Field pull out test results of 500 kV double-circuit line of Luping-Fule are presented in this paper to investigate the uplift bearing behavior of rock-socketed belled short piles. A calculation model of rock-socketed belled short pile has been proposed. During the initial stage of loading test, uplift load is shared by even section and bell of the pile, and the bell continues to bear uplift load after the lateral resistance of even section pile reaches the limit. A different performance has been found on the case of long belled pile. At the ultimate state, the uplift resistance provided by bell accounts for about 54.9% and 34.7% of the total uplift capacity for the 6.0 m long and 7.0 m long piles, respectively. Increasing pile length has been found to noticeably increase the ultimate uplift bearing capacity, while it has less effect on the displacement of pile top. The uplift capacity of even section pile is associated with the shear strength of rock mass around the pile, and the test results demonstrate that the ultimate resistance can be equal to the shear strength. The calculation method proposed in this paper is proven to be able to accurately predict the ultimate uplift bearing capacity of the rock-socketed belled short piles.

The stratums along the Beijing-Shanghai high-speed railway are composed mainly with soft soil. The foundation of roadbed were strengthened in hope of reducing differential and total settlement. Ram-compacted piles are mentioned in this paper, as an example of strengthening methods. Using joint test method combining liquid level settlement gauges and single point settlement gauges, total settlements and compressions at different depths were measured. Field test results showed that：1. The settlements were significantly reduced. 2. The settlement of the basement with cap at the middle of roadbed mainly appeared during filling stage, and that without cap indicated a 30-day-stablisation during preloading stage. 3. The up thorn can be decreased by pile cap. 4. The largest settlement was found at roadbed center, whereas the smallest occurred at embankment toe. Ram-compacted piles successfully reduced settlement of roadbed, offering reference value to high-speed railway design.

The railway substructure needs to be monitored to determine whether the substructure is stable. In the paper, the damages to the substructure of the heavy-haul railway in the tunnel were recognized and the grouting technology and water pipes were used to avoid further damages. To monitor the state of the substructure in the tunnel, a wireless monitoring system was developed. The accelerometers, laser rangefinders, water level gauges, and cameras were used in the sensor module, the fiber optics and mobile telephony were used in data transferring module, and a data managing system was developed in the control center. To examine the measured date by the monitoring system, the measured vertical displacement and horizontal displacement, the settlement, and the water levels at the site were presented. The measured data showed that the underground voids still existed after the grouting technology and water pipes of installation were applied. The horizontal and vertical displacement and settlement were induced by the underground voids and the loading of the train. The water level varied at the three locations, and the change of the water level beneath the surface showed that the flowing water was drained due to the water pipes. The wireless monitoring system was successfully developed to monitor the real-time data of the substructure and determine if the substructures was stable.

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