公轨双层高架中道路桥梁形式对轨道噪声分布影响研究

高架独立轨道交通具有建设、运营成本低的优势，但其对周边居民产生的环境噪声污染问题突出，道路与轨道双层合建高架的上层道路桥梁可起到屏蔽作用，减小由轨道交通引起的道路上部区域噪声。为分析不同道路桥梁形式对轨道噪声传播规律的影响，根据实测钢轨振动加速度，建立二维声学模型进行轨道噪声传播规律预测研究。首先采用现场噪声实测结果验证方法的准确性，然后对比分析独立双U梁轨道、空心板梁道路桥+双U梁轨道、小箱梁道路桥+双U梁轨道的噪声传播与分布规律，揭示双层高架桥梁的降噪机理。结果表明，上层道路桥改变了噪声的传播途径，在增大桥下噪声的同时可以使得一部分区域(道路桥侧上方)的噪声减小；进而，在道路以上区域，小箱梁道路桥+双U梁轨道形式相比空心板梁道路桥+双U梁轨道显著降低了噪声级，大部分降幅在6～11 dB(A)之间，最大降幅约21 dB(A)；与空心板梁结构形式相比，底面凹凸不平的小箱梁结构能将声能量更好地限制在道路桥梁以下范围内，从而对道路上方区域取得更大的降噪效果。提出的噪声预测方法可为公轨合建双层高架的轨道噪声快速预测与评估提供参考，计算结果可为双层高架的道路桥梁选型提供声学性能依据。

Spatial Noise Distribution of Double-deck Rail-cum-road Viaduct with Different Road Bridge Types

ndependent rail transit viaducts have the advantages of low construction and operation costs, but they produce significant environmental noise pollution that affects nearby residents. However, the upper road bridge of the double-deck rail-cum-road viaduct can act as a barrier to reduce the upper-zone noise originating from rail transit traffic. To analyze the spatial noise distribution of a double-deck rail-cum-road viaduct with different road bridge types, a two-dimensional acoustic model was established to predict the track noise propagation characteristics based on the measured rail vibration acceleration. First, the accuracy of the proposed method was verified using field noise measurement results. Second, the noise propagation and distribution characteristics of the independent rail transit double U-beam viaduct and the double-deck rail-cum-road viaduct constructed with small box girders and hollow slab beams were compared. Finally, the noise mitigation mechanism of the double-deck viaduct was determined. The results show that the upper road bridge changes the transmission path of noise, which can reduce the noise in some areas (above the road bridge side), while increasing the noise under the bridge. Meanwhile, the noise under the road bridge significantly increases owing to the reflection of sound by the road bridge. Additionally, in the area above the road, the small box girders significantly reduced the noise level compared to the hollow slab girders, with a general decrease between 6 and 11 dB (A), and the maximum decrease was approximately 21 dB (A). A small box beam with an uneven bottom can limit the acoustic energy within the zone below the road bridge and achieve a greater noise-reduction effect in the area above the road. The proposed noise prediction method can provide a reference for prediction of the noise from the rail track of a double-deck rail-cum-road viaduct. The calculation results can provide an acoustic performance basis for selecting the type of road bridge for the double-deck viaduct.