# A Novel Carbon Fiber Composite Material for the Simulation of Damage Evolution in Thick Aquifers
## 1 Introduction  
Similar material simulation experiments are one of the primary methods for studying the movement and failure of overburden due to mining and for controlling rock layers [1, 2, 3]. Underground mine face pressure monitoring can only passively and indirectly observe the process of rock layer failure and movement, and the pressure manifestation formed at the face [4]. This approach struggles to effectively study the microscopic processes of damage, crack development, and expansion within the mining-induced rock layers [5]. Consequently, numerous scholars domestically and internationally are dedicated to developing more sophisticated boundary conditions and multi-dimensional joint monitoring techniques in similar simulation equipment. They aim to deeply analyze and uncover the micromechanical behavior characteristics of rock layer damage, crack propagation, and fracture patterns, to more intuitively and reliably reproduce and understand these mechanical processes [6; 7; 8]. The design and modification of similar material simulation platforms is an important approach for scholars conducting technical research. In the field of platform development, in addition to experimental platforms simulating conditions of thin bedrock or hard roof strata [9], large-scale stope model testing platforms and corresponding hydraulic support simulation devices have also been introduced [10], enriching the fundamental tools for experimental research. Meanwhile, multi-functional three-dimensional physical simulation [11] platforms and two-dimensional similar material simulation platforms, approaching the issue from different dimensional perspectives, have effectively expanded the depth and breadth of research, driving technical studies toward more refined and comprehensive development. Moreover, in response to special conditions such as steeply inclined working faces, the invention of novel parallelogram-type hydraulic supports and the application of new three-dimensional loadable model testing systems [12] have not only optimized structural design but also provided new methods for verifying mining behaviors, further advancing the innovation and progress of similar material simulation technologies. In terms of experimental monitoring, numerous studies have explored similar material simulation results using various monitoring techniques, including fiber Bragg grating stress sensors [13; 14], 3D ultra-high-definition borehole video systems [15], XTDIC systems [16], graphical processing software [17], microseismic monitoring [18], and resistance strain gauges [19]. These technologies and devices are employed to monitor stress variations, rock layer movement, fracture development, and strain field distribution. However, a review of existing studies reveals that current similar material simulation experiments mainly focus on the improvement and innovation of external monitoring equipment, with limited attention given to the physical and chemical modifications of the simulation materials themselves. There is still a lack of development in materials with damage and fracture self-sensing capabilities, as well as the corresponding monitoring methods. In recent years, researchers in structural monitoring have actively pursued innovative exploration. By incorporating carbon fibers into cement-based materials, they have successfully developed composite materials with self-sensing health capabilities [20; 21; 22], opening new pathways for structural health monitoring. When carbon fibers are uniformly mixed with cement-based materials, they form a complex and orderly conductive network [23; 24]. Establishing this network significantly reduces the electrical resistivity of the composite material [25], laying the foundation for it to exhibit a range of excellent properties [26]. Studies show that carbon fiber composites not only possess excellent piezoresistive properties [27; 28] but are also highly sensitive to the development and propagation of internal cracks [29; 30].