In-situ test and numerical verification of bearing capacity of soft rock foundation with depth

Currently, there is insufficient confidence in the application of soft rock in major projects, leading to overly conservative design of foundation bearing capacity. Clarifying the stress distribution and failure process of soft rock foundation with depth offer guiding significant for determining the bearing capacity of soft rock foundation in practical geotechnical engineering. Based on the arch foundation project of the Fifth Bridge of the Lantian Yangtze River, this paper investigated the bearing capacity of soft rock foundations and its depth correction rule by analyzing field test results and numerical simulations.  A formula inversion model was established referencing current standards and relevant literature, and the depth correction coefficient k2 for soft rock foundation bearing capacity was calculated based on field test measurements.  Using finite element software PLAXIS 3D, a numerical model of soft rock foundations with variables including load plate burial depth and lateral limiting conditions was created under field conditions and calculate the simulated bearing capacity of soft rock foundations.  By combining results from both methods, the variation rule of soft rock foundation bearing capacity influenced by depth factors is analyzed, and the applicability of different research methods is discussed.  It is found that within a certain range, the bearing capacity of soft rock foundations has a linear positive correlation with burial depth, and after reaching 15d, it shows a gradual trend.  Finally, recommended values for the depth correction coefficient are 2.5 (for undetailed or poor foundation conditions) and 8.0 (for good foundation conditions with low weathering degree), with different values adopted according to site conditions.  Furthermore, the bearing capacity of soft rock foundations with free surfaces was discussed, offering a valuable reference for similar future engineering scenarios.  After the bearing capacity measurement and foundation deformation performance analysis, it was concluded that there is still a significant bearing capacity reserve, which provides essential data support for dimensional optimization.  This paper further substantiates that the bearing capacity of soft rock foundation can be significantly enhanced through in-depth modification, thereby offering meaningful reference and guidance for practical engineering applications.