All soils fail at critical state, For OC soils, usually they are dilative. During drained shear, they would have a peak strength and final volume increase.
For Undrained condition e=const,V=const, u would decrease(it's possible to be suction,<0) due to increase of effective stress during shear. Usually u drops all the way. Sometimes it's possible to observe initial increment of u before decreasing, this might result from the threshold strain that for particles to roll over each other.
