Abstract : Experimental investigations are carried out in order to characterize behavior of fault gouges. We use a cylindrical shear apparatus with a thick synthetic fault gouge sheared over plurimetric slip distance. The progressive slip-weakening of apparent friction is modeled by a new power law which takes into account confinement level without any notable effect of water. Shear stress release imposed by slip perturbation induces a systematic healing at reloading when the perturbation is greater than a certain threshold. This healing should be related to the prevented dilation of the shear band of localized deformation. Moreover, sinusoidal or steps variation of confinement induces proportional volumetric strain and shear variation. The sinusoidal confinement perturbation takes place without time lag and any resonance phenomena. The effect of variation period is observed at small values (< 20 s). Furthermore, the confinement variation has little influence on a sample already submitted to a confinement level greater than that covered by the variation. Interestingly, measurement during slip of hydraulic conductivity of the shear band shows a large reduction related to fine particles produced by grains crushing. Thanks to a new device, normal stress estimation at rough interface indicates comparable behavior to previous studies on smooth interface. An exception appears for large slip weakening phases.The general behavior of experiments seems to depend particularly on the interaction between the shear band and the surrounding soil.