水蒸汽增湿重塑非饱和黄土地基现场应用参数研究

Study on field application parameters of unsaturated loess ground remodeling by humidification of water vapor

天然状态下,非饱和黄土地基中土体含水率较低,导致强夯法处理黄土地基时夯实效果较差,无法满足地基承载特性,因此,如何对黄土地基进行增湿成为研究的重点。为了研究非饱和黄土在水蒸汽作用下的增湿效果,以重塑非饱和黄土为研究对象,开展水蒸汽增湿模型试验,分析了不同水蒸汽压力梯度、花管开孔数量及开孔间距条件下,水蒸汽扩散速率、温度及气体运移随时间的变化规律。结果表明:水蒸汽增湿是含水率梯度、压力梯度和温度梯度三者耦合且相互影响的动态变化过程,其中,温度梯度是影响水蒸汽运移的主要因素。水蒸汽通入土体后,体积含水率、气压和温度在各个测点处随通气时间的推移,均呈现快速上升−逐渐稳定的两个阶段。试验中,增大水蒸汽压力,增湿程度和增湿范围变化明显;增加开孔数量,土体增湿的均匀程度提高;减小开孔间距,土体增湿程度变化不大。研究成果可为水蒸汽增湿非饱和黄土地基相关工程提供一定的经验。

In the natural state,the moisture content of the soil in the unsaturated loess ground is low,resulting in the poor compaction effect of the loess ground by the heavy ramming method,which cannot meet the requirements of ground bearing capacity.Thereby,how to humidify the loess ground has become the focus of the research.In order to study the humidification effect of unsaturated loess under the action of water vapor,the water vapor humidification model experiment was carried out with the unsaturated loess as the research object,and the variation of water vapor diffusion rate,temperature and gas transport with time under different water vapor pressure gradients,the number of flower tube openings and the spacing of open holes were analyzed.The results show that the humidification of water vapor is a dynamic change process in which the moisture content gradient,pressure gradient and temperature gradient are coupled and interact with each other,of which the temperature gradient is the main factor affecting the transport of water vapor.After the water vapor is introduced into the soil,the volumetric moisture content,air pressure and temperature at each measurement point with the passage of ventilation time,all show two stages of rapid rise-gradual stabilization.In the test,Increasing water vapor pressure results in significant changes in the degree and range of humidification,and raising the number of open pores,the uniformity of soil humidification increased.Reducing the spacing between the opening pores and the degree of humidification does not change much.The research results can provide certain experience for the engineering of water vapor humidification of unsaturated loess foundations.