In-situ shearing strength and penetration resistance testing of soft seabed sediments in western mining area

To obtain the mechanics parameters of the soft deep seabed sediments, the shearing strength and penetration resistance tests were made in Chinese Pioneer Area in the western part of the Pacific with the in-situ testing way. According to the measured data in the 41 sites, the shearing strength and penetration resistance increase with the increase of testing depth till their own peak values then go down in small range. The shearing strength and penetration resistance are very low in the depth from 0 cm to 8 cm and reach their respective peak values in the depth of 40-45 cm, which are 11.8 kPa and 100 kPa, respectively. The soil in the depth 14-20 cm can be used to traction and bear the tracked vehicle because of its homogeneous mechanics characteristic with shearing strength of 5.8 kPa and penetration resistance varying from 46 kPa to 50 kPa. Tooth should work in the depth from 14 cm to 20 cm with the lowest height of 6 cm and the design value of shearing strength around the tooth should be 3-4 kPa. The track shoe should sink to the depth of 14 cm in the stationary state. Four empirical formulas based on the above data can be used to evaluate shearing strength and bearing behavior of the soft deep seabed sediments. The formulas may be used to design the track of the seabed tracked vehicle, especially to determine its grouding pressure.