Mine roof bolt assembly

A mine roof bolt assembly for installation in a mine having a roof with a bore drilled therein;

• said bolt assembly comprising:
• a bolt shaft for insertion into a bore through the roof of a mining tunnel, the bolt shaft having a diameter Dshaft;
• a bolt head connected to a lower end of the shaft and having a diameter Dhead greater than the diameter Dshaft of the shaft;
• a flange extending radially outward from the bolt head and having an upper side forming a bolt ledge, the bolt ledge having a diameter Dledge that is greater than the diameter Dhead of the bolt head;
• a bearing plate including an axial aperture through which the shaft extends, the plate having an upper roof-contacting face and a lower washer-contacting face;
• a separate washer which is not interconnected with the bearing plate, the washer including an axial opening through which the shaft extends, the washer being situated between the bolt ledge and the lower washer-contacting face of the bearing plate;
• wherein said washer comprises:
• an elbow engaging the bolt ledge inboard from its diameter Dledge;
• a radially inner portion extending upward from the elbow and surrounding the axial opening;
• and
• a radially outer portion sloping upward from the elbow and contacting the lower face of the bearing plate.