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Abstract

In recent years, there has been an increased resort to microtunnelling/pipe-jacking as a means of constructing underground conduits (for water, sewage, gas, and other utilities) to avoid on-street disruption in urban areas. In this paper, technical details of two 1 200 mm internal diameter microtunnels in silty sand totalling over 550 m in length are discussed. While average skin friction values are extremely low for both drives suggesting effective lubrication practice, differences in normalised bentonite volumes appear to be responsible for differences in skin friction. Full or near full buoyancy of the pipeline has been demonstrated for the majority of the drive. The frictional stress increase after a stoppage is shown to depend on stoppage duration but also on the normalised lubriation volume. Interpretation of data in the manner presented in the paper is an important means of assimilating experience of microtunnelling in different ground conditions.

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... The jacking force is determined by the friction resistance on the outer surface of the pipe when it crosses the soil layer. To reduce the frictional resistance on the outer wall of the pipe during jacking, thixotropic mud is usually injected on the outer surface of the pipe to reduce drag (Norris, 1992;Milligan and Marshall, 1998;Pellet-Beaucour and Kastner, 2002;Khazaei et al., 2006;Boulanger and Wong, 2016;Namli and Guler, 2017;Cheng et al., 2019;O'Dwyer et al., 2019). The thixotropic mud will change the mechanical properties of the original soil and pipe interface, and consequently have a substantial impact on the mechanical response of pipe jacking. ...
... At this time, the equipment may be damaged or the pipe may be broken due to the incorrect calculation of the jacking force. At present, there are few studies on this problem, and these studies only analyze the change in the jacking force after the restart of pipe jacking (Pellet-Beaucour and Kastner, 2002;Cheng et al., 2017;Zhang et al., 2017;O'Dwyer et al., 2019). It has not been studied in depth in the mechanism of the sharp rise of the jacking force caused by restart after the stagnation of pipe jacking and the mechanical properties of the interface after being restarted. ...
... In the direct shear experiment, the pipe-soil friction coefficient increases with the longer stagnation time, and consequently the jacking force of the concrete pipe when restarting increases with the longer stagnation time, which is consistent with the on-site monitoring results of many pipe jacking projects (Pellet-Beaucour and Kastner, 2002;Curran and McCabe, 2011;Cheng et al., 2017;Zhang et al., 2017;O'Dwyer et al., 2019). The direct shear test shows that the increase of the friction coefficient is closely related to the increase of the gravelly sand particles on the shear surface. ...
Article
Full-text available
In the process of long-distance and large-diameter pipe jacking, thixotropic mud is generally injected into the outer surface of the pipe wall to reduce the frictional resistance between the pipe and the soil. The process of pipe jacking may be stopped due to various reasons such as pipe rupture and equipment damage. When the pipe is restarted after being stopped for a period of time, the interface mechanical properties usually change substantially, resulting in a substantial increase in frictional resistance compared to before the stop. However, the mechanical properties and shear mechanism of the pipe-soil interface after jacking is restarted have not been sufficiently investigated. In this paper, a series of gravelly sand-concrete direct shear tests are carried out, in which lubricant is injected into the interface between gravelly sand and concrete, and the effect of construction stagnation time is considered. The mechanical properties of the interface when the concrete pipe is restarted after stagnation is studied by the direct shear tests. The results show that the friction coefficient of pipe-soil interface increases with the stagnation time, which is determined by the thixotropic mud state and the content of gravelly sand involved in shear. In a short period of stagnation, the friction coefficient is determined by the cohesion caused by thixotropic mud and the friction angle produced by the gravelly sand involved in the shearing action. With the increase of stagnation time, the friction angle gradually becomes the decisive factor for the increase of friction coefficient.
... For example, lubricant injected at the pipe-soil interface is used to minimize F s through a reduction in the effective weight of the pipe string, stabilization of the tunnel bore, and reduction of the pipe-soil interface friction (Milligan and Marshall 1998;Pellet-Beaucour and Kastner 2002;O'Dwyer et al. 2018). In contrast, work stoppages typically cause significant peaks in the jacking force upon resumption of tunneling (e.g., Norris and Milligan 1992;Pellet-Beaucour and Kastner 2002;Meskele and Stuedlein 2015;Cheng et al. 2017;Shi et al. 2018;O'Dwyer et al. 2019). Although a significant body of research conducted over the last 30 years has greatly enhanced our understanding of these effects and their influence on F T , the literature contains many examples by which static rule-based design methods fail to provide a satisfactory prediction of the field behavior (e.g., Norris and Milligan 1992;Rahjoo et al. 2012;Reilly and Orr 2012;Choo and Ong 2015;Barla et al. 2006;Sheil et al. 2016). ...
