scholarly journals Thermomechanical Behavior of Energy Pile Embedded in Sandy Soil

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Xu Huang ◽  
Yajun Wu ◽  
Huaifeng Peng ◽  
Yaohu Hao ◽  
Chenyang Lu
Keyword(s):  
Sandy Soil ◽  
Thermal Effects ◽  
Load Transfer ◽  
Energy Pile ◽  
Capacity Change ◽  
Energy Piles ◽  
Different Temperatures ◽  
Loading Tests ◽  
Plastic Displacement ◽  
Aluminum Pipe

The traditional energy pile (solid energy pile) has been implemented for decades. However, the design of different kinds of energy piles is still not well understood. In this study, a series of model tests were performed on an aluminum pipe energy pile (PEP) in dry sandy soil to investigate the thermal effects on the mechanical behaviors of pipe energy pile. The thermal responses of the PEP were also analyzed. Steady temperatures of the PEP under different working conditions were also compared with that of the solid energy pile. Different loading tests were carried out on four pipe energy piles under three different temperatures of 5, 35, and 50°C, respectively. The bearing capacity change can be interpreted through the load-displacement curves. Experiment results were also compared with the solid energy pile to evaluate bearing capacities of the PEP and the solid energy pile under different temperature conditions. The mobilized shaft resistance was also calculated and compared with the solid energy pile data and the results show that the PEP has a similar load transfer mechanism with the solid energy pile. It could also be found that, for PEPs under working load, plastic displacement would appear after a whole heating cycle.

Laboratory-scale pull-out tests on a geothermal energy pile in dry sand subjected to heating cycles

2020 ◽  
Vol 57 (11) ◽  
pp. 1754-1766
Author(s):  
Rehab Elzeiny ◽  
Muhannad T. Suleiman ◽  
Suguang Xiao ◽  
Mu’ath Abu Qamar ◽  
Mohammed Al-Khawaja
Keyword(s):  
Load Transfer ◽  
Pressure Sensors ◽  
Temperature Sensors ◽  
Heat Pumps ◽  
Laboratory Model ◽  
Ground Source Heat Pumps ◽  
Energy Pile ◽  
Pull Out ◽  
Energy Piles ◽  
Dry Sand

Ground source heat pumps coupled with energy piles operate intermittently, subjecting the piles to temperature cycles throughout their lifetime. The research presented in this paper focuses on studying the thermomechanical behavior of energy piles subjected to heating cycles. Laboratory model tests were performed at the soil-structure interaction (SSI) facility at Lehigh University. A fully instrumented model energy pile, embedded in dry sand, was subjected to different number of heating cycles followed by axial pull-out loading. Baseline (room temperature), five heating cycles (5HC), and 100 heating cycles (100HC) tests are reported in this paper. The soil was instrumented with temperature sensors and pressure sensors, while the pile was instrumented with temperature sensors, strain gauges, and pressure sensors. The test results showed that the peak pull-out loads for the baseline, 5HC, and 100HC were 2794 N, 3633 N (30% higher than baseline), and 3559 N (27% higher than baseline), respectively. It was also found that subjecting the pile to large number of daily heating cycles induced small degradation in the load transfer or the peak pull-out load in dry sand.

In situ investigation of the impact of cyclic thermal variations impact on the mechanical properties of sandy soil.

2020 ◽  
Author(s):  
Sandrine Rosin-Paumier ◽  
Hossein Eslami ◽  
Farimah Masrouri
Keyword(s):  
Mechanical Properties ◽  
Sandy Soil ◽  
In Situ Investigation ◽  
Energy Piles ◽  
Before And After ◽  
Cyclic Variations ◽  
Loading Tests ◽  
Adjacent Soil ◽  
Comparison Of The Results ◽  
The Impact

<p>The incorporation of heat exchangers into geostructures leads to changes in the temperature of the adjacent soil, which may affect its hydro-mechanical properties. In this study, mini-pressiometer tests were carried out in the vicinity of three experimental energy piles of 12 meters length and 0.52-meter diameter installed in saturated sandy soil. Tests were carried out in three locations and in two different depths (namely 3 and 4 meters in depth) before and after cyclic variations of their temperature. The pressuremeter parameters are the pressuremeter modulus EM, the limit pressure PL and the creep-pressure Pf. These parameters characterize the properties of the soils; some measurements were done close to the energy piles (1.25 meters from the center of the pile) using a mini-pressuremeter cell (380 mm in height and 28 mm in diameter). The comparison of the results before and after the four warming-cooling cycles (8° to 19° C) showed a thin thickening of the material at 3 meters depth. These results are coherent with in-lab measurements and with the results of the pile loading tests carried out later on the same site.</p>

scholarly journals Load transfer approach for the geotechnical analysis of energy piles in a group with slab

2020 ◽  
Vol 205 ◽  
pp. 05008
Author(s):  
Elena Ravera ◽  
Melis Sutman ◽  
Lyesse Laloui
Keyword(s):  
Load Transfer ◽  
Individual Response ◽  
Thermal Loads ◽  
Thermally Induced ◽  
Soil Response ◽  
Energy Pile ◽  
Analysis And Design ◽  
Energy Piles ◽  
Transfer Method ◽  
Load Transfer Method

