The engineering properties of both rocks and soils depend on their specific type and texture.
When designing any building or other structure on land, engineers must take into consideration the structural properties of the ground that supports their project. Both soil and rock have highly varied engineering properties, depending on the specific type of soil or rock. For this reason, the analysis of geologists and soil scientists is very useful information to engineers. Does this Spark an idea?
Critical Slope
The critical slope, also known as the angle of repose, is the most extreme angle at which rock or soil can remain stable. For example, when digging out a trench, you may find that digging excessively steep walls causes the surrounding earth to cave in. At the beach, where the soil is very sandy, the sand will begin to cave in at a far gentler angle. By contrast, in dense, claylike soil, you can dig on the vertical without triggeromg a landslide. Critical slope, then, is a property both of soil and rock, which varies among different types, textures and stages of each. For example, granite changes its critical slope as it weathers; the smaller stones of highly-weathered granite can eventually behave more like soils than boulders formed from the same type of rock.
Bulk Density
You can determine the bulk density of either soil or rock, a measurement that reflects a material's density, taking into consideration the presence of pores within the material, as in the case of soils or gravelly rocks. Bulk density is usually measured in grams over cubic centimeters, taking the weight of oven-dried soil and dividing it by the volume it occupies under no added pressure. Bulk density of a material not only affects its suitability for engineering applications, it also influences the movement of water through or around the medium as well as plants' ability to root in soil or rock.
Elasticity
Engineers figure soils' and rocks' elasticities based on the shear modulus, also known as the modulus of rigidity. This is a coefficient that describes the elastic behavior of a material when a shearing force is applied. For example, when an earthquake causes intense pressure perpendicular to the face of the material, different soils and rocks will have different abilities to stretch before breaking. The shear modulus corresponds to this capacity. You measure shear modulus in terms of shear stress over the material's linear displacement. If you know the shear wave velocity, the speed at which seismic waves travel through a material, and you also know the material's bulk density, you can determine the shear modulus, as all three properties are interconnected.
Tags: soil rock, shear modulus, also known, Bulk density, bulk density, engineering properties, example when
