软土地基扩径桩竖向承载性能研究
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摘要
扩径桩作为一种软土地基新型处理技术,它的存在使其承载性能优于传统桩基.本文通过在砂土中进行一系列尺寸相似比为10的扩径桩模型试验和PLAXIS 3D建模计算,研究扩径桩在抗压、抗拔条件下的承载性能与扩径体在荷载传递过程中的作用机制.研究结果表明:在良好持力层中,扩径体能显著提高等直径桩的抗压极限承载力1.76倍、抗拔极限承载力2.47倍,明显降低桩顶位移.扩径桩桩身轴力和侧摩阻力在扩径段均发生显著突变,但扩径体两端存在侧阻弱化现象.在下压荷载下,扩径桩表现出多支点摩擦端承桩特性;在上拔荷载下,扩径段的侧摩阻力表现出强化效应.修正了《建筑桩基技术规范》中单桩抗压、抗拔极限承载力参数取值,计算结果与试验值基本吻合,适用于预估扩径桩的竖向承载力.该研究结果可应用于软土地基中良好持力层的桩型选择.
The diameter-enlarged pile is a new technology in soft deposit treatment, due to which its bearing capacity is enhanced. In this paper, a series of model tests, with similar ratio of piles as 10 and PLAXIS 3 D simulation, were conducted to investigate the distribution of bearing capacity and the mechanism of the enlarged parts under compression and tension. The results showed that, in good bearing stratum, the bearing capacity of the pipe pile is remarkably improved by enlarged parts. The capacity of compression and tension is increased by 1.76 times and 2.47 times respectively and the displacement in top pile is reduced markedly. The axial force and the side friction resistance change greatly at the place of enlarged parts, but the side resistance in both ends of enlarged part is significantly weakened. Moreover, the diameter-enlarged pile shows the characteristics of multiple friction pivots in end-bearing pile under compression. The lateral friction of the diameter-enlarged section shows the strengthening effect under tension. The parameters of formulas for predicting the ultimate bearing capacity of single pile under compression and tension in the standard of Technical Code for Building Pile Foundations is revised. The results are in good agreement with the experimental values and suitable for predicting the vertical bearing capacity of diameter-enlarged pile. The research results can be applied to the selection of pile in good bearing stratum of soft deposit.
The diameter-enlarged pile is a new technology in soft deposit treatment, due to which its bearing capacity is enhanced. In this paper, a series of model tests, with similar ratio of piles as 10 and PLAXIS 3 D simulation, were conducted to investigate the distribution of bearing capacity and the mechanism of the enlarged parts under compression and tension. The results showed that, in good bearing stratum, the bearing capacity of the pipe pile is remarkably improved by enlarged parts. The capacity of compression and tension is increased by 1.76 times and 2.47 times respectively and the displacement in top pile is reduced markedly. The axial force and the side friction resistance change greatly at the place of enlarged parts, but the side resistance in both ends of enlarged part is significantly weakened. Moreover, the diameter-enlarged pile shows the characteristics of multiple friction pivots in end-bearing pile under compression. The lateral friction of the diameter-enlarged section shows the strengthening effect under tension. The parameters of formulas for predicting the ultimate bearing capacity of single pile under compression and tension in the standard of Technical Code for Building Pile Foundations is revised. The results are in good agreement with the experimental values and suitable for predicting the vertical bearing capacity of diameter-enlarged pile. The research results can be applied to the selection of pile in good bearing stratum of soft deposit.
引文
[1]高伟杰.扩底桩竖向承载特性模型试验研究[D].淮南:安徽理工大学, 2016.
[2]周韬.竹节管桩抗拔承载特性研究[D].杭州:浙江大学, 2014.
[3] Horiguchi T, Karkee M B. Load tests on bored PHC nodular piles in different ground conditions and the bearing capacity based on simple soil parameters[J].Proceedings of Technical Report of Japanese Architectural Society, 1995(1):89-94.
[4] Karkee M B, Kanai S, Horiguchi T. Quality assurance in bored PHC nodular piles through control of design capacity based on loading test data[C]//Proceedings of the7th International Conference and Exhibition, Piling and Deep Foundations, 1998.
