Development of prestressed geotextile-reinforced soil

预应力土工布加筋土的研制

基本信息

批准号：
07555150
负责人：
TATSUOKA Fumio
金额：
$ 4.61万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Since late 1980's, geotextile-reinforced soil method has been widely used for important structures as reraining walls and bridge abutments for reilways or highways in Jpana, resulting from its cost-performance ratio superior to that of conventional method using reinforced concrete (RC) structures supported by pile foundations. To make the new method spread more widely, however, it is necessary to make reinforced soil structures much stiffer against vertical compressive load and to give them high stability and stiffness not significantly lower than those of RC structures. For that purpose, a new method called 'preloaded and prestressed (PLPS) reinforced soil method' was invented. In the method, a well compacted geotextile-reinforced soil embankment using well graded gravel as the backfill is vertically compressed on its reinforced area by using several tie rods. First, the reinforced backfill is preloaded at the load level about twice as large as that of the design load to be deformed b … More y creep. Second, the backfill is unloaded to the load level about the same as the design load. Finally the top ends of the tie rods are fixed to the reaction block on the top of the backfill to make the system in a prestressed condition. The structure is used as a bridge abutment or pier under that condition.In this study, loading tests and detailed measurements were performed on a full scale model embankment and a prototype railway bridge pier, which were constructed by the PLPS reinforced soil method. In addition, large scale triaxial compression teats were preformed on the fill materials (well graded gravels). The feasibility and mechanisms were examined based on the results, and the method for quantitative prediction of the deformation and the design method for PLPS reinforced soil structures were developed. The major conclusions are as follows.a) Large prcload can be applied because the soil is reinforced. The preloading makes the soil nearly elastic and stiff. In addition, preloading on the soil introduces tensile prestress in the geptextile arranged horizontally, which confines the backfill in the horizontal direction.b) High vettical prestress gives the backfill higher, vertical and compressive stress condition, therefore the soil shows higher stiffness against vertical load.c) Sufficinet creep deformation which occurs during preloading results in a suppression both of the creep deformation and the decrease in the tie rod tension when a vertical load lower than the preload level is applied.d) When vertical compressive load is applied on top of the structure, the amount of increase in the load which works on the backfill decrease because the tie rod tension decreases by compression of the backfill. Less

自 20 世纪 80 年代末以来，土工布加筋土法已广泛应用于日本铁路或高速公路的挡土墙和桥台等重要结构，其性价比优于采用钢筋混凝土 (RC) 结构支撑的传统方法。然而，为了使新方法得到更广泛的推广，有必要使加筋土结构具有更大的抗垂直压缩载荷的刚度，并使其具有不明显低于传统方法的高稳定性和刚度。为此，发明了一种称为“预载和预应力（PLPS）加筋土法”的新方法，在该方法中，使用级配良好的砾石作为回填物，在其加筋上垂直压缩压实的土工布加筋土路堤。首先，通过使用多个拉杆对加固回填物进行预加载，其荷载水平约为设计荷载的两倍，以便因蠕变而变形。最后将拉杆顶端固定在回填土顶部的反力块上，使系统处于预应力状态，作为桥梁使用。本研究对采用 PLPS 加筋土法建造的全尺寸模型路堤和原型铁路桥桥墩进行了加载试验和详细测量，此外还进行了大型三轴压缩试验。根据结果检验了填充材料（良好级配砾石）的可行性和机理，并开发了 PLPS 加筋土结构的变形定量预测方法和设计方法，主要结论如下。 a) 可以施加大的预载，因为预载使土壤接近弹性和刚性。此外，对土壤的预载会在水平布置的土工织物中引入拉伸预应力，从而限制回填土。 b) 高垂直预应力使回填土具有较高的竖向压应力条件，因此土壤对竖向荷载表现出较高的刚度。 c) 预压过程中发生的足够的蠕变变形会抑制蠕变变形和蠕变变形。当施加低于预载水平的竖向荷载时，拉杆张力的减小。d) 当在结构顶部施加竖向压缩荷载时，由于拉杆的存在，作用在回填土上的荷载增加量减少回填材料的压缩会降低张力。