既有深基坑扩建时新支护方案的选择与优化

本文介绍了某已支护深基坑工程扩建时新支护方案设计的工程实例。介绍并比较分析了土钉墙与桩锚联合方案、砖挡墙与桩锚联合方案、微型桩—直立土钉墙联合方案和微型桩—放坡土钉墙联合方案等四种支护方案。通过分析比较确定了相对适宜的支护方案,并结合工程实际给出了优化建议。分析认为,既有深基坑扩建时侧壁土体应力状态和强度参数及新支护体系的工作状态均不同于新建基坑,因此,为扩建既有基坑设计新支护方案时必须考虑已有支护结构的影响,应考虑已有支护结构的可利用性、施工措施的可行性、新旧支护结构的匹配性和与周边环境要求的适应性等因素。

Selection and optimization of the new supporting system for expanding a supported deep foundation pit

This paper presents an engineering example in designing a new supporting system for expanding an existing and supported foundation pit. Four alternative supporting systems such as soil nailing combined with pile-anchor system, brick retaining wall combined with pile-anchor system, micro-piles combined with vertical soil nailing wall and micro-piles combined with sloping soil nailing wall are introduced and comparatively analyzed. Through analysis and comparison the relative appropriate support systems are selected and optimization proposal is given. Case analysis shows that the stress state, soil strength parameters of the existing pit wall and the working conditions of new supporting system are also different from that of the new pit. Therefore, the influence of existing support structure must be taken into account during the design and construction of the new supporting system while expanding an old pit. Many important aspects should be considered such as the probability to re-use the existing supporting structure, the feasibility of construction measures, the matching between the old and the new supporting structure and the adaptability of the new system to the surrounding environment.