岩溶管道构造影响下浅部地层温度数值模拟研究

Numerical simulation study of shallow strata temperatures under the influence of karst conduit structures

当含水岩溶构造体存在时,浅部地层温度场会产生变化。浅层测温法可以简单快速地获得浅层地温数据,通过温度差异反演出岩溶构造的分布。为了研究以贵州省盘州市某场地及其周围场地为对象时,浅层测温技术探测岩溶管道构造体的可行性,笔者采用数值模拟方法。结果表明:构造体不同的埋深会显著改变浅部地层的温度,对于单个岩溶构造体(等效直径为0.5 m,水温12℃),可探测深度极限约为66 m;在管道内流体的温度为12℃时,岩溶管道构造体有效流动截面积的增大会降低浅部地层温度,等效直径在0.1~1.0 m区间内改变时,2.0 m处地层温度的变化在0.02℃以内,这使得利用浅层测温法识别岩溶构造体的有效流动截面积变得困难;流体温度在一定范围内(12~18℃)的变化会改变浅部地层温度,尤其是低温流体的影响更为明显。

When a water-bearing karst structure exists,the temperature field of shallow strata will change.The shallow temperature measurement method can quickly and easily obtain shallow geothermal data,and the distribution of karst structures can be inferred through temperature differences.To study the feasibility of detecting karst conduit structures using shallow temperature measurement technology in a site in Panzhou City,Guizhou Province,and its surrounding areas,the numerical simulation methods were used.The results show that different burial depths of the structure significantly change the temperatures of shallow strata.For a single karst conduit structure(with an equivalent diameter of 0.5 m and water temperature of 12℃),the maximum detectable depth is approximately 66 m.When the fluid temperature inside the conduit is 12℃,an increase in the effective flow cross-sectional area of the karst conduit structure will lower the temperature of the shallow strata.When the equivalent diameter changes within the range of 0.1 to 1.0 m,the change in the temperature of the strata at 2.0 m is within 0.02℃,making it difficult to identify changes in the effective flow cross-sectional area of karst structures using shallow temperature measurement.The change in fluid temperatures within a certain range(12 to 18℃)will alter the temperatures of the shallow strata,especially the impact of low-temperature fluids.