软土地区土压平衡盾构停机实测分析

Analysis of Ground Responses to Shield Shutdowns in Soft Clay

文章结合杭州软土地层某一地铁区间盾构掘进过程中的两次较长时间停机事故,研究了土压平衡盾构在软土地层中停机期间地层的变形特性。分析结果表明:在盾构停机过程中,沉降影响范围超过5倍盾构直径,远大于正常掘进情况下3倍盾构直径的影响范围;盾构前方土体呈现整体沉降的规律,其沉降槽不能被Peck正态分布公式拟合;在盾构重新启动时,与正常掘进相比,盾构千斤顶总推力急剧上升。究其原因认为,在停机过程中,受扰动结构性软土强度恢复影响,导致盾构与土体之间摩阻力大幅增大所致。本文结果对研究软土地区盾构施工因故停机期间地层及盾构响应特性有一定借鉴意义。

Based on two shutdowns of the EPB shield during construction of a Hangzhou metro running tunnel in soft ground, the law of ground deformation during the stoppage is investigated. The results indicate that： the affected settlement scope is more than 5 times the shield diameter and much higher than 3 times under normal driving conditions; settlement of the soil mass in front of the shield develops as a whole, and its settlement trough does not fit the Peck normal distribution formula; the total thrust of jacks increases sharply when the shield driving restarts as compared to normal driving. It is thought that disturbed structural clay recovers its strength during the shutdown time, and this results in a substantial increase of friction between the shield skin and soil mass.