## 1 Introduction  
As one of the most important fossil energy sources in the world, coal resources are widely used in industries such as chemicals, power generation, and energy [1, 2]. With the continuous increase in population and the rapid development of the global economy and technology, the demand for coal resources is also rising. However, due to environmental pollution and excessive exploitation, coal resources in shallow layers have gradually been depleted, unable to meet daily coal consumption needs. This poses a serious impact on global sustainable development and energy security [3, 4]. Therefore, the development and utilization of deep coal resources have gradually become a hot topic [4, 5]. However, unlike shallow layer environments, the unique characteristics of deep layers, such as high ground pressure, high pore pressure, and high temperature, present a series of technical challenges for the exploitation of deep coal resources [6, 7, 8]. As a critical aspect of coal mining, the construction of vertical shafts is one of the key problems that must be addressed in the extraction of deep coal resources. Drilling methods, as an effective technique for penetrating alluvial layers during coal mining [9,10], possess notable features such as high mechanization, favorable working conditions, and the ability to drill without going underground, making it a significant research direction in shaft construction [11, 12, 13]. However, with the increasing depth of coal mining, the depth of mine shafts is also continuously increasing. Traditional floating sinking methods may encounter technical challenges such as difficulty in floating due to excessive wall weight or structural failure caused by a loss of stability upon touching the bottom [14, 15, 16, 17, 18], significantly reducing the applicability of drilling methods for deep shaft construction. The construction of shafts using cast-in-situ concrete wall methods in a slurry environment--employing movable conduits and holds for directly casting concrete walls in the slurry of the drilling shaft--eliminates the need for floating and sinking, thereby effectively addressing these technical difficulties. The strength of the concrete wall is one of the primary indicators of shaft safety. If the wall strength fails to meet the support requirements, it can lead to severe structural failure and catastrophic consequences [19,20], as shown in Figure 1. Therefore, experimental research on the strength of concrete in a slurry environment provides theoretical and technical support for the use of in situ concrete wall methods in deep shaft construction. In recent years, many scholars have focused on studying the strength of shaft wall concrete. [PERSON] et al. [21] studied the effect of environmental factors on the compressive and flexural strength of corroded concrete, finding that with increasing concentrations of corrosive liquid and decreasing pH, the strength of the concrete gradually decreases. [PERSON] et al. [22] researched the strength of concrete poured in laboratory and construction site conditions, discovering that the early strength of concrete grows rapidly, and the strength growth rate of concrete poured at the construction site is higher than that in the laboratory. [PERSON] et al. [23] investigated the strength of concrete after high-temperature cooling, revealing significant differences in the impact of various cooling methods on concrete strength. When cooled after excessive temperatures, concrete may collapse due to the complete loss of strength. [PERSON] et al. [24] measured the strain of concrete using optical fiber grating during shaft wall construction, analyzing the strain variation pattern and finding that, during construction, concrete is predominantly under compression, with circumferential strain greater than vertical strain, and the strain variation stages correspond to construction phases. [PERSON] et al. [25] analyzed the concrete strength improvement factors  
Figure 1: Diagram of failure in cast-in-situ shaft walls in a slurry environment.