水下工程勘探对已建水库水体质量及库底渗流场影响研究

Study on the impact of underwater engineering exploration on the water quality of existing reservoirs and the seepage field at the reservoir bottom

【目的】工程勘探对需在复杂水下环境中进行施工的工程是必不可少的,但在重点水源地区对施工造成的水源及渗流影响有严格控制,需针对工程勘探对水库水体质量及库底渗流场造成的影响进行分析。【方法】通过对勘探前后水体中的pH值、化学需氧量、氨氮及悬浮物等指标进行化学分析,研究了水库钻探对水库水源质量的影响;通过数值分析研究了不同勘探工况对库底渗流场的影响。【结果】结果显示:勘探过程中水体pH值最大值未超过8.30,化学需氧量基本未超20 mg/L,氨氮施工前后变化量为0.04 mg/L,悬浮物变化幅度为10 mg/L;孔底处渗流量和渗流速率增大了10倍,影响变化值为1×10^(-8);夹层会影响其下5 m范围内土层。【结论】结果表明:勘察期间水库水质相关监测指标在施工过程中未出现较大变化,符合相关规范中水质标准,未对水库水体造成显著影响。渗透影响集中在成孔后阶段,施工前后变化表明勘探孔会对场地渗流场产生一定影响,但因初始值较小,不会威胁库底防渗性能;夹层透水性越强,对地层渗流影响越大;封孔材料效果优异,能满足库底防渗要求。针对水下工程勘探的影响程度与范围的研究分析,可为类似需进行水下勘探的工程提供参考。

[Objective]Engineering exploration is essential for construction projects that need to be carried out in complex underwater environments.However,strict control over the impact of construction on water sources and seepage in key water source areas is necessary.This paper aims to analyze the effects of engineering exploration on the water quality of reservoirs and the seepage field at the reservoir bottom.[Methods]Chemical analysis of pH value,chemical oxygen demand,ammonia nitrogen,and suspended solids in the water before and after exploration was conducted to study the impact of reservoir drilling on the water quality of the reservoir.Numerical analysis was used to study the effects of different exploration conditions on the seepage field at the reservoir bottom.[Results]The result showed that the maximum pH value of the water during exploration did not exceed 8.30,and the chemical oxygen demand did not exceed 20 mg/L.The change in ammonia nitrogen before and after construction was 0.04 mg/L,and the variation in suspended solids was 10 mg/L.The seepage flux and seepage rate at the bottom of the hole increased by 10 times,with a variation value of 1×10~(-8).Intercalated layers affected the surrounding soil within a range of 5 m below them.[Conclusion]The result indicate that there were no significant changes in the monitored water quality indicators during the exploration period,and they complied with the relevant water quality standards,thus having no significant impact on the water quality of the reservoir.The seepage effects were mainly concentrated in the post-drilling stage,and the changes before and after construction indicated that exploration holes would have a certain impact on the seepage field,but the initial values were small and did not threaten the anti-seepage performance of the reservoir bottom.The permeability of intercalated layers had a greater impact on the seepage of the formations.The sealing materials showed excellent performance and met the requirements for preventing seepage at the reservoir bottom.This paper conducts a research analysis on the degree and scope of the impact of under water engineering exploration,providing references for future engineering projects that require underwater exploration.