Page 54 - RoadCem Manual - PCT BV

4.2 Soil properties 4.2.1 General
Figure 4.1 Can we use soil for pavement structural layers?
The first thing one needs to do when characterizing the soil/sub base is to adopt a soil classification system.
The adoption of the principles of soil mechanics by the engineering profession has inspired numerous attempts to devise a simple classification system that will tell the engineer the properties of a given soil. As a consequence, many classifications have come into existence based on certain properties of soils such as texture, plasticity, strength, and other characteristics.
A few classification systems have gained fairly wide acceptance, but rarely has any system provided the complete information on a soil that the engineer needs. Nearly every engineer who practices soil mechanics will add judgment and personal experience as modifiers to whatever soil classification system he uses. Obviously, within a given agency (where designs and plans are reviewed by persons entirely removed from a project) a common basis of soil classification is necessary so that when an engineer classifies a soil as a certain type, this classification will convey the proper characteristics and behaviour of the material. Furthermore, the classification should reflect those behaviour characteristics of the soil that are pertinent to the project under consideration.
For our purposes we recommend that a Unified Soil Classification System (USCS) be used. When appropriate a reference to other Soil Classification Systems will also be given.
The USCS is based on identifying soils according to their textural and plasticity qualities and on their grouping with respect to behavior. Soils seldom exist in nature separately as sand, gravel, or any other single component. They are usually found as mixtures with varying proportions of particles of different sizes; each component contributes its characteristics to the soil mixture. The USCS is based on those characteristics of the soil that indicate how it will behave as an engineering construction material.
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