Pile Setup in Cohesive Soil. II: Analytical Quantifications and Design Recommendations

: This paper establishes a methodology to quantify pile setup by using recent field test data that was presented in a companion paper for steel H-piles driven in cohesive soils. Existing methods found in literature for the same purpose either require restrikes of piles onsite or are developed for a specific soil type and seldom use easily quantifiable soil properties, despite their significant influence on pile setup. Following a critical evaluation of the existing methods, a new approach for estimating pile setup was developed using dynamic measurements and analyses in combination with measured soil properties, such as the horizontal coefficient of consolidation, undrained shear strength, and the standard penetration test N value. Using pile setup information available in the literature, the proposed approach has shown that it provides good estimates for the setup of steel H-piles, as well as for other types and sizes of driven piles

Pile Setup in Cohesive Soil. I: Experimental Investigation

Pile setup in cohesive soils has been a known phenomenon for several decades. However, a systematic field investigation to provide the needed data to develop analytical procedures and integrate pile setup into the design method rarely exists. This paper summarizes a recently completed field investigation on five fully instrumented steel H-piles embedded in cohesive soils, while a companion paper discusses the development of the pile setup method. During the field investigation, detailed soil characterization, monitoring of soil total lateral stress and pore-water pressure, collection of pile dynamic restrike data as a function of time, and vertical static load tests were completed. Restrike measurements confirm that pile setup occurs at a logarithmic rate following the end of driving, and its development correlates well with the rate of dissipation of the measured porewater pressure. Based on the field data collected, it was concluded that the skin friction component, not the end bearing, contributes predominantly to the setup, which can be accurately estimated for practical purposes using soil properties, such as coefficient of consolidation, undrained shear strength, and the standard penetration testN-value

Potential of ground source heat pump systems in cooling-dominated environments: Residential buildings

For countries in the Arabian Peninsula, air conditioning (A/C) systems account for 65% of the energy consumption, all of which comes from fossil fuel. Given the preparation for the 2022 World Cup, which will be held in Qatar, the possibility of implementing ground source heat pump systems (GSHP) for A/C purposes is investigated. Due to its high thermal performance, GSHP is considered a viable solution for reducing the energy consumption of heating and A/C systems. However, for the GSHP system to gain popularity in cooling-dominated environments such as Qatar, financial and environmental benefits need to be demonstrated. These benefits strongly depend on local design practices and standards and on working conditions.The work presented in this paper demonstrates the energy savings by using GSHP systems in the residential buildings sector in cooling-dominated environments. To achieve this goal, a common type of residential house located in Doha, Qatar, was chosen as a case study. The cooling load of the case study and the driving energy of two different air conditioning systems were estimated. The two considered air conditioning systems are the conventional air source heat pump system (reference system) and the ground source heat pump system. Finally, economic analysis of the proposed system for construction practices in Qatar was carried out.The performed analyses show that the reduction in the prime energy demand and, consequently, the greenhouse gas emissions for the GSHP is 19% when compared to the conventional air source heat pump system. In addition, the analyses show that for the local conditions in Qatar the payback time of GSHP is 9 years.This work was made possible by an NPRP 7-725-2-270 a grant from the Qatar National Research Fund (a member of The Qatar Foundation)

Modified-thermal borehole shear test device and testing procedure to investigate the soil-structure interaction of energy piles

The intermittent operation of heat pumps connected to energy piles causes cyclic variation of temperature in the pile and surrounding soil, affecting the soil-pile interaction in ways that have not been fully investigated or directly measured. The temperature variation and cycles produce expansion and contraction of the pile in both the axial and radial directions and affect soil properties. In this study, a fully automated modified-thermal borehole shear test (Modified-TBST) device was developed to measure the thermo-mechanical behavior of the soil-pile interface properties considering the effects of radial expansion/contraction and temperature variation and cycles. Unlike other devices, the developed Modified-TBST device is fully automated and capable of combining the effects of temperature cycles with radial expansion/contraction (displacement) cycles or separating their effects. This paper describes the testing device, including the control method for expansion/contraction displacement cycles, the calibration of the shear head under non-isothermal conditions, and the measured load and displacement controls during the shearing stage. Furthermore, the paper presents procedure recommendations for performing the soil-pile interface tests, simulating energy piles and presenting preliminary results of shear stress-vertical displacement (t-z curves), considering temperature and displacement effects. 1 2017 ASTM International. All rights reserved.This work was made possible by an NPRP 7-725-2-270 grant from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

A Radio Propagation Model for Wireless Underground Sensor Networks

Abstract—An accurate and simple radio propagation model for underground low-power devices such as wireless sensor nodes is introduced and its performance is evaluated by real wireless sensor nodes. The proposed model describes underground radio signal propagation that is proportional to e −2αρ /ρ 2 where ρ represents the distance and α represents the attenuation constant reflecting the soil properties. To evaluate the proposed underground radio propagation model, experiments measuring the radio signal strength with underground sensor nodes were conducted in various sub-surface conditions. Comparing the theoretical estimations of the underground radio propagation and the measured data, the theoretical model fits the measured data well within a 3.45dBm deviation or with an accuracy of 96.33% on average

Subsurface Event Detection and Classification Using Wireless Signal Networks

Subsurface environment sensing and monitoring applications such as detection of water intrusion or a landslide, which could significantly change the physical properties of the host soil, can be accomplished using a novel concept, Wireless Signal Networks (WSiNs). The wireless signal networks take advantage of the variations of radio signal strength on the distributed underground sensor nodes of WSiNs to monitor and characterize the sensed area. To characterize subsurface environments for event detection and classification, this paper provides a detailed list and experimental data of soil properties on how radio propagation is affected by soil properties in subsurface communication environments. Experiments demonstrated that calibrated wireless signal strength variations can be used as indicators to sense changes in the subsurface environment. The concept of WSiNs for the subsurface event detection is evaluated with applications such as detection of water intrusion, relative density change, and relative motion using actual underground sensor nodes. To classify geo-events using the measured signal strength as a main indicator of geo-events, we propose a window-based minimum distance classifier based on Bayesian decision theory. The window-based classifier for wireless signal networks has two steps: event detection and event classification. With the event detection, the window-based classifier classifies geo-events on the event occurring regions that are called a classification window. The proposed window-based classification method is evaluated with a water leakage experiment in which the data has been measured in laboratory experiments. In these experiments, the proposed detection and classification method based on wireless signal network can detect and classify subsurface events

Subsurface Event Detection and Classification Using Wireless Signal Networks

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