Pipejacking is a tunnel construction technique which is increasing in popularity, but fundamental research is necessary to fully understand the extent of its possible uses and limitations. This dissertation reports on laboratory research into the performance of reinforced concrete pipes, assessment of pipe joints and the use of joint packing materials. The research has addressed specific problems which the tunnelling fraternity have raised. Model pipes have been constructed at scales of 1:6 and 1:10.5 using reinforced microconcrete and they have been tested in either a sand filled chamber or between supporting yokes. Current British Standard tests have been used as a control on the quality of pipe manufacture. Data have been recorded of changes in soil pressures, pipe geometry and strains induced in the pipes. The tests have investigated deformation of pipes, deflection angles between consecutive pipes, distribution of stress concentrations and the effects of the use of joint packing materials on allowable jacking loads and induced stress magnitudes in the pipes. A review of current pipejacking practice is presented and recommendations for the control and supervision of pipejacking operations are made. The conclusions include recommendations for fieldwork monitoring and implications of this stage of the research to industry. Recommendations are made for maximum installation jacking loads for any given deflection angle between pipes. The prediction of friction angles at the pipe soil interface have been assessed at different soil stress levels and new recommendations are made. The effects of cyclic loading on the pipejacking system and transfer from jacking load to ground loading once the pipes are installed are presented. The criteria used in the selection of a recommended joint packing material for use in jacking operations have been included. Failure modes of pipes are stated and recommendations are made for pipe design, installation and monitoring to predict and prevent such failures. This dissertation is the report on the first stage of an overall programme of research which is now set to progress with monitoring of pipejacking operations on several construction sites.

While much money and effort has been spent by manufacturers and users of pipe jacking equipment to develop suitable techniques, this work appears to be the first to study the method at full scale, in a scientific research programme. It has involved monitoring a series of five pipe jacks during construction. In each case a heavily instrumented pipe was incorporated into the pipe string to measure pipe joint stresses, pipe and joint compressions and contact stresses between pipe and ground. Total jacking loads and movements of the pipe string were also measured and all results correlated with a detailed site log, full tunnel alignment surveys, and observed ground conditions. The success of the site monitoring has been highly dependent upon the development of a suitable instrumentation and data acquisition system in conjunction with appropriate site procedures for working in the restricted and physically demanding pipe jack environment without undue disruption to normal site operations. The build up of total jacking force is the result of highly complex soil-pipe interaction. The local interface stresses are essentially frictional in most ground conditions, and can be related to the shear strength of the ground. The problem is in determining the effective radial stresses which are affected by soil insitu stresses, stiffness and strength; groundwater conditions; rate of progress; pipeline misalignment and use of lubricants. Relations between pressure distributions at pipe joints and measured tunnel alignments are presented. That small angular deviations between successive pipes cause severe localisation of stresses on their ends is clearly demonstrated. Careful back analysis shows that the linear stress approach of the Concrete Pipe Association of Australia can adequately match the measured stresses and could be used by pipe manufacturers to provide design data on allowable jacking forces for pipes on the basis of pipe size, packer properties, concrete strength and angular alignment. It is also clear from the small pipe barrel stresses that improved packing materials would allow more of the potential strength of pipes to be achieved. Since relative angular than absolute deviations control transfer mechanisms between pipes, uncritical adherence to specifications based on absolute line and level is counter-productive.

Pipe jacking is a trenchless construction technique for the installation of underground pipelines. Although pipe jacking is widely used, fundamental research is still needed to understand fully the factors affecting the process and to prevent unexpected failure. With the time and financial limitation, it is difficult to explore all aspects of these factors with experiments; and it is also difficult to study them by analytical methods because of the complexity of the problem. This thesis describes the use of the finite element technique to study the pipe performance under different environments and the laboratory tests of several different joint designs. The emphasis of the current research is on the performance of the concrete pipes during jacking under working conditions and to seek possible improvements in the design of pipes and pipe joints by numerical modelling. In the finite element modelling, a simplified two-dimensional model is used for a preliminary study, then the analyses are carried out with three-dimensional models A, B and C representing a complete pipe, a pipe with surrounding soil and a symmetric three-pipe system respectively. Several factors affecting the pipe performance have been examined, for example, the properties of the packing material, the stiffness of the surrounding soil, the misalignment angle at the pipe joint, and the interaction between the pipe and surrounding soil. The numerical results show that the misalignment of the pipe is the dominating factor inducing both tensile stresses and localized compressive stresses in the concrete pipe, especially with a high misalignment angle which results in separation between packing material and the pipe. The packing materials with high Poisson's ratio and high stiffness also induce higher tensile stresses in the pipe, and the influence of Poisson's ratio is significant. Under 'diagonal' loading, both the stiffness of the surrounding soil and the interaction between the pipe and the surrounding soil have a significant effect on the stresses within the concrete pipe. Under 'edge' loading, the greatest potential damage is at the pipe joint due to the tensile stresses in the hoop direction; while under 'diagonal' loading, the damage is most likely the cracking on the external surface of the pipe along a line connecting the two diagonal loaded corners. The results show that the Australian model gives somewhat good prediction about the maximum normal stress and the diametrical contact width at pipe joint. Based on the numerical results, several different joint designs for improving the pipe strength have been proposed and tested in the laboratory. Both the laboratory tests and the back analyses suggest that the local reinforcement and the local prestressed band at the pipe joint will improve the pipe strength.

