关键词: 随钻跟管桩, 钻孔卸荷, 后注浆, 挤土效应, 足尺寸原位试验

Abstract: To overcome the squeezing effect of pipe pile construction, a drilling with a prestressed concrete (DPC) pipe pile with drilling into hole, synchronous sinking pile and post-grouting was developed. It was a type of the rock-socketed and non-squeezed pipe pile. In this paper, the deformation and pressure change in the soil around the pile, caused by the drilling unloading and side post-grouting, were tested by in-situ tests. Based on test results, the change rules of unloading and grouting effects along the horizontal and vertical directions were analyzed, revealing the disturbances of soil around the pile. Moreover, a method for estimating the disturbances of DPC pipe pile construction was developed based on the circular hole shrinkage theory. The study shows that the disturbances mainly manifests unloading and grouting effects. Drilling unloading causes a shrinkage of the hole wall of 3.5−18.9 mm, and subsequent pile side post-grouting restore the shrinkage deformation by 28% to 50%, partially eliminating the impact of drilling unloading effect. In addition, the deformation and pressure change of soil around the pile caused by drilling unloading can be estimated by the modified circular hole shrinkage theory. Compared with the squeezing effect of displacement piles, the unloading effect of DPC pipe piles is significantly smaller, more advantages in application in urban areas with dense buildings and pipelines.

Key words: DPC pipe piles, drilling unloading, post grouting, squeeze effect, full-size in-situ test