... The development of the total jacking force with jacked distance is shown in Fig. 10(a). Unusually high jacking forces are evident toward the end of the drive where the TBM was reported to have encountered and broken through the reception shaft (O'Dwyer et al. 2018(O'Dwyer et al. , 2019; therefore, the corresponding datapoints have been classed as abnormal. The raw data in Fig. 10(a) have also been transformed into the feature space shown in Fig. 10(b) employing the STL decomposition [Eq. ...
... 9. The reader is referred toO'Dwyer et al. (2018O'Dwyer et al. ( , 2019 for additional details on the project. ...
Article
The proliferation of data collected by modern tunnel boring machines presents a substantial opportunity for the application of data-driven anomaly detection (AD) techniques that can adapt dynamically to site specific conditions. Based on jacking forces measured during microtunnelling, this paper explores the potential for AD methods to provide more accurate and robust detection of incipient faults. A selection of the most popular AD methods proposed in the literature, comprising both clusteringand regression-based techniques, are considered for this purpose. The relative merits of each approach is assessed through comparisons to three microtunnelling case histories where anomalous jacking force behaviour was encountered. The results highlight an exciting potential for the use of anomaly detection techniques to reduce unplanned downtimes and operation costs.
... However, the use of slurry makes it more complex to calculate or predict the friction resistance because of the change in contact conditions between the pipe and soil and lubricant slurry. The new contact state, which is due to the pipe-soilslurry interaction, is affected by factors such as pipe diameter, soil properties, overcut [3,9], lubrication efficiency [9], pipeline misalignments [10,[14][15][16], and stoppages [9,14,[17][18][19]. The existing prediction models have not fully taken these factors into consideration, leading to an overestimation or underestimation of the friction resistance [9,[20][21][22][23]. ...
... In pipe jacking, the linear factors to generate friction resistance are due to the weight of pipe (f W ), soil pressure (f s ), slurry pressure (f m ), pipe-soil cohesion (f sc ), and pipe-slurry cohesion (f mc ). Their equations can be expressed as [5,6,9,10,14,19,21,22,25,26]. ...
... To calculate Equation (18), the vertical soil stress σ v has to be first determined. It is noted that at the present time, by far the most commonly used model for soil pressure calculation is Terzaghi's silo model (Equation (22)) [5,6,9,19,21,26]. According to Equation (22), the calculation of the vertical soil stress requires some physical parameters that may be determined with some accuracy, such as the height of cover h, the cohesion c s , and the unit weight of soil γ, but also some empirical parameters, such as b, δ, and K. ...
Article
Full-text available
Friction resistance usually constitutes one of the two main components for the calculation of required jacking force. This paper provides a new approach to predict the friction resistance of slurry pipe jacking. First, the existing prediction equations and their establishment methods and essential hypotheses used were carefully summarized and compared, providing good foundations for the establishment of the new model. It was found that the friction resistance can be uniformly calculated by multiplying an effective friction coefficient and the normal force acting on the external surface of the pipe. This effective friction coefficient is introduced to reflect the effect of contact state of pipe-soil-slurry, highly affected by the effect of lubrication and the interaction of pipe-soil-slurry. The critical quantity of pipe-soil contact angle (or width) involved may be calculated by Persson’s contact model. Then, the equation of normal force was rederived and determined, in which the vertical soil stress should be calculated by Terzaghi’s silo model with parameters proposed by the UK Pipe Jacking Association. Different from the existing prediction models, this new approach has taken into full consideration the effect of lubrication, soil properties (such as internal friction angle, cohesion, and void ratio), and design parameters (such as buried depth, overcut, and pipe diameter). In addition, four field cases and a numerical simulation case with various soils and design parameters were carefully selected to check out the capability of the new model. There was greater satisfaction with the measured data as compared to the existing models and the numerical simulation approach, indicating that the new approach not only has higher accuracy but is also more flexible and has a wider applicability. Finally, the influence of buried depth, overcut, and pipe diameter on the friction resistance and lubrication efficiency were analyzed, and the results can be helpful for the future design.
... Therefore, quality control measures (such as frequent calibration, maintenance, replacement of measurement equipment) need to be implemented by tunnelling operators to ensure that the data are of sufficient quality to unlock the potential of both backanalysis (e.g. McCabe et al., 2012;O'Dwyer et al., 2020) and machine learning in contributing to our understanding of tunnelling processes. ...
