Jacking Force Research Articles

Selection of jacking sequence and jacking parameter analysis of multi-row jacking pipes in water-rich sand

For the purpose of safe and efficient construction of multi-row pipe jacking in water-rich sand layer, a case study was carried out, taking the three-row pipe jacking project of the water-rich sand layer in Haikou city as an example. Firstly, based on the analysis of the disturbance mechanism of surrounding rock in multi-row pipe jacking construction, the principle that multi-row pipe jacking construction should give priority to excavate two pipe jacking tunnels which are far apart in turn was established. Secondly, taking the maximum ground settlement at the center of pipe jacking as the judgment index, the optimal scheme of the construction sequence of multi-row pipe jacking was determined. Finally, based on the field measured data, the relationship between the jacking force, the pressure of the palm surface, the average frictional resistance and the jacking process during the jacking process was analyzed, and summarized the experience of the site construction. The results show that: (1)it is better to give priority to construct two pipe jacking tunnels which are far apart in the construction order multi-row pipe jacking; (2)Based on the empirical method of surface subsidence, the maximum surface subsidence at the center of pipe jacking group can be used as the judgment index to determine the optimal jacking sequence; (3)Under the condition of "from the two sides to the middle", the surrounding rock around the middle jacking pipe is greatly disturbed by the construction of the first jacking pipe, its jacking rate should be reduced on the basis of the first building jacking pipe, and the cutting rate of the cutter and the grouting pressure should be increased, so as to realize the continuous jacking construction. The results of this paper are of great reference value to the determination of the jacking parameters of multi-row pipes in the future.

Prediction of microtunnelling jacking forces using a probabilistic observational approach

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.

Assessment of experimental friction parameters and contact property of pipe string for the estimation and verification of a solution for pipe stuck in the China's first rock pipe jacking

The first rock pipe jacking project of China in Chongqing Guanjingkou encountered a pipe sticking problem soon following the abrupt increase of jacking force. It was essential for the direct shear test results and stresses acting normal to the outer periphery of the pipe strings to be relevant in the understanding of jacking forces for the pipe stuck. In this paper, direct shear tests were performed on the frictional characteristic between a dolomite and concrete specimen using the same test method in the earlier companion paper. The normal stresses of the pipe string were obtained through plane strain finite element modeling of the pipe-jacking under different engineering geological conditions, contact characteristics, overburden and contact areas, the threshold values of the normal contact stresses increased dramatically have also been achieved, simultaneously. Then the jacking force needed for stuck pipe strings has been predicted based on the frictional test results and the normal stress simulation in order to determine where the temporary intermediate jacking stations (TIJSs) should be installed. Finally, the pipe stuck problem is solved successfully using the TIJS method, this result provides excellent reference data for the similar engineering problems in the future.

Jacking Force Estimating and Site Measured Data Analysing of a complex Curved Long Distance and Large Diameter Pipe Jacking

This paper presents the jacking force estimating and the measured data analysing of a 3D curved, 413 meters long distance and 3.8 meters external diameter jacking project. The jacking load consists of the face load and friction resistance, and it is influenced by many factors. The widely used estimated method include Chinese cord method, Japanese method and German method, and they all have application conditions, which make them have limitations for engineering application, especially the friction resistance factors are offered by a wide interval. The jacking loads are calculated by the above estimated methods in a 3D curved, 413 meters long distance and 3.8 meters external diameter jacking project, 3 intermediate jacking stations are set according the calculation result. According by the site measured datum in the construction procedure, the composition of the jacking load and its relationship with the jacking distances and the curve radius are analysed, and the frictional residence factors in clay are provided on the class by straight line and curved lines, which provide a basis for similar engineering.

Assessment of base capacity of open-ended tubular piles installed by the Rotary Cutting Press-in method

The ‘press-in’ method is a piling technique by which a pile is installed with a static jacking force while a reaction force is obtained from previously installed piles. The applicable ground conditions for this method have been significantly expanded by the ‘Rotary Cutting Press-in (RCP)’ method, whereby a vertical jacking force and a torque are applied simultaneously onto a pile with cutting teeth on its base while water is injected around the pile base. In this paper, a method to estimate the base capacity of RCP piles is proposed based on the UWA-05 framework. The proposed method utilizes CPT (cone penetration test) or SPT (standard penetration test) results as the input parameters and estimates the plugging condition (Incremental Filling Ratio, IFR) from these results. Four static load tests on open-ended RCP piles are shown to have been predicted well by the proposed method in terms of the base capacity, regardless of the embedment depth into the bearing stratum.

