The benefits of visiting the resting place of Tzaddikim:
One who prays by the gravesite of a person arouses the soul of that person in heaven to ask for mercy on one’s behalf.  The dead are made aware of what occurs below by being visited and are saddened to hear of the suffering of those alive. If not for the prayers of the dead on behalf of the alive the world would be unable to exist. The visiting of a gravesite of a Tzaddik assists one to merit to true repentance and saves him from both physical and spiritual suffering. Likewise the main Tikkun for the sin of Pegam Habris is accomplished through this.