Environmental Engineering Reference
In-Depth Information
FIGURE 6.84
Saprolite taken with split spoon sampler in decomposed gneiss. White material, kaolinite; black material,
biotite mica; gray material, stained with iron oxides (Jacarepagua, Rio de Janeira, Brazil). (a) 12 m depth; (b) 15
m depth.
as soils (Vargas, 1974; Deere and Patton, 1971) because of their engineering properties. In
the Piedmont region of the southeastern United States void ratios typically range from 0.7
to 1.3 and as high as 2.0, indicating the relative compressibility of the material (Sowers,
1954). Excavation by pick and shovel is relatively easy.
Stage 3: Residual soil without relict structure is the final stage of decomposition (see Figure
7.3). Clay soils (kaolin) predominate; some parts are white, but most are stained with iron
oxides and range from brightly colored red and purple to browns and yellows. In places
the iron oxides are concentrated in nodules, fissure veins, or blanket veins. Desiccation and
some cementation following leaching can cause the upper zone of 3 to 10 ft to form a stiff
crust where located above the water table. The soils are usually classified as ML or CL-ML.
Engineering Properties
A general description of the weathering profile in igneous and metamorphic rocks
together with some relative engineering properties is given in Table 6.14. Strength param-
eters of weathered igneous and metamorphic rocks are given in Table 3.35.
Sedimentary Rocks (Excluding Marine Shales)
General
Sedimentary rocks are composed of stable minerals (quartz and clays) or soluble materi-
als, with minor amounts of unstable materials present either as cementing agents or
 
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