基于混凝土水化热效应的高地温水工隧洞衬砌结构温控防裂研究

Temperature Control and Crack Prevention in High Ground Temperature Hydraulic Tunnel Linings: Insights From Hydration Heat Effect of Concrete

为分析高地温水工隧洞衬砌结构温度应力特性,基于拉普拉斯变换推导出衬砌结构瞬态温度场的解析解,并借助弹性抗力法推导出衬砌结构的弹性温度应力分量。依托新疆布伦口水电站监测数据对衬砌结构瞬态温度场及应力场进行计算分析,并采用抗拉强度准则和裂缝尖端强度因子对衬砌结构破坏进行分析,提出合理的温控防裂措施。结果表明:1)衬砌温度场前期整体温度迅速上升,在第7天左右达到最大值,其中衬砌内壁温度可达到37℃,外壁温度可达到56℃。2)衬砌结构外墙环向应力可达到2.2 MPa,体现为拉应力状态;径向应力可达到2.7 MPa,呈现为压应力状态。3)衬砌结构强度的破坏主要受温度及结构本身稳定性2方面影响,可通过采用低热水泥、控制混凝土的入模温度以及严格监控施工过程来提高衬砌的稳定性。其中,采用低热水泥可降低衬砌结构的温升值,混凝土的最终水化热每降低50 k J/kg,衬砌结构内外壁的温差可降低1.85℃左右;适当提高入模温度可缩短水化热的放热周期及降低衬砌内外壁温差。

An analytical solution for the transient temperature field of hydraulic tunnel lining structures in high ground temperature environments is presented using the Laplace transform.The temperature stress characteristics of the lining are examined,and the elastic resistance method is applied to derive the elastic temperature stress components.Using data from the Bulunkou hydropower station in Xinjiang,the transient temperature and stress fields of the lining structure are computed.The analysis incorporates the tensile strength criterion and the intensity factor at the crack tip to evaluate structural damage.The authors propose effective temperature control measures based on the following findings:(1)During early age,the temperature within the lining temperature field surges,peaking on approximately the 7th day with inner and outer wall temperatures reaching 37℃and 56℃,respectively.(2)The circumferential stress on the outer wall achieves 2.2 MPa,indicating a tensile stress state,whereas the radial stress reaches 2.7 MPa,reflective of a compressive state.(3)The structural integrity of the lining is predominantly influenced by temperature and its stability.Enhancements in stability are achievable using low-heat cement,precise control of concrete′s molding temperature,and rigorous construction monitoring.A reduction of the final concrete hydration heat by 50 kJ/kg can decrease the temperature differential between the lining′s inner and outer walls by approximately 1.85℃.Moreover,increasing the molding temperature can expedite the hydration heat release period,thus reducing the temperature variance across the lining.