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Carbonated sands, also referred to as calcareous sediments, are a common type of soil in marine environments such as the West Australia Continental Platform, South China Sea, Persian Gulf and Oman sea and many parts of the world. During pile driving in such soils, imposed shear and volumetric strain to particles, crushing occurs which leads to change in the particle size distribution as well as interface properties of the soil-pile system. In this study, two types of sands (siliceous Firoozkooh-161 and carbonate Hormoz sand) and three types of materials (steel, wood and concrete) have been selected and were investigated using a direct shear and a tall oedometer apparatus for the prediction of the sand-pile interaction properties considering particle crushing. The smoothness and roughness of materials as well as soil relative density, and shearing rate on the interface properties were examined. Based on the results, smooth steel, wood at the direction of vessels, rough steel, smooth concrete, wood at the right angle to vessels, and rough concrete represent the lowest to the highest interface shear strength, respectively. Results revealed, increasing soil relative density leads to an increase in the interface friction angle. The results also emphasized that increasing the vertical stress leads to increasing in the breakage index both dense and loose states, however, the amount of particle increases with density. Particle crushing also decreases significantly when soil interact with smooth surfaces. Furthermore, increasing the shearing rate enhances the shear strength and reduces particle crushing. It also investigated that Hormoz sand compared to Firoozkooh sand exhibits a higher level of particle breakage due to the shape and texture of carbonated particles. Finally based on the achievements of this research, the limit values for skin friction bearing capacity of piles driven in carbonate and siliceous sands proposed in ARGEMA and API approach were examined. [ABSTRACT FROM AUTHOR]

Assuming plane strain deformation instead of three-dimensional behaviour of nailed convex trenches in the design process might lead to life and property losses during the operation period. In this research, the behaviour of convex nailed trenches was investigated. Various physical models with three-dimensional and plane strain conditions were tested using a geotechnical centrifuge. The failure acceleration was measured as well as the walls deformations. Results showed that convex nailed trenches had less stability than long nailed trenches. It was also revealed that the connection quality of the trench sides at their intersection had a significant effect on increasing stability. Finally, a method was proposed to increase the stability of the convex trench in which the two sides of the trench are sewed together by a series of diagonal nails. Using this method to reinforce the model resulted in the maximum stability and minimum deformation of the convex trench. [ABSTRACT FROM AUTHOR]

Anisotropy is one of the inherent characteristics of sedimentary deposits, which affects the behaviour of soils. Owing to the abundance of calcareous sands in many coastal and offshore areas and the construction of massive structures in these regions, investigating the effect of anisotropy on the shear strength of these types of soils is necessary. However, only few studies have investigated the influence of anisotropy on the behaviour of carbonate soils. In this research, the anisotropic behaviour of the carbonate sands of Hormoz Island, which is located north of the Persian Gulf, was investigated through rotating the bedding plane relative to the shear plane utilising a modified direct shear apparatus. The experimental investigations were conducted on different specimens with various densities and normal stresses in dry and saturated conditions. The experimental results evidently show that the effect of anisotropy is strongly related to the normal stress and density of the specimens. In addition, the effect of anisotropy is pronounced at high normal stresses for relatively dense samples. Furthermore, the samples at dry and saturated conditions reflected similar behaviour. [ABSTRACT FROM AUTHOR]

Two marine calcareous deposits as crushable soils and a siliceous sand as a noncrushable soil were used in this study to compare their monotonic response. Undrained monotonic triaxial tests were conducted on samples, which were prepared in different relative densities and consolidated under various confining pressures. The location of phase transformation point in undrained response of the sands in different initial conditions was evaluated. The effect of important parameters including relative density, confining pressure, particle shape, and particle breakage on phase transformation point was assessed. The input energy applied per unit volume of the soils was used to interpret the shearing response of crushable and noncrushable soils. The results showed that calcareous sands have more tendencies in contraction. Particle shape and breakage play a key role in engineering behavior of crushable soils. [ABSTRACT FROM AUTHOR]

This paper presents an innovate approach to simulate the stress-strain behaviour of sands subjected to large amplitude regular cyclic loading. New prediction correlations were derived for damping ratio (D) and shear modulus (G) of sand utilizing linear genetic programming (LGP) methodology. The correlations were developed using several cyclic torsional simple shear test results. In order to formulateDandG, new equations were developed to simulate hysteresis strain–stress curves and maximum shear stress (τmax) at different loading cycles. A genetic algorithm analysis was performed to optimize the parameters of the proposed formulation for stress-strain relationship. A total of 746 records were extracted from the simple shear test results to develop theτmaxpredictive model. Sensitivity and parametric analyses were conducted to verify the results. To investigate the applicability of the models, they were employed to simulate the stress-strain curves of portions of test results that were not included in the analysis. The LGP method precisely characterizes the complex hysteresis behaviour of sandy soils resulting in a very good prediction performance. The proposed design equations may be used by designers as efficient tools to determineDandG, specifically when laboratory testing is not possible. [ABSTRACT FROM AUTHOR]