Most important parameters for the evaluation of trafficability of deep sea floor are the undrained shear strength and the shear stress - shear displacement relation. A test stand, where shear ring, vane test, track segment tests, cone tests and plate load tests can be performed in bentonite water mixture, has been built and concepts of deformation are being developed to explain the device sensitivity of measurement values. A method of correcting device sensitivity between measurements with vane shear tester, shear ring and track segment is introduced. Physical explains for the device sensitivity for enhancing traction force calculation shall be found.
The Institut für Konstruktion (IKS) and the National Institute of Ocean Technology (NIOT) have developed and built a tracked deep sea mining machine for mining of manganese nodules, which underwent several successful test series till the end of 2000 in the Gulf of Mannar, off the South Indian coast. For the evaluation of the trafficability of the deep sea soil, the tractive forces and the soil bearing capacity are most important. The calculation of the maximum possible traction forces is done with the use of shear stress - shear displacement relations. The experimental determination of shear stress - shear displacement relationships is still strongly varying with the geometry and type of the measurement method used. For systematic analysis of the device dependency IKS has set up a test stand, that allows comparative measurements with different measurement methods. In addition to the experimental measurements, finite element simulation of the mechanical deformation process is being carried out to identify parameters (Luetticke, 2003), which cause the device dependency. An ideal outcome of the research work would be to introduce physically verified correction parameters or functions, which allow the elimination of the device sensitivity of the different measurement methods.
