Search

The problem of the bump at the transition between the embankment and the bridge is an important concern for railways and highways. These bumps can lead to a rough riding surface which creates discomfort at high speed and high maintenance costs. The current study addresses the problem for High Speed Trains (HST). One reason for the development of a bump is the difference in stiffness between the compacted soil embankment and the bridge typically resting on deep foundations. A 4-D finite element model, developed in LS-DYNA, was used to simulate the effect of this difference in stiffness at the transition between the embankment and the bridge. The modulus of the embankment is varied from 5 MPa for a very soft embankment to 120 MPa for a very stiff embankment. The bridge is considered to be rigid by comparison. This study will show that the dynamic amplification factor, DAF, defined as the ratio of the maximum dynamic rail/wheel impact force to the static load on the wheel, changes dramatically with the embankment modulus and train speeds. [ABSTRACT FROM AUTHOR]

The rapid modernization has been mainly based on non-renewable fossil-fuels sources with the associated uncontrolled release of greenhouse gases impacting negatively on our environment. New renewal energy technologies, like shallow geothermal systems can help to solve this problem. This method harnesses constant and moderate ground temperature that is used to assist in the air conditioning of buildings. This technology is growing rapidly because it consumes less conventional energy for operation, which in turn results in fewer CO 2 emissions. A group of energy piles was installed and instrumented as part of the foundation system of a new five-story building constructed in Texas A&M University, USA. This setup is used in this research to explore the performance of this technique to control the building temperature under cooling-dominated weather conditions. This study found that integrating energy piles in building foundations could be an economical and environmentally friendly solution also under such climate conditions, but attention should be paid to the thermodynamic efficiency of the system when unbalanced pile-ground heat-transfer cycles take place through the year. ∙ Pilot energy-piles tests in a building operated under a cooling-dominated climate. ∙ Simulation of the long-term (30 years) performance of the energy pile system. ∙ Economic study anticipates a payback period of around 13 years. ∙ Prevailing cooling demand leads to unbalanced heat transfer cycles through the year. ∙ Progressive increase of ground temperature jeopardizes long-term system efficiency. [ABSTRACT FROM AUTHOR]

Energy piles are bi-functional foundation elements used as structural support as well as ground heat exchangers for shallow geothermal energy systems. Because they are relatively short, energy piles may be partially embedded in unsaturated soils. Saturation conditions influence the thermal properties of the ground and therefore the heat exchange rate, which in turn affects the efficiency of energy piles. This paper combines analytical, experimental and numerical investigations to evaluate the heat exchange rate of energy piles partially or fully embedded in unsaturated soils. The proposed analytical solution is based on the cylindrical heat source theory that treats the soil as a semi-infinite, homogeneous, and isotropic medium. The solution from this theory is multiplied by a function developed analytically in this paper and the outcome is the heat exchange rate for energy piles in unsaturated soils. The proposed function depends on soil saturation, soil and pile thermal properties, and pile geometry. The analytical solution was compared against a finite element solution; which was in turn validated against results from laboratory experiments. Very satisfactory agreements between the analytical, numerical and experimental outputs were observed. The proposed method can be used for a quick and simple evaluation of the efficiency of energy piles in unsaturated conditions. The proposed analytical solution can also be a useful tool for the verification of numerical codes developed for the design of energy piles in unsaturated soils. [ABSTRACT FROM AUTHOR]