TEST STUDY ON POST BASE-GROUTING BORED PILE SOCKED IN MUDSTONE IN REGARD TO SETTLEMENT REDUCING EFFECT

The settlement difference between widened and spliced bridge-pile and original bridge-pile has a large impact for upper structure, therefore the settlement of new build bridge-pile should be strictly controlled. Post grouting technology could solidify bottom sediment and mud cake around pile, and improve the bearing capacity of pile. However the grouting in mudstone strata has less experience, contrast test was performed in regard to settlement reducing effect between post base-grouting bored pile and non-grouting bored pile socked in mudstone, combined with the expansion project of Changping highway K94+920.9 channel bridge. Then, through analysis of the post grouting load-settlement behavior and skin friction behavior, the results are revealed as follows: Under same level of load, on average, settlement of post grouting pile is 40% smaller than non-grouting one, and settlement reducing effect is obvious; the ultimate skin friction of non-grouting pile socked in completely weathered mudstone is about 120kPa, and the ultimate skin friction of post-grouting pile completely weathered mudstone is about 240kPa, 2 times of non-grouting pile; with water cement ratio of grout of 0.5 and grouting pressure of 2MPa, the maximum grout climbing height up to 4m above pile base. It provides reference for the design of post-grouting bored piles and settlement control at mudstone stratum in this area.