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针对输电线路掏挖基础极限上拔承载力问题,根据塑性极限平衡原理,假设基础周围土体发生整体剪切破坏并服从Mohr-Coulomb破坏准则,建立静力学平衡方程式,并结合变分法原理求解不同加载条件下基础的极限抗拔力。通过变参数计算,分析土体强度及基础埋深比对中心上拔、偏心上拔及倾斜上拔时基础极限上拔力的影响。经归一化处理,分别给出水平力和弯矩存在对基础抗拔力折减的影响系数。当归一化弯矩与上拔力比值Nm<0.4时,随着Nm增加,弯矩影响系数?m急剧减小;当Nm>0.4时,?m减小速度放缓。相对于内摩擦角,黏聚力变化对?m的影响更明显。水平力影响系数?h同时受到土体内摩擦角、黏聚力以及基础埋深比的共同影响,规范建议值较变分解法的计算结果偏大。通过与规范公式法计算结果及试验结果进行对比,验证了所提方法的合理性和准确性。研究结果为偏心上拔及高露头基础顶部作用水平荷载时基础抗拔承载力的计算提供参考。
According to the principle of plastic limit equilibrium, assuming that the soil around foundation is undergoing total shear failure and obeying the failure criterion of Mohr-Coulomb, the static equilibrium equation is established and solved with the principle of variational method Under different loading conditions under the basic anti-pull force. Through variable parameter calculation, the influence of soil strength and basic depth-to-depth ratio on the pull-out force at the basal upper limit, eccentric pull-up and oblique pull-up is analyzed. After normalized treatment, the influence coefficients of horizontal force and moment on the reduction of basic pullout force are given respectively. When the normalized bending moment and the pull-out ratio Nm <0.4, as the Nm increases, the bending moment? M decreases sharply; when Nm> 0.4, the decrease of? M slows down. Relative to the internal friction angle, cohesion changes? M more significant impact. The influence factor of horizontal force? H is affected by both the internal friction angle, cohesion and the basic depth-to-depth ratio, and the proposed value is larger than that of the variable decomposition method. By comparing with the results calculated by the standard formula method and the test results, the rationality and accuracy of the proposed method are verified. The results provide a reference for the calculation of the basic pull-out bearing capacity of eccentric pull-up and top-out effect of high outcrop foundation.