冻融循环对硅酸钠固化黄土力学性质的影响

硅酸钠作为一种灌浆材料,常被用于湿陷性黄土的固化工程。冻融循环会影响季节冻土区固化黄土的结构,从而导致其力学性质发生变化。以兰州黄土为研究对象,分别对冻融循环前后掺量为3%的硅酸钠固化黄土进行压汞试验和力学强度试验,从强度、刚度、能量耗散和土体微观孔隙结构等方面探讨冻融循环作用对硅酸钠固化黄土力学特性的影响。结果表明：一方面,冻融作用会增大土中平均孔隙直径,降低微孔隙含量,导致土样产生裂隙;另一方面,硅酸钠反应生成的Na⁺在水分梯度作用下迁移至土样和裂隙表面并重结晶,上述作用破坏了土颗粒间胶结,最终大幅度劣化了固化黄土力学性能。随着冻融次数的增加,硅酸钠固化黄土无侧限抗压强度在单轴加卸载过程中的能耗值、弹性变形量和滞回环回弹模量均呈现下降趋势,冻融20次后强度降幅高达85.33%,而能耗均值与回弹模量均值分别为未冻融状态下的8.68%和20.70%,即固化土消振性与刚度大幅劣化。鉴于此情况,季节冻土区盐渍黄土硅酸钠的固化处理措施应慎重使用。     

青藏铁路通风路基边界条件研究

In permafrost regions, many methods about active cooling embankment are put forward, one of these representations is ventilated embankment, its cooling effect is the result of the air convection in the duct, and this leads to reducing the annual average ground temperature. The present work in this article is to determine the boundary conditions of the ventilated embankment and natural ground in numerical work. There are several effects which influence boundary conditions, they are: radiation, evaporation,phase change, convection and embankment material etc. Radiation and convection are the main effects in those. We mainly consider sun radiation in this article. The added-surface effect in ventilated embankment lowers its temperature, so the temperature on the wall of the ventilated embankment is different from the temperature in atmosphere. There are two methods in determining the surface temperature, experimental method and experiential method. Detailed research is discussed in the article.     

无人飞艇的差分GPS辅助空中三角测量精度分析

针对普通数码相机应用于低空摄影测量大比例尺成图时存在的像幅小、像片数量多、摄影基线短等一些实际问题,山东科技大学与中国测绘科学研究院联合设计研发了带差分GPS的自稳定双拼相机低空无人飞艇航测系统;本文详细介绍了系统的组成,并进行了低空航摄实验,设计了多种GPS辅助空三加密方案,对加密结果精度进行了对比分析,实验结果表明:采用该系统进行低空摄影测量,进行少量控制点布点差分GPS辅助空三的结果满足大比例尺测图空中三角测量规范要求。     

Analysis on spatial distribution and correlation of pavement distress along the Xinjiang-Tibet Highway北大核心CSCD

The Xinjiang-Tibet Highway（XTH）is a transportation corridor of manpower and supplies from inland regions to Tibet. The XTH has the highest altitude in China,which also has complex geological conditions and high distress ratio. The pavement distress was investigated completely to analyze the spatial distribution of pavement distress along the XTH and reveal the relationship among different types of distress. The distress ratio of 7 types of pavement distress was obtained and the relationship of pavement distress and ground surface temperature,altitude and vegetation cover was quantitatively fitted along the XTH. The result shows that,distress occurrence ratio of racking is has the largest percentage,which is the main reason to reduce the road condition. Pavement distress has a positive correlation and interaction with each other. One type of distress appears with the formation and development of other types of distress. The pavement cracking of the roadway with high altitude was obviously influenced by solar radiation and freeze-thaw cycle,which has a larger occurrence scale and development ratio than other regions. This paper reveals the relationship of each pavement distress and environmental factors,and provides a scientific basis and theoretical reference for the operation,maintenance and distress treatment of the XTH and planning Xingjiang-Tibet transportation corridor. © 2022 Science Press (China).