新型预应力钢桁架支护桩设计及应用研究

Study on design and application of new retaining pile with prestressed steel truss

预应力钢桁架作为支护桩尚未在深基坑工程中得到应用。通过分析支护桩受力形态得到其优化线路。以新型预应力钢桁架作为支护桩在实际工程中的应用为例,详细介绍了新型桁架桩的规格尺寸、预应力施加方法、内填水泥浆液的施工方法、桩插入施工的过程等;并以预制预应力混凝土工字桩作为参照组,通过对两者的实测的桩顶水平位移、桩顶沉降、深层水平位移及基坑南侧管线及道路沉降等进行对比,验证新型桁架桩的可行性。结果表明:采用新型桁架桩与工字桩时,两种支护结构桩顶沉降及桩顶水平位移差异不大;基坑开挖面以下桁架桩刚度沿深度减小,这会导致桩体深层最大水平位移的位置的显著下移;基坑南侧管线及道路沉降可满足设计要求。

Prestressed steel truss as retaining pile has not been applied in deep foundation pit.By analyzing the force form of the retaining pile,the optimized route was obtained.Taking the application of the new retaining pile with prestressed steel truss in practical engineering as an example,the specification and size of the new type of retaining pile,the method of prestressing force application,the construction method of filling cement soil,and the insertion construction process of pile were introduced in detail.Taking the precast prestressed concrete I-shaped pile as the reference group,the feasibility of the new truss pile was confirmed by comparing the measured horizontal displacement of pile top,settlement of pile top,deep horizontal displacement and the settlement of the pipelines and roads on the south side of foundation pit.The results show that when the new truss pile and I-pile are used,the pile top settlement and pile top horizontal displacement of the two supporting structure have little difference;the stiffness of the truss pile under the excavation surface of foundation pit decreases along the depth,which will lead to the significant downward movement of the maximum value of the deep horizontal displacement of the pile;the settlement of the pipelines and road on the south side of foundation pit could meet the design requirements.