Experimental study of embankments with different reinforcement materials and spacing between layers

Worldwide, waste tires are being discarded in landfills at a huge environmental cost, therefore, their use as a three-dimensional reinforcement material is a wise solution to reduce their environmental impact, and fire risk in the case of shredded tires. In this research a series of experimental model tests of embankments reinforced with Geocell and tires were conducted to compare the performance of these types of reinforcement. The models tested had different Geocell embedment depths, number of Geocell layers, vertical spacing between Geocell layers and density or soil stiffness. Testing consisted of applying pressure at the crest of the embankment and monitoring the pressure distribution, as well as the vertical and horizontal deformations inside of the embankment. The results suggested that when compared with unreinforced embankments, reinforced embankments effectively improve the bearing capacity, thereby, reducing vertical and lateral displacements. This study also showed that an optimal embedment depth and spacing between Geocell reinforcement layers can further improve the slope performance. Comparisons between Geocell reinforced embankments and waste tire reinforced embankments, showed that waste tire reinforcement has a superior performance over the Geocell-reinforced embankments. This difference in performance between the two types of reinforcement is more apparent if the embankment backfill has lower stiffness. i.e. lower density.     

Combined effect of PVDs and reinforcement on embankments over rate-sensitive soils

A numerical study of the behavior of geosynthetic-reinforced embankments constructed on soft rate-sensitive soil with and without prefabricated vertical drains (PVDs) is described. The time-dependent stress–strain-strength characteristic of rate-sensitive soil is taken into account using an elasto-viscoplastic constitutive model. The effects of reinforcement stiffness, construction rate, soil viscosity as well as PVD spacing are examined both during and following construction. A sensitivity analysis shows the effect of construction rate and PVD spacing on the short-term and long-term stability of reinforced embankments and the mobilized reinforcement strain. For rate-sensitive soils, the critical period with respect to the stability of the embankment occurs after the end of the construction due to a delayed, creep-induced, build-up of excess pore pressure in the viscous foundation soil. PVDs substantially reduce the effect of creep-induced excess pore pressure, and hence not only allow a faster rate of consolidation but also improve the long-term stability of the reinforced embankment. Furthermore, PVDs work together with geosynthetic reinforcement to minimize the differential settlement and lateral deformation of the foundation. The combined use of the geosynthetic reinforcement and PVDs enhances embankment performance substantially more than the use of either method of soil improvement alone.     

A reinforcing method for steep clay slopes using a non-woven geotextile

The effect of non-woven geotextile reinforcement on the stability and deformation of two clay test embankments is examined based on their performance for about 3 years for the first embankment and about years for the other. Horizontal planar sheets of a non-woven geotextile are expected to work in three ways: for compaction control; for drainage; for tensile reinforcement. The degree of stability of the steep slopes of the test embankments decreased during heavy rainfall. It is found that the use of non-woven geotextile reinforcement may effectively improve embankment performance. Only the stability analysis in terms of effective stresses can explain the performance of the test embankments. The horizontal creep deformation of the embankments during 2–3 years, which is partly attributed to the creep deformation of the non-woven geotextile, was found to be small. The results of both laboratory bearing capacity tests of a strip footing on a model sand ground reinforced with the non-woven geotextile and plane strain compression tests on sand specimens reinforced with the non-woven geotextile show that the non-woven geotextile gives tensile reinforcement to soils.     

基于监测数据的加筋高填路堤分层填筑变形特性分析

在高填路堤建设中,铺设土工格栅对沉降的影响一直是关注热点之一。结合云罗高速公路高填路堤建设,本文采用数值方法模拟了分层填筑路堤施工过程的沉降规律,并结合监测数据,探讨了高填路堤加筋土在沉降控制方面的基本规律。结果表明:高填路堤填土过程中,土工格栅使土体位移重新分布。水平位移和垂直位移均减小了,这在一定程度上防止了不均匀沉降,且土工格栅对水平位移的影响随着填土厚度的增加而加大。同时,在典型路堤加筋土分层填筑过程中,单向土工格栅降低水平位移幅度为8.74%,而降低沉降幅度为3.82%。在分层填筑过程中,筋材有效地控制了路堤的不均匀沉降,使路堤最大沉降值降低,且监测点的水平位移最大降幅分别为8.62%、8.38%和4.16%。     

衡重式加筋土路肩挡墙土工离心模型试验研究

以某山区公路旧路拓宽改造工程中新建的衡重式加筋土路肩挡土墙为原型,设计了4组模拟墙体实际位移形态的土工离心模型试验,讨论了墙后土体压实度和土中加筋对墙背土压力和路基填土变形的影响规律。试验表明：①墙后土体加筋对减小墙背承受的土压力作用随填土压实度的提高而趋于明显,主要影响区域位于上墙背的下半部分,压实度由88%增至95%会引起上墙背土压力分布由近似线性增大演化为折线型变化;②衡重台对其上覆填土存在托举效应,致使下墙背的土压力大幅减小,其影响范围约为衡重台以下约1/3下墙高度;③墙后土体加筋能提高路基填土的抗变形能力,减小因墙体侧向位移引起的填土表面下沉,对降低新旧路基间的不均匀变形效果显著。     

Effect of basal reinforcement on performance of floating geosynthetic encased stone column-supported embankment

In this paper, two centrifuge modeling tests were performed to investigate the influence of basal reinforcement on the global performance of floating geosynthetic encased stone column (GESC)-supported embankments. Based on the centrifuge tests, a 3-dimensional (3D) numerical modeling was carried out to investigate the influence of basal reinforcement on the deformation behavior of the floating GESC-supported embankment. The centrifuge and numerical modeling results showed that the basal reinforcement reduced total and uneven settlement at the embankment crest and base significantly. Moreover, the inclusion of the basal reinforcement significantly reduced the lateral displacement on top of the column, preventing outward bending of the floating GESCs below the embankment toe. However, the basal reinforcement increased the lateral displacement at the bottom of columns.     

软基上加筋防波堤的离心模型试验

通过离心模型试验，研究在有无土工织物加筋垫层条件下防波堤和软基的变形性状，得到了地基沉降、隆起及水平位移的分布规律。提出了一种量测筋材张力的新方法，对土工织物在离心试验过程中的应力状态进行了测试。研究结果表明：土工织物加筋垫层能有效地减小地基的侧向位移，有一定的加筋效果：土工织物张力的发挥水平与堤坝的沉降量密切相关，工作状态下其最大强度发挥水平约为52％。     

Use of cellular confinement for improved railway performance on soft subgrades

Due to extensive right-of-way, railroads are inevitably subject to poor subgrade conditions and interrupted service for significant maintenance due to excessive deformations and loss of track geometry. Geocell confinement presents itself as a possible solution for improving performance of ballasted railroad embankments over weak subgrade. To investigate the efficacy of geocell confinement on ballasted railway embankments, a set of well-instrumented, large-scale cyclic plate loading tests and numerical simulations were performed on geocell-confined ballast overlaying a weak subgrade material. The agreement of results from tests and simulations served as a basis for simulating practical track geometry and performance for various geocell configurations and subgrades using three-dimensional (3D) finite element (FE) analyses. The study showed that geocell reinforcement significantly decreased track settlement, decreased subgrade deformations with lower and uniform distribution of vertical stresses on subgrade and inhibited lateral deformation and serviceability under cyclic loading. These results demonstrate that geocell confinement can be an effective alternative to subsurface improvement or shorter maintenance cycles, particularly on weak subgrades.