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PVC pipe jacking is prone to cause yielding or buckling under the jacking force and may lead to engineering failure. The relationship between the buckling modes, ultimate bearing capacity, different diameter–thickness ratios, and length–diameter ratios of PVC pipe jacking under different load forms was analyzed. The calculation methods for allowable jacking force and the single allowable jacking distance are obtained through theoretical analysis and three-dimensional finite elements. The buckling mode of the pipe under uniform load changes from symmetric buckling to asymmetric buckling and then to the overall Euler buckling form as the length–diameter ratio increases. The ultimate bearing capacity of the pipe approaches the theoretical value of yield failure when L/D ≤ 6. For L/D > 6, the pipe undergoes buckling, and the ultimate bearing capacity determined by the axial buckling value and the buckling load can be calculated according to the long pipe theory formula when L/D > 8.5. Under eccentric loads, the failure mode transitions from local failure to Euler buckling with increasing pipe length. The ultimate bearing capacity of pipe is obviously lower than that of uniform load, but as the length–diameter ratio increases, this difference decreases until it becomes consistent. [ABSTRACT FROM AUTHOR]

A new type of prefabricated foundation for onshore wind power was proposed in this paper. The stress and bearing mechanism of the new foundation was explored through theoretical calculation and finite element analysis. The results show that compared with the extended foundation in the same position, the amount of concrete in the new foundation is reduced by 30.00%, and the amount of rebars are reduced by 34.69%. The new prefabricated foundation has been inspected and calculated according to the specification. The calculation results indicate that the stress and initial reinforcement of the foundation meet the specification requirements. The bearing capacity, inclination rate, deformation, and stability of the foundation meet the requirements. Through finite element analysis, it is further confirmed that the structure meets the requirements of wind turbine operation, and the overall force meets the requirements of various indicators. The stress distribution of the foundation concrete and rebars is reasonable and uniform, and the load transfer is great. Also, the maximum stress of rebars and concrete does not exceed the specification limit, and the concrete remains intact without cracking or damage. The new foundation structural design and theoretical analysis were reasonable and accurate, and can be put into application in the future. [ABSTRACT FROM AUTHOR]

• Developed pipe-swallowing technique for pipe replacement in sand. • Evaluated it by monitoring stress, pulling force, and vertical displacement. • Established an equation to predict vertical displacement. Pipe bursting, a trenchless technique for replacing underground pipes, may induce ground movements that potentially harm nearby structures. To address this issue, the innovative pipe-swallowing method has been developed. Compared to pipe bursting, this method reduces surface disturbances and offers better protection for the newly installed pipes. In this study, a uniaxial test machine was employed in preliminary tests to enhance the structural design of the pipe-swallowing device. Follow-up experiments conducted in a 3.0 m × 1.8 m × 1.5 m test box measured the pulling forces and three-dimensional surface displacements involved in replacing a buried HDPE pipe, 315 mm in diameter, with another of the same size. The most effective pipe splitting force, determined as 32 kN, was achieved using three blades with 30° V-edges and 120° intersection angles, leading to the lowest observed peak pulling force. This force predominantly offsets the friction between the new pipe and the soil, the interaction of the swallower with the soil, and the force required for pipe splitting. The pipe-swallowing process leads to persistent alterations in the pressure distribution around the pipe, causing ground disturbances extending roughly ± 650 mm. The maximum vertical displacement measured was 21 mm, aligning with the modified Gaussian distribution model. These findings affirm the practicality of the pipe-swallowing method and pave the way for future improvements in finite element models for this application. Furthermore, expanded research exploring a range of soil types and pipe materials, including both flexible and brittle varieties, is crucial for advancing the efficiency of this technology. [ABSTRACT FROM AUTHOR]

Horizontal Directional Drilling (HDD) is an environment-friendly and high efficient method for underground utilities and pipelines crossing. The formation of cuttings bed, due to low Cuttings Transport Performance (CTP) in large-size HDD, has resulted in the overwear of reamer and been required additional borehole cleanups which will result in high construction risk and extending the work period. In order to investigate the formation and broken mechanism of cuttings bed, two tests were designed to determine the potential effect of mud rheological properties, flow rate, borehole inclination and rotation of drill rod on the cuttings bed state. The drill rod laid down at the invert of the borehole, broke the stability state of cuttings bed and take some cuttings away from the cuttings bed, which causes an incremental trend of CTP, even for the cuttings bed consisting of 8–12 mm diameter cuttings. The observations and results of the tests indicated that drill rod rotation had a positive impact on the instability of cuttings bed, whereas, YP of mud, average velocity of mud and borehole inclined shown a limited effect on it for the large-scale HDD reaming. Further study is needed to determine the details about drill rod behavior and extend the tests results by the finite element method. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel model to quantify load-carrying capacity of intact double-cage RCPs. • Novel model to quantify residual bearing capacity of corroded RCPs. • FEM models of intact and corroded RCPs set at TEBT condition. • TEBTs for the verification of the calculation and simulation results. Reinforced concrete pipes (RCPs) are widely used as jacking pipes in various infrastructures, such as sewers, tunnels, and pipe galleries. However, owing to the presence of harmful chemicals and microorganisms in the surrounding environment, the pipe gradually corrodes, thereby thinning the pipe wall and lowering the residual bearing capacity (RBC) of the structure. For the daily maintenance of the RCP, the RBC should be evaluated precisely to ascertain the service status of the pipe, and if necessary, timely rehabilitation can be performed to yield the optimal repair outcome and cost efficiency. In this study, quantitative models for RBCs of both intact and corroded RCPs are proposed; these models are based on the plastic collapse failure mode of rigid pipe. Additionally, the impact of uncoordinated deflection between concrete and reinforcement has also been characterised. A series of numerical simulations were developed on the basis of the finite element method (FEM) to evaluate the RBC of corroded RCPs, and the FEM results are consistent with those of the quantitative model. Finally, three-edge bearing (TEB) tests were conducted by incorporating both intact and corroded RCPs. The results of the TEB tests also revealed the reliability of the quantitative model. [ABSTRACT FROM AUTHOR]

• The full-scale tests results of damaged RCPs rehabilitated by centrifugal spraying tech were introduced. • A 3D finite element model of "Damaged Pipe-Repair Lining" structure was established based on CDP and Cohesive Zone models. • Influence rule of related variables on the structure bearing capacity was obtained. • New design method of centrifugal spraying technology for trenchless restoration was elaborated. There has been growing interest in using trenchless technology, especially centrifugal spraying techniques, to renovate the sewer pipe network in China. In this study, a damaged reinforced concrete pipe (RCP) (i.e., 14.7% vertical deformation) with one-meter diameter is rehabilitated by centrifugally spraying on a 50 mm thickness mortar lining. The ultimate (D u) D-load only increased by 2% compared to host pipe's residual strength; however, other pipe properties exhibited improvement. Based on the behavior of two experimental results, finite element models were established, and an innovative pipeline damage quantization model was proposed. Through parameter sensitivity analysis, the effects of interface strength and fracture energy on pipe bearing capacity were studied. It was discovered that interface bonding performance affected the service load of the rehabilitated pipe. From the analysis of pipeline initial state deformation influence on the repaired structure bearing capacity, it was discovered that selecting a reasonable repair time point can effectively improve the functionality of the pipe network and reduce repair costs. An analysis of RCPs structural repair with a vertical deformation larger than 14% revealed that it is difficult to repair damaged pipes only employing mortar spraying. A structural design method based on the service load and ultimate load is presented in this paper. [ABSTRACT FROM AUTHOR]