砂土中螺旋锚上拔承载特性模型试验研究

螺旋锚基础因其能够利用深层土体抗力且具有快速安装和承载的优势而广泛应用于各类岩土工程问题中。多锚片螺旋锚上拔承载特性受埋深、锚片间距、数量、土质条件等因素影响。相邻锚片相互影响导致土体破坏区域重叠,从而影响破坏模式和极限承载力,然而多锚片螺旋锚承载特性的理论及试验研究有限。针对砂土中螺旋锚锚片间距及数量对上拔承载特性及极限上拔承载力影响进行室内1g模型试验研究。结果表明,在中密砂及密砂中,单锚埋深比分别超过6.0和10.5时可认为是深埋锚。中密砂中深埋多片螺旋锚锚片间距在3.0D~4.5D时,各锚片承载能力能够独立发挥,承载量破坏模式发生;密砂中浅埋多片螺旋锚保证承载量破坏模式的锚片间距超过6.0D,但间距为6.0D时,螺旋锚发挥效率超过90%。增加锚片数量可适当提高上拔承载力,但当锚片数量增加使得锚片间距小于某一临界值时,柱状破坏模式发生,螺旋锚承载力不再增加;中密砂中此临界间距约为1.5D,密砂中临界间距约为2.0D。

Experimental study on uplift capacity of multi-helix anchors in sand

Helical anchors are widely used to resist uplift loading for a variety of applications involving a wide range of soil conditions. The performance and ultimate capacity of multi-helix anchors depends on the depth of embedment, spacing and number of helixes and soil conditions. The interaction of adjacent helixes can make the overlapping of soil failure zone, which thus will affect the failure mode and ultimate uplift resistance. However, there is very limited experimental study on the problem. The behavior of multi-helix anchors in medium and dense sand is investigated by performing a series of small-scale pullout tests. The embedment ratios for deep anchors in medium and dense sand are regarded as 6 and 10.5 respectively. The critical spacing of helixes of deep anchors in medium sand that makes individual bearing capacity occur is between 3.0D and 4.5D. The critical spacing of helixes of shallow anchors in dense sand is greater than 6.0D, which can reach the efficiency of more than 90%. The uplift resistance will increase with the increasing number of helixes. However, cylindrical failure mode will happen when the spacing decreases to some value due to the increase in number of helixes, which can no longer produce higher uplift resistance. The critical values of spacing are about 1.5D and 2.0D for the medium and dense sand respectively.