西安建筑科技大学学报(自然科学版)

某大桥是国家“一带一路”标志性项目,其桩基础置于弱胶结、多孔隙及高脆性的珊瑚礁灰岩中,传统的桩基设计方法与承载力评估标准并不适用,急需展开研究.开展了大量打入式钢管桩高应变测试,并将测试结果与规范计算结果进行了对比分析,结果表明:(1)钢管桩在打入过程中,其侧壁的礁灰岩结构遭到破坏,产生剪缩与软化现象,无法提供有效的嵌固力,只能以摩擦的方式提供较低的摩阻力,导致钢管桩承载力实测值均远小于规范计算值;(2)珊瑚礁具有结构性,无法产生剪胀效应并持续提供侧摩阻力的增长,致使钢管桩承载力的时间效应不明显,承载力只增长了16%;(3)提出了适用于珊瑚礁地层嵌岩钢管桩的承载力计算方法,建议选择强度相对较高的礁灰岩作为持力层,以桩端受力为主,避免盲目加大桩长或桩径.

The bridge is a landmark project of “one belt and one road” in the country. Its pile foundation is located in the coral reef limestone with weak cementation, porosity and high brittleness. The traditional pile foundation design method and the bearing capacity evaluation standard are not applicable, so there is an urgent need for research. A large number of high strain tests of driven steel pipe piles were carried out, and the test results were comparative analyzed with the calculated results of the code. In-situ static load tests of cast-in-place bored piles were carried out, which were verified by the mechanical tests and numerical simulation methods of coral reef limestone and pile foundation interface. Results show that:(1)During the driving process, the reef limestone structure of the side wall of the steel pipe pile to be damaged, resulting in the phenomenon of shear shrinkage and softening, which can't provide an effective embedment force, so it can only provide a lower friction resistance in the way of friction, resulting in the measured value of the bearing capacity of the steel pipe pile is far less than the calculated value in the code;(2)The coral reef is structural, which can't produce the shear expansion effect and continue to provide the increase of side friction resistance, so that the time effect of the bearing capacity of steel pipe pile is not obvious, and the bearing capacity only increased by 16%;(3)The bearing capacity calculation method for rock socketed steel pipe pile in coral reef is put forward. It is suggested that reef limestone with relatively high strength should be selected as the bearing layer, and the stress at the pile end should be taken as the main force to avoid blindly increasing the pile length or pile diameter.

引言
1 工程背景与地层特点
2 钢管桩竖向承载力计算方法
3 钢管桩竖向承载力的时间效应
4 结论

图1 珊瑚礁分布图<br/>Fig.1 Distribution of coral reefs

图1 珊瑚礁分布图
Fig.1 Distribution of coral reefs

表1 各岩土层设计参数建议值<br/>Tab.1 Suggested values of design parameters for each rock and soil layer

表1 各岩土层设计参数建议值
Tab.1 Suggested values of design parameters for each rock and soil layer

图2 桥梁平面示意图<br/>Fig.2 Plane of the bridge

图2 桥梁平面示意图
Fig.2 Plane of the bridge

图3 桥墩桩基承台尺寸(单位:mm)<br/>Fig.3 Pile cap dimensions of piers(unit: mm)

图3 桥墩桩基承台尺寸(单位:mm)
Fig.3 Pile cap dimensions of piers(unit: mm)

图4 竖向承载力对比<br/>Fig.4 Comparison of vertical bearing capacity

图4 竖向承载力对比
Fig.4 Comparison of vertical bearing capacity

图5 实测端阻力与侧阻力分摊比<br/>Fig.5 Distribution ratio of measured end resistance to side resistance

图5 实测端阻力与侧阻力分摊比
Fig.5 Distribution ratio of measured end resistance to side resistance

图6 海底钢管打入桩桩侧礁灰岩破坏<br/>Fig.6 Damage of reef limestone on the side of pile driven in submarine

图6 海底钢管打入桩桩侧礁灰岩破坏
Fig.6 Damage of reef limestone on the side of pile driven in submarine

图7 钢管桩竖向承载力对比<br/>Fig.7 Comparison of vertical bearing capacity of steel pipes

图7 钢管桩竖向承载力对比
Fig.7 Comparison of vertical bearing capacity of steel pipes

图8 钢管桩竖向承载力的时间效应<br/>Fig.8 Time effect of vertical bearing capacity of steel pipe piles

图8 钢管桩竖向承载力的时间效应
Fig.8 Time effect of vertical bearing capacity of steel pipe piles

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备注

引言

1 工程背景与地层特点

2 钢管桩竖向承载力计算方法

3 钢管桩竖向承载力的时间效应

4 结论

期刊信息