Explore the vast range of titles available.

In long-distance, large-section rectangular pipe jacking operations, machine deviation is an inevitable factor that poses substantial challenges to the accurate prediction of frictional resistance. To address this issue, a novel methodology is proposed to analyze the dynamic interactions at the pipe–soil–slurry interfaces. This approach integrates real-time alignment monitoring with the Winkler elastic foundation theory to enhance predictive accuracy. A comprehensive predictive framework is developed for excavation profiles and pipeline deflection curves under varying thrust distances, enabling the quantification of complex contact states. By applying Newton’s law of friction and the Navier–Stokes fluid mechanics equations, calculation methods for the frictional resistance of pipe–soil contact and pipe–mud contact are systematically derived. Furthermore, a predictive model for the jacking force in long-distance rectangular pipe jacking, accounting for complex contact conditions, is successfully established. The jacking force monitoring data from the 233.6-m utility tunnel pipe jacking project case is utilized to validate the reliability of the proposed theoretical prediction method. Parametric analyses demonstrate that doubling the subgrade reaction coefficient enhances peak resistance by 80%, while deviation amplitude exerts a 70% greater influence on performance compared to cycle parameters. Slurry viscosity emerges as a critical factor governing pipe–slurry interaction resistance, with each doubling of viscosity causing up to a 56% increase in resistance. The developed methodology proves adaptable across five distinct operational phases—machine advancement, initial jacking, stable jacking, deviation accumulation, and final jacking—establishing a robust theoretical framework for the design and precision control of ultra-long pipe jacking projects.

The construction disturbance caused by pipe jacking is an index that must be strictly controlled in the project. With the wide application of curved pipe jacking in urban underground construction, predicting its ground surface settlement characteristics has become an increasingly important research topic. Based on finite element numerical simulation, a three-dimensional model of curved pipe jacking was established to simulate the construction stage. Compared with the straight pipe jacking, the normal component of jacking force is set in the outer tunnel of the curved pipe jacking to simulate the extrusion of the outer soil caused by the corner of the pipe joint, and the surface settlement characteristics of the curved pipe jacking are explored by changing the pressure value. The research results show that the surface settlement of the curved pipe jacking conforms to the normal distribution as a whole. Compared with the linear pipe jacking, the surface settlement is not symmetrical about the design axis of the tunnel. With the increase of the pressure outside the tunnel, the maximum settlement value of the surface and the difference between the two sides of the axis increase. Compared with the Peck formula, the width of the settling tank of the curved pipe jacking is larger, the convergence rate outside the width of the settling tank is slower, and the settlement trend is more in line with the Verruijt formula. The calculation formula is modified by axis offset distance and ovalization coefficient and modified formula can better reflect the measured engineering data. The research results can provide guidance and reference for the prediction and control of surface settlement of curved pipe jacking.

The disc cutter, which is essential to pipe-jacking to break rock, is the main tool used in this crucial method of tunnel building. The present research is focused on the force of the disc cutter and how well it breaks rock. This paper uses the medium-weathered granite of the Xinjing Mountain Substation - Beifeng Substation as an example to study the effects of penetration and cutting speed on the force and rock-breaking efficiency of the disc cutter. It does this by using ABAQUS to analyze the disc cutter’s operating state under various penetration and cutting speeds and to find the ideal rock-breaking efficiency. The findings demonstrate that: (1) Breaking rock is a discontinuous process that advances continuously. The rock unit beneath the disc cutter ring will change from an elastic to an elastic condition as the disc cutter moves. The rock unit beneath the disc cutter ring will undergo continuous extrusion as the disc cutter moves, changing from an elastic to a plastic state until failing as a result of damage. (2) All of the cutting forces rise as penetration and cutting speed increase, but the rolling force is more affected by penetration and vertical force by cutting speed. When the disc cutter breaks in a straight line, the side force is little. (3) The rock-breaking efficiency increases with a 4 mm penetration and a faster cutting speed.

