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Beaverton, OR, United States

Meskele T.,Geotechnical Resources Inc. | Stuedlein A.W.,Oregon State University
Pipelines 2014: From Underground to the Forefront of Innovation and Sustainability - Proceedings of the Pipelines 2014 Conference

Pipe ramming is an emerging trenchless technique that allows installation of pipes and culverts in soils that can pose difficulty to other trenchless technologies. However, because pipe ramming hammers provide high-frequency impact blows to the pipe, high-magnitude stress waves travel down the pipe and are transmitted to the surrounding soil. This can have a serious adverse effect on adjacent structures and nearby utilities if located sufficiently close to the pipe alignment. The potential effects include differential settlements, densification, and local liquefaction depending on the soil and groundwater conditions. Owing to the lack of field observations in the literature, this study was conducted to observe the ground vibrations that can result from pipe ramming and to provide guidelines for the prediction of pipe ramming-induced vibration. An experimental pipe-ramming project was conducted that consisted of the installation of open-ended steel pipe 1,070 mm in diameter and 36.5 m long rammed with two pneumatic hammers. Observations indicated that the vibrations measured at the ground surface largely comprised surface waves, and that vibrations propagate most intensely from the face of the pipe, but also from the surface area of the embedded casing. Ground vibrations are presented as a function of frequency content, magnitude of peak particle velocity, proximity to the source, and direction of propagation. The information obtained from the experimental evaluation of pipe ramming-induced ground vibrations reported herein can provide the means for a first approximation of vibration-induced damage susceptibility. © 2014 American Society of Civil Engineers. Source

Stuedlein A.W.,Oregon State University | Reddy S.C.,Geotechnical Resources Inc. | Evans T.M.,Oregon State University
DFI Journal

This closure addresses the comments made by the discussers to a previously published paper on the interpretation of failure loads from static loading tests on augered cast-in-place piles. In this closure, it is shown that there were no data or interpretation problems as postulated by the discussers. It is shown that: the ratio of elastic and initial compression slopes depends on the slenderness ration, the L2 capacity depends on the magnitude of displacement imposed, and the L2 capacity relative to the Davisson capacity is a function of the axial stiffness. This closure points to the important role of slenderness ratio (which serves as a proxy for axial stiffness) on the interpretation of failure loads. © 2015 Deep Foundations Institute. Source

Meskele T.,Geotechnical Resources Inc. | Stuedlein A.W.,Oregon State University
Journal of Pipeline Systems Engineering and Practice

Pipe ramming installations generally induce high levels of ground vibrations that may affect the structural integrity of nearby buildings and utilities. This paper investigates the ground vibrations associated with pipe ramming installations and develops reliable models for estimating the ground vibration levels in an effort to avoid the undesirable effects of the vibrations. The study presents field observations of ground vibrations in which an open-ended steel casing 1,070 mm in diameter and 37 m long was driven into granular soils using two pneumatic hammers of varying energy. The ground vibrations observed during the installation are presented as a function of magnitude of peak particle velocity, frequency content, and direction of propagation. Observations indicate that a wide range of amplitudes and frequencies is possible, ranging from 1 to 100 mm/s and 20 to 100 Hz, respectively, for the case of forward and laterally propagating vibrations. The forward-propagating vibrations were observed to exceed the safe limit vibration criteria for a proposed pipe alignment for close source-to-sensor distances, indicating a potential for damage caused by pipe ramming-induced vibrations. The attenuation characteristics of the pipe ramming-induced vibrations were assessed by adopting and calibrating the existing scaled-distance empirical model and compared to those for a number of common construction operations. © 2015 American Society of Civil Engineers. Source

Meskele T.,Geotechnical Resources Inc. | Stuedlein A.W.,Oregon State University
Journal of Geotechnical and Geoenvironmental Engineering

The evaluation of the drivability of a proposed pipe is a critical task in the planning and execution of pipe-ramming installations, because it results in increased efficiency, safe installations, and significant cost savings. The analysis of drivability provides a means for optimizing the hammer energy required for a given pipe-ramming installation, and it minimizes potential damage to the pipe due to overstressing the pipe material. Four full-scale pipes with diameters ranging from 610 to 3,660 mm installed using pipe-ramming hammers were instrumented to observe the measurement of hammer-pipe energy transfer, driving stresses, and total (static and dynamic) soil resistance to penetration and formed the basis for evaluating drivability. First, the hammer-pipe energy transfer calculated from the observed force and velocity time histories was characterized, indicating the quantity of energy that actually results in the penetration of the pipe through soil. Then, the dynamic model parameters known as the soil quake and damping were back-calculated using common signal-matching analyses and presented as a function of normalized soil resistance. Wave-equation analyses used routinely to assess the constructability of pile foundations were adapted to estimate the observed force time histories and driving curves or the variation of penetration resistance with static soil resistance. Wave-equation analyses were also used to estimate the observed compressive and tensile driving stresses and the accuracy of the estimates characterized. The results of this study and those used to develop equations for static soil resistance to ramming can be used as the basis for the evaluation of the drivability of rammed pipes. © 2014 American Society of Civil Engineers. Source

Meskele T.,Geotechnical Resources Inc. | Stuedlein A.W.,Oregon State University
Journal of Geotechnical and Geoenvironmental Engineering

Pipe ramming is a cost-effective trenchless pipe installation method in which percussive blows generated by a pneumatically or hydraulically powered encased piston rammer are used to advance a pipe or culvert through the ground. To evaluate the feasibility of a pipe ramming installation, engineers must be able to reliably predict the pipe drivability and installation stresses. Assessment of the drivability of the pipe and selection of the optimal hammer for pipe ramming installation requires that the static and dynamic soil resistance to ramming at the pipe face and along the casing be reliably estimated. However, pipe ramming-specific models are not currently available, and engineers often resort to the existing traditional pipe-jacking and microtunneling models for static soil resistance computations. This paper describes the results of four full-scale pipes rammed in the field and the corresponding static soil resistance to ramming in granular soils. A companion paper addresses dynamic soil resistance and pipe drivability. The accuracy of the existing pipe jacking and microtunneling-based static soil resistance models is evaluated herein and found to provide unsatisfactory estimates of the face and casing resistance. New semiempirical pipe ramming-specific models are proposed based on the field observations and are found to produce good estimates of static soil resistance for use in pipe drivability evaluations. © 2014 American Society of Civil Engineers. Source

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