Site investigations on the decay characteristics of the soil shear modulus have so far been very limited. Meanwhile

for the laboratory experiments

which may need sampling

transportation and other procedures

soil samples are normally disturbed to some extent. However

accurate descriptions of the soil modulus are important for the site evaluations as well as the structure designs. Therefore

a series of self-boring pressuremeter based in-situ tests with a maximum depth of 33m has been carried out in the lacustrine clay of Taihu tunnel area

China. Total stress-strain curves of the different soils were obtained

and on basis of that

the shear modulus decay characteristics of the soils were analyzed in detail. Shear modulus distribution along the depth was discussed under different shear strains

where a common conclusion could be obtained for different soils is that strong degradation characteristics are shown for the small strains

and then would become stable gradually as the strain increases. A correlation law between shear modulus as well as its decay characteristics and plasticity index was established. Results show that the plasticity index can be used as a reliable index to evaluate the shear modulus decay characteristics of soils.