小净距隧道下穿既有建筑物稳定性研究

Study on Stability of Small Clear Distance Tunnel Underpassing Existing Building

近接施工引起的结构稳定性一直是城市地下工程关注的热点问题。以合肥小净距隧道穿越利海大厦办公楼工程实践为依托,建立三维数值力学模型,研究建筑物桩基变形特性、小净距隧道围岩塑性区分布和衬砌力学响应。研究结果表明:上台阶开挖引起桩基沉降占整个断面通过后总沉降量较大比例,上台阶施工过程控制尤为重要;接近隧道入口的桩基沉降量最大,从外向内逐渐减小;隧道通过20 m后,桩基沉降基本稳定。小净距隧道围岩塑性区主要集中在边墙、中隔墙和拱脚,建议设置中隔墙对拉锚杆和拱脚锁脚锚杆;先行洞洞周变形大于后行洞,先行洞隧道拱肩、中夹岩柱侧边墙二次衬砌安全系数最小,应作为施工阶段重点监测部位。研究成果对复杂环境城市地下工程设计、施工提供参考和借鉴。

The stability of approaching construction has been a focus in the field of urban underground engineering. Based on a small clear distance tunnel underpassing office building of Lihai mansion in Hefei, three-dimensional numerical model is established to investigate deformation characteristics of building pile foundation, distribution of surrounding rock plastic zone of small clear distance tunnel, and mechanical response of lining. The results show that most of the settlement of pile foundation takes place during upper bench excavation and the control of upper bench excavation is of special importance. The settlement of pile foundation at the entry of tunnel dominates and decreases from extroversion to introversion. When the working face of tunnel advances 20 m the settlement of pile foundation tends to be stable. As the plastic zone of small clear distance tunnel concentrates at side-wall, mid-partition wall and arch-footing, it is suggested that tensile-type bolts should be installed at mid-partition wall and locking anchor adopted at arch-footing. The deformation of first-excavation hole is more than that of subsequent hole. The safety factors of lining at spandrel and side wall close to mid-partition wall are the minimum, where special monitoring should be addressed. The research results can supply to the design and construction of urban underground engineering in complicated environment.