## 1 Introduction  
The development and utilization of underground space represents a significant area of focus within the broader field of civil engineering, encompassing a diverse range of construction projects, including tunnels, pipelines, shafts, and underground stations. These projects typically entail the breaking and excavation of earth or rock, with one of the most prevalent methods being drill-and-blast [1, 2, 3]. In comparison to mechanical excavation techniques such as shields and TBMs, the drill-and-blast method is relatively inexpensive, straightforward to operate, and has a wide range of applications. However, the traditional blasting method has an excavation footage of approximately 1.5 to 1.8 m in a single cycle,which is inefficient and requires a lengthy period of time for a single operation [4]. Although drilling and blasting remains a favored approach for cost reduction or in response to terrain constraints, the development of innovative and efficient blasting methods and technologies is an inevitable trend for subsequent advancement, with the aim of improving excavation efficiency. The process of an opening cut in tunnel blasting is of paramount importance in single-free-face blasting, and the slot cavity produced by the explosion has a significant impact on the quality of rock breakage in subsequent detonation holes [5]. The most common cutting methods can be divided into three categories: straight-hole cutting, oblique-hole cutting, and combined cutting [6; 7]. Among these methods, oblique cutting is an effective means of producing an effective free surface and a good rock-throwing effect, but the depth of the hole is limited by the width of the section due to the existence of inclination angles. In small cross-section tunnels with an area of \(<\)10 m\({}^{2}\), the use of oblique-hole cutting can achieve a superior rock-breaking effect, but due to the limited footage per cycle in small cross-section tunnels, which typically does not exceed 70% of the tunnel span [8], and the utilization rate of the blasting holes in engineering practice, which is only 80% to 90% or even lower [9], the footage of oblique-hole cutting often fails to meet the project's progress requirements. The depth of straight-hole cutting is not limited by the width of the section, and the rock-throwing distance is relatively short, but the construction technology requirements are high, the slot cavity produced by blasting is small, the explosive unit consumption is considerable, and poor geological conditions are conducive to the formation of hanging mouths and incomplete rock crushing. It is therefore of great significance to enhance the rock-breaking efficiency of cutting holes and to optimize the utilization rate of blast holes for blasting construction. In recent decades, in view of the above problems, scholars have investigated the rock-breaking mechanism of cut blasting and proposed a range of improved cut blasting methods. [PERSON] [10] conducted a comparative and analytical study of the various techniques employed for cutting holes and concluded that in soft rock (Class IV) with a borehole depth of less than 2.5 m, oblique-hole cutting is the most efficient method; conversely, with an increase in the strength of the rock and the depth of the borehole, the effect of straight-hole cutting becomes more pronounced. [PERSON] et al. [11] conducted a statistical regression analysis on the parameters of straight-hole cutting and oblique-hole cutting based on a database of tunnel blasting schemes, and investigated the correlation curves between the tunnel section, specific boreholes and the specific explosive consumption, and proposed a method to quantify and classify the difficulty of tunnelling. [PERSON] et al.