隧道二次衬砌结构混凝土开裂会影响其长期使用性能，导致结构耐久性退化。客运专线隧道二次衬砌的细微裂缝甚至会在车辆运行作用下（振动、气动压力）扩展，影响行车安全，因此控制衬砌混凝土施工期裂缝的研究显得十分重要。现场测试采用在衬砌混凝土上预留孔的方法测定二次衬砌现浇混凝土内部的温度和湿度，得到其随时间的变化规律，同时在衬砌混凝土内埋置振弦式混凝土应变计的方法测试混凝土在施工期间的应变变化规律。测试结果表明，早期混凝土内部应变的变化规律从量值上表现为： 边墙部位的压应变态势、拱顶部位的拉应变态势及拱腰部位的过渡态势。拱顶部位在施工期表现为拉应变，这是衬砌混凝土裂缝控制的关键。

Cracks of concrete lining structures of tunnels will affect the longterm operational performance of the tunnel and will lead to the durability degradation of the tunnel structure Due to the action of the running trains (vibration and aerodynamic effect), the micro cracks on the secondary lining of tunnels on passengerdedicated railways will expand and the operation safety of the tunnels will be affected As a result, it is of great necessity to study the control of the cracks of the secondary lining The internal temperature and humidity of the lining concrete are monitored by means of reserved holes in the concrete, and the variation of the temperature and humidity with time is obtained Meanwhile, the variation of the strain of the concrete during the construction period is obtained by means of embedding vibratingwire concrete strain gauges in the concrete lining The testing results show that the internal strain of the earlyage concrete has the variation rule that compressive strain occurs to the sidewall, tension strain occurs to the crown and the haunch is the transition zone Tension strain occurs to the crown, therefore the crown is the key point to control the cracks of the concrete lining 