# Experimental Investigation into Permeable Asphalt Pavement Based on Small-Scale Accelerated Testing
## 1 Introduction  
The progression of urbanization has led to an extensive coverage of impermeable surfaces across metropolitan regions [1]. This phenomenon causes diminished infiltration and evaporation capacities, subsequently elevating surface runoff volumes while reducing groundwater replenishment rates [2]. As an eco-friendly stormwater management strategy, permeable pavement mitigates environmental impacts while enhancing vehicular safety and ride quality for motorists and adjacent communities [3, 4]. This pavement system facilitates hydraulic connectivity through surface infiltration and potential subgrade percolation. The base layer functions as a temporary water retention reservoir to attenuate runoff volumes. Since 1970s, the fully permeable pavement had been implemented in numerous U.S. states for low-volume roadways and light-duty vehicle applications. The design prioritizes high void ratios in the surface and base layers to achieve optimal permeability andstormwater storage capacity. However, conventional designs employing minimally compacted subgrade soils frequently exhibit moisture susceptibility and a reduced service life. Alternative configurations utilizing high-strength permeable bases with a reduced porosity may improve structural durability when hydraulic storage functions are deprioritized, though the associated mechanical performance requires comprehensive investigation. Previous studies have identified clogging of the surface layer, raveling, and cracking as primary types of distress of permeable pavement [5]. While laboratory testing remains fundamental for material characterization, such empirical data demonstrate a limited correlation with in-service pavement performance. Accelerated pavement testing (APT) has emerged as a robust methodology for evaluating structural response and distress mechanisms, including rutting, fatigue cracking, and deformation under controlled loading conditions [6; 7; 8; 9; 10]. APT enables the precise simulation of axle load magnitudes and repetition frequencies on constructed pavement sections, facilitating the short-term accumulation of damage equivalent to long-term field performance. Nevertheless, full-scale APT implementations incur substantial capital and operational expenditures. To address this limitation, a down-scale laboratory wheel tracking device, the model mobile load simulator (MMLS), was selected to test the mechanical response and performance of pavement. The model mobile load simulator (MMLS) has been adopted for mechanistic-empirical analysis. The MMLS apparatus, a one-third scale accelerated loading system, accommodates both in situ pavements and laboratory-constructed test sections. [PERSON] [11] demonstrated the efficacy of a scaled APT for performance prediction through a comparative full-scale validation, emphasizing critical scaling factors including loading frequency, pavement layer thickness proportionality, and dimensional similitude requirements. [PERSON] [12] conducted multi-scale APT comparisons, concluding that MMLS provides a cost-effective rutting and fatigue characterization when structural equivalency criteria are maintained. Subsequent investigations have employed scaled APT to analyze tire configuration effects [13], the scale of model pavements [14], and temperature on the performance of pavement [15]. Many studies have pointed out that MMLS3 has the potential to obtain the mechanical responses and performance of pavements in term of fatigue performance, permanent deformation [16; 17; 18; 19], and other properties [20; 21; 22]. While full-scale APT initiatives continue to advance pavement engineering [23], their implementation remains cost-prohibitive for routine testing. Current MMLS3 applications predominantly focus on porous asphalt material characterization rather than holistic structural evaluation [24]. Numerical modeling approaches employing finite element analysis (FEA) and discrete element methods (DEMs) have supplemented experimental permeable pavement research [25; 26; 27; 28].