See question above. Can one visit the Kevarim of Tzadikim then? How about on Shabbos?

On Erev Shabbos the answer is that it is permitted, however on Shabbos and Yom Tov it is not. The Arizal (Shaar Hayichudim) argues that on Shabbos the Neshomos of the Tzadikim are not in contact with their earthly abode. Mishmeres Sholom (5: 29), Nitei Gavriel (Avelus 83: 2) and others permit to visit Kever Avos (burial ground of forefathers) and Tzadikim to pray for someone who is in life danger, during Shabbos or Yom Tov.