Thermally induced group effects characterise closely spaced energy piles. It has been observed experimentally that the behaviour of energy piles subjected to mechanical and thermal loads, in which the piles are located sufficiently close to each other, is different from the behaviour of single isolated piles. Therefore, civil engineers encounter new challenges in the geotechnical design of such foundations. This leads to the necessity to develop practical tools to address their analysis and design. The conventional load transfer method is one of the commonly used methods for the analysis of axially loaded conventional piles. Thus, the purpose of this study has been to propose a formulation of the load transfer method to consider the thermally induced effects among energy piles in groups. The soil response is characterized in a lumped form by ascribing the behavioural features of the soil to interface elements. The individual response, in terms of strain and stress of an energy pile in a group, can be addressed for the first time through the application of the displacement factor in the load displacement curve of the single isolated energy pile. A validation through a full-scale field test reveals the capability of the approach to provide the necessary information in the analysis and design phases of the foundation for one-way thermal loads.

Exposure of Polymeric Glazing Materials Using NREL’s Ultra-Accelerated Weathering System (UAWs)

2010 ◽  
Author(s):  
Carl Bingham ◽  
Gary Jorgensen ◽  
Amy Wylie
Keyword(s):  
Light Intensity ◽  
Thermal Effects ◽  
Outdoor Exposure ◽  
Exposure Chamber ◽  
Accelerated Weathering ◽  
Intensity Level ◽  
Design And Implementation ◽  
Different Temperatures ◽  
Exposure Testing ◽  
Ultraviolet Irradiance

NREL’s Ultra-Accelerated Weathering System (UAWS) selectively reflects and concentrates natural sunlight ultraviolet irradiance below 475 nm onto exposed samples to provide accelerated weathering of materials while keeping samples within realistic temperature limits. This paper will explain the design and implementation of the UAWS which allow it to simulate the effect of years of weathering in weeks of exposure. Exposure chamber design and instrumentation will be discussed for both a prototype UAWS used to test glazing samples as well as a commercial version of UAWS. Candidate polymeric glazing materials have been subjected to accelerated exposure testing at a light intensity level of up to 50 UV suns for an equivalent outdoor exposure in Miami, FL exceeding 15 years. Samples include an impact modified acrylic, fiberglass, and polycarbonate having several thin UV-screening coatings. Concurrent exposure is carried out for identical sample sets at two different temperatures to allow thermal effects to be quantified along with resistance to UV.

scholarly journals Load transfer on instrumented prestressed ground anchors in sandy soil

2021 ◽  
Vol 14 (6) ◽  
Author(s):  
Alex Micael Dantas de Sousa ◽  
Yuri Daniel Jatobá Costa ◽  
Luiz Augusto da Silva Florêncio ◽  
Carina Maria Lins Costa
Keyword(s):  
Skin Friction ◽  
Sandy Soil ◽  
Load Transfer ◽  
Retaining Wall ◽  
Load Variations ◽  
Bored Pile ◽  
Ground Anchors ◽  
Anchor Testing ◽  
Wall System ◽  
Unbonded Length

abstract: This study evaluates load variations in instrumented prestressed ground anchors installed in a bored pile retaining wall system in sandy soil. Data were collected from instrumentation assembled in the bonded length of three anchors, which were monitored during pullout tests and during different construction phases of the retaining wall system. Instrumentation consisted of electrical resistance strain gauges positioned in five different sections along the bonded length. Skin friction distributions were obtained from the field load measurements. Results showed that the skin friction followed a non-uniform distribution along the anchor bonded length. The mobilized skin friction concentrated more intensely on the bonded length half closest to the unbonded length, while the other half of the bonded length developed very small skin friction. The contribution of the unbonded length skin friction to the overall anchor capacity was significant and this should be accounted for in the interpretation of routine anchor testing results. Displacements applied to the anchor head were sufficient to mobilize the ultimate skin friction on the unbonded length, but not on the bonded length. Performance of loading-unloading stages on the ground anchor intensified the transfer of load from the unbonded length to the bonded length. Long-term monitoring of the anchor after lock-off revealed that the load at the anchor bonded length followed a tendency to reduce with time and was not significantly influenced by the retaining wall construction phases.

scholarly journals Thermal Effect on Structural Interaction between Energy Pile and Its Host Soil

2017 ◽  
Vol 2017 ◽  
pp. 1-9
Author(s):  
Qingwen Li ◽  
Lu Chen ◽  
Lan Qiao
Keyword(s):  
Thermal Stresses ◽  
Heat Transfer Process ◽  
Structural Element ◽  
Energy Pile ◽  
Structural Interaction ◽  
Comprehensive Method ◽  
Green Power ◽  
Energy Piles ◽  
Distribution Of Stress ◽  
Peak Value

Energy pile is one of the promising areas in the burgeoning green power technology; it is gradually gaining attention and will have wide applications in the future. Because of its specific structure, the energy pile has the functions of both a structural element and a heat exchanger. However, most researchers have been paying attention to only the heat transfer process and its efficiency. Very few studies have been done on the structural interaction between the energy pile and its host soil. As the behavior of the host soil is complicated and uncertain, thermal stresses appear with inhomogeneous distribution along the pile, and the peak value and distribution of stress will be affected by the thermal and physical properties and thermal conductivities of the structure and the host soil. In view of the above, it is important to determine thermal-mechanical coupled behavior under these conditions. In this study, a comprehensive method using theoretical derivations and numerical simulation was adopted to analyze the structural interaction between the energy pile and its host soil. The results of this study could provide technical guidance for the construction of energy piles.

