Study on the Distribution Law of Crustal Stress in Fault Fracture Area

Determining crustal stress is crucial in the design and construction of underground engineering projects, particularly in fault fracture zones. This paper aims to identify the characteristic factors that influence the crustal stress of faults, including the difference in deformation characteristics between faults and ordinary formations (expressed by the elastic modulus ratio Er/Ef), the degree of fault fragmentation P, and the angle α between fault tendency and the principal stress direction. Numerical simulations are conducted to investigate the impact of these three factors on the magnitude and direction of the principal stress. Additionally, measured stress values from a specific tunnel are analyzed to validate the findings. The results demonstrate the crucial role of α in determining the increase or decrease of principal stress and the direction of the offset. When α is less than 45°, σ1 and σ3 within the fault experience an increase, while σ1 and σ3 in the ordinary surrounding rock area near the fault exhibit a slight decrease. Moreover, the σ1 direction inside the fault deviates towards the parallel fault, whereas σ1 near the outside slightly deviates towards the vertical fault. Conversely, when α is greater than 45°, the trend of principal stress is reversed. Er/Ef affects the magnitude of the principal stress change, with larger values resulting in more pronounced changes. P only affects the stress distribution inside the fault.