## 1 Introduction  
Floor water intrush refers to a type of mine hazard during which large volumes of groundwater from underling aquifers break through a geological barrier (i.e., key strata) and burst uncontrollably into the excavation space in a sudden, delayed or lagged form [1, 2, 3, 4, 5]. Moreover, these catastrophic events with high-frequency growth have comprised a major safety challenge for deep underground engineering projects in northern China [6, 7, 8]. As shown in Figure 1, recent statistics have shown a rising cumulative death toll, with approximately 4018 deaths recorded from 2000 to 2021 in China [9, 10, 11, 12]. However, there are some new problems with the increase in mining depth in recent years. More evidence has demonstrated that strata failure resulting from mining activities significantly increases the risk of water outburst [13, 14, 15, 16, 17] and may threaten the safety and efficiency of coal production. Therefore, accurately evaluating the failure range and stability of the mining floor above pressurized aquifers has attracted more attention from numerous mine operators and researchers.  
Many models and validation methods have been proposed to identify the deformation and failure characteristics of floor rocks. These approaches have been widely applied and developed in engineering practice for several decades [18; 19; 20; 21]. [PERSON] et al. [22] and [PERSON] et al. [23] used analytical models under mechanical loads to analyze the stress distribution of the mine floor after coal extraction, and further theoretically calculated the damage range based on the Mohr-Coulomb criterion. [PERSON] [24] originally put forward the slipping-line theorem to evaluate the theoretical depth of the damage area in the post-mining horizontal floor. Further studies have shown that the excavation-induced fractures of rock mass typically involve strata pressure as well as hydraulic pressure [25; 26; 27; 28]. However, few theoretical models have been reported for explaining the failure characteristics of floor strata during the process of mining above the aquifer. Numerous investigations have been carried out to improve the understanding of fracturing behavior in rocks under hydro-mechanical conditions. Among them, [PERSON] et al. [7], [PERSON] et al. [29] and [PERSON] et al. [30] adopted a coupled flow-stress-damage modeling approach for heterogeneous rocks, thereby successfully simulating the progressive development of fractures in a stressed floor. [PERSON] et al. [31] represented the entire process of the formation of inrush pathway associated with mining using a physical analog. To evaluate floor water bursting, [PERSON] et al. [32; 33] innovatively proposed a vulnerability index approach by correlating a geographic information system (GIS) and the analytic hierarchy process (AHP). [PERSON] et al. [34], [PERSON] et al. [35] and [PERSON] et al. [36] successively developed various methods based on the conventional water in-rush coefficient to assess the safety of practical production in coalmines. [PERSON] et al. [37] and [PERSON] et al. [38] used the random forest (RF) model and fuzzy comprehensive evaluation for the quantitative grading of the factors controlling floor water intrusion. Although these improved models have contributed to the scientific understanding of the mechanism of groundwater outburst in underground engineering, knowledge is still lacking in terms of comparatively analyzing the failure characteristics and stability of seam floors with varying dips.  
Therefore, this paper proposed mechanical models to comparatively analyze the failure ranges and water-inrush risk of horizontal and inclined floor strata considering the effects of excavation-induced and hydraulic pressures. These models were confirmed by numerically simulating the failure patterns of mine floors above a confined aquifer. The comparative results could provide a scientific basis for effective floor grouting to prevent mine inrush hazards.  
Figure 1: Water-related mining accidents in China from 2000 to 2021.