Compression Behavior on Precast Concrete Assembly Spread Foundation for Qinghai-Tibet AC/DC Grid Interconnection Project

The precast concrete assembly foundation for Qinghai-Tibet AC750kV/DC±400kV grid interconnection project in frozen soil area was tested under compression load. The mechanical co-working properties for the different parts of the foundation were analyzed based on the observed results of soil pressure, structural displacement and stress. Under compression load, the displacement of the ring flange connecting the column, the bottom slab, and the joint seam of the two consolidated bottom slabs conformed with that of the top plane of the foundation. Two stages of elastic and elastic-plasticity were observed according to load-displacement curves of the foundation. The stress of the channel beams increased with the compression load and was in elastic stress condition. Under compression load, the two edges which were parallel to the joint seam of two consolidated foundation slabs had a tendency to up warping. But the displacements of all angular measuring points were less than that of the foundation top plane. The displacement and the stress of the different connected parts redistributed until the new balance developed. As a result, the different connected parts of the precast concrete assembly foundation co-operated to carry the compression load. The structural characteristic of the assembly foundation, the gaps among the assembly parts, the discrepancy of the nut screwing up and the mismatching tolerance during consolidating were the key factors to determine the performance of the foundation. Generally, under compression load, all structural parts of precast concrete assembly foundation had good entirety.