【摘要】 旋挖钻孔灌注桩在不稳定地层施工过程中因成孔质量差造成混凝土充盈系数过高,严重影响工程效益。基于此,分析了混凝土充盈系数的影响因素,在工程现场泥浆具有局限性的的情况下,可以从控制最大允许提钻速度和改进钻头结构两方面开展研究工作。建立了最大允许提钻速度的理论计算模型,获得了环空比和泥浆密度对最大允许提钻速度的影响规律和显著性。针对具体工程地质条件,采用两瓣斗钻头结构,并从辅助排水孔和非光滑结构的合金球加强型截齿等方面进行改进设计,以提高旋挖钻进和排渣效率,从而降低成孔时间。现场试验结果表明,通过控制提钻速度和改进钻头结构,单桩旋挖成孔时间缩短28.57%,旋挖钻孔的混凝土充盈系数降低3.62%,显著节约了项目施工成本。更多还原

【Abstract】 During the construction of cast-in-place piles by rotary drilling rig bit in the instable formation, low hole quality usually results in high concrete filling coefficient and more project costs. Aiming at this problem, this paper analyses influencing factors for the filling coefficient and suggests that controlling the maximum lifting velocity and optimizing rotary digging bit structure should be useful when drilling mud has some problems in the construction site. By establishing a theoretical model of the maximum lifting velocity, the effects and significances of annular ratio and mud density to the maximum lifting velocity are obtained. More importantly, ringent bit structure is employed according to a detailed engineering geology condition, and some specially designed characters, such as auxiliary drain holes, non-smooth cutter enhanced by tungsten carbide balls, are applied to improve rotary drilling rig and discharge efficiencies. Field test results indicate that, controlling the maximum lifting velocity and optimizing rotary digging bit structure can shorten the rotary digging time of a single pile by 28.57%, and reduce the concrete filling coefficient by 3.62%. The research results can save construction cost significantly and be helpful for the similar engineering.更多还原