沉井基础设置根键及压浆后处理原位试验分析

Analysis on the Caisson Foundation Compared with Setting Root Keys and Post Grouting In-situ Test

研究设置根键及注浆对沉井基础承载特性的影响,采用自平衡原位试验的方法对某一沉井基础设置根键前后及压浆处理进行现场测试与分析。整个测试过程分普通沉井承载力测试、顶入根键后承载力测试、压浆后测试3个阶段进行。根据测试结果,分析了沉井基础在3种不同情况下的荷载与位移关系曲线(Q-s)、轴力的分布情况及侧摩阻力分布规律。研究结果表明:沉井基础在设置根键的情况下,通过根键的挤密、叠加及扩散作用,大大改善了沉井基础与土体的相互作用,使得沉井基础承载能力得到极大提高,提高幅度达到50%,且通过井壁后压浆处理可进一步提高其承载能力;从承载力的分担比例来看,根键的设置使得沉井基础的侧摩阻力所占比重明显增大。与普通沉井相比,设置根键后,沉井基础的侧摩阻力占总的极限承载力的比例提高了28.7%,通过后压浆的处理可进一步增加4%;从轴力分布的规律来看,设置根键及后压浆处理的沉井,两者轴力分布曲线都较为平缓,这对发挥沉井基础材料本身力学性能较为有利,达到了充分利用材料的目的。

To research the influence of setting root keys and grouting on the bearing characteristics of caisson foundation,the caisson foundation with root keys and grouting was tested and analyzed by using the Self-Balanced Test method. The whole bearing capacity test was divided into three stages: common caisson test,setting root keys caisson test,post grouting caisson with root keys test. Based on the test results,the load and displacement relation curves(Q-s),the distribution of axial force and side friction resistance of caisson foundation were analyzed under the different conditions. The result shows that,because of the compaction,superposition and diffusion of the root key,the interaction between the caisson foundation and the soil is greatly improved in the case of setting the root key,and the bearing capacity has been greatly improved to 50%,and the bearing capacity can be further improved by post grouting treatment. From the view of the sharing of the bearing capacity,the root key makes the proportion of side friction resistance increase obviously in caisson foundation. Compared with the common caisson,the ratio of the side friction to the ultimate bearing capacity with root keys is about 28.7%,which is higher than that of the conventional caisson.The treatment of grouting can be further increased by 4%. According to the principle of axial force distribution,the axial force distribution curve is both relatively smooth in caisson with the root key and the post grouting. It is beneficial to the performance of the foundation itself,which can make full use of the material of caisson.