This project is a great reference for the construction and design of similar pipe-pile combined retaining wall systems that OSP specialises in providing, and of which we have 20 years of experience applying to the precise and diverse needs of each project we’ve encountered.
The Honghua Marine Construction Base in Qidong City, Jiangsu province has a 22,000 tonne Truss Arched mobile crane installed. This is a large-scale offshore platform equipped with hoisting equipment, jointly developed and manufactured by Honghua Group Co. Ltd and Wuqiao Heavy Industry. The overall height of the equipment is 150 meters, with a maximum lifting height of 71,38 meters and weighing 14,800 tonnes
The terminal adopts the layout of a dub-in basin, and has a plane dimension of 150m x 110m. The overall Honghua harbour is 162m long, with a land track of 143m. It consists of a shipping port pool as well as the delivery station.
After further research and product comparison, OSP was chosen to apply the integrated unloading piling terminal structure. The structure of integral unloading type slab-pile wharf combined with an structure of Honghai track Foundation and Port Pool.
The terminal structure here uses a combination of φ1219*18 pipe piles as well as AZ20-700 steel sheet piles to form a combined pipe-sheet pile retaining wall. The φ1 219 pipe piles are used as the primary pile in order to increase the wall’s resistance to bending moments as well as allowing it to withstand greater lateral horizontal force, while the AZ20-700 sheet pile acts as an auxiliary connection pile to transmit land and water pressure back to the main pipe piles. These auxiliary AZ sheet piles are connected to the steel pipe piles through locking buckles which allow a certain degree of rotation. At the same time, the AZ piles are doubly piled with pressure points only at the top, allowing the sheet pile arrangement to be adjusted as necessary.
Due to a heavier than usual standalone and hoist weight (compared to regular terminal load weights), as well as large structure and lifting heights, the level of horizontal thrust and torque produced during usage of the harbour as well as horizontal wind forces will have a greater impact on the terminal structure here. It is imperative therefore that the structure we built has to meet the intense requirements for vertical and horizontal bearing and displacement, especially since the level of precision required in the heavy marine product industry is extremely high.
This type of unloading type bearing platform can withstand large track loads while meeting strict deformation control requirements. When combined with the pile foundation layout, the forefront of the base slab has an area of 10.5m with a thickness of 4.3m, while the back is 14.5m with a thickness of 2m. The total length of the front slab is 25m, and because of its increased width what results is an overall more effective unloading experience. The front slab has an elevation level of 0.5m above ground level.
By combining an extensive knowhow of our products as well as the geotechnical expertise of our engineers, we concluded that with these soil conditions it was possible to provide auxiliary sheet piles that are actually shorter than the primary piles while still retaining maximum efficiency and stability. This helped our client save significant costs for the project as we managed to reduce the length of the auxiliary pile by at least 25% the original length of the primary pile (the primary piles used here were 41.5 – 43.3m long, while the auxiliary piles were only 30 – 31m long).
For the installation and construction of the combination wall, we firstly had to sink the main pile and subsequently sink the auxiliary piles, utilising vibratory piling first and impact hammer driving after. The main equipment involved here was the DZJ200 vibrating hammer, a 120 and 250 tonne crawler crane as well as a land-pile driver.
During the driving process of this project, strict controls and regulations were maintained in order to uphold the position and vertical deviation of the main and auxiliary piles. The entire project falls strictly within with relevant construction deviation thresholds. Installation began March 2013 and successfully completed end of the following year, with all primary and auxiliary piles sunk in.
When drilling in the project area began, it was revealed that
1. The strata between the surface all the way to elevation levels of -17m consisted of artificial fillings and silt,
2. The -17m til -28m elevation levels consisted a thick layer of muddy, silt-based clay
3. The -28m to -40m elevation levels consisting of non-muddy silt-based clay.
This created a unique environmental combination that our engineers immediately capitalised on to save costs for our clients: