以砂箱試驗探討植生滯留槽二維滲漏流況及提升其效益的方法

為提升植生滯留槽各層之運用效益，本研究透過觀察渠槽砂箱中水體垂直二維滲漏流況，生長介質層之濕峰並非均勻向下移動，且乾燥區塊需花費較長時間才能達到濕潤，為土內空氣壓力累增所抵擋；水洗砂層之滲漏型態為指狀流，無法使水洗砂層所有空間均勻被利用，針對以上兩點觀察到的現象進行改善。首先針對生長介質層內提出排氣法使土壤孔隙中氣體排出以提升水體之入滲率，以土壤入滲深度與時間作圖比對不同方案之效益；再者於水洗砂層提出增加水力停留時間的方法，以提升生物膜與水體的接觸機會，藉由多層複合材料（MSL）為構想所使用交錯型不織布作隔層以比較水力停留時間的差異。實驗使用烘乾後之材料且流量採用定水頭的方式並針對每件改善方案做三次實驗取平均以提供參考依據。由實驗結果可知，土壤空隙並非完全相通，透過排氣管提升生長介質層入滲率，以增加管壁孔洞數量之效益為佳；針對指狀流的不可避免現象，透過增設交錯型不織布隔層可有效提升水洗砂層之水力停留時間藉此增加水體與顆粒接觸之機會。

關鍵字

植生滯留槽；入滲率；垂直滲漏；指狀流；水力停留時間

並列摘要

In order to improve the utilization efficiency of each layer of the bio-retention cells, this study, observes the vertical two-dimensional seepage flow of the water body in a flume filled with sand and soil, the water saturation of the soil layer does not move down uniformly, and it takes a long time for the dry block to get wet, caused by the accumulation of air pressure in the soil; The seepage pattern of the sand layer is fingering flow which cannot make all the space of the sand layer be used evenly. Improvements were made to the phenomena observed in the above by two ways. Firstly, a vantilation method was proposed for the sand layer to discharge the air in the soil pores to improve the infiltration rate of the water body, and the benefits of different schemes are compared by plotting the soil infiltration depth and time. Secondly, a method of increasing the hydraulic retention time was proposed in the sand layer to improve the contact opportunity between the biofilm and the water body. The multi-soil layering (MSL) concept was adopted by using a staggered geotextile as an interlayer and the difference in hydraulic retention time was compared. The experiments use dried soil/sand material and the flow rate was controlled by the method of constant water head, and for each improvement plan, three experiments were performed and the average was used as a reference. Based on the experimental results, it shows that the soil voids are not well connected. It is better to increase the infiltration rate of the sand layer through vatilation pipes, and better by increasing the number of holes in the pipe wall. In view of the inevitable phenomenon of fingering flow, a staggered geotextile interlayer was added, which can effectively increase the hydraulic retention time of the sand layer, thereby increasing the chance of the water body contacting the particles of media in bio-retention cell.