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.

The behavior of unsaturated soils depends heavily on material properties and soil conditions. In Geotechnical Engineering, compacted soils are frequently used as fill material, and quality control is vital to the construction process. There are few methods available to estimate the parameters associated with unsaturated soils based on field measurements, and a relationship between these factors could reduce testing time and lower construction costs. Undrained triaxial tests were performed on four clays representing a range of material properties in an effort to reach the maximum dry density, which provides the highest bearing capacity. Each clay was compacted at optimum moisture content, as well as wet and dry of optimum. Measurements were taken using the GeoGauge and shear wave velocities. An empirical approach was used to estimate the effect of a density gradient on soil suction. A relationship between the normal stress and matric suction produced a strong trend when plotted against a function of stiffness and the void ratio, which represents a density gradient. Another relationship between the GeoGauge and shear wave stiffness measurements was found, but no relationship with the material properties of the samples was observed, indicating that more in-depth research is needed to find a stronger relationship.

In the past decade, the grouting industry has made significant technological advancements in real-time monitoring of flow rate and pressure of pumped grout, stable grout mix design, and with grout curtain concepts dealing with placement and orientation. While these practices have resulted in improved construction practices in the grouting industry, current design guidelines for grout curtains are still predominately based on qualitative measures such as engineering judgment and experience or are based on proprietary methods. This research focused on the development of quantitative guidelines to evaluate the effectiveness of a grout curtain in porous media using piezometric and hydraulic flow data. In this study, a laboratory-scale physical seepage model was developed to aid in the understanding and development methodology to evaluate the effectiveness of a grout curtain. A new performance parameter was developed based on a normalization scheme that utilized the area of the grout curtain and the area of the improved media. The normalization scheme combined with model-based Lugeon values that correspond to pore pressure and flow rate measurements at different soil unit weights and grout curtain spacings, produced a mathematical equation that can be used to quantify the effectiveness of a grout curtain. This study found a relationship that takes into account soil unit weight, grout curtain spacing and a new performance parameter that can be used to help predict the effectiveness of a grout curtain.

As an abundant sedimentary rock, shale is widely used as construction material around the world. However, shale is a fissile and laminated material and is therefore subject to deterioration due to environmental and chemical forces (i.e., weathering), which is possible to cause high maintenance cost on associated structures and failures of earth slopes and embankments. However, currently, there is lack of efficient method to monitor the weathering process of shale. This thesis uses several shale samples collected from the commonwealth of Kentucky to study the deformation and shear behaviors of weathered compacted shale. A new electrical approach was developed to access the deformation behavior of shale. The long term deformation behaviors, such as collapse and swell can be predicted from specific electrical parameters. The critical state theory was used to describe the shear behavior of weathered compacted shale. Some findings observed by previous researchers were confirmed, and new empirical equations were provided to estimate the shear strength parameters of weathered compacted shale.

Grouting techniques have been in used for many years, but several new grout materials have surfaced in recent decades that have re-defined the boundaries of the limitations of grouting programs. Typically these applications are used for seepage control in earthen impoundments, but strength of these earthen impoundments should be considered where there is potential for movement in the grouted soil mass. This study investigated initial conditions that could affect grout application effectiveness. The initial conditions in question were soil grain size and in situ moisture content. Two grouts were used, ultrafine and acrylate, and variations in pure grout properties were studied. An apparatus was developed so that a uniform grout could penetrate the pore spaces of a soil specimen. The rate of penetration of the grout into the soil was studied. The unconfined compressive strength of the resulting grouted soil was then analyzed. In testing neat ultrafine grout, it was shown that increased water-to-cement ratios had negative effects on the stability of the grout. Increasing the water-to-cement ratio from 0.5 to 2.5 resulted in a decrease in strength by a factor of 100. An inhibitor chemical was used to increase the time for reaction in the acrylate grout. During the chemical reaction, the curing temperature and gel times were monitored. A grout mix was selected for the acrylate grout that achieved appropriate gel times. In general, this study found that the grout penetrations rates into the soil increased as the initial moisture was increased from dry conditions to a gravimetric moisture content of nine percent. In each study, increased initial moisture decreased the grouted soil strength, with decreases in strength exceeding 50 percent. Empirical relationships were realized when compared to the initial matric suction of the soil. This suggests initial matric suction may be a useful initial condition for estimating increases in soil strength upon implementation of a grouting program for both the acrylate and ultrafine grouts.

This thesis is a theoretical study, using both finite element and boundary element methods, of the behaviour of single-piles and pile groups under vertical and lateral loading. It offers an improved understanding of the soil-structure interaction that occurs in pile groups, particularly closely spaced piles subjected to lateral loads. The potential of a two- dimensional idealisation of what is a three-dimensional problem is demonstrated by achieving real insight into the complex nature of pile-soil and pile-soil-pile interaction in pile groups. A new load transfer mechanism is presented for a rigid, axially loaded vertical pile. From this an improvement is then derived to the analytical solution for pile head settlement given by Randolph and Wroth (1978). The improved mechanism has the further merit that it can be applied also to solutions for flexible piles and pile groups. The improved analytical solution is further adapted in the development of two correcting layers specifically for vertically loaded piles to model infinite boundaries in the finite element model. The correcting layers help in establishing superiority of the finite element method over the boundary element method. To model pile-soil interaction, a purely cohesive interface element is developed and then validated by performing various two-dimensional test problems, including stability analysis of flat surface footings. Footing-soil interface tension is successfully modelled in this way - an outcome that entails a significant modification to the Hansen (1970) bearing capacity solution. Stability analysis is also carried out of conical footings using a three-dimensional finite element model: the results help to explain the applicability of the existing bearing capacity theories to conical footings. The ultimate lateral soil reaction is determined and various pile loading stages are investigated through parametric studies. Study of the stage immediately following pile installation (i.e. the consolidation stage) highlights the need to develop an effective stress analysis for laterally loaded piles. Pile-soil interaction is studied using the cohesive interface element presented earlier, which proves to be quite successful in smoothing out the stress discontinuities around the pile. A new material model for frictional soils is presented, and validated by using it to model an extension test: it captures well post-peak behaviour and takes care of the effects of dilation on the response of laterally loaded piles. Finally, mechanisms of interaction in closely spaced pile groups are studied. Simple analytical expressions are derived which quantify the effects of interaction. A new method of analysis is presented for single-piles and pile groups which offers a considerable degree of reliability without having to do either impossibly expensive full scale field tests or prohibitively expensive full three-dimensional analysis using the currently available computers.

