Geotechnical performance of waste tires for soil reinforcement from chamber tests

Bearing capacity and settlement of tire-reinforced sands

Reinforced soil is a composite material in which elements of high tensile resistance are implemented to increase the tensile resistance of the soil. Geotextiles are one of the major groups of geosynthetic products that are used for soil reinforcement. This paper deals with the effects of using nonwoven geotextile to improve the ultimate bearing capacity of footings resting on sand with medium density. The plate load tests were performed using 27 cm × 27 cm and 35 cm × 35 cm square plates, and the effects of the depth of the first layer of geotextile, vertical spacing as well as the number of geotextile layers on the ultimate bearing capacity of the footings were studied. Moreover, the impact of plate size and sample size was examined numerically by performing 3-D finite element analyses with different sizes of the square plate. The experimental results showed that the maximum bearing capacity is achieved for the system with four geotextile layers, vertical spacing of 0.3B between geotextile layers and geotextile width of 4B, where B is the width of the plate. The numerical analyses indicated that with increasing the size of the plate up to 65 cm, the values of the bearing capacity ratio (BCR) gradually decrease; however, additional increase in the size of the plate has a little impact on BCR values.

Experimental and Numerical Study of Bearing Capacity and Effect of Specimen Size on Uniform Sand with Medium Density, Reinforced with Nonwoven Geotextile

Stone column technique has been successfully applied for the foundation improvement. A rigid box with dimensions of 1.5 × 1.5 × 1.2 m equipped with a jacking-pump system was used to loading the stone column reinforced bed. Laboratory tests are carried out on stone columns with 6.3 cm diameter and different patterns surrounded by loose sand. The parameters varied in this experimental and numerical investigation are length, diameter and number of stone columns. The number of stone columns in these tests are 4, 5 and 9 and lengths of stone columns are 30, 40 and 50. A 40 × 40 × 2 cm steel plate is used as the model foundation. In these tests, the variation of bearing capacity ratio (BCR) and settlement reduction factor (SRF) are reported for different length and number of stone columns. The results show that by increasing the number and length of stone columns, BCR value will increase and SRF value will decrease. Finite-element analyses have also been performed using the ABAQUS software. The numerical results from the FEM were first validated with the experimental results and then some parametric analyses were conducted to investigate the effect of stone column diameter.

Physical and Numerical Modeling of Stone Column Behavior in Loose Sand

When designing structures that will impose a significant load over a large area, such as buildings, tanks, walls, slopes or embankments, geotechnical engineers must address the following situations, especially when dealing with weak foundation soils: bearing capacity failures, intolerable total and differential settlements, large lateral pressures and movement, and slope instability. The construction of reinforced soil foundations to support a shallow spread footing has considerable potential as a cost-effective alternative to conventional methods of foundation support. With this technique, more than one layer of geogrid reinforcement is placed within layers of engineering fill material under the footing to create a composite material with improved performance characteristics. Here an attempt is made to present the details of an investigation of the performance of geogrid reinforcement in soil. For this purpose, model isolated footing load tests were conducted on soil with and without multi-layers of geogrid at different depths below the footing. The load settlement characteristic for each soil-geogrid configuration was observed. The influence of various selected parameters on the load settlement behavior were studied and critically appraised for their practical significance. The paper discusses the mechanisms of this system using a large-scale model footing for a case studies in which geogrid-reinforced soil footing is used for a schools project in Saudi Arabia. That site has a very soft silty clay/clayey silt soil, and the large-scale plate loading test was tested according to the procedure of ASTM D1194. Also, the paper presents the successful application in the use of geogrid-reinforcement. The field observations proved that the geogrid-reinforced system creates an enhancement to the very soft/soft soils and minimizes the differential settlement. The geogrid-reinforced system is more economic and attractive and demonstrates superior performance compared with most other ground improvement techniques and is optimal for rapid construction and/or strict total and differential settlements of the structure and/or a thick and newly placed fill.

Vito A. Guido

Papers

Bearing Capacity and Settlement Characteristics of GEOWEB-Reinforced Earth Slabs