严寒条件下面板堆石坝长面板一次拉成裂缝成因分析

因工期及气候条件限制,部分严寒地区面板堆石坝的混凝土面板需一次拉成。通过对某面板堆石坝工程面板混凝土材料体系、环境条件、堆石体结构和垫层接触面特性、养护及越冬措施等因素对面板开裂影响的研究,结合现场实测裂缝性态,分析了严寒地区一次拉成长斜面混凝土面板施工期裂缝的成因。结果表明:混凝土胶凝材料体系绝热温升值高,温度收缩、自生收缩、干燥收缩大是面板开裂的内因;混凝土浇筑温度高、昼夜温差大、养护水温较低,越冬期混凝土温降绝对值大,是影响面板开裂的环境因素;垫层接触面对面板约束程度对混凝土面板内部的受力状态、应力水平和分布特性有显著影响;喷涂乳化沥青可有效降低面板的受约束程度,减小开裂风险。预防和减少面板混凝土裂缝的发生,应从混凝土材料体系、堆石体和垫层结构、环境因素的控制等方面予以足够重视。

Causes of Cracking on Long Concrete Face Plate of Rockfill DamManufactured by One-off Construction Technique in Cold Region

Many concrete face plates of rockfill dams in cold region should be built by one-off construction technique due to limits of duration and weather conditions. The present paper focuses on the impacts of properties of raw materials, environmental conditions, rockfill structure and properties of interaction zone, curing method as well as insulation measures on the cracking performance of concrete face plate. In association with field test data of cracks, the causes of a long concrete face plate in cold region built by one-off construction technique are symmetrically analyzed. Investigations reveal that high adiabatic temperature rising, temperature shrinkage, autogenous shrinkage and drying shrinkage are internal causes of the cracks of concrete face plate in construction stage. Meanwhile, high casting temperature, large temperature difference between day and night, low temperature of maintenance water, and also temperature reduction in winter, as environmental causes, accelerate the crack of concrete face plate. Constraints of interaction zone exert significant impacts on the state, level and distribution of stress. Emulsified asphalt is helpful to reduce the constraints of interaction zone and brings down the cracking risks of concrete face plate.Elements including properties of raw materials,structure of rockfill and interaction zone,and environmental causes should be seriously considered in the design stage,construction stage and curing stage of concrete face plate.