Speaker
Description
Cone penetration tests (CPT) are widely used as a cost-effective and rapidly deployable method for ge-otechnical site investigation. However, the derivation of geotechnical design parameters from CPT data remains insufficiently standardized within the current German framework (DIN 1997-2:2010-10;DIN 4020:2010-12). Existing empirical correlations are often restricted to specific soil types and deposi-tional conditions and are not directly applicable to many types of non-cohesive soils encountered in northern Germany.
To address this gap, a large-scale geotechnical calibration chamber is currently being designed by the Federal Waterways Engineering and Research Institute (BAW) in cooperation with the Helmut-Schmidt-University, Hamburg (HSU). The facility is intended to enable controlled laboratory CPTs in homogeneous soil specimens of known density and grain size distribution. The cylindrical chamber will have an internal diameter of 1.8 m and a height of 2.2 m, making it unique in scale and allowing boundary effects to be minimized. Sand specimens will be prepared using an integrated air pluviation system, which is part of the calibration chamber setup, that produces a uniform sand rain across the entire chamber cross-section while main-taining a constant drop height. This method enables the reproducible preparation of homogeneous soil specimens with defined relative densities. In addition, the feasibility of performing pluviation under vacuum conditions is being investigated in order to further improve sample homogeneity and reduce particle segregation. The chamber is designed to allow independent application of both axial and radial stresses. Radial stress will be applied via a water-pressurized membrane enclosing the specimen, con-ceptually similar to a large-scale triaxial cell. Axial stress will be applied either through hydraulic cylin-ders located beneath the specimen or via a pressurized membrane at the base. Controlled saturation from the base permits investigation under both drained and saturated conditions.
Although the project is currently in the final design phase and experimental results are not yet availa-ble, this contribution presents the conceptual design, technical challenges, and anticipated capabilities of the calibration chamber. The facility will form the basis for future systematic CPT investigations aimed at developing improved, soil-specific correlations for non-cohesive soils.