基桩嵌岩段抗拔承载特性现场试验研究

Field Test Study of Bearing Characteristics of Rock-socketed Segment of Uplift Piles

通过现场试验研究了砂岩层中基桩的抗拔承载特性,分析了基桩嵌岩段的破坏机理,提出了嵌岩桩极限抗拔承载力的预测公式,将计算结果与试验值和规范计算值进行了比较。研究结果表明:嵌岩桩的上拔荷载-桩顶位移曲线均为陡变型,增加桩长可以有效地增加承载力,但对桩顶位移的影响有限。试验得到桩岩相对位移为20~25 mm,中风化砂岩层侧阻力达到极限,极限抗拔侧阻力为925.4~961.3 kPa。当桩身强度高于桩周岩体时,基桩的抗拔承载力由桩周岩体的抗剪切强度提供,桩的极限侧阻力可以等效为桩周岩体的抗剪切强度。现行规范的计算值偏于保守,与本文试验值的比值为0.18~0.39。

Based on the field test,the bearing characteristics of uplift piles in the sand strata were studied.The failure mechanism of rock socketed piles were analyzed.The prediction formula of the ultimate uplift bearing capacity of rock socketed piles were proposed.The calculation results,test values and code calculation values were compared.The results show that the uplift load and displacement curve of rock socketed pile is steep.Increasing the pile length can effectively increase the bearing capacity,but has limited impact on the displacement of pile top.The test relative displacement of the pile and rock is 20~25 mm,and the side resistance of the moderately weathered sandstone layer reaches the limit.The ultimate uplift side resistance is 925.4~961.3 kPa.When the pile strength is higher than the rock mass around,the uplift bearing capacity of the pile are provided by the shear strength of the rock around the pile.The limit side resistance of piles can be equivalent to the shear strength of the rock around the pile.The code calculation value are conservative,which is 0.18~0.39 times of the test value.