Method for Determining Road Comprehensive Bearing Capacity Based on the Cavity Diameter-to-Depth Ratio

Abstract

The leakage of drainage pipes is the primary cause of underground cavity formation, and the cavity diameter-to-depth ratio significantly affects the overall stability of roads. However, studies on the quantitative calculation for road comprehensive bearing capacity considering the cavity diameter-to-depth ratio have not been extensively explored. This study employed physical model tests to examine the influence of the cavity diameter-to-depth ratio on road collapse and soil erosion characteristics. Based on limit analysis theorems, a mechanical model between the road comprehensive bearing capacity and the cavity diameter-to-depth ratio (FB–L model) was established, and damage parameters of the pavement and soil layers were introduced to modify the FB–L model. The effectiveness of the FB–L model was validated by the data derived from eight physical model tests, with an average deviation of 14.0%. The results indicate a nonlinear increase in both the maximum diameter and fracture thickness of the collapse pit as the cavity diameter-to-depth ratio increased. The pavement and soil layers adjusted the diameter and fracture thickness of the collapse pit to maintain their load-bearing capacity when the cavity diameter-to-depth ratio changed. The fluid erosion range increased continuously with increasing depth of buried soil and was influenced predominantly by gravity and seepage duration. Conversely, the cavity diameter decreased as the buried depth increased, which is associated with the rheological repose angle of the soil. Furthermore, the damage parameters of the pavement and soil layers decrease as the distance from the collapse pit diminishes, with the pavement exhibiting more severe damage than the soil layer. This study provides a theoretical basis for preventing road collapses. Soil cavity expansion results in a progressive degradation of the load-bearing capacity of the pavement and soil layers. When the sum of the traffic load and gravity surpasses the sum of the pavement bearing capacity and soil bearing capacity, the potential for catastrophic road collapses heightens significantly. Establishing a quantitative correlation between the dimensions of the soil cavity and the load-bearing capacity of the pavement and soil layers is essential. Furthermore, advancements in ground-penetrating radar technology have facilitated the rapid and precise determination of cavity dimensions, thereby enabling the expedited assessment of the load-bearing capacity of the pavement and soil layers based on the dimensions of the soil cavity. Consequently, an equation for ascertaining the load-bearing capacity of the pavement and soil layers according to cavity size parameters was proposed. This equation can be integrated into road safety management system platforms, serving as an effective early warning information for potential road collapses.