Development and application of pneumatic hollow cylinder apparatus with four-direction dynamic loads

Only the torque can be dynamically controlled in the traditional hollow cylinder apparatus, and the dynamic shear tests can be carried out. The existing hollow cylinder apparatus is modified to have the four-direction vibration capability, including axial force, torque, internal and external pressures, to study the influences of wave loads. The composition and technical parameters of SJTU-HCA are mainly introduced. The basic formulas for the fixed principal stress axis tests and the principal stress axis cyclic rotation tests are deduced, and the instrument control programs including the automatic control algorithm are prepared. The static loading ability of the apparatus is verified by the fixed principal stress axis tests of any principal stress angle for sand. Further, the dynamic loading capacity of the apparatus is verified by the principal stress axis cyclic rotation tests for sand under the three control parameters including the defection stress q, the average principal stress p and the principal stress parameter b. The results prove that the SJTU-HCA can work with various complex stress paths. The pneumatic improvement experience may provide a reference for the future development of geotechnical apparatus.