一种区分欠固结软土地区盾构施工地表沉降组成的实用方法

Practical Method to Judge the Ground Settlement Caused by Shield Tunnelling in Unconsolidated Soft Soil

在欠固结软土地区中,监测所得盾构掘进引起的地表沉降相对于真实值往往偏大,导致掘进对地层的影响被高估。欠固结软土地区盾构掘进对地层扰动规律目前缺乏研究,为找到能更精确评估掘进影响的方法,文章结合实际广州某大盾构项目的地表沉降实测数据分析欠固结地层中盾构掘进引起的地表沉降规律。分析实测数据后得出以下结论,在欠固结软土地区盾构施工中,地表沉降应由盾构施工引起的沉降和地层欠固结引起的沉降两个部分组成,两个部分沉降的速率存在明显差异,利用盾构施工引起的沉降呈现槽形分布且先完成的特点,提出了“增量沉降速率槽”方法,从总沉降中有效分离出盾构施工引起的沉降和地层欠固结引起的沉降两部分。研究有助于更加准确地评价和确定盾构掘进在欠固结地层引起真实位移。

In underconsolidated soft soil areas,the surface settlement caused by shield tunnelling obtained by monitoring is frequently larger than the true value,resulting in an overestimation of the impact of tunnelling on the strata.There is currently a lack of research on the law of stratum disturbance caused by shield tunnelling in underconsolidated soft soil areas.In order to find a method that can more accu‐rately evaluate the impact of tunnelling,analyzes the law of surface settlement caused by shield tunnelling in underconsolidated strata based on the measured surface settlement data of a large shield project in Guangzhou.After analyzing the measured data,the following conclusions were drawn:in shield construction in underconsolidated soft soil areas,the surface settlement should be composed of two parts:settlement caused by shield construction and settlement caused by underconsolidation of the strata.There is a significant difference in the settlement rates of the two parts.Taking advantage of the fact that the settlement caused by shield construction presents a trough-shaped distribution and is completed first,the"incremental settlement rate trough"method is proposed to effectively separate the settlement caused by shield construc‐tion and settlement caused by underconsolidation of the strata from the total settlement.The study helps to more accurately evaluate and de‐termine the true displacement caused by shield tunnelling in underconsolidated strata.