输电线路深井掏挖桩井壁外敷接地特性研究

Grounding Characteristics of Excavated Pile in Deep Well of Transmission Line

现行杆塔混凝土桩基内部钢筋骨架受混凝土介质电阻率的影响散流效率低,提高掏挖桩基散流性能可有效降低接地电阻并减少耕地开挖面积。本研究根据实际杆塔掏挖桩基结构与施工工序,提出深井掏挖桩井壁外敷接地结构模型并验证其降阻效率。首先,根据实际杆塔深井掏挖桩尺寸结构,建立柔性接地材料缆体外敷、面状外敷和组合外敷3种垂直接地模型。然后,分别计算3种井壁外敷结构在单桩情况下的接地电阻变化规律及影响因素,并分析不同接地模型的混凝土桩基散流密度特征。最后,计算整塔四桩基采用井壁外敷结构的降阻效率并与常规方框射线型接地网进行对比。研究结果表明:杆塔掏挖桩基采用井壁垂直外敷,可以明显改变深井掏挖桩基在垂直维度上的散流结构与电流密度分布规律,相比于常规方框外延射线型接地结构,3种井壁外敷方式均能有效降低杆塔接地电阻并节省水平耕地开挖面积。仿真结果可为在有限施工面积下设计掏挖桩基接地结构提供参考。

The current dispersion efficiency of the steel frame inside the concrete pile foundation of the existing pole tower is affected by the resistivity of the concrete medium.Improving the dispersion performance of the excavated pile foundation can effectively reduce the grounding resistance and reduce the excavation area of the cultivated land.Based on the actual tower excavated pile foundation structure and construction procedures,the author proposes a deep well excavated pile shaft wall external grounding structure model and verifies its resistance reduction efficiency.First of all,according to the actual size and structure of deep well excavated piles for towers,three vertical grounding models of flexible grounding material cable external application,surface external application and combined external application are established.Then,the grounding resistance change rules and influencing factors of the three types of externally-coated shaft wall structures in the case of a single pile are calculated respectively,and the characteristics of the concrete pile foundation dispersion density of different grounding models are analyzed.Finally,the resistance reduction efficiency of the four-pile foundation of the entire tower using the externally-coated shaft wall structure is calculated and compared with the conventional box-ray grounding grid.The results of the study show that the vertical external application of the shaft wall for the pole-tower excavated pile foundation can significantly change the vertical diffusive structure and current density distribution of the deep-well excavated pile foundation.All the methods of external application of shaft walls can effectively reduce the grounding resistance of the towers and save the excavation area of horizontal arable land.The simulation results can provide a reference for the design of the grounding structure of the excavated pile foundation under the limited construction area.