In order to study the time-dependent deformation behavior of bedding anisotropy greenschist of Jin-ping II Hydropower Station, uniaxial and biaxial compression creep experiments were carried out. Vertical loadings were perpendicular or parallel to bedding planes, which were graded 4 classes. Lateral loadings in biaxial experiments were equal to half vertical loadings. The data of experiments were put forward by different strain-time curves, the relationship between both instantaneous elastic modulus and steady-state creep rate and stress level was established by employing exponential function. The results show that both bedding anisotropy and lateral pressure have strong control on the development of instantaneous strain and steady-state creep strain. In biaxial creep compression experiment, bedding anisotropy had greater effect on instantaneous elastic modulus and less effect on steady-state creep rate. But in uniaxial creep compression experiment, bedding anisotropy had greater effect both on instantaneous elastic modulus and steady-state creep rate.
With the development of civil engineering such as hydraulic resources exploitation, nuclear industry engineering, railway and highway traffic engineering, and deep mining, a lot of large-scale engineering in deep rock mass continue to emerge. Take an auxiliary tunnel of Jin-ping I and II Hydropower Station as an example, such an engineering shows the characteristics such as deep buried, longer length, higher earth stress and higher water pressure. In fact, the length of the tunnel is almost 16.6km, the thickness of its overburden is from 1500 to 2000 meters, the earth stress measured in situ is 42.11MPa, the maximum value of which is approximately 70MPa and the minimum is around 26MPa, and the maximum water pressure is around 10MPa.
Compared with the engineerings in shallow rock mass, the surrounding rock of deep buried engineerings is influenced by high earth stress, high temperature and high water pressure, which are caused by the depth of overburden and give rise to the mechanical behavior variations of surrounding rock, including the viscidity of brittle rock.
The Surrounding rock of the auxiliary tunnel in Jin-ping II Hydropower Station mainly consists of marble, slate, chlorite schist and metamorphic sandstone, which belong to hard rock in the middle and upper series of the Triassic. The field monitoring data of the auxiliary traffic tunnel show that the surrounding rock has obvious rheological characteristics, bedding structure and strong inherent anisotropic properties, for which it is necessary to study further.
