Characterizing Subsurface Conditions Using Drilling Parameters for a Deep Foundation Project in Boston, MA, USA

Identifying stratigraphic changes from coarse to fine-grained soils was one of the primary goals of the subsurface investigation performed for a deep foundation project in Boston, Massachusetts, USA. A drilling parameter recorder (DPR) was used during the advancement of a tri-cone roller bit through the overburden glacial soils to aid in identifying changes in soil stratigraphy. By correlating soil samples obtained from 2-inch split spoons with the trends in the drilling parameters, it was possible to identify changes in stratigraphy in other boreholes based on the DPR data alone. The correlations were used to reduce the frequency and number of split spoon samples taken and ultimately increased the efficiency in which the borings were completed. In addition, DPR was used to record the drilling parameters during rock coring to better identify natural fractures in the formation. By correlating the trends in the DPR data with the physical characteristics of the bedrock core specimens, it was possible to identify zones of more fractured rock, and select depth intervals in which to perform packer tests. The results from the investigation were used to determine the design depth of a reinforced concrete diaphragm wall.