不同埋深扩体锚杆竖向拉拔破坏模式试验研究

通过室内模型试验,研究砂土中竖直埋设的扩体锚杆在不同埋深条件下的竖向拉拔破坏模式。试验结果表明,扩体锚杆经过竖向拉拔,由于深径比的不同而存在3种破坏模式。浅埋扩体锚杆破坏体近似呈倒钟形并延伸至砂层表面,破坏模式属整体剪切破坏,在工程设计中应避免采用。深埋扩体锚杆破坏体在砂层表面以下一定深度内闭合成为"椭球形",砂层表面在扩体锚杆破坏后未产生变形,破坏模式属局部剪切破坏。因此,在工程设计中扩体锚杆应采用深埋形式。在浅埋与深埋扩体锚杆之间还存在一种过渡型锚杆,其破坏体形态兼具深埋与浅埋扩体锚杆破坏体的特征,但破坏模式趋近于浅埋锚杆,因此将其归类为浅埋锚杆破坏模式中。

MODEL TEST RESEARCH ON FAILURE MODES OF DIFFERENT EMBEDDED DEPTH UNDERREAMED GROUND ANCHOR UNDER VERTICAL PULLOUT

The failure modes of underreamed ground anchors in sand under vertical pullout,which were embedded in various depths,were researched by model test.The test results exhibited three different modes of failure depending on the embedment ratio.The rupture surface of shallow underreamed anchor presented like an inverted bell,inclined slightly inward as it extended to the sand surface.The failure mode of shallow underreamed anchor was known as general shear failure,shallow underreamed anchors should not be used in practice.The rupture surface of deep underreamed anchor was completely limited inside sand and presented like a ellipsoid.There was no deformation in the shallow sand layer either during or after pullout,and the failure of underreamed anchors embedded in deep sand resulted from local shear failure.It was highly recommended to apply the deep underreamed ground anchors in design.There was another type of underreamed anchor between shallow and deep underreamed anchors,namely the transitional anchor,and a combined failure surface of the anchor was appeared in the failure zone.But the failure mode of the transitional anchor was near to the shallow one,which was classified as the shallow failure mode.