均质地层中桩筏基础筏板荷载分担比的归一化分析方法

Normalized analysis for pile-raft load sharing ratio of piled raft foundation in homogeneous ground

在进行桩土共同作用的桩筏基础设计时,其核心之一是合理评估筏板的荷载分担特性。为了准确得到筏板的荷载分担比大小,基于桩土筏相互作用理论提出了竖向荷载作用下考虑土体非线性弹塑性的刚性板桩筏基础实用分析方法。在此基础上,进一步分析了土体参数、桩数、桩间距、桩长及桩径对筏板荷载分担比的影响,并根据计算结果提出了考虑基础整体安全系数影响的筏板荷载分担比归一化计算模型。计算结果表明:基础整体安全系数对筏板荷载分担比的大小有重要影响,安全系数越小,筏板荷载分担作用越大;桩数、桩长、桩间距直接影响筏板荷载分担比的大小,但其影响程度存在差别,桩间距影响较显著,桩长次之,桩数影响程度较弱;采用归一化分析模型能较好地统一不同参数对筏板荷载分担比的影响。最后,通过实际工程案例初步验证了归一化模型的有效性。

For the design of a piled raft foundation that considering the pile-soil interaction,one of the key factors is to evaluate the load sharing characteristics of the raft reasonably.In order to determine the load sharing ratio of the raft accurately,a nonlinear elastic-plasticanalysis method for the rigid piled raft foundations under verticalloading is developed based on the pile-soil-raft interactions theory.On that basis,the influences of soil parameters,pile number,pile spacing,pile length and pile diameter on the pile-raft load sharing ratio of rigid piled raft are analyzed further,and a normalized calculation method of raft load sharing ratio is proposed based on a series of calculation results of piled raft under different working conditions.The results show that:the overall safety factor of the piled raft has a remarkable influence on the load sharing behavior of raft,i.e.,the raft load sharing decreases with the increaseof foundation safety factor.Pile number,pile length and pile spacing have a direct influenceon the raft load sharing ratio,but the influence degreesare different.Pile spacing has the most significant influence,followed by pile length,and pile number has the least influence degree.The normalized calculation model can unify the influences of the aboveparameters on the raft load sharing behavior.Finally,the proposed normalized calculation model is verified preliminarily by the collected project examples.