Abstract: In this paper, two loading methods of surcharge preloading (overload ratio 1.14) and permanent pressure loading are used to carry out in -situ tests on large -area deep soft soil foundation treatment at an airport in Hubei province. By analyzing the data of settlement and pore water pressure monitoring, the change law of soil consolidation degree and the development of horizontal displacement rate of the two loading schemes are summarized, and the post construction settlement is predicted by the hyperbolic method. The test results show that the consolidation degree of most soft soil foundations can reach more than 90% after 120 days of stack-load preloading. The foundation consolidation degree of the surcharge preloading is 3.39% higher than that of the permanent pressure loading in test section. The average predicted post construction settlement of surcharge preloading is 25.59 mm, and the average predicted post construction settlement of permanent pressure preloading is 74.11 mm, both of which can meet the design requirements of post construction settlement. In the two forms of preloading process, the maximum value of the horizontal displacement rate of deep soft soil is 1.65 mm/d, which is lower than the standard value of 5 mm/d. The above conclusions can provide a basis for the subsequent construction of the project and a reference for similar projects.

Key words: foundation treatment, stack-load preloading, soft soil treatment, consolidation degree, pore water pressure