Pile foundations in calcareous sand are often applied to bear vertical cyclic loads. Model tests of a single pile bearing vertical cyclic loads were performed in calcareous sand, and the accumulated settlement and bearing capacity were measured via sensors using a self-designed experimental device. The influences of the dynamic load and number of cycles on the accumulated settlement and bearing capacity of the pile were analyzed. The results revealed that the accumulated settlement of the pile increased with the number of cycles, it was categorized as either stable, progressive, or destructive. The “threshold effect” was observed once a critical number of cycles had been achieved, the particles breakage hindering the settlement tendency lead to the accumulated settlement rate of the pile gradually decreased and stabilized. During cyclic loading, the proportions of the upper load shared by the pile end and side constantly changed, the pile-side frictional resistance gradually decreased, while the average resistance of pile end slowly increased. After cyclic loading, the bearing capacity of the pile was improved slightly, but the pile-side frictional resistance was greatly reduced, two formulas were presented. The test results can be used for the design of pile foundations in calcareous sand.

A novel fiber-optic based earth pressure sensor (FPS) with an adjustable measurement range and high sensitivity is developed to measure earth pressures for civil infrastructures. The new FPS combines a cantilever beam with fiber Bragg grating (FBG) sensors and a flexible membrane. Compared with a traditional pressure transducer with a dual diaphragm design, the proposed FPS has a larger measurement range and shows high accuracy. The working principles, parameter design, fabrication methods, and laboratory calibration tests are explained in this paper. A theoretical solution is derived to obtain the relationship between the applied pressure and strain of the FBG sensors. In addition, a finite element model is established to analyze the mechanical behavior of the membrane and the cantilever beam and thereby obtain optimal parameters. The cantilever beam is 40 mm long, 15 mm wide, and 1 mm thick. The whole FPS has a diameter of 100 mm and a thickness of 30 mm. The sensitivity of the FPS is 0.104 kPa/με. In addition, automatic temperature compensation can be achieved. The FPS’s sensitivity, physical properties, and response to applied pressure are extensively examined through modeling and experiments. The results show that the proposed FPS has numerous potential applications in soil pressure measurement.