不同地下水流系统模式渗流场和温度场的互相影响

Interaction between seepage and temperature fields in different groundwater flow systems

在地热资源丰富的地区,需要研究不同地下水流系统发育模式下渗流场和温度场的互相影响。基于二维潜水盆地多源汇的数值模拟和室内砂箱实验,改变降雨入渗强度,通过砂箱底部加温研究上下边界不同温度差条件下的渗流场和温度场的变化。研究结果表明:①随着降雨入渗强度加大,地下水流速增大,地下水流系统由单一区域系统向复杂的局部+区域、局部+中间+区域多级嵌套系统转化,水流对温度的再分配影响变大;②补给区等温线受下降水流影响下移,排泄区等温线受上升水流影响上抬,其中区域补给区和区域排泄区温度变化幅度最大;③砂箱底部加热后,含水层潜水面下降,地下水流速增大,流线循环深度整体变大,滞留带范围缩小。温度差是地热丰富地区的地下水流系统研究中不可忽视的驱动力。

In the regions with rich geothermal resources, it is necessary to study the interaction between the seepage and temperature fields under different groundwater flow systems.Based on numerical simulation and sandbox experiments in a two-dimensional unconfined groundwater basin with multi-sources and sinks, we changed the rainfall infiltration intensity and studied the changes of seepage and temperature fields under different temperature difference between surface and bottom by heating the sandbox bottom.The results showed that with the increasing of the rainfall infiltration intensity, the groundwater velocity increased, groundwater flow systems presented changes from single regional system to a complex local-regional nested system and local-intermediate-regional nested systems, and the groundwater flow had a greater impact on the temperature redistribution.The isotherm in the recharge area moved down under the influence of downward groundwater flow, while the isotherm in the discharge area was lifted up under the influence of upward groundwater flow.And the temperature change in the regional recharge and discharge areas were the most obvious.After heating the sandbox bottom, the water table of the unconfined aquifer decreased and the groundwater velocity increased.Overall penetration depth of streamline became larger, and the scope of stagnant zones decreased.The geothermal energy becomes a nonnegligible driving power in the study of groundwater flow systems in rich geothermal areas.