土压平衡盾构用复合式泡沫发生器及其产泡特性的研究

Research on the composite foam generator and its foaming properties for earth pressure balance shield

为了解决土压平衡盾构用泡沫发生器产泡效果差、泡沫浪费严重等问题,设计复合式泡沫发生器。通过泡沫流量、发泡倍率和析液半衰期试验,确定滚珠填充率、粒径、多孔板孔径是泡沫发生器主要影响因素,测试泡沫析液质量与时间的关系,对泡沫平均直径随时间的变化关系进行了研究。研究结果表明:玻璃滚珠粒径为4~5 mm,体积填充率为50%,多孔板板孔径为3 mm时,泡沫流量为80~133 L/min,发泡倍率为26.0~31.6,析液半衰期为758~845 s,泡沫发生器产泡量较大、发泡倍率较大、泡沫稳定性好。泡沫从产生至半衰期,泡沫携液量大,析液快,0~8 min泡沫平均直径为10μm,8 min至半衰期平均直径增加到40μm,泡沫改良渣土和排土器排土多集中在此时间段;半衰期后,析液量小、持继时间长。整个过程中,泡沫平均直径处于动态变化过程中。利用含聚合物的泡沫剂对高含石量的砂卵石地层进行改良,塑流性随泡沫掺量增加而升高,渗透系数、剪切强度和内摩擦角随泡沫掺量增加而降低。泡沫掺入量40%~50%时,塑流性和渗透系数能达到要求。

In order to solve the problems during the foaming process of foam generating system of EPB shield,such as poor foaming effect and serious waste of foam,the compound foam generator was designed.Through the experiments of the foam flow,foaming ratio and half-life of the foaming generator,the major factors affecting foaming properties were glass bead diameter,volume filling rate and aperture of porous plate.In this paper,the relationship between the quality of foam and the time was tested,and the relationship between the average diameter of foam and time was studied.The results show that when the working conditions for the foam generator were diameter of the glass ball is 4~5 mm,volume filling rate is 50%,porous plate aperture is 3 mm,foam flow is 80~133 L/min,foaming ratio is 26~31.6 and half-life is 758~845 s,the foam generator reaches the optimum state.From production to half-life,foam carrying volume is large,liquid evolution is fast,the average of diameter is 10μm in 0~8 min,it increases to 40μm from 8 min to half-life,muck improvement and dumping are mainly concentrated in this period.After half-life,foam liquid gradually lost,liquid evolution volume is small,holding time is long.The foam diameter is in dynamic process during the whole process.Foaming technology for high gravel content sandy cobble stratum is carried out with polymer containing foam agent.The permeability,shear strength and internal friction angle decrease with the increasement of foam content,on the contrary,the plasticity increase.When the amount of foam is 40%~50%,the plasticity and permeability can meet the requirements.