Author(s): Hiroyuki YAMAZAKI, Kenichi MAEDA, Kunio TAKAHASHI, Kouki ZEN, Kentarou HAYASHI
A counter-measure against liquefaction using solution type grouts was developed for foundation soils beneath existing structures. Laboratory tests and a field experiment were conducted, and the effectiveness of the grouting was validated on the counter-measure against liquefaction. The laboratory tests showed the following results. (1)The shear modulus of the improved soil obtained by the cyclic triaxial test was almost same as that of the original one. (2)The liquefaction strength of the improved soil became much higher than that of the original one. The state of liquefaction of the improved one was different from that of the original one, and was similar to the state of clay degraded by cyclic loading. The field experiment showed the following results. (3)Improved bodies were not spherical but elliptical due to the anisotropy of the permeability of ground. (4)The distribution of the unconfined compressive strength in the improved body was not homogeneous but high near the grouting point. The improved body was, however, more homogeneous and larger (4m in diameter) compared with conventional grouting methods, because some new grouting techniques were used. (5)Cyclic triaxial tests were performed on undisturbed samples taken from the improved body to investigate the liquefaction strength. The liquefaction strength of the improved soil was two times larger than that of unimproved one.