... However, plenty of in-situ measured data indicates that pipe-surroundings contact conditions are complicated due to the axis deviation, lubrication effect, and incomplete discharge of spoil (Zhang et al., 2017a;Ji et al., 2019;Li et al., 2019;Deng et al., 2021;Deng et al., 2022). Then, the frictional resistance is related to the frictional properties of the outer pipe interface (Reilly and Orr, 2017;Li et al., 2018;O'Dwyer et al., 2019), which can be used to estimate the jacking force with theoretical calculations and numerical simulations (Pellet-Beaucour and Kastner, 2002;Shou et al., 2010;Yen and Shou, 2015;Ong and Choo, 2016;Ong and Choo, 2018;Li et al., 2019;Choo and Ong, 2020). ...
Article
Pipe sticking is frequently occurred during the pipe jacking in rock strata due to the blockages accumulated in the annulus gap. The frictional resistance induced by surrounding rocks increased sharply, and the total jacking force might exceed the pipe structural capacity. Through the in-situ monitoring and direct shear tests, the influence of the pipe sticking on the deformation and frictional properties of the steel pipe jacking was analyzed. In the severe pipe sticking, the contact pressure acting on the pipe exceeded 1 MPa, and significant radial compression took place. The hoop strain of the pipe contacting with the blockages illustrated a tensile state, while the pipe contacting with the slurry or groundwater exhibited compressive strain. In the direct shear tests, the frictional properties of the steel pipe-rock interface under five contact conditions were evaluated. Experimental results revealed that the pipe-rock friction coefficient under the blockages exhibited as high as 0.6, and the blockages in annulus gap were the main reason for the increase in frictional resistance. In addition, the causes of the pipe sticking were analyzed, and measures were implemented to resolve the pipe sticking issue.
... It is acknowledged that the magnitudes of shear stresses (crit) alluded to in Section 4.2 exceed the values of skin friction measured in field drives, where values below 1 kPa are routinely achieved with modern automated lubrication systems (e.g. Curran & McCabe, 2011;Cheng et al., 2017;O'Dwyer et al., 2020). This is because jacking pipes are designed to exploit buoyancy from the lubricant within the overcut annulus, formed as a result of the TBM having a slightly larger diameter than the pipes. ...
Conference Paper
Full-text available
In long pipe-jacking drives used for installing utility pipelines, maximum jacking load requirements are usually governed by skin friction at the pipe-soil interface. In addition, field experience has shown that transient peaks in skin friction arise upon recommencement of jacking after stoppages; these stoppage durations can be short (due to the addition of a pipe to the string) or long (due to weekend stoppages or breakdowns) and constitute a risk for pipe-jacking contractors. In this paper, the problem is replicated in the laboratory using direct shear interface tests using a concrete specimen in one half of the apparatus and sand/bentonite mixtures in the other. Once critical state conditions were reached in these tests, stoppages of various durations (from 30 mins up to 2 weeks) were incorporated and the increase in shear stress upon recommencement of shearing was noted. From the experiments, there appears to be a threshold stoppage duration beyond which the skin friction increase appears to plateau, suggestive of a time-limited process within the bentonite. These skin friction data are shown to provide an upper bound to corresponding stoppage data from pipe-jacking drives in sandy ground conditions.
... Traditionally, tunnelling contractors have relied on empiricism, in addition to more formal design calculations. While simplified design calculations play an important role in tunnel design and construction, optimising tunnelling operations remains technically challenging due to their dependence on several complex factors, such as site geology, tunnel-boring machine (TBM) operational parameters and tunnel geometry (O'Dwyer et al., 2018(O'Dwyer et al., , 2020Phillips et al., 2019). Although a significant body of research conducted over the past 30 years has greatly enhanced understanding of these effects and their influence on tunnelling operations, the literature contains many examples where static 'rule-based' design methods fail to provide satisfactory prediction of field behaviourfor example, the papers by Barla et al. (2006), Choo and Ong (2015) and Sheil et al. (2016). ...
Article
The proliferation of data collected by modern tunnel boring machines (TBMs) presents a substantial opportunity for the application of machine learning (ML) to support the decision-making process on site with timely and meaningful information. The observational method is now well-established in geotechnical engineering and has a proven potential to save time and money relative to conventional design. ML advances the traditional observational method by employing data analysis and pattern recognition techniques, predicated on the assumption of the presence of enough data to describe the modelled system’s physics. This paper presents a comprehensive review of recent advances and applications of ML to inform tunnelling construction operations with a view to increasing their potential for uptake by industry practitioners. This review has identified four main applications of machine learning to inform tunnelling, namely TBM performance prediction, tunnelling-induced settlement prediction, geological forecasting and cutterhead design optimisation. The paper concludes by summarising research trends and suggesting directions for future research for ML in the tunnelling space.
