A research of failure mechanism of tropical expansion soil in Africa and its countermeasure of symbiosis with nature

泥灰岩是一种热带膨胀土，广泛分布于非洲赤道地区，在岩土工程领域具有体积变化的特点。在雨季，泥岩体积增大，而在旱季，泥岩体积减小。由于下部建筑物的自重不具有抗膨胀压力的承受能力，因此收缩和膨胀引起的变形引起微分沉降和膨胀。通过对达喀尔周边地区的实地调查，从建筑物类型、建筑物破坏类型和地质条件三个方面对影响因素进行了分析。此外，还从达喀尔的严重受损地区收集了样本。为了了解Marl的物理力学性能和微观结构，将样品运往日本并在日本进行实验室测试。根据试验结果，详细分析了灰岩的主要特征。由于灰泥的力学特性随含水量的变化而变化，在不同含水量条件下进行了室内试验。研究了高含水率条件下强度和膨胀特性的降低以及排水条件下强度和膨胀特性的恢复。本研究的实际目的是建立在达喀尔地区利用土袋提高地基刚度的施工方法。为了证实土袋作为地基改良方法（Solpack-method）的有效性，采用土袋进行了各种试验。在实验结果的基础上，研究了solpack方法的适用性，并进行了数值模拟。通过一系列的研究，提出并建立了solpack法的设计标准和设计手册。为了在达喀尔地区应用solpack方法，在达喀尔市与达喀尔地区的行政工程师、建筑商、研究人员和达喀尔大学的Fall教授举行了技术会议。针对达喀尔地区的研究人员和工程人员，提出了一种详细适用于不同地区的solpack方法。未来，这些地区的研究人员有望开发出适合当地的详细设计手册。少

A kind of tropical expansion soil : Marl that widely spread in equatorial area of Africa has a feature of volumetric change in geotechnical field. The volume of Marl increase due to high moisture in rainy season, on the other hand the volume is reduced in dry season. As the weights of lower building do not have bearing resistance against swelling pressure, the deformation caused by shrinkage and expansion invoke differential settling and swelling. From the field investigations around Dakar, factors are investigated based on the type of building, type of damage for building and geological condition. In addition, samples are collected from the major-damaged area in Dakar. In order to understand the physical and mechanical properties and microstructure of Marl, the samples were shipped to Japan and laboratory tests were carried out in Japan. From the results of those tests, the main features of Marl is investigated in detail. As the mechanical feature of Marl changed with water content, l … More aboratory tests were conducted under various water contents. The reduction of strength and the swelling character in high water content condition andtherecovery of strength and swelling character under drainage condition are studied in the research.The practical goal of this research is to establish the construction method to improve the ground stiffness using soil bag in Dakar area. In order to confirm the effectiveness of soil bag as the ground improving method (Solpack-method), various tests using soil bag were conducted. Based on the experimental results, the applicability of Solpack-method is investigated and numerical simulations are carried out in addition. From a series of research, a standard and a manual for design of Solpack-method is proposed and established.In order to apply the Solpack-method in Dakar area, technical meetings are held in Dakar city with engineers of administration, builders, researchers in Dakar area and Professor Fall of Dakar University. Solpack-method, which is established to apply for various local regions in detail, is proposed for researchers and engineers in Dakar area. It is expected to develop the detail manual of design for local area by the researchers in those areas for the future. Less