滇中引水工程隧洞衬砌施工期温控措施

Temperature Control Measures during Construction Period for theTunnel Lining of Central Yunnan Water Diversion Project

隧洞衬砌混凝土属于典型的薄壁大体积混凝土,衬砌采用泵送混凝土、水化温升高,围岩约束大,衬砌易产生温度裂缝。为探究合理的隧洞衬砌施工期温控措施,采用三维有限元软件,考虑围岩和衬砌接触,开展了滇中引水工程某隧洞混凝土典型衬砌段施工期的温度场和温度应力场分布规律分析。结合现场监测数据,反馈分析了衬砌段表面保温系数为16.7 kJ/(m 2·h·℃)。研究了不同的浇筑温度、浇筑段长度、浇筑季节、混凝土自生体积变形特性对混凝土衬砌温度应力场的影响。结果显示:浇筑温度越高温度应力越大,浇筑温度每升高4℃,最小抗裂安全度降低0.30;高温季节浇筑最大应力较大,甚至>3.5 MPa;衬砌结构应采用合适的分段长度;采用微膨胀混凝土有利于抗裂。研究成果可为滇中引水工程隧洞衬砌混凝土温控施工提供参考。

Tunnel lining concrete is a typical example of thin-walled,large-volume concrete.During construction,the high hydration temperature of pumped concrete and the significant constraints imposed by the surrounding rock often lead to temperature-induced cracking.To explore reasonable temperature control measures,we employed three-dimensional finite element software to analyze the temperature field and thermal stress distribution in a typical tunnel lining section of the Central Yunnan Water Diversion Project.Contact elements were used to model the interactions between the surrounding rock and the lining.Based on on-site monitoring data,we performed a feedback analysis on the surface insulation coefficient of the lining section,which was 16.7 kJ/(m 2·h·℃).We investigated how different pouring temperatures,section lengths,seasons,and the autogenous volumetric deformation of concrete affect the thermal stress field of the concrete lining.Our findings indicate that higher pouring temperatures increase thermal stress;specifically,a 4°C rise in pouring temperature reduces the minimum anti-cracking safety factor by 0.30.The maximum stress exceeded 3.5 MPa when concrete was poured during high-temperature seasons.Appropriate segment lengths for the lining structure and micro-expansion concrete can enhance crack resistance.The findings offer valuable insights for temperature control in tunnel lining concrete for the Central Yunnan Water Diversion Project.