路基宽度对多年冻土区透壁式通风管-块石复合路基降温效应的影响

多年冻土区公路路基大多属高温冻土、极易受工程的影响产生融化下沉,多年冻土区宽幅公路聚热效应尤明显,路基宽度的增加会导致路基病害加重,路基稳定性问题已成为青藏道路工程建设亟待解决的关键问题。透壁式通风管-块石复合路基是一种主动降温措施。为研究其在宽幅公路的冷却效果及路基宽度的变化对路基降温效应的影响,基于块石层和通风管中空气的流速场和多孔介质传热的温度场的特征,采用两相物理场耦合关系,在考虑全球气候变暖以及路基两侧阴阳坡的条件下对宽幅公路透壁式通风管-块石复合路基的温度场进行数值模拟,分析路基施工后10年间的降温效应。研究结果表明:相较于素土路基,透壁式通风管-块石复合路基在路基下侧形成稳定冰核,对宽幅公路的冷却效果更为显著,宽度对路基的风速场和温度场影响明显。路基宽度增大,透壁式通风管风速减小,块石层风速增加,冰核面积及其下移深度增长速率变小,路基稳定时间加长,透壁式通风管-块石复合路基的降温效应逐渐减弱。当路基宽度大于32 m时,块石层风速增长速率明显放缓,低温区域面积增长速率及边缘深度下移增长速率下降,路基稳定时间延长,零温线上升高度减小。

Study on the applicability of frequency spectrum of micro-tremor and dynamic characteristics of surface ground in Asia area

The dynamic characteristics of ground soil using micro-tremor observation in Asia (Zushi and Ogasawara (Japan), Xi’an (China), Manila (Philippines), and Gujarat (India)) are studied. Ground micro-tremor signals were observed and analyzed by fast Fourier transform method (FFT). The response of ground soil to frequency of ground micro-tremor is revealed, and func- tions with frequency-dependence and frequency-selection of micro-tremor for different foundation soil strata are also researched. The horizontal to vertical spectral ratio (H/V, Nakamura technique) of micro-tremor observed at the surface ground was used to evaluate the site’s predominant period. This paper also discusses the application of micro-tremor on site safety evaluation, and gives the observed calculation results obtained at multiple points. The experimental foundation and the deduction process of the method are described in detail. Some problems of the method are pointed out. Potential use of the technique’s good expandable nature makes it a useable means for preventing and reducing disaster’s harmful effects.