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Abstract

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. (C) 2014 American Society of Civil Engineers.

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... The drivability of rammed pipes requires an estimate of static and dynamic soil resistance. Dynamic soil resistance to ramming and pipe drivability is described in a companion paper (Meskele and Stuedlein 2014b). This paper focuses on static soil resistance to ramming in granular soils. ...
... On the basis of semiempirical adjustment of the existing models, new pipe ramming-specific static soil resistance models are calibrated, and their accuracy and uncertainty are quantified. This work presents the first known pipe ramming-specific soil resistance models, and these models may be used in conjunction with the pipe drivability studies described in Meskele and Stuedlein (2014b) to estimate the feasibility of proposed pipe ramming installations until more data become available. ...
... The static soil resistance increased with penetration of the fifth segment because of increased penetration length, filling of the pipe with spoils, and the loss of lubrication owing to a rupture of lubricant conduit. This was accompanied by an increase in penetration resistance over the same driving interval of approximately 250% (from 2,000 to 5,000 blows=m) as described in Meskele and Stuedlein (2014b). The static soil resistance increased further over the last segment of the pipe because of the increase in casing friction resistance associated with additional embedment, accumulation of spoils, and the termination of the use of lubrication. ...
Article
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. (C) 2014 American Society of Civil Engineers.
... However, it is not likely that excess pore pressures was developed during shearing of the soil along the wetted pipe interface because of the high hydraulic conductivity of the sand and gravel penetrated. Meskele and Stuedlein (2015a, 2015b describe the factors affecting the static soil resistance and impact of hammer-pipe connection on energy transfer in pipe-ramming installations in detail, respectively. ...
... This resulted in energy inefficiencies owing to the large number of frictional interfaces in the pipe-hammer connection. Interested readers are referred to Meskele and Stuedlein (2015a) for a detailed discussion of hammer-pipe energy transfer. The second-moment sample statistics of the observed energy transfer efficiencies observed during the pipe installation and for the two hammers were determined by fitting the energy observations to Gaussian (i.e., normal) distributions. ...
Article
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.
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An accurate estimation of the jacking forces likely to be experienced during microtunnelling is a key design concern for the design of pipe segments, the location of intermediate jacking stations and the efficacy of the pipe jacking project itself. This paper presents a Bayesian updating approach for the prediction of jacking forces during microtunnelling. The proposed framework is applied to two pipe jacking case histories completed in the UK including a 275 m drive in silt and silty sand and a 1237 m drive in mudstone. To benchmark the Bayesian predictions, a ‘classical’ optimisation technique, namely genetic algorithms, is also implemented. The results show that predictions of pipe jacking forces using the prior best estimate of model input parameters provide a significant over-prediction of the monitored jacking forces for both drives. This highlights the difficulty in capturing the complex geotechnical conditions during tunnelling within prescriptive design approaches and the importance of robust back-analysis techniques. Bayesian updating is also shown to be a very effective option where significant improvements in the mean predictions, and associated variance, of the total jacking force are obtained as more data is acquired from the drive.
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In focus is improvement of hole-making technology by vibro hammer pushing with batch-wise removal of soil core while a pipe is driven in soil under impact loading. The important advantage of the technology is the concurrent pipe driving and soil core removal. The minimal air pressure required to separate a core and transport it along the pipe is determined. The frequency of soil core separation and transport during vibro-hammer driving of pipes in soil has been tested in underground construction of utilities. The tests prove the possibility to cut-down time of trenchless construction of underground passages and to raise the level of mechanization of the operations.
Article
Full-text available
A method is presented for determining the axial static pile capacity from dynamic measurements of force and acceleration made under the impact of a large hammer. The basic equation for calculation of the forces resisting pile penetration is derived. With the availability of this derivation, it is possible to prove that the Case Pile Wave Analysis Program (CAPWAP) resistance force distribution is unique. Using the assumption that the resistance to penetration can be divided into static and dynamic parts, an expression is developed for calculating the dynamic resistance to penetration. The resulting method requires the selection of a damping constant which is shown empirically, to relate to soil size distribution. A correlation of Case Method capacity and the capacity observed in static load tests is given for 69 statically tested piles that were also tested dynamically.
Article
During recent years wave analyses, or analyses of the elastic pile, were utilized with increasing frequency for both pile design and construction control. These methods range from purely analytical to experimental. This paper presents a review of available analytical methods and gives examples both of equipment used for measurements and of results obtained.
