Geoenvironment Impact Mitigation and Management - Sustainable Practices in Geoenvironmental Engineering - page 363

Particle morphology, surface texture,
composition, particle size distribution

Compactibility

Density

Pore size
distribution

Porosity Packing Soil structure

Physical properties Mechanical

properties

Permeability
Hydraulic conductivity

Compressibility
Consolidation

Water retention

Shear strength

ermal conductivity Gas diffusion

FIGURE 10.2
Control of physical and mechanical properties by soil composition and particle properties and characteristics.

10.5.1.1 Soil Microstructure Controls on Hydraulic Transmission

Figure 2.11 in Chapter 2 illustrates the main points of physical interactions between a liquid
waste stream permeating among the soil particles. The physical and hydraulic properties
of the soil immediately involved in deining the nature of the luid permeation are known
as the transmission properties of the soil. These are essentially linked to the permeabil-
ity of the soil to aqueous and gaseous phases, as shown in the bottom left compartment
in Figure 10.2. Considering only luid low, the factors that affect hydraulic conductivity
can be conveniently divided into three distinct categories: (1) external environmental fac-
tors such as hydraulic head and temperature, (2) luid phase factors, and (3) soil structural
factors. The luid phase factors of signiicance in the rate of luid movement in the soil
include the density, viscosity, and chemistry of the solutes contained in the luid phase.
Soil structural features are very inluential in controlling low rate and partitioning of con-
taminants. These include the microstructure and the micropores in the soil, the pore size
distribution, and the continuity of pores. All of these are functions of the macrostructure
and density (packing) of the soil.
For any given density of soil, there is an almost ininite number of arrangements of soil
particles in a typical unit volume of soil. The sketches shown in Figures 2.9 and 2.10 in
Chapter 2 indicate that individual particles acting as single units are rarely found, except
for granular soils. Figure 10.3 shows a scanning electron microscopy (SEM) picture of a
typical clay soil unit composed of aggregate groups of clay particles, and depending on the
sizes of these groups, they are generally called domains, clusters, peds, or microstructural