土压盾构非满舱掘进时压缩空气与地层适应性分析

Adaptability Analysis of Compressed Air and Stratum in Non-full Chamber Excavation of Earth Pressure Shield

针对气压辅助工法应用越来越多工程实践,基于Geostudio Air/w建立的气-水-固耦合数值计算模型,探讨了不同盾构隧道顶部埋深、上覆闭气层厚度、地层性质以及盾构压力舱空舱高度对开挖面渗气量的影响。结果表明:分析广州地铁21号线某区间土压盾构气压辅助工法的应用案例,压缩空气渗气量控制在1.2 m^(3)·min^(-1)内,在开挖面建立稳定的支护压力,确保盾构掘进达到微扰动控制水平;闭气能力强的粉质黏土和黏土地层土压盾构掘进时,通过向压力舱注入少量压缩空气可以更好的保持开挖面支护压力的稳定;渗透系数较大、地质分布不均的砂卵石、上软下硬地层,难以进行满舱掘进时,可根据隧道埋深和上覆闭气层厚度来选择合适的空舱高度,确保压缩空气逃逸量小于产气量;土压盾构穿越渗透性地层,上覆闭气层厚度在10.0 m以上、或埋深大于28.0 m时,压缩空气逃逸量较少,也不易发生压缩空气逃逸冒顶。

Aiming at increasing engineering practice of compressed-air-assisted method,based on the numerical calculation model of air-water-solid coupling established by Geostudio Air/w,the influence of different shield tunnel top buried depth,thickness of overlying airtightness layer,stratum property and pressure chamber height on the seepage volume of excavation face was discussed.The results show that:The application case of compressed-air-assisted method in a section of Guangzhou Metro Line 21 is analyzed.The seepage gas volume is controlled within 1.2 m^(3)·min^(−1).A stable support pressure is established on the excavation surface to ensure that the shield tunneling reaches the microdisturbance control level.When the earth pressure shield tunneling in silty clay and clay stratum with high airtightness ability,appropriate compressed air can be injected into the pressure chamber to better maintain the stability of the support pressure of the excavation face;To ensure the seepage volume is less than the gas production.When it is difficult to carry out full-cabin excavation in sandy cobble,upper soft and lower hard stratum with large permeability coefficient and unequal geological distribution,the appropriate empty chamber height can be selected according to the buried depth and the thickness of the overlying airtightness layer.When the earth pressure shield crossing permeable stratum and the thickness of the overlying airtightness layer exceeding 10.0m,or the buried depth exceeding 28.0m,compressed air escape amount is less,and it is not easy to occer roof fall under compressed air.