Case Study of sewerage pipe installation using Pipe Jacking and Micro-tunnelling Boring Machine (MTBM) in Ipoh

This paper provides a review of the sewerage pipe installations near Jalan Pengkalan Perindustrian, Ipoh Perak using pipe jacking and micro-tunneling methods. The alignment of the pipe installation involving tunneling and jacking beneath the KTMB (Kereta Api Tanah Melayu Berhad) railway track with 191 m distance from jacking to receiving pit. The average jacking force of the micro-tunneling boring machine varies over distance and the highest recorded was 310 tons at 190 m distance from jacking pit meanwhile 50 tons was the lowest jacking force within 10 m distance from the jacking pit. The trend of the advance rate, mm/m shows the similarity with the average jacking force. The higher average of jacking force leads to a higher value of advance rate with the highest and lowest value was 270 mm/m and 5 mm/m respectively. The excessive deviation for both line and level affect the magnitude of the ground surface settlement where 100 mm and 130 mm for both line and level produce 30 mm of ground surface settlement at 40 m distance from the jacking pit. As the machine advances further and has better control in deviation, the settlement decrease where the value for both line and level below 30 mm, the settlement decrease to 10 mm at 80 m distance from the jacking pit and the trend continues to decrease for both deviation and settlement. The maximum settlement for the railway track was 2 mm after the MTBM passing through and still within the allowable limit set by KTMB (10 mm over 10 m chords for intervention).

Ground Response due to Construction of Shallow Pipe-Jacked Tunnels in Sandy Soil: Laboratory Investigation

Abstract Pipe jacking is a microtunneling construction technique that is widely used as a trenchless technology in infrastructure and can be adopted in various geological conditions. Ground responses, such as displacements and soil fracturing, will occur during pipe jacking. In order to reduce disturbance to the surrounding soils, factors resulting in ground responses should be evaluated prior to construction. This article presents a series of laboratory tests to investigate the ground response that is due to shallow buried pipe jacking in sandy soil. Single and parallel pipe-jacked tunnel tests were conducted to simulate different construction conditions. Vertical soil displacements and corresponding jacking forces for various cases were observed and discussed. The results indicate that factors such as the existing pipes, the thickness of overburden soil, and the grouting slurry used have significant effects on the ground responses during pipe jacking. Slurry with a proper ratio is proposed for pipe jacking construction. Soil fracturing and grouting overflow can easily occur in the shallow buried tunnels when slurry injection points are opened at the upper side of the pipe. The jacking parameters should also be controlled within a range to reduce the risk of soil fracture and grouting overflow.

Assessment of Anomaly Detection Methods Applied to Microtunneling

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 microtunneling, this paper explores the potential for AD methods to provide a more accurate and robust detection of incipient faults. A selection of the most popular AD methods proposed in the literature, comprising both clustering- and regression-based techniques, are considered for this purpose. The relative merits of each approach is assessed through comparisons to three microtunneling case histories in which anomalous jacking force behavior was encountered. The results highlight an exciting potential for the use of anomaly detection techniques to reduce unplanned downtimes and operation costs.

Bionic Design to Reduce Jacking Force for Trenchless Installations in Clay Soil

The application of trenchless technology is the trend of underground public facilities’ installation, replacement and repairing. As the soil-engaging component during penetrating bore, the working resistance of penetration head has remarkable effect on energy consumption of the whole working process. Some typical soil-digging animals, like pangolin and earthworm, they own special micro structures on their surface. It has been widely proved that some micro geometrical structures can effectively reduce adhesion resistance. Four kinds of bionic penetration heads were designed by imitating micro geometrical structures inspired by the soil animals. In this work, the real time jacking forces of the bionic penetration heads were measured and compared with a smooth penetration head (control group) without micro geometrical structures. The result indicated that the jacking forces of the bionic penetration heads were smaller than that of the smooth penetration head. This proved that the bionic penetration heads have the ability of reducing adhesion resistance. The vertical concave penetration head got the smallest jacking force, of which the average jacking force was 18.7% lower than that of the smooth penetration head. The interaction between soil and bionic surface of penetration head was discussed on the condition of wet friction. The bionic surface reduced the adhesion resistance by disturbing the soil and braking the continuous water film between soil and the surface of the penetration head.

Development of compound EPB shield model test system for studying the water inrushes in karst regions

The shield tunnel, when running through urban karst areas, may induce engineering hazards, such as water inrush, ground collapse, and shield drooping. To reveal the water inrush mechanism triggered by confined karst caves during shield excavation, we developed a model test system for studying the evolution of water inrushes, which could be used to simulate the shield excavation process. The compound EPB shield machine allows the adjustment of parameters, including the cutter rotation speed, torque, excavation speed, supporting force, tunneling footage and excavation height. At a 1780 mm excavation distance, the deflection of the front end can reach the millimeter level. A special cutter with an automatic protection mechanism was designed to avoid low rotation speeds and high jacking forces, thereby effectively protecting the cutter. Moreover, several new and advanced test techniques were developed, including the soluble 3D printing of an irregular karst cave model and ground settling reconstruction using laser measurements. Based on these test devices and advanced techniques, a model test of the water inrush in the Jinan metro was conducted using the EPB shield machine, in which the variations of displacement, stress, and seepage pressure were analyzed. The results showed that the apparatus performed stably and reliably.

