The first phase of CNOOC Longkou Nanshan LNG receiving station project (hereinafter referred to as "Longkou LNG") is located at the planned LNG zone in the operation area of Longkou Port, Yantai Port, Longkou City, Shandong Province, and the project started on April 15, 2020 and completed on April 1, 2021, lasting 351 days. The main workload completed includes all the work related to T-0201, T-0202 storage tank pile foundation project, including cast-in-place pile construction (720 piles with a diameter of 1.5 m, pile length of 9.86m ~ 41.8m, concrete grade of C40P8) with a total of 40,765.71m ³、rebar cage fabrication with a total of 3,564.846 t, sonic logging pipe installation with a total of 8601.59 m, stone column construction (3497 piles with pile diameter of 1 m, pile length of 8 m) with a total of 21972.3m³, transportation of 39,358.86m³ rotary excavation spoil, 720 sets of holes reserved for installation of vibration isolation mats (number of holes for single pile is 10, hole length is 0.9 m, hole diameter is 80 mm), advance drilling of 5,247.5 m.
The pile layout of this project is gravel pile around the grouting pile, so the 8m long gravel pile is constructed first and then the grouting pile, the distance between gravel pile and grouting pile is only 0.38m, the hole wall is easy to collapse when the grouting pile is formed and cannot be drilled into the hole, by using vibratory hammer to sink and pull the 10m long steel casing and using integrated pile formation method, it greatly improves the quality of pile formation. During the construction process, the actual rock surface depth was different from the survey report, and the rock layer was complicated, so the bedrock determination efficiency was low, and the accuracy was poor. The accurate location of the bedrock surface was detected by advance drilling construction, which improved the efficiency and accuracy of rock determination and ensured the quality of piling. Because of the long and large diameter of the cage, the number of thick main bars, and the main bars are mechanically connected, the cage fabrication is difficult, by using electric wrench for mechanical connection of the main bars, it greatly improves the production speed of the cage. The top of each cast-in-place pile of the project needs to reserve 10 isolation rubber pad installation holes (diameter of 80 mm, hole depth of 900 mm), which are evenly arranged along the circumference with the pile center as the circle center, with high accuracy requirements and great construction difficulty. The quality and accuracy of the reserved holes are guaranteed by using the integral formwork support to locate and embed the bellows.
The project has been accepted by the owner, supervisor, general contractor, design organization and investigation organization, and the overall quality of the project is assessed as qualified. Stone columns and cast-in-place piles have passed the third-party test, and the test results are qualified, with a qualified rate of 100%. Among them, 720 piles were detected with low strain, 99.3% of which were Class I piles and no Class III or IV piles. 72 piles were tested by cross hole sonic logging, 100% of which were Class I piles and no Class III and IV piles. 8 piles were detected by single pile vertical compressive static load, and the single pile vertical compressive bearing capacity characteristic value is 10000KN, meet the design requirements. 40 groups of cone dynamic penetration test showed that the pile body has good continuity and the compactness is slightly dense to dense. Standard penetration of 40 groups, liquefaction had been eliminated.
During the whole construction process, no safety and quality accidents occurred, the project quality was excellent, HSE management was controlled, progress met the requirements, and all indicators met the contract requirements, which was recognized and praised by the supervisor, general contractor and owner. Due to the excellent performance of the company, the EPC project team of Longkou LNG commended the company and individuals, awarded the company as "Advanced Organization of Quality Management" and "Advanced Organization of HSE Management", and many team members were awarded as "Excellent Project Manager", "Advanced Individual of Quality Management" and "Advanced Individual of HSE Management".
