基于区域和工程稳定性的绿汁江大桥选址方案论证研究

Study on site selection of Lüzhijiang bridge based on region and engineering stability

桥梁是跨越河流沟谷的重要交通工程之一,桥址边坡的稳定性决定了坐落其上的桥梁建构筑物的安全性,是桥梁选址的重要依据。以弥楚高速公路绿汁江大桥选址为研究对象,根据区域构造、地层岩性和不良地质现象等对桥位的不利影响,定性评估了B4和B6桥位的可行性;根据工程稳定性,定量评估了2个桥位的优劣,所得主要结论如下:1)平推断层在B6桥位楚雄岸附近的折冲转向容易造成该区应力集中、内部岩体破碎,对B4桥位楚雄岸的影响较小,区域稳定性评价支持B4桥位;2)根据自然边坡安全系数1.35划定的满足工程稳定性的区域,无治理措施条件下,对于B6桥位玉溪岸主塔需要后移103 m;楚雄岸支墩需要后移112 m。B4桥位玉溪岸主塔主塔需要后移117 m;楚雄岸支墩无需后移。满足稳定性要求的主跨,B4桥位819 m,B6桥位1 350 m,B4桥位方案在区域稳定性、工程稳定性和经济性方面均优于B6桥位方案。

A bridge is important in traffic engineering for spanning river or gully. The stability of a bridge bank slope determines the safety of bridge buildings that locate on them, which is a key basis for bridge site selection. Site selection of Lüzhijiang bridge in Michu highway is studied. According to the disadvantages for bridge site done by regional tectonic,formation lithology and bad geological phenomenon, the feasibility of B4 and B6 site is qualitatively estimated. According to the engineering stability, two bridge sites are quantitatively compared. Main conclusions are listed as follows:(1)Turning of flat-push fault near B6 Chuxiong side is easy to cause stress concentration and inner rock mass crushing in the region, the fault does little harm to B4 Chuxiong side, the regional stability estimation supports B4 bridge site.(2) Region meeting to engineering stability is drawn by safety factor being 1.35 of natural slope without reinforcement measures. The distance between main tower of B6 bridge site Yuxi side tower should be moved back 103 m. that of Chuxiong side buttress should be moved back 112 m. The distance between main tower of B4 bridge site Yuxi side tower should be moved back 117 m. that of Chuxiong side buttress need not be moved. B4 bridge site with 819 m span is better than B6 site with 1 350 m span in regional stability, engineering stability and economy.