Field study of residual forces developed in pre-stressed high-strength concrete (PHC) pipe piles

2016 ◽  
Vol 53 (4) ◽  
pp. 696-707 ◽  
Author(s):  
Hai-lei Kou ◽  
Jian Chu ◽  
Wei Guo ◽  
Ming-yi Zhang
Keyword(s):  
Static Loading ◽  
High Strength Concrete ◽  
Large Scale ◽  
Load Transfer ◽  
High Strength ◽  
Neutral Plane ◽  
Shaft Resistance ◽  
Strength Concrete ◽  
Loading Tests ◽  
Residual Force

A large-scale field testing program for the study of residual forces in pre-stressed high-strength concrete (PHC) pipe piles is presented in this paper. Five open-ended PHC pipe piles with 13 or 18 m in embedded length were installed and used for static loading tests at a building site in Hangzhou, China. All the piles were instrumented with fiber Bragg grating (FBG) strain gauges. The residual forces in these piles were recorded during and after installation. The measured load transfer data along a pile during the static loading tests are reported. The effect of the residual force on the interpretation of the load transfer behavior is discussed. The field data show that residual force along the installed pile increases approximately exponentially to the neutral plane and then reduces towards the toe. The residual force decreases with time to a stable value after pile jacking due to the secondary interaction between the pile and the disturbed soil around the pile and other factors. The large residual forces along the PHC pipe piles significantly affect the evaluation of the pile load distributions, and thus the shaft and toe resistances. The conventional bearing capacity theory tends to overestimate the shaft resistance at positions above the neutral plane and underestimate the shaft resistance at positions below the neutral plane, and the toe resistance for an open-ended PHC pipe piles founded in stratified soils.

Thermal Effects on Wheel Performance Based on Twin Disc Testing

2020 ◽  
Author(s):  
Dingqing Li ◽  
Monique Stewart
Keyword(s):  
Thermal Effects ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Contact Forces ◽  
Rolling Contact ◽  
Test Machine ◽  
Testing Program ◽  
Different Types ◽  
Different Temperatures ◽  
Surface Performance

Abstract This paper presents the results and findings from a testing program conducted to investigate how temperature at the wheel-rail interface may affect wheel surface performance; i.e., development of rolling contact fatigue (RCF) and wear. Under this testing program, a twin disc test machine was used to test two different types of wheel specimens (cast and forged) under a range of temperatures (ambient to 800° F) and slip ratios from 0 to 0.75 percent. This testing program included a total of 32 tests, covering two wheel materials, four different temperatures, four slip ratios, and various traction coefficients as a ratio of longitudinal and vertical wheel/rail contact forces.

Thermomechanical Behavior of Energy Piles and Interactions within Energy Pile–Raft Foundations

2020 ◽  
Vol 146 (9) ◽  
pp. 04020079
Author(s):  
Jincheng Fang ◽  
Gangqiang Kong ◽  
Yongdong Meng ◽  
Lehua Wang ◽  
Qing Yang
Keyword(s):  
Thermomechanical Behavior ◽  
Energy Pile ◽  
Energy Piles ◽  
Raft Foundations

scholarly journals Analytical solution and process analysis of energy pile’s heat transfer rate

2020 ◽  
Vol 205 ◽  
pp. 05026
Author(s):  
Jun Yang ◽  
Zhenguo Yan ◽  
Zhengwei Zhang ◽  
Shu Zeng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Heat Transfer Process ◽  
Transfer Performance ◽  
Energy Pile ◽  
Energy Piles ◽  
The Difference ◽  
Surrounding Soil

With the ever-increasing energy demand and implications of climate change, the use of energy piles to absorb shallow geothermal energy to regulate room temperature of buildings is considered the best sustainable energy technology, especially in China, and the use of this technology is becoming increasingly popular. At present, studies generally uses the temperature field to analyze the heat transfer performance of the energy pile, which cannot represent the heat transfer rate distribution intuitively. In this study, we used mathematical models to provide an analytical solution to determine the heat transfer rate distribution between the energy pile and surrounding soil. Analysis of the heat transfer process of concrete piles in clay showed that the difference in thermal properties between the energy pile and the surrounding soil affected the whole heat transfer process, especially in the initial stage. The time required to reach the quasi-steady state mainly depended on the pile’s volume heat capacity, the thermal diffusivity of the pile and the surrounding soil. In engineering practice, to enhance the heat transfer performance of energy piles, the following measures can be taken: reduce the difference in thermal properties between the energy pile and surrounding soil and increase the distance between energy piles to improve the heat transfer conditions.

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