黏土–粉土地基掏挖基础抗拔试验研究

Experimental Study on Uplift Behavior of Excavation Foundations in Clay-Silt Foundation

杆塔基础是架空输电线路的重要组成部分,主要承受上拔、下压和水平荷载,其中抗拔荷载是评价杆塔基础承载性能的主要因素,因此开展了分层地基中杆塔基础抗拔承载性能的现场试验研究。本文根据3个掏挖基础的基顶上拔荷载位移曲线和基础周围土体裂缝的开展,分析了黏土–粉土地基掏挖基础基顶荷载位移曲线特性、极限承载力取值和地基破坏模式。结果表明:基础的荷载位移曲线为缓变型,基础埋深增大,其抵抗变形的能力越强;掏挖基础极限承载力及其对应位移的取值方法按大小排序为L1-L2法 >规范法 >双直线交点法 >初始直线斜率法,其中规范法最适合掏挖基础的极限承载力取值;随着基础埋深增加,基础地表宏观裂缝的影响范围先减小后趋于稳定,剖面宏观裂缝的延伸深度逐渐减小,基础的破坏模式为整体破坏。

The transmission tower foundation is an important part of the overhead transmission line,which is mainly subjected to uplift,compressive and horizontal loads.Uplift load is the main factor to evaluate the bearing performance of the tower foundation.Therefore,the tower foundation test on uplift bearing capacity in the layered foundation is carried out.The uplift load-displacement curves of three excavation foundations and the cracks of soil around the foundation are obtained.The load-displacement curve characteristics,ultimate bearing capacity and failure mode of the foundation in clay-silt foundation are analyzed.For the foundation top plane,the load-displacement curve develops slowly.The greater the depth of the foundation in the clay-silt foundation,the stronger its ability to resist deformation.The method of the ultimate bearing capacity of the excavation foundation and its corresponding displacement is sorted,L1-L2 method>norm method>tangent intersection method>slope tangent method.The norm method is most suitable for the ultimate bearing capacity of the excavation foundation.As the foundation depth increases,the influence range of the macroscopic crack on the foundation surface first decreases and then stabilizes;the depth of the macroscopic crack gradually decreases;the failure mode of the excavation foundation is overall failure.