水平荷载下基桩分布式变形检测模型试验研究

Research on Distributed Detection of Pile Deformation under Horizontal Load in Model Test

为克服传统测试技术获取水平荷载作用下基桩变形的不足,开展基于光频域反射(OFDR)技术的室内模型桩试验。将光纤对称粘贴于桩表面,检测水平荷载下基桩变形及应力分布,推导基于OFDR的桩身挠度和弯矩计算公式,采用有限元软件ABAQUS模拟桩变形和分析桩土作用。结果表明:基于光纤应变数据,可准确计算桩身沿深度的水平位移分布,理论计算与百分表测值基本吻合;水平荷载作用下,模型桩变形主要集中在地面以下0.2 m范围,桩身弯矩最大值与反弯点深度随荷载增加均有不同程度的增大;数值模拟结果与光纤实测规律基本一致,桩土接触压力随水平荷载增加不断向深部发展。基于OFDR技术的水平荷载作用下基桩分布式变形检测方法是可行的,变形与弯矩计算公式是可靠的。

In order to overcome the deficiency of traditional measurement method to obtain the pile deformation under horizontal load,an indoor pile model test based on optical frequency domain reflection( OFDR) technology was carried out. Strain-sensing optical fiber was attached to the surface of the model pile symmetrically. The axial deformation and stress distribution of the model pile under horizontal load were detected. The formula for calculating the deflection and bending moment of the pile body based on OFDR technology was derived. The finite element software ABAQUS was used to simulate the deformation of the model pile under horizontal loads,and the pile-soil interaction was analyzed. The study results show that the distribution of the pile horizontal displacement can be calculated accurately using OFDR based strain sensing data. The theoretical calculation result is basically consistent with the measured value of dial indicator. Under the horizontal load at the top of the pile,the deformation of the model pile mainly occurs in the depth range of 0.2 m below the ground. The depth of the maximum bending moment of the pile body and the depth of the inflection point increase with the horizontal load. Results of the numerical simulations are basically consistent with that of actual measurement. The value and impact depth of contact pressure between the pile and soil increase continuously with the increase of horizontal load. It is feasible to detect the distributed deformation pile model under the horizontal load based on OFDR technology. The pile deformation and bending moment formulas based on OFDR are practical and reliable.