超长桩基础极限荷载判定的比能对比法

Correlation Method of Specific Energy to Estimating the Ultimate Load of Super-long Pile

超长桩基础广泛应用于高层建筑、超高层建筑、大型枢纽工程其极限荷载的判定直接影响到工程建设的安全性和经济性。桩土系统比能由体积变化比能和形状改变比能构成,明确了系统比能的改变将导致桩土系统稳定状态的变化,提出超长桩基础极限荷载判定的比能对比法,即当系统比能超过桩周岩土材料抗剪强度时(u/τ_(e)>1),桩周土材料塑性区连通而破坏;当u/τ_(e)=1时,桩基础处于破坏临界条件,桩顶荷载为极限荷载。采用比能对比法、P-s曲线拐点法、LogP-s曲线法、Δs/ΔP-E曲线法,判定预制预应力方形桩、大直径灌注桩的两种桩型、7根超长桩基础的极限荷载,四种方法判定的极限荷载一致,说明比能对比法可以适用于超长桩基础的极限荷载判定。

Super-long pile foundation is widely used in high-rise buildings,super high-rise buildings and multipurpose project,and estimation of ultimate load affects the safety and economy of engineering construction.The specific energy of the pile-soil system(EDPS)consists of the specific energy of volume change and the energy density of shape change.The EDPS change will change the stability of pile-soil system.The correlation method of specific energy(CMED)estimating the ultimate load of super-long pile under pressure was put out.When u/τ_(e)>1,the plastic zone of the soils around pile connected and the pile-soil system failed.When u/τ_(e)=1,the pile foundation was in the critical condition of failure,and its load on pile top was the limit load.Used CMED,the inflection point method of P-s curve,the method of LogP-s method and the method ofΔs/Δp-E,the ultimate loads of 7 super-long pile of the pretstressed precast square pile and the cast-in-place of large diameter pile were estimated.The estimations of ultimate load were the same.These indicated that CMED might be used to estimate the ultimate load of the superlong pile foundation.