Abstract
In the present study, based on previous research results, a finite element method that considered the grouting pressure and displacement control of the tube-soil side friction coefficients was established for the purpose of estimating the jacking forces of large sections of rectangular pipe jacking. Furthermore, the pipe jacking project of Zhong-Zhou Avenue was taken as an example in this study, in which the rectangular pipe jacking models A1 and B1 under silty clay geological conditions were established. The two estimation models were verified using the pipe jacking cases A2 and B2, respectively. The estimation model can effectively estimate the jacking force, and the rectangular jacking force is distributed as a logarithmic function with the jacking distance. The shallow buried rectangular pipe jacking has some common characteristics in buried depth, grouting pressure, the length-width ratio of outer diameter, construction geological conditions, and so on. The main independent factors that affect the jacking force are the buried depth and the outer perimeter of the jacking pipe. Based on the numerical model of case A1 and case B1, the logarithmic functions of jacking force of case A1 and case B1 with jacking distance were obtained by changing the buried depth. The calculation formula of the jacking force can reflect the variation law of the jacking force to some extent.
Highlights
Yen and Shou [6] first proposed that jacking forces could be accurately estimated using finite element methods of displacement control for jacking pipes. e jacking forces at different jacking positions were first calculated by displacement control finite element methods. en, the curve fitting relationships between the jacking forces and jacking distances in the middle sections of jacking pipes were successfully obtained through data fitting. e jacking forces were determined to be related to the construction conditions and jacking distances
Grouting Pressure Programs of the Models. e jacking forces of the rectangular jacking pipes consisted of the resistance at the ends of the jacking heads and the resistance at the sides of the outer walls of the pipes. e lateral resistance was found to be related to the grouting pressure of the mud sleeves and the lateral friction coefficients of the outer surfaces of the pipes
It was observed that the friction coefficients between the outer walls of the jacking pipes and the soil could be greatly reduced by the mud sleeves formed by the bentonite plasticizer, which were usually 0.2. en, by applying the displacements of the pipe joint lengths in the jacking direction (i.e. 1.5 m), the initial sections of the first pipe joints in front of the jacking heads could be selected in order to search the stress components of each element node in the examined sections along the jacking direction, which were essentially the longitudinal stress components. erefore, this study only focused on the distributions of the longitudinal stress σyy
Summary
It has been found that, through numerical simulations, the contact mechanical behaviors between the surrounding soil and the outer walls of the jacking pipes can be quickly determined. Regarding to the stress control method, the side friction resistance levels of the pipes and the surrounding soil are obtained through various empirical and theoretical equations. Is effectively opens the door for finite element methods of displacement control to accurately simulate pipe jacking processes. Yen and Shou [6] first proposed that jacking forces could be accurately estimated using finite element methods of displacement control for jacking pipes. In this study, jacking forces at different jacking positions were obtained by applying given displacements to sections of the jacking pipes in a launch shaft using the numerical analysis software ABAQUS [7]. Jacking Force Estimation Models of Rectangular Pipe Jacking ere have been various studies conducted to investigate the jacking forces of circular pipes using theoretical derivations
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