Simulation analysis of the effect of single-chamber double-line pipe jacking through different soil materials on surface uplift and subsidence

Abstract

This article is based on the relocation project of the 330 kV overhead line in Xi’an, China. In this paper, the soil settlement under different jacking depths was calculated by using the modified Peck’s formula. Meanwhile, by modeling in ABAQUS, the jacking process of a single-chamber double-line large diameter pipeline under different soil conditions was simulated, and the ground deformation data under the different simulated working conditions were obtained. The results of the two methods were compared with the construction monitoring results, and it was found that the finite element simulation results were closer to the actual results. The control variable method was used in the analysis of the surface soil deformation law to analyze the effect of different soil parameters and pipe jacking depths on surface soil deformation. Finally, the best soil conditions applicable to single-chamber double-line large diameter pipe jacking construction were obtained through comparative analysis. The results show that (1) when using double-line construction, the maximum surface settlement under different soil conditions is located 11–15 m from the centerline of the soil above the pipeline, the minimum settlement location is inside the isolation pile, and with the increase in jacking distance, the settlement at the same section of the surface will gradually decrease and finally produce a small uplift. (2) In the first jacking, the settlement of powder clay is the largest, and the maximum settlement points in the surface section are more distributed. The maximum settlement value is approximately 11.66 mm. The settlement of powder soil is the smallest but produces a certain uplift deformation, and its maximum settlement is more concentrated in the surface section. After the comparison of deformation and soil parameters, loess-like soil is more suitable for single-compartment double-line large diameter pipe jacking construction. (3) When the top pipe burial depth changes, the greater the burial depth is, the smaller the settlement but the greater the lateral influence range. In the soil parameters, the modulus of elasticity only changes 3 MPa, and the settlement change value is approximately 5 mm. By changing the parameters, it can be obtained that the larger the modulus of elasticity of the soil is, the smaller its deformation. The larger the internal friction angle of the soil is, the smaller its deformation, but the maximum value of settlement change is only 1.7 mm, which means that the change in the internal friction angle has little effect on the soil deformation.

Comparative research on the pipe-soil frictional resistances of circular and rectangular pipe sections during trenchless pipe jacking

“…Thus, in the practice of trenchless pipe jacking engineering, pipe-soil frictional resistance is the key factor to be considered when determining the jacking force of equipment. The reasonable estimation of jacking force directly determines the success or failure of trenchless pipe jacking operation, it also has great influence on the aspects of safety, resource allocation and comprehensive cost control during operation [1][2][3][4][5][10][11][12][13][14][15][16][17][18][19].…”

“…(2) How to effectively reduce the pipe-soil frictional resistance during pipe jacking process? At present, the common practice is to inject thixotropic mud into the gap between the outer wall of pipe sections and the formation, so that the slurry jacket is formed around the outer wall of pipe sections to achieve the effect of lubrication and friction reduction [ 1 – 5 , 9 – 12 , 16 ].…”

“…Many pipe jacking engineering practices show that if the pipe-soil frictional resistance is too large, it may cause the engineering accidents such as jacking difficulty, pipe section cracking, the back support wall of launching shaft damage, etc. [1][2][3][4][5][6][7][8][9][10][11][12][13]21] Thus, there are two key aspects to ensure the smooth implementation of trenchless pipe jacking operation as follow: (1) How to accurately estimate the jacking force for the construction design of pipe jacking operation? Currently, the main estimation methods of jacking force include theoretical analysis, experimental test, theoretical calculation equations, empirical estimation equations, and field monitoring, etc.…”

“…Currently, the main estimation methods of jacking force include theoretical analysis, experimental test, theoretical calculation equations, empirical estimation equations, and field monitoring, etc. However, each estimation method has its own applicable conditions and limitations, it is difficult to provide a general guidance for pipe jacking engineering practice [1][2][3][4][5][10][11][12][13][14][15][16][17][18][19]. (2) How to effectively reduce the pipe-soil frictional resistance during pipe jacking process?…”