Number Of Reinforcement Layers Research Articles

BEARING CAPACITY OF SQUARE FOOTING ON GEOGRID-REINFORCED LOOSE SAND TO RESIST ECCENTRIC LOAD

This research presents and discuss the results of experimental investigation carried out on geogrids model to study the behavior of geogrid in the loose sandy soil. The effect of location eccentricity, depth of first layer of reinforcement, vertical spacing, number and type of reinforcement layers have been investigated. The results indicated that the percentage of bearing improvement a bout (22 %) at number of reinforced layers N=1 and about (47.5%) at number of reinforced layers N=2 for different Eccentricity values when depth ratio and vertical spacing between layers are (0.5B and 0.75B) respectively.

Behavior of vertical piles embedded in reinforced sand under pullout oblique loads

The behavior of vertical single piles embedded in reinforced and non-reinforced cohesionless soil has been investigated with the help of small-scale model tests. These piles were installed in sand of different relative densities (<i>D_r</i> = 30 and 60%) and subjected to pullout loads of different inclinations. The model pile pullout tests were conducted using three reinforced concrete circular piles with different surface conditions (smooth, smooth with necking and bulging, and rough). The influence of sand reinforcement with geogrid on the uplift performance of the model piles was investigated. These investigations were carried out by varying the inclination of the pullout load, the embedded depth of reinforcement, the number of reinforcement layers, and the length of the reinforcement layer. The test results show that the pullout resistance increases with the concrete surface roughness, sand density and the inclusion of a reinforcing layer. It was also found that the effectiveness of the reinforced layer is dependent on the concrete surface roughness. This paper also discusses the effects of these parameters on the relative ground movement near the pile surface.

Effect of Reinforcement on Bearing Capacity of Loose Sand Foundation and Deformation Behavior of Buried Flexible Pipes

Abstract The present study investigates if improving the bearing capacity of foundations with reinforcement layers could reduce deflection of a pipe buried under reinforced sand. A series of model tests were conducted to examine the bearing capacity of foundations and deformation behavior of a pipe according to the number of reinforcement layers, reinforcement material, and buried depth of pipe. The results showed that bearing capacities significantly improve by increasing the number of reinforcement layers up to two layers, however no further improvement in bearing capacity was observed with more than two layers. The reduced settlement caused by improved bearing capacities with embedded reinforcements had little effect on resistance to deflection when the depth of the buried pipe was greater than the width of the footing. However, the resistance to pipe deflection by installation of reinforcement was greatly increased when installed at a depth less than the width of the footing.

Numerical model to predict the settlement response of two nearby foundations due to geotextile slippage

In this paper, a numerical study is undertaken on the settlement response of two nearby flexible loads resting on a reinforced granular bed underlain by a soft soil, considering plain strain loading conditions. The finite element code PLAXIS-8 has been used. The granular fill, soft soil and geosynthetic reinforcements are considered as linear elastic materials. The geosynthetic reinforcement is modeled with interface elements for allowing slip between the soil and reinforcement. When no interface elements were used, the geosynthetic reinforcement was modeled as if there were no slip. It appears that allowing slip has a negligible effect on the settlement predicted. The results obtained from the present investigation showed that as the number of reinforcement layers increase up to three layers, the vertical stresses in the loaded region decreases causing maximum settlement reduction at a decreasing rate of 16% and 20% for 3-layers without and with slippage respectively. A parametric study has been carried out to bring out the effect of slippage of the reinforcement layer on the settlement response in dry and saturated soils. The increase in the settlement is not significant when the slippage of the reinforcement is considered. An interesting observation in this note is that the settlement was about 10% less when there were two nearby footings compared to when there was only one. The interaction between the footings resulted in reduction in the settlements, possibly due to reduced confining pressures.

