定性与定量相结合的李仙江大桥大里程岸边坡稳定性评价

Qualitative and Quantitative Stability Evaluation of Bank Slopes Near Lixianjiang River Crossing Bridge

拟建的李仙江大桥大里程岸坡问题相对突出,利用工程地质方法定性评价了该岸边坡的整体稳定性,在此基础上,利用极限平衡法计算评价了初始地形和开挖改变地形条件下该侧岸坡整体和局部(主塔上边坡和下边坡)稳定性。结果表明:①依据现场定性分析,大里程岸整体稳定,局部可见坍塌滑移;②自然地形下,边坡整体满足工程稳定,仅浅表层不满足工程稳定性要求。③改变地形下,主塔上部边坡部分前表层不满足工程稳定性。下边坡满足工程稳定性。④针对改变地形后的开挖边坡,建议坡面采取3 m×3 m,长度30 m的锚杆(索)不小于15排,锚固段深入强风化基岩不小于10 m。该大桥的桥址选址是适宜的,在采取工程措施加固的基础上可满足桥梁建设需要。

The slope stability of riverbanks at the propose Lixianjiang River Crossing Bridge was a concern. The global stability of the entire riverbanks was first evaluated using the engineering geology method. The stabilities of both the entire and local slopes(main tower upper and lower slopes) of both side of the riverbanks were evaluated and analyzed under both initial conditions and constructed conditions. The following conclusions can be obtained: 1) Based on the qualitative evaluation of the site conditions, it is concluded that the global stability of the Dalicheng riverbanks could be warranted and the local collapses and instabilities could be occurred. 2) under the natural conditions, the global stability of both riverbanks was satisfactory and the shallow slides that could not meet the engineering requirements and need to be improved. 3) under the constructed conditions the upper slope at the main tower had surficial stability concern and the lower slope was stable globally and locally. 4) for the excavated slope after changing the topography, it was suggested that the riverbank slope could be stabilized using ground anchors with 3 m(vertically)×3 m(horizontally) pattern with the anchor length of 30 m and no less than 15 rows. It is important the ground anchor grouted length should be imbedded into the strong weathered bedrock with no less than 10 meters deep. Based on the above evaluations, it is also concluded that the selection of the bridge site was appropriate and the minor stability concerns could be mitigated throughout the engineering stabilization methods.