## 8 Conclusions  
(1) The stability of bottom structures in block caving mines is significantly challenged by impact loads generated from large rockfalls and ore collapses on slopes. This study investigated the mechanical response and failure characteristics of bottom structures under dynamic and cyclic loading conditions through a combination of discrete element method (DEM) simulations and true triaxial tests. The results provide valuable insights into the damage mechanisms and stability of bottom structures under complex loading scenarios.  
(2) The impact loads generated by slope collapses can be categorized into three types: overall impact from large-scale slope collapses, localized impact from partial rock and soil mass collapses, and continuous multiple impacts from progressive slope failures. The experimental and numerical investigations revealed that while overall and multiple impact loads from slope collapses do not lead to catastrophic failure of the bottom structure, severe damage occurs under a 100 m thickness of ore and large block impacts. Specifically, the inner walls of ore accumulation troughs peel off, and ore pillars between troughs fracture and fail.  
(3) The mechanical response of the bottom structure under different loading conditions was characterized by varying degrees of deformation and strain accumulation. The presence and thickness of the overlying soil layer significantly influenced the stress distribution and mechanical response, leading to more severe deformation and potential for damage. The results highlight the importance of considering the combined effects of static overburden  
Figure 27: Characteristics of bottom structure failure under 100 m overlying load and large impact: (**a**) the broken ore pillars between the ore gathering tanks; (**b**) cracking at the arch of the alley entrance; (**c**) pillar fracture; and (**d**) the ore tank is peeling off.  
pressure and dynamic impact forces in the design and assessment of bottom structures in block caving mines.  
(4) In the future, it is necessary to conduct experiments on the impact of blasting loads on the stability of the bottom structure. As blasting loads are high-frequency loads, Hopkinson bar technology needs to be utilized to achieve the desired experimental results.  
Software, G.L., Z.W. and H.L.; Formal analysis, X.F.; Investigation, G.L., Z.H. and H.L.; Resources, X.F., Z.W., X.Z. and H.L.; Data curation, G.L. and Z.H.; Writing--original draft, X.F., Z.W. and X.Z.; Writing--review & editing, X.F. All authors have read and agreed to the published version of the manuscript.  
This paper receives its funding from Projects (5247042340, 42277175) supported by National Natural Science Foundation of China; Project (2023 JJ30657) supported by Hunan Provincial Natural Science Foundation of China; Yunnan Province Science and Technology Plan Project (202205 AD160063); Hunan provincial key research and development Program (2022 SK2082).  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
Authors [PERSON], [PERSON] and [PERSON] were employed by the company Yunnan Diqing Non-Ferrous Metals Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.