冻融期内U形渠道混凝土衬砌板下地温分布规律

针对宁夏引黄灌区分布广泛的小型U形渠道衬砌冻融破坏技术难题,基于青铜峡市邵刚镇高标准农田建设区内的小型U形渠道混凝土衬砌板下地温在一个冻融期内的原位观测试验及其数据,分析讨论了衬砌板下地温分布规律及其与极值平均气温之间的关系。研究表明:板下30 cm以下地温与冻融期内时间和极值负积温分别呈较好的二次函数关系,拟合相关系数在0.91以上;板下30 cm范围内的地温同时受到极值气温变化和极值负积温积累效应的影响,地温变化幅度远小于气温的变化幅度;在板下约30 cm处存在准恒地温层;渠道不同观测部位的地温变化规律不一致,冻结期渠底地温总体高于渠内阴阳坡面,融化期渠内阳坡面地温回升速度最快,且与观测时间有密切关系。

Distribution law of ground temperature under concrete lining slab for U-shaped channel during freezing-thawing period

Aiming at the technical problem from the freezing-thawing damage of the concrete lining for the small-sized U-shaped channel that is widely distributed within the Yellow River Irrigation District of Ningxia，the distribution law of the ground temperature under the lining slab as well as the relationship between it and the extreme mean temperature are discussed herein based on the in situ observation experiment and its data of the ground temperature under concrete lining slab of the small-sized U-shaped channel within the high standard farmland construction area of Shaogang Town in Qingtongxia City during a freezing-thawing period. The study shows that the ground temperature 30 cm below the lining slab presents a better quadratic function relationship with both the time of freezing-thawing period and the extreme negative accumulated temperature respectively with the related coefficient of over 0.91. Meanwhile，the ground temperature with the range of 30 cm below the lining slab is impacted by both the extreme temperature change and the accumulated effect of the accumulated negative temperature，while the changing amplitude of the ground temperature is far less than that of the air temperature with a stratum of quasi-constant temperature about 30 cm below the lining slab. The changing laws of the ground temperatures observed at different locations are not so consistent，i.e. the ground temperature of the bottom of the channel is generally higher than those of the sunny and shady slopes within the channel during the freezing-thawing period，while the ground temperature returning speed of the sunny slope therein is most fast during the thawing period and it is closely related to the observation time.