... Large-diameter open caissons are an increasingly common means of constructing underground storage and attenuation tanks, as well as launch and reception shafts for tunnelboring machines (O'Dwyer et al., 2018(O'Dwyer et al., , 2020. A 'cutting face' at the base of the caisson wall, resembling an inclined ring footing, is commonly used to aid the sinking phase. ...
Article
Large-diameter open caissons are an increasingly common means of constructing underground storage and attenuation tanks, as well as launch and reception shafts for tunnel boring machines. A ‘cutting face’ at the base of the caisson wall, resembling an inclined ring footing, is typically used to aid the sinking phase. This paper describes a suite of over 15,000 finite element limit analyses exploring the bearing capacity of a caisson cutting face, partially- or wholly-embedded in undrained soil. The primary aim of the study is to assess the influence of the cutting face inclination angle on the vertical bearing capacity. The effects of cutting face roughness, internal overburden and surcharge, and caisson radius are also investigated. In particular, the results indicate that a steepening of the inclination angle may not always reduce the bearing capacity, if the cutting face is rough. The numerical output informs the development of a closed-form approach for application in routine design. The new design method is shown to provide an excellent representation of the numerical output.
... Современный мир невозможно представить без усовершенствования способов подъема и транспортировки различных грузов. Подъемно-транспортные установки, в частности домкраты, активно применяемые в большинстве производств [1]- [4], предназначены для подъема грузов на небольшую высоту и нашли широкое применение при монтажных работах -подъемах с фиксацией как отдельных частей, так и целых сооружений и судов [5], [6]. Домкраты активно применяются на всех предприятиях, в том числе судостроительных и судоремонтных, а также в портовом хозяйстве. ...
Article
This paper describes direct shear testing of a range of sand-bentonite slurry mixes, identified as a gap in the literature. In the absence of a concrete interface, there was an apparent transition zone from sand-governed strength (bentonite content ≤30%) to clay-governed strength (bentonite content ≥80%), which was linked to the sample void ratio. When a concrete interface was introduced, the critical stress ratio (critical state shear stress normalised by the effective normal stress) was found to change linearly with bentonite slurry content, reflecting an interface sliding failure mechanism. The testing also considered the effect of shearing rates ranging from 0.0025 mm/min to 10 mm/min on interface shear strength. The mixtures containing greater bentonite slurry content displayed a greater decrease in the critical stress ratio with increasing shear rate. Very few studies have explored the influence of the relative sand-clay mix composition on interface shear resistance; these results provide a better understanding of their mechanical behaviour and forms a basis for future research in this area.
Article
When large-section rectangular pipe jacking is performed in anhydrous sand strata, due to the special geological condition and construction specification, there are specific requirements for the performance of thixotropic slurry. In this study, an optimized traditional slurry formula and a nano-modified slurry formula (with 2% nano-SiO2 added) suitable for large-section rectangular pipe jacking in anhydrous sand formations were proposed by conducting an L25 (3⁵) orthogonal test and a two-factor test, respectively. Five indicators were used to select the optimal slurry component proportion and nano-additive and additive concentration, including plastic viscosity (PV), filter loss (FL), water dissociation ratio (WDR), thixotropic value (TV) and yield point (YP). The influence of the component content on the slurry properties was analysed. To preliminarily verify the drag-reducing effect of the slurries prepared according to the formulas, an interface friction test was designed. The interface friction test results show that the optimized traditional slurry can reduce the pipe-soil friction coefficient to 64.7%, whereas the nano-modified slurry is 54.9%. Through scanning electron microscopy (SEM) observations, the micro mechanisms of the slurries were investigated. Furthermore, the formulas were applied in a practical pipe jacking project, and the jacking load and soil settlement were well controlled throughout the application period.
Article
To monitor the mechanical performance of a deep-buried rock-jacketed pipe within the scope of the Guanjingkou Water Control Project in Chongqing during construction, an extensive field experimental program was performed. The pipe–rock contact pressure, pipe deformation, and jacking load eccentricity were monitored. Regarding the pipe-rock contact pressure, the following conclusions can be drawn: (1) the magnitude was independent of the pipeline depth; (2) the maximum magnitudes were detected at the crown and decreased towards the invert due to the pipe buoyancy; (3) the magnitude was constant at the crown and sides for increasing jacking forces, whereas it increased or decreased at the invert with pipe-uplift or pipe-incrustation into the surrounding rock, respectively. With regard to the strain patterns measured on the pipe, the results demonstrated that magnitude of those was only significant for high jacking force magnitudes. The experimental approach followed and the results obtained were found to be useful for future projects because such results are rarely reported.