Validity of Anchorage Zone Design for Post-Tensioned Concrete Members with High-Strength Strands

This paper evaluated the validity of a design method for anchorage zones in post-tensioned concrete members using Grade 2400 strands from American Concrete Institute (ACI) Building Code, ACI 318-19 and Association of State Highway and Transportation Officials (AASHTO) codes. For this purpose, the behaviors of anchorage zones in ten specimens were investigated and compared with ACI 318-19 and AASHTO codes, considering the jacking force and ultimate flexural load. The anchor shape, number of strands, and reinforcement details of the anchorage zone were considered as variables. The test results showed that ACI 318-19 and AASHTO codes could not predict where the maximum bursting force would occur. In addition, they calculated bursting force by summation of the pre-stressing forces from the individual strands, whereas the experimental results were not linearly proportional to the number of strands. The ACI 318-19 and AASHTO standards were inadequate to calculate bearing force of post-tensioned members using high-strength strands. Furthermore, additional stress in the anchorage zone occurred as the flexural load increased, which may have been caused by a failure in the anchorage zone. The experimental results indicated that the method used to predict stress and design of anchorage zone in current codes should be improved to consider stress distribution and additional stress in post-tensioned concrete members using high-strength strands.

Estimation of jacking forces on casings in microtunneling

Estimation of jacking forces on casings in microtunneling

Research of jacking force of densely arranged pipe jacks process in pipe-roof pre-construction method

The tunnel crossing project of the Taiyuan Railway Station is constructed by using a pipe roof preconstruction method (PPM). The project uses 20 steel pipe jacks with a diameter of 2 m. The distance between the jacking pipes is 165–265 mm. In this study, the jacking force of densely arranged pipe jacks was studied by a large-scale similar model test and engineering measured data. Pipe jacking forces at different positions during the model test were analysed. The upper pipe jacks of the PPM interacted with the surrounding soil. The soil between the pipe jacks became tightly compressed, and an arched soil–pipe jack pseudostructure was formed (pipe–soil arching effect). A squeezing phenomenon was observed during the jacking process. The jacking force of the pipe below the waterline was reduced by water buoyancy. The formula for calculating the jacking force of the jacking pipe below the pipe arching effect was proposed. The passive soil pressure coefficient should be reasonable in the formula for calculating the jacking force. The formula for calculating the jacking force below the water level line was derived.

Experimental Research Based on the Optical Fiber Sensing Technology for a Jacked PHC Pipe Pile Penetration Process

The aim of this work is to explore the influence of the end resistance and shaft resistance regarding the mechanism for jacked pile penetration and the load‐transfer rule during the penetration process. A full‐scale field test was conducted in an actual project located in Dongying, Shandong Province, China. In this test, the axial strain experienced by two closed Prestressed High‐strength Concrete (PHC) pipe piles during jacking into layered soil was monitored successfully using Fiber Bragg Grating (FBG) sensors mounted on the pile shaft. The experimental results show that FBG sensors have a good stability, strong antijamming performance, and can effectively monitor the pile stress. The variation law of the jacking force reflects the distribution of the soil layer, and the hardness of the soil layer at the pile end limits the pile force. When the pile end enters the silt layer from the clay layer, the jacking force and shaft resistance increase by 2.5 and 1.7, respectively. The shaft resistance accounted for 44.99% of the jacking force. The end resistance is affected by the mechanical properties of soil, and the end resistance of the silt layer is approximately twice that of the clay layer. The end resistance of the silt layer accounted for 59.84% of the jacking force. When the pile end enters the soft soil layer from the hard soil layer, the impact of the pile driving speed and the tangential force on the surface of the pile body must both be considered. During the pile penetration process, as the penetration depth increases, the radial stress on the pile side at a given depth is gradually released, while the shaft resistance at the pile side degrades significantly.

Prediction of Friction Resistance for Slurry Pipe Jacking

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.

