Jacking Force Research Articles

Lubrication performance of pipejacking in soft alluvial deposits

Pipejacking technologies has been extensively chosen by many mega cities worldwide to construct their sewer pipelines. Lubrication has been deemed to be the key factor in manipulating the performance of pipejacking works. Inadequate lubrication during pipejacking can lead exaggerated jacking force causing damages to the jacked pipe string and adjoining properties. Due to limited studies, a consensus has not yet reached. This study gives an access of evaluating the lubrication performance via the reduction in the frictional coefficient μ and investigates the impacts of injection type, soil and lubrication natures, and misalignment on the lubrication performance for a pipejacking project in alluvial soil deposits. The effect of misalignment, while ramming through the 8–21 m section of gravel at Drive C, gears up the frictional stress τld to 12.5 kPa (compared to 0.4 kPa of the 2–8 m section of the same gravel) and reduces the reduction to 71%. While traversing through the 24–31 m section of clayey gravel at Drive D, the occasional gravel not being long enough to develop lower face resistance leads the misleading reduction of 60%. These factors have greater influences on the lubrication performance than the injection type. The presented results would be helpful in managing the lubrication performance while pipe ramming for upcoming pipejacking project.

Experimental Study on the Complex Contact Frictional Property of an Ultralong Distance Large-Section Concrete Pipe Jacking and Prediction of Pipe String Stuck

Line 2 of the Guanjingkou Pipe Jacking Project in Chongqing encountered a pipe sticking problem, whose occurrence was inevitably attributed to the higher total frictional resistance of pipe strings rather than the maximum jacking force. Line 1, which is about to start construction, has basically the same construction environment as Line 2 using the same microshield and pipe string sizes. To avoid repeating the pipe sticking problem of Line 2, the mutual friction characteristics between the surrounding rocks and jacked pipe strings are studied for Line 1 by adopting the same test method under seven complex contact conditions (the presence or various combinations of three substances, i.e., extrapipe string field debris, bentonite slurry, and sand-laden waste slurry, on the jacked pipe string-surrounding rock contact surface are mainly considered). The results show that sufficient bentonite slurry can effectively reduce the frictional resistance, and when the amount of bentonite is insufficient, the average friction coefficient (AFC) of the later contact surface increases by 50%∼70%. The comparison of the monitored versus predicted jacking forces indicates that the value predicted by the test is slightly higher than the monitored force and the variation trends of the two match well, thus proving the correctness of the test results. It is possible to continue predicting the variation trends of the jacking force and frictional resistance based on the contact situation outside the pipe string wall, which greatly lowers the probability of re-encountering pipe sticking. The test results not only explain the important role of bentonite slurry in reducing the pipe string wall frictional resistance but also suggest that an increase in the pipe string wall frictional resistance resulting from the complex contact inflow into the overexcavation gap is the root cause of pipe sticking; moreover, the number of jacked pipe strings matching a single IJS is the second cause of pipe string sticking. The methodology of this study can provide a reference for other studies concerning the jacking force of long-distance rock microshield tunnelling.

A method to estimate the jacking force for pipe jacking in sandy soils

Pipe jacking is a commonly used trenchless technology to install pipelines especially in congested urban areas or river crossings. However, the estimation of the jacking force is often heavily dependent on empirical calculations. The jacking force needs to be greater than the combined frictional resistance and face resistance. This investigation proposes to use a modified Protodyakonov’s arch model to compute the face resistance. A series of direct shear tests is performed to provide data of interface friction coefficient between different types of soil and pipe. The influence of slurry lubricant is also considered. A two-dimensional plane strain numerical model is conducted, where the surrounding soil is simulated as discrete particles and the lining is simplified as a single big particle. The novel modeling technique enables the evaluation of the normal force acting on the pipe. The friction resistance is then determined by multiplying the interface friction coefficient by the normal force. A ‘wavy’ shaped pipeline model is proposed to define an angular deviation influence factor to scale up the calculated jacking force due to pipe misalignment. In the end, comparison between calculated and field measured jacking force is conducted for three different drives in a pipe jacking project to illustrate the effectiveness of the proposed analysis framework.

