A paper by T.B.S. Christopher, 1996.

Description of bulk density and pore space, and how texture and structure may affect these soil properties.

The plastic limit is that moisture content of a soil at which it becomes too dry to be plastic, used together with the liquid limit to determine the plasticity index which when plotted against the liquid limit on the plasticity chart enables the classification of cohesive soils.

A student paper by Erik Ekdahl and Mary Savina, 1996.

Detailed explanation of how to do soil sampling in order to achieve reliable results.

Detailed description of a lab work assignment.

These tutorials range in difficulty from college sophomore to the senior/graduate/postdoctoral level. They begin with the basics and extend to a new exact solution to Richards' equation for unsaturated horizontal and vertical flow.

Interactive tutorials on soil taxonomy, texture and calculation of soil physical properties (New Mexico State University).