Defined: An inorganic silt of slight plasticity; quakes like jelly from vibration.
Bull’s Liver is a highly unusual soil, with unconventional engineering behaviors. Without sufficient testing and identification, these soils can cause damage and delays in development projects, or result in construction cost overruns. To avoid such overruns, it is crucial that soil properties be sufficiently identified during subsurface exploration, and proper evaluations be considered during project design phases.
An informative video showing the extraordinarily unique behavior of this soil may be viewed at the IEC YouTube channel. Go go http://youtu.be/No16bDOTVi0.
Rock Flour (or Bull’s Liver) consists predominantly of silt-size particles, but has little or no plasticity. Non-plastic rock flour contains particles of quartz, ground to a very fine state by the abrasive action of glaciers. Terzaghi and Peck (1967) state that because of its fine particle size, this soil is often mistaken as clay.
In describing this soil, the term “bull’s liver” apparently comes from its in-situ appearance. It has been observed that in a saturated state, it quakes like jelly from shock or vibration and can even flow like a liquid (Sowers and Sowers, 1970). This is of course a highly undesirable condition, not only for construction work, but for permanent foundations.
Cortlandt Street Station, Manhattan, New York-Photo (C) MTA Bridges & Tunnels Special Archive. Used with permission.
The Cortlandt Street Station, which serves the R&W subway lines in Manhattan, New York, is located immediately adjacent to the World Trade Center site. Constructed in the early 20th century using cut-and-cover methods, the station has two platforms and twin tracks situated within a typical New York City Metropolitan Transit Authority (NYCMTA) concrete arch box structure. Soils in the area, known locally as “Bulls Liver,” soils are typically low-permeability, low-plasticity silts and have historically demonstrated high instability when saturated and subjected to construction-induced disturbance.
This was the case when recovery and construction activities at the adjacent World Trade Center site created significant ground loss and subsequent loosening of the surrounding soils at the station site, resulting in settlement of the station structure up to three inches at the point of maximum deflection.*
*source: More Trench
With such cautionary tales to go by, any construction project manager where such soils are suspected, would do well to heed the signs, and do a more thorough examination than might normally be called for. It is best to err on the side of caution, rather than proceed into circumstances that place life and property at risk.
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