全断面富水砂层浅埋盾构隧道下穿平房群施工参数研究

盾构在富水砂层中掘进时,容易出现喷涌、地表沉降大、流砂等现象,给掘进施工带来很多问题和困难,尤其是在全断面富水砂层中掘进时,如何控制盾构施工参数显得极其重要。文章结合广州地铁21号线水西站—长平站盾构区间隧道工程实例,考虑了工程实践中盾构穿越全断面富水砂层且下穿薄弱基础的水西村民房建筑的情况,进行了盾构施工措施及试验段掘进参数分析,确定了盾构下穿水西村民房建筑的施工参数。监测结果表明:参数实际控制值与分析拟定值接近,地表沉降可以控制在5 mm内,房屋沉降可以控制在10 mm内,验证了参数选取的正确性。盾构在全断面富水砂层中下穿平房群时,实际土舱压力高于静止土压力,同步注浆量不低于1.6倍的理论值,提高土压力和推力可以有效降低平房群的沉降值。

Study on the Construction Parameters of Shallow Buried Shield Tunnels under Bungalows in Water-rich Sand Stratum

Blow-out,large ground surface settlement,quick sand and so on are encountered during shield construc tion in water-rich sand stratum,which will bring many problems and difficulties.It is extremely important to control the parameters of shield construction in water-rich sand stratum.Based on the practice of a running tunnel between Shuixi station and Changping station of Guangzhou metro line 21,an analysis on shield construction measures and parameters of the test section is conducted in light of the shield construction passing through water-rich sand stra tum and underneath the bungalows with poor foundation in Shuixi village,and the parameters of shield construction are determined thereof.The monitoring results show that:the actual control values are close to the fitting values of analysis,the settlements of ground surface and building can be controlled within 5 mm and 10 mm respectively,and the correctness of the selected parameters is verified.The actual pressure in earth chamber is higher than the static earth pressure,the amount of simultaneous grouting shouldn′t be less than 1.6 times of the theoretical value,in creasing of earth pressure and thrust can effectively reduce settlement.