Rock strength and resistance

Abstract

The physical and dynamic properties of rock are governed by the nature of the solid mineral grains, the nature and extent of voids within the mineral aggregate and the nature of the bond, if any, between the mineral grains. These characteristics will also govern rock behaviour and should figure prominently in any explanation of the interplay between landform evolution and rock type. Erosional agencies attack rock in a variety of ways such as by wear, abrasion, impact, crushing and plucking. The most important rock properties are those which reflect these processes. Rock properties can be grouped into three classes:

• (a) Properties which measure the hardness or toughness of rocks. Hardness is usually taken to mean resistance to abrasion and toughness refers to resistance to crushing or impact.

• (b) Properties which relate to the ease with which water is absorbed and transmitted through rocks, such as porosity, permeability, water absorption and specific gravity. These properties enable an assessment to be made of a rock’s resistance to processes such as frost action, swelling and softening.

• (c) Properties which relate to the strength of rock. Strength can be assessed in a number of ways, e.g. compressive strength, tensile strength, shear strength.