Field Tests of Soft Marine Clay Foundation Reinforced by T-shaped Bidirectional Dry Jet Mixing Piles

In order to overcome disadvantages of the marine soft soil foundation treated by the conventional dry jet mixing(DJM) piles, such as mixing non-uniformity of soil cement and low strength of pile body, a technique of using T-shaped bidirectional DJM piles was proposed to reinforce the soft marine clay foundation in Lianyungang area of China. Single pile tests were conducted in a field site of the Lianyungang-Linyi Expressway (Jiangsu Section). Disturbance effects of DJM during installation and static load test after the construction of the T-shaped bidirectional DJM were analyzed. The dissipation process of the excess pore water pressure after installation, load, and settlement parameters were monitored during the static load test. The results indicate that the excess pore water pressure exceeded the effective overburden stress of the soil during installation, probably due to the larger diameter of upper head of the T-shaped DJM pile and the repeated mixing process. However, excess pore water pressure dissipated quickly just after installation. Single pile installation had an influence scope of 510 times the pile radius. The single pile static load test results indicate that, compared to bidirectional and conventional DJM piles with the same diameter, the ultimate bearing capacity of the T-shaped bidirectional DJM pile increased 36% and 76%, respectively. Therefore, T-shaped bidirectional DJM is characterized by high pile strength and high single pile bearing capacity.