In pipe jacking construction, thixotropic slurry critically governs lubrication, friction reduction, and ground support. This study evaluated slurry performance through six parameters: specific gravity (SG), pH, fluid loss (FL), water separation rate (WSR), filter cake thickness (FCT), and funnel viscosity (FV). Orthogonal experiments optimizing bentonite, carboxymethyl cellulose (CMC), and sodium carbonate (Na2CO3) ratios established 10 wt.% bentonite, 0.3 wt.% CMC, and 0.4 wt.% Na2CO3 as the optimal formulation. Subsequently, to address performance limitations in challenging conditions, this study introduces hydroxyethyl cellulose (HEC) as a novel additive, with potential advantages under high-salinity and variable pH conditions. Comparative experiments demonstrated that HEC, as a non-ionic water-soluble cellulose, not only significantly increases FV and reduces FL while maintaining SG, FCT, and WSR within acceptable thresholds, but also exhibits superior pH stability compared to CMC. Based on the aforementioned results, interface friction characterization tests were conducted on representative slurry formulations with varying FVs, quantitatively demonstrating the viscosity-dependent friction-reduction performance. Complementary scanning electron microscopy (SEM) analysis of three distinct thixotropic slurry compositions systematically revealed their microstructural characteristics, with microscopic evidence confirming the excellent compatibility between HEC and thixotropic slurry matrix. These findings highlight HEC’s potential as an effective alternative in pipe jacking, particularly in demanding geological environments.

Circular pipe-jacking construction in gravel strata faces significant technical challenges, including high frictional resistance, elevated permeability, and susceptibility to collapse. Optimizing the formulation of thixotropic slurry is crucial for improving the construction quality and efficiency of such projects. This study, based on the Ruyang Water Supply Project of the North Main Canal in the Qianping Irrigation Area, Henan Province, China, systematically investigated slurry formulation using bentonite, soda ash, sodium carboxymethyl cellulose (CMC), polyacrylamide (PAM), and shell powder as raw materials. An orthogonal experimental design was employed to optimize the mix proportions, and the friction-reduction performance was validated through drag-friction model tests. The results indicate that the optimal slurry formulation is: bentonite 8%, soda ash 0.3%, CMC 0.2%, PAM 0.15%, shell powder 4%, and water 87.35%. This formulation exhibits excellent fluidity and thixotropy, facilitating the formation of a stable slurry film. Consequently, the friction coefficient between concrete specimens and gravel soil was reduced by 35.6%. The inclusion of shell powder significantly enhanced the slurry’s cohesiveness and improved the anti-seepage capacity of the surrounding stratum due to its filling effect. The optimized thixotropic slurry effectively mitigates frictional resistance during pipe jacking in gravel strata and enhances the formation’s resistance to collapse. The findings of this study provide a viable technical reference for pipe-jacking projects under similar geological conditions.

Non-lubricated jacking will be predominantly employed to achieve cost reduction and efficiency during the initial stages of rock pipe jacking. However, a lack of comprehensive scientific understanding regarding dry friction characteristics may significantly elevate the probability of major engineering accidents. The pivotal determinant for these characteristics lies in the dynamic friction coefficient, which inevitably undergoes substantial variations due to changes in jacking distance, speed, and pipe weight. Therefore, in this work, a developed dynamic friction coefficient prediction model with a correlation between the shear velocity (representing the speed of pipe jacking), test times (indicating the distance covered during pipe jacking), and normal pressure (reflecting variations in pipe jacking weight) have been proposed. The results consistently demonstrate that the order of grey relational degree for the test numbers, shear velocity, and normal pressure is determined as V < Nt < Fn. When the jacking distance is less than 25 m (500 tests), the dynamic friction coefficient ranges from 0.412 to 0.453; and when exceeding 500 tests, it can be considered that the dynamic friction coefficient stabilizes at approximately 0.404 with negligible variation. In addition, considering the variable dynamic friction coefficient allows for a more precise evaluation of the jacking force, providing a crucial scientific foundation for cost reduction and efficiency engineering development.HighlightsThe dynamic friction coefficient prediction model (DFPM) has been established.The grey relational order of the 3TI factors has been determined as V< Nt< Fn.The DFPM with shear velocity, test times and normal force has been analyzed.The DFPM with jacking speed, distance and pipe weight has been established.The reliability of DFPM has been finally validated.

In this study, the rectangular pipe-jacking tunnel project of the Liuye Avenue West Extension under the Changzhang Highway is used to study highway pavement settlement and deformation during pipe-jacking construction through on-site monitoring. A three-dimensional numerical simulation method is employed to analyse the factors contributing to the significant settlement and rebound of the pavement. This study identifies the fundamental law governing the development of pavement settlement over time. The findings indicate that settlement increases rapidly when the jacking distance reaches approximately 10 m and then stabilizes at a consistent growth level. Furthermore, completion of the jacking of the left pipe leads to a transition in the surface settlement groove from a \"V\"-type distribution to a \"W\"-type distribution. Comparative analysis reveals that horizontal and vertical displacements exhibit similar characteristics, with maximum displacements occurring in the lagging jacking area. On both sides of the axis, the settlement groove curve remains stable within a range of 30–40 m, while the horizontal displacement curve stabilizes within a range of 20–30 m.

