摘要
软土地区,应用Prandtl地基承载力计算式验算墙底抗隆起稳定性安全系数存在两个问题:一是不能反映随着围护体插入深度的增加,墙底抗隆起稳定性安全系数也随之增大;二是不能体现基坑宽度对墙底抗隆起稳定性安全系数的影响。本文在分析基坑开挖卸荷与应用Prandtl公式计算地基承载力的力学边界条件差异的基础上,认为现有的Prandtl计算式不足以反映基坑隆起破坏滑动模式;依据极限平衡计算原理,提出考虑围护体墙底以上基坑内外两侧土体抗剪作用的改进计算模式。按基坑宽深比为3的标准划分宽、窄基坑,并分别给出宽窄基坑抗隆起稳定性安全系数计算式。通过工程实例计算表明:本文提出的改进公式与成功实施的工程实例安全状况相符,能解释在软土地区随着围护体插入比的增大,基坑抗隆起稳定性得到提高的规律;按照宽窄基坑划分,可以合理计算窄基坑的抗隆起稳定性安全系数。本文研究结果可有助于软土地区基坑抗隆起稳定性计算评价和基坑围护结构的优化设计,也有待于进一步理论研究的补充完善和工程实践的验证。
In soft soil areas, there are two problems in checking the stability against basal heave using Prandtl foundation bearing capacity calculation formula. First, the formula can’t reflect that the stability against basal heave increases with the increase of enclosure insertion depth;Secondly, it can’t reflect the influence of foundation pit width on the safety factor of anti-uplift stability at the bottom of the wall. The analysis of the difference of mechanical boundary conditions between excavation and the bearing capacity by Prandtl formula indicated that the existing Prandtl formula is not enough to reflect the uplift failure sliding mode of foundation pit. According to the principle of limit equilibrium calculation, this paper proposes an improved calculation model considering the shear action of soil on both sides of foundation pit above the bottom of enclosure wall. The wide and narrow foundation pits are divided under the standard ratio 3 of foundation pit width-depth. The formulas for calculating the stability against basal heave of the wide and narrow foundation pits are given respectively. The calculation of engineering examples shows that the improved formula is consistent with the safety situation of successful engineering examples. It explains the law that the stability of foundation pit against basal heave is improved with the increase of enclosure insertion ratio in soft soil areas. According to the division of wide and narrow foundation pits, the safety factor of against basal heave stability of narrow foundation pits can be calculated reasonably. The research results of this paper can contribute to the calculation and evaluation of stability of foundation pit against basal heave in soft soil area, and to the structure optimization design of foundation pit. It also needs to be supplemented and improved by further theoretical research and verified by engineering practice.
作者
阳吉宝
黄星
YANG Jibao;HUANG Xing(Shanghai Municipal Engineering Design Institute(Group)Co.,Ltd.,Shanghai 200092,China)
出处
《工程地质学报》
CSCD
北大核心
2023年第1期341-349,共9页
Journal of Engineering Geology
