To study the deformation and fracture behavior of ultra-deep drilling core

an ultra-deep drilling core geological environment true triaxial apparatus was developed. The apparatus was mainly designed to obtain the complete stress-strain behavior

cyclic loading and unloading fracture behavior

and time-dependent deformation behavior of specimens (25 mm×25 mm×50 mm) processed by ultra-deep drilling cores under a true triaxial stress

mainly solving the technical problems such as inaccurate measurement of specimen deformation

low stiffness of the apparatus

mutual interference between pressure chamber oil pressure and actuator pressure. The device was used to test the mechanical behavior of the cores from the Xiling engineering exploration hole at the Sanshandao Gold Mine of Shandong Gold Group under the true triaxial stress. It was found that the true triaxial cyclic loading and unloading weakened the brittle fracture characteristics of the specimen

and induced deformation in three directions to show anisotropy. In the multi-stage true triaxial creep test

the deformation of specimen in three directions showed primary creep

steady creep

and accelerated creep. The creep strain rates in the three directions increased approximately linearly with deviatoric stress.