CAJ | 학술논문

既有建筑下增层开挖对已有桩基础的影响不同于基坑开挖对坑内桩基的影响。基于工程实例验证的有限元参数，用硬化土弹塑性模型模拟土体，用接触面单元模拟桩土相互作用，建立了桩筏基础-地基-增层开挖三维有限元模型，对增层开挖后群桩基础的竖向承载性状进行研究。分析了桩顶刚度、桩身轴力、桩侧摩阻力、桩端阻比以及土体回弹的变化规律，并研究了不同桩端土体刚度和增层开挖深度对这些参数的影响。结果表明，增层开挖后群桩中不同基桩表现出不同的承载性状，增大桩端土体刚度可明显提高单桩承载力和端阻比临界值；随着增层开挖深度的增加，侧阻和端阻的发挥程度也随之提高。研究结果有望为地下室增层开挖施工中的结构托换变形控制和补桩设计提供依据。
기유건축하증층개알대이유장기출적영향불동우기갱개알대갱내장기적영향。기우공정실례험증적유한원삼수，용경화토탄소성모형모의토체，용접촉면단원모의장토상호작용，건립료장벌기출-지기-증층개알삼유유한원모형，대증층개알후군장기출적수향승재성상진행연구。분석료장정강도、장신축력、장측마조력、장단조비이급토체회탄적변화규률，병연구료불동장단토체강도화증층개알심도대저사삼수적영향。결과표명，증층개알후군장중불동기장표현출불동적승재성상，증대장단토체강도가명현제고단장승재력화단조비림계치；수착증층개알심도적증가，측조화단조적발휘정도야수지제고。연구결과유망위지하실증층개알시공중적결구탁환변형공제화보장설계제공의거。
The effect of further downward excavation beneath an existing building on the pile foundation is different from the one encountered in a newly-created excavation case. Based on the finite-element parameters derived from a case history, a hardening-soil model and a contact-surface model are adopted to simulate the characteristics of soil and the pile-soil interaction, respectively. The three-dimensional finite element framework takes into account the interaction of piled raft foundation, ground and excavation, and is able to investigate the vertical bearing behavior of the existing pile groups after the excavation. The investigation accounts for the effects of end-bearing soil stiffness and excavation depth on the variation trends of pile-head rigidity, pile force, pile shaft resistance, ratio of pile base resistance and soil rebound. The results show that individual piles in an existing pile group subjected to further excavation behaved differently. Increasing the stiffness of the end-bearing soil is crucial to enhancing pile capacity and the critical ratio of pile base resistance. The excavation depth is a key factor that positively influences the mobilization degree of the shaft and base resistances of existing piles. The present results are possible to assist the deformation control of structure underpinning and the design of supplemented pile for further excavation under existing basement.