基于高密度电阻率成像法的双环入渗过程监测研究

发布时间：2018-01-23 20:52

本文关键词： 双环入渗视电阻率成像侧向入渗饱和渗透系数　出处：《南京大学》2017年硕士论文　论文类型：学位论文

【摘要】：渗水试验(试坑、单环或双环)是水文地质工程地质勘查中评价地表土层垂向入渗能力的常用方法。这种方法把环内水通过包气带到达潜水面的运动近似看作一维垂向运动,应用Ampt-Green模型,解出土层的垂向饱和渗透系数。或者当试验时间比较长,水头下降速度达到稳定时,这时可忽略环中水柱高度的影响,近似认为垂向水力梯度为1,最终水头下降速度便是土层垂向饱和渗透系数Ks。试验结果常用来评价降雨、湖泊、河流的入渗补给能力。其中双环法,由于外环促进了内环中水体的垂向入渗作用,减少了内环水体侧渗所带来的误差,因此测量精度普遍比试坑法和单环法要高,应用广泛。然而,正如所有入渗试验所具有的不足一样,双环法所测定的结果也仅仅是反映了试验土壤的一个综合性参数,它很难获取地下介质的非均质信息。为此,进一步研究双环法测定试验中水体在多孔介质中的实际入渗过程就具有非常重要的意义。本文基于识别介质渗透特性的目的,在甘肃北山高放废物预选区的新场场址区采用高密度电阻率成像监测方法进行了双环入渗试验,以认识双环法中的水体入渗过程,为根据双环法所获得的饱和入渗系数提供更可靠的支持。并进行紫金山和滁州水科院试验基地双环入渗电法监测成像试验。通过本研究获得了以下成果:1.建立了电阻率模型,运用RES2D软件模拟了双环入渗初始状态和稳定状态视电阻率成像情况。2.采用了 GMS软件模拟稳定状态双环入渗情况。建立数值模型,分析内外环插入深度对双环入渗的影响。发现内环相对外环有更好的约束作用,同时,外环对内环垂向入渗作用也不可忽略。3.应用电阻率成像法对北山双环入渗过程进行了二维监测研究。分析了入渗过程不同深度测点视电阻率变化,近似得到了分层饱和的时间。分析同一深度所有测点视电阻率变化,近似得到了入渗锋面的推进情况。外环的侧向入渗,及其对内环水流垂向入渗的促进作用通过视电阻率等值线图能够体现,双环装置对于水流的入渗路径有一定的影响。4.进行了紫金山和滁州水科院试验基地双环入渗试验,获取入渗系数,由于气候潮湿,粘土具有很好的持水性,初始含水率高,采用湖水、地下水入渗时,入渗区的电阻率响应不明显。当自来水入渗时,电阻率出现增大的现象。进行了盐脉冲双环入渗,入渗区电阻率减小。说明在场地附近取水入渗电阻率特征不明显时,可以尝试采用自来水作为高阻体,盐水作为低阻体进行入渗监测。采用视电阻率相对变化图能更好的显示入渗过程电阻率变化情况。
[Abstract]:Seepage test (test pit). Single ring or double ring) is a common method for evaluating the vertical infiltration ability of surface soil in hydrogeological engineering geological exploration. This method approximately regards the movement of water in the ring through the aeration zone to the diving surface as one dimensional vertical motion. Using Ampt-Green model, the vertical saturated permeability coefficient of soil layer can be calculated. Or when the test time is longer and the velocity of water head drop is stable, the influence of water column height in the ring can be ignored. It is considered that the vertical hydraulic gradient is 1 and the final velocity of water head descent is the vertical saturated permeability coefficient of soil layer. The experimental results are often used to evaluate the infiltration and recharge capacity of rainfall, lakes and rivers. Because the outer ring promotes the vertical infiltration of the water body in the inner ring and reduces the error caused by the lateral seepage of the inner ring water body, the accuracy of the measurement is generally higher than that of the test pit method and the single ring method. However, it is widely used. Just like the shortcomings of all infiltration tests, the results measured by the double ring method only reflect a comprehensive parameter of the test soil, and it is difficult to obtain heterogeneous information of underground media. It is very important to study the actual infiltration process of water in porous media by double loop method. The purpose of this paper is to identify the permeability characteristics of porous media. In order to understand the process of water infiltration, a double-ring infiltration test was carried out in the new site area of Beishan high radioactive waste preelection area in Gansu Province by using high-density resistivity imaging monitoring method. In order to provide more reliable support according to the saturated infiltration coefficient obtained by the double ring method, and to carry out the double ring infiltration electrical monitoring imaging test in the experimental bases of Zijinshan and Chuzhou Institute of Water Science, the following results have been obtained through this study:. 1. The resistivity model is established. RES2D software is used to simulate the initial and stable state of dual ring infiltration. 2. The GMS software is used to simulate the steady state of double ring infiltration. The numerical model is established. The influence of the insertion depth of the inner and outer rings on the double ring infiltration is analyzed. It is found that the inner ring has a better constraining effect than the outer ring, and at the same time. The effect of the outer ring on the vertical infiltration of the inner ring can not be ignored. 3. Using the resistivity imaging method, the 2-D monitoring of the infiltration process of the Beishan double ring is carried out. The apparent resistivity changes at different depth points during the infiltration process are analyzed. The time of delamination saturation is obtained approximately. The change of apparent resistivity at all measuring points at the same depth is analyzed. The advance of infiltration front and lateral infiltration of outer loop are obtained approximately. And its promotion to the vertical infiltration of the inner ring water flow can be reflected by the apparent resistivity isoline diagram. The double-ring device has certain influence on the infiltration path of water flow. 4. The double-ring infiltration test was carried out in Zijinshan and Chuzhou Water Institute, and the infiltration coefficient was obtained. Because of the humid climate, the clay has a good water holding capacity. When the initial water content is high, the resistivity response of the infiltration area is not obvious when the lake water is used and the groundwater is infiltrated. When the tap water is infiltrated, the resistivity increases, and the salt pulse double loop infiltration is carried out. The resistivity of infiltration area is reduced. It shows that tap water can be used as high resistivity body when the resistivity characteristics of water infiltration near the site is not obvious. The salt water is used as the low resistivity body to monitor the infiltration. The relative change diagram of apparent resistivity can better display the change of resistivity during infiltration.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.322

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