土体支承刚度对下沉期沉井内力的影响分析

Effect of supporting soil stiffness on internal force of caisson during sinking

为了确保大型沉井下沉期间的本体结构安全,对各种不利工况下沉井的弯矩内力进行了分析.以马鞍山长江公路大桥南锚碇沉井为例,将刃脚和内部隔墙下方土体支承模拟为文克尔地基上的弹簧支座,采用SAP2000程序计算周边井壁和内部隔墙的弯矩分布,并与实测数据进行了对比.分析和实测结果表明:相比大锅底开挖,分区开挖可显著降低内部隔墙弯矩峰值;在分区开挖工况下,刃脚和隔墙处的支承刚度比显著影响沉井结构的弯矩分布和大小,其内部隔墙下土体实际支承刚度有限且分布不均.工程设计时应以大锅底工况计算隔墙底部弯矩,分区开挖时应取刃脚初始支承刚度的50%来计算隔墙顶部弯矩.

In order to ensure the safety of the large-scale caisson structure in the process of sinking, the bending moment and the internal force of the caisson under harsh conditions are analyzed. The south anchorage caisson of the Ma＇anshan Yangtze Highway Bridge is taken as an example. The sup- porting soil below the cutting edge and the internal partition walls are simulated as spring supports on Winkler foundation, and the SAP2000 program is used to calculate the bending moment distribution of the surrounding walls and the internal partition walls. The computation results are compared with the measured data. The analysis and measurement results show that compared with large span excava- tion, partition excavation can significantly reduce the maximum bending moment of the internal par- tition wall. In the case of partition excavation, the supporting stiffness ratio of soil under the cutting edge feet and partition wall significantly influences the distribution and the value of the bending mo- ment within the caisson structure. The actual supporting stiffness of soil under the internal partition wall is limited and unevenly distributed. In engineering design, the moment of the bottom bending of the partition wall should be calculated on the condition of large span excavation. 50% of the initial supporting stiffness of the cutting edge should be used to calculate the top part of the partition wall in the case of partition excavation.