Abstract
As the groundwater environment changes in a goaf, the creep deformation of the backfill underwater pressure is worthy of attention. This paper takes the undercut goaf filling in the Yuzhou section of the middle route of the South‐to‐North Water Transfer Project as an example. Grading loading creep testing of the backfill under different water pressures was carried out using equipment developed by our research team. Based on the experimental results, the following key points were observed: (1) under the same axial stress, the creep strain and steady creep rate increase with increasing water pressure. Under the same water pressure, the creep strain and steady creep rate also increase with increasing axial stress. (2) The long‐term strength of a backfill sample decreases with increasing water pressure and has a nonlinear relationship with water pressure. (3) The increase in water pressure exacerbates the damage of a backfill sample, which is manifested by the secondary crack propagation at the time of failure. Therefore, the increase in water pressure degrades the mechanical properties of the backfill to some extent. The results of this paper provide a reliable theoretical basis for the long‐term stability analysis of goaf filling underwater pressure.
Highlights
(2) When the stress level is lower than the yield stress, the backfill sample undergoes only attenuation creep and steady-state creep
(3) When the stress level is higher than the yield stress, the backfill sample has the characteristics of attenuation creep and steadystate creep and accelerated creep
When the axial pressure is constant, as the water pressure increases, the rate of steadystate creep increases and the time of steady-state creep stage becomes shorter, while the rate of decay creep increases but the time of decay creep stage becomes longer. is shows that the sample is damaged in the process of increasing water pressure and axial pressure, and the number of microcracks inside the sample is increasing, which leads to the increase of the rate in the creep stage and shows the phenomenon that the long-term strength of the sample decreases
Summary
E cement and coal ash were mixed according to the mixing ratio, vibrated, and poured into the mould. E entire process is computer-controlled by the test equipment, for example, via the automatic control of the water pressure, airdrying temperature, mixing time, shear rate, constant load, load measurement, axial deformation, water pressure, and sample temperature.
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