Untersuchungen zur Befahrbarkeit von Tiefseeböden mit selbstfahrenden Arbeitsmaschinen

Trafficability of deep sea soil is one of the main pre-conditions for successful mining of manga-nese nodules from the deep sea. Thixotropic soil behaviour of the deep sea soil makes specific demands on the crawler vehicle and assessment of trafficability.

In this thesis, criteria for trafficability assessment and soil mechanical basics of selected meas-urement devices, like vane shear test, cone test, shear ring, track segment and load plates are outlined. Vertical stress distribution in the soil, immediate settlement and ground failure under the crawler vehicle are described. Furthermore the measurement behaviour of vane shear test, shear ring, track segment and load plates is looked into experimentally with a specifically developed and built test stand of University of Siegen.

Based on the mechanical basic principles and the experimental results, a function of shear stress – shear strain especially for deep sea soil (IKS-Function) is developed to minimise systematic deviations in the characterisation of deep sea soil shear behaviour. With the developed function, characteristic diagrams of experimental shear stress – shear strain characteristics of vane shear test, shear ring and track segment have been created. Furthermore characteristic diagrams for dynamic sinkage of track segment and shear ring have been set up. The mathematical descrip-tion of the experimental results allows transformation of the different measurement behaviours into each other.

The use of a deep sea insitu soil testing device with cone penetration test, vane shear test and load plates with settlement measurement provide the characteristic data for assessment of traf-ficability. With these data and the relevant parameters of the crawler vehicle, traction safety and ground failure safety are formulated. An example provides practical numbers for soil values, trac-tion forces, driving resistances, traction safety and ground failure safety. In this context two gen-eral results could be obtained: At first, the vertical soil pressure due to the crawler vehicle im-proves the residual traction force compared to traction force calculation with vane shear test val-ues significantly. Secondly the measurement of dynamic sinkage prior to crawler operation on the deep sea soil is not necessary because of its marginal influence on the resistance forces of the crawler. Finally the crawler vehicle as online measurement device is suggested.

The anew up-to-dateness of manganese nodule mining has revitalised the development of mining technology development internationally, not being influenced by the financial crisis of the years 2008 and 2009.