长间歇期对L型混凝土结构上下层温度和应力影响研究

Study on the influence of long intermittent periods on the temperature and stress of upper and lower layers in L-shaped concrete structures

针对船闸底板-导角(L型结构)混凝土浇筑过程中经常出现超过28 d龄期的长间歇期,新混凝土受到老混凝土强约束容易使船闸混凝土结构产生裂缝的问题,依托某大型船闸工程,建立典型闸室底板-导角三维有限元模型,开展了不同施工间歇期(30~180 d)底板-导角混凝土温度场和徐变应力场仿真计算。结果表明:混凝土浇筑季节由春季向秋季顺延,由于外界气候环境变化,导角混凝土最高温度由50.80℃增加至60.77℃,然后下降至52.85℃;上层混凝土对下层混凝土温度影响范围在1.5 m深度左右,新老混凝土接触面附近温度梯度先增加后减小,但间歇期本身对混凝土温度的变化无影响;导角混凝土28 d最大拉应力随着间歇期的延长从30 d到180 d由0.93 MPa增长至1.71 MPa,开裂风险明显增加。

Regarding the issue that long intermittent periods exceeding 28 days often occur during the concrete pouring process of the lock bottom slab-guide angle(L-shaped structure),and that the new concrete is strongly constrained by the old concrete,easily causing cracks in the lock concrete structure,a large lock project was used as a basis.A three-dimensional finite element model of the typical lock chamber bottom slab-guide angle was established to simulate the temperature field and creep stress field of the bottom slab-guide angle concrete under different construction intermittent periods(30 to 180 days).The results showed that as the concrete pouring season shifts from spring to autumn,due to changed in the external climatic environment,the maximum temperature of the guide angle concrete increased from 50.80°C to 60.77°C,then decreased to 52.85°C.The temperature influence ranged of the upper layer concrete on the lower layer concrete was about 1.5 meters in depth.The temperature gradient near the contact surface of the new and old concrete first increased and then decreased,but the intermittent period itself had no impact on the concrete temperature changes.The maximum tensile stress of the guide angle concrete at 28 days increased from 0.93 MPa to 1.71 MPa as the intermittent period extends from 30 days to 180 days,significantly increasing the risk of cracking.