PublisherThe University of Arizona.
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EmbargoRelease after 09/21/2024
AbstractIn a real three-dimensional (3D) world, the ground around structures is also under 3D stress states. Although the 3D stress states or three principal stresses significantly affect the behavior of rock mass in field and laboratory tests, the intermediate principal stress is still ignored in the current analytical and numerical approaches for rock mechanics and rock engineering problems. To bridge this gap, in the current study, the effect of intermediate principal stress on rock mass strength was stressed and considered in a 3D revision of the well-known Hoek-Brown (HB) criterion, and then the proposed 3D criterion was further developed as a constitutive model for rock mass and applied to various rock engineering practices.First, a 3D revision of the HB criterion was proposed to consider the effect of the intermediate principal stress as well as the smoothness and convexity of the failure criterion in the 3D principal stress space. The smoothness and convexity of the proposed failure criterion were checked by mathematical proofs and comparisons among the proposed criterion and other 3D criteria were made regarding the true triaxial tests of elven rocks. Second, based on the laboratory tests on the stress-strain relations of rock, a unified constitutive model for rock mass was proposed using the proposed 3D strength criterion. And the proposed constitutive model was successfully implemented as a user-defined constitutive model in a commercial numerical modeling software FLAC3D. Then the performance of the proposed constitutive model was evaluated by applying it to both laboratory experiments and a tunnel project. Third, the proposed 3D criterion for rock mass was applied to theoretically analyze deep tunnels in rock mass with the consideration of disturbed zone, large strain and 3D strength. Validation of the theoretical solution was verified by a numerical simulation by FLAC3D, and parametric studies were conducted to investigate the influences of the disturbed zone and rock mass properties. Fourth, the end-bearing capacity and side shear bearing capacity of rock socketed shafts were analyzed based on the proposed 3D strength criterion for rock mass and the method of characteristics. Comparisons between the proposed solutions and summarized field and laboratory tests were made to verify the validity of the proposed solutions. Fifth, the semi-analytical solutions to the bearing capacities of shallow foundations including strip and circular foundations on rock mass were presented based on the proposed 3D strength criterion for rock mass and the method of characteristics. A finite difference scheme was utilized to solve the characteristic mesh below the foundation with both smooth and rough base conditions. Parametric studies were performed on the effects of rock mass properties and foundation size on the failure surface and bearing capacity. Finally, the stability of rock slopes was evaluated by an upper bound limit analysis using the proposed 3D strength criterion for rock mass and a user-defined genetic algorithm for optimization. A GUI app based on Python programming language was developed for the proposed approach and then further bundled as a standalone excusable program. As a work beyond the scope of applying the proposed 3D criterion but related to rock mechanics, an ensemble learning approach based on four machine learning algorithms was trained on a database for predicting the bearing capacity of rock socketed shafts. To train the model, a database of 151 rock socketed shafts with tested end bearing capacities and rock mass properties was summarized from the literature. Then a graphic user interface (GUI) was developed based on the proposed model by using the MATLAB programming language.
Degree ProgramGraduate College
Civil Engineering & Engineering Mechanics