考虑接触行为的U型渠道冻胀数值模拟

U型衬砌渠道具有良好的整体性和冻胀适应性,但在冬季仍极易因土体冻胀而导致破坏。考虑渠基冻土与衬砌接触面冻结的非线性特性和冻土、混凝土材料的塑性特征,建立能分析渠道基土与衬砌间挤压、脱开及滑移等接触力学行为的渠道冻胀破坏热力耦合数值模型。以宝鸡峡灌区塬下北干渠为原型渠道,按照模型是否考虑接触分别进行冻胀数值模拟,并对模拟结果进行对比分析。结果表明:考虑接触的模型模拟结果与原型实测值更相符,更能合理地解释U型渠道冻胀在渠底与阴坡衔接处冻胀量最小;考虑接触的混凝土塑性应变最大值是不考虑接触时的3.76倍;考虑接触的法向冻胀力和切向冻结力更均匀,最大值均减少1.5~3.0倍,应力集中现象减弱,更能反映混凝土衬砌板与渠基土之间的滑移变形与破坏准则的相互作用。研究结果为U型衬砌渠道冻胀破坏规律提供了分析方法。

Numerical Simulation of Frost Heave Damage of U-shaped Canal Considering Interaction between Concrete Lining Board and Soil

The lining structure of U-shaped canal has favorable integrity and adaptability to frost heave damage; but in winter these canals are still at high risk of frost heave damage. In consideration of the non-linear characteristic of the interface between foundation frost soil and concrete lining as well as the plasticity of frozen soil and concrete lining, we put forward a thermo-mechanical coupling numerical model for U-shaped lining canal, through which the contact mechanical behavior between the foundation and concrete lining such as squeezing, separation and glide can be analyzed. By taking Yuanxiabei main canal in Baojixia irrigation district as prototype canal, we simulated the frost heave damage of the canal in two conditions (considering and not considering the contact between foundation and lining). Results unveil that the simulation results of the model considering the contact are more consistent with the measured values of the prototype, and better explains that the frost heave of U-shaped channel is the smallest at the junction of the channel bottom and the shady slope. The maximum plastic strain of concrete with contact is 3.76 times that without contact. In addition, the normal frost heave force and tangential freeze force considering contact are more uniform, with the maximum values reducing by 1.5~3.0 times. Stress concentration is weakened, which better reflects the interaction between the slip deformation and failure criteria between the concrete lining slab and the canal foundation soil.