Theory and Practice of Soil Densifcation

Of the several factors that determine the thermal resistivity of soils the "dry" density, i.e., the weight of the solid soil components per unit volume, varies the least under normal surface conditions. Because of this, and since for the same soil composition, the thermal resistivity decreases with increasing density, optimum densification should be sought for soils that must dissipate beat transmitted to them from electric cable and conduit systems. Such soils include the normally granular bedding and enveloping of the cable and conduit, the original, often cohesive, excavation soil which is employed for the upper and surface sections of the trench, and sometimes the soil outside of the trench proper if the system is placed in a loose natural soil or in fill. Obviously, the engineer entrusted with the design and construction of underground cable or conduit systems must be concerned with the principles governing the potential densities of soil materials and also with those underlying the methods by which the design densities are obtained in the field.