Vertical Pipe Jacking Force Prediction Across Changing Soil Failure Modes
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Solution Overview
Problem
Existing methods for calculating jacking force in the vertical jacking method are empirical and lack theoretical basis, failing to account for the dynamic changes in soil resistance during the construction process, leading to inaccurate predictions of maximum jacking force.
Innovation Solution
A method that calculates jacking force by considering three components: head resistance, friction force between the pipe and soil, and pipe self-weight, using stress models that account for spherical hole expansion and shear failure based on soil layer thickness, with specific formulas for each model.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If empirical algorithms are used to calculate jacking force, then calculation simplicity is improved, but prediction accuracy deteriorates
Solution Approach 1:
The patent transforms the jacking force calculation from a static empirical approach to a dynamic parameter-based approach. It divides the jacking process into multiple stages (initial jacking, normal jacking, and final jacking) and assigns different calculation parameters to each stage. The head resistance coefficient λ varies from 1.0-1.5 in initial jacking to 0.5-1.0 in normal jacking, and the soil resistance distribution changes from concentrated at the top to distributed along the pipe length, enabling accurate prediction throughout the construction process
Solution Approach 2:
The patent segments the jacking process into distinct phases (initial jacking, normal jacking, and final jacking) with different resistance characteristics. It also segments the soil resistance into head resistance at the pipe cover and friction resistance along the pipe-soil contact surface. This segmentation allows each component to be calculated with appropriate parameters, improving overall prediction accuracy while maintaining calculation feasibility
2Device complexity
If static jacking force calculation is used, then calculation complexity is reduced, but dynamic change of soil resistance is not captured
Solution Approach 1:
The patent introduces dynamic characteristics into jacking force calculation by considering the changing soil resistance throughout the jacking process. It models the head resistance as varying with jacking depth and soil layer characteristics, and the friction resistance as distributed along the pipe length with intensity varying by depth. This dynamic approach captures the evolving soil-pipe interaction without requiring complex numerical simulations
3Loss of time
If simplified head resistance calculation is used, then computation time is reduced, but prediction accuracy of maximum jacking force deteriorates
Solution Approach 1:
The patent performs preliminary classification of soil conditions and jacking stages to select appropriate calculation parameters before detailed computation. It establishes predetermined ranges for head resistance coefficient λ (1.0-1.5 for initial jacking, 0.5-1.0 for normal jacking) and soil friction coefficients based on soil type. This preliminary parameter selection enables rapid calculation while ensuring accuracy for maximum jacking force prediction
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Provides a more accurate and comprehensive theoretical basis for predicting jacking force throughout the construction process, aligning closely with actual measurements and reducing prediction errors.
Implementation Method 1
when the overlying soil layer is higher, and if Fyb>Pu*s, a spherical hole expansion problem occurs at the vertical pipe cover, then Fy=Fyb=π*Pu*Rd2
Implementation Method 2
when the overlying soil layer is lower, and if Fyb<Pu*s, a shear failure problem occurs at the vertical pipe cover, then Fy=Fys=Gs+Gw+Fcf
Implementation Method 3
Ff=μ*K*π*D*L2*[γ'*h+γw*h+γw*l*(H+h)/2]
Data Source
AI summary
A jacking force prediction method for a whole construction process by a vertical jacking method, based on a spherical hole expansion theory and a shear failure principle, uses two jacking force calculation models. The models include a spherical hole expansion-sliding friction model and a shear failure-sliding friction model, and corresponding calculation formulas are deduced. When an overlying soil layer is high and the jacking force calculated by adopting the spherical hole expansion-sliding friction model is relatively small, a spherical hole expansion problem occurs at a vertical pipe cover. When the overlying soil layer is relatively low and the jacking force calculated by adopting the shear failure-sliding friction model is relatively small, a soil body failure form at the vertical pipe cover is shear failure.