Experimental investigations of critical hydraulic gradients for a soil prone to suffusion

The presence of soils, which are at the limit state of internal stability, is a potential risk to earthworks under seepage flow. Therefore, it is necessary to identify unstable soils and to estimate hydraulic gradients at which the suffusion can be initiated respectively progressed. An experimental study has been carried out to quantify critical hydraulic gradients for a widely graded soil. For the tested soil, in downwards vertical percolation experiments, the global critical hydraulic gradients lie in the different ranges between icrit = 0:1 to 5:5 with dependency on the particle arrangement. The critical hydraulic gradient was investigated using various types of sample preparation technique. Moreover, suffusion tests using several types of samples with the same particle size distribution have been carried out. It states that for such a widely graded soil, the main problem is the particle arrangement. In other words, the suffusion might be not problematic if there is no segregation. Sometimes a specific amount of segregation also stabilizes the sample against suffusion. The common way of sample preparation delivers comparable results to the results of other researchers

Numerical investigation of the particle skeleton of widely graded soils prone to suffusion

The soil structure affects directly the capability of distributing and transmitting forces between its particles. Thus, the particle arrangement dictates the performance of soil under hydraulic and dynamic loads. This paper describes an analysis method in which the skeletal force chains of the particle assembly (packing) can be identified based on Discrete-Element-Method (DEM) modelling. For the simulations the software LIGGGHTS is used. A widely graded particle size distribution (PSD) is investigated to find correlations between PSD and the micromechanical properties of the particle assemblies. These PSD is based on common internal stability criteria prone to suffusion. The different roles of fractions of the PSD in packings and the force chains under specified load are analysed. Therefor a packing is generated with the Modified-Force-Biased-Algorithm (MFBA). A method based on the bimodality of widely graded PSDs is proposed to differentiate the soil skeleton and the fill of packings of such a PSD. Particle contact number and contact forces are evaluated to identify the amount of loose particles, which are potentially mobile particles. The influence of the packing homogeneity on its skeleton is also addressed. The described method provides a better understanding of the soil structure as well as of internally stability of widely graded soil

Experimental identification of the dominant fabric in widely graded soils

To estimate the vulnerability of widely graded soils to internal erosion, the soil structure has to be analysed. Based on the theory of the bimodal fabric, each particle size distribution (PSD) has a unique diameter that divides the PSD into particles of the soil skeleton and finer mobile particles. The particle diameter, which divides the PSD into these two fractions, is defined as the separation point (dT) and part of the soil skeleton. In this study the Sequential Fill Test (SFT) is used to identify the mobility of particle fractions and the soil matrix. This study is an extension of a series of descriptions of this particular test method. The paper is focused on a widely graded PSD, which is prone to internal erosion. This study demonstrates the change of the soil matrix by variation of the amount of the fine particles. The soil matrix of the investigated PSD does not change until the pore volume is completely filled with mobile particles. If the mobile particles filled completely the pore volume of the coarse soil skeleton, they become also part of the soil skeleton. This matrix is called dual matrix. With further increase of the amount of fine particles, the coarse skeleton is replaced by a new skeleton, where all particles belong to the soil skeleton. For the assessment of a selected PSD, which is prone to internal erosion, it is important to identify the amount of fine fractions, which can stabilize an internally instable dominant fine matrix (i.e. building a dual matrix)

Total Quality Management (TQM) and Information Technology (IT): Relationships and Performances

Modern and new technologies have changed the management view and the methods of problem solving and management of organizations. For effectively managing the organizations at todays changing environment managers should view different global economic, social, political and legal conditions and must pay attention to factors such as developing deformation and communication technologies and changing customers expectations. For with respect to each condition and factor they needs appropriate information to increase their knowledge and decrease their uncertainty to have effective performance. In this way it seems necessary to consider information technologies and total quality management and understand their impact on efficiency and effectiveness. In this article through citing the relationships between information technology and total quality management we attempt to examine their impact on organizations efficiency and effectiveness. Therefore we study the concepts of effectiveness efficiency and productivity and then point to the relationships between information technology and total quality management and to the impact of these relationships on organizations efficiency and effectiveness. Because, today managers' attitudes and views to quality in firms is new. Production with desired quality requires not only clear definition of goals, specific policies and procedures for each part of work and each stage of process but also real time inspection, measurement and documentation syste

Les textes théologiques entre la philologie et l'histoire. La constitution de corpus et les étapes de la formation des textes

Suffusion is one major reason for dysfunctions of earth dams and embankments. Suffusion as a self-filtration process occurs when loose grains are mobilised and transported through a series of pores interconnected by pore constrictions formed by the skeleton. For the assessment of suffusion, the grain size distribution is divided into two parts: (i) skeleton, which transfers the load and forms the basic soil skeleton; and (ii) loose grains, which can be mobilised and removed by seepage flow. To date, most suffusion assessment methods based on self-filtration criteria assume that there is a sharp boundary in grain size distribution between soil skeleton and loose grains fraction. This paper suggests a newself-filtration criterion for suffusion assessment which was developed on a numerical approach on the grain scale. The major difference to existing criteria is the introduction of a smooth boundary between the skeleton and loose grain fraction. The new method has been tested with data from some experimental studies