Effect of Artificial Crust Layer on Pile-Soil Stress Ratio of Pipe Pile Composite Foundation
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摘要:
为研究就地固化硬壳层对预应力管桩复合地基桩-土应力比的影响,以绍兴钱滨线泥浆池路段为背景,开展现场试验和数值模拟分析,研究路堤荷载作用下预应力管桩复合地基的受力和变形;从桩-土应力比的角度,着重探讨硬壳层对桩基复合地基承载性能的影响规律;分析路堤高度与桩帽净间距之比、桩帽宽度与桩帽净间距之比等设计参数对桩-土应力比发展的影响机制. 研究结果表明:硬壳层的存在能够有效提高桩基复合地基的承载特性;在本文试验条件下,就地固化硬壳层的预应力管桩复合地基最大水平位移发生在地表以下5~6 m处,区别于传统桩基复合地基的土体水平位移沿深度逐渐降低的规律;桩-土应力比在23~37,高于传统桩基复合地基.
Abstract:In order to study the influence of artificial crust layer formed by in-situ solidified on the pile-soil stress ratio of prestressed pipe pile composite foundation, field experiments and numerical simulation analysis were carried out based on the mud pit section of Qianqing-Binhai highway in Shaoxing. On this basis, both the stress response and deformation of prestressed pipe pile composite foundation under embankment load were studied. From the pile-soil stress ratio, the influence of artificial crust layer on the bearing performance of pile composite foundation was emphatically discussed. In addition, the influence mechanism of design parameters such as the ratio of embankment height to net distance between pile caps and the ratio of pile cap width to net distance between pile caps on the development of pile-soil stress ratio were preliminarily studied. It shows that artificial crust layer can improve the bearing capacity. Under the experimental conditions, the maximum horizontal displacement of artificial crust layer combined prestressed pipe pile composite foundation occurs 5~6 m below the ground surface, which is different from traditional composite foundation decreases gradually along the depth. The pile-soil stress ratio is between 23 and 37, which is higher than that of traditional pile composite foundation.
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表 1 试验段土层的基本物理力学指标
Table 1. Basic physical and mechanical indexes of soil layer
土层 厚度/m 天然湿密度/
(g•cm−3)天然
孔隙比黏聚力/kPa 内摩擦
角/(°)弹性模量/
MPa泊松比 渗透率/
(×10−4 m•d−1)路堤 4.5 2.0 38.0 35.00 0.30 1000.0 土工格栅 3500.00 0.30 桩 80000.00 0.15 硬壳层 3.0 1.85 0.380 300.0 16.0 300.00 0.30 1.0 泥浆 9.0 1.69 2.060 10.0 10.1 2.50 0.35 1.7 粉土 1.0 1.79 0.902 8.2 29.2 4.46 0.35 4.3 粉砂 7.0 1.79 0.735 6.4 30.9 6.32 0.35 43.2 淤泥质黏土 19.0 1.78 1.212 15.0 3.7 2.73 0.35 4.3 表 2 施工参数对比表
Table 2. Comparison of construction parameters
工况 来源 桩长/m 桩径/m 桩间距/m 桩间土
应力/kPa桩顶土
应力/kPa桩-土
应力比褥垫层/硬壳层 1 本文 16.0 0.40 2.5 88.3 2785.8 31.6 3.0 m 硬壳层 2 文献[6] 16.0 0.40 2.5 90.8 2851.1 31.4 3.0 m 硬壳层 3 文献[7] 16.0 0.40 3.0 97.0 3073.8 31.7 3.0 m 硬壳层 4 文献[12] 20.0 0.40 2.0 18.2 375.0 20.6 加筋垫层(土工格栅抗拉
模量1000 kN/m,垫层和整平层
压缩模量 25 MPa)5 2.5 46.6 289.9 6.2 6 3.0 24.3 381.1 15.7 7 文献[12] 14.0 0.40 2.0 24.1 281.0 11.7 加筋垫层(土工格栅抗
拉模量 600 kN/m,垫层和整
平层压缩模量 25 MPa)8 0.30 2.5 40.1 292.2 7.3 9 文献[12] 13.5 0.48 2.7 30.4 350.8 11.5 10 2.2 20.9 269.3 12.9 11 文献[13] 7.0~8.0 0.50 1.2 3.8 0.5 m 砂性土 12 5.0 0.5 m 碎石垫层 13 文献[14] 16.0 1.00 3.0 58.9 624.9 8.9 0.5 m 碎石垫层+土工格栅
(抗拉模量 1180 kN/m)14 文献[20] 3.0~6.0 0.50 1.6 115.1 177.3 1.5 0.5 m 碎石垫层+土工格栅
(抗拉模量 300 kN/m)表 3 参数影响程度
Table 3. Influence degree of parameters
影响因素 影响程度/% 结论 h/s 108.6 高(+) b/s 63.0 高(+) 注:表中“ + ”表示积极影响. -
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