摘要
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。
Limit equilibrium theory and variational method are combined to analyze ultimate uplift capacity of excavated foundation of transmission tower. A general shear failure for the soil mass around the tower is hypothesized. The soil stresses satisfy the yielding criteria of Mohr-Coulomb at limit conditions. The ultimate bearing capacities for different loading conditions can be estimated with this method. The effects of soil strength and embedment ratio on ultimate uplift of foundation under centric, eccentric and inclined uplift force are examined with a series of calculations. The influence coefficients of moment and horizontal force are proposed using a normalized processing. When the ratio of normalized moment to uplift force Nm is less than 0.4, the moment influence coefficient ？m declines rapidly with Nm. When Nm is more than 0.4, the decay rate of ？ m becomes slow. Soil cohesion has more significant effects on ？ m than the internal friction angle. The influence coefficient of horizontal loading ？ h is affected by the soil strength and embedment depth simultaneously. The results show the values of ？ h are smaller than those proposed in technical code. The accuracy and reasonableness of the method are verified by comparing test data with the results of formula in code. It can provide a reference for determining uplift capacity of outcrop foundations under eccentric uplift or horizontal force.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2015年第1期163-170,共8页
Rock and Soil Mechanics
基金
国家自然科学基金项目(No.51308095
No.51278091)
中国电机工程学会电力青年科技创新项目(No.20110515)
吉林省科技厅青年科研基金(No.20130522068JH)
关键词
掏挖基础
极限上拔力
影响系数
极限平衡法
变分解法
excavated foundation
ultimate uplift force
influence coefficient
limiting equilibrium method
variational method
