盾构舱内空气损失计算及影响因素分析

为确保盾构在“气压模式”下掘进及在带压开舱作业时控制舱内气压的稳定，在分析刀盘正面土体、开挖间隙周边土体、盾尾注浆和螺旋输送机4个区域的气压损失范围基础上，改进Krabbe公式并考虑渗透系数、舱内压强、地层变化等影响因素，提出空气损失量Q的半经验半理论计算方法。将计算方法应用于实际工程，通过对空气损失量最大断面进行灵敏度分析，主要结论如下： 1）舱内压强与空气损失量呈二次正相关，工程范围内气压的增加会导致一定的空气损失； 2）空气损失量最大的断面为地层突变处，通过分析该断面的灵敏度，可以对盾构配备的空气压缩机功率进行合理的判断。

Calculation and Influencing Factors of Air Loss inShield Chamber

The stability of air pressure in shield chamber duringtunneling under "air pressure mode" and chamber opening underpressure should be guaranteed. Hence, the air pressure loose zones in 4 areasof soil in front of cutterhead, soil around the excavation gap, grouting areain shield tail and screw conveyor are analyzed, the Krabbe formula is improved,and based on which a semi empirical and semi theoretical calculation method of air loss Q is proposed by considering the permeability coefficient, earthchamber pressure and soil variation. The calculation method is applied topractical engineering, and the following conclusions are drawn by sensitivityanalysis of the cross section with the largest airloss: (1) There is a quadratic positive correlation between chamber pressureand air pressure loss, and the increase in air pressure within the scope of theproject will result in a certain volumn of air loss. (2) The cross section with the largest volumn of air loss locates in formationabrupt change area, and by carrying out sensitivity analysis on this cross section, the power of air compressor equipped on shield can bereasonably judged.