Abstract: 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.

Key words:  hydraulic tunnel, Laplace transform, elastic resistance method, tensile strength criteria, tip intensity factor, temperature control and crack prevention