盾构土舱压力变化规律测试试验与理论分析

Test and theoretical analysis of change laws of earth chamber pressure

为研究刀盘开口率对盾构土舱内、外压力的影响,利用土压平衡盾构模型机,在多种不同刀盘开口率条件下进行模拟掘进试验,监测刀盘开口处土压力和土舱压力,分析不同刀盘开口率条件下的土舱内、外压力的变化规律,试验结果表明,随着刀盘开口率的增加,土舱压力传递系数逐渐增大,土舱内、外压差逐渐减小。借鉴黏性流体理论,针对盾构施工渣土运动过程中的应力变化建立力学模型,提出土压力变化公式,考虑土体运动过程中的沿程损失和刀盘结构处的局部损失,使计算过程更加贴近于实际状况,可以定量分析刀盘开口率、隧道洞径、土体参数、附加应力等参数对土舱内、外土压力变化的影响。根据该力学公式可得,土体内摩擦角和黏聚力越大,盾构土舱内、外土压力差值越大;盾构刀盘开口率越大、隧道直径越大,盾构土舱内、外土压力差值越小。为确认理论分析的合理性和适用性,将理论计算公式和实际工程的监测数据、离散元模拟结果以及模型试验结果进行了对比分析,进一步论证了计算理论的合理。

The simulating driving test of shield machines is carried out by using a model shield of earth pressure balanced type with cutterheads of different open area ratios. Through measuring the earth pressure inside and outside the chamber, the relationship between earth pressure and open area ratios of cutterheads is gotten. Based on the theory of fluid mechanics, a calculation formula of the pressure change is deduced and the quantitative analysis of the influence of aperture ratio, tunnel diameter, soil parameters, additional stress on changes of the earth chamber pressure can be performed by means of the deduced formula. According to the formula, when the angle of internal friction and cohesive increase, the difference of chamber pressure and earth pressure outside become greater. Besides, when the rate of opening on cutterdisc and diameter of shield tunnel increate, the difference of chamber pressure and earth pressure outside become smaller. Comparisons between results of theoretical calculations and the other means, such as field monitoring and discrete element simulation analysis are done, which confirms the rationality of the gotten formula.