###### Abstract  
In order to study the applicability of high-pressure gas expansion rock-cracking technology in hard rock tunnel near historic sites, theoretical analysis, field tests as well as vibration monitoring are conducted to obtain suitable rock mass cracking parameters for tunnel excavation. The results show that the ideal effect of rock mass cracking can be achieved with the cutting mode of \"central vertical empty hole + double wedge cutting hole\" and the auxiliary hole network parameter of \"0.8 m \(\times\) 0.7 m\({}^{*}\). The measured vibration velocity is less than 0.1 cm/s at the monitoring point 60 m away from the tunnel face in the field test, which meets the vibration control requirements of the historic sites in the process of tunnel excavation. The research results show that as long as there is a high quality of hole plugging and no punching, the high-pressure gas expansion rock-cracking technology has the advantages of little vibration, low noise and less flying rocks, which provides a technical reference for the excavation of hard rock tunnels near ancient buildings and historic sites. high-pressure gas expansion rock cracking; hard rock tunnel; field tests; rock-cracking parameters; vibration monitoring +
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excavation method by numerical simulation and derived the tunnel milling law, which provides a reference for the construction of the mechanical milling method. [PERSON] et al. [9] analyzed the effect of CO2 blasting through a blasting test, and studied the fracturing mechanism of CO2 blasting through numerical simulation. [PERSON] et al. [10] studied the vibration effect of CO2 blasting and obtained some attenuation laws of blasting vibration signals. Although these non-explosive blasting rock-cracking technologies overcome the problem of high vibration, they also have their own shortcomings, such as high cost, low efficiency of rock cracking, and cumbersome operation processes. Moreover, the technical problem that most limits their application is their poor rock-cracking effect on hard rock and low excavation efficiency. In recent years, high-pressure gas expansion rock-cracking technology, a new rock-cracking technology, not only inherits the advantages of non-explosive blasting rock-cracking technology with little vibration, but also can achieve safe and efficient excavation of hard rock. In the excavation of hard rock tunnel near ancient buildings and historic sites, it is important to consider the effect and efficiency of rock mass cracking and the impact of vibration on the safety of ancient buildings and historical sites. High-pressure gas expansion rock-cracking technology stands out among many rock-cracking technologies and becomes the preferred solution for similar projects. High-pressure gas expansion rock-cracking technology and CO2 blasting technology are two different kinds of rock-cracking technology that use gas expansion, but the rock-cracking mechanism of both has some commonality. So, it is necessary to understand CO2 blasting technology for in-depth studies of high-pressure gas expansion rock-cracking technology. [PERSON] et al. [11] studied the rock fracture mode of CO2 blasting by numerical simulation and presented some corresponding experimental phenomena, which enriched the theoretical studies of CO2 blasting. [PERSON] et al. [12] studied the initiation mechanism of CO2 fracturing pipe and obtained its empirical model, which can be used to optimize CO2 blasting technology. [PERSON] et al. [13] monitored the vibration of CO2 blasting and concluded that the vibration of CO2 blasting is lower than that of explosive blasting. [PERSON] et al. [14] studied the influences of different factors on the CO2 blasting effect by numerical simulations and field tests, and concluded that peak pressure plays a major role in controlling the effect of CO2 blasting.