In the joining of waterproof sheets for tunnel lining using the NATM method, heat fusion welding is commonly employed. In this process, two sheets are brought into contact with a heat plate of a heat fusion splicer, where they are fused and crimped together. To enhance quality control, thermal imaging remote sensing inspection can be effectively used to assess the quality of the joint by analyzing the relationship between surface temperature and the tensile strength of the welded area. If the heat transfer behavior of the sheets during joining can be accurately modeled, and a threshold temperature for pass/fail determination can be calculated, this method could significantly benefit sheet joining inspections by reducing the need for time-consuming and labor-intensive tensile tests.
To address this issue, a heat transfer model of geomembrane seam welding is being developed to derive threshold temperatures for detecting faulty welds, applicable to various materials. To verify the model's accuracy, the vertical temperature distribution of the seam was measured. Temperatures at the jointed part and the surface were obtained using thermocouples while the sheets were welded by a self-propelled heat-welding machine. The model values correspond reasonably well with the experimental data under various conditions.
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