In the collapsible loess of Midwest China, quicklime compaction pile composite foundation has been widely used in practical engineering. Firstly，the calculation method of quicklime compaction pile composite foundation is analyzed; then the influencing factors of bearing capacity for quicklime compaction pile composite foundation was researched on the basis of the character about soil compaction effect between piles with the quicklime expanding when absorbing water from the soil; lastly, the calculation method was used in practical engineering, the results can be used to reference in reliability design application of composite foundation.

The Zr2Al4C5 ceramic was successfully fabricated by the spark plasma sintering at 1800 °C for 10 min under uniaxial 20 MPa pressure in vacuum using a mixed raw materials of Zr, Al, Si and graphite powders. The X-ray diffraction analysis results showed that the unexpected Zr2Al3C5 phase rather than target compound Zr2Al4C5 formed in the sintered samples. An initial Zr:Al:C molar ratio of 2:4.2:4.8 for raw powders, and even 55 mol.% excess Al, did not lead to a phase transformation from Zr2Al3C5 to Zr2Al4C5. When 4 wt.% Si was induced in the starting powders, the major phase became Zr2Al4C5 and no obvious Zr2Al3C5 was detected in the sintered samples with an initial Zr:Al:C molar ratio of 2:6.2:4.8 (55 mol.% excess Al). The introduction of Si could suppress and even remove additional ZrC, and Si atoms would exclusively occupy the site of Al to make Zr2Al4C5 become a stable solid solution. The scanning electron microscopy observation showed that the as-synthesized Zr2Al4C5 grains had elongated, rod-like and/or plate-like shapes. The mechanical properties of the sintered Zr2Al4C5 ceramic were also investigated, and it showed a hardness of 11.06±0.34 GPa and a fracture toughness of 4.6 ± 0.4 MPa×m1/2.