湿干冻融耦合循环作用下渠道劣化过程离心模型试验研究

Centrifugal model tests on deterioration process of canal under cyclic action of coupling wetting-drying and freeze-thaw

季冻土地区复杂的水-热耦合作用是输水渠道等水工结构物发生劣化失稳的诱因。研制了一套季冻区渠道湿干冻融离心模型试验设备,实现了在离心场下进行湿润—干燥—冻结—融化过程的水-热耦合循环作用模拟。以北疆输水渠道为原型,开展了渠道在湿干冻融耦合循环作用下渠道劣化过程的离心模型试验。试验结果表明:湿干冻融耦合循环作用诱发模型渠道中的裂隙不断拓展,并最终产生一条贯穿渠顶表面的深层横向张拉裂隙,导致渠道有自渠顶张拉裂隙发生劣化失稳的趋势,这一过程中,渠水入渗深度不断增大,入渗量逐渐减小,土体的冻结速率和融化速率呈上升趋势。试验观测出渠坡处产生的累积法向变形最大,渠顶次之,渠底最小。所采用的离心模拟试验设备及测试方法对于寒冷地区渠道灾变问题的研究是适用的。

The complex action of coupling moisture and heat in seasonally frozen soil regions is the inducement of deterioration and instability of hydraulic structures such as canals.A set of centrifugal model test equipment for canal under the cyclic action of coupling wetting-drying and freeze-thaw in seasonally frozen soil regions is developed,which realizes the simulation of cyclic action of coupling moisture and heat during the process of wetting-drying and freeze-thaw in the centrifugal field.The centrifugal model tests are conducted to investigate the deterioration process of the canal in north Xinjiang under the cyclic action of coupling wetting-drying and freeze-thaw.The tests results show that the cyclic action of coupling wetting-drying and freeze-thaw makes the cracks of model canal expand,and eventually produces a deep transverse tension crack across the top surface of the canal,which leads to that the model canal has a tendency of instability from the tension cracks at the canal top.In this process,the infiltration depth of canal water increases and the infiltration volume decreases.The freezing rate and thawing rate show an upward trend.In addition,the final normal deformation at the canal slope is the largest,followed by that at the top of the canal and that at the bottom of the canal.The equipment and method adopted in the centrifugal model tests are applicable to the disaster researches on canals in cold regions.