Research On Behavior And The Determination Method Of Bearing Capacity Of 2D Composite Ground

When method of Dry Jet Mixing(DJM) column and drainage consolidation were organically combinated, the lateral pressure produced during DJM column installation could be motivity of pore water's exclusion, the strength of soft clay surrounding column were increased under drainage consolidation, and the bearing capacity of DJM composite ground could be inceased effectilvely, thus a new technique of composite ground formed as 2D(Drained DJM) method. However, being unmature in theory with highly complexity and limited in practice, the appiled reasearch has important fulfillment meaning.In this dissertation, the applicability and superiority of 2D method were verified on test, and (1)the practical construction effects on the surrounding soil during DJM column or 2D column installation, (2)comparing analyses of 2D column and DJM column, (3)the bearing capacity of soil between 2D column, (4)characteristic of 2D composite ground and the determination method of bearing capacity were studied, the main contents are as follows:Based on the sampling experiments and the field test, the soil strength change mechanisms and the excess pore water pressure change mechanisms during DJM column installation and after installation were considered, the influnce range during 2D column installation and after installation was studied. The results of test show that, the soil's module surrounding DJM column was not obviousle improved, but the soil's strength improved obviously surrounding 2D column and the improvement mainly displayed in the soft clay layer. Excess pore water pressure inceased during DJM column installation and disppeared after DJM column installation, it differs with the distance from column and depth. The pore water pressure of the soil surrounding 2D column increased more evidently, the time it reached maximum and the dissipation time became shorter, which is advantageous to increase the degree of soil consolidation and shorten the consolidation time. The influence radius during DJM column installation was less than 16 times column radius and the dissipation time is about two days; the influence range of 2D column can reach 4 meters and the maximum dissipation time is no more than 2 days. Based on field loading test, the determination method of 2D composite ground and the determination method of bearing capacity of single column and soil between column were stuided, the experiential formula and esitimate method of sigle column's bearing capacity were statistically obtained.