Article
Full-text available
This paper investigates the use of stability factors for estimating the ultimate bearing pressures on cylindrical caissons in cohesive-frictional soils. Rigorous upper and lower bound limit analyses with finite elements in axisymmetric (AX) condition are used for a series of numerical studies. The bearing capacity factors (Nc0, Nq0 and Nγ0) for a surface circular footing are firstly revisited. This is followed by a study on the effect of caisson’s embedded depth ratio (L/D). A comprehensive set of depth factors (Fcd, Fqd and Fγd) is then reported as a function of caisson’s embedded depth ratio (L/D) and soil internal friction angle (ϕ). The obtained results are compared with published solutions in the literature. Several examples are given to validate the principal of superposition as well as to illustrate on how to use the produced factors to estimate the ultimate bearing pressures on cylindrical caissons in cohesive-frictional soils. The study should be of great interests to practitioners.
Article
The use of supporting fluids to stabilise excavations is a common technique adopted in the construction industry. Rapid detection of incipient collapse for deep excavations and timely decision making are crucial to ensure safety during construction. This paper explores a hybrid framework for forecasting the collapse of fluid−supported circular excavations by combining physics-based and data-driven modelling. Finite element limit analysis is first used to develop a numerical database of stability numbers for both unsupported and fluid−supported circular excavations. The parameters considered in the modelling include excavation geometry, soil strength profile and support fluid properties. A data-driven algorithm is used to ‘learn’ the numerical results to develop a fast ‘surrogate’ amenable for integration within real−time monitoring systems. By way of example, the proposed forecasting strategy is retrospectively applied to a recent field monitoring case history where the observational method is used to update the input parameters of the data-driven surrogate.
Article
Large-diameter open caissons are an increasingly common means of constructing underground storage and attenuation tanks as well as launch and reception shafts for tunnel boring machines. The caisson walls typically feature a tapered base, referred to as the ‘cutting face’, to aid the sinking process by reducing the vertical soil reaction. The primary aim of this paper is to explore the influence of the caisson cutting face inclination angle on the vertical soil reaction in sand. Both finite element limit analysis and finite element analysis are adopted for this purpose. The effects of cutting face roughness, external embedment depth, and caisson radius are also investigated. The results show that the influence of the cutting face inclination angle on the bearing capacity is highly dependent on both the soil friction angle and the roughness of the cutting face. A reduction in the caisson radius is also shown to cause a significant increase in the vertical soil reaction. The numerical output is used to inform the development of a new closed-form analytical approach amenable for use in routine design. The design method is shown to provide a high-fidelity representation of the numerical output.
Article
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.
Article
There frequently exists inadequacy regarding the number of boreholes installed along tunnel alignment. While geophysical imaging techniques are available for pre-tunnelling geological characterization, they aim to detect specific object (e.g. water body and karst cave). There remains great motivation for the industry to develop a real-time identification technology relating complex geological conditions with the existing tunnelling parameters. This study explores the potential for the use of machine learning-based data driven approaches to identify the change in geology during tunnel excavation. Further, the feasibility for machine learning-based anomaly detection approaches to detect the development of clayey clogging is also assessed. The results of an application of the machine learning-based approaches to Xi’an Metro line 4 are presented in this paper where two tunnels buried in the water-rich sandy soils at depths of 12-14 m are excavated using a 6.288 m diameter EPB shield machine. A reasonable agreement with the measurements verifies their applicability towards widening the application horizon of machine learning-based approaches.
Article
Microtunnelling is an increasingly popular means of locating utilities below ground. The ability to predict the total jacking force requirements during a drive is highly desirable for anomaly detection, to ensure the available thrust is not exceeded, and to prevent damage to the pipe string and/or launch shaft. However, prediction of the total jacking force is complicated by site geology, the use of a lubricated overcut, work stoppages, tunnel boring machine driving style and pipe misalignment. This paper introduces a probabilistic observational approach for forecasting jacking forces during microtunnelling. Gaussian process regression is adopted for this purpose which allows forecasts to be performed within a probabilistic framework. The proposed approach is applied to two recent UK microtunnelling monitoring projects and the forecasts are appraised through comparisons to predictions determined using design methods currently applied in industry. The results show that the proposed framework provides excellent forecasts of the monitored field data and highlights a significant opportunity to complement existing prescriptive design methods with probabilistic forecasting techniques.
Article
Detecting sudden changes in geological conditions (e.g., karst cavern and fault zone) during tunnelling is a complex task. These changes can cause shield machines to jam or even induce geo-hazards such as water ingress and surface subsidence. Tunnelling parameters that relate closely to the surrounding geology have proliferated in recent years and present a substantial opportunity for the application of data-driven artificial intelligent (AI) techniques that can infer patterns from data without reference to known, or labelled, outcomes. This study explores the potential for support vector machines (SVM) to identify changes in soil type during tunnelling towards reducing the possibility of jamming and geo-hazard development. All tunnelling data were pre-processed to convert time series data into feature-based sub-series. A selection of the most popular parameter optimisation algorithms was explored to improve the accuracy of the AI predictions. Their relative merits were evaluated through comparisons with a recent pipejacking case history undertaken in gravel and clayey gravel soils. The results highlight an exciting potential for the use of optimisation algorithm-based SVMs to identify changes in soil conditions during pipejacking.
