大跨度多孔箱涵顶进时底板内力研究

Study on Internal Force of Bottom Plate in Jacking Construction of Large Span Porous Box Culvert

在大跨度多孔箱涵的长距离顶进过程中,由于箱涵跨度大,顶推用千斤顶数量多,作用于箱涵上的面积宽,若对千斤顶顶力分配控制不当很容易导致箱涵整体受力不均,同时引起箱涵的偏移与转动。论文依托北京大礼路箱涵顶进工程,基于大跨度箱涵顶进时底板钢筋内力实时监测数据,对箱涵底板在顶进时所受内力进行研究,为实现大跨度箱涵实时智能顶力控制提供理论依据与现实参考。研究结果表明:顶进全程箱涵底板混凝土压应力变化峰值在3.5MPa以下,小于混凝土的抗压极限,顶进过程不会对涵体结构造成影响,但同时底板存在左右两侧受力不均的现象。箱涵底板应力不均现象在一定程度上影响了箱涵姿态控制,因此,在工程施工中,应结合箱涵姿态、纠偏策略等因素进行顶力合理配置,将左右顶力保持相对均衡,避免发生较大的顶力波动以及顶力浪费。

In the long-distance jacking process of large-span porous box culverts,due to the large span of box culverts,the number of jacks used for jacking and the wide area acting on the box culverts,if the distribution of jacking force is not properly controlled,it is easy to lead to uneven overall force of the box culverts,and at the same time cause the deviation and rotation of the box culverts.Based on the box culvert jacking project in Beijing Dali Road and the real-time monitoring data of the floor reinforcement internal forces during the jacking of the large-span box culvert,this paper studies the internal forces received by the box culvert floor during the jacking,providing theoretical basis and practical reference for the realization of real-time intelligent jacking control of large-span box culvert.The results show that the peak value of the compressive stress change of the floor concrete of the box culvert during the whole jacking process is below 3.5 MPa,which is less than the compressive limit of the concrete.The jacking process will not affect the structure of the culvert body,but at the same time,there is the phenomenon of uneven stress on the left and right sides of the floor.The uneven stress in the bottom floor of the box culvert affects the attitude control of the box culvert to a certain extent.Therefore,in the construction of the project,the jacking force should be rationally allocated by combining the attitude of the box culvert and the deviation correction strategy,so as to keep the left and right jacking forces relatively balanced and avoid the occurrence of large jacking force fluctuation and the waste of jacking force.