螺杆灌注桩竖向抗拔承载特性的模型试验研究  

Model test of vertical uplift bearing capacity of screw cast-in-place piles

作　　者：王浩宇 Wang Haoyu(Institute of Foundation Engineering,China Academy of Building Research,Beijing 100013,China)

机构地区：[1]中国建筑科学研究院有限公司地基基础研究所,北京100013

出　　处：《建筑科学》2022年第3期119-128,共10页Building Science

摘　　要：螺杆灌注桩是一种桩身上部为直杆、下部为螺纹的组合新桩型。当前《螺杆灌注桩技术规程》(T/CECS 780-2020)中关于螺杆灌注桩抗拔极限承载力的计算方法未有明确,继续按照现有抗拔桩基承载力计算方法对其进行设计计算将存在误差,因此需对其展开进一步研究。通过砂箱模型试验,采用图像处理分析技术和桩身应变测试技术相结合的试验方法,分析模型桩在抗拔过程中荷载-位移曲线、桩周土体的位移场和内力、侧阻力的分布,揭示了螺杆灌注桩竖向抗拔承载特性。结果表明:在均匀砂土中,螺杆桩与直杆桩相比可以较大提高单桩的抗拔极限承载力,且随着砂土相对密实度的增加而效果增强;螺杆桩荷载-位移曲线的陡升段相对直杆桩更加平缓;螺杆桩在上拔荷载作用下,螺牙上侧桩周土被挤密成楔形体向上移动,随着相对密实度的增加楔形体高度增加,破坏时螺牙间形成连续的拱形位移场。Screw cast-in-place pile is a kind of composite cast-in-place pile whose body part is cylindrical and lower part is threaded. At present, the calculation method of ultimate bearing capacity of screw cast-in-place pile is not clear in "Technical Specification for Screw cast-in-place Pile"(T/CECS 780—2020), so there will be errors in calculating and designing the ultimate bearing capacity of screw cast-in-place pile based on the existing calculation method. Therefore, it is necessary to carry out further research.Through sand box model test, the load-displacement curve of model pile, the displacement field of soil around the pile and the distribution of internal force and lateral resistance are analyzed by combining image processing analysis technology and pile strain testing technology, and the vertical uplift bearing characteristics of screw cast-in-place pile are revealed. The result shows that: in the homogeneous sand, the ultimate bearing capacity of single pile can be greatly improved by screw pile compared with straight pile, and the effect is enhanced with the increase of relative compactness of sand. The steep rise of load-displacement curve of screw pile is more gentle than that of straight rod pile. Under the action of uplift load, the soil around the upper screw teeth is squeezed into a wedge shape and moves upward. With the increase of relative compactness of sand soil, the height of the wedge shape increases, and a continuous arch displacement field is formed between the screw teeth in the failure stage.

关 键 词：螺杆灌注桩 竖向抗拔 桩侧阻力 室内模型试验 图像分析技术 

分 类 号：TU473[建筑科学—结构工程]