Creep characteristics and long-term strength of underground water reservoirs ' coal pillar dam specimens under different osmotic pressures

Overlying rock pressure and stored water seepage notably affect coal pillar dam creep and long-term strength in underground water reservoirs. However, the current understanding of the seepage-creep coupling effects on coal pillar dam behavior is unclear, necessitating targeted research. Therefore, This Paper conducted experiments on coal pillar dam samples under various osmotic pressures to study their creep behavior and long-term strength. The results indicate that seepage fluids, with their softening, dissolving, lubricating, and flow carrier effects, significantly notably promote the creep behavior of coal samples. Viscoelastic creep in coal decreases with increasing osmotic pressure, whereas the viscoplastic creep strain increases with increasing time and stress. This Paper proposes employing the critical stress at the steady state viscoplastic creep rate threshold as the long-term strength of coal. These findings indicate an inverse link between long-term strength and osmotic pressure, with osmotic pressure going from 0 to 6 MPa, strength drops from 23.2 to 8.5 MPa. Therefore, when designing and ensuring the long-term stability of coal pillar dams, it is crucial to consider the impact of stored water seepage.