Construction And Test of An Instrumented 2D Channel With Rainfall And Insolation Control.

This paper presents the construction and testing of a large instrumented 2D channel for the simulation of the performance of compacted barriers under controlled conditions of insolation and rainfall. Details of the main apparatus devices and capabilities and the results of a long-term test performed on a capillary barrier (CB) are presented. The performed test aimed to simulate the CB behavior over a period of one year in typical semi-arid conditions. The channel behavior was considered very promising with its components functioning as expected and providing the desired information. Concerning the CB performance, it is shown that the upper clayey layer of soil presented undesirable shrinkage cracks that impacted the CB performance, mainly at the end of the period of evaluation. The obtained results point to the need to use of silty or low plasticity clayey soils in the CB design, despite the higher expected values of hydraulic conductivity, as well as the adoption of layers thicker than usual in order to preserve the integrity of the clayey soil near the interface with the bottom coarse soil layer.

Effets du précédent cultural arachide (Arachis hypogaea L.) et de la charge en éléments grossiers du sol sur la production du coton (Gossypium hirsutum L.)

Le monde agricole est confronté à des baisses fréquentes de rendements qui sont liées à l’état physique (structure et/ou texture) ou à la non fertilité du sol. Pour y remédier, nous avons eu recourt aux légumineuses alimentaires. Ainsi, une étude a été conduite à la station de recherche sur le coton du Centre National de Recherche Agronomique (CNRA) à Bouaké, en vue d’évaluer l’effet combiné du précédent cultural arachide et du taux en éléments grossiers du sol sur la production du coton. Le dispositif expérimental mise en place a été en blocs de Fisher comportant quatre blocs et cinq traitements (T1, T2, T3, T4 et T5). Les résultats obtenus ont montré que la présence d’éléments grossier influence fortement la résistance à la pénétration des racines, avec des corrélations positives (r = 0,757) et (r = 0,768) dans les tranches (0-20) et (20-40). Ce qui joue négativement sur le développement racinaire (r = -0,820). Le précédent cultural a favorisé le développement des racines dans les traitements T3, T4 et T5. Celui-ci associé à la fertilisation minérale a permis d’obtenir un rendement de (1482 kg/ha) en T4, soit un gain de 58% par rapport à la pratique conventionnelle en milieu paysan (T2). La précédente arachide et les éléments grossiers du sol influencent la production du coton. Ces résultats pourraient être utiles pour les producteurs, dans le choix des parcelles et des pratiques culturales.Mots clés : Cotonnier, précédent cultural, éléments grossiers, développement racinaire. English Title: Effects of the previous peanut (Arachis hypogaea L.) and the loading of coarse soil elements on cotton production (Gossypium hirsutum L.)The agricultural world is confronted with frequent yield reductions that are linked to the physical state (structure and/or texture) or non-fertility of the soil. To remedy this, we have resorted to the use of food legumes. Thus, a study was conducted at the cotton research station of the National Center for Agronomic Research (CNRA) in Bouaké, in order to assess the combined effect of the previous groundnut crop and the level of coarse soil elements on production cotton. The experimental set-up was in Fisher blocks comprising four blocks and five treatments (T1, T2, T3, T4 and T5). The results obtained showed that the presence of coarse elements strongly influences the resistance to root penetration, with positive correlations (r = 0.757) and (r = 0.768) in the slices (0-20) and (20-40). Which negatively affects root development (r = -0.820). The previous crop favored the development of roots in T3, T4 and T5 treatments. This combined with mineral fertilization made it possible to obtain a yield of (1482 kg / ha) in T4, that is to say a gain of 58% compared to the conventional practice in peasant environment (T2). The previous peanut and coarse soil elements influence cotton production. These results could be useful for producers, in the choice of plots and cultural practices.Keywords: Cotton plant, crop precedent, coarse elements, root development.

Exploring the Occurrence of Clogging in Highly Permeable Coarse Soils of Dam Foundations

Leakage through the permeable coarse soils of dam foundations in Tibet, China, lessened over time without any additional antiseepage measures. In fact, clogging generated during the infiltration process is recognized as the major factor in reducing leakage. A laboratory study was conducted to understand clogging in highly permeable coarse soil of a dam foundation with the primary aim of determining the clogging patterns and optimum clogging particle size (PS). Seven replicate experiments were constructed using soil media with PS ranges of 32–64 mm, 16–32 mm, 8–16 mm, 4–8 mm, 2–4 mm, 1-2 mm, and 0.5–1 mm to observe clogging after feeding the soil media with sediments of different PSs. The experimental results showed that four clogging patterns were formed in different PSs of the coarse foundation soil. The ratio of the effective aperture of the soil Dea and the equivalent clogging particle size dede/Dea had a dominant effect on the four clogging patterns (surface clogging, de/Dea>1; surface-internal clogging, 0.5<de/Dea≤1; internal partial pore blockage, 0.25<de/Dea≤0.5; and unclogging, de/Dea≤0.25). The assessment criterion of the optimum clogging pattern was determined by 0.5<de/Dea≤1, and from that, the optimum clogging PS do was calculated.

A frost heave model of unsaturated coarse-grained soil considering vapour transfer

Substantial frost heave has been observed in coarse fills in high-speed railway embankments. These coarse fills have low fine contents and very low water content. The groundwater table is located below the coarse fills. The coarse fills were considered not susceptible to frost heave. Recent experimental results in the literature showed that vapour transfer has a considerable influence on the frost heaving of unsaturated coarse-grained soil. But vapour transfer has been rarely considered in the modelling of frost heave. This study presents a new frost heave model with considering vapour transfer and its contribution to ice formation. The rigid ice theory is applied to initiate an ice lens formation in the frozen fringe. An updated computer programme PCHeave is developed by considering the vapour transfer. The results of the proposed model are compared with laboratory test results, which show reasonable agreement. The prediction of the model agrees well with the measured frost heave and frost depth, which indicates that the proposed model can reasonably reflects the process of frost heave in unsaturated coarse soil.

Horizontal and Vertical Geotechnical Variations of Soils According to USCS Classification for the City of An-Najaf, Iraq Using GIS

The unified soil classification system (USCS) first proposed by Casagrande and subsequently developed by the Army Corps of Engineers. It widely used in many building codes and books. An-Najaf city is the most important city in Iraq due to its religious and spiritual value in the Muslim world, so it is fast expanding and continuous developing city in Iraq. The data from 464 boreholes in the study area for depths of 0–26 m have been used. 13 Soil samples were collected from each borehole with 13 depths level (0–26) m with 2 m intervals. The USCS was applied to the soil samples from 13 depth levels borehole. This research aims to create a geodatabase for soil properties for An-Najaf. The ArcGIS 10.5 software was used to interpolate the spatial data to produce 33 geotechnical maps for fine soil, coarse soil and USCS for 13 depth levels. For numerical soil data, Ordinary Kriging has been used for interpolation mapping of Fine and Coarse percentage data for each depth. For non-numerical (nominal) soil data (USCS class), the Indicator Kriging method is used. The results show that the coarse soil occupied 85–95% for depth 0–16 m and consist of (SP, SP-SM, SM) while fine soil occupied 5–15% consisting of (OL, CH, ML) subsequently, this soil when compacted has a permeability of pervious to semi impervious, good shearing strength, low to very low compressibility and acceptable workability as a construction material. The results also show that after 16 m depths until 26 m, the fine soil percentage increased to 40% with a coarse soil percentage of 60%, indicating changes in soil characteristics as the permeability became semi-pervious to impervious, fair shearing strength, medium compressibility and fair workability as a construction material. The study results will provide help and saving time, efforts and money in preliminary engineering designs.