砂岩地基中架空输电线路抗拔基础承载性能的现场试验研究

Field experimental study on bearing capacity of uplift foundation for overhead transmission line in sandstone foundation

本文以砂岩地基中的架空输电线路抗拔基础为研究对象,开展6个相同底径、不同埋深的直柱基础和扩底基础的现场抗拔承载性能试验,分析了6个试验基础的荷载—位移曲线、抗拔承载力、地基破坏范围及混凝土利用效果。结果表明:两种型式基础的弹塑性变形能力均会受到基础埋深的影响;根据双直线交点法确定试验基础的抗拔承载力,基础埋深相同时,扩底基础抗拔承载力可达直柱基础的1.2~2.0倍;基础破坏时,在地表处形成径向和环向分布的裂缝,且随着埋深的增加,地表破坏半径逐渐减小;采用上拔角定量表示地基破坏范围,则对于相同埋深的抗拔基础,扩底基础的上拔角均大于直柱基础,表明其提高基础抗拔承载力的同时,也加大了地基岩体的破坏范围;以基础抗拔承载力与混凝土消耗量的比值M定量表征不同基础型式和埋深条件下混凝土的利用效果,扩底基础对混凝土的利用效果最高可达直柱基础的5.9倍,工程应用中建议优先选用扩底基础。

Taking the uplift foundation of overhead transmission line in sandstone foundation as the study object,the field uplift bearing capacity tests of six straight column foundations and expanded foundations with the same bottom diameter and different buried depths are carried out.The load-displacement curves,uplift bearing capacity,failure range of foundation and concrete utilization effect of the six test foundations are analyzed.The study results show that the elastic-plastic deformation ability of the two types of foundations is affected by the depth of the foundation.According to the method of double straight line intersection,the uplift bearing capacity of the foundation with expanded bottom can reach 1.2~2.0 times of that of the straight column foundation with the same buried depth.When the foundation fails,the radial and circumferential cracks are formed at the surface,and the failure radius of the surface decreases with the increase of the buried depth.The upper drawing angle is used to quantitatively represent the failure range of the foundation.For the uplift foundation with the same buried depth,the uplift angle of the expanded foundation is larger than that of the straight column foundation,which indicates that the uplift bearing capacity of the foundation is increased,and the failure range of the foundation rock is also increased.The utilization effects of concrete under different foundation forms and buried depths are quantitatively characterized by the ratio M of the foundation tensile capacity and the concrete consumption.The utilization effect of the expanded foundation on concrete is up to 5.9 times that of the straight column foundation.It is suggested that the expanded foundation should be preferred in engineering applications.