土钉墙桩排组合支护基坑土压力和变形分析

Earth Pressure and Displacement of Combined Retaining Structures from Piles plus Soil Nailing Walls

土钉墙和桩排组合支护是基坑工程中一种新的挡土形式,其上部的土钉墙和下部的桩排协同作用,使得它受到的土压力和发生的变形既不同于土钉墙,也不同于桩排支护。针对这种组合支护一基坑实例,用三维数值模拟实验方法,探讨了空间受力与变形的特征。分析结果表明,这种组合支护:(1)实际受到的土压力与由郎肯理论确定的土压力不相同,文中给出了修正系数。与单纯的桩排支护相比,它的被动土压力增加约20%,而土钉墙面层最大土压力则减少了近50%;(2)发生的最大变形与本文提出的组合支护无量纲整体刚度系数相关。相同地质条件下,当整体刚度系数从4 000增加到5 000时,组合支护变形有明显减少的趋势。

The structures formed from soil nailing walls and piles are the new earth-retained walls developed recently in deep excavations.The upper soil nailing walls work together with lower piles as a whole to retain soil.Earth pressure and displacement for the combined supporting structures are thus different with either soil nailing walls or piles.Based on case history in Wuhan,the earth pressures and displacements are investigated using 3D numerical simulation experiments.For the combined structures,analytical results have indicated that（1） actual earth pressures are different from those determined by classical Rankine theory.Coefficients are given to correct the values from Rankine theory.Passive earth pressure increases by about 20% in comparison with that for piles while the maximum earth pressure for soil nailing walls decreases by about 50%;（2） the maximum lateral displacements are associated with the coefficients of integrality stiffness proposed in this study.Under similar geological conditions,as the coefficient increases from 4000 to 5000,the maximum lateral displacement is found to decrease remarkably.