低热水泥混凝土在特高拱坝中应用的可行性分析

针对低热水泥混凝土早期强度低,在大坝主体中应用较少,低热水泥混凝土能否应用于高拱坝工程仍存疑虑的情况,以白鹤滩工程为例,采用室内试验资料对比和有限元仿真结果对比相结合的方法,对白鹤滩拱坝拟采用的中热水泥混凝土和低热水泥混凝土的材料特性和温度应力仿真结果进行了对比分析。结果表明,从材料特性的角度来看,低热水泥与中热水泥混凝土各有优劣,低热水泥混凝土早龄期强度低不利于防裂,但低热水泥的绝热温升低、早期发热慢、弹模小、徐变大这些因素均有利降低整体应力水平,后期强度高则有利于提高后期安全系数,降低开裂风险。此外,有限元计算结果表明,在相同的温控措施和边界条件下,低热水泥混凝土最高温度比中热水泥混凝土低2～3℃,低热水泥混凝土冷却全过程的安全系数均要大于中热水泥混凝土,且在2. 0以上。研究成果进一步证实了低热水泥混凝土比中热水泥混凝土具有更好的抗裂特性,可以应用于特高拱坝,也为白鹤滩拱坝全坝采用低热水泥混凝土提供了重要支撑。

Analysis on feasibility of application of low-heat cement concrete to construction of ultra-high arch dam

Aiming at the problems from the application of low-heat cement concrete， i. e. lower early strength， less application tothe construction of the main body of dam， the doubt of whether it can be applied to the construction of high arch dam， etc. ， acomparative analysis is carried out on the results from the simulations made on the material characteristics and the temperaturestresses of both the mid-heat cement concrete and the low-head cement concrete which are planned to be applied to the construc-tion of Baihetan Arch Dam through the method of combining the comparison of the in-door experimental data with the comparison of the results from the relevant finite element simulations by taking Baihetan Project as the study case. The result shows that inthe aspect of the material characteristics， both the mid-heat cement concrete and the low-head cement concrete have their ownmerit and defect. The early strength of the low-heat cement concrete is lower and then is unfavorable for anti-cracking， but all thefactors of it， such as low insulation temperature rise， slow early heat-production， small elastic modulus and large creep， are fa-vorable for lowering the integral stress level， while its high late strength is favorable for enhancing the late safety coefficient andlowering cracking risk. Moreover， the relevant finite element calculation result shows that the highest temperature of the low-heatcement concrete is lower than that of the mid-heat cement concrete by 2 ～ 3 ℃ ， while the safety coefficient of the whole coolingprocess of the low-heat cement concrete is larger than that of the mid-heat cement concrete， which is over 2. 0. This study resultfurther demonstrates that the low-heat cement concrete has much better anti-cracking behavior than that of the mid-heat cementconcrete， and then can be used for the construction of ultra-high arch dam， thus can provide an important support for adopting thelow-heat cement concrete for the construction of the whole body of Baihetan Arch Dam as well.