Soil resistance description

Terzaghi assumed that a soils response to a surface load could be divided into three zones, as shown in Figure 2.8. Zone I moves down, causing Zone II to rotate about the footing edge. Zone III resists the movement of Zone II. It can be inferred that the soils response to the load mobilizes shear resistance along the bottom boundaries of Zones II and III. A more detailed description of the soil s assumed response can be found in soil mechanics texts. 

A more descriptive terminology for liquefaction failure of plastic soils (silts or clayey silts), containing 100 % fines and with relatively high PI (such as PI > 10 %), is cyclic strain softening which emphasizes more on the structural breakdown of the material under cyclic loading than on the buildup of excess pore water pressure. Evaluation of liquefaction resistance for plastic soils is an area that requires more research. In the... 

The distributed reactivity model explanation for the biphasic rate behavior commonly observed for desorption of HOCs from soils is that the soft-carbon sorbed, or labile fraction of the contaminant desorbs readily and reversibly, whereas the hard-carbon sorbed, or resistant component is released much more slowly. The slow desorption step has been attributed to non-Fickian diffusion into a tightly-knit SOM, polymerization, or entrapment within the SOM matrix. The rate model found in comparative analyses to be the most appropriate for description of such behavior (17) is a two-phase release model which couples first-order rate equations for both the slow, resistant, and rapid, labile fractions, < >r (= 1- (j) ... 

---