Experimental Study On Meso-damage Development Properties Of Nanjing Red Sandstone And Its Constitutive Model

Engineering disaster of swelling rock is a subject of extreme complication and momentously economic implications. How to construct projects and sustain its stability economically and effectively in such rock is always a problem puzzling many experts in rock mechanics and engineering geology. Once swelling rock mass is disturbed especially water content changing, an evidently physical and chemical reaction is occurred in swelling rock, which seriously influences the stability of engineering.Taking disposal of swelling red sandstone groundsill of Hong Shan Yao hydrojunction as project ground in this paper, the whole stress-strain curves, macroscopic failure shapes, pictures of meso-structure development of red sandstone are achieved though uniaxial compression tests of RMT and meso-structure of red sandstone in different water content. By applying the theory of rock mechanics , damage and fracture mechanics, experimental results are analyzed and some conclusions are summarized as the following:(1) Though uniaxial compression tests of RMT, the relations of water content and compression strength, elastic module, peak strain of red sandstone are analyzed. Though uniaxial compression tests of meso- structure, the relations of macroscopic mechanics responses and micro-crack damage development of red sandstone are importantly analyzed by means of Geo-image programme.(2) From the theory of meso-damage, crack area ratio is defined as damage variable, and damage constitutive model of peak strain is deduced, further four periods of damage development are expounded: damage reducing, elasticity, nonlinear strengthening, softening. From the theory of macro-damage, intrinsic reasons of strain softening property of red sandstone are analyzed on basis of whole stress-strain curves. And damage constitutive model of post strain is deduced on basis of others achievements.(3) Through the comparison with above model and results of RMT, other models, the constitutive model of red sandstone is correct and logical. Further the model is applied in the Hong Shan Yao project, which not only has a guiding means for the design, construction, running of the project, but also enriches and develops the study of damage mechanics.