Mechanism And Application Research On Cast-In-Situ Concrete Thin-Wall Cylindrical Pile For Treating Soft Soil At Bridge Bead

Cast-in-situ concrete thin-wall cylindrical pile (Hereinafter referred to as cylindrical pile) is a new type of foundation engineering, has the advantages of convenient construction process, material used saving, high bearing capacity and short construction period, and it has wide application prospect. At present, the test results and theoretical research of cylindrical pile structure are very less and not yet have the mature design theory, so restricting its practice application. Based on site tests, this paper makes an extensive research on cylindrical pile for strengthening soft foundation at bridge head.This article first introduces the general situation of ternary structure and dual structure soil test section, then it provides the calculation method and formula of standard value of ultimate bearing capacity, and the calculation method is verified by the static load test, according to field test, in-situ observation, data analysis and theoretical calculation, finally detects the pile-forming quality status of cylindrical pile; contrasts with the change of inter-pile soil physical and mechanical properties, bearing capacity and surface foundation capacity between the pre-and post pile-forming; studies on the change of cylindrical pile foundation immediate settlement by heaped load effect; analyzes settlement law, vertical and horizontal deformation rule of composite subgrade under action of embankment load; explores the pile and soil stress ratio and strengthening effect by using coverplate on pile top and paving of geogrid. Inspects of the combination of cylindrical pile and water jet graded sandstone mixture effect on treatment of soft foundation; compares the mechanism, strengthening effect, construction technology, quality control and economic benefit of cylindrical pile, dry jet mixing pile and plastic drain plate. Finally, main achievements and conclusions for strengthening soft soil subgrade on cast-in-situ concrete thin-wall cylindrical pile are obtained.Main achievements and conclusions: The cylindrical pile compound subgrade has the advantages of pore-forming advanced craft, the pile's integrity, high bearing capacity, easy to control quality and inspection conveniently. This kind of pile can increase the strength and rigidity of soft soil ground dramatically. The subgrade is stable and can be filled quickly resulting in shorter construction period. The economic and social benefits are obvious. Reinforcement area of settlement is mainly in inter-pile soil, pile top is less settlement, amount of total settlement is small, lessening the vehicle bump at bridge head after construction. By using cylindrical pile compound subgrade, the high embankment section has a good antiskid quality. The calculation method and formula of standard value of ultimate bearing capacity has been worked out. This paper provides a completely new method for solving the quality problems such as bump at bridge head and ground strengthening of building.