Preparation And Engineering Characteristics Of Grouting Shaped Root Piles After Prefabrication

In order to fully implement the concept of sustainable development and prolong the service life of Engineering structures,the existing building reinforcement technology plays an increasingly important role in the construction industry and economic construction in China.Among them,improving the existing foundation reinforcement technology can solve the problems of long construction period and low post-pouring strength of cast-in-situ piles in the current soft soil foundation reinforcement technology.A new type of precast grouting special-shaped root pile has been prepared.It can not only be used in the reinforcement of small space soft foundation,but also has the advantages of small construction area,fast construction speed and high economic benefits.Through theoretical analysis,indoor and field tests,the design parameters,preparation technology,construction technology and bearing characteristics of the pre-grouted special-shaped root pile are systematically studied.The main work and achievements are as follows:(1)The mechanical mechanism and bearing characteristics of special-shaped root piles at home and abroad were analyzed.By referring to the construction technology of post-grouting pile,a new type of pre-grouting special-shaped tree-root pile was designed for the reinforcement of soft foundation in existing buildings.Twelve piles with different diameters and connection modes were prepared.The mechanical properties and connection technology of piles were studied through indoor mechanical properties test.The test results meet the design requirements.On this basis,the design parameters and preparation technology of piles were optimized,and the pile-making mould was improved.(2)Fifteen pre-grouting special-shaped tree-root piles with 250 mm outer diameter and 1m pile length were manufactured by using the optimized parameters and technology.Field piling tests were carried out on pre-grouting special-shaped tree-root piles with matching mini-pile driver,and post-grouting construction operation was carried out to verify the feasibility and applicability of the post-grouting construction technology.Construction technology of pre-grouting special-shaped tree-root piles was summarized.It has engineering reference value.(3)Field static load test of precast grouted special-shaped tree-root pile was carried out.Through the Q-s curve obtained from the test,the bearing and settlement characteristics ofprecast grouted special-shaped tree-root pile are analyzed,and the ultimate bearing capacity of single pile was determined.The results show that the grouting special-shaped root pile has a good effect on foundation reinforcement.(4)Based on pile foundation theory and field test results,the interaction between special-shaped piles and soil around piles was analyzed.Through the study of pile hole expansion process and grout diffusion,shape correction coefficient and grouting reinforcement coefficient were introduced.Based on the current pile foundation code,formulas for calculating the bearing capacity of single pile under non-grouting and grouting conditions were given respectively.The settlement correction coefficient was introduced and the settlement correction formula of precast grouted special-shaped root pile was given.