路基湿度测量方法、演化规律及调控技术研究进展

State-of-the-art Review on Measurement Methods,Evolution Laws,and Control Technologies of Subgrade Moisture Field

路基湿度状态是影响道路工程全寿命周期服役性能的关键因素之一。准确测量路基湿度、揭示路基湿度演化规律、提出合理的路基湿度调控技术一直是道路工程的重点问题。近年来,随着科学技术的不断发展,在路基湿度调控的相关研究中涌现出了大量新理论、新方法和新技术。聚焦路基湿度测量方法、演化规律以及调控技术3个方面,系统阐述了国内外有关路基湿度的研究现状。综合分析表明,在路基湿度测量方法上,传统破坏性路基湿度测量方法逐渐被低扰动和非扰动测量方法替代,时域反射技术(TDR)、频域反射技术(FDR)和探地雷达技术(GPR)等新技术为路基湿度测量提供了新方法,但在原位、无损、精准和快速测量方面仍有提升空间。在路基湿度演化规律研究上,理论计算、数值分析和缩尺模型试验是揭示路基湿度演化规律的主要研究手段,并从水-力-热多因素耦合下的非饱和土渗流、多孔介质的流动传热、缩尺模型的搭建等方面对路基湿度演化规律进行了研究与分析。然而路基湿度演化受复杂环境的直接影响,具有明显的时空效应,目前的研究成果尚不足以全面、精确地反映路基湿度演化规律。在路基湿度调控技术上,传统的路基内外部排水系统和以粒料隔离层为代表的路基结构在路基湿度调控方面具有显著效果,但由于无法阻隔路基内部的水汽迁移,其调控效果随着服役时间的增加逐渐减弱。以高性能吸疏水材料为代表的新型调控技术可实现路基湿度的主动调控,但尚未实现路基湿度的精细化、智能化调控,未来可向低成本、高效率和高实用性的路基湿度调控技术方向发展。

Moisture field is a crucial factor that influences the service performance of a subgrade over its full life cycle.Three issues related to the subgrade moisture field have been extensively examined by the engineering community:the measurement method,evolution law,and control technology.Recently,owing to developments in science and technology,many new theories,methods,and technologies have been proposed for subgrade moisture control.In this study,the current state-of-the-art of the moisture field of the subgrade in the categories of measurement methods,evolution laws,and control technology were introduced.Traditional destructive measurement methods are progressively being replaced by minimal or nondestructive measurement methods,such as time-domain reflectometry(TDR),frequency-domain reflectometry(FDR),and ground penetrating radar(GPR).However,these new measurement methods for subgrade moisture still require improvements for in-situ,nondestructive,precise,and rapid measurements.Theoretical calculations,numerical analyses,and model tests are primarily employed to determine the evolution law in subgrade moisture fields.Currently,the moisture evolution in subgrades has been examined from various aspects,such as unsaturated soil seepage subjected to the hydro-mechanical-thermal coupling effect,flow and heat transfer in porous media,and reduced scaling model tests.Considering the complicated service conditions of subgrades,current research on the moisture evolution law still requires further improvements to fully and precisely describe the moisture field of a subgrade in a real environment.In terms of control technology,subgrade structures with commonly used drainage systems and gravel layers can improve the control performance of subgrade moisture.However,the improvement is gradually weakened with service time owing to the failure to block vapor migration inside the subgrade.Represented by high-performance hydrophobic and hydrophilic materials,new moisture control technology can achieve active control of subgrade moisture.However,more endeavors are still required to improve subgrade moisture control technology with higher precision,higher intelligence,lower cost,higher efficiency,and better practicality.