Abstract：Diwang Commercial Center and Jiadexin Crystal Mansion are both high-rise buildings in Nanning，and they are close to each other. Foundations of them are both made of manual digging socketed belled piles in tertiary mudstone. Tertiary mudstone is a typical soft rock distributing widely in Nanning Basin，Guangxi Autonomous Region. It is usually chosen as the bearing stratum of pile foundation. In order to master the engineering characteristics of socketed pile in soft rock，the self-balanced loading test is conducted to test eight piles of two high-rise buildings. The cell assembled in the pile body is the key equipment of the test. To get better test effect，assembly of cell has been taken different modes in terms of depth that pile socketed in rock and dimension of enlarged toe. By the self-balanced loading test，the problem that the ultimate bearing capacity of the large tonnage socketed belled pile in soft rock is hard to be acquired is solved. Several key parameters required in design are obtained. In terms of test results，the bearing performances of the piles are studied. By comparing the test curves of pile tip，pile side and the equivalent converted curves of the whole pile，it reveals apparently that the bearing capacity of the socketed pile in mudstone will decrease after mudstone has been immerged. Since effective measures have been taken；mudstone is prohibited from being immerged during construction. And valuable experience has been accumulated for similar projects construction henceforth.