3-D numerical model of jack force interaction to segmental tunnel lining in soft soil

The construction process of a bored tunnel is a complicated process. During tunnelling, loads were acting on tunnel and tunnel lining were installed to support excavation. Simultaneously, soil redistribution induced by tunnel excavation leads to lining to deform. One of the parameters that affect global soil-tunnel behaviour is the jack forces. Jack force is exerted during the tunnel advancement to install the lining and the same time to enhance tunnel face stability. The complexity of jack force application to ensure the overall tunnel stability is not fully studied yet. Hence, the impact of jacking force on segmental tunnel lining and surrounding soil during the tunnel advance is still unclear. This paper presents a numerical simulation by using ABAQUS/Standard 3D FE software to determine and investigate the lining deformations/jacking force relationship. The behaviour of different tunnel lining thickness applied with a variation of jack forces in the tunnel-boring machine (TBM) were examined. The result based on the numerical model explained that the jacking force required to advance is related to the cross section area of segments. Finally, a relation has been established between the segment’s thickness and the jacking force t hat required advancing through a certain soil block with specific loads cases. The findings showed that the complex geological features and loads case applied to cause great stress on the tunnel face which have to be encountered by a certain thrust magnitude to advance the tunnel. The model analyses the contact reaction and radial reaction to the segment as a result of the axial force that is exerted by jack thrust and bending moment due to strata load, respectively. However, a proposed model that suggests a certain step to investigate and analyse the magnitude of jack forces is required.

Assessment on tunnel lining to ensure stability in soft ground

Soft ground tunnelling describes as additional measures that are needed to be taken as it has been associated with settlement due to changes of stress and strength of the soil induced by tunnelling. Segmental tunnel lining is a structure used to support the ground and to have allowable movement due to soil stress redistribution. The research will be focusing on the type of modelling, structure parameter of the tunnel, pressure upon the tunnel lining and relationship with the induced ground settlement. Tunnel modelling was done in three dimensional (3D) modelling using ABAQUS software; of tunnel as parameter. This paper will discuss the effect of jack forces to the global behavior of the tunnel in order to support the surrounding load, thus be able to handle the tunnel-soil reaction without any visible or critical deformation, so that the tunnel can be used in the stable condition. A stand-alone ring method together with all-in-once method was used to simulate the Singapore MRT Circle Line 3 (CCL3). In the findings, when the tunnel lining thickness is reduced, the settlement of the ground surface is increased. Jack forces is also one of the reason of the tunnel to distort and the effect is more visible on the rings with reduced thickness compared to original thickness of the tunnel lining.

Numerical Simulation Analysis of Supporting Stability of Cast-in-place Piles in Pipe Jacking

Combined with the support excavation and pipe jacking construction of the pipe jacking working well in a section of Zhenjiang sponge city plan construction, the three-dimensional numerical analysis model was established by MIDAS-GTS, and the deformation of the supporting structure at each construction stage was analyzed. The conclusions are as follows: when the three-dimensional numerical analysis model is established, the deformation of the beam element is closer to the real situation than that of the plate element beam element; in the process of pipe jacking construction, the displacement of the supporting structure is opposite to that of the jacking direction after the Jack loads, and the displacement trend changes linearly with the magnitude of the Jack force. in the process of pipe jacking construction, the maximum displacement of the supporting pile occurs at the break of the supporting pile at the exit of the pipe jacking machine. the deformation of the supporting pile can be effectively reduced by strengthening the soil in a certain range of the opening of the pipe jacking. Through the simulation analysis of excavation support and subsequent pipe-jacking construction with concrete cast-in-place pile, the results can provide a reference for the design of supporting structure and the control of surface subsidence and deformation during construction.

Numerical simulation for an estimation of the jacking force of ultra-long-distance pipe jacking with frictional property testing at the rock mass–pipe interface

