摘要
砂卵石红砂岩复合地层上部为密实砂卵石下部为强风化红砂岩,整体呈上硬下软状。采用土压平衡盾构施工时易产生盾构姿态上下偏移,出现盾构机在砂卵石、红砂岩两类地层中往复穿越的现象,导致盾构推力、刀盘扭矩等波动大,而砂卵石、红砂岩地层条件悬殊,在掘进时需要不断更换改良剂以适应地层变化,使得渣土改良更加困难。本文依托兰州地铁2号线盾构工程,结合现场施工经验,对膨润土泥浆配比进行了重新优化,提出膨润土泥浆加泡沫剂的混合改良方案。实践表明,采用1:6配合比膨润土泥浆,4%浓度泡沫剂,泥浆掺入比10%、泡沫掺入比15%左右的混合改良剂方案能够同时适用于两种地层,通过工程试验和掘进参数分析,发现掘进时的盾构推力、刀盘扭矩等波动明显减小。
The upper part of the sand pebble-red sandstone composite stratum is hard dense sand pebble,and the lower part is soft intensely weathered red sandstone.When the earth pressure balance shield(EPBS) is used for construction,the position of the shield is prone to shift up and down.The condition that the shield machine moves up and down in the strata of sand pebble and red sandstone can cause large fluctuations in shield thrust and cutterhead torque.Since the stratum conditions of sand pebble and red sandstone are very different,the modifier needs to be replaced continuously during the excavation process,which brings difficulties to the soil improvement.Taking the shield tunneling project of Lanzhou Metro Line 2 as an example,an optimized improvement plan of bentonite mud mixing with foaming agent is proposed in this paper.The practice shows that the mixed modifier with bentonite mud of 1:6 ratio,a concentration of 4% foaming agent,mud mixing ratio of 10% and foam mixing ratio of 15% is suitable for those two strata at the same time.The field tests and driving parameter analysis show that the fluctuation of shield thrust and cutterhead torque are significantly reduced during shield driving.
作者
于开贞
李忠
Yu Kaizhen;Li Zhong(College of Urban Railway Transportation,Shanghai University of Engineering Science,201620,China)
出处
《特种结构》
2022年第4期96-101,共6页
Special Structures
关键词
土压平衡盾构
砂卵石红砂岩复合地层
渣土改良
掘进参数分析
Earth pressure balance shield(EPBS)
Sand pebble-red sandstone composite formation
Soil improvement
Driving parameter analysis