Numerical Analysis of Multi Layer Geosynthetic-Reinforced Granular Bed over Soft Fill

In this paper, considering the plain strain conditions, a numerical study has been conducted to investigate the behavior of multi layer geosynthetic-reinforced granular bed overlying a soft soil using the Fast Lagrangian Analysis of Continua (FLAC) program. The granular fill, soft soil, and geosynthetic reinforcements are considered as linear elastic materials. The geosynthetic reinforcements are modeled as cable elements fully bonded with the surrounding soil, thus neglecting any slip. The results obtained from the present investigation showed very close agreement when compared with the results of finite element analysis and lumped parameter modeling. The distribution of vertical, lateral and shear stresses in the soil are greatly affected as the number of reinforcement layers is increased. If the tensile stiffness of geosynthetic layers increases and its value is no more than 4,000–5,000 kN/m, the settlement of the reinforced foundation decreases significantly. The reduction in settlement is insignificant when the tensile strength of the geosynthetics exceed the above value.

Numerical studies of ring foundations on geogrid-reinforced sand

Numerical predictions of the ultimate bearing capacity of ring foundations supported by a sand bed with and without geogrid reinforcement are presented. Numerical analyses of the test models were carried out using the finite element package Plaxis. It is shown that the behaviour of ring foundations on sand beds may be reasonably well represented by the hardening soil model available in the Plaxis package. The hardening soil model parameters were derived from the results of drained triaxial tests. The parameters investigated are the effect of depth of first reinforcement layer, the number of reinforcement layers and reinforcement layer size on the ultimate bearing capacity of ring foundations. The results from the finite element analysis are in very good agreement with the experimental observations. The results of this study showed that the reinforcement had a considerable effect on the ultimate bearing capacity of the ring foundations. It was also shown that ultimate bearing capacity values can, depending on the reinforcement geogrid arrangement, be improved by up to three times that of the unreinforced case for the model arrangements investigated.

Laboratory Investigation of Behavior of Foundations on Geosynthetic-Reinforced Clayey Soil

The behavior of foundations on geosynthetic-reinforced clayey soil of low to medium plasticity using laboratory model footing tests was investigated. The model footing was made of a steel plate with dimensions of 152 mm (6 in.) × 152 mm (6 in.). The parameters investigated in this study included the top layer spacing, the number of reinforcement layers, the vertical spacing between layers, and the stiffness and type of reinforcement. The effect of reinforcement on the vertical stress distribution in the clay and the strain distribution along the reinforcement were also investigated. The test results showed that the inclusion of reinforcement could significantly improve the soil's bearing capacity and reduce the footing settlement. With three or more layers of reinforcement, the settlement could be reduced by approximately 50% at a relatively medium surface pressure. The geogrids with higher stiffness performed better than geogrids with lower stiffness. The test results also showed that the induced vertical stresses in clay under the center of footing could be appreciably reduced with the inclusion of reinforcement, which would result in reducing the consolidation settlement. Insignificant strain measured in the geogrid beyond its effective length of 6.0B (where B is the footing width) indicated that the geogrid beyond this length provided negligible reinforcement effect.

Experimental and numerical study of soil-reinforcement effects on the low-strain stiffness and bearing capacity of shallow foundations

This paper presents results of meticulous laboratory testing and numerical simulations on the effect of reinforcement on the low-strain stiffness and bearing capacity of shallow foundations on dry sand. The effect of the location and the number of reinforcement layers is studied in the laboratory, whereas numerical simulations are used to study the reinforcement-foundation interaction. Laboratory tests show an increase of 100, 200, and 275% not only in bearing capacity but also in low-strain stiffness (linear load–displacement behaviour) of a square foundation when one, two, and three layers of reinforcement are used, respectively. The specimen preparation technique is found to be crucial for the repeatability and reliability of the laboratory results (less than 5% variability). Numerical simulations demonstrate that if reinforcements are placed up to a depth of one footing width (B) below the foundation, better re-distribution of the load to deeper layers is achieved, thus reducing the stresses and strains underneath the foundation. Numerical simulations and experimental results clearly identify a critical zone between 0.3 and 0.5B, where maximum benefits not only on the bearing capacity but also on the low-strain stiffness of the foundation are obtained. Therefore, soil reinforcement can also be used to reduce low-strain vibrations of foundations.