In ultra-long-distance rock micro-shield pipe jacking, the pipe wall friction resistance is a key factor that determines the magnitude of the jacking force and the layout of the intermediate jacking stations (IJSs), whereas the pipe-rock contact condition is the critical factor controlling the pipe string wall friction resistance. This paper aims to reveal the variation law of the friction resistance between the outer wall of a large-section of concrete pipe string and the surrounding rock during construction via ultra-long-distance rock micro-shield pipe jacking. To that end, the shear friction behaviour and mechanical mechanism was investigated between sandstone and concrete pipe string walls under seven different complex contact conditions (primarily considering various combinations of the three substances, namely, extra-pipe in situ debris, bentonite slurry and sand-laden waste mud at the pipe-rock contact surface) through direct rock shear tests based on the actual pipe-rock contact condition at the Guanjingkou Water Conservancy Project in Chongqing. The average friction coefficient (AFC) of the residual phase of the contact surface under 7 contact conditions was obtained by friction testing. Combined with the contact situation between the surrounding rock and pipe strings at the stage of a rapidly increasing jacking force, a three-dimensional finite element model was established, and the displacement control method was used to simulate the jacking. The comparison with the field monitoring results shows that the numerical model can accurately predict the jacking force and verify the reliability of the AFC parameters in the numerical calculation. Therefore, the combination of indoor testing and the finite element method can be applied to study the jacking force for other ultra-long rock micro-shield pipe jacking applications.

Analysis of jacking forces during pipe jacking in granular materials using particle methods

Trenchless technology is often used in congested urban areas or river crossings to install underground pipelines to minimize disturbance to surface traffic or other activities. Pipe jacking is a typical technique applied to jack pipe segments between two working shafts. However, the design of the jacking force is usually implemented using empirical methods. It should be emphasized that the jacking force will change for each site, depending on the magnitude of overcut, lubricants, work stoppages, geology and misalignment. A particle method is proposed to estimate the jacking force along the pipe. The microparameters are calibrated for sandy soils in Shenyang, so that the macroscale material behavior can be reproduced using the particle model. Hence, the normal force around the pipe circumference can be derived in the particle model, after which the interface friction coefficient is applied to evaluate the friction resistance mobilized at the soil-pipe interface. A modified Protodyakonov’s arch model can be used to assess the magnitude of earth pressure acting on the shield face. In the end, the combination of friction resistance and face pressure provides the jacking force. The efficacy of the proposed particle method is demonstrated by comparing calculated jacking forces with those measured in the field for three types of jacking machines in sandy soils under the Hun River, Shenyang.

Calculating Jacking Forces for Circular Pipes with Welding Flange Slabs from a Combined Theory and Case Study

Recently, the Steel Tube Slab (STS) curtain method has been successfully used in the construction of ultra-shallow metro stations in modern urban areas. By using the STS curtain method, the external surfaces of pipes are welded with flange slabs, and then the pipes are jacked into soils. However, the nature and extent of the influence of flange slabs on the calculation of jacking force is unclear. This paper presents the first combined theoretical and case study to calculate the increase of jacking forces for circular steel pipes with welded flange slabs during the entire jacking process. The increase of jacking forces was assumed to balance the friction at the soil-pipeline interface. Theoretical formulae were firstly developed to calculate earth pressure based on pressure arch theory and elastic foundation beam theory. A case study was then performed to verify the theoretical results with the field data from Olympic Metro Station on the Shenyang Metro Line 9 in China. Subsequently, factors influencing the calculation of jacking force were analyzed and discussed. Results show that the theoretical formulae produced good results with minor errors. The implications of these findings regarding the prediction of jacking force and selection of hydraulic jack are discussed.

Bond behaviour of CFRP tendons in UHPFRC

For a safe design of prestressed concrete members, the bond behaviour of prestressing tendons needs to be investigated. In general, for prestressing tendons, an a priori determination of the transfer length is essential. For thin concrete elements, the minimum thickness to provide a split-free transmission zone has to be determined. To realise thin concrete members, high performance cementitious composites are advantageous. Ultra-high performance fibre reinforced concrete (UHPFRC) provides high compressive and tensile strengths with ductile material behaviour. The application of non-corrosive reinforcement, e.g. carbon fibre reinforced polymer (CFRP), allows for filigree concrete elements with a thin concrete cover to only fulfil bond requirements. For the material combination of CFRP reinforcement and UHPFRC, the bond behaviour was investigated experimentally and theoretically. By means of pull-out tests local bond strengths were determined for different release states of jacking forces (i.e. lateral extension of the reinforcement). Tests on small-scale beams were conducted to determine transfer lengths and minimum dimensions of thin UHPFRC elements for two types of CFRP prestressing tendons. Simulations and further investigations on the bond behaviour were performed using non-linear finite element modelling as well as an analytical approach.

