Mechanical Properties of Sands Obtained from Tunnel Construction Site of Tohoku Shinkansen

Hirofumi TOYOTA

Soil's strength parameters (c,) are important in the foundation design of various structures and the stability of the ground. The strength parameters are different depending on soils, in addition, they change by the void ratio, the degree of saturation, the stress history, the shear rate and the drainage conditions. Therefore, the decision of the unique strength parameters is not easy. It is necessary that the strength parameters are obtained considering conditions of a construction site for an accurate prediction.
In this research, triaxial compression tests were conducted to examine shear properties of a sandy soil obtained from Rokunohe tunnel of Tohoku Shinkansen under construction. Dense and loose specimens were prepared by wet tamping method. The shear process was executed under constant p' and drained conditions. Moreover, the creep tests were also carried out to investigate creep behaviour at a variety of strain levels.
The obtained results in this research are shown below:
1)Although strain softening appeared in dense Rokunohe sand, large strain was needed for the softening.
2)Angles of shear resistance were about 41.4 and 32.2 degrees in dense and loose conditions, respectively. Cohesions were about 5 kPa in both conditions.
3)The value of shear modulus in dense conditions indicated about twice or more that in loose conditions at strain level of 0.01%.
4)Influence of creep was able to be ignored in Rokunohe sand because the stress-strain relation returned to that of monotonous loading after the creep behaviour.