Mastering the strain transfer mechanism in distributed fiber optic (DFO) sensors holds the key to analyzing strain measurement errors from DFO sensing systems. However, the impact of the monitored structure’s strain distribution on the strain transfer mechanism in DFO sensors has often been overlooked in the existing research. To address this issue, a strain transfer model of surface-bonded DFO sensors with multilayered structures was established based on the shear lag theory. The closed-form solutions of the strain transfer coefficient of DFO sensors subjected to uniform, parabolic, single-linear gradient, and bilinear gradient strains were obtained. With a high-accuracy optical frequency-domain reflectometer (OFDR), the theoretical model was validated by laboratory tests. Upon parametric analysis, suggestions were further offered about designing and installing DFO sensors.

The dam site of Kaluma Hydropower Station is located on the Nile River in northern Uganda. It is a diversion power station with a total installed capacity of 600 MW. The gneissic fissures and medium dip fissures in the plant area not only reduce the strength of the rock mass, but also easy to form adverse combinations and cuts, which adversely affecting the stability of the cavern. Therefore, surrounding rock deformation and block instability are the key factors affecting the stability of underground caverns. Based on the field investigation data, according to the research of geological prototypes such as rock mass structural plane investigation and quality classification, this paper uses the finite element numerical analysis software FLAC^3D to establish and calculate the numerical model, adjusts the boundary conditions of the model through parameter inversion, and then calculates the stress and strain of each part of the rock mass, so as to evaluate the excavation stability of underground powerhouse construction. The actual situation of construction and excavation verifies the accuracy of numerical analysis and calculation.

According to the latest physical mechanical parameter of rock, crustal stress, section style and support parameter, rock stability of intersection of EVT- Ventilation Tunnel 2-1 and Ventilation Shaft 2 is analyzed and verified through FLAC3D on the base of actual geology parameter and test value of crustal stress.