利用示踪试验时间-浓度曲线分析岩溶管道结构特征

岩溶管道结构特征对岩溶水资源的合理取用、保护及地下工程安全施工均具有重要影响。目前在利用示踪试验曲线分析岩溶管道结构特征时，难以通过曲线叠加、钝锋、不规则上升和下降等形态准确解释多条岩溶管道连接关系、地下湖所处位置和地下水状态。运用地下水溶质运移理论，推导出岩溶管道流溶质运移模型，根据模型绘制三维溶质运移形态和理论时间-浓度曲线，结合水力学相关知识，对岩溶管道连接关系、地下湖位置及岩溶管道流形态变化对应的时间-浓度曲线进行解释。得出以下主要结论:（1）曲线出峰个数对应岩溶管道条数，由于管道径流长度及流速存在差异，双管道并联曲线存在3种模型，分别为2个孤立的单峰、下降曲线存在双峰叠加和2个连续上升的叠加峰；（2）单管道曲线下降梯度个数对应地下湖个数，多管道需结合管道个数和地下湖位置具体分析下降梯度和地下湖个数关系，根据地下湖位置将双管道并联岩溶管道划分4种类型，即地下湖存在于未分支管道、主管道、支管道、主管道和分支管道上；（3）曲线形态极速变化标志着管道流发生表流和承压流的相互转化。研究结果可为岩溶地区地下水保护及地下工程安全建设提供保障。

Analysis of structural characteristics of karst conduit by timeconcentration curve of tracer test

The structural characteristics of karst conduit have an important influence on the rational use and protection of karst water resources and the safe construction of underground engineering.At present,when using tracer test curve to analyze the structural characteristics of karst conduit,there are some problems,such as curve superposition shape,blunt front shape,irregular rise and fall of curve,connection relationship between multiple karst conduit,location of underground lake and groundwater state.In this paper,the time concentration curve of tracer test is used to explain the structural characteristics of karst conduit through the numerical simulation of the karst conduit flow tracer test and the change of water flow state.The results are as follows:(1)The number of curve peaks corresponds to the number of karst conduit,and there are three models for the parallel curve of double pipelines due to the difference of the length and velocity of karst conduit runoff.(2)The number of single karst conduit curve decline gradients corresponds to the number of blue hole,and the relationship between the decline gradients and the number of blue hole should be analyzed for multiple karst conduit in combination with the number of karst conduit and the location of blue hole.There are four types of parallel karst conduits.(3)The rapid change of curve shape indicates the mutual transformation of surface flow and pressure flow.