Experimental Study on Mechanical Properties and Acoustic Emission Characteristics of Dry and Water-Saturated Soft Rocks under Different Dynamic Loadings

Studying how soft rocks behave dynamically in water-rich settings is vital for ensuring sustainable coal extraction from deep water-saturated soft rock mines. A dynamic disturbance loading system utilizing creep-impact dynamics was employed to analyze the mechanical traits and acoustic emission behaviors of both dry and fully saturated soft rock. Expanding on uniaxial compression tests as a foundational framework, additional experiments involving dynamic disturbances and acoustic emission observations were carried out on the aforementioned soft rock samples. These experiments encompassed a spectrum of cyclic disturbance amplitudes ranging from 2 kN to 10 kN. Experimental results indicated the following: (1) during dynamic disturbance, the hysteresis loop exhibits a "sparse to dense" variation. When subjected to the same number of disturbances, the hysteresis loop takes on a pointed leaf-like shape, which increases with the amplitude of the disturbances. (2) The pinnacle of intensity and the elastic modulus of the samples, when exposed to diverse amplitudes of disturbances, can be categorized into a strengthening phase and weakening phase. The reinforcement effect is highest for both samples under the effect of a perturbation of 4 amplitudes. (3) Under the action of disturbances at various amplitudes, the acoustic emission signals from the samples can be classified into four stages. In all stages, the maximum acoustic emission signals exhibited by the desiccated samples surpass those emanated from the saturated samples. In the fluctuation period (II), dry and saturated samples exhibit a cyclic strengthening effect, which becomes more pronounced as the amplitude increases. The study results offer theoretical support for understanding deformation and instability mechanisms in roadways of deep water-saturated soft rock mines, which is essential for ensuring sustainable coal resource development.