# Research on the Influence Mechanism of Foam Slurry Wall Formation
## 6 Conclusions  
This study primarily uses numerical simulations to investigate the influence of soil properties, foam slurry proportioning, and pressure gradient on the effectiveness of foam slurry wall formation. The main conclusions are as follows:  
1. The membrane formation process of foam slurry can be divided into three stages--particle infiltration, initial membrane formation, and final membrane formation. During the initial membrane formation stage, bubbles play a significant role in accelerating the formation process by clogging the pores. 2. The particle size of the soil (especially the maximum particle size, dmax) significantly affects the membrane formation. Smaller particle sizes promote mud cake formation,  
Figure 13: Flow–pressure relationship curve of foamed slurry after sand addition. while larger particle sizes increase permeability, thereby prolonging membrane formation time. An increase in porosity and gradation parameters (such as b and m) also increases the membrane formation time, but their overall impact on membrane formation is relatively small. 3. The foam slurry composition strongly influences final membrane formation quality. A swelling ratio (Rsw) of around 5% is found to be optimal. When Rsw is too low (Rsw = 2.5%) or foam concentration is too high (Cg = 30%), the slurry fails to form a stable filter cake. In contrast, a foam concentration of approximately 20%, combined with an adequate bentonite content, provides the best balance between bubble transport and effective clogging. Excessive bubble content with insufficient bentonite may lead to continued infiltration and the failure of cake formation. 4. The pressure gradient affects the membrane formation time and the depth of slurry penetration. Within a tested range up to G = 4000, membrane formation time shows a quadratic increase with pressure gradient. While a moderate increase in infiltration pressure can enhance bubble mobility and reduce formation time, excessively high pressure gradients are unfavorable for achieving a stable filter cake. Overall, the pressure gradient mainly influences the dynamics of bubble migration but has a less decisive impact on the final membrane formation outcome compared to soil and slurry parameters. In summary, soil particle size and slurry formulation are the dominant factors in determining membrane formation performance. The pressure gradient should be carefully controlled within a reasonable range to avoid undermining filter cake stability. The recommended engineering parameters for effective foam slurry wall formation are as follows: swelling ratio \(\approx\) 5%; foam concentration \(\approx\) 20%; and maximum soil particle size \(<\) 1 mm. Conceptualization: [PERSON] and L.H. ; methodology: L.H. and L.C. ; software: L.H. and X.L. ; validation: L.C., B.C. and T.L. ; formal analysis: L.H. and L.C. ; investigation: L.H. and X.L. ; resources: [PERSON] and B.C. ; data curation: [PERSON] and T.L. ; writing--original draft preparation: [PERSON]; writing--review and editing: [PERSON], L.C. and X.L. ; visualization: [PERSON] and T.L. ; supervision: [PERSON]; project administration: [PERSON] and L.C. ; funding acquisition: J.Y. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Key Research and Development Program of China, grant number 2024 YFF1700701. Not applicable. The data that support the findings of this study are available from the corresponding author upon reasonable request. Author [PERSON] was employed by the company Nanjing Zhongxing New Software Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Summary table of numerical simulation schemes.