多孔隙瀝青混凝土以高孔隙率為設計目標，具有相當之透水性，可有效降低雨天路面積水之可能，並增加路面摩擦性，減少輪胎打滑之可能性；PAC之多孔結構，亦能吸收部份噪音，降低交通引起之噪音。PAC的多孔結構，會受到砂塵堵塞或孔隙閉合之影響，導致透水性能降低。實驗室變水頭(falling-head)與定水頭(constant-head) 試驗所量測之K值具有良好之一致性，利用變水頭試驗量測多點性，可有效評估PAC排水速率之變化，更能瞭解PAC之排水特性。
研究發現，PAC的排水速率不會受到試體厚度或水頭高度改變，而等比例增減，因此無法保持固定的滲透係數K值。利用堵塞與壓實對實驗室透水之影響，探討堵塞與壓實對孔隙率改變之影響，進而評估現地透水之影響權重，實驗發現堵塞會使得KC / KO值降低至0.44，利用吸力原理清除堵塞，可有效回升部份透水性能，KR / KO值可達0.58；不同瀝青抵抗車轍壓實造成之永久變形能力不同，抗車轍能力高黏瀝青最佳，其次改質III型瀝青、AR8000瀝青，車轍變形對三種瀝青之垂直向透水影響並不明顯，但隨著車轍變形量增加，除HA瀝青外，對改質III型與AR8000瀝青之水平向透水皆有明顯降低之現象，其KC / KO值最多可降至0.58，藉由變形量與K值之關係，可建構出永久變形影響鋪面之滲透係數模型。介電量測為一種非破壞性之檢測，藉由電磁波之傳遞與反射，可有效量測鋪面之厚度與密度。以介電量測與實驗方式評估堵塞與壓實造成孔隙改變之關係，建立PAC密度預測模式，並探討介電與K值之關係。

關鍵字：滲透係數、變水頭試驗、介電性質

Porous asphalt concrete is designed with high porosity, with equivalent permeability. It can effectively reduce the possible rain water in the street, and to increase the surface friction, reducing the possibility of wheel slip. PAC can also reduce traffic-induced noise by absorbing noise. Pores will be clogged by sand and reduce porosity, resulting in permeability properties decreasing. Laboratory falling-head test measure K value has a good consistency with constant-head test. Falling-head test can measure K value on different water head, used to assess the drainage rate of PAC, and more understand the drainage characteristic of PAC. Research found, the rate of drainage is not proportional change with the thickness or head height, so K value can not maintain a constant value. Evaluating the effect of clog and compaction in laboratory drainage test, and then assess the in-situ permeability. Results shows KC/KO will decreased to 0.44. Clearing clog by suction will make KC/KO recovered to 0.58. High viscosity asphalt resistance to rutting best, then modify type III asphalt, AR-8000. Rutting has not obvious effect on vertical drainage, but except of HA with increase of rutting deformation, with decrease of permeability. By the relationship between K value and deformation can be constructed out of the pavement permeability model. Dielectric measurement as a kind of non-destructive testing, through the transmission and reflection of electromagnetic waves, which can effectively measure pavement thickness and density. To evaluate the change of pores between clog and deformation by dielectric measurement and experimental methods. Then constructing PAC density prediction model, and assess the relationship between K value and dielectric value.

Key Words: permeability, falling-head test, dielectric value

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