新型伞状抗拔锚的制作及其试验研究

MANUFACTURE AND EXPERIMENTAL STUDY OF A NEW TYPE UMBRELLA-SHAPED ANTI-FLOAT ANCHOR

针对传统锚杆的不足,结合带扩大头桩锚的优点,设计出一种新型伞状抗拔装置,该装置主要由伞状锚头(可在土层中张开)和张拉锚索组成,在制作成型的基础上对其进行3组拉拔试验,其中2组用于比较伞状锚在锚头处灌浆与无浆的承载性能,1组用于比较其与竖直抗拔桩的承载性能。试验结果表明,新型伞状锚的抗拔性能要优于传统的竖直抗拔桩,且锚头灌浆伞状锚的抗拔性能最好。结合试验过程进一步对伞状锚的受力机制展开研究,结果表明,伞状锚的抗拔力主要来源于锚头兜住的土柱重力和兜住土体与未兜住土体之间的剪切摩擦两部分,由此提出伞状锚极限承载力特征值的估算公式,从而为伞状锚的工程应用奠定基础。

A new type umbrella-shaped anti-float device, being composed of stretching anchor cables and an anchor head that can stretch in soil, is designed to perfect the traditional anchors on the basis of fully integrating with the advantages of under-reamed piles and anchors. There are two groups of pullout tests for umbrella-shaped anchor with and without grouting at anchor head, and a group of vertical pile pullout test is done for comparison. The results indicate that the anti-float performance of the new type anchors is better than traditional vertical piles. Moreover, the pullout behaviour of the umbrella-shaped anchor with grouting in anchor head is better. According to the test, the force mechanism of the umbrella-shaped anchor is further analyzed. It is pointed out that the uplift bearing capacity depends on the weight of soil pole wrapped by the anchor head and the shear friction along the interface of soil pole. Therefore the ultimate beating capacity estimation formula of the umbrella-shaped anchor can be presented, which establishes the foundation for the engineering application of umbrella-shaped anchors.