泥水盾构施工引起的地面固结沉降实例研究

摘要

Extensive analysis of consolidation settlements induced by slurry shield tunnelling in construction of Hangzhou Qiantang River Tunnel was executed to explore their characteristics. A practical method to distinguish the consolidation settlements from immediate settlements was put forward. Formation mechanism, influencing factors, and control measures of consolidation settlements due to slurry shield tunnelling were summarized. This case study shows that: ①Both immediate and settlement long-term ground surface settlement in the transverse direction can be fitted using Peck equation with great precision. ②The transverse ground surface consolidation settlements usually do not conform to Gaussian curves. Maximum consolidation settlements develop at the ground surface above the tunnel centre or in the vicinity, from where they descend gradually with increasing distance. ③ Consolidation settlements contribute to widening the settlement trough width. ④The time corresponding to the turning point in settlement-time curve or settlement rate-time curve is proposed to be chosen as boundary to divide the immediate and consolidation settlements. ⑤Optimized control of slurry shield excavation parameters contributes to smaller disturbances to surrounding soils, consequently lowering consolidation settlements and their duration.%通过对杭州钱塘江隧道泥水盾构施工的分析,研究了泥水盾构施工引起的地面固结沉降的特点,提出划分地层损失沉降和固结沉降的实用方法,总结了盾构施工引起扰动土体固结沉降的机理、影响因素及控制措施.分析表明:无论是地层损失沉降还是长期沉降,均可用Peck公式较好地拟合；横向地面固结沉降曲线不符合高斯曲线形式,一般隧道轴线或附近地面固结沉降最大,向两侧递减；扰动土体固结使得横向沉降槽不断拓宽；软土地区盾构隧道施工,可取地面沉降曲线或沉降速度曲线的转折点作为地层损失沉降和固结沉降的界限；通过优化泥水盾构掘进参数,可减少施工扰动,从而降低固结沉降量和固结沉降时间.