Developments and research directions in pipe jacking and microtunneling

This paper provides a review of the history and development of pipe jacking and microtunneling methods with extensive referencing to the published literature. The application of such methods in comparison with other trenchless technologies is discussed and the various planning, design and construction aspects are introduced. The emphasis of the paper is to trace the academic research and field monitoring results covering critical aspects of design and construction with a particular emphasis on jacking force estimation and the effect of lubrication on jacking forces.

Assessment of non-linear rock strength parameters for the estimation of pipe-jacking forces. Part 1. Direct shear testing and backanalysis

A method of backanalysis was used for the assessment of pipe-jacking forces from three pipe-jacking drives in laminated shale and interbedded lithological units of metagraywacke, siltstone, greywacke and phyllite found in the highly weathered and fractured lithologies of the Tuang Formation (Malaysia). Direct shear tests were conducted on reconstituted tunneling rock spoils sampled from three pipe-jacking sites. The direct shear test results were initially assessed using the Mohr-Coulomb failure criterion, which demonstrated severe shortcomings in capturing the nonlinear shear strength behavior of the reconstituted tunneling rock spoils. Subsequently, a simple power law function was proposed together with the generalized tangential method to obtain useful equivalent tangential cohesion, c't,p and friction angle, ϕ’t,p for the assessment of pipe-jacking forces in fractured lithologies. The outcomes from this study show that the tangential Mohr-Coulomb strength parameters can be used to backanalyze the frictional coefficient, μavg and the vertical stress at the tunnel crown, σEV. These backanalyzed values were successfully related back to the measured jacking forces and jacking speeds for pipe-jacking drives in various geological conditions and lubrication efforts. The use of the backanalyzed parameters c't,p, ϕ’t,p, μavg and σEV in the assessment of pipe-jacking forces from highly weathered rocks comprising of laminated and interbedded lithological units could lead to the prediction of jacking forces using numerical models. A companion paper to this study has also been produced to evaluate the reliability and suitability of these backanalyzed parameters for assessing pipe-jacking forces using the finite element method.

ANALYSIS AND DESIGN OF MRT’S CIRCULAR TU

ABSTRACT Jakarta MRT was one of solution to solve the traffic jam in Jakarta. There are two physical constructions which serves as the main infrastructure of Jakarta MRT, elevated and underground track. It is not only the first MRT in Indonesia but also, the first large-scale underground works in Jakarta. The physical construction of underground structure became an interesting case to be researched. The use of precast concrete tunnel lining (PCTL) segment was necessary to hold the loads and to provide the space for underground track. In designing the tunnel lining, calculation of the member forces and safety check are necessary to determine the amount of rebar and the dimension, and also to know the value of safety, so, the tunnel lining can be used as the function. According to the guidelines for the design of shield tunnel lining issued by International Tunnelling Association (ITA, 2000), the member forces of tunnel lining could be calculated by (1) Elastic Equation Method, (2) Bedded Frame Method, (3) Finite Element Method (FEM). In this research, the member forces of tunnel lining are calculated using analytical method, without computer program. Therefore, method (1) is used to know the value of each member forces to be used for designing the reinforcement bars. The member forces are analysed for tunnel lining with 6.8 m outer diameters, 1.5 m width and 0.25 m thickness in Jakarta MRT CP106 (Bundaran HI). Based on research which has been done, obtained the maximum values for positive bending moment in the tunnel crown (I¸ = 0°) is 101.352 kN.m, for negative bending moment in the tunnel axis (I¸ = 90°) is -281.394 kN.m. In contrary, the value of maximum axial force is in the tunnel axis (I¸ = 90°) is 1094.538 kN, for minimum axial force is in the tunnel crown (I¸ = 0°) is 904.674 kN. While, the value of maximum shear force is in (I¸ = 120°) is 118.740 kN, for minimum shear force is in (I¸ = 30°) is -66.866 kN. The result of safety checks against member forces in tunnel lining, the value of nominal bending moment multiplied by reduction factor (I• · Mn) is 296.263 kN.m, bigger than the value of ultimate bending moment (Mu) is 281.394 kN.m. For the value of nominal shear force multiplied by reduction factor (I• · Vn) is 136.095 kN, bigger than the value of ultimate shear force (Vu) is 118.740 kN. While, safety check against thrust force of shield jack obtained the value of maximum compressive stress of concrete segment (𝜎𝑐) is 5.016 MN/m2, bigger than the value of allowable stress (𝜎𝑐𝑎) is 16 MN/m2. Keywords: Jakarta MRT, underground, tunnel lining, member forces, Elastic Equation Method.

