Numerical investigation into ground treatment to mitigate the permanent train-induced deformation of pile-raft-soft soil system

For the bearing rock in geotechnical engineering, it is frequently affected by external loads. This paper adopted different upper limits of stress to carry out cyclic loading-unloading on the sandstone specimens to make them in different damage degrees and analyzed the mechanical mechanism of the damaged sandstone under different stresses. Then, the strength change and energy evolution of sandstone with different damage degrees were analyzed, and the damage of the loaded sandstone was quantitatively characterized. The experimental results showed that the strength and plastic deformation of sandstone after cyclic loading-unloading with different upper-stress limits gradually decreased with the increase of the upper-stress limit. In the loading-unloading stages of cyclic loading-unloading, the elastic modulus increased with the increase of the upper-stress limit. In general, as the number of cycles increased, the total strain energy density and elastic deformation energy density gradually increased, and as the upper-stress limit increased, both of them also increased. The damage factor of sandstone after cyclic loading-unloading, which was characterized by dissipated energy, increased in an S-shape with the increase of the upper-stress limit, and the growth rate first increased and then decreased.

Section: Introductionmentioning

confidence: 99%

Mechanical Properties and Energy Dissipation of Sandstone under Cyclic Loading‐Unloading

Xie

et al. 2021

“…Accordingly, fractures are more easily expanded under tensile shear stress. During a mining excavation, the principal stress level and the principal stress direction change; in other words, the changes in stress state of surrounding rock at any time lead to a certain range of damage to the rock mass on the excavation face [6,7], which will also have significant impacts on the expansion of rock mass cracks and deformation and failure of surrounding rock [8,9]. e expansion and the distribution of unloading cracks are the basis for the study of rock mass failure and surrounding rock stability in underground engineering.…”

Section: Introductionmentioning

confidence: 99%

The Mechanism of Rock Mass Crack Propagation of Principal Stress Rotation in the Process of Tunnel Excavation

Chang

Hua

Zhang

et al. 2021

Rock excavation has experienced complex stress paths. The development of the original crack under the path of principal stress magnitude and principal stress direction is a key scientific problem that needs to be solved in rock underground engineering. The principal stress magnitude dominates the initiation and propagation of the crack and increases rock damage under the action of principal stress rotation. In this study, the theoretical calculation and numerical analysis method have been combined with the crack propagation conditions to study the stress-driven mechanism of brittle rock crack propagation under principal stress rotation. The results show that the “relative initial angle” of crack angle is being updated in time during the principal stress rotation process; once the stress is rotated, it will become the next initial crack angle; the crack propagation direction is deviated under the applied shear load, and it is always in the direction of minimum shear load, leading to a certain degree of inhibition of crack propagation depth in the initial direction. According to the results of numerical simulation, the effect of principal stress rotation caused by mining excavation is obvious and has a certain range of influence depth, the stress of surrounding rock of roadway is the highest within the depth range of 1∼2 m, and the maximum principal stress is as high as 26.89 MPa. The rotation of principal stress direction on the roadway surrounding rock surface is the strongest, which makes the surrounding rock more fragmented, and the middle principal stress and the maximum principal stress rotate about 90° counterclockwise along the Ox axis. Studying the action mechanism of principal stress rotation on fractured rock masses can provide scientific basis for geotechnical engineering design and rock mass surrounding support.

“…Based on the calculation model of Biot's theory, Yu et al [12] and Zheng et al [13] studied the dynamic characteristics of end-bearing piles and pipe piles embedded in saturated soil under horizontal vibration. Gu et al [14] studied the composite foundation treatment of pile raft and soft soil foundation. Jiang et al [15] summarize the research on the axial resistance of rock-socketed piles.…”

Section: Introductionmentioning

confidence: 99%

Impedance of Inner Saturated Soil to Horizontally Vibrating Large‐Diameter Pipe Piles

Xie

2021

An analytical solution for the inner soil impedance of saturated soil to a horizontally vibrating large-radius pipe pile was presented. Based on the porous media theory and the assumption that the vertical normal stress is zero, the closed solution of the inner soil impedance of the saturated soil to the movement of the large-diameter pipe pile is obtained. This analytical solution considers the influence of saturated soil parameters on the impedance of the core soil of large-diameter pipe piles. Through numerical examples, the variation law of the inner soil impedance with pile radius, pile length, dimensionless frequency, compression coefficient, effective permeability coefficient, and porosity was analyzed and the pile radius corresponding to effective inner soil impedance is determined.