To prevent the collapse and settlement of fine granular soil during earth pressure balance (EPB) tunneling or tunneling balance machine (TBM) operations, foaming agent mixing is one of the most efficient techniques. This work focuses on the stability of loose sandy-clay soil conditioned with the foaming agent. Four reconstituted loose sandy-clay soils were conditioned with the foaming agent CLB F5/AC. Using optical observation, Turbiscan analysis, and foam volume determination, the stability of foam mixed with fine soils was studied based on drainage coalescence and coarsening phenomena that occurred over time. Additionally, foam stability under gravity drainage was analyzed through a (one-dimensional) 1D column experiment. Variation in the FIR (foam injection ratio) shows that there is a limit FIR value from which the foam begins to be observed in the soil sample, involving a discontinuous porosity increase to the detriment of the continuous porosity decrease. An approach that considered this discontinuous porosity generated by the inclusion of gas bubbles was used to describe foam bubble degradation. Tests carried out on foam alone showed its rapid degradation compared with that of the foam added and mixed in the soil. Fine particles of clay allow foam stability even in the soil mixture. The foam volume in the soil decreases according to constant volume stages separated by a fast volume decrease. Both drainage and coalescence phenomena have occurred significantly for high values of FIRs. From the 1D column experience, foam bubbles modify the drainage kinetics by accelerating the drainage velocity compared with that of unconditioned soil. The foam behavior evolution over time when mixed with the soil can be analyzed using the same theory of the behavior of the foam alone.

中文翻译：

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松散黏土的泡沫物理稳定性：条件土壤中的孔隙度作用

为防止在土压平衡（EPB）隧道或隧道平衡机（TBM）操作期间细粒土壤的塌陷和沉降，发泡剂混合是最有效的技术之一。这项工作的重点是用发泡剂处理的松散砂土的稳定性。用发泡剂CLB F5 / AC对四种再生的疏松的沙质土壤进行处理。利用光学观察，Turbiscan分析和泡沫体积测定，基于随时间推移发生的排水聚结和变粗现象，研究了与细土混合的泡沫的稳定性。此外，通过（一维）一维柱实验分析了重力排水下的泡沫稳定性。FIR（泡沫注入比率）的变化表明存在一个有限的FIR值，从该极限FIR值开始可以在土壤样品中观察到泡沫，涉及不连续的孔隙率增加，从而不利于连续的孔隙率下降。考虑到由于包含气泡而产生的这种不连续孔隙的方法被用来描述泡沫的降解。与在土壤中添加和混合的泡沫相比，仅对泡沫进行的测试显示其迅速降解。细颗粒的粘土即使在土壤混合物中也能使泡沫稳定。土壤中的泡沫体积根据恒定的体积阶段而减少，并以快速的体积减少分开。对于较高的FIR值，明显发生了排水和聚结现象。从一维专栏的经验来看，与未处理的土壤相比，泡沫气泡通过加快排水速度来改变排水动力学。可以使用与泡沫单独行为相同的理论来分析与土壤混合时泡沫行为随时间的演变。