土压平衡盾构刀盘环向开口率研究

盾构刀盘开口率是指刀盘开口部分的面积与刀盘总面积的比值,是盾构选型时需要考虑的重要指标,但这一指标无法反映刀盘开口位置是否合理。为了更好地反映刀盘开口状况,提出了刀盘环向开口率的概念。运用环向开口率特征曲线对北京地铁9号线军事博物馆站—东钓鱼台站区间土压平衡盾构刀盘环向磨损事件进行了分析,阐明了刀盘发生环向磨损的主要原因是刀盘上某一区域环向开口率过小,部分渣土淤积在此区域,另外渣土从开口率小的区域向开口率大的区域流动也造成了刀盘的环向磨损。刀盘环向开口率特征曲线是判断刀盘开口位置合理性的重要依据,开口位置合理的刀盘,除刀盘中心区域外其环向开口率特征曲线应该是平缓的,以保证刀盘上每一个区域都有合理的开口区域,确保渣土顺畅进入土舱,土压平衡盾构刀盘设计时应充分考虑环向开口率这一指标。

Radial opening ratio of EPB TBM cutterheads

The opening ratio of cutterheads, the area ratio of the cutterhead openings to the entire cutterhead, is an important index for selection of earth pressure balanced (EPB) TBM. However, the opening ratio of cutterheads alone cannot fully reflect whether the positions of the cutterhead openings are reasonable or not. To solve this problem, the concept of radial opening ratio of cutterheads is proposed. Based on the characteristic curve of the radial opening ratio, the radial abrasion events of TBM cutterheads during construction of Military Museum Station to East Diaoyutai Station of Beijing Metro Line 9 are analyzed. The main reason of radial abrasion is that the radial opening ratio is too small in a certain area on the cutterhead, and part of the soil deposits in this area. Besides, it also causes the cutterhead to abrase when soil flows from the small opening ratio area to the large one. The characteristic curve of the radial opening ratio can be used to evaluate the rationality of opening position on the cutterhead. For the TBM cutterhead with reasonable opening positions, the characteristic curve of the radial opening ratio should be gentle without large fluctuations except for the central area of the cutterhead so as to ensure the reasonable opening positions in each part of the cutterhead and smooth soil moving into the chamber. The radial opening ratio should be fully considered when designing TBM cutterheads.