Research On The Application Of Superfluid Concrete Cast-in-place Pile In Subway Foundation

With the rapid development of urbanization,the construction of subway is in the stage of rapid development,and the requirements for pile foundation are getting higher and higher.In addition to ensuring the construction quality and construction schedule,new requirements are put forward for the environment,cost and other aspects.As a kind of concrete material with high mobility and no need to vibrate,superfluid concrete can form dense concrete blocks by itself,which can effectively solve the problems of high-density reinforced parts and not easy to vibrate.But the application of superfluid concrete in the pile of subway foundation pit is not very common.Therefore,in this paper,the foundation pit of a standard section of section 4 of Shenyang metro line 9 is studied to optimize the design of superfluid concrete cast-in-place piles,analyze the proportion of superfluid concrete,study the reasonable pile spacing,and optimize the design of foundation support.Through to the superfluid concrete liquid and mineral admixture and discussing the mechanism of action,and then optimize the superfluid state of concrete mixture ratio design,and test the performance of new cooperate with concrete have surplus flow concrete coarse aggregate particle size should be less than 25 mm,the dosage of the cementing materials should not be less than 510kg/m~3,the concrete good liquidity,resistance separation capability is strong,can meet the construction requirements.Subsequent papers in Shenyang sand area and superfluid concrete pile soil interaction study,the results show that with the increase of pile spacing,pile soil arch between rise gradually increase,the influence of the soil arch also gradually increased,the pile spacing between 2 d to 4 d,the soil arch will load transfer between pile to pile on the ability of basic same,between the pile spacing is 6d-8d,soil arching effect scope above 6 m,the soil arch stability obviously.Therefore,the reasonable pile spacing is between 2d-4d.At the same time,the characteristics of the contact surface between the pile and the soil have little influence on the soil arch effect.Finally,the paper uses Midas finite element analysis software to simulate the excavation of the foundation pit,and makes a comparative analysis with the actual monitoring data,and concludes that the foundation pit is always in a stable state during the excavation process,and the model can effectively simulate the deformation of the retaining structure and ground during the excavation process.The application of steel support prestress has little effect on the uplift of the ground near the foundation pit,but it can significantly reduce the final settlement of the ground.The uplift of the ground near the foundation pit during excavation is mainly caused by the deformation of the retaining structure driven by the rebound of the bottom of the pit.Under the condition of timely erection of concrete between supporting and jetting piles,pile spacing can be increased to2.5m,which has achieved the goal of reducing project cost.