在上软下硬地层富水浅埋暗挖小断面隧洞中，因中、下台阶破岩困难，且上台阶拱脚未坐落于基岩上，初期支护未能及时封闭成环易导致上台阶初期支护发生整体下沉。针对此问题，以龙泉隧洞出口段为工程背景，通过设置开挖试验段，以破岩效率为主要指标，对比分析改装炮机破岩、液压劈裂、CO2相变致裂、膨胀剂致裂4种破岩技术的适用性，并对采用改装炮机破岩技术后隧洞的水平收敛及地表沉降规律进行分析。结果表明： 1）CO2相变致裂破岩效率约为6 m3/h，效率最高； 改装炮机次之，约为4 m3/h； 液压劈裂和膨胀剂致裂的破岩效率最低，分别为2 m3/h和1.1 m3/h。2）改装炮机破岩技术的地层适应性好、振动可控、易修边，采用改装炮机破岩后，地表沉降和拱顶沉降均大幅减小。

During construction of shallowburied tunnel with small crosssection in uppersoft and lowerhard strata with rich water, rock breaking is hard to conduct in middle and lower benches, the arch foot of the top heading is not located on the bedrock, so the primary support cannot be closed in time, which may lead to the overall settlement of the primary support of the top heading. Therefore, a case study is conducted on the exit section of the Longquan tunnel, a excavation test section is set and the rock breaking efficiency is taken as the main index to comparatively analyze the feasibilities of four rock breaking technologies, namely, refitted blasting machine, hydraulic fracturing, CO2 phase change fracturing, and expansive agent fracturing, and the laws of tunnel convergence and surface settlement after rock breaking by refitted blasting machine are further analyzed. The results show the following: (1) The rock breaking efficiency of CO2 phase change fracturing is the highest, reaching 6 m3/h, followed by that of refitted blasting machine(about 4 m3/h), and those of hydraulic fracturing and expansion agent fracturing are lower, reaching 2 m3/h and 1.1 m3/h, respectively. (2) The rock breaking technology of refitted blasting machine has many advantages such as good stratum adaptability, controllable vibration, and easy trimming, which can reduce the surface and crown settlement.