TESTING STUDY ON REINFORCING SOFT FOUNDATION OF HIGHWAY BRIDGE-HEAD BY VACUUM COMBINED WITH SURCHARGE PRELOADING
高等级公路桥头软基真空联合堆载预压加固试验研究

The observation results of the Jialichen bridge-head experiment site such as pore water pressure, settlement of soil at various depths,surface settlement,and horizontal displacement are analyzed. The results show that the combined excessive pore water pressure in the soft ground is relatively small,usually less than zero,which is produced by negative excessive pore water pressure and positive excessive pore water pressure through the process of vacuum combined with surcharge preloading,so that it is advantageous for rapid embankment construction. The results also show that the settlement can be eliminated greatly;and settlement after completion of construction is less than 100 mm,meeting the requirement of bridge-head soft ground. The soil horizontal displacement is little in the influence area 20 m away from the improvement area border. The effect of soil improvement is evaluated;and the result shows that the effective influence depth of vacuum preloading can be deeper than 10 m. The improvement effect is checked;and the results show that the strength of soil in the improvement area is improved obviously;and the soft foundation treated by vacuum combined with surcharge preloading is very effective. Combined with the observation results,the mechanism of vacuum combined with surcharge preloading is analyzed;and the superimposed stress distribution diagram is given.