岩溶作用过程试验方法研究——以岩溶作用仪研制为例

Study on test method of karstification process: Take the development of karstification instrument as an example

通过对前人试验装置的分析,以岩溶作用原理及其影响因素为基础,结合仪器使用单位的试验需求,研制岩溶作用仪。通过分析不同的CO_(2)起源、岩溶发育深度、不同pH条件以及地下水循环深度的地质环境条件,提出了仪器的基本功能和适用条件,进行岩溶作用仪功能模块的论证设计和研制,并进行了验证性试验,且达到预期目标。得到如下成果:提出了四种岩溶作用模式,研制了五个岩溶作用功能模块,总结分析了功能模块与岩溶作用内在关系以及功能模块组合原则,提供不同地质环境条件下的岩溶作用试验。仪器可以实现:模拟地下水循环深度0~200 m,环境温度0~70℃,CO_(2)起源:表生、内生起源Pco2=0.0~2.0 MPa,不同酸度背景条件:pH可控,不同水流速度条件下的沉积作用可控,岩溶裂隙张开度的沉积作用(可组合)。

In recent years,with the construction of national economy and the need to achieve the"double carbon goal",a large number of increasingly complex problems on karst science have been encountered,which need to be solved by simulating the process of karst action in different geological environment conditions.In the past,karst simulation was mainly carried out under normal temperature,normal pressure and certain pH conditions to determine the basic characteristics of karst and parameters such as the rate of karst,which could not effectively simulate karst under different geological conditions.Therefore,a comprehensive set of instruments for simulating karst action under different geological environmental conditions(e.g.,ambient temperature of 0-70℃,subsurface depth of 200 m,different CO_(2) origins and different saturation levels,etc.)is needed to solve a series of scientific problems such as karst dissolution and sedimentation in different geological environmental contexts.Based on the principle of karstification,this paper defines the functions and parameters of the instrument by analyzing the geological environment conditions of different CO_(2) origins,karst development depths,different pH conditions and groundwater circulation depths.Based on the requirement of the karstification instrument,the parameters and modules of karstification instrument have been designed according to the instrument functions,karstification control factors and karstification principle.After the design of each part and the overall development of the instrument were completed,a verification test was carried out to illustrate the feasibility of the instrument.Finally,the following results are obtained.(1)Four karstification models are proposed,i.e.,the origin of CO_(2) in the supergene zone—the shallow circulation karstification model of groundwater;CO_(2) origin of supergene zone—cyclic karstification model of groundwater depth;the origin of CO_(2) in the deep—the model of karst process of groundwater depth circulation;and the mode of groundwater circulation karstification under the biological action of supergene zone(such as the change of pH value of humic acid).(2)According to the basic principle of karstification and the four models of karstification,five karstification function modules are developed,CO_(2)(pH)solution function module of different geological environment origins,water circulation depth module,environmental background temperature module,dissolution module and sedimentation module.(3)The internal relationship between functional modules and karstification together with the combination principle of functional modules has been summarized and analyzed to provide karstification tests under different geological environment conditions.Finally,according to the principle of karstification,taking the computer as the basic control unit,the test parameters of different functional modules have been monitored by sensors and controlled by PLC,and the functional modules have been organically connected and controlled to meet the requirement of fully automatic karstification tests under different geological environment conditions.Basic parameters of karstification instrument are listed as follows:(1)simulated groundwater circulation depth of 0-200 m;(2)ambient background temperature of 0-70℃;(3)CO_(2) origins—supergene origin Pco2=0.0 MPa and endogenous origin Pco2=0.0-2.0 MPa;(4)different acidity background conditions—pH value is controllable;(5)sedimentation that can be controlled under different flow velocities;(6)sedimentation of the opening degree of karst fissures(can be combined).However,due to the limitations of time and cost,the instrument can be further improved.For example,in order to improve the preparation efficiency of saturated CO_(2) solution,the contact area between CO_(2) and water can be increased.A dual solution preparation system can be designed to prepare the solution so that the efficiency of the test can be increased.The maximum safe pressure of this instrument is 2 MPa(water circulation depth of 200 m).If a simulation of a greater water circulation depth is needed,the thickness of stainless-steel materials for solution preparation,dissolution reaction kettle and deposition reactor(meeting the requirements of high-pressure vessel specifications)can be increased,and a pressure pump with a larger pressure rise will be used.