為了推動「海綿城市」建設將雨水吸收並儲存於鋪面或道路之下，其主要應用於人行道與停車場，此建設工法近年來漸漸受到政府的重視。雖然此方法對於環境永續發展有很大的幫助，但對於道路維管單位卻是個麻煩的問題，由於透水鋪面下儲水，可能會因路基土壤泡水軟化，導致路基土壤承載力降低。有鑑於此，本研究提出就現有透氣道路之路基土壤剖面設計加以改良，利用黏土質礫石層結合矽酸膠砂層形成阻水層，將透水路面下方之儲水層與路基土壤予以隔開，使其不會因為鋪面下儲水而導致基底土壤承載力降低；同時導入透水側溝設計，以維持透水鋪面滋潤大地之功能。本研究經由小型室內模型試驗，量測底層土壤強度與含水量變化。經試驗結果發現，黏土質礫石層結合矽酸膠砂層形成阻水層可以有效阻止水滲入基底土壤，黏土質礫石層則可用來保護下方的矽酸膠砂層，期待未來此透水透氣且保水之設計能用於一般車行道路下，並達到改善微氣候之功能。

To build a sponge city which can absorb and keep the rain water under the pavements of roads, pedestrian walks, parking lots has been recently gaining more and more attention to the public and the government as well. Although this is a good idea for the sustainability of the environment, it may be a bad idea for the road maintenance department. Because the water preserved in the water storage space under the porous pavement may soften the base soil and weaken the bearing capacity of subgrade. This study proposes a modified road base design for the porous pavement. It uses a water barrier under the water storage gravel layer. This design also integrates the porous pavement with the perforated side ditches. It can not only keep the water storage capacity beneath the porous pavement but also maintain the infiltration ability of water to moisture the base soil without jeopardizing the bearing capacity of the road. Laboratory tests were adopted to study the changes on moisture content and strength properties of the base soil. The test results showed that the water barrier formed by a layer of colloidal silica sand could stop the water infiltration to the base soil and prevent any softening effect of soil due to soaking; a clayey gravel layer is also used to protect the integrity of the underlying colloidal silica sand layer. This road base system can be used with the porous pavement to preserve water under the pavement and to adjust the micro-climate around it.

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