Article
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There are several well-established jacking force models available for determining the jacking loads. However, their ability to characterise the tunnel bore conditions is limited. A simple approach to characterise the tunnel bore conditions is proposed and applied to a case study where four sewer pipelines of the Shulin district sewer network in Taipei County, Taiwan were constructed to verify its validity. In this paper, four jacking force models are reviewed. Based upon the given soil properties and pipe dimensions as well as the pipe buried depth, the normal contact pressure (σ’) in each jacking force model and the measured frictional stress (τ) in each baseline section are utilised for back-analysis of the frictional coefficient (μavg). The μavg values outside the range of 0.1-0.3 recommended for lubricated drives can be attributed to the increasing pipe friction resulting from excessive pipe deviation or ground closure or due to the gravel formation not being long enough to establish lower face resistance or total jacking load. JMTA (Japan Microtunnelling Association) has indicated a further potential use in assessment of the interface performance during pipe-jacking works.
Thesis
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The use of bentonite and polymer slurries as lubricants to reduce jacking force has long been established practice in pipe jacking and microtunnelling, with reductions in the skin frictional resistance component of jacking force of up to 90% being reported. The objective of this research is to improve the understanding of the mechanisms of action of these pipe- jacking lubricants. Field case histories are presented where the influence of lubricants is shown. Laboratory studies are described where the effects of pressurised and unpressurised lubricant slurries in the interface between concrete jacking pipes and coarse- grained and fine-grained soils are quantified. A novel triaxial testing apparatus is presented, which allows for the injection of lubricants onto the interface between rough concrete and a soil that is shearing at the constant volume interface friction angle. It is shown from the results of laboratory testing that the main beneficial effect of pipe jacking lubricants is the reduction of the radial effective stress acting on the pipeline through the generation and retention of excess pore water pressure in the soil near the interface. Results are compared to field case history data and conclusions are drawn. Additionally, the jacking forces observed during two recent microtunnelling projects in rock in Ireland are presented and analysed.
Conference Paper
Full-text available
Pipe jacking force mainly consists of the penetration resistance from face pressure and the friction resistance between the pipe and soil. Jacking forces depends on several site related parameters such as alignment, pipe diameter, soil type, groundwater table, overburden, overcut, lubrication, steering corrections, and stoppage. This paper presents how the soil type affects the penetration resistance and how the misalignment affects the friction resistance. A slurry machine excavating through alluvium deposit to install a sewer line of 1.5meter diameter was selected in discrete four straight drives with similar conditions of groundwater table, overburden, overcut, lubrication, and stoppage. This study develops a method to classify the soil encountered with unified soil classification system based on the collected data such as cutting disc’s torque, slurry pressure, slurry unit weight, P1 pump rpm, and soils retained on coarse and fine shaker screens from pipe to pipe. The soil classification system developed in this study helps to interpret the local variation of jacking force is resulted from increasing penetration resistance due to either driving from coarse soil to fine soil or driving into wood log. This penetration resistance increment is recoverable when driving condition is reversed. The friction resistance increases significantly if misalignment is larger than a threshold value of 60 mm, and remains unchanged even if deviation is corrected. The misalignment effect to friction resistance is not recoverable. The lubricant distributed among injection outlets along the pipeline ensures a more uniform distribution of lubricant around the jacked pipes and a more effective reduction in frictional resistance. For large diameter pipe jacking with stabilized overcut and sufficient amounts of lubricant, the penetration resistance can be significant relative to friction resistance.
Conference Paper
Full-text available
Microtunnelling is an important trenchless construction technique that is used to successfully install essential utility pipelines in increasingly congested urban centres around the world. An important consideration for a microtunnelling project is the magnitude of the jacking force that will be required to advance the microtunnelling shield and the string of product pipes from the starting shaft to the receiving shaft. Frictional resistances along the surface of the pipeline have a major contribution to the total jacking force. This paper considers the frictional resistance mechanism involved in advancing concrete pipes through a coarse-grained soil and describes laboratory testing carried out with the aim of physically modelling the process. Comparisons are made with case histories from microtunnelling projects recently completed in coarse-grained soils. Recommendations are made on predicting likely jacking forces in advance of future projects.
