Determination of Secant Moduli of Agbelouve Silty Sand Stabilized with Cement Used as a Roadway Layer in Togo

The soil stabilization use is necessary in the presence of lesser quality soils. This stabilization has the effect of modifying the soils properties, in particular the strain modulus. For road dimensioning using rational method, it is necessary to know secant modulus of the soil which is not often done in Togo. In this paper, it is determined the secant modulus at different ages of silty sand stabilized with cement at different rates. For this, specimen of silty sand stabilized with cement at rates of 2.5; 3.5 and 4.5% are subjected to the Modified Proctor test and measurement of compressive strength with strain measurement to estimate the modulus at 7, 28, 60 and 90 days of age. The results show that moduli increase with age and cement rate. From different correlations, we estimate the dimensioning modulus of Agbélouvé silty sand stabilized with cement. These estimated moduli allow saying that the cement rate studied are satisfactory from the modulus viewpoint. This study completes the information on Togolese materials needed for road dimensioning by rational methods.

Numerical Study on Scale Effect of Repetitive Plate-Loading Test

Repetitive plate-loading test is intended to identify the elastic modulus of a target structure subjected to dynamic loading; such tests are mainly applied to railway roadbeds. The repetitive plate-loading test uses the same equipment as the plate-loading test but different loading methods. The plate-loading test derives the subgrade reaction modulus (k30), while the repetitive plate-loading test derives the strain modulus (Ev2). The former considers the scale effect of the loading-plate size, whereas the latter does not, thereby reducing the reliability of the results. Therefore, numerical analysis was conducted to propose a scale effect that can applied to field tests. First, to verify the 50-mm loading plate, a previous study comparing the results of the 300-mm loading plate in a field test was simulated by a numerical analysis, and the results were compared and analyzed. Next, the strain modulus was investigated according to the loading-plate size under subgrade conditions. An equation to estimate the scale effect applicable to loading plates with diameters of less than 762 mm was derived. The relationship between the calculated strain and elastic moduli was additionally analyzed.

COMPONENTS OF MATHEMATICAL MODEL OF TEXTILE YARN EXTENSION TO A BREAK IN TECHNOLOGICAL PROCESSES

The idea that mathematical simulation of the process of textile yarn stretching which reveals new features of its destruction in technological processes is substantiated in the paper. Mathematical model should take into account textile yarn motion velocity in technological processes, acting external forces, and the reliable law of yarn strain under stretching. Secant moduli of cotton yarn strain were determined from experimental diagrams of cotton yarn stretching. A significant nonlinearity of the change in strain modulus depending on the strain value is shown. An account of this factor leads to physically nonlinear laws of cotton yarn strain. Therefore, as the basis of a mathematical model of the motion process, a physically developed nonlinear elastic-viscoplastic law of cotton yarn strain is proposed. The main properties of the proposed law and the methods for determining its support dependencies are discussed. An algorithm for using the law in a mathematical model of the process of yarn strain to a break is proposed.

MODULUS ELASTISITAS BERBAGAI JENIS MATERIAL

Tujuan penelitian ini adalah menentukan modulus young (modulus elastisitas) dari berbagai jenis kawat logam, yaitu kawat tembaga, kawat baja dan kawat besi. Modulus young menilai keelastisan dari sebuah material perbandingan antara tegangan tarik (stress) dan regangan (strain). Modulus elastis dari Kawat baja sebesar 200,45 x 109, pada grafik hubungan tegangan terhadap regangan menunjukkan bahwa batas elastis ada pada beban ≤ 2,5 kg, batas plastis ada pada beban 3 kg - 5,5 kg, selanjutnya beban ≥ 6 kg kawat akan putus. Kawat tembaga nilai modulus elastisnya sebesar 117,83 x 109, pada grafik menunjukkan batas elastis ada pada beban ≤ 1,0 kg, batas plastis ada pada beban 1,5 kg – 3,0 kg, selanjutnya beban ≥ 3,5 kg akan putus. Kawat besi nilai modulus elastisnya sebesar 178,29 x 109, dari grafik menunjukkan bahwa batas elastis ada pada beban ≤ 2,0 kg. Batas plastis ada pada beban 2,5 – 3,5 kg, pada beban ≥ 4 kg akan putus. Penggunaan material uji menggunakan material dengan kondisi yang baik dalam menghindari terjadinya perlakuan negatif sebelum material tersebut diuji laboratorium. Dalam mendapatkan hasil maksimal, sebaiknya menggunakan alat uji tarik material mikro, agar setiap perubahan yang terjadi pada material dapat terdeteksi dan menghasilkan data yang lebih akurat