1 A CRITERION FOR BRITTLE FAILURE OF ROCKS USING THE THEORY OF CRITICAL DISTANCES by Jorge Castro ( 1 )(*), Sergio Cicero ( 2 ) and César Sagaseta ( 3 ) Department of Ground Engineering and Materials Science University of Cantabria Avda. de Los Castros, s/n 39005 Santander, Spain Tel.: +34 942 201813 Fax: +34 942 201821 e-mail: ( 1 )castrogj@unican.es ( 2 )ciceros@unican.es ( 3 )sagasetac@unican.es (*) Corresponding Author Date: February 2015 Number of words: 6,100 Number of tables: 2 Number of figures: 18