Abstract: High-fill culverts placed in valley topography have a complex earth pressure distribution law due to their locations around culverts in various valley topography conditions. In order to investigate the influence of valley topography on the earth pressure around the culvert of high-fill arch culverts, a interaction model of "topography-culvert-fill" was established by using centrifugal model test and numerical simulation method. Additionally, the distribution laws of earth pressure around the arch culverts and earth pressure concentration coefficient K_s at the top of the culvert under different valley widths B and valley slopes a were analyzed and were compared with the latest Chinese culvert design code. Furthermore, the mechanism of earth pressure formation of high-fill arch culverts under valley topography was presented. The research findings are as follows: (1) The influence of the valley width B on the earth pressure concentration coefficient K_s at the top of the culvert is significant, and the increment of the earth pressure concentration coefficient K_s at the top of the culvert is larger when B is 4D−6D（D is the clear span of arch culvert）. (2) When B is less than 4D, the topography would play the role of load reduction to the culvert. (3) With valley slopes ranging from 45° to 60°, the earth pressure at the tops and K_s would be affected dramatically. (4) When fill height is 20 m with a >70°, K_s≤1; and when 40 m fill height with a >50°, K_s≤1. (5) The K_s recommended by the latest Chinese culvert design code differs to some extent from those by centrifugal model test and numerical simulation. In the case of a =45° with a small B value, the earth pressure concentration coefficient K_s at the top of a culvert of the code is more conservative. (6) K_s of high-fill arch culvert in valley is related to the formation of arch top compaction area and isobaric surface. The arch top compaction area can cause the earth pressure concentration on the top of the arch culvert, and cause the vertical earth pressure of the soil around the compaction area to be arched. At a certain depth approaching the surface of the fill, the arch distribution gradually transits to the horizontal distribution, thus forming an isobaric surface. The upper load of the isobaric surface will be dispersed on the valley slope, so the unloading effect of the valley topography can be exerted.

Key words: high-fill arch culvert, valley width, valley slope, earth pressure around the culvert, loading mechanism