Assessment of the Engineering Properties for Mud Through CPT and VST in Hengqin Coast

With the rapid development of urbanization in China, more and more constructions are carried out in the delta of the coastal area, especially the nearshore embankment projects. Mud or muddy clay are widely distributed in the delta region, which normally has low strength and high sensitivity. The evaluation on the engineering properties of mud is the critical factor for embankment construction, not only for construction expense, but also for the safety. Traditional assessment method of mud depends on the results from laboratory tests of drilling samples, which highly depends on the sample quality. Due to the high sensitivity, it is recommended to use in-situ investigation for the evaluation of the engineering properties. In this research, cone penetration test (CPT) and vane shear test (VST) are performed in 14 locations at Hengqin coast of Zhujiang, Guangdong province. VST results show that the soil sensitivity of mud varies from 3 to 12, and the undrained shear strength su increases with soil depth and expressed by a liner equation. Based on the shear strength obtained from VST, the cone factor Nk of CPT for mud is calibrated for strength interpretation in Hengqin area, which varies from 12.53 to 30.08. The undrained shear strength su′ of remoulded mud is found to be relevant to the sleeve friction fs of CPT, where the calibrated interpretation parameter Nf ranges from 3.93 to 5.66. It is reasonable to use the average value 21.1 of Nk and 4.76 of Nf for CPT interpretation in Hengqin area, which show good agreement with the measured results from VST.