基于压实实时监测的高填方基础薄弱区快速识别研究

Fast Detection Method for Low-bearing-capacity Area of High-filled Subgrade Based on Real-time Compaction Monitoring

高填方路基基础薄弱区域的存在不利于其工后沉降控制。通常采用的事后试验检测不仅无法在事中及时发现薄弱区域反馈施工,且难以实现作业区全域检测。基于智能碾压技术的压路机车载压实监测指标能够表征一定影响深度范围内的基础承载能力,为填筑过程中实时、连续检测高填方基础薄弱区提供了可能。基于此,考虑快速傅里叶变换(FFT)对碾压振动加速度信号进行频谱分析时存在的栅栏效应与频谱泄露现象,提出了基于四项三阶Nuttall窗的改进FFT计算压实监测值的方法;通过现场试验建立了压实监测值与高填方基础回弹模量的关系模型;给出了利用碾压过程中实时采集的压实监测指标进行全工作面快速基础薄弱区域识别的标准与方法。在土石混填高填方路基上的实例应用结果表明:改进FFT方法可抑制频谱泄露与栅栏效应,其计算的压实监测值与基础回弹模量具有强相关性,拟合系数R^(2)为0.8811;提出的薄弱区域快速识别方法能够以较小的误差有效识别薄弱区域。所提方法为高填方基础薄弱区的连续、无损、快速识别提供了有效途径,有助于控制高填方工后沉降,确保公路运行安全。

Low-bearing-capacity areas negatively impact the post-construction settlement control of high-filled subgrades.The bearing capacity of subgrades is traditionally evaluated based on in situ tests on limited samples after construction.These tests cannot detect all the weak areas and feedback in time or provide all the bearing capacity details of the entire area.Roller compaction indexes based on intelligent compaction technology characterize the bearing capacity of a subgrade within a specific depth,providing the possibility for the real-time and continuous evaluation of weak areas during construction.In this study,an improved fast Fourier transform(FFT)algorithm based on the Nuttall window was developed to reduce the impact of the fence effect and spectrum leakage in the spectrum analysis of the acceleration signal of roller vibration using FFT and calculate the roller compaction value accurately.A regression model between the compaction value and the resilient modulus obtained from in situ tests was established.Next,a fast detection method was developed to evaluate the weak area of the high-filled subgrade using the roller compaction value,and a case of a high-filled subgrade filling by earth-rock mixtures was analyzed.The results show that the proposed method can effectively suppress the spectrum leakage and fence effect.A strong correlation exists between the compaction value and resilient modulus,and the R^(2) value of the linear fitting model is 0.8811.Furthermore,the proposed fast detection method can effectively identify low-bearing-capacity areas with an acceptable slight error.This study demonstrates an effective method for the continuous,nondestructive,fast detection of the low-bearing-capacity areas of high-filled subgrades,helpful for controlling post-construction settlements and ensuring the operational safety of high-filled subgrades.