含水量对渠道保温板保温耐久性的影响及保温板厚度设计

北方渠道大多使用保温板防止混凝土衬砌受冻胀破坏。在计算保温板厚度时为了降低成本,容易忽略保温板使用过程中受各种因素的影响导致保温效果变差的情况,使混凝土衬砌达不到设计使用年限便提前被破坏。内蒙古河套灌区试验结果表明,由于受酸雨、冻融作用、含水量等因素的影响,保温板保温效果平均每年降低0.9℃,其中受含水量变化的影响最大。经试验测得:聚苯乙烯保温板(EPS)含水量每增加1%,会导致导热系数增大5%。基于多层材料串联热阻叠加原理和热阻等效原理,对保温板厚度计算公式进行完善,并提出相应的铺设方法和施工技术要求。该设计对保温板在季节性冻土区的推广应用具有一定参考价值。

Impact from water content on durability of thermal insulation board and design of thermal insulation board thickness

Thermal insulation board is widely used to prevent concrete lining from frost heaving damage for most of the irrigation channels in the north of China. In order to reduce the cost，it is prone to ignore the worsening of the thermal effect of the thermal insulation board caused by all kinds of the relevant factors during the utilization of it，which can make the concrete lining not reach the design working life and damage in advance. The experiment made in Hetao Irrigation District of Inner Mongolia shows that under the impacts from the factors of acid rain，effect of freeze thaw，water content，etc.，the thermal insulation effect of the board therein averagely decreases by 0.9℃ every year，in which the impact from water content is the largest. It is obtained from the relevant test that each increase of 1%of the water content can lead the thermal conductivity to be increased by 5%for the polystyrene insulation board （EPS）. Based on both the superposition principle of thermal resistance in series and the equivalent thermal resistance principle of multilayer material，the formula for calculating the thermal insulation board thickness is improved，and then the corresponding placing method and construction technique are put forward as well. The design has a certain reference value for the popularization and application of the thermal insulation board within the seasonal frozen soil region.