Geotextiles Closed Systems (GCS) has been used to dewatering a variety of high-water content sediments aiming to reduce the final volume of the residue at disposal. The geotextile retention capability and a filter-cake that does not involve an excessive reduction of the hydraulic conductivity of the system are determinant to the success of the dewatering process. In addition, the grain size distribution (GSD) of the solid phase is tightly related to this success. There are two distinguishable phases in the process: the initial phase in which geotextile permeability controls the flow rate, and the post filter-cake formation phase in which the retained sediments start to control the flow rate.  The GSD play an important role in the retention of particles with a diameter smaller than the characteristic geotextile opening size by interlocking small particles between the bigger ones retained by the geotextile. However, it is difficult to determinate how sensitive the dewatering process is to GSD variation. This work presented a discussion on how the increment in the coarse fraction of the GSD affects the filter-cake formation.  The paper will discuss the results of falling-head column test performed to evaluate the behavior of a woven geotextile in the dewatering process of a sediment with different compositions of GSD, in a turbulent flow condition at initial solids concentration of 5%. The tests also evaluated the solids concentration in the effluent and water content in retained material. The obtained results indicate that a small amount of coarse material is sufficient to initiate the filter cake formation and has a greater impact on effluent quality.