Experimental Study on Confined Swelling Characteristic of Redbed Mudstone in Chongqing

In this paper,by means of confined free swelling test and confined swelling test under loads,redbed mudstone of Shaximiao group in the Middle Jurassic in Chongqing area is present to study its swelling characteristics under confined free and loading conditions,and swelling under different water injections as well.Results reveal that three phases are present in the confined free swelling of mudstone,fast swelling deformation and high swelling increasment in the first phase and increasing swelling velocity in the second phase.95 percent swelling occurs in the former two phases.It is found that vertical loads greatly restrain the confined swelling of mudstone.The confined loading swelling ratios decrease sharply with the increasing vertical loads.Moreover,the amount of water has no obvious effect on swelling characteristic of red bed mudstone within a short time under confined without load,but it plays a controlling role on the stable swelling capacities,swelling processes and characteristics as time lapsing.