Soft clays

Clay smear soft clay, often of marine origin, is smeared into the fault plane during movement and provides an effective seal. 

Sepiolite, also known as meerschaum or sea foam, is a white or off-white soft clay of low density. It is composed of hydrated magnesium silicate and occurs in consolidated masses that are easily carved and whose surfaces can be smoothed and endowed with a durable polish. It is for this reason that meerschaum has been used, since antiquity, for making ornaments and decorative carvings. For many centuries meerschaum has been intensively mined in Greece and Turkey. 

Porosity that includes the voids between mineral (or soil) grains is referred to as primary porosity. When the porosity is the result of cracks, fractures, or solution channels, it is known as secondary porosity. The porosity of soft clay is often over 50%, but clay typically has low permeability because the pores are either not interconnected or are too small to permit easy passage of water. On the other extreme, nonfracture igneous rock often has a porosity of less than 0.1% but, again, low permeability. 

An interesting application of early chemistry was the use of fire to make pottery. Early pots were formed from soft clay that, of itself cannot hold much weight or water. Early humans... 

Hinckley believes the differences between the two types of clays is largely a function of the environment of deposition and post-depositional leaching. The poorly crystallized hard clays were believed to have been deposited in a marine environment where face to face flocculation occurred. The well-crystallized soft clays were presumably flocculated edge to face in a fresh-water environment. The more porous soft clays were more thoroughly leached and re-crystallized than the less porous hard clays. Like other kaolinite studies this one does not provide any specific information about the actual chemical composition of the kaolinite minerals. 

The allowable bearing pressure varies for different types of soils, and the soil should be checked at the surface and at various depths to determine the bearing characteristics. The allowable bearing pressure for rock is 30 or more ton/ft2 (30 X 104 kg/m2), while that for soft clay may be as low as 1 ton/ft2 (1 x 104 kg/m2). Intermediate values of 4 to 10 ton/ft2 (4 X 104 to 10 X 104 kg/m2) apply for mixtures of gravel with sand, hard clay, and hardpan. 

Fig. 12. Photograph of a surface exposure of a fault in east Texas. A sandstone is juxtaposed across a 180 m throw fault with another sandstone. The fault zone consists of about a meter wide soft clay (from Smith, Company Report).

Normally consolidated soft clays, silts, organic deposits, landfills... 

Structural fills Structural fill distributes loads to underlying soft soils Soft clays or organic soils marsh deposits High strength good load distribution to underlying soft soils... 

In September 2006, at depths of 0-0.3 m, 22 species of mobile microphytes (Table 3) were again present In November 2007 (0-0.2 m water depths) there were only 13 species (Table 4). In the beginning of June 2008 microphytobenthos of ultra-shoals (0-0.3) cmisisted of two species on soft clay groimd (Nitzschia tenuir-ostris and N. radiosafallax) and of 14 species — on rocky ground (Table 5). 

This is essentially hydrated aluminium silicates derived from natural deposits. There are soft clays, hard clays, calcined clays and treated clays. This is a common filler in the manufacture of acid resistant ebonites, natural soft rubbers and in Neoprene compounding for phosphoric acid duties. 

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