填海工程背景下半岛地下水流场及污染物运移的数值模拟分析

以古雷半岛为例,基于GMS地下水数值模型探索海砂填海(情景一)、海砂+黏土填海(情景二)、黏土填海(情景三)这三种填海情景对研究区地下水流场及污染物运移的影响。结果表明:(1)研究区在填海背景下地下水水位整体抬升,水位上升幅度由小到大依次为情景一、情景二、情景三,最高升幅达4.78m。(2)不同填海情景下的地下水流场差异在填海区的黏土区域最为明显,情景二、情景三与情景一的地下水水位差最大值分别为4.44 m和8.20m。(3)在仅考虑物理作用的情况下,三种填海情景下污染物运移均呈现以水平运移为主、垂向运移为辅的特点。(4)相较于污染物运移基本相同的情景一与情景二,预测时间30a时,水平方向上情景三污染物迁移面积、迁移速率分别下降23.07%、18.89%;垂向上污染物主要积聚于第一层含水层,情景三观测井在第一层含水层的污染物浓度为情景一(或情景二)的5.87倍。说明采用低渗透性黏土填海对于污染物运移具有一定的阻滞作用。

Numerical simulations of peninsula groundwater flow and contaminant transport in different scenarios of land reclamation

Using the numerical model GMS, in this paper we analyzed the impacts of three reclamation scenarios on groundwater flow field and contaminant transport in the Gulei Peninsula. The three designated reclamation scenarios were sand reclamation (Scenario 1), clay + sand reclamation (Scenario 2), and clay reclamation (Scenario 3). The results showed that (1) There was a regional increase of water table up to 4.78 m after reclamation. The extent of increase from small to large was as follows: Scenario 1, Scenario 2, and Scenario 3. (2) The groundwater flow field difference between different scenarios was the most prominent in the clay region. The maximum difference of water table between Scenario 2 and Scenario 1 was 4.44 m, and that between Scenario 3 and Scenario 1 was 8.20 m. (3) When only the physical interaction was considered, the horizontal contaminant transport was more prominent than the vertical transport in all the three scenarios. (4) Compared with the case of Scenarios 1 and 2, which had basically the same contaminant transport intensity, for the predicted duration of 30a, the contaminant transport area and speed in Scenario 3 respectively decreased by 23.07% and 18.89% in the horizontal direction; in the vertical direction, the contaminant mainly accumulated in the first layer. The concentration of contaminants in the first layer in Scenario 3 was 5.87 times of that in Scenario 1 (or Scenario 2). This indicates that reclamation with low-permeability clay have a certain retardation effect on contaminant transport.