Pile foundation construction of Zhejiang LNG Phase III project receiving station tanks is located in Ningbo City, Zhejiang Province, invested by CNOOC Lvnengang Zhejiang Ningbo Energy Co., Ltd. The scope of construction includes pile foundation of 1#, 2#, 4# storage tanks, and a total of 1,027 piles with pile diameter of 1,500mm and pile length of 7m～63.26m have been completed.
The difficulty in the construction process of this project lies in the casing lowering, due to the construction area is a block stone backfill layer, the stratum is complicated, this project adopts the double casing method to cross the deep block stone backfill layer, to ensure that the mud is not leaking out and the hole is not collapsed. Double casing is one large and one small casing, the large casing is 3.0m long, the small casing is determined according to the depth of the backfill layer, and the inner diameter of the large casing is 10cm-20cm larger than the outer diameter of the small casing. In order to realize the method of graded lowering of large and small casing. Firstly, lower the large casing, after the large casing is lowered, then according to the deviation, use the small core barrel to drill downward, when crossing the backfill layer, then lower the small casing, after the positioning of the small casing is completed, pull out the outer large casing, and then fill the small casing around with clay, and then use the drilling rig to squeeze and compact, and then complete the casing placement. This method effectively solves the problem of placing casing in the super-thick backfill block layer, ensures that no hole collapses in the process of casing placement, and the outer side of the small casing is densely packed with clay, so that the mud will not leak out, thus achieving the effect of protecting the environment, reducing the quality hazards, and saving the cost.
The pile foundation construction of this project started on October 03, 2021 and was concluded on June 18, 2023. After third party testing, the pile foundation construction meets the design and specification requirements with a 100% pass rate.
