This thesis investigates ground improvement techniques, focusing on the application of drains and the innovative capsule grouting technology (CGT) for tunnel excavation in saturated clay mediums. The excavation of an underground metro systems frequently encounters geo-materials of poor geotechnical properties, making it essential to improve the ground's strength and stiffness under certain conditions to support the excavation process. Pre-excavation drainage of clayey layers is typically considered effective. It involves drilling boreholes and activating them for a specific duration. Special attention is directed towards the innovative capsule grouting technology (CGT), which involves injecting grout into capsules (or inflating pockets) made from a special membrane to create an artificial volumetric increase, ensuring controlled grout distribution within heterogeneous ground conditions.