【作者】 温汉辉；

【导师】 万军伟；

【作者基本信息】 中国地质大学 ， 水文学及水资源， 2013， 博士

【摘要】 雷州半岛地区是广东省历史性干旱缺水最严重的区域之一,同时也是地下水水量比较丰富的地区。但该地区的一些地质环境问题(如海水入侵、岩溶塌陷、地面沉降等)凸显出了地下水资源未得到合理开发利用的弊端,因此,开展雷州半岛地区地下水赋存条件、地下水动态特征、地下水循环规律、及地下水资源合理开发利用的研究,对于有效开发雷州半岛地区地下水资源、保护地下水环境具有十分重要的实际意义和理论意义。本文通过收集整理雷州半岛地区基础地质、水文地质及地下水动态监测资料,以地下水系统思想为指导,以水文地质学、地下水动力学理论为基础,采用三维地质建模技术、地下水数值模拟技术和同位素技术,对雷州半岛地下水系统结构、地下水补径排特征、地下水循环规律和地下水资源开发利用及其相关的火山口对含水层结构的影响、对地下水循环规律的影响以及研究区自流井、泉等问题进行综合研究,取得了以下主要成果及认识：1、根据收集的有效钻孔2327个及地质图和剖面图,结合岩相古地理,研究了雷州半岛火山口对研究区地层结构和含水层结构的影响,建立了雷州半岛三维含水层结构模型。该地区含水层分布特征是：浅层含水岩组由埋深30-50m以内的松散岩类孔隙水和火山岩孔洞裂隙水组成,除沿海部分地区缺失或咸水区外广泛分布于全区。中层含水岩组广泛分布全区,仅在玄武岩台地地区随火山岩深度的增加而变薄或缺失,雷北主要为湛江组砂岩,至雷南由于湛江组变薄而逐渐过渡为下洋组上段第二岩组。深层含水岩组几乎遍布全区,仅在西北角及东北角由于基岩埋深浅而缺失,雷北由下洋组下段组成,至需南过渡为下洋组上段第一岩组及部分第二岩组。火山口及火山岩对研究区含水层结构具有重要的控制作用,主要体现在火山口将浅中深三个含水层贯通,使之具有很好的水力联系。2、基于雷州半岛地下水动态观测资料及地下水开发利用状况,结合含水层结构特征,对地下水循环规律及流场特征进行了研究,分析了火山口对地下水循环规律的影响。结果表明,雷州半岛地下水循环及其流场变化主要特征是：(1)浅层水因埋藏浅,易接受大气降雨及地表水体的入渗补给,且未集中开采,迄今未形成区域降落漏斗,流场的形态受地形地貌控制,等水位线与地形等高线形状相似,地下水总体由西北向东南迳流,南部石峁岭火山锥形成局部地下水高水头区,使地下水以石峁岭为中心向四周流动。地下水位仅有季节性波动,年变化幅度一般为2到3m,地下水水位均高于海平面,因此目前基本没有发生严重的海水入侵。(2)中层承压水流场特征是：平面上地下水总体由西北向东南方向流动；垂向上,由于火山口贯通浅中深三个含水岩组,使中层含水岩组接受浅层地下水补给；受人工开集中大量开采影响,水位总体持续下降,已形成多个中心的区域降落漏斗,水位下降2m线圈闭面积达1946km2,漏斗中心水位高程为-21.95m,近海地段除太平地段高于海平面2到5m,东山、东简一带接近海平面之外,其余地区水位均低于海平面。(3)深层承压水流场特征是：中层地下水流场受地形地貌控制比浅中层地下水受地形地貌约束程度小得多,在垂向上受火山口和断层控制,接受中层含水层补给。自二十世纪七十年代起集中开采,水位总体逐年下降,下降速率大；水位埋深2m等值线圈闭面积已达2315km2,漏斗中心水位标高-19.68m,埋深达到25m。不同层位地下水位变化总的规律是由浅至深,变化幅度逐渐增大,降落漏斗面积增大。3、研究了自流井、泉的数值模拟方法。在对自流井、泉的水动力性质进行分析基础上,总结了自流井与泉流数值模拟的特点,分析了自流井与泉的数值模拟的主要难点,提出了相应的解决方案。通过物理模拟试验,发现管道内的实际渗透系数与理想公式计算得到的渗透系数相差1-2个数量级,从而为渗流-管流模型进行自流井、泉数值模拟时的参数选取提供重要参考依据。4、结合雷州半岛地区水文、气象、及各种测试分析资料和地下水动态资料,根据雷州半岛地区地下水系统自流井、泉等特殊的水文地质条件,对MODFLOW程序进行了修改,建立了基于渗流-管流理论的地下水数值模型,更加合理地刻画了自流井、泉等水文地质要素,对雷州半岛地区地下水资源量进行了计算评价。5、选择石峁岭典型火山口区,建立了地下水示踪剂迁移数值模型,计算了火山口地区地下水补径排时间。结果表明第一含水层的地下水年龄比第二含水层的地下水年龄要小,与同位素结果相吻合,其主要原因是在第一含水层与第二含水层之间有一个隔水层,而且隔水层的厚度较大。同时MODPATH表明第一含水层的流线的捕获时间都是1到2年左右,而第二含水层的地下水捕获时间是6年左右,地下水年龄明显比第一含水层的要大。6、根据雷州半岛地区地下水开发现状和潜在需求,设计了两种开发方案,利用所建立数值的模型,对开采方案进行了预测对比。按2010年开采水平,增加20%开采,如果都安排在赤坎、霞山、坡头水源地开采,那么就在2015年后会出现超采现象,所以在规划开采量布局时,除了上述3个水源地按照计算的开采外,欠缺部分按排在铺仔、太平水源地开采补充,并扩大地表水供水能力作为地下水不足部分的补充。如果在2015年及2020年分别在铺仔、东海岛及太平三个水源地开采地下水送到市区或就地工业用水,将会形成次级漏斗中心,同时产生水位迭加,三个水源地的预测水位降迭加,三个水源地的预测水位降2015年铺仔为14.88m、东山为9.37m、太平为13.25m；2020年预测水位下降幅度不大,铺仔为15.63m、东山为10.25m、太平为14.30m。论文主要特色及创新点：(1)根据研究区地下水系统自流井、泉的能够要素特征,采用渗流-管流模型刻画自流井和泉,并修改了MODFLOW程序,实现了对自流井、泉以及混合开采(或注水)井的模拟。(2)揭示了火山口对地下水循环特征的影响和控制作用,建立了火山口示踪剂迁移数值模型,计算了火山口附近地下水循环时间。(3)通过物理模拟试验,发现管道内的实际渗透系数与理想公式计算得到的渗透系数相差1-2个数量级,从而为渗流-管流模型进行自流井、泉数值模拟时的参数选取提供重要参考依据。问题及建议：边界条件的确定也是数值模拟中的难点之一。在数值模型的建立过程中,中、深层侧向边界在海域中的位置难以确定,对于水流模型,可以采用等效边界,但溶质运移模型,等效边界就存在明显不足。建议在以后的工作中,如能收集到研究区的边界资料或有专门的调查研究项目,尽可能对边界条件进行更为准确的刻画。更多还原

【Abstract】 Leizhou peninsula is the most serious drought and water shotage regions in the Guangdong Province, but also is rich in groundwater. Some geological environment problems (Such as sea water intrusion, karst collapse, ground subsidence) highlights the groundwater resource did not get reasonable development and utilization of malpractice. Therefore, it is very important to investigate groundwater storage conditions, characteristics of groundwater fluctuation, groundwater circulation pattern, and the rational exploitation of groundwater resources in Leizhou Peninsula. It is very significant in practical and theory not only for effective development of groundwater resources, protection of groundwater environment, but also for the Leizhou Peninsula sea water intrusion prevention.Through the collection of Leizhou peninsula area of geology, hydrogeology and groundwater dynamic monitoring data, underguiding of groundwater system theory, based on hydrogeological fundmental theory, groundwater dynamic theory and Hydrogeologic chemical theory, using