This study investigates the ultimate lateral unit earth pressure of rigid tetrapod foundation imposed by eccentric loads, based on a couple of two-dimensional adaptive finite-element limit analyses with lower-bound, upper-bound and 15-node mixed Gauss element formulations. A parameter study is conducted to emphatically explore the influence of eccentricity as well as to assess the role of additional parameters such as soil-pile interface strength and pile spacing on the normalised lateral earth pressure factor N_p. Results from the numerical analyses reflect that the presence of loading eccentricity may lead to significant reduction in lateral soil resistance, the maximum diminution is up to 45% for the case that eccentricity equals to 0.5 times spacing. Three representative failure mechanisms are identified associated with various eccentricities. Pile spacing and interface strength additionally affect the variation of failure mechanisms with eccentricity increases. Finally, the eccentricity reduction factor, defined as the ratio of the N_p considering the effect of loading eccentricity to the N_p omitting this effect, is proposed, and the variation of this factor with eccentricity is presented for different values of pile spacing and soil-pile adhesion factor.

中文翻译：

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偏心率对粘土中四脚桩极限横向单位土压力的影响

本研究基于具有下限、上限和 15 节点混合高斯元公式的二维自适应有限元极限分析，研究了偏心荷载施加的刚性四脚架基础的极限横向单位土压力。进行了一项参数研究，着重探讨偏心率的影响，并评估土桩界面强度和桩间距等附加参数对归一化侧向土压力系数N _p的作用. 数值分析结果表明，加载偏心的存在会导致土体侧向阻力显着减小，在偏心等于0.5倍间距的情况下，最大减小量可达45%。确定了与各种偏心率相关的三种代表性故障机制。随着偏心率的增加，桩间距和界面强度还会影响破坏机制的变化。最后，提出了偏心减少系数，定义为考虑荷载偏心影响的Np_{与忽略该影响的Np}之比，并给出了不同桩间距和土体值时该系数随偏心度的变化情况-桩粘附系数。