In response to the intermittent separation type water and sand inrush problem caused by the mining of weakly cemented strata in the western Jurassic coalfield, taking the water and sand inrush disaster in the New Shanghai No.1 coal mine as an example, a water and sand inrush start-up test device was used to design 25 sets of water and sand inrush start-up tests under static and dynamic water pressure conditions. Using the single factor analysis method, the influence of clay layer thickness, water head height, crack width, crack angle, and particle size on the initiation of water and sand inrush was studied. The range analysis was used to quantify the effect of each main controlling factor on the initiation of water and sand inrush.On this basis, the influence of different gas injection and pressure compensation methods on the initiation of water and sand inrush was analyzed through membership degree comparison and water and sand inrush disaster time, revealing the mechanism of water and sand inrush disaster in the process of separation and water collection. The results showed that the initial water head height and crack width are positively correlated with the initiation of water sand bursts, while the thickness of clay layers is negatively correlated with the initiation of water sand bursts. The proportion of the influence of clay layer thickness, water head height, crack width, crack angle, and particle size on the initiation of water sand bursts is 39.4%, 27.3%, 12.1%, 12.1%, and 9.1%, respectively. The order of the impact of static and dynamic water pressure on water sand burst is continuous gas injection pressure>intermittent gas injection pressure>static water pressure. The research results can provide reference and guidance for the prevention and control of water and sand inrush disasters in weakly cemented roof.