Temel Yetimoglu

A study on shear strength of sands reinforced with randomly distributed discrete fibers

Abstract A study was undertaken to investigate the shear strength of sands reinforced with randomly distributed discrete fibers by carrying out direct shear tests. The effect of the fiber reinforcement content on the shear strength was investigated. The results of the tests indicated that peak shear strength and initial stiffness of the sand were not affected significantly by the fiber reinforcement. The horizontal displacements at failure were also found comparable for reinforced and unreinforced sands under the same vertical normal stress. Fiber reinforcements, however, could reduce soil brittleness providing smaller loss of post-peak strength. Thus, there appeared to be an increase in residual shear strength angle of the sand by adding fiber reinforcements.

Hydraulic conductivity of compacted clay liners permeated with inorganic salt solutions

Due to their low permeability, geosynthetic clay liners (GCLs) and compacted clay liners (CCLs) are the main materials used in waste disposal landfills. The hydraulic conductivity of GCLs and CCLs is closely related to the chemistry of the permeant fluid. In this study, the effect on the hydraulic conductivity of clays of five different inorganic salt solutions as permeant fluid was experimentally investigated. For this purpose, NaCl, NH4Cl, KCl, CaCl2, and FeCl 3 inorganic salt solutions were used at concentrations of 0.01, 0.10, 0.25, 0.50, 0.75 and 1 M. Laboratory hydraulic conductivity tests were conducted on low plasticity (CL) and high plasticity (CH) compacted raw clays. The change in electrical conductivity and pH values of the clay samples with inorganic salt solutions were also determined. The experimental test results indicated that the effect of inorganic salt solutions on CL clay was different from that on CH clay. The hydraulic conductivity was found to increase for CH clay when the salt concentrations increased whereas when the salt concentrations were increased, the hydraulic conductivity decreased for the CL clay.

Strength Behavior of Fine Grained Soil Reinforced with Randomly Distributed Polypropylene Fibers

Admixtures and reinforcement materials are frequently used in practice to stabilize coarse and fine grained soils and to improve their engineering properties. However, a limited number of studies have been carried out on fiber-reinforced fine grained soils. In this study, a series of unconfined compression tests, direct shear tests, and California Bearing Ratio tests were carried out to investigate the effect of randomly distributed polypropylene fiber on the strength behavior of a fine grained soil. The content of polypropylene fiber was varied between 0.25 and 1% by total dry weight of the reinforced samples. It was observed that unconfined compression strength, cohesion intercept and California Bearing Ratio increased with the addition of fibers. On the other hand, the results of the tests indicated that shear strength angle was not affected significantly by the fiber reinforcement.

Comparison of Measured and Theoretical Pressure Distribution below Strip Footings on Sand Soil

AbstractThe paper presents vertical pressure values occurring under the center line of uniformly loaded laboratory model tests of a surface strip footing on a sand bed. The vertical pressure distribution in medium dense sand was measured using miniature pressure sensors. The experimental measures obtained from the model test program have been compared with values obtained from earlier theories. Tests were performed in plane strain conditions. Finally, the results obtained from experiments and theoretically obtained values were discussed. The results indicated that the distribution of pressure was not the same for every load level. It was found that the pressure distributions fit Westergaard distribution better at lower loads. They approach the pressure predicted by an earlier study as the applied loads reach bearing capacity values.

Simple design models for bearing ratio of sand reinforced using different geosynthetics

To develop relatively simple equations for design of a reinforced pavement design model, tests were conducted. Firstly, the effects of vertical spacing of reinforcement layers and depth of the reinforced zone were investigated by using different types of geosynthetic materials. The number of the reinforcement layers was also varied to see how these material parameters influenced the results. The comprehensive results from laboratory model tests supported on a woven geotextile and different geogrids were presented. The results were compared to each other. Based on model tests, different reinforcement types showed different behaviors for different numbers of reinforcement layers and different vertical spacing of the reinforcement layers. Additionally, it was seen that the improvement obtained by reinforcing the subgrade is different for low settlement ratio values and large settlement values for different vertical spacing values. Then, new simple estimation formulas were determined for bearing ratio by regression analyses for different types of reinforcement materials.