Experimental investigation on strength and deformation properties of clastic sandstone under triaxial compression

Based on the characteristics of loose organizational structure, high moisture content, poor physical mechanical properties and pore cementation contact, the basic physical properties tests on clastic sandstone were carried out first. It's considered that the rock which belongs to small porosity sandstone as micro-permeability is extremely complex microstructure and that internal structure is damage seriously. The main mineral compositions are quartz, feldspar, sericite and so on; mainly chemical constituent is SiO2 and the chemical erosion is not significant. Secondly, the hydrostatic pressure tests, uniaxial and triaxial compression tests were carried out for clastic sandstone to study the strength and deformation failure properties. Finally, the correlations between mechanical properties and physical properties are preliminary discussed. The results show that the internal micro-defect of rock is compaction completed when hydrostatic pressure reaches 2.6 MPa. The uniaxial compression curve shows the characteristics of six distinct stages; and that the peak stress is 0.98 MPa. Moreover, brittleness and ductility are shown. Under triaxial compression test, clastic rock shows significant characteristics of mainly compressed and ductility dilatancy failure. In the action of deviatoric stress, the axial and lateral strains of rock reach 6% and 4% respectively. The curve has no significant damage load, which shows the mechanical properties of nonlinear, plastic hardening, yield platform and volume strain from compression to ductility dilatancy and so on. And the volume dilatancy damage stress is almost the same as the yield stress. The dilatancy turning point increases with an increase of confining pressure, and moreover, the confining pressure enhances the rock resistance to deformation and failure. The results provide dependable reference for the establishment of rock constitutive model and stability analysis.