The influence of pressure as a form of confinement on various geotechnical properties of silt layers in different locations was the main focus of this study. Confinement levels between 11 and 225 kilopascals (kPa) were evaluated to determine changes in resonance frequency, shear velocity, and maximum shear modulus (Gmax). The observations are presented and discussed in detail here. The results showed a direct relationship between confinement and resonance frequency. Greater confinement resulted in a considerable drop in the natural frequency of vibration in the silt layers. This occurs due to the increased stiffness of the soil matrix caused by the applied pressure, which inhibits free particle movement and, thus, affects the vibrational behavior. Additionally, our findings point to an increase in shear velocity as a result of confinement. The generated pressure enhances contact forces among particles in the silt layer, making the soil stiffer and, consequently, facilitating the transmission of shear waves, leading to higher shear velocities. Lastly, the maximum shear modulus (Gmax) tends to increase under higher confinement levels. This indicates that pressure promotes the establishment of stronger inter-particle bonds, and a denser soil structure, resulting in greater resistance to shear deformation. In summary, our research shows the considerable effect of confinement on the resonance frequency, shear velocity, and Gmax of silt layers. Decreased resonance frequency and increased shear velocity and maximum shear modulus illustrate the crucial role of pressure in modifying the dynamic and mechanical properties of the soil. Such knowledge is essential for geotechnical engineering and construction purposes.
Further studies should be conducted to analyze the long-term effects of confinement and investigate the possible ramifications of these outcomes on the design and reliability of structures constructed on silt layers.
The increase in confinement pressures of the silt soil at Sites A, B, and C presented in Fig. 1 has revealed striking variations in the frequency response of the soil. A gradual rise in the frequency response was recorded as the confinement in the sandy soil layers grew, highlighting a direct correlation between soil confinement and frequency response. As the confinement pressures intensified, Site A registered a frequency response that ranged from 41.13 Hz to 61.5 Hz while Site B between 41.45 Hz and 63.44 Hz, and Site C between 44.74 Hz and 67.21 Hz. Comparing the varying sites, Site C had the highest frequency response, followed by Site B, with Site A showing the least. This disparity suggests the soil at Site C being far stiffer in comparison to that of Sites A and B. The stiffness of soil plays a prominent role in its liquefaction potential, and the higher frequency response at Site C denotes a lesser possibility. This notion aligns with the notion that higher frequency corresponds to stiffer soil. As the soil confinement pressures boosted, the stiffness of the soil at all three sites augmented; consequently, the susceptibility to liquefaction reduced. In conclusion, the increase in soil confinement pressure at Sites A, B, and C is paralleled by a relative rise in frequency response, demonstrating the direct connection between the two factors. Site C showed the highest frequency response - revealing a stiffer soil and decreased risk of liquefaction - whereas Site A held the lowest response, characterizing a more pliable soil with a higher risk of liquefaction. This study underlines the impact of increased soil confinement pressure on soil stiffness and its consequential effect on liquefaction potential.
Figure 2 shows the increasing shear wave velocity (Vs) in the sandy soil layer as confinement level rises highlights how important this parameter is for assessing the soil's dynamic characteristics and behavior, including its resistance to liquefaction and susceptibility when used for structural foundation designs. When the confinement is deepened, the velocity steadily increases, showing that these soils are compact and hard, according to the data. Increased confinements have caused a large rise in shear wave velocity, which is evidence of denser, more compact soil with higher stiffness and deformation resistance. It is clear that confinement has a significant impact on the characteristics of the soil since the shear wave velocity recorded at Site A ranges from a low of 59.31 m/s at 11 kPa to a high of 180.97 m/s at 225 kPa. This illustrates how richer soil and higher shear wave velocities might result from greater constraint exertions. Similar patterns can be seen at Sites B and C, where the velocities range from a low of 44.32 m/s at an 11 kPa confinement to a high of 175.15 m/s and from a minimum of 50.68 m/s to a maximum of 171.43 m/s, respectively. This suggests that greater confinement directly and proportionately increases the density, stiffness, and deformation resistance of the soil. Figure 2's information highlights the remarkable influence confinement may have on the soil's dynamic qualities. The premise that denser soil composition might result in superior resistance to deformation and optimal comprehension of geotechnical assessments and structured foundation designs is concretely attested to by the increased velocity caused by higher confinements.
The analyzed soils in this study exhibited similar shear wave velocities which allowed them to be classified according to the National Earthquake Hazards Reduction Program (NEHRP) soil classification scheme. These values were found to follow consistent trends among the tested sites, demonstrating a cohesive mixture of Class C and Class D soils. It is vital to note that the range of these velocities offers one with valuable insights. These soils appear to have a high stiffness that would allow them to withstand significant dynamic loading. In addition to this, these soils possess a decreased risk of soil liquefaction when exposed to seismic or loading forces. Factors such as these make the soils desirable for a range of civil engineering projects. The data collected in this study provides insight into the favorable features of the tested soils. These characteristics are conducive to the construction of civil structures, allowing for improved safety and reliability when it comes to dynamic forces and pressure. Altogether, the findings assist in better understanding soil properties and informs decision-making processes in the domain of geotechnical engineering.
A detailed overview of the maximum shear modulus (Gmax) that a sandy soil layer may express at various confinement levels is shown in Fig. 3. In terms of quantity, the maximum shear modulus appears to rise with increased confinement, indicating that the soil is more resistant to shear pressures. When larger confinement pressures were used, shear modulus values at Sites A and B significantly increased, going from 6.73 MPa to 59.11 MPa and 5.54 MPa to 55.44 MPa, respectively. The similar phenomena were seen at Site C, where the shear modulus varied depending on confinement pressures from 5.13 MPa to 54.12 MPa. These findings suggest that the sand soil layer's resistance to shear stress is enhanced by increased confinement pressures.
On the other hand, because of the soil's increased susceptibility to deformation, a decrease in the shear modulus at lower confinement pressures signifies a poorer capacity for lateral support. In order to increase the strength of the soil and its resistance to shear pressures under low confinement settings, extra actions should be performed in addition to the deployment of appropriate ground development techniques. Results from Fig. 3 generally shed light on the relationship between confinement pressures, maximum shear modulus, and the dynamic behavior of sandy soil layers. The behavior of the soil layer changes when confinement forces are increased, going from a state of increased susceptibility to one of increased strength and resistance. under order to avoid possible damages and improve foundation performance under unfavorable conditions, essential measures must be performed.