True triaxial tests were conducted on artificially frozen sand. The effects of the intermediate principal stress coefficient, temperature and confining pressure on the strength of frozen sand were studied. The stress-strain curves under different initial conditions indicated a strain hardening. In response to increases of either the intermediate principal stress coefficient or the confining pressure or to a decrease of temperature, the strength typically increased. Furthermore, a new strength criterion was proposed to describe the strength of artificially frozen sand under a constant b-value stress path, combining the strength function in the p-q and pi planes. Considering the low confining pressure, the strength criterion in the p-q plane fitted the linear relationship in the parabolic strength criterion well. The strength criterion in the pi plane was combined with stress invariants, and a new strength criterion was established. This criterion considers unequal tension and compression strength, and integrates temperature. Test results indicated its validity. All parameters of the strength criterion could be easily determined from the triaxial compression and triaxial tensile tests.

This study reveals the mechanical behavior of silt in the Yellow River floodplain under 3D stress. A true triaxial apparatus was used to conduct consolidated drained shear tests under different intermediate principal stress coefficients (b) and consolidation confining pressures to investigate the influence of the intermediate principal stress on the deformation and shear strength of silt. The stress-strain curves exhibited strong strain-hardening characteristics during shearing. Due to enhanced particle interlocking and microstructural reorganization, the silt demonstrated complex b-dependent deformation and strength characteristics. The cohesion rose with increasing b, whereas the internal friction angle followed a non-monotonic pattern, increasing and decreasing slightly as b approached 1. The strength envelope of the silt fell between that predicted by the Lade-Duncan and the extended von Mises strength criteria., which is best predicted by the generalized nonlinear strength criterion when the soil parameter alpha was 0.533. The findings reveal the stress-path-dependent mechanisms of Yellow River floodplain silt and provide essential parameters for optimizing the design of underground engineering projects in this region.

The contact network of granular materials is often divided into strong and weak subnetworks, which play different roles in micromechanics. Within the strong contact network, there exists the largest connected component, that is, the largest cluster, which may connect system boundaries and could be the most important structure in force transmission of the whole system. This paper concerns the particular features of the largest cluster in the strong contact network of granular materials, by considering the combining effects of loading path and particle shape. A series of true triaxial tests with various intermediate principal stress ratios are conducted for granular assemblies of different shaped particles using the discrete element method (DEM). Both the macroscopic stress-strain responses and the microscopic topological changes of the contact network are investigated. It is found that both particle shape and loading path will influence the shear strength and the topological features of the strong network. The threshold zeta$\zeta $ (the ratio to the average force) is used to distinguish the strong and weak networks, and a critical threshold can be identified by comparing the network-based metrics. The largest cluster within the strong network approaching the critical threshold can span the boundaries in each direction with minimum contacts, which occupies a small portion of particles and contacts but transmits a considerable portion of the applied stress. In addition, the similar contribution weight of the largest cluster to the deviatoric stress is identified for granular materials with different particle shapes.

True triaxial tests of cyclic loading and unloading were carried out on remodeled loess, and the effects of the anisotropic consolidation ratio (K=sigma 1c/sigma 3c), intermediate principal stress coefficient (b=sigma 2-sigma 3/sigma 1-sigma 3), and cyclic loading on the deformation characteristics of the loess were analyzed. The results show that principal strain develops in two stages: a rapid initial increase followed by a slower increase until stabilization. Plastic volumetric strain is found to increase with increases in cyclic loading, anisotropic consolidation ratio, and intermediate principal stress coefficient. After normalization, the consolidation mode has a large effect on the plastic volumetric strain ratio, while the intermediate principal stress coefficient has a smaller effect. All types of plastic shear strain exhibit shear shrinkage, increasing with increases in cyclic loading and the intermediate principal stress coefficient, with no obvious relationship with the anisotropic consolidation ratio. After normalization, the consolidation mode and the intermediate principal stress coefficient have significant effects on the plastic shear strain ratio.