Force and Deformation of a Shallow Soil-Buried Super-Long Box Culvert during Jacking Construction on a Highway

An example of a project on an oversized box culvert jacked into highway subgrade in Guangdong area was investigated to determine the mechanical behavior of shallow soil-covered super-long box culvert in the jacking construction process. On the basis of 3D finite element simulation, the law for stress-strain change and the effective construction area of the box were studied by considering different lengths and thicknesses and drag reduction versus non-drag reduction of overburden soil. Result shows that under the same working condition, the stress-strain of the roof and bottom plate exhibits an "armchair" change shape with an increase in jacking length, whereas the side wall presents a "trapezoid" shape in the box culvert jacking process. The thickness and characteristics of the covered soil (on top of the box culvert) exert considerable influences on the stress-strain of the box culvert structure. If the covered soil is thick and dense, then the stress-strain of the structure will be high. The pavement (on top of the box culvert) settlement ranges from 7.0-17.1 mm due to the effect of vibrations produced during box culvert jacking construction, and the scope of the disturbed roadbed and road surface is 23-30 m along the jacking direction. The drag reduction effect of the paraffin oil mixture is more effective than that of slurry drag reduction. The research results will play a significant guiding role in the design and construction of similar projects.