Deep ocean cobalt crust is about 5cm thick and as hard as coal. For mining the crust, a drum cutter similar to that for mining coal was conceived. A cutting model was proposed to describe the cutting process of a single tooth, the forces on the tooth were analyzed and the cutting force was calculated. The model and the analysis will be of great help to the design of the drum cutter upon taking into account the associated engineering issues and equipment design in operating 800–3000 m depth in the ocean.
As we know, there are much more mineral resources on the sea floor than on the land (Manheim, 1986; Manheim, 1988). Since the mineral resources on the land are being used out, mankind has to turn to the ocean and exploit the mineral resources on the sea floor. Currently, many countries are competing to exploit the mineral resources on the sea floor. China has taken thirty years of great efforts to have an area in international seawaters. In this area, there are enormous amounts of cobalt crust. The curst is variable in its thickness, ranging from 1cm to 15cm, mostly from 4cm to 6cm. Its color is black red, its surface, in the shape of smooth grape, sometimes, flat and smooth. The crust is directly contacted with undersea hill side slope rock, with no sediments between them. The seabed rock is generally alkaline basalt, degenerative basalt or glass fragmentary rock (Bu and Qiu, 2002). The density of the crust is between 1.6g/cm3 and 2.17g/cm3, its compressive strength, between 0.5MPa and 16.8 MPa (Yamazaki and Sharma, 1998; Yamazaki and Sharma, 2000). As far as the strengths are concerned, the crust is equivalent to the coal and can be considered to be a kind of soft rock.