A soil pressure balance rectangular pipe jacking project is investigated to find out the interaction of jacking control and ground settlement in Zhengzhou, China. The dimension of the rectangular pipe jacking excavation face is 6.94 m (width) × 4.24 m (height). The tunnel is 35.6 m long and 10.6 m beneath the ground in silty clay strata. The trajectory of the pipe jacking tunneling machine was measured during the whole construction. Meanwhile the construction sets like cutter pressure, jacking force, and grouting pressure were measured with sensors on the pipe jacking machine. The ground settlement was obtained throughout the rectangular pipe jacking process. The results showed that ground settlement variation started from 7.46 m in front of the cutter and ended with 9.79 m away from cutter. The ground settlement can be divided into four phases according to the settlement increasing pattern which is consistent with the distance from the cutter. The ratio of these four phases settlement is approximately 3:3:2:2. The trajectory of the jacking pipe tail has a nonnegligible effect on the settlement distribution characteristics of the ground. The vertical trajectory variation induces lager settlement increasing than horizontal trajectory. Ground settlement increases during the whole progress, but the increasing amplitude decreases with the increasing of cutter pressure, jacking force and grouting.

With the widespread application of large-section quasi-rectangular pipe-jacking tunnels in urban road traffic engineering in China, higher requirements have been put forward to control the influence of their construction on the surrounding environment. To scientifically evaluate the stability of large-section quasi-rectangular pipe-jacking tunnels under-passing existing box culverts, we proposed a novel viscoelastic–plastic model coupling Biot consolidation with non-stationary parameter shear creep (NPSCBCVPM) to fully characterize the coupling effect of consolidation and rheology of saturated soft soil. NPSCCBVPM was developed in Fortran as an ABAQUS user material subroutine. In addition, the NPSCBCVPM was compared with the creep tests of undisturbed soft soil and the generalized Nishihara creep model (GNCM). Finally, the proposed model was applied to the large-section quasi-rectangular pipe-jacking tunnel under-passing existing box culverts of Songhu Road in Shanghai. The results show that NPSCBCVPM are in good agreement with the creep tests of soft soil, and NPSCBCVPM can better reflect the nonlinear rheological characteristics of soft soil than GNCM. Furthermore, the proposed model can scientifically evaluate the viscoelastic–plastic stability analysis of large-section quasi-rectangular pipe-jacking tunnel under-passing box culvert. Further research should focus on developing three-dimensional NPSCBCVPM to better evaluate the spatial response of the box culvert structure and surrounding soil to the entire construction process of large-section quasi-rectangular pipe-jacking tunnels.

Jacking-pipe construction has the advantages of high mechanization, low environmental impact and fast construction speed. It is widely used in the project of underground pipeline under river. However, jacking-pipe grouting under shallow burial conditions is prone to cause surface bubbling problems. Based on the jacking-pipe project of Meichong Lake in Changfeng County, Hefei, this paper discussed the mechanism of grouting surface leakage, and defined the relationship between the critical pressure of jacking-pipe grouting and the ultimate pressure of shear damage of mud jacket. Mechanical model of surface leakage from shallow buried jacking-pipe grouting was established. A general mathematical expression for the grouting critical pressure was derived and a sensitivity analysis was performed. A numerical model was established based on the background engineering, and multiple sets of grouting pressure conditions for simulation and analysis were set up. The results showed that the cohesive force c, the angle of internal friction φ, and the overburden thickness hs were all approximately linearly and positively correlated with the critical pressure of grouting. When the grouting pressure was less than 197.54 kPa the surface settlement increased. When this value was exceeded the surface displacement changed from settlement to uplift and the risk of slurry bubbling increased significantly. The theoretical calculation matched the value of grouting critical pressure from numerical simulation. The actual grouting pressure in the project was lower than the theoretical grouting critical pressure value and no slurry bubbling occurred during construction, which had verified the reliability of the theoretical model. This study can provide theoretical basis and investigation ideas for the setting of reasonable grouting pressure in similar projects.