Calcareous sand is one of the main building materials in the construction of islands and reefs, and its shear property is very important for predicting their strength and deformation. However, the correlation research on the shear properties of calcareous sand is limited. In this paper, a series of the triaxial consolidation drainage shear tests of calcareous sand with relative densities (Dr) of 70% and 90% under confining pressures of 100, 200, 400 and 800 kPa were carried out by a triaxial testing apparatus, and the effects of relative density and confining pressure on the deformation and strength characteristics of calcareous sand were analyzed. The results show that the stress–strain curves of calcareous sand show a strain softening characteristic, and both peak deviatoric stress and failure strain increase with confining pressure, but the increase in failure strain is restrained when the confining pressure is larger than 400 kPa. The initial shear modulus of calcareous sand is positively correlated with confining pressure. Additionally, the molar circular envelope of calcareous sand is linear in the range of 100~400 kPa, but it deviates from linear when confining pressure exceeds 400 kPa. The critical state line (CSL) of calcareous sand is nonlinear, with almost the same exponent for calcareous sand with different relative densities. The research results have important reference value for the foundation construction of islands and reefs.

A total of 9 tests were carried out with 30 mm and 78 mm caliber scaled projectiles penetrating into granite targets. The penetration depth, crater diameter, and mass loss rate were examined and discussed. The results indicate that the dimensionless penetration depth of large-caliber projectiles is 20% greater than small-caliber projectiles. Based on the description of static resistance R_a in the Forrestal semi-empirical formula, the size effect of dimensionless penetration depth can be attributed to the size effect of static resistance R_a, and it can be seen that the penetration static resistance of projectile A is 40% higher than that of projectile B. Numerical simulations of projectile penetration into granite targets were conducted using the finite element program ANSYS/LS-DYNA. In terms of penetration depth and crater damage, the numerical simulation results agree well with the test data. This suggests that the selection of parameters was reasonable. The influence of compressive strength, projectile striking velocity, mass, diameter, and caliber–radius–head (CRH) ratio on the static resistance R_a were studied by RHT model parameterization. Based on the numerical results from the parametric study, an empirical formula was derived to predict the static resistance R_a.

In this paper, the straight-wall-arch structure in the rock medium is taken as the research object, and the high-pressure plane charge loading test technology is adopted to study the anti-explosion performance of different types of structures under the explosion loading. Three types of structures, which are individually built with the high-performance reinforced concrete, the C30 reinforced concrete, and the C30 reinforced concrete with a foam concrete backfill layer as well, are tested, and the dynamic responses and damage characteristics of these structures are investigated. The test results show that under the condition of the same plane charge explosion loading, in the vault of the high-performance reinforced concrete test section appears a through-tensile crack with a largest transverse relative displacement between the two straight walls, and the composite structure test section only shows an intermittent crack at the arch foot, which represents a slight damage mode. Meanwhile the arch spring of the C30 reinforced concrete test section suffers a through-compression shear failure with a largest vertical relative displacement between the vault and the floor, which represents a moderate damage mode. Therefore, adopting the high-performance reinforced concrete, and the C30 reinforced concrete with the foam concrete backfill layer, can effectively decrease the damage degree of the rock structures. Compared with the C30 reinforced concrete, the high-performance reinforced concrete can improve the resistance of the structure by improving the structural strength and strengthening its capacity to absorb waves and energy dissipation, and the foam concrete backfill layer can significantly reduce the lateral and vertical relative displacement of the structural free surface and the peak stress of the structural inner layer. The composite structure test section of the C30 reinforced concrete with foam concrete backfill layer appears to be an excellent anti-explosion performance property.