PHC管桩土塞胀管作用定量分析

沉桩过程中,PHC管桩内形成的土塞将对桩内壁产生横向胀管作用。建立了PHC管桩土塞胀管作用的力学模型,并进行了定量分析。考虑沉桩扰动影响,将管内土塞分为楔形区和非楔形区,对土塞的一维平衡方程进行了修正。应用圆柱孔扩张理论解释管桩沉桩过程中的挤土效应,对桩外土体进行了弹塑性分析,得到了塑性区半径以及考虑土体初始应力的桩外土侧压力的解析表达式。根据圆环受均布内外压力的拉梅解答,给出了管桩环向破坏的判别准则。通过现场实测对模型进行了验证,对环向箍筋动态应变的测试结果表明,所建立的模型能够定量描述强胀管作用下PHC管桩的环向破坏机制,可用于工程中PHC管桩环向抗拉承载力的验算。

Quantitative Analysis of Soil Plug Expansion Effect of PHC Pipe Pile

When a PHC pipe pile is driven into the ground,the lateral pressure provided by the soil plug may lead to hoop failure of the PHC pipe pile.In this paper,the mechanical model of the expansion effect of soil plug is established,and the quantitative analysis is carried out.Considering the disturbance of piling,the soil plug is divided into wedged zone and unwedged zone,and an improved one-dimensional equilibrium equation of soil plug is derived.The cylindrical cavity expansion theory is used to explain the compaction effect of PHC piles.It is assumed that the external soil is in elastoplastic state,and the expressions of radius of plastic zone and lateral earth pressure which consider initial stress are deduced.According to the Lame solution of axial symmetrical ring,the rule to judge hoop failure is given.At last,the rationality of the model presented in this paper is verified by a practical example.In-situ test results of hoop stirrup strain indicate that the model can quantitatively describe the hoop failure mechanism of PHC pipe piles,and can be useful for checking calculation of hoop tensile resistance.