Establishment of numerical cracking constitutive models using 3D reconstruction and X-ray CT images of geomaterials

Cracking behaviors significantly affect the mechanical properties of geomaterials. Triaxial compression and Xray CT tests are implemented on Chongqing sandstone specimens to study the 3D cracking behaviors, and to obtain the stress-strain curves. A local-threshold segmentation algorithm is proposed to segment cracks, pores and solid objects in X-ray CT images. A 3D cracking damage constitutive model is established to study the strength and failure behaviors based on the defined damage ratio. Results suggest that five cracking stages are divided as follows: ((I) microflaws compaction and closure, (II) no microcrack initiation, (III) microcrack initiation and propagation, (IV) microcracks coalescence to form macrocracks , (V) the failure of specimens. The numerical stress-strain curves agree well with experimental results. This method provides excellent tools to understand the characteristics of 3D cracks, and to understand the strength and failure behaviors during the damage process of geomaterials.