Numerical simulation of the uplift behavior of shield tunnel during construction stage

In this study, a new 3D numerical model that considers the circumferential joint, longitudinal bolt, grout pressure, jacking force and the constraint of shield on the linings is developed to derive deeper insights into the lining uplift behavior during shield tunneling. The numerical analysis is conducted using ANSYS, which is verified by a case history in soft soils. Revealed by both the measurements and calculation results, it is found that the lining uplift due to shield tunneling in soft soils can be divided into three stages: dislocation, stretch and steady deformation stages, respectively. In the dislocation stage, the lining deformation attributes principally to the dislocation deformation between neighboring linings. In the stretch stage, the lining deformation is mainly caused by the stretch deformation of circumferential joints. The major uplift is caused during dislocation stage. Thereafter, the impacts of shield-driving parameters including gradient of grout pressure, jacking force and pre-tightening force of longitudinal bolts on the uplift behavior are investigated by a series of parametric studies. The jacking force during segment preparation and assembly shows the most significant impact on the uplift of the tunnel, while the pre-tightening force of longitudinal bolts shows negligible impact. Finally, the control criterion for lining uplift related to the allowable dislocation and opening angle of circumferential joints is proposed.

Interaction diagrams for design of hybrid fiber-reinforced tunnel segments

Fiber reinforcement has emerged as an alternative to traditional reinforcing bars and welded wire mesh reinforcement for precast concrete tunnel segments. This is mainly due to improved postcracking behavior and crack control characteristics of fiber-reinforced concrete (FRC) segments. A hybrid solution of fibers and reinforcing bars is adopted when FRC is not adequate as the sole reinforcing system. Often times, this is the case in large-diameter tunnels with large curved length segments in order to achieve required strength for embedment loads in shallow cover, TBM thrust jack forces, and loading from imperfect construction and irregularities. P–M interaction diagrams are used as one of the main design tools since segment cross section, under most of governing load cases, is subjected to a combined axial force and bending moment. Standard FRC constitutive laws recently allows for a significant residual strength in tension zone below the neutral axis. However, design capacity of hybrid fiber-reinforced concrete (HRC) segment is significantly underestimated using conventional Whitney’s rectangular stress block method. Methods that currently incorporate contribution of fibers on P–M diagrams are based on numerical and finite-element analyses. However, closed-form solutions offer important advantages. This paper presents material models, derivations and for the first time closed-form solutions to construct P–M interaction diagram of HRC segments. Parametric studies are conducted and validity of the model is verified by simulating experimental results of HRC columns and model-predicted results of precast and cast-in-place concrete linings. Results show that using appropriate material models for fiber and reinforcing bar, engineers can use the proposed methodology to obtain P–M interaction diagrams for HRC tunnel segments.

Frictional analysis of pipe-slurry-soil interaction and jacking force prediction of rectangular pipe jacking

Predictive model and formula of jacking force has been well-established for circular pipe jacking in the past decades. However, the frictional mechanism of pipe–soil–slurry and jacking force prediction of rectangular pipe jacking has not well been understood. Nowadays, the rectangular pipe jacking is widely used, because of its over 20% larger effective usable area than that of circular pipe as underground facilities, with the same cross-sectional area. Nevertheless, the corresponding prediction models of thrust of rectangular pipe jacking are lacking. In order to further understand the frictional mechanism of slurry rectangular pipe jacking, five classical analytical calculation models have been proposed, considering the pipe–soil–slurry interaction, and prediction formulas are obtained. Then, 3D finite difference method was introduced to estimate the jacking force by using FLAC3D. Finally, three case studies have been carried out to validate the proposed models. The results show that the numerical and theoretical results have good consistency, and what is more, the measured jacking force can be well included within the ranges of analytical models presented in this paper, which can improve the thrust prediction of rectangular pipe jacking.

