Effect of soil permeability on soil–structure and structure–soil–structure interaction of low-rise structures

Abstract

Earthquake-induced soil liquefaction can generate excessive damage to building structures due to significant reduction in soil effective stress. With increasing urbanisation and population growth, the performance of closely-spaced buildings, such as those in towns and cities, is of greater