<p>Calcareous sand has been widely utilized as the primary hydraulic filling material in offshore engineering projects. A thorough understanding of its mechanical properties is crucial for ensuring the long-term stability of offshore structures. Calcareous sand foundations are prone to excessive deformation and particle crushing due to their inherently fragile characteristics. Geotextile reinforcement has gained attention as an effective method for enhancing the overall strength and stability of geo-structure in marine environments. This study examines the influence of geotextile arrangement type on the mechanical behavior of calcareous sand through a series of drained triaxial shear tests. The experimental results demonstrate that the incorporation of geotextile layers significantly enhances the mechanical performance of calcareous sand specimens. An increasing number of geotextile layers leads to improvement of peak shear strength and delays the axial strain corresponding to the failure state, while reducing post-peak strength degradation tendency. Furthermore, both the apparent cohesion and friction angle of the calcareous sand increase with the geotextile layers. The addition of geotextile layers effectively suppresses dilation behavior and significantly constrains lateral deformation, resulting in a transition in the failure mode from shear band formation to bulging between adjacent geotextile layers. The presence and number of geotextile layers has a significant influence on the mechanical properties of geotextile-reinforced calcareous sand at the critical state.</p>