A Small Volume Calibration Chamber for Cone Penetration Testing (CPT) on Submarine Soils

A new small volume CPT calibration chamber with dynamically controlled boundary conditions has been built to improve the correlation between in-situ data and soil parameters. The sample volume in the new CPT calibration chamber has a diameter of 30 cm and a height of 54.5 cm. Therefore, it is possible to use reconstituted samples of limited quantity, e.g. from boreholes. The chamber is able to simulate large overburden stresses and overconsolidation ratios (OCR) up to 5 MPa. Horizontal, vertical and pore pressures are independently applied via syringe pumps while recording volume changes. All pressures are dynamically controlled and allowing stress, strain and mixed stress-strain stress boundary conditions BC1-BC5 to be enforced. The sample deformation is measured by circumferential laser triangulation sensors. In a first series of tests using Cuxhaven Sand, a 12 mm cone and BC1 conditions, CPT tip resistances reach steady state about a length of at least 10 cm. The corrected tip resistances and the inferred relative densities for Cuxhaven Sand differ substantially from previously established correlations, confirming the need for more advanced correction factors and relationships between CPT data and in-situ soil properties.