Equivalent linear site response analysis of partially saturated sand layers

Ghayoomi, Majid; Mirshekari, Morteza

doi:10.1201/b17034-78

Cited by 6 publications

(7 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is a result of the presence of interparticle suction forces that change the effective stresses in soils (Khalili et al 2004) and, in turn, the mechanical response. Thus, soils with different degrees of saturation differ in stiffness, and this consequently results in different dynamic response, seismic compression, and pore-water pressure generation and dissipation in geotechnical systems (Ghayoomi et al 2013;Ghayoomi and Mirshekari 2014;Mirshekari and Ghayoomi 2017;Cary and Zapata 2016). Experimental difficulties, such as direct measurement and control of matric suction, have hindered the investigation of the dynamic behavior of unsaturated soils.…”

Section: Introductionmentioning

confidence: 99%

Cyclic Triaxial Test to Measure Strain-Dependent Shear Modulus of Unsaturated Sand

2017

View full text Add to dashboard Cite

Dynamic shear modulus plays an important role in the seismic assessment of geotechnical systems. Changes in the degree of water saturation influence dynamic soil properties because of the presence of matric suction. This paper describes the modification of a suctioncontrolled cyclic triaxial apparatus to investigate the strain-dependent shear modulus of unsaturated soils. Several strain-and stress-controlled cyclic triaxial tests were performed on a clean sand with various degrees of saturation. Suction in unsaturated sands increased the shear modulus in comparison with the ones in dry and saturated conditions for different shear strain levels, with a peak modulus in higher suction levels. Also, shear modulus decreased with an increase in the shear strain for specimens with similar matric suction. The normalized shear moduli of the unsaturated sand specimens followed a similar trend to the ones predicted by the available empirical shear modulus reduction functions but showed lower values. The modulus reduction ratios of unsaturated sands shifted up as a result of higher effective stress and suction-induced stiffness. These trends were consistent for both strain-and stress-controlled tests.

show abstract

Section: Introductionmentioning

confidence: 99%

Cyclic Triaxial Test to Measure Strain-Dependent Shear Modulus of Unsaturated Sand

2017

View full text Add to dashboard Cite

show abstract

“…This, in turn, yields to different soil dynamic properties including small-strain and strain-dependent shear modulus and damping [32][33][34][35][36][37][38][39][40][41][42][43]. As a result, seismic wave propagation mechanisms may vary in partially saturated soil layers [44] that would lead to a different seismic site response [30,[45][46][47][48][49]. Soils in either dry or fully saturated conditions have been believed to result in more conservative solutions because matric suction in unsaturated soils increases the ground stiffness.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, partial saturation has not been directly considered in the state-of-the-practice site response analysis. However, recent investigations on the site response in unsaturated soils showed that this assumption might not be always reasonable [47][48][49]. Further, the influence of the degree of saturation on seismic response analysis is often considered by incorporating the in-situ measured shear wave velocity of shallow unsaturated soil layers.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Ghayoomi and Mirshekari [48] and Mirshekari and Ghayoomi [49] numerically studied the seismic response of partially saturated sand and silt layers using site response software DeepSoil [24]. In the absence of any available numerical procedure to account for partial saturation, this influence was investigated by adjusting the soil unit weight and effective stress for any given degree of saturation.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Centrifuge tests to assess seismic site response of partially saturated sand layers

Mirshekari

Ghayoomi

2017

Soil Dynamics and Earthquake Engineering

View full text Add to dashboard Cite

Seismic response of unsaturated soil layers may differ from that of saturated or dry soil deposits. A set of centrifuge experiments was conducted to study the influence of partial saturation on seismic response of sand layers under scaled Northridge earthquake motion. Steady state infiltration was implemented to control and provide uniform degrees of saturation profiles in depth. The amplification of peak ground acceleration at the soil surface was inversely proportional to the degree of saturation, especially in low period range. The cumulative intensity amplification of the motion was also higher in unsaturated soils with higher suctions. The lateral deformation and surface settlement of partially saturated sand with higher stiffness were generally lower than that in dry soil. Although neglecting the effect of partial saturation in sand layers might be conservative with respect to seismic deformations, it may result in underestimating the surface design spectra.

show abstract

“…Although several studies have been conducted in this research area leading to the proposal of several empirical procedures, they have focused on soil layers in dry or water-saturated conditions [1][2][3][4]. However, recent studies have emphasized the importance of understanding the influence of partial saturation on the seismic response of soils [5][6][7][8]. Since soils near the ground surface are typically partially saturated, it is important to have an inclusive methodology to incorporate the degree of saturation in seismic analyses.…”

Section: Introductionmentioning

confidence: 99%

Procedure to Estimate the Seismic Settlement of Partially Saturated Soils

Ghayoomi

McCartney

2015

Indian Geotech J

View full text Add to dashboard Cite

The performance of near-surface geosystems during earthquake shaking depends on the free-field response of the soil layer and soil-structure interaction mechanisms. This paper presents a brief summary of the variables involved in considering the free-field response of partially saturated soil layers, and provides a step-by-step procedure to estimate the seismic settlement of a soil layer with a given initial relative density and degree of saturation. The procedure, which has been validated in a previous study using centrifuge physical model tests, was tabularized and presented in a flow chart. This methodology was followed to estimate the seismic settlement of different sand layers having different initial relative densities. It was observed that the degree of saturation has the greatest impact on loose soil layers, which also show the greatest amount of seismic settlement. However, partially saturated soil layers resulted in lower seismic settlement comparing with dry or saturated soil layers.

show abstract

Equivalent linear site response analysis of partially saturated sand layers

Cited by 6 publications

References 1 publication

Cyclic Triaxial Test to Measure Strain-Dependent Shear Modulus of Unsaturated Sand

Cyclic Triaxial Test to Measure Strain-Dependent Shear Modulus of Unsaturated Sand

Centrifuge tests to assess seismic site response of partially saturated sand layers

Procedure to Estimate the Seismic Settlement of Partially Saturated Soils

Contact Info

Product

Resources

About