Simple unpaved roads consist of a layer of coarse granular material placed directly onto the surface of weak or compressible ground. It is thought that the construction of such roads can be considerably improved by the incorporation of a geogrid at the base of the granular fill layer. Geogrids are a type of geotextile, distinguished by their relatively large aperture size. Laying out a geogrid on the surface of the ground before placing the fill layer may in many cases allow a reduced thickness of fill material to be used, and may also substantially increase the load required to cause a complete failure of the system. No generally accepted design method exists for the construction of reinforced unpaved roads, due to the complex mechanisms which govern deformations in the system. The primary aim of this dissertation was to investigate the performance, in such a construction, of a particular geogrid, namely Tensar, manufactured by Netlon Ltd. A detailed model study into failure mechanisms was undertaken using laboratory apparatus constructed to conduct work at 1/4 full scale. Simple plane-strain, monotonic footing tests were carried out on systems consisting of a fill layer compacted onto a consolidated clay subgrade, both with and without the incorporation of a model grid at their interface. The testing technique included a comprehensive study of photographs taken of marker movements in the clay through the transparent sides of the test-box during tests. The relevant failure mechanisms associated with reinforced and unreinforced systems were established. In addition the significance of shear stresses acting at the subgrade surface was recognised and a concept whereby the appropriate subgrade bearing capacity factor is related to these shear stresses was developed. The modelling techniques adopted in this work obviated the need for a centrifuge.

The cone pressuremeter is an in situ testing device comprising a pressuremeter mounted behind a cone penetrometer of the same diameter. Previously reported tests had indicated that the cone pressuremeter can provide measurements of soil strength, stiffness and in situ stress. The study presented in this thesis is aimed at developing methods of interpretation of the cone pressuremeter that can be applied with confidence to a variety of soil types. Carbonate sands have been the cause of significant problems associated with the design of foundations for offshore structures. A programme of cone pressuremeter testing in a carbonate sand from the west coast of Ireland is presented. Tests were carried out in a calibration chamber where conditions of vertical and horizontal stress and relative density were controlled. The influence of these parameters on measured values of cone resistance and pressuremeter limit pressure is assessed. Similar tests were also carried out in a felspathic sand, and correlations have been presented for deriving horizontal stress and relative density that are applicable to most types of sand. The influence of creep strains and of overconsolidation were other features of carbonate sand that have been assessed with the cone pressuremeter. A numerical model which accounts for the crushing characteristics of carbonate sand is presented, and is shown to improve significantly predictions of limit pressure measured in the calibration chamber. Cone pressuremeter tests were carried out in soft clay at the Bothkennar test site in Scotland. An analysis based upon cavity expansion theory was shown to provide good estimates of undrained shear strength and stiffness compared with results from other in situ and laboratory tests. Estimates of the in situ horizontal stress were found to be unrealistically high. Shear modulus in both sand and clay has been measured from unload-reload cycles carried out during pressuremeter expansion. The stress levels and strain amplitudes of these cycles have been shown to influence the shear modulus greatly. In sand, a procedure for relating these moduli to those at an extremely small reference strain is presented. In clay, shear moduli are shown to give a remarkably close agreement to others reported from Bothkennar, when due account of the strain amplitude is made. Finally, a time/cost analysis between the cone pressuremeter, the cone penetrometer and the self-boring pressuremeter is presented. The cone pressuremeter is found to be a cost-effective device bearing in mind the amount and quality of information it can provide.

The main purpose of this thesis is the development of a new constitutive soil model emphasising the use of thermodynamic principles. This new approach to plasticity modelling, termed ‘hyperplasticity’, was first developed by Collins and Houlsby (1997) and Houlsby and Puzrin (2000). This idea has been further extended to continuous hyperplasticity in which smooth transitions between elastic and plastic behaviour can be modelled (Puzrin and Houlsby, 2001b). Applying hyperplasticity to this research, a kinematic hardening model specified by means of two scalar functionals is used to accommodate the effect of stress history on stiffness. A rate-dependent calculation for an approximation of the incremental stress-strain response is introduced. The model developed in the research is named ‘kinematic hardening modified Cam-clay (KHMCC) model’ and requires eight parameters (plus an extra parameter for rate-dependent analysis). Triaxial test results from the Asian Institute of Technology (AIT) and cyclic undrained triaxial data from Chulalongkorn University are employed to establish the soil parameters for the new model. The model is initially developed in terms of triaxial stress-strain parameters for the purpose of comparison with the experimental data on Bangkok clay. The model is expressed in FORTRAN code for implementation into the OXFEM finite element program. Two examples of real geotechnical projects in Bangkok (a road embankment and tunnelling in soft ground) are analysed under plane strain conditions. Comparisons of the numerical analysis results with field data are made. In addition, factors affecting the results of the analysis such as stress history and K0, are investigated.

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.