丹江口库区郧县汉江二桥嵌岩桩基岩承载力特性试验研究

Bedrock Bearing Capacity of Rock-Socketed Piles of Second Hanjiang Bridge in Yun County in Danjiangkou Reservoir Region

丹江口库区郧县汉江二桥地基为白垩系至下第三系的一组软岩和极软岩,具有胶结较差易扰动的特点,桥梁基础为嵌岩钻孔灌注桩,在详勘阶段进行了岩块物理力学性质试验和现场岩体力学试验,其中采用的桩侧摩阻力试验为岩体力学试验的新方法。通过现场试验研究基岩荷载与沉降变形的关系,得出桩端阻力和桩侧摩阻力的容许值,弥补了室内岩石试验的局限性,提出了桩端阻力及桩侧摩阻力参数建议值,为工程优化设计提供了依据。

Rock mass of the foundation of the Second Hanjiang Bridge in Yun County consists of soft rock and extremely soft rock which are formed from Cretaceous Period to Paleogene Period.The cementation is unfavourable and they are easily degraded under disturbance.The foundation of the bridge is bored-pile socketed in rock.Laboratory physical and mechanical tests on rock samples as well as in-situ mechanical tests on the rock mass were carried out in the detailed prospecting stage.Of the adopted test methods for the mechanical properties of rock mass,the method for the test of lateral frictional resistance force of pile is a newly proposed one.The correlation between bedrock load and settlement deformation was investigated based on in-situ tests.Permissible values of resistance force at the end of pile and lateral frictional resistance force of the pile were both obtained,hence the limitations of laboratory tests were overcome.Suggested values of the resistance force at the end of pile and the lateral frictional force were proposed and therefore the optimization design is provided with reliable basis.