Book
Pipe jacking is a construction process for the no-dig laying of pipes. Successful pipe jacking demands low skin friction between the ground and the jacked pipe. This is achieved with bentonite lubrication. The bentonite slurry fed into the annular gap fulfils several purposes. It stabilises the annular gap by supporting the surrounding ground and reduces friction contact between ground and jacked pipe. The Bentonite Handbook deals comprehensibly with the relevant aspects of annular gap lubrication: starting with the ground conditions, which are of decisive importance for lubrication, through the rheological properties of the bentonite slurry to the technical components of lubrication technology and lubrication strategy. The use of standardised measuring apparatus is described as well as mixing equipment and the automatic lubrication system. Overview tables with calculations and suggested values for bentonite consumption quantities depending on the prevailing ground conditions and the pipe jacking parameters complete the recommendations. © 2017 Wilhelm Ernst & Sohn, Verlag für Architektur und technische Wissenschaften GmbH & Co. KG. All rights reserved.
Article
This study investigates the influencing factors that affect the jacking loads during slurry pipe-jacking works at four drives in the Shulin district sewer network in Taipei County, Taiwan, with lengths varying from 73 to 126 m. The main factors which affect the jacking loads during tunnelling may include (1) overcut annulus and volume of injected lubricant, (2) work stoppages, (3) geology, and (4) misalignment. In the four pipe-jacking drives, the jacking forces are represented using the baseline technique. The pipe-jacking results show that the local variations (increasing or decreasing) of jacking force are ascribed to the varying face resistance due to driving between coarse soil and fine soil governed sand or gravel deposit or driving into and away from a buried wooden log. The increase in the jacking loads could also be due to the increasing friction resistance resulting from the pipe deviation being greater than a threshold value of 60 mm. Excessive injected volumes of lubricant result in very low pipe frictions incurred during pipe-jacking of the four drives and are reflected through the back-analysed μavg values which vary from 0.02 to 0.09. The jacking load increases due to either overnight stoppages or short breaks are more pronounced in poorly graded gravel or sand deposit than in clayey gravel or clayey sand deposit.
Article
There is currently no published guidance on the excavatability of Irish rock for microtunnelling applications. In this paper, new data and experiences of microtunnelling through rock (using a Herrenknecht AVN slurry shield machine with a rock head) at five Irish sites are presented and interpreted. The rock type is limestone at three of the sites, with mudstone/conglomerate and sandstone at the other two sites. The jacking forces are separated into face and friction (between the concrete pipe and rock) components. Useful relationships have been established between the excavatabilityindex andthe uniaxial compressive strength and brittleness index of rock.Cutter head wear is discussed in the context of rotational distance travelled and rock strength. In addition, the suitability of a number of prediction models documented in the literature for the prediction of microtunnel boring machine performance in Irish rock is examined.
Article
This Paper investigates theoretically and experimentally the stability of a circular tunnel in a cohesionless soil with support conditions similar to those found during construction. The experimental investigation consisted of small-scale model tests in the laboratory and on the Cambridge University large-diameter centrifuge. All the model tests were carried out in plane strain using Leighton Buzzard sand and tests with and without surcharge loading are reported. The theoretical studies are based on the upper and lower bound theorems and predictions of collapse pressures from these theoretical solutions are shown to bracket closely the values observed in the model tests. Cette étude examine théoriquement et expérimentalement la stabilité d'un tunnel circulaire dans un sol pulvérulent soutenu dans des conditions semblables à celles trouvées pendant la construction. L'étude expérimentale consista en essais sur modéle à petite échelle en laboratoire et sur la centifugeuse à grand diamètre de l'Université de Cambridge. Tous les essais sur modèle furent mis à exécution sous déformation plane en utilisant du sable de Leighton Buzzard, et l'on rend compte des essais avec et sans surcharge additionelle. Les études théoriques sont basées sur les théorèmes limites supérieures et inférieures et on montre que des prévisions de pressions de rupture à partir de ces solutions sont encadrées étroitement par les valeurs observées en essais sur modèles.
Article
This paper outlines methods for estimating the jacking forces associated with different types of microtunnelling operations. These methods have been developed using probably the most extensive database of microtunnelling jacking forces assembled to date. These data were collected by questionnaire in Japan as part of an initiative by the International Society for Trenchless Technology (ISTT) and coordinated by the Japanese Society for Trenchless Technology (JSTT). Methods for predicting jacking force are produced for slurry, auger and push-in type microtunnelling operations. Separate methods are suggested for these techniques as it was found that the jacking force is sensitive to the method of installation. The methods can also take into account the soil type found on a particular project. However, sensitivity of the measured jacking force to other factors, such as soil strength and depth of installation, were not included in these predictive methods as no discernible relationships could be established due to the variability in the data.Examples from two case histories, one involving a 1.0 m nominal diameter slurry microtunnelling machine in dense silty sand and the second involving a 500 mm nominal diameter microtunnelling machine in sand and gravel, are presented which use the equations proposed in this paper. The results from these examples show that the predicted jacking forces are comparable to those measured in the field.This paper therefore presents practical and reliable methods of predicting jacking forces associated with microtunnelling projects.
