Classification and verification of direct shear and strength-test apparatus for multi-scale rock mass discontinuity

Different scale effects on shear strength of rock mass discontinuity need to be tested by a special direct-shear apparatus to get stable mechanical shear strength parameters.To ensure the reliability of test data,the precision of apparatus should reach 1% when the load is range from 2kN to 1 000 kN.Due to the limitations of existing technical for testing system,the loads can not all be tested in a same apparatus.For this reason,a new integrative direct-shear apparatus was developed by three level direct-shear devices based on load classification method.Each level of device had overlapped load zones to ensure the continuity of test results.The precision and load range of this integrative direct-shear apparatus had been tested and met the testing requirement of the multi-scale specimen.The integrative direct-shear apparatus has provided a platform to research shear strength of multi-scale rock masses.