螺锁式异型复合桩承载力试验分析

Test and Analysis on Bearing Capacity of Special-shaped Composite Pile with Bolt-shackle Connection

螺锁式异型复合桩是水泥土桩与植入的螺锁式异型管桩复合而成的桩型,具有成本低和承载力高的优点。以实际工程为依托,对试桩和工程桩进行竖向抗压和抗拔静载荷试验。通过12组抗压试桩破坏性试验、12组抗拔试桩破坏性试验及工程桩承载力验收试验,对异型复合桩承载特性进行研究,试验结果表明:破坏面位于异型管桩内芯与水泥土外芯界面时,荷载位移曲线呈突变型,为脆性破坏,水泥土与桩侧表面的黏结力破坏,导致桩侧极限摩阻力大大降低,随桩周土重新固结,承载力不易恢复;破坏面位于水泥土外芯与桩周土界面时,荷载位移曲线呈缓变型,为塑性破坏,随桩周土重新固结,承载力能恢复破坏前状态;影响异型复合桩承载力的主要因素为水泥土的成桩质量及异型管桩的接桩质量;工程桩承载力验收检测时,需考虑静载荷试验对工程桩的破坏性,设计合理的桩顶位移量限值为试验终止加载条件。

Special-shaped composite pile with bolt-shackle connection is a pile type composed of cementsoil piles and implanted special-shaped pipe piles.It has the advantages of low cost and high bearing capacity.Based on actual project,the author conduct vertical compression and pullout static load tests on test piles and engineering piles.Through the destructive test of 12 groups of compression test piles,the destructive test of 12 groups of uplift test piles and the acceptance tests of engineering pile bearing capacity,the bearing characteristics of special-shaped composite piles are studied.The test results show that: When the failure surface is located in the core or at the cement-soil core interface,the loaddisplacement curve is abrupt and brittle failure.The bonding force between the cement soil and the pile surface is destroyed,resulting in a significant reduction in the ultimate friction resistance of the pile side.As the pile surrounding soil re-consolidates,the bearing capacity cannot fully recover.When the failure surface is outside the cement soil at the interface between the core and the soil around the pile,the loaddisplacement curve shows a gradual change,which is a plastic failure.As the soil around the pile is reconsolidates,the bearing capacity can return to the state before the failure.The main factors affecting the bearing capacity of the special-shaped composite pile are the formation of the cement-soil pile quality and connection quality of special-shaped pipe piles.In the acceptance test of the bearing capacity of the engineering pile,the destructiveness of the static load test to the engineering pile should be considered,and the reasonable limit of the displacement of the pile top is the test termination loading condition.