Article
Slurry pipe jacking was firmly established as a special method for the non-disruptive construction of the underground pipelines of sewage systems. Pipe jacking, in its traditional form, has occasionally been used for short railways, roads, rivers, and other projects. Basically the system involves the pushing or thrusting of concrete pipes into the ground by a number of jacks. In slurry pipe jacking, during the pushing process, mud slurry and lubricant are injected into the face and the over cutting area that is between the concrete pipes and the surrounding soil. Next, the slurry fills voids and the soil stabilizes due to the created slurry cake around the pipes. Fillings also reduce the jacking force or thrust during operation. When the drivage and pushing processes are finished, a mortar injection into the over cutting area is carried out in order to maintain permanent stability of the surrounding soil and the over cutting area. Successful lubrication around the pipes is extremely important in a large diameter slurry pipe jacking operation. Control of lubrication and gaps between pipes and soil can prevent hazards such as surface settlement and increases in thrust. Also, to find voids around the pipes after the jacking process, in order to inject mortar for permanent stabilizing, an investigation around the pipes is necessary. To meet these aims, this paper is concerned with the utilization of known methods such as the GPR (Ground Penetrating Radar) system and borehole camera to maintain control of the over cutting area and lubricant distribution around the pipes during a site investigation. From this point of view, experiments were carried out during a tunnel construction using one of the largest cases of slurry pipe jacking in Fujisawa city, Japan. The advantages and disadvantages of each system were clarified during the tests.
Article
Lubricants are frequently applied in pipe-jacking, especially under difficult geological conditions or in cases of a longer alignment. The main purpose of lubricant application is to reduce the friction between pipe and soil. However, it is very difficult to quantitatively determine the real contact conditions between the two. New technology for soil–pipe interaction measurement is still scarce and requires further development. Only indirect methods are available for practical measurement of soil–pipe interaction, and engineering judgment is required for the application of those measurements. In this study, a simple test method was applied to obtain the frictional properties of the most popular lubricants in the Taiwan area. Those frictional properties were used for jacking force estimation and numerical analysis of soil–pipe interaction for linear and curved pipe-jacking. The analyses of jacking force show that reduction in jacking force is closely related to reduction in friction coefficients, and the effect of lubrication is slightly more significant in the case of curved alignment than the case of linear alignment. In addition, a study of a 400-m linear pipe-jacking case in the Taichung Science Park shows overestimation of the jacking force by an empirical formula. It reveals the reduction in pipe-soil contact area induced by over-cutting is significant for pipe-jacking in gravel formations.
Article
Friction forces usually constitute the main component of jacking loads. As a result of their increase with jacking length, it is these forces which limit the drive length. Therefore, it seems important to be able to quantify them accurately. The field monitorings, carried out as a part of the French National Project ‘Microtunnels’, have shown the effects of parameters such as lubrication, stoppages, deviation and overbreak on friction force values. Frictional stress, deduced from field monitoring, is compared with empirical results extracted from the literature and with the results of most frequently used calculation models.
Article
Field research on fourteen case histories of microtunneling and pipe jacking projects was presented. Pertinent project details were provided including pipe materials, site geometry, geotechnical information, construction sequencing, lubrication injection, and jacking force records. Jacking force records for each project were separated into isolated segments along the alignment to analyze jacking stresses. Unlubricated segments of the microtunneling drive records were analyzed to compare actual and predicted jacking forces using the proposed model. The predictive model was compared to other models currently available for predicting the frictional component of jacking forces. Lubrication effects on jacking forces were analyzed to determine how the interface friction coefficient changed once lubrication was applied to the pipeline. Two types of lubrication strategies were identified and predicted lubricated jacking forces were shown. A step-by-step guide for using the jacking force predictive model was presented for design applications and estimating lubricated interface friction values. Dr. J. David Frost, Committee Chair ; Dr. G. Wayne Clough, Committee Co-Chair ; Dr. William F. Marcuson III, Committee Member ; Dr. Paul W. Mayne, Committee Member ; Dr. Susan Burns, Committee Member. Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2007.
Article
Work carried out in The Dept. of Engineering Science. BLDSC reference no.: D203867. Thesis (D. Phil.)--University of Oxford. 1998. Includes bibliographical references.
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