Research on the Slurry for Long‐Distance Large‐Diameter Pipe Jacking in Expansive Soil

When the pipe jacking technology is applied in expansive formation, the soil around the pipe will easily absorb water from the slurry and expand to wrap up the pipe, producing an excessive pipe jacking force. A water‐based slurry formula suitable for pipe jacking in expansive soil layer was proposed in this paper. Firstly, the key design points of pipe jacking slurry in expansive soil were put forward. Secondly, plant glue, potassium humate, Na‐CMC, and graphite powder were chosen as treating agents to improve the slurry performance. The effect of addition levels of different treating agents on the funnel viscosity, filter loss, expansion ratio, friction coefficient and water dissociation rate of the slurry were tested. Thirdly, based on the results of single‐factor tests, a water‐based slurry formula suitable for pipe jacking in expansive soil was obtained. Finally, the slurry formula was applied in a practical pipe jacking project in expansive formation, and the jacking force was controlled well in the whole jacking process. The new water‐based slurry is cheap and practical and has no pollution to environment. Furthermore, a simple and practical calculating method of the pipe jacking force was presented. The comparison of the calculated and measured pipe jacking force shows that the simple calculating method can estimate the jacking force well. Improving slurry performance to reduce jacking force in pipe jacking and predicting pipe jacking force accurately can help reducing the investment for counterforce wall and jacking system in pipe jacking engineering.

A new cable force identification method considering cable flexural rigidity

Cables are the main load-bearing members of prestressed structure and other tensegrity structures. Based on the static equilibrium principle, a new cable force identification method considering cable flexural rigidity is proposed. Its computational formula is derived and the strategy to solve its implicit formula is introduced as well. In order to improve the reliability and practicality of this method, the influence of the cable flexural rigidity on cable force identification accuracy is also investigated. Through cable force identification experiments, the relationships among certain parameters including jacking force, jacking displacement, initial cable force, and sectional area (flexural rigidity) are studied. The results show that the cable force calculated by the proposed method considering flexural rigidity is in good agreement with the finite element results and experimental results. The proposed method with high computational accuracy and resolution efficiency can avoid the influences of the boundary condition and the length of the cable on calculation accuracy and is proven to be conveniently applied to cable force identification in practice.

A jacking force study of curved steel pipe roof in Gongbei tunnel: Calculation review and monitoring data analysis

Jacking force is one of the crucial parameters for pipe structure design, selection of pipe jacking machine and shaft structure design during jacking process. To predict the jacking force more accurately, this paper summarizes four calculation methods of curved jacking force. The Japan Micro Tunneling Association (JMTA) Method is based on Terzaghi arching theory with full contact between pipe and soil. However, according to the elastic contact theories, Hertz contact method, Shimada method and Persson contact method assume that pipe and soil contact partially in stable excavation cavity. The three methods are considering the influences of frictional resistance of pipe-soil and pipe-mud concurrently. By field monitoring of jacking force data in different types of soil and cover depth in the curved pipe jacking roof of Gongbei tunnel, the cutterhead resistance, dynamic and static frictional resistance have been analyzed. Also, the additional frictional resistance caused by stoppage effect has been presented. The results show that the mud pressure is more convenient to calculate the cutterhead resistance than active soil pressure. The Persson contact model is applicable to calculate the friction in stable condition of excavation cavity while the Shimada model is capable of predicting frictional resistance values for unstable condition.

Earth pressure on shield excavation face for pipe jacking considering arching effect

Pipe jacking is often used to install pipelines in congested urban areas or river crossings. The applied jacking force needs to be greater than the frictional resistance along the pipe and the face resistance. Lubricant slurries are usually employed to minimize the frictional resistance. Therefore, it is critical to estimate earth pressures acting on shield excavation face correctly. In this paper, the original Protodyakonov’s arch model is modified to calculate the vertical pressure on deeply buried pipes. For shallow burial depth less than 5 m, the Terzaghi arching model is still applicable to estimate the vertical pressure. The soil prism in front of excavation face is divided into different zones to establish the force equilibrium. The calculated earth pressure is applied on top of soil wedges. The proposed analytical solution can analyze the stability of vertical and inclined excavation faces considering the influence of three-dimensional arching effect, as well as the contribution of soil cohesion. In the end, the effectiveness of the developed design framework is assessed by comparing calculations with experimental measurements of earth pressures on excavation face.