In transparent soil model experiments, fused quartz stands out as the most promising substitute for natural sand. However, there is still a lack of a comprehensive evaluation system to assess the similarity of its mechanical properties to natural sand. Therefore, a similarity evaluation method based on constitutive model simulation is proposed. First, due to the high friction angle characteristic of fused quartz in transparent soil model tests, multiple oedometer compression and shear box tests were conducted on various gradations of fused quartz. Subsequently, a hypoplastic sand model, which is abundant in natural sand data, stable, and has a straightforward calibration process, was then selected for parameter calibration of fused quartz. Finally, the substitutability of fused quartz for natural sand was evaluated by comparing constitutive parameters and shear box simulation, considering factors such as initial void ratio and confining pressure. The results indicate that the hypoplastic sand model accurately captures the shear behavior of fused quartz. Particles with grain sizes ranging from 0.5 to 2 mm weaken the strength of well-graded fused quartz. The findings also suggest that well-graded fused quartz maintains consistent shear behavior with various natural sands. By contrast, the applicability of single-sized fused quartz is limited.

Aiming to address the problem of selecting the parameters of a soil constitutive model in the calculation of foundation pit stability, this paper proposes a hybrid genetic differential evolution algorithm (GADE) which performs by jumping out of local optima with fast convergence based on the hybrid optimization algorithm strategy and compares the advantages and disadvantages of genetic algorithms (GAs) and differential evolution algorithms (DEs). Three typical test functions were used to evaluate the search efficiency and convergence speed of GAs, DEs, and GADE, respectively. It was found that GADE has the fastest convergence speed and can search for the global optimal solution to the problem, which highlights its excellent optimization performance. At the same time, taking the Shimao Binjiang deep foundation pit as an example, GADE was used to invert the soil modulus parameters of a CX1 measuring point and construct a finite-element model for calculation. The results showed that the simulated calculation curve and the measured displacement curve were in good agreement and the curve fitting reached 95.05%, indicating the applicability and feasibility of applying GADE to identify soil parameters.

Based on the discrete element particle flow software PFC3D, four irregular particles with the same aspect ratio, convexity, and sphericity as the binary pictures are constructed. To examine the influence mechanisms of particle shape on mechanical properties, microstructure, and critical characteristics, an index F characterizing the regularity of the particle shape is introduced. By examining the link between the regularity index and the constitutive parameter, a statistical model is developed to predict the peak friction angle while considering the impacts of relative density and particle shape. The findings demonstrate that decreasing the value of the regularity index always causes an increase in the stress ratio, shear dilatancy, and void ratio. In p'-q, e-logp', and MCN-logp' spaces, the distribution pattern of critical state lines is affected by the particle shape. At the same strain instant, when the particle becomes more irregular, the distribution direction of the maximum contact force of irregular particles tends to be more horizontal to resist the greater external loads. In comparison to spherical particles, the Delta q/p' and Delta phi p of irregular particles increase linearly with the increase of Delta F. The measured and predicted values of the peak friction angle for the statistical model are essentially consistent. The critical parameters ecs,eta cs,phi cs,MCNcs decrease linearly with the increase of the regularity index. The above conclusions serve as a guide for revising the empirical formula.