Assessment of non-linear rock strength parameters for the estimation of pipe-jacking forces. Part 2. Numerical modeling

In the earlier companion paper (Ong and Choo, 2018), direct shear tests were performed on reconstituted tunneling rock spoils for the development of equivalent tangential cohesion, c't,p and friction angle, ϕ't,p. These equivalent rock strength parameters were used in assessing jacking forces, which were measured from three pipe-jacking drives negotiating the highly weathered lithologies from the Tuang Formation, Malaysia. The measured jacking forces were back-analyzed, leading to the development of frictional coefficient, μavg and the vertical stress at the tunnel crown, σEV. In this paper, the reliability of using the parameters, c't,p, ϕ't,p, μavg and σEV was assessed through the use of three-dimensional finite element modeling of the studied pipe-jacking drives. The peak tangential strength parameters, c't,p and ϕ't,p were applied to the modeled rock mass and the strength parameters of the pipe-rock interface were developed from μavg. Arching ratios were developed from σEV, which were subsequently used for post-analysis assessment of the results from numerical modeling. There was sound agreement between the resulting pipe-rock interface shear stresses, τ1 and reaction loads, ΣFy from the numerical analysis against the field measured jacking forces, thus demonstrating the reliability of the use of developed equivalent rock strength parameters, c't,p, ϕ't,p, μavg and σEV in the assessment of pipe-jacking forces through highly weathered lithologies.

An Improved CPTu-based Method to Estimate Jacked Pile Bearing Capacity and Its Reliability Assessment

This paper presents an improved method for predicting the bearing capacity of single jacked pile based on piezocone penetration test (CPTu) data which contain tip resistance (qt), side friction (fs) and excess dynamic pore water pressure (u2). Firstly, the average value of qt was determined to calculate the pile unit base resistance according to the influence zone of the logarithmic spiral concerning the effect of soil types. Secondly, fs and u2 were used to calculate the pile unit shaft resistance considering the effect of friction fatigue. The pile jacking force was obtained in terms of unit base resistance and unit shaft resistance. The ultimate bearing capacity was finally determined using pile jacking force multiplied by a force ratio denoted as Rf. The ultimate bearing capacities calculated for two case projects show a good agreement with the measured results, which indicates that the proposed method is feasible and effective. Reliability assessment was carried out on the proposed method and other five estimation methods with respect to the reliability index obtained by advanced first-order second-moment (AFOSM) method. Comparison result showed that the method proposed in this study has a higher reliability index over other five existing methods. Therefore, the proposed method can be used as a reliable alternative to predict the bearing capacity in the engineering practice of jacked pile foundation.

Model tests on performance of offshore wind turbine with suction caisson foundation in sand

The performance of steel caisson during and after installation with different penetration velocities in medium dense sand is presented. The applied jacking forces, the amount of formed soil heave and bearing capacity were measured in the model tests. The influence of penetration velocities on jacking forces, soil heave and bearing capacity were also discussed in detail. The results indicated that the jacking forces for caisson in medium dense sands were significantly affected by the penetration velocity. The larger the penetration velocity, the more soil flowed into the caisson cavity during installation. This will lead to larger inner shaft resistance and in turn more jacking forces required for the same penetration depth. The height of soil heave during installation increases with penetration velocity. The m value calculated by the ratio of the volumes of the soil heave to that of the penetrated caisson wall can be used to evaluate the soil heave. The larger the applied velocity, the larger the m value and larger bearing capacity of caisson after installation. The relationship between the m value and penetration velocity can be used to control the soil heave for a steel caisson with a wall thickness to external diameter ratio of 4.2% in medium dense sand by jacking method.

Model tests on open-ended concrete pipe piles jacked in sand

An experimental study of the performance of concrete pipe piles during installation under different penetration speeds and static load tests on the piles in sand is presented. The applied jacking force, the amount of pile penetration, length of soil plug formed and ultimate bearing capacity were measured during the model tests. The results showed that the concrete pipe piles were partially plugged and the behavior of the soil plug was significantly affected by the penetration speed. The lower the penetration speed, the larger the soil plug formed which in turn leads to a greater ultimate bearing capacity. The size of soil plug can be evaluated by the m value defined as the ratio of the volume of the soil plug to that of the penetrated pile wall. The relationship between the m value and the penetration speeds can be used to estimate the amount of soil plug and the depth of penetration for an open-ended concrete pipe pile jacked into sand.

Effects of hybrid steel fiber reinforced composites on structural performance of segmental linings subjected to TBM jacks

AbstractIn recent years, incorporating fibers as the main reinforcement in segmental lined tunnels has gained significant interest. Damage to segmental linings due to the thrust force of TBM jacks is one of the main problems that arises in the assembly phase, reducing serviceability and durability of tunnels. The aim of this paper is to experimentally and numerically investigate the effects of fiber size, content, and hybridization on the performance of steel fiber reinforced concrete (SFRC) tunnel segments under TBM jack forces compared to conventionally reinforced concrete (RC) segments. In this regard, different scenarios of segment support conditions and eccentricity of the applied TBM jack loads are investigated in a particular real tunnel. The results showed that under various configurations of segment support and load eccentricity, SFRC composites show better performance over RC in both SLS and ULS conditions under TBM jack loads in terms of cracking strength and damage propagation.