groundwater numerical simulation technology and three-dimensional geological modeling, on the Leizhou Peninsula groundwater recharge runoff drainage of groundwater, groundwater circulation pattern and optimization of exploitation and their relevant problems are studied, the main achievements are as followings:1. Based on the2327borehols, combined with the lithofacies palaeogeography, the impact of crater or volcano formation on the stratigraohic structure in the studied area has been studied and the structure of the aquifer model is established.the chracteristics of aquifer are:the burial depth of the shallow water varies from30m to50m, is consist of loose rock pore water and all the volcano rock cave fissure water, widely distributed in the study area, except for the coastal and brackish water areas. Intermediate confined aquifer water is widely distributed in the study area, it becomes thinner or vanishes as the depth of the volcanic rocks increase in the basalt platform region. The north part of Leizhou Penisula is mainly consisted of sandstones of Zhanjiang group, in the South part of Leizhou Penisula, the Zhanjiang group becomes thinner and gradually transition to the upper group of Xiayang group. Deep confined groundwater almost distributed throughout the region, is only lack of in the northwest corner and the northeast corner of the bedrock buried depth. Lei north from under the ocean group segments, to the south of transition for the thunder under the ocean group upper part the first rock group and part of the second rock group.2. According to the observation data of groundwater water table, and the situation of development and utilization of groundwater resource in Leizhou Penisula, the characteristics of groundwater flow field are studied, the impaction of volcano cater on groundwater flow pattern is studied. It is recognized that groundwater flow field is mainly affected by the hydrogeological conditions, groundwater exploitation mode. The mainly characteristics are as followings:(1) Shallow aquifer is easy to accept the precipitation and surface water infiltration, and is not concentrated mining, hitherto unreported form regional drawdown funnel, the flow patterns affected by topography, the ground water table contour is similar with terrain contour. Groundwater runoff overall from northwest to Southeast. Groundwater table is only seasonal fluctuation, the yearly amplitude is generally2-3m, all most above sea level.(2) The groundwater flow field in the middle confined aquifer has a gradual evalution from natural flow field to artificial exploitation flow. Original condition groundwater flow is generally from northwest to Southeast. Due to the concentration of a large number of exploitation, the groundwater level continued to decline, the central region descend funnel has been formed, the area with groundwater level drop2m is1946km2, funnel center water level is-21.95m. groundwater level is above sea level2-5m in very few of offshore area, the reast offshore area are below the sea level.(3) The groundwater table in deep confined aquifer is drawdown continuously since the concentrated mining groundwater in1970s; the area of ground water drawdown is greater than2m already amounted to2315km2, the groundwater level in funnel center is-19.68m. the groundwater level changes in different layers is from shallow to deep, change rate increase, funnel area increase.3. hydraulic features of the artesian well and spring are analysized, and the numerical methods for modeling artesian flow and soring flow are investigated. An example is designed to test the methods.4. Based on the Leizhou Peninsula3-D aquifer structure model, and the combination of hydrology, meteorology, and all kinds of test data