## 1 Introduction  
With increasing pressure on surface transportation, urban rail transit has developed rapidly in recent years. As a core tunneling method, shield construction involves complex cross-process operations and poses high risks, particularly during the launching and reception stages. These stages are prone to accidents due to intensive ground disturbances and challenging working conditions. Statistics show that approximately 70% of accidents during shield construction occur at tunnel faces [1,2], especially in soft ground where excessive surface settlement and surrounding rock instability are more likely. Therefore, studying reinforcement technologies and deformation mechanisms for shield launching in muddy soil layer is of significant theoretical and practical value.  
Regarding reinforcement techniques for shield launching sections, [PERSON] et al. [3] summarized commonly used methods and their suitability for various ground conditions, based on soil equilibrium theory. [PERSON] [4], using the second phase of the Zhengzhou Metro suburban railway project as an example, explored the application of high-pressure jet grouting in clayey ground, analyzing the reinforcement mechanism and the construction process. [PERSON] et al. [5] determined the lateral reinforcement range using [PERSON]'s rock pressure theory and FLAC3D, identifying the optimal range by balancing economic and stability factors. [PERSON] et al. [6] studied the impact of shield tunneling in thick soft ground via numerical simulation and discussed optimal reinforcement dimensions. [PERSON] [7] and [PERSON] [8] simulated ground conditions post-reinforcement to analyze settlement and stress distribution, offering guidance for practical applications. While reinforcement technologies for tunnel faces have matured, most studies target clay or soft ground. [PERSON]. [9], [PERSON]. [10], and [PERSON]. [11] obtained the influence of different reinforcement methods on surface settlement through different numerical simulation software. This indicates that shield tunnel face reinforcement technology is becoming increasingly mature. However, existing research has mainly focused on clay and deep soft soil conditions. Therefore, studying face reinforcement techniques for shield tunnels in shallow silt layers is of significant engineering and practical value.  
Weak ground construction is highly susceptible to significant surface settlement, collapse, and subsidence. [PERSON] [12], aiming to analyze settlement behavior, proposed the Peck surface settlement curve based on field measurements and theoretical models. [PERSON] et al. [13], using PLAXIS 3D to simulate tunneling in soft soil, found significant post-construction settlement, suggesting pre-reinforcement measures. [PERSON] [14], addressing deformation in shallow-buried silty strata through simulation and field data in the Pearl River Delta, found greater uplift near the tunnel face, with segment uplift initially increasing and then decreasing. [PERSON] et al. [15] evaluated construction schemes for minimizing side slope disturbance, concluding that the hidden-arch method suits shallow silty ground entry zones. [PERSON]. [16], [PERSON]. [17], and [PERSON]. [18] studied the influence of shallow buried and soft soil tunnel construction on ground settlement by using test and numerical simulation software.  
Despite many studies on shield tunneling in soft, shallow grounds, few focus on controlling post-reinforcement settlement in muddy soil layer. This study, based on the launching section of the Guanggang New City depot access tunnel on Guangzhou Metro Line 10, uses numerical simulations to compare two reinforcement schemes. Combined with field monitoring and theoretical analysis, the study explores the effectiveness of these methods and examines the deformation behavior during tunneling. The findings aim to provide theoretical guidance and practical references for shallow-buried soft ground shield tunnel face reinforcement and construction.