软弱围岩隧道开挖后自稳能力差，易发生大的变形、钢架扭曲等现象。为降低安全风险，依托郑万高铁高家坪隧道进口机械化全断面爆破施工，对支护体系下的围岩压力、钢架应力、初喷混凝土应力、锚杆轴力、围岩内部位移、掌子面挤出变形等进行系统试验研究。试验结果表明： 围岩压力、钢架应力、初喷混凝土应力受岩性条件、施工扰动等因素影响显著，随时间推移均呈现“急剧增大、缓慢增大、波动变化、稳定收敛”的变化规律； 通过锚杆轴力峰值位置可以初步判定围岩塑性区范围约为距洞壁3.0 m。基于现场试验监测，通过数值模拟分析了初期支护结构压应力、轴力和弯矩的分布情况，与现场量测数据相符，较好地反映了初期支护受力特征。本次试验的相关方法、手段和结论对隧道机械化大断面施工软弱围岩变形与支护体系受力研究具有借鉴作用，同时也为建立科学合理的支护结构体系提供了参考。

Large deformation and steel frame contortion are easily occurred due to poor stability of weak surrounding rock after excavation. Hence, a series of items of entrance section of Gaojiaping Tunnel on ZhengzhouWanzhou Highspeed Railway constructed by mechanized fullsection blasting excavation method, i.e. surrounding rock pressure, stress of steel frame, stress of shotcreting, axial force of anchor bolt, internal displacement of surrounding rock and extrusion deformation of tunnel face, are systematically studied. The results show that: (1) The surrounding rock pressure, stress of steel frame and stress of shocreting are affected significantly by lithological conditions and construction disturbance, and they show a variation law of "sharply increasing, slowly increasing, fluctuation variation and stable convergence". (2) According to the peak position of axial force of anchor bolt, the plastic zone of surrounding rock can be initially determined to be about 3.0 m away from tunnel wall. The distributions of compressive stress, axial force and bending moment of primary support structure are analyzed by numerical simulation based on field monitoring; and the analytical results coincide with the field measurement data, which can better reflect the stress characteristics of primary support. The experimental study can provide reference for mechanical study of soft rock deformation and support system of tunnel constructed by mechanized fullsection method and establishment of rational supporting structure system.