Research On Engineering Properties Of Rock-Socketed Pile In Deep Sea Backfill

With the rapid development of the economy in China, urbanization, industrialization and gathering population to larger pace acceleration, a large area of land in many parts of Chinese has been developed and exhausted basically, Chinese’s coastal cities began to study many coastal countries whose are scarce in the land resources, and start slowly attention to use of the beach or bay waterfront land reclamation, want to land towards the sea to solve the increasingly tense land issues Therefore, a large number of land reclamation projects,and consequential many geotechnical problems also attracted the attention of many experts and scholars.Due to the foundation soil include the original soil and backfill soil in reclamation land reclamation area, According to the original data, the ultimate side friction standard value is not very clear when pile design, if the use of the reported recommended values of its original geological survey data, most likely will have some error also causing many engineering problems such as waste of resources and hidden safety problems The extreme values of the standard end resistance is not clear the surface of fill soil combined with the original soil reclamation is weak there is a big consolidation problem due to recently deep backfill which is easy to produce uneven settlement negative skin friction will produce when using pile This problem has a large overall stability affects on the pile The waterfront of the project, so that the water table is affected by ebb tide of the sea in infrastructure projects When using pile foundation in engineering sulfate ions and chloride ions have a certain degree of corrosion on steel and concrete in seawater of foundation works seriously affect the integrity pile thus reducing its durability. The above circumstances, In this paper, regard field trials and laboratory tests as the main line, discussion on the load transfer mechanism of rock-socketed pile, Introduction of casing construction technique, solved side negative friction of pile in deep backfill, based on accelerated testing to get corrosion properties and corrosion resistance of concrete construction pile mix about concrete against chloride and sulphate resisting. The main work and achievements are as follows:(1) We reviewed the status of pile and the geotechnical problems of application reclamation area, summed up the pile bearing capacity, research progress of resistance to negative friction and durability.(2) Relying a coastal deep backfill engineering project in Qingdao City, by large tonnage static load test of pile and mechanical testing, discussion on the large diameter rock load transfer mechanism of piles and vertical bearing features. The results showed that, Q-s curve gentle of test pile, when load to 16000 k N, the settlement is small, meet the engineering requirements. Under vertical loads, axial force from top to bottom gradually decay, the decay rate is large in the lower part of pile, playing side friction and tip resistance of pile has asynchronous, lateral friction prior to play to the end resistance of pile, and the side frictional resistance of each soil layer measured values increased by 2 to 7 times higher than the recommended value of Geological Survey reported.(3) By analyzing the negative friction causes and mechanism, Introduction of casing construction technique to eliminate negative friction resistance, the test results proved feasible. Through mechanical testing of three test piles found that axial force of backfill soil are close to pile load, pile friction tends 0, pile load borne mainly by soil below the backfill layer.(4) Through the indoor accelerated test simulated field water erosion environment, treat specimen corrosion factor and weight loss as evaluation of corrosion-resistant concrete, research on corrosion bearing performance of pile in new coastal environment. The results show, cementitious materials in an amount of 480 kg / m3, water-cement ratio of 0.32, when using polycarboxylate water reducer, efficient preservative of concrete and organic concrete rust inhibitor, development the mechanical properties of concrete specimens, resistance to chloride ion diffusion and sulfate resistance are optimum, to meet the design requirements of pile concrete in corrosive environment.