Research on the Mechanical Behavior and Damage Constitutive Model of Fractured Sandstone Constrained by CFRP

Abstract Aiming at the engineering problem of the coordinated deformation and failure of the advanced support structure of deep roadways and the overburden fissured rock mass, taking the transportation roadway of the 40101 mining face of Gaojialiang Coal Mine in Ordos as the engineering background, a flexible support structure formed by the simulation of surrounding rock and advanced support using carbon fiber reinforced composite material (CFRP) is adopted. The mechanical response, failure mode and energy damage evolution mechanism of fissured sandstone under different CFRP constrained areas and fissure angles are studied through a uniaxial compression test. The results show that as the constrained areas of CFRP gradually increases, the peak strength, elastic modulus and peak strain of fissured sandstone gradually increase, the Poisson's ratio gradually decreases, the failure mode gradually changes from brittle split failure to ductile shear failure, the energy storage capacity increases, the critical threshold for the conversion from elastic energy to dissipated energy gradually moves backward, and the initial stress level of damage significantly increases. The mechanical parameters exhibit significant anisotropy with the fissure angle. The peak strength, elastic modulus and peak strain all show an asymmetric "V" shaped evolution pattern with the fissure angle, with the minimum values all located at θ = 45°, and the Poisson's ratio monotonically increases with the fissure angle. Based on fracture mechanics and statistical damage theory, the CFRP constraint coefficient β was introduced to modify the stress intensity factor K Ⅰ at the fissure tip. A damage constitutive model of sandstone with prefabricated fissures considering the modification of CFRP constraints was established. The accuracy and rationality of the model were verified in combination with the test results. The research results provide a reliable theoretical basis for the collaborative design of fissure surrounding rock and advanced support in deep roadways.