No abstract

Soil thermal resistivity plays an important role in the design and laying of high-voltage buried power cables, oil and gas pipelines, nuclear waste disposal facilities, ground-modification techniques employing heating and freezing, etc. For these situations, it is important to estimate the resistance offered by the soil mass in dissipating the heat generated. Several investigators have tried to develop mathematical and theoretical models to estimate soil thermal resistivity. However, these models are not always capable of predicting thermal resistivity of soils. This is mainly due to the fact that thermal resistivity of soil is a complex phenomenon that depends upon various parameters, viz. type of the soil, particle-size distribution, compaction characteristics, etc. As such, none of the relationships available in the literature are suitable for estimating the thermal resistivity of all soils. This paper deals with the details of fabrication of a "laboratory thermal probe" which has been used to evaluate thermal resistivity of various soils. A relationship has been proposed to estimate thermal resistivity of soils depending upon the moulding moisture content and density of the soils.Key words: thermal resistivity, laboratory thermal probe, black cotton soil, fly ash, sands, silty sand.

A generalized procedure based on finite elements and non-linear programming has been developed and is presented to obtain lower-bound solutions for break-out factors for horizontal and vertical strip anchors embedded in sand. The validity of the method is shown by comparison of predicted values with experimental data and theoretical solutions available in the literature. Une procédure généralisée, basée sur une programmation non-linéaire par éléments finis, a été développée afin d'obtenir la solution en limite inférieure des facteurs de rupture pour des ancrages-plaques horizontaux ou verticaux enfoncés dans du sable. La validité de cette méthode est démontrée en comparant les valeurs calculées à partir de données expérimentales aux solutions théoriques disponibles dans la littérature.

Various models that incorporate the influence of soil suction on different engineering properties of unsaturated soils have been developed. However, a systematic study of various physical parameters of the soil mass such as type of soil, particle size distribution, and the state of compaction (i.e., water content, dry unit weight, and saturation) is required to understand the influence of these parameters on soil suction, directly or indirectly. This would be of great help in understanding the unsaturated properties of the soil mass. With this in view, an effort has been made in this technical note to measure the suction of locally available silty soil and commercially available white clay, compacted at different water contents and dry unit weights, using an insertion tensiometer. Efforts have been made to determine the influence of various parameters, as stated earlier, on the soil suction. Details of the test setup used for these studies are also presented.

Modelling heat migration in soils is of great interest in various civil and electrical engineering projects. Researchers have developed several analytical and numerical models to model heat migration in soils and their validity has been demonstrated by conducting conventional laboratory or field experiments. Though laboratory tests are inexpensive, quick and easy to perform, they lack simulation of the prototype conditions in terms of in-situ stresses. To overcome this, field tests, which are relatively costly, time consuming and difficult to perform, are found to be of immense help. In order to overcome these limitations, a geotechnical centrifuge can be used for studying heat migration in the soil mass. To demonstrate the utility of a geotechnical centrifuge for such studies, standard grade sand compacted to different states has been chosen. Using a line heat source, a thermal probe, thermal gradient has been imposed and migration of heat in the soil mass has been studied by recording its temperature as a function of time and radial distance. The study highlights utility of a geotechnical centrifuge in modelling heat transfer in the soil mass.