砂砾石地层桩基拔除施工技术

Construction Techniques for the Extraction of the Pile Foundation from a Sandy Gravel Stratum

为了在富水砂砾石地层中盾构机安全穿越钢筋混凝土桩基础,提出了采用全回转套管机拔除的解决思路。通过对全回转套管机刀尺、刀具的改良,提高钢套筒下压沉入效率;通过对全回转套管机扭矩、压入速度、压入垂直度等参数控制的改进,克服工程遇到的硬土、硬岩等难题;增加气举反循环、注水挖土等工艺清除桩周土,减小拔桩需要克服的摩檫力;在全回转套管机底座加配重稳固机身,减小拔桩过程中套管机振动,确保顺利拔桩。实践证明,采用改进工法进行拔桩时,施工全过程处于安全、稳定、快速、优质的可控状态。

In order to solve the problem in helping the shield machine go safely through the reinforced concrete pile foundation in a rich-watered sandy gravel stratum,put forward in the present paper is a problem-solving idea that the piles be extracted with a full-rotation casing machine.The efficiency of the steel sleeve sinking is improved by bettering the cutting tool and the cutter ruler of the full-rotation casing machine.The problems such as the project encountering hard soil,hard rock or other difficulties are overcome through improving the controlling of the parameters related to the torque,penetration speed and verticality of the full-rotation casing machine.The processes such as the air-lifting reverse circulation and excavation with water injection are used to clear the soil around the pile,which can decrease the friction force when the pile is extracted.The counterweight is added to the base of the full-rotation casing machine to stabilize the machine so as to decrease the vibration of the machine when the pile is extracted and to ensure the smooth and successful extraction of the pile.Engineering practice shows that the entire construction process is kept in a safe,stable,quick and high-quality controllable state when the pile foundation is extracted with the improved construction method for the project.