Abstract
Columnar jointed basalts (CJB) are featured by the joint network of discontinuities, which is hard for geotechnical design and construction. Therefore, investigating the mechanical behaviors of CJB is significant for the long‐term use of the engineering structures. In this paper, field research studies, such as the rigid bearing plate tests and acoustic tests, were employed, to obtain the deformation modulus and the acoustic velocity of columnar jointed basalts, and the formula expressed by deformation modulus and acoustic velocity was then established, which would be a useful guidance for the site operation. Based on the monitoring and testing data of CJB, several numerical simulation models with different joint angles and weak thickness were built to further discuss the mechanical behaviors of CJB. The numerical simulation results show that the joint angle of 30° ∼ 60° presents weak antipressure abilities, for the shearing slipping force and interformational sliding are remarkable in them. Besides, the small material property difference is helpful for the compressive strength of rock masses. After adopting the most unfavorable joint angle and width to model the tunneling process in CJB, it suggests that it is easily damaged along the directions of rock joints in CJB when constructing in tunnels.
Highlights
Erefore, investigating the mechanical behaviors of columnar jointed basalt (CJB) has become urgent matters in recent years due to their particular damage modes and mechanical behaviors during the columnar jointed basalts (CJBs) tunneling and excavation, which poses adverse effects on project stability
When η is less than 10%, it is considered that the excavation has little or no influence on the rock masses; when the value of η is between 10% and 15%, the rock masses are considered slightly affected by the excavation; when η is larger than 15%, it is believed that the excavation has influence on the rock mass quality
When the thickness of weak intercalation increases to a certain value (3.75 mm), the stress strength of CJB appears a tiny increase, because the rock specimen gradually becomes intact, and it is advantageous for the stress strength of CJB
Summary
Erefore, investigating the mechanical behaviors of CJB has become urgent matters in recent years due to their particular damage modes and mechanical behaviors during the CJB tunneling and excavation, which poses adverse effects on project stability. Laboratory tests on rock mass and physical modeling tests have been conducted as well [28,29,30], to evaluate mechanical behavior and failure mechanisms [31, 32]. Limited by the scale of laboratory tests, field tests become an effective way to confirm mechanical properties of rock masses. Numerical simulation methods are quick and effective approaches to investigate the mechanical behaviors of CJB. A novel geometric modeling method based on the topological properties of field columnar basalt was employed, which provided a method to estimate rock mass modulus using numerical simulation. A modified constrained centroid Voronoi tessellation (CCVT) algorithm was put forward to analyze the influence of columnar jointed structure on the mechanical properties of CJB. A computational interaction algorithm with high numerical accuracy and efficiency under the loading conditions of plasticity, damage, and coupled elastoplastic damage was developed
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