analysis and groundwater dynamic data, a groundwater numerical model is built by using seepage-pipe flow model theory, which taking multilayered pumping well and artesian springs into accounted in the model. the MODFLOW software is modified to realize the calculate the multilayerd aquifer and artician springs flow.5. The groundwater recharge and discharge time in the volcano area is calculated by the groundwater numerical model. The results show that groundwater age in the first aquifer is smaller than the one in the second aquifer, and this is consist with tisotope results. the main reason is that there is an aquifuge between the first and second aquifer, and aquifuge thickness is large. At the same time that the first MODPATH aquifer flow acquisition time is about1-2years, while the second aquifer groundwater capture time is6years, groundwater age in the second aquifer is greater than the one in the first aquifer.6. According to the Leizhou peninsula area of groundwater exploitation and potential demand, two kinds of development programs are designed. The programs were predicted and compared by using the numerical model. The results shownthat:for the program based on the exploitation amount, increase by20%yearly, if this amount watwe is all exploited in Chikan, Xiashan and Potou resource area, then in2015will appear the over-extraction phenomenon. Thus programming exploitation amount layout, in addition to the3water sources in accordance with the calculation of the exploiting, the lack of part according to the row in the Puzai and Taiping water exploiting g supplement, and expand the supply of surface water groundwater insufficient ability as part of the supplementary. If groundwater is exploited for downtown or in situ industrial use from the three groundwater exploitations-Puzai, East Island and Taiping-respectively in2015and2020, a secondary cone center will be formed, three forecasting groundwater level superposition will arise at the same time. In2015, the groundwater level superposition in Puzai will be14.88m, in Dongshan it will be9.37m, in Taiping it will bw13.25m; in2020the forecasting groundwater level will drop a little, the groundwater level superposition in Puzai will be15.63m, in Dongshan it will be10.25m, in Taiping it will be14.30m.Main findings:(1) According to the characteristic of groundwater system with many artesian wells and springs in the Leizhou Penisula, the MODFLOW program is modified based on the seepage-pipe flow model to simulate the ground water flow in the springs and artesian wells system.(2) the impaction and control function on the flow pattern of groundwater are revealed, the tracer migration numerical model is established and is used to calculate the groundwater circulation time in the volcanic area.(3) based on physical experiment, it is found that the real conductive coefficient in practice is lto2orders magnitude greater than that calculated from the ideal formula, this result is very helpful for determing the parameters in using seepage-pipe flow model to simulate artesian well, springs flow in aquifer systems.Sugestions:The determination of boundary condition is one of the difficulties in numerical simulation. When establishing the numerical model, the boundaries are assumed to be constant heads, equivalent to the sea surface elevation. In fact, only the first layer is completely consistent with the assumption. For the intermediate and deep aquifer, the boundaries in the sea are hard to be determined. In the flow modeling, equivalent boundaries are used, but noticeable defects will occur in solute transport model. For more accurate characterization of boundary conditions, more boundary data and specialized investigations are needed in further studies.更多还原