Innovating and Improving the Adaptation of Steel Sheet PileCofferdam in a Complex Environment (Figure)

Award level: Second Prize

Project name: Study of constructiontechnology for steel sheet pile cofferdam of deep water platform in the boulderthick coating

Piling using static pressure pile driver

In recent years, steel sheet pile cofferdam has been widelyused as waterproof cofferdam since it is recyclable, environmental andeconomical. Whereas steel sheet pile cofferdam is often used for clay, silt,medium sand and other stratums, vibratory hammer is often adopted for steelsheet pile construction of highway projects. Under deep water condition ofboulder thick coating, existing construction technologies and methods for steelsheet pile cofferdam can easily cause flooding at the pile bottom when the holeis led to be bottom, and consequently safe and effective construction cannot beguaranteed. For this purpose, the innovation team of CCCC First HighwayEngineering Group First Engineering Co., Ltd. (hereinafter referred to as“innovation team”) developed the construction technology for steel sheet pilecofferdam of deep water platform of boulder thick coating through independentinnovation to further improve the adaptation of steel sheet pile cofferdam in acomplex environment.

Innovating and Improving theAdaptation of Steel Sheet Pile Cofferdam in a Complex Environment

Presently, domestic and overseas test methods for waterpermeability of underwater bed rock mainly refer to acquiring the bed rock tobe tested from the site, carrying out permeability test in the laboratory andobtaining the osmotic coefficient of bed rock. The innovation team inventedquick test methods and corresponding devices for water permeability ofunderground water of the site, and the test data was more reasonable than thoseobtained from indoor permeability test. Meanwhile, the innovation team analyzedthe data obtained from on-site osmotic coefficient test through GTS waterpermeability theory, and the analysis result was consistent with theengineering practice result. It symbolizes a set of more scientific methods fortesting the osmotic coefficient of bed rock.

At present, the steel sheet pile cofferdam is set in the deepwater environment of boulder thick coating and dense sandstone formation, andthere are no documentary records on existing tools and constructiontechnologies. For this purpose, the innovation team developed groovedreplacement technology and drill bit combined steel sheet pile constructionequipment and process. The grooved replacement technology realizes continuousgrooving and bagged fine sand backfill after steel casing follow up. This technologywas first adopted in China and offered references for steel cofferdamconstruction in similar complex geological conditions. The drill bit combinedsteel sheet pile construction equipment and process solved the difficulty ineffectively installing the steel sheet pile in boulder thick coating and densesandstone formation and there were first adopted for the construction ofsimilar bridge projects at home and abroad.

The innovation team broadened the application scope of staticpressure pile driver and improved its use ratio. Featuring advanced technology,convenient construction, concise and efficient, and pile verticality up to0.8%, this technology effectively ensured to drive the steel sheet pile intothe virgin stratum in the anchoring stratum according to the piling path, andultimately the steel sheet pile pressing technology combining twist drill andstatic pressure pile driver was formed.