This paper describes the use of a sensor based on a fiber Bragg grating (FBG), which is capable of reducing strain transfer errors, to measure the strain features within the top and bottom layers of a cement concrete pavement subject to different degrees of foundation settlement. Based on measured data, the characteristics of the distribution and the variation in the structure strain were analyzed in detail. By comparing the measured results with those obtained by means of finite element analysis, the proposed FBG-based sensor assembly was found to be capable of effectively monitoring the strain distribution in a cement concrete pavement, thus proving that the improved optical fiber grating strain sensor is a very promising solution for road pavement structural health monitoring.
Soil-rock mixture is a commonly used geotechnical material used in many construction projects, such as slopes, tunnels, and dams. The shear strength of soil-rock mixture is its key property and is affected by many factors. This study aimed to investigate the shear strength characteristics of soil-rock mixture and the influences of moisture and stone content on shear strength parameters. Soil-rock mixture samples with four different stone and moisture contents were fabricated and tested using a large-scale direct shear test apparatus under four vertical pressures. The results demonstrated that the shear properties of the soil-rock mixture showed significant Mohr Coulomb failure criteria for all stone contents. As the moisture content increased, the shear strength of the soil-rock mixture first increased by 10~18% and then decreased after w = 12% to the residue value. The change in cohesion and internal friction angle of soil-rock mixture with different moisture contents shared a similar trend. For w < 12%, the cohesion and internal friction angle increased with moisture content, and for w > 12%, the two indexes obviously decreased. As the stone content increased from 30% to 60%, the shear strength of the soil-rock mixture increased by 82~174%. The internal friction angle increased linearly with stone content, while the cohesion of the mixture first increased and then decreased after the stone content reached 50%. The results can help in the designation and application of soil-rock mixture.
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