Design and validation of a new temperature-controlled large-scale direct shear apparatus

To mitigate the size effect on the shear mechanical properties of geotechnical materials and address the limitations of conventional direct shear apparatus, we have designed a new temperature-controlled large-scale direct shear apparatus (TXTZJ-500) based on the existing ones. The innovative apparatus can be used to test the direct shear mechanical behaviors of different materials under freezing or high temperatures. By increasing the size of the shear box, this new direct shear apparatus significantly minimizes the impact of the size effect on the sample failure surface. Consequently, it represents the stress state and provides precise shear mechanical properties of the sample accurately. Subsequently, we conducted a series of direct shear tests on sandy soil and graded gravel materials at different temperatures and axial stress levels using the TXTZJ-500 apparatus. The obtained test results indicate that the TXTZJ-500 effectively replicates the strength and deformation characteristics of sandy soil, frozen soil, and graded gravel. The test data of the developed apparatus are stable and reliable, and can provide a test reference for assessing the mechanical properties of geotechnical materials. •A new temperature-controlled large-scale direct shear apparatus was developed and introduced.•The mechanical properties of a coarse sand were studied by the developed direct shear apparatus.•The mechanical properties of graded gravel with different gradations were investigated.