Field Estimationof Fine Soil Materials Strength
Field Estimationof Fine Soil Materials Strength
(OP)
A test pit was dug to 4.2 m. From top to bottom, it was 1.6 m silty clayey sand, 0.9 m peat/organic silt, and 1.7 m mineral silt. The bottom of pit was examined immediately after excavation and it was stiff silt but after half an hour the silt materials spalled and caved in. GWL was at top of silt layer. The silt on the wall appeared to be firm. A photo is attached.
What does the spalling of wall suggest to an engineer. Could the silt be soft or.. Thanks.
What does the spalling of wall suggest to an engineer. Could the silt be soft or.. Thanks.





RE: Field Estimationof Fine Soil Materials Strength
RE: Field Estimationof Fine Soil Materials Strength
Additionally, the inflow of water may be causing the silt to cave.
You are going to need other tests to estimate design parameters.
Mike Lambert
RE: Field Estimationof Fine Soil Materials Strength
RE: Field Estimationof Fine Soil Materials Strength
Mike Lambert
RE: Field Estimationof Fine Soil Materials Strength
www.PeirceEngineering.com
RE: Field Estimationof Fine Soil Materials Strength
Normally, as mentioned previously, granular soil will behave like this below the groundwater level; the walls will collapse, even decent bearing soils. Fine grain sands and non-plastic silts typically tend to be more susceptible to collapse. Because there is no confinement,once the surrounding material is removed, these soils may appear loose, but they could be of a much denser nature in the undisturbed state.
It is very difficult and unreliable to look at soil of this nature and predict its strength. Use SPT or maybe use dynamic cone penetrometer to help estimate the strength of the material. If those are not available, you have to use some very conservative estimates.