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近年来河道无序采沙对桥梁结构安全带来了很大隐患,针对桥下乱挖乱采河沙情况,以采用摩擦桩基础的某高速公路连接线特大桥梁为研究对象,通过理论分析、数值模拟和现场试验,开展桥下采沙对桥梁承载能力及安全的影响研究。研究结果表明:桥下挖沙导致了桩端土处承载力和单桩承载力显著降低,而对墩柱下沉量、主梁跨中挠度和墩柱弯矩影响较小;试验车辆在桥上行驶时,采沙桥墩墩顶竖向动位移和纵向动位移较未采沙桥墩有所增大,刹车则引起两个方向动位移显著增大,远大于跑车试验数据;过路汽车试验数据远大于试验车数据,过路车超载严重;试验车辆和过路车作用下主梁跨中动挠度变化不明显;车辆重量是影响墩顶竖向位移的主要因素,车辆刹车时的纵向制动力是影响墩顶纵向位移的主要因素;桥上刹车和超载具有较大危害,需尽快采取限速、限重、加固等措施,避免桥上紧急制动和水流冲刷,保证桥梁结构安全。
In recent years, the disorderly sand mining of the river brings great hidden dangers to the structural safety of the bridge. Aiming at the situation of chaos dredging and sand mining under the bridge, a bridge connecting with a highway with friction pile is taken as the research object. Through theoretical analysis, Numerical simulation and field test to study the influence of sand mining on the bearing capacity and safety of the bridge. The results show that: under the bridge dredging, the bearing capacity of the soil at the pile tip and the bearing capacity of the pile are significantly reduced, while the influence on the settlement of the pier, the mid-span deflection of the main girder and the bending moment of the pier is insignificant; The vertical dynamic displacement and longitudinal dynamic displacement of the pier of the sand-mining pier increased compared with that of the un-pumped sand pier, the dynamic displacement caused by the brake in the two directions significantly increased, which was much larger than that of the sports car test data; In the test vehicle data, the overpass vehicle is overloaded severely; the midspan deflection of the main beam under the test vehicle and the overpass vehicle is not obvious; the vehicle weight is the main factor that affects the vertical displacement of the top of the vehicle; the longitudinal braking force when braking the vehicle affects the abutment Top longitudinal displacement of the main factors; brake and overload on the bridge has a greater hazard, as soon as possible to take speed, weight, reinforcement and other measures to avoid emergency braking and water erosion on the bridge to ensure the safety of the bridge structure.