Shield tunneling inevitably disturbs the surrounding soil, primarily resulting in changes in stress state, stress path, and strain. Modifications to certain parameters, such as shield thrust, shield friction, and soil loss, are made based on the elastic mechanics Mindlin solution and the mirror method, and a calculation expression for additional soil stresses induced by tunneling was derived. Additional soil stresses are calculated using the parameters of the Hangzhou Metro Kanji section. 3D principal stress paths and deviations of the principal stress axes near the tunnel crown, waist, and invert during shield tunneling were obtained by applying a transition matrix orthogonal transformation. These results are compared with experimental data to validate the theoretical solution's accuracy. The stress distribution along the tunneling direction and the 3D principal stress paths and deviations of the principal stress axes in the surrounding soil are determined. The results are as follows: The additional soil stresses along the tunneling direction follow a normal distribution and an S-shape. Under the combined influence of three construction mechanics factors, the shear stress component is approximately 1/3 to 1/2 of the normal stress and should not be neglected. During shield tunneling, the deviation angle of the principal stress axis at the tunnel crown changes from 90 degrees to 180 degrees, with little change in the magnitude of the principal stress. At the invert, the magnitude of the principal stress rapidly increases from 0.25 kPa to 8 kPa, with minimal deviation in the principal stress axis. At the shoulder, the principal stress variation and axis deviation are small. At the foot of the arch, the deviation angle of the major and minor principal stress axes is larger, while the magnitude of the principal stress slightly changes. At the waist, the deviation angle of the major principal stress is larger, and the magnitude of the minor principal stress significantly changes. A strategy for addressing changes in soil stress paths during shield tunnel construction is also proposed.

The mining sector plays a significant role in the economic development of countries by contributing to their gross domestic product. Once the demand for commercialized ore grows, the mining industry looks for new technologies to boost exploration and manage residue disposal. One promising technique to dispose of these residues is dry stacking. This research investigates the behavior of cemented iron ore tailings (IOTs) that use unconfined compression strength (UCS) and triaxial testing. The UCS tests investigated different dosages of cement-tailings compacted blends. In addition, nine triaxial tests were carried out, where six were cured under atmospheric pressure, and three were cured under 300 kPa. Samples were sheared under mean effective stresses of 300 and 3,000 kPa. Both curing conditions were subjected to drained axial loading, constant mean effective stress (p '), and lateral unloading stress paths. The results indicate that the porosity/cement index (eta/Civ) could control the mixtures' UCS. The triaxial tests revealed the effective strength parameters stress dependence. Samples that were consolidated under high stress might experience bond breakage, which leads to a decrease in the friction angle and a tendency toward critical state conditions. No meaningful variation was observed between samples that were cured under stress and atmospheric pressure.

Specimen preparation methods significantly affect indoor sand soil's properties. A theoretical model was developed based on granular thermodynamics to describe the undrained shear characteristics of calcareous sand. We validated the model using specimens prepared through four different methods under various relative densities, stress paths, and confining pressures. The hardening index and granular temperature of this model effectively reflect the impact of specimen preparation methods on the strength characteristics of calcareous sand. The model successfully captured these differences in shear behavior resulting from four preparation methods by adjusting the hardening parameters. Furthermore, this model can accurately describe the influence of stress path changes on the mechanical responses of the calcareous sand granular system by incorporating the third elastic strain invariant.

To essentially explore and quantitatively clarify the mesoscopic failure mechanism of deep weak interlayer zone (WIZ) induced by complex stress levels and stress paths (i.e., particle breakage and orientation, pore morphology, etc.), a semi-quantitative mesoscopic structural damage analysis methodology has been proposed, by involving SEM-MATLAB image processing technique with representative meso-structural parameters after sufficient analysis of basic geotechnical properties of WIZ. Results show that the natural WIZ exhibiting a flocculated structure could be characterized as a well-graded geotechnical material forming main clay minerals, in which most pores are intergranular, with the pore size distribution concentrated in 0.007-200 mu m. Higher initial confining pressure and axial loading tend to intensify the particle breakage degree and particle size distribution characteristics of WIZ more than that of axial and circumferential unloading, in which the stress path II of axial pressure loading and confining pressure unloading under the initial confining pressure of 25 MPa is the most severe with average particle area reduced by 56% and particle Korcak fractal dimension increased by 36%. The broken particles undergoing a series of irreversible dislocation, tumbling and rotation under the action of shear and tensile stress, tend to orient in the direction of 0 degrees-15 degrees, in which particles in stress path IV aggregate in two directions of 0-15 degrees and 60-90 degrees due to the bidirectional unloading. The unloading stress path IV shows the most distinct directional orientation and orderliness, with particle anisotropy increased by 267% and directional probability entropy reduced by 13%. Particle breakage and orientation in WIZ are accompanied by obvious filling, expansion and propagation of the meso-pores and meso-cracks, in which stress path IV under lower confining pressure most affects the morphological complexity of pore and crack boundaries with the pore morphology fraction dimension increased by 13.5%. The quantitative theoretical correlation of macro-meso parameters has been established by the stepwise regression analysis of two most relevant and representative correlation indexes (i.e., Korcak fractal dimension and pore morphology fractal dimension) with the ultimate bearing strength of WIZ, which has been proved to have high fitting accuracy by comparing the regression results with the test measured values. The meso-structural damage mechanism of WIZ under stress paths II and IV could, respectively, match the failure law of structural stress-induced collapse in the spandrel and the plastic squeezing-out failure of WIZ on the high sidewall of underground excavations. Research could provide feasible ideas for the relationship between macroscopic failure and mesoscopic damage of WIZ, as well as the effective basis for the further discussion of macro-meso constitutive model establishment. A semi-quantitative method by SEM-MATLAB image processing technique was proposed to explore the mesoscopic failure mechanism of weak interlayer zone.The particle breakage, particle orientation, pore morphology and crack evolution induced by complex stress paths were quantitatively explored.The quantitative theoretical correlation of macro-meso parameters was established by stepwise regression analysis.The correlation between meso-structural variation and engineering failure mechanism of weak interlayer zone was discussed.