[5] Borda O, Uno M, Towhata I. Shaft capacity of nodular piles in loose sand[C]//Proceedings of the 49th National Conference, Japanese Geotechnical Society, 2007.
[6] Honda T, Hirai Y, Sato E. Uplift capacity of belled and multi-belled piles in dense sand[J]. Soils and Foundations,2011, 51(3):483-496.
[7]高广运,蒋建平,顾宝和.同场地扩底桩和直桩的对比研究[J].岩石力学与工程学报, 2005, 24(3):502-506.
[8]罗照,耿大新,方焘.变截面桩竖向承载性状的模型实验研究[J].武汉大学学报(工学版):2011, 44(6):731-734.
[9]吴江斌,王卫东,黄绍铭.等截面桩与扩底桩抗拔承载特性数值分析研究[J].岩土力学, 2008, 29(9):2583-2588.
[10]王卫东,吴江斌,许亮,等.软土地区扩底抗拔桩承载特性试验研究[J].岩土工程学报, 2007, 29(9):1922-1926.
[11]黄广龙,惠刚,梅国雄.钻孔扩底桩原型对比试验研究[J].岩石力学与工程学报, 2006, 25(9):1922-1926.
[12]胡庆红,张土乔,谢新宇.深厚软土中大直径灌注扩底桩受力性状试验研究[J].土木工程学报, 2007, 40(4):987-991, 103.
[13]建筑基桩检测技术规范. JGJ 106-2014[S].
[14]李连祥,李先军.不同扩径体数量、位置对支盘桩承载力的影响[J].山东大学学报(工学版), 2016, 46(5):88-94.
[15] Teo P L, Wong K S. Application of the Hardening Soil model in deep excavation analysis[J]. The IES Journal Part A:Civil&Structural Engineering, 2012, 5(3):152-165.
[16]建筑桩基技术规范. JGJ 94-2008[S].
[2]周韬.竹节管桩抗拔承载特性研究[D].杭州:浙江大学, 2014.
[3] Horiguchi T, Karkee M B. Load tests on bored PHC nodular piles in different ground conditions and the bearing capacity based on simple soil parameters[J].Proceedings of Technical Report of Japanese Architectural Society, 1995(1):89-94.
[4] Karkee M B, Kanai S, Horiguchi T. Quality assurance in bored PHC nodular piles through control of design capacity based on loading test data[C]//Proceedings of the7th International Conference and Exhibition, Piling and Deep Foundations, 1998.
[5] Borda O, Uno M, Towhata I. Shaft capacity of nodular piles in loose sand[C]//Proceedings of the 49th National Conference, Japanese Geotechnical Society, 2007.
[6] Honda T, Hirai Y, Sato E. Uplift capacity of belled and multi-belled piles in dense sand[J]. Soils and Foundations,2011, 51(3):483-496.
[7]高广运,蒋建平,顾宝和.同场地扩底桩和直桩的对比研究[J].岩石力学与工程学报, 2005, 24(3):502-506.
[8]罗照,耿大新,方焘.变截面桩竖向承载性状的模型实验研究[J].武汉大学学报(工学版):2011, 44(6):731-734.
[9]吴江斌,王卫东,黄绍铭.等截面桩与扩底桩抗拔承载特性数值分析研究[J].岩土力学, 2008, 29(9):2583-2588.
[10]王卫东,吴江斌,许亮,等.软土地区扩底抗拔桩承载特性试验研究[J].岩土工程学报, 2007, 29(9):1922-1926.
[11]黄广龙,惠刚,梅国雄.钻孔扩底桩原型对比试验研究[J].岩石力学与工程学报, 2006, 25(9):1922-1926.
[12]胡庆红,张土乔,谢新宇.深厚软土中大直径灌注扩底桩受力性状试验研究[J].土木工程学报, 2007, 40(4):987-991, 103.
[13]建筑基桩检测技术规范. JGJ 106-2014[S].
[14]李连祥,李先军.不同扩径体数量、位置对支盘桩承载力的影响[J].山东大学学报(工学版), 2016, 46(5):88-94.
[15] Teo P L, Wong K S. Application of the Hardening Soil model in deep excavation analysis[J]. The IES Journal Part A:Civil&Structural Engineering, 2012, 5(3):152-165.
[16]建筑桩基技术规范. JGJ 94-2008[S].