Nonlinear analysis of multilayer extensible geosynthetic-reinforced granular bed on soft soil

The paper presents a model for the analysis of granular foundation beds reinforced with several geosynthetic layers. Such reinforced granular beds are often placed on soft soil strata for an efficient and economical transfer of superstructure load. The granular bed is modeled by the Pasternak shear layer and the geosynthetic reinforcement layers by stretched rough elastic membranes. The soft soil is represented by a series of nonlinear springs. The reinforcement has been considered to be extensible and it is assumed that the deformation at the interface of the reinforcements and soil are same. The nonlinear behavior of the granular bed and the soft soil is considered. Plane strain conditions are considered for the loading and reinforced foundation soil system. An iterative finite difference scheme is applied for obtaining the solution and results are presented in nondimensional form. The results from the proposed model are compared to the results obtained for multilayer inextensible geosynthetic reinforcement system. Significant reduction in the settlement has been observed when the number of reinforcement layer is increased. In case of inextensible reinforcements as the number of reinforcement layer is increased the settlement is decreased with a decreasing rate, but in case of extensible reinforcement the reduction rate is almost constant. Nonlinear behavior of the soft soil decreases as number of reinforcement layer is increased. The effect of the stiffness of the geosynthetic layer on the settlement response becomes insignificant for multilayer reinforced system, but the mobilized tension in the reinforcement layers increases as the stiffness of the geosynthetic layers increases.

A study of the deformation of flexible pipes buried under model reinforced sand

A series of model tests were conducted to investigate the effects of installing reinforcement layer above the pipe on the deformation characteristics of PVC pipes. The number of reinforcement layers, types of reinforcements, and burial depths of the pipe were varied in a number of tests. The test results showed a significant increase in bearing capacities when reinforcements were introduced, while the reduced settlement caused by improved bearing capacities with buried reinforcements had little effect on resistance against pipe deflection. When the burial depth of flexible pipe was shallower than the width of the loading area, the effectiveness of reinforcements in reducing pipe deflection increased as the load became larger.

Model studies of ring foundations on geogrid-reinforced sand

An experimental investigation into the ultimate bearing capacity of ring foundations supported by a sand bed with and without geogrid reinforcement is reported. The parameters investigated are optimum ring width, the effect of depth of first reinforcement, the number of reinforcement layers, and the effect of reinforcement layer length on the ultimate bearing capacity of ring foundations. The results of the experimental study proved that the reinforcement had a considerable effect on the ultimate bearing capacity of the ring foundations. It was also proved that ultimate bearing capacity values can, depending on the reinforcement geogrid arrangement, be improved by up to three times that of the unreinforced case. It was shown that a ring foundation with the optimum width showed similar performance to that of full circular foundation with the same outer diameter on the ring foundations for both the unreinforced and reinforced cases.

Model studies of ring foundations on geogrid-reinforced sand

An experimental investigation into the ultimate bearing capacity of ring foundations supported by a sand bed with and without geogrid reinforcement is reported. The parameters investigated are optimum ring width, the effect of depth of first reinforcement, the number of reinforcement layers, and the effect of reinforcement layer length on the ultimate bearing capacity of ring foundations. The results of the experimental study proved that the reinforcement had a considerable effect on the ultimate bearing capacity of the ring foundations. It was also proved that ultimate bearing capacity values can, depending on the reinforcement geogrid arrangement, be improved by up to three times that of the unreinforced case. It was shown that a ring foundation with the optimum width showed similar performance to that of full circular foundation with the same outer diameter on the ring foundations for both the unreinforced and reinforced cases.

Bearing Capacity of Rectangular Footings on Geogrid‐Reinforced Sand

A study was undertaken to investigate the bearing capacity of rectangular footings on geogrid‐reinforced sand by performing laboratory model tests as well as finite‐element analyses. The effects of the depth to the first layer of reinforcement, vertical spacing of reinforcement layers, number of reinforcement layers, and the size of reinforcement sheet on the bearing capacity were investigated. Both the experimental and analytical studies indicated that there was an optimum reinfprcement embedment depth at which the bearing capacity was the highest when single‐layer reinforcement was used. Also, there appeared to be an optimum reinforcement spacing for multi‐layer reinforced sand. The bearing capacity of reinforced sand was also found to increase with reinforcement layer number and reinforcement size when the reinforcement was placed within a certain effective zone. In addition, the analysis indicated that increasing reinforcement stiffness beyond a certain value would not bring about further increase in the bearing capacity.