The New Empirical Equation Describing Damping Phenomenon in Dynamically Loaded Subgrade Cohesive Soils

Abstract

The damping ratio (D) is one of the key soil parameters in geotechnical issues where the soil is subjected to dynamic loads, like machines foundation, city tram and subway traffic, and driving of sheet pile or precast pile. Each of the abovementioned geotechnical problems is connected with significant damping, so its effect should be included in the dynamical analysis. Therefore, this article focuses on the damping phenomenon in cohesive soils from the capital of Poland, which is described by damping ratio (D). In this research, a set of the damping tests by free vibration method in resonant column device were conducted, and the influence of four selected factors, i.e., shear strain (γ), effective stress (p’), plasticity index (PI), and void ratio (e) on damping ratio in wide strain range was investigated and discussed. Based on the laboratory tests, the shear strain has the most impacts on the damping ratio characteristics; the plasticity index and the effective stress also have a significant influence. Based on the performed analysis, the authors propose the empirical equations with two sets of variables, the first for low and medium cohesive soil (PI < 20%) and the second for very cohesive soils (PI > 20%).

Application of an Artificial Neural Network (ANN) Model to Determine the Value of the Damping Ratio (D) of Clay Soils

“…Later, from ten results of the parameter D, the average value was evaluated and used in the performed analysis. More details about materials and methods are presented in [29].…”

“…from 0 to 326 m. The equation proposed by Soból et al [29] was calibrated on the same soil samples as the ANN model. It should be noted, however, that the formula proposed there was different for soils with an IP < 20% and different for those with an IP > 20%.…”

“…Soból et al [29]: Each considered model in the literature was suitable only for the tested soils. The equation presented by Ishibashi and Zhang [36] was calibrated for cohesive soil with an IP below 50% and an effective stress below 1000 kPa.…”

“…It characterizes the behavior of soil subjected to dynamic loads, such as the foundations of machines, the traffic of city trams and subways, and the driving of precast pile or sheet pile. These geotechnical problems are associated with significant damping, so its impact has to be taken into account in the dynamic analysis [29]. Unfortunately, the damping ratio, although important, is not easy to determine either on the basis of empirical formulas or in laboratory tests.…”

A Computer-Aided Algorithm Combined with an Integrated Downhole Method to Improve Shear Wave Detection and Damping Ratio Assessment: Theory and Preliminary Results

“…It seems that these have a good relationship with the material properties and confining pressure. The regression laws formulated so far require the initial damping ratio, D min (at low strain), e.g., in the Masing model [46] and other authors [47][48][49][50][51]. Instead, Taboada et al [52] show that D min has a weak relation with the confining stress but a greater affinity with D max − D min through numerous sandy soil tests.…”