The reported work constituted the third phase of a programme of research into the performance of concrete pipes during installation by the pipe-jacked tunnelling technique. This third stage was a continuation of the on-site monitoring of full-scale pipe jacks during construction. Four schemes were monitored in different ground conditions: London clay, dense fine sand below the water table, stiff glacial till and soft alluvial clay. Pipe sizes ranged from 1000mm to 1800mm internal diameter and excavation methods included hand tools, slurry machines and an open face tunnel boring machine. The main objective was to collect information on jacking loads and stresses at the pipe-soil interface to provide a better basis for future designs. This was achieved by building twelve stress cells -capable of measuring total normal stresses, shear stresses and pore pressures - into the wall of a standard concrete jacking pipe that could be inserted anywhere in the pipe string. Jacking loads and forward movement of the pipe string were simultaneously recorded and the results were correlated against site activities, including lubrication operations, and tunnel alignment surveys. Another objective was to monitor the ground response by measuring displacements around the tunnel and ground pressures above the perpendicular to the intended line. Ground movements were measured using conventional surveying techniques for surface settlements, and inclinometer access tubes for sub-surface deformation. On one scheme, electro-levels were employed in a near-horizontal tube to measure centre line settlement as the tunnel bore advanced. Push-in spade cells and pneumatic piezometers were installed on two schemes to measure the change in horizontal pressures with the passage of the shield. Because of the myriad data collected, it has only been possible to present a summary of the results obtained. Jacking force records from all the monitored schemes - including the previous fieldwork stage - are presented. The pattern of jacking load build up and the magnitude of frictional resistance can differ significantly according to the type of ground and use of lubricants. Stress measurements at the pipe-soil interface show that the interaction between jacking loads, pipeline misalignment, stoppages, lubrication, excavation technique etc, is highly complex. Ground movement measurements compared to well established empirical predictive methods show that short-term displacements are related to ground losses caused by closure of the overbreak void between shield and pipe.

The frictional behavior of soil-construction material interfaces is of significant importance in geotechnical engineering applications such as retaining structures, pile foundations, geosynthetic liners, and trenchless technologies. Since most failures initiate and develop on the interfaces, special attention is required to predict the capacity of these weak planes in the particular application. Pipe-jacking and microtunneling technologies are being more widely used over the past decade and there is significant interest to predict the jacking forces and jacking distances achievable in order to achieve more efficient design and construction. This study focuses on the evaluation of the frictional characteristics and factors affecting the shear strength of pipe-soil interfaces. Eight different pipes made from fiber reinforced polymer (FRP), polycrete, steel, concrete, and vitrified clay were tested in the experimental program. For this purpose, a new apparatus was designed to conduct conventional interface direct shear testing on pipes of different curvature. This device allows coupons cut from actual conduits and pipes to be tested in the laboratory under controlled conditions. The apparatus includes a double-wall shear box, the inner wall of which is interchangeable to allow for testing against surfaces of different curvatures. By considering a narrow width section, the circular interface of pipes was approximated with a surface along the axial direction and the boundary is defined by the inner box. Roughness tests were performed using a stylus profilometer to quantify the surface characteristics of the individual pipes and relate these to the interface shear behavior. The surface topography showed different degrees of variability for the different pipes. To extend the range of roughness values tested and force the failure to occur in the particulate media adjacent to the interface, two artificial pipe surfaces were created using rough sandpapers. Interface shear tests were performed using the new apparatus with air-pluviated dense specimens of Ottawa 20/30 sand. Additional tests were performed using Atlanta blasting sand to evaluate the effect of particle angularity. The effect of normal stress and relative density were also examined. The interface strength was shown to increase with surface roughness and finally reach a constant value above a certain critical roughness value, which corresponded to the internal strength of the soil itself. This represented the failure location moving from the interface into the soil adjacent to the interface. Both the strength and the shearing mechanism were thus affected by the surface topography. It was also shown that the interface shear strength was affected by particle angularity, relative density and normal stress.

Pipe jacking, has seen a rise in popularity, particularly in urban areas where infrastructure does not permit cut-and-cover methods. As pipe jacking has becomes more commonplace, engineers are pushing the limits of the technology more and more by designing longer drives in more difficult ground conditions. Lubrication is essential to reduce the frictional resistance generated at the pipe-soil interface. Even though lubrication is widely utilized, there is not a clear understanding of the conditions required to obtain the full benefit of lubrication. This dissertation focuses on bentonite slurry characteristics and interface behavior under different lubricating conditions with the goal to further the understanding of the mechanisms responsible for the large friction reductions observed in the field. An interface shear device capable of measuring interface behavior on pipe surfaces was used to perform tests under two lubricating conditions. Pipes were sheared against a mixture of sand and slurry and the effect of the slurry was quantified. In another series of tests, slurry was injected at the pipe-soil interface. An axisymmetric interface shear device was developed to further investigate the lubrication mechanism associated with injection of slurry into sand. The device was designed to inject slurry through injection ports built into a shaft displaced within a sealed sand-filled chamber. A series of tests were performed on dry sand as well as sand where water or slurry was injected during shearing. The effect of sand type and viscosity are also investigated. Findings from the experimental studies are related back to full-scale behavior with the objective of assessing the lubrication methods and their effectiveness. A rational procedure for predicting non-lubricated and lubricated jacking forces is proposed to optimize design and serve as a framework for evaluating jacking forces in the field.