Site Characterization Using the Seismic Piezocone in Presumpscot Clay and Development of Piezocone Correlations to Engineering Parameters

The Presumpscot clay deposit found throughout coastal and inland regions of Maine is a sensitive silty clay deposit, formed beneath glaciers in the marine environment. This soil often has silt and fine sand layers, which influences anticipated behavior during construction, as well as performance of infrastructure. Many times, discrete sampling does not identify the variability at a site, and the sensitive nature of the soil makes collection of high quality samples difficult, depending on ground conditions. Uncertainty in soil characteristics and engineering parameters associated with soil sampling (i.e., sample disturbance) and identification of variability within the soil deposit can be reduced with in situ testing. One such in situ test is seismic cone penetration testing with pore pressure measurement (i.e., piezocone) (SCPTu). The SCPTu test provides near continuous measurement of tip resistance, sleeve friction, and pore pressure in situ. The seismic cone also has the capability to detect shear waves generated at the ground surface so dynamic soil properties such as shear wave velocity and small strain shear modulus can be determined. The advantage of SCPTu testing is that a SCPTu profile can be performed in less time than a conventional boring to a similar depth. Additionally, the continuous profiling provides more information about the subsurface through measured penetration resistance, compared to soil sampling at discrete intervals and subsequent laboratory testing. For instance, a full record of layering and changing soils can be identified; these layers may be missed by discrete interval sampling. Once SCPTu correlations to engineering parameters are generated for a soil deposit through correlations of penetration parameters and laboratory determined engineering properties of soils, fewer subsequent soil samples and laboratory tests are necessary to characterize a site or deposit. This leads to time and cost savings, all while providing a more extensive and efficient subsurface site investigation. This thesis describes research aimed at developing correlations between measured SCPTu parameters and engineering properties for the Presumpscot clay, a marine deposit found extensively in the coastal regions of Maine. The objective is to provide engineers with a tool to improve site investigations as a means to improve design and reduce cost. The test site chosen for the investigation is in Falmouth, Maine. Accompanied with a laboratory testing program on high quality soil samples, the SCPTu data can be used to develop correlations to engineering parameters such as stress history and undrained shear strength. The correlations developed by this study were compared to correlations developed using site investigation results from previous investigations at the Falmouth, ME site. The purpose of the correlation comparison is to evaluate and advance the standard of practice