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Assessment of the Internal Instability for Granular Soils Subjected to Seepage

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Journal of Geoscience and Environment Protection 2016年第6期4卷 46-55页

作者： marx ferdinand ahlinhan Marius Bocco Koube Codjo Edmond Adjovi Ecole des Sciences et Techniques du Batiment et de la Route (ESTBR) Université Polytechnique d’Abomey (UPA) Abomey Benin

The knowledge of the internal stability of granular soils is a key factor for the design of granular and filter for the geotechnical infrastructures such as dykes, barrages, weirs and roads embankment. To evaluate the internal instability of granular soils different criteria are generally used in the practice. However, the results of these criteria on the same soil may lead to different evaluations of the internal instability. In this paper the common criteria used for the internal instability have been presented and compared as far as possible. It was found that the most internal instability criteria define a limit value for the secant slope of the grain size distribution curve of the granular soils. Based on this finding an own criterion for the evaluation of the internal instability of granular soil has been developed and compared to the common criteria. A very good agreement between some criteria was found. Furthermore, a site specific assessment for the evaluation of the internal instability of granular soil has been proposed in order to get more confidence in this evaluation.

关键词： Internal Instability Granular Soils Seepage Dams Dykes Site Specific Assessment Instability Index

石灰加固贝宁(西非)土的性能及滑坡防控（英文）

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Journal of Central South University 2019年第11期26卷 3066-3086页

作者： Quirin Engelbert Ayeditan ALAYE LING Xian-zhang Yvette Sèdjro KIKI TANKPINOU marx ferdinand ahlinhan LUO Jun Michel Hadilou ALAYE School of Civil Engineering Harbin Institute of TechnologyHarbin 150001China National University of Sciences TechnologiesEngineering and Mathematics(UNSTIM)Abomey 133Benin(West Africa Ministry of Public Works and Transport 01 BP 351 CotonouBenin(West Africa

过去数十年,西非主要城市的基础设施建设快速发展,亟需对该地区的岩土特性进行全面研究,以实现可持续发展.本文研究了西非贝宁土的特性.在本研究中,对西非土的性能特征进行了三方面深入研究:1)获取该地区土壤类型的特征;2)评价了石灰掺... 详细信息

过去数十年,西非主要城市的基础设施建设快速发展,亟需对该地区的岩土特性进行全面研究,以实现可持续发展.本文研究了西非贝宁土的特性.在本研究中,对西非土的性能特征进行了三方面深入研究:1)获取该地区土壤类型的特征;2)评价了石灰掺量为2%、3%和5%时土的性能;3)描述滑坡特征,以评估其破坏和潜在的不稳定性.根据法国标准,采用试验方法进行研究,开展颗粒分析试验、击实试验、液塑限试验等物理试验和动力触探试验、直剪试验、固结试验等力学试验以评估目标一,开展击实试验和加州承载比试验以评价目标二,同时对河岸滑坡的地质、环境、社会和安全等进行评估.本文首先揭示了贝宁南部(非洲)存在黏土的稳定/不稳定地区,并给出了预测稳定/不稳定地区的方程.其次,研究表明石灰占比在2%~3%之间时土体可达到最佳性能.最后,本文指出河岸滑坡可能是由山谷中的突然退水所致.

关键词：土壤特性土体性能黏土石灰滑坡

Experimental and Numerical Investigation of Stress Condition in Unstable Soil

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Open Journal of Civil Engineering 2016年第3期6卷 370-380页

作者： marx ferdinand ahlinhan Emmanuel Kokou Wouya Yvette Kiki Tankpinou Marius Bocco Koube Codjo Edmond Adjovi School of Sciences and Technologies for Building and Road (ESTBR) Polytechnic University of Abomey (UPA) Abomey Benin Institute University of Technology Lokossa (IUT) University of Lokossa Lokossa Benin

In unstable soils, a special erosion process termed suffusion can occur under the effect of relatively low hydraulic gradient. The critical hydraulic gradient of an unstable soil is smaller than in stable soils, which is described by a reduction factor α. According to a theory of Skempton and Brogan (1994) [1], this reduction factor is related to the stress conditions in the soil. In an unstable soil, the average stresses acting in the fine portion are believed to be smaller than the average stresses in the coarse portion. It is assumed that the stress ratio and the reduction factor for the hydraulic gradient are almost equal. In order to prove this theory, laboratory tests and discrete element modelings are carried out. Models of stable and unstable soils are established, and the stresses inside the sample are analysed. It is found that indeed in unstable soils the coarse grains are subject to larger stresses. The stress ratios in stable soils are almost unity, whereas in unstable soils smaller stress ratios, which are dependent on the soil composition and on the relative density of the soil, are obtained. A comparison between the results of erosion tests and numerical modeling shows that the stress ratios and the reduction factors are strongly related, as assumed by Skempton and Brogan (1994) [1].

关键词： Unstable Soil Suffusion Hydraulic Gradient Stress Reduction Factor Laboratory Tests Discrete Element Modeling

Experiments and 3D DEM of Triaxial Compression Tests under Special Consideration of Particle Stiffness

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Geomaterials 2018年第4期8卷 39-62页

作者： marx ferdinand ahlinhan Ernesto Houehanou Marius Bocco Koube Valery Doko Quirin Alaye Nicholas Sungura Edmond Adjovi National University of Sciences Technologies Engineering and Mathematics (UNSTIM) Abomey Republic of Benin University of Abomey Calavi Abomey Calavi Republic of Benin Harbin institute of Technology Harbin China Deutsche Bahn Hannover Germany

Discrete element modelling is commonly used for particle-scale modelling of granular or particulate materials. Developing a DEM model requires the determination of a number of micro-structural parameters, including the particle contact stiffness and the particle-particle friction. These parameters cannot easily be measured in the laboratory or directly related to measurable, physical material parameters. Therefore, a calibration process is typically used to determine the values for use in simulations of physical systems. This paper focuses on how to define the particle stiffness for the discrete element modelling in order to perform realistic simulations of granular materials in the case of linear contact model. For that, laboratory tests and numerical discrete element modelling of triaxial compression tests have been carried out on two different non-cohesive soils i.e. poorly graded fine sand and gap graded coarse sand. The results of experimental tests are used to calibrate the numerical model. It is found that the numerical results are qualitatively and quantitatively in good agreement with the laboratory tests results. Moreover, the results show that the stress dependent of soil behaviour can be reproduced well by assigning the particle stiffness as a function of the particle size particularly for gap graded soil.

关键词： Grain Size Dependent Stiffness Experiment Discrete Element Modelling Triaxial Compression Test Non-Cohesive Soils Materials