Article
The soil model used for wave equation analysis of pile driving has undergone little development since it was introduced by E. A. L. Smith over 25 years ago. Research efforts have concentrated on improving estimates of the required soil parameters, the limiting resistant R(max), quake Q and damping factor J. Recently an improved soil model has been developed, with full account being taken of inertial effects in the soil around the pile. These effects may still be modelled using a simple spring and dashpot analogue, but now with parameters derived in terms of fundamental soil properties. Results obtained using the new soil model are presented and compared with results from more rigorous finite element analyses, and also with field measurements of pile response during driving. Refs.
Article
Installation of new buried pipes and culverts, and replacement of existing ones utilizing trenchless technologies, is increasing in popularity because these methods mitigate many of the surface disturbances associated with conventional open-cut placement. Pipe ramming is an efficient technique that allows installation of casings in soils that can present difficulties for other trenchless technologies. Despite increasing usage, little technical guidance is available to owners and engineers who plan installations with pipe ramming. This paper provides an overview of the pipe ramming technique, possible design procedures, and governing mechanics associated with pipe ramming, with the goal of providing a baseline for engineered installations and identifying areas for further research. Methods to estimate soil resistance to ramming, analysis of ground deformations, and ground vibrations are discussed and compared with measurements observed in field installations. Soil resistance predictions based on conventional jacking methods are shown to underpredict measured resistances inferred from dynamic load testing. Empirical Gaussian settlement models commonly employed in tunnel engineering were shown to result in somewhat inaccurate predictions for an observed pipe ramming installation in cohesionless soils. Field measurements of the ground vibrations resulting from ramming are presented and compared with commonly used safe vibration standards developed for residential structures; the frequencies of vibration generally range from 20-100 Hz, are considerably high for small source-to-site distances, and attenuate rapidly with radial distance. In general, the study lays a basis for planning pipe installation projects with the intent of providing technical advancement in pipe ramming.
Article
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. (C) 2014 American Society of Civil Engineers.
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An automated prediction scheme is presented which utilizes both force and acceleration records measured at the pile top during driving to compute the soil resistance forces acting along the pile. The distribution of these forces is determined, and the dynamic and static resistance forces are distinguished such that a prediction of a theoretical static load versus penetration curve is possible. As a theoretical basis stress wave theory is used, derived from the general solution of the linear one-dimensional wave equation. As a means of calculating the dynamic pile response, a lumped mass pile model is devised and solved by the Newmark β-method. Wave theory is also employed to develop a simple method for computing static bearing capacity from acceleration and force measurements. Twenty-four pile tests are reported, 14 of them with special instrumentation, i.e., strain gages along the pile below grade. The piles tested were of 12-in. (30-cm) diameter steel pipe with lengths ranging from 33 ft. to 83 ft. (10 m to 25 m).
Article
A one-dimensional wave equation model for pile-driving analysis is presented. In this model, the pile is represented by discrete elements, while the soil is represented by a series of springs and dashpots, the coefficients of which are derived using elasto-dynamic theory. The soil model incorporates the loss of wave energy to the soil through radiation or geometric damping. In addition, the effect of the increase in soil resistance to failure when subjected to rapid loading is taken into account. The capability of the proposed model is demonstrated by comparison with field data of two instrumented piles. The analyses include predictions of set, and driving stresses at various levels of the piles. Comparisons are made with the sets and driving stresses predicted by the Smith (1960) model. From the analyses by the proposed model and load test results, estimations of soil setup for the two piles are also presented.
Traditional methods of underground utility installation and replacement generally employ conventional open cut methods. These trenching methods in most urbanized settings typically create road closures, traffic delays, unnecessary detours, loss of access to homes and business, unsightliness, noise, and general disruption. Faced with population growth and an aging underground utility system, China has looked to emerging technologies to assist in providing sustainable solutions to addressing this situation. Three trenchless construction methods that have currently been adopted in China are horizontal directional drilling (HDD), pipe bursting, and pipe ramming. HDD is a technique that enables the installation of conduits and pipelines with minimum need for open-cut surface excavation. Pipe bursting is an accepted method for trenchless pipe replacement where an existing sewer or utility pipeline is replaced with a totally new structural pipe of equal or greater inside diameter. Pipe ramming is an established technology that provides a cost efficient alternative for placing steel casings under roads, railroads, finished landscapes, and structures. This paper describes each of the three trenchless construction methods and discusses several applications for sustaining underground utility networks through case histories of successful projects in China.
Bearing capacity of piles from dynamic measurements
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