增层开挖条件下地基反力对托换桩屈曲稳定临界荷载的影响研究

Influence of Excavation Beneath Existing Building on the Critical Buckling Capacity of Underpinning Pile with Complicated Subgrade Reaction Modulus

为研究既有建筑地下增层开挖条件下,复杂地基反力模式对托换桩桩身屈曲稳定临界荷载的影响,以甘水巷3号组团地下室建设工程为背景,假定桩周土层地基反力系数呈复杂的幂级数分布,采用Winkler弹性地基梁理论建立桩-土体系总势能方程,结合最小势能原理,获得既有建筑地下增层开挖中托换桩桩身屈曲稳定临界荷载表达式,并对其影响因素进行分析。结果表明:不同开挖深度及幂级数对应着不同的收敛半波数;当半波数等于99时,不同开挖深度及不同幂级数情况下的托换桩桩身屈曲稳定临界荷载均已收敛;托换桩屈曲稳定临界荷载比随幂级数的增大而急剧增加,随开挖深度的增加而减小;当幂级数为2和3时,其与开挖深度之间的关系基本一致。

In order to analyze the influence of complicated subgrade reaction modulus on the critical buckling capacity of underpinning pile under the condition of excavation beneath existing building.Based on the case history of No.3 subsection of Ganshuixiang construction project,the most generalized power distribution of subgrade reaction modulus is assumed.the total potential energy of pile-soil system is established by the theory of Winkler elastic beam.The expression of critical buckling capacity is obtained by the principle of minimum potential energy.Then the influencing factors of critical buckling capacity of underpinning pile are analyzed.The result shows that convergent half-wave number varies with the excavation depth and power;when the convergent half-wave number is 99,the critical buckling capacity of underpinning pile with different excavation depths and different power has converged;the ratio of critical buckling capacity of underpinning pile increases rapidly with increasing power,while it decreases with an increase in excavation depth;the relationship between power and excavation depth is similar when the power is 2 and 3.