Reinforcement for Upgrading Earth Structures Using Geocomposites under Cyclic Loading

本研究旨在探索一种利用两种或三种不同的土工合成材料组合而成的土工复合材料来加固交通、海浪和地震等循环荷载作用下的土工结构的方法。本研究的关键词是“Hybrid”和“Sandwich”，包含以下两个方面：1)本研究使用的材料是一种杂交材料，即非织造土工合成材料与类似于三明治的编织土工合成材料相结合。ii)在土工复合材料的上下两侧放置砂垫。这种类型的土质结构可称为混合夹层土质结构。为了实现混合土工合成材料混合土工结构的优势，进行了模型试验和数值分析。主要研究结果如下：1)在土工合成材料之间放置砂垫形成的夹层结构对软土的改善作用比只放置砂垫而不添加土工合成材料的情况更为显著。2)砂席与土工合成材料复合形成夹层结构，提高了土工合成材料的渗透性和透性。将编织的土工合成材料夹在编织的土工合成材料中间的土工复合材料最适合实现这一目的。3)夹层结构的优势体现在两个方面：一是增加了路堤的稳定性，减少了路堤的变形和沉降。4)编制了考虑土工合成材料约束对夹芯结构路堤变形和稳定性影响的有限元计算程序。5)提出了在夹层结构中注入水泥砂浆的复合加固方法，是一种很有前途的地基与土方结构复合加固方法。特别是在交通、海浪和地震的循环荷载作用下，该系统能有效地提高稳定性，减少沉降。6)无论是使用土工合成材料，还是将无纺布土工合成材料与注入水泥砂浆相结合，都可以在受海浪作用的沿海地区建立稳定的加固护岸。少

The present study aims at exploring a reinforcing method for upgrading earth structures under cyclic loading induced by traffic, ocean waves and earthquakes by using geocomposites which are manufactured by combining with two or three different kinds of geosynthetics. The keyword in this study is "Hybrid" and "Sandwich" which contains the following two aspects :I) The material used in the study is a hybridized one in which the unwoven geosyntheitc is combined with the woven geosynthetic similar to the sandwich.ii) Sand mat is placed at the both sides, above and beneath the geocomposite. This type can be called a hybrid-sandwich earth structure., In order to accomplish the advantageous aspects of the hybrid earth structure with the hybrid geosynthetic, model tests and numerical analysis were carried out. The following main findings were derived from the present study :1) Sandwiched structures formed by sand mat placement in-between geosynthetics contribute to improvement of soft soils mo … More re markedly than in the case with sand mat only without geosynthetic reinforcement.2) Sand mat placement combined with geosynthetics as a sandwich structure gives rise to improvement of permeability and transmssibity of geosynthetics. The geocomposite in which the woven geosynthetic is sandwiched by the woven geosynthetic in-getween is most suitable for accomplishing this purpose.3) Advantages of sandwiched structures are recognized in the two aspects : the one is increase of stability of embankment and decrease in deformation and settlements of embankment.4) The finite element computer code is formulated to consider the effect of confinement due to geosynthetics into deformation and stability of embankment with the sandwich structure.5) Anew method combined by injecting cement mortar into send mat in the sandwich structure is suggested as a promising hybrid system for upgrading foundations and earth structures. In particular, this system is effective to increase stability and reduce settlements under cyclic loading induced by traffic ocean waves and earthquakes.6) Either the use of geocomposite or the combination of non-woven geosynthetic with injection of cement mortar gives rise to stable reinforced revetments at the coastal area subjected to ocean wave actions. Less