西安建筑科技大学学报(自然科学版)

为了解双排圆形桩在基坑支护中的变形规律和内力分布特性,结合BOTDA分布式光纤传感技术和深层位移监测技术对双排桩在基坑开挖过程中的变形及内力响应进行测试.通过在前、后排桩分别布设传感光缆,采集了从基坑开挖过程到稳定后的应变对双排桩的变形特性及内力,并引入数值模拟与之对比分析.研究结果表明:光纤监测推算的桩身扰度与相应位置的测斜监测的桩身侧向位移曲线规律基本一致,基坑整体变形较小且处于稳定状态,双排圆形桩起到了很好的支护效果; 通过监测应变能真实反映桩身内力分布及传递规律,对比数值模拟成果,双排桩实测弯矩剪力值明显小于模拟值,分布规律基本一致,在前、后排桩上的系梁连接点及坑底以下2 m附近的弯矩较大,后排桩分担的荷载大于前排桩的; 基坑开挖完成后,坑底以上土压力的分布形式呈现“上下部小,中部大”的中凸特征,实测土压力值也小于经典土压力法理论计算值.

In order to understand the deformation laws and internal force distribution characteristics of the double-row circular piles in the foundation pit support, the deformation and internal force response of double-row piles in the process of foundation pit excavation are tested by means of BOTDA distributed optical fiber sensing technology and deep displacement monitoring technology. By laying sensing optical cables in the front and rear piles respectively, the strain from the excavation process to the stability of the foundation pit is collected to study the deformation characteristics and internal forces of the double-row piles, and the numerical simulation is introduced for comparative analysis. The result shows that the pile disturbance calculated by the optical fiber monitoring is basically consistent with the pile lateral displacement curve of the corresponding position inclination monitoring. The overall deformation of the foundation pit is small and in a stable state, and the double-row circular piles have a good supporting effect. By monitoring the strain energy, the internal force distribution and transfer law of the pile body are truly reflected. Compared with the numerical simulation results, the measured bending moment and shear force values of the double-row piles are significantly smaller than the simulated values, and the distribution law is basically the same. The bending moment at the connecting point of the tie beams on the front and rear piles and near 2m below the bottom of the pit is larger, and the load shared by the rear piles is greater than that of the front piles. After the excavation of the foundation pit is completed, the distribution of earth pressure above the bottom of the pit shows a convex characteristic of "small in upper and lower parts and large in middle parts". The measured earth pressure value is also less than the theoretical value calculated by classical earth pressure method.

引言
1 基于BOTDA支护桩受力变形监测
2 工程实例分析
3 光纤测试内力成果分析
4 支护结构数值分析
5 结论

图1 排桩纵断面-监测原理示意图<br/>Fig.1 Vertical section of row of piles-Schematic diagram of monitoring principle

图1 排桩纵断面-监测原理示意图
Fig.1 Vertical section of row of piles-Schematic diagram of monitoring principle

图2 窦官基坑平面示意图<br/>Fig.2 Schematic diagram of Douguan foundation pit

图2 窦官基坑平面示意图
Fig.2 Schematic diagram of Douguan foundation pit

图3 排桩横截面-监测原理示意图<br/>Fig.3 Cross section of row of piles-Schematic diagram of monitoring principle

图3 排桩横截面-监测原理示意图
Fig.3 Cross section of row of piles-Schematic diagram of monitoring principle

图4 窦官基坑典型断面1<br/>Fig.4 Typical section of Douguan foundation pit 1

图4 窦官基坑典型断面1
Fig.4 Typical section of Douguan foundation pit 1

表1 支护桩参数取值<br/>Tab.1 Parameter values of supporting pile

表1 支护桩参数取值
Tab.1 Parameter values of supporting pile

图5 支护桩桩内光缆布设图<br/>Fig.5 Optical cable layout diagram in the supporting pile

图5 支护桩桩内光缆布设图
Fig.5 Optical cable layout diagram in the supporting pile

图6 现场测试图
Fig.6 Field test diagram

图7 后排桩应变分布曲线<br/>Fig.7 Strain distribution curve of the rear piles

图7 后排桩应变分布曲线
Fig.7 Strain distribution curve of the rear piles

图8 前排桩应变分布曲线<br/>Fig.8 Strain distribution curve of front row piles

图8 前排桩应变分布曲线
Fig.8 Strain distribution curve of front row piles

图9 深层位移监测曲线<br/>Fig.9 Monitoring curve of deep-seated displacement

图9 深层位移监测曲线
Fig.9 Monitoring curve of deep-seated displacement

图10 光纤测试侧向位移曲线<br/>Fig.10 Lateral displacement curve of fiber test

图10 光纤测试侧向位移曲线
Fig.10 Lateral displacement curve of fiber test

图11 桩身弯矩分布曲线<br/>Fig.11 The bending moment distribution curve of the pile

图11 桩身弯矩分布曲线
Fig.11 The bending moment distribution curve of the pile

图12 桩身剪力分布曲线<br/>Fig.12 Shear force distribution curve of pile

图12 桩身剪力分布曲线
Fig.12 Shear force distribution curve of pile

图13 开挖完成后土压力实测值与理论值的对比<br/>Fig.13 Comparison between measured value and theoretical value of earth pressure after excavation

图13 开挖完成后土压力实测值与理论值的对比
Fig.13 Comparison between measured value and theoretical value of earth pressure after excavation

图14 Midas数值分析模型<br/>Fig.14 Midas numerical analysis model

图14 Midas数值分析模型
Fig.14 Midas numerical analysis model

表2 土层力学参数<br/>Tab.2 Mechanical parameters of soil layer

表2 土层力学参数
Tab.2 Mechanical parameters of soil layer

表3 支护结构参数及单元类型<br/>Tab.3 Supporting structure parameters and unit types

表3 支护结构参数及单元类型
Tab.3 Supporting structure parameters and unit types

表4 数值分析计算步<br/>Tab.4 Numerical analysis calculation step

表4 数值分析计算步
Tab.4 Numerical analysis calculation step

图15 桩身弯矩分布曲线<br/>Fig.15 Distribution curve of pile bending moment

图15 桩身弯矩分布曲线
Fig.15 Distribution curve of pile bending moment

图16 桩身剪力分布曲线<br/>Fig.16 Shear force distribution curve of pile body

图16 桩身剪力分布曲线
Fig.16 Shear force distribution curve of pile body

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引言

1 基于BOTDA支护桩受力变形监测

2 工程实例分析

3 光纤测试内力成果分析

4 支护结构数值分析

5 结论

期刊信息