砂土中锚板拉拔模型试验及其抗拔力计算

锚板基础因其具有良好的抗拔特性而广泛应用于各类岩土工程问题中。在不同密实程度砂土中采用不同几何形状的锚板进行小比尺拉拔模型试验,分析锚板型式及尺寸对上拔承载特性的影响。试验结果表明,相同直径和埋深比的螺旋锚与平板锚上拔承载特性无明显差别;相同埋深比时,直径为50 mm的锚板上拔承载力系数略小于直径为20mm锚板的上拔承载力系数,而其上拔破坏位移比明显高于小直径锚板。进一步根据破坏位移比与埋深比关系曲线确定中密及密砂中浅、深破坏模式的临界埋深比,同时结合已有试验结果假设两种破坏模式的滑裂面,利用极限平衡分析推导并给出两种破坏模式下上拔承载力公式;通过与41个拉拔试验数据进行比较,验证了所提理论公式的适用性及准确性。

Experimental investigation of uplift behavior of anchors and estimation of uplift capacity in sands

Anchor plates have been widely used in geotechnical engineering due to their good uplift resistance. Small-scale pullout model tests on anchors with various geometries in dry sands are carried out to investigate the influences of type and dimension of anchors on the uplift behavior. The experimental results show that there is no distinct difference of uplift capacity between helical anchor and circular plate anchor with the same diameter and embedment depth. The breakout factors of anchors with a diameter of 50 mm are slightly lower than those with a diameter of 20 mm, and their dimensionless failure displacements are obviously higher than those of anchors with a smaller diameter. The critical embedment ratios of anchors in medium and dense sand are determined based on the relationships of dimensionless failure displacement and embedment ratio, which is used to postulate failure surfaces of shallow and deep modes considering previous experimental results. Accordingly, theoretical formulas for uplift capacity are deduced by means of limit equilibrium analysis. The comparisons between theoretical values and experimental results demonstrate the accuracy of theoretical formulae.