A study on the vertical bearing capacity according to the inclination angle of single batter piles and the relative density of sand under vertical loads

This study analyzed the increase in the compressive bearing capacity of single-sloped piles according to the relative density and inclination angle when the batter piles are subjected to a vertical load in non-adhesive sand. An experiment was conducted with inclination angles of 0, 10, 20, 30, and 40, and the relative density of sandy soil was divided into 31% (loose), 53% (medium), and 72% (dense) and compared with the results of the earlier research. As a result of the experiment, when the relative density of the ground was medium and dense, the bearing capacity was greater than that of the vertical pile (0°) at all angles. The tendency noted was that the bearing capacity of the pile increased from vertical to 20° and gradually decreased after 20°. The same tendency was also exhibited by loose sandy soil, but with less bearing capacity than the vertical pile (0°) except for 20°.

Experimental Study on Groutability of Sand Layer concerning Permeation Grouting

Permeation grouting is widely used in grouting engineering because of its low grouting pressure and minor disturbance to the stratum. However, influenced by the complex properties of sand layer and slurry, an accurate prediction of the groutability of the sand layer remains to be a hard work. In this paper, the permeability of sand layer is studied based on a self-designed permeation grouting test device, which considers the different sand particle size, relative density of sand layer, slurry water-cement ratio, and clay content. The influencing factors of sand layer groutability are analyzed, and the different parameters that affect the grouting of sand layer are evaluated, thus proposing a new approach to predict the groutability of sand layer. Results show that the sand particle size and slurry water-cement ratio are positively related to the groutability of sand layer, and the relative density and clay content of sand layer are negatively correlated with the groutability of sand layer. The proposed alternative empirical formula to estimate the groutability of sand layer will help predict the groutability of sand layer with a higher degree of accuracy, which can provide a certain reference for engineering.

Uplift behaviour of axial granular pile anchor encased with geogrid in cohesionless soil

Purpose The purpose of this paper is to provide a cost-effective foundation technique for the design of foundations of transmission towers, heavily loaded structures, etc. Design/methodology/approach Experimental model tests are conducted in a model test tank to find out the effect of length and diameter of geogrid encased granular pile anchors, the relative density of sand and the angle of inclination of the pile from the vertical on uplift behavior of granular pile anchors. Findings The uplift capacity of the geogrid encased granular pile anchor increased with increasing length and diameter of granular pile anchor. Further, increasing the relative density of surrounding soil increased uplift capacity of geogrid encased granular pile anchor system. Moreover, increasing the angle of inclination of loading also increased uplift capacity of whole system. Thus, the proposed system can be effectively used in field for further applications. Originality/value The paper is helpful for the engineers looking for cost-effective foundation techniques for heavily loaded structures.

Dynamic Response of a Single Pile Embedded in Sand Including the Effect of Resonance

In this paper, responses of a single pile embedded in sand soil (loose and dense) under dynamic loading (sinusoidal dynamic vibrations of 0.1 g to 0.5 g) have been investigated by two-dimensional analysis using the finite element method (FEM). Viscous (dashpot) boundaries have been used for taking the boundary effects of far-field into account. The applicability and accuracy of site responses of two-dimensional analysis due to the FEM modelling have been well verified with one-dimensional site responses. The results indicate that the relative density of sand (loose, dense) becomes prominent for the displacements of the pile, specifically under the frequency effects of resonance. While the pile in loose sand causes the displacements of 0.1 m to 0.5 m, the pile in dense sand leads to the displacements of 0.05 m to 0.25 m, proportionally with the dynamic loads from 0.1 g to 0.5 g. Moreover, the displacements reach their peak value at the frequency ratio of the resonance case. Viscous boundaries are found sufficient for modelling excessive displacements due to dynamic loading. However, the displacements reveal that high vibrations (> 0.1 g for loose sand, > 0.2 g for dense sand) influencing the pile deformations are critical for the issues of settlements. This is more significant for the resonance case in order for ensuring sufficient design. Consequently, the findings from the study are promising good contributions for pile design under the dynamic effect.

Experimental Investigation of Square Footing Resting on Sand over Gypseous Soils

This study included (40) tests of loading a square footing (100*100 mm) resting on two layered soils (sand over gypseous soils) using a steel box with the dimensions of (900*900*500 mm). Gypseous soil was brought from Tikrit-University with gypsum content 61%. The tests were divided into two groups. The first groups included (4) tests for gypseous soil only by using the field and maximum densities (14.5, 18.75 kN/m3) respectively, without soaking and with soaking where gypseous soil lost a great value of its resistance. The second group included (36) tests of loading two layers of soil by replacing a layer of gypseous soil by sandy soil with relative density (30%, 60%, and 80%) and depths (B/2, B and 3/2 B). The results showed that the replacement process gave an improvement in the bearing capacity when the gypseous soil was compacted to field density and soaked with a relative density of sand (80%) while the other cases did not have any improvement. The results of loading the two layers of soil also show that the soaking of gypseous soil under the sandy layer affects on the resistance of sand through reducing it especially when the depth of sand was (B/2) this effect decreased gradually with increase in the depth of the sandy layer.

Effect of Gradation and Particle Size on Correlations between DCP Index (ASTM D6951 – 03) and Relative Density for Sand

This research study was mainly focus on performing dynamic cone penetration tests according to ASTM D691 - 03 with various relative density on different gradation (poorly graded and well graded) of sand. Sand samples were collected from different region of Gujarat viz. Khanpur, Sevaliya, Ahmedabad. Well graded sand samples were prepared by mixing in different proportions of sand samples collected from above locations. Dynamic cone penetration tests were carried out in Plexiglas tank (60 cm × 60 cm × 75 cm) on three different poorly graded and three different well graded sand at different relative density of 30, 50, 65, 75 %. Relative density of sand samples were determined according to IS : 2720 (Part 14) – 1983. Dry sand has been filled in tank up to 70 cm height of tank. Tamping was done with rammer (30 cm × 30 cm × 1 cm) of 9.5 kg weight to achieve desired density. Desired depth of penetration is 60 cm. Dynamic cone penetration tests were performed according to ASTM D6951-03.