## 1 Introduction  
In today's world, the efficient development and utilization of resources serve as a crucial driving force for national economic development [1, 2]. The wire-line core drilling technology is currently the most widely used core drilling technique in mining engineering, often employing a clamp-type spring to grip the core. When drilling in intact formations, this method can ensure a core recovery rate of approximately 95% [3, 4, 5]. However, when drilling in loose and broken formations, due to poor formation cementation and severe fragmentation, the spring is unable to effectively grip the core. As a result, the core can become dislodged during the hoisting process, leading to a low core recovery rate or even empty runs, significantly affecting the core quality and drilling efficiency in loose and broken formations [6, 7, 8, 9]. To address the challenges of core recovery in wire-line core drilling processes for loose and broken strata, [PERSON] [10] developed a hydraulic pressure-assisted double core claw core drilling tool. At the end of drilling, a steel ball is dropped into the drill pipe to create pressure inside the tool, compressing the pressure-assisted core claws to close and cut the core. [PERSON] [11] developed the GW series fully adaptable formation core drilling tool, which also uses a steel ball to create pressure, causing the pressure-assisted core claws to close and complete the core cutting. [PERSON] [12] designed a hydraulic wire-line core drilling tool that employs a steel ball to create pressure for core cutting, sealing the flushing fluid flow path to achieve pressure buildup, and compressing the core claws to close and complete the core cutting. However, this method requires a specialized fishing tool. [PERSON] [13] and colleagues addressed the low core recovery rate issue in complex formation drilling by designing a bag-type double-tube core drilling tool, which significantly improved the core recovery rate and largely preserved the authenticity and integrity of the core samples. [PERSON] [14] designed an active piston suction core drilling tool that effectively reduced the resistance for the core entering the core barrel, ensuring the originality of the core samples. The aforementioned studies primarily rely on complex mechanical pressurization methods or utilize the technique of dropping steel balls into the drill pipe to create pressure for core cutting, which results in cumbersome processes and low efficiency. Additionally, these methods tend to overlook the erosive effect of the flushing fluid on the core, which can negatively impact the core recovery rate. The flushing fluid, while intended to clean the borehole and cool the drill bit, can also cause core sample erosion, particularly in loose and broken formations, leading to further degradation of core quality and reduced recovery rates. Therefore, there is a need for more efficient core cutting mechanisms that also account for the detrimental effects of flushing fluid on the core during the drilling process.  
To address the aforementioned issues, this paper employs finite element analysis and fluid simulation to develop a hydraulic closed core cutting mechanism and a water-blocking protective core bit specifically for wire-line core drilling in loose and broken strata. The system controls the flow rate of the flushing fluid to perform core cutting while significantly reducing the erosive effect of the flushing fluid on the core. First, laboratory experiments are conducted to verify that the system can successfully complete the core cutting task. Subsequently, field tests are performed to validate the high core protection and integrity rate achieved by this method. This integrated approach ensures not only efficient core acquisition but also preserves the integrity and authenticity of the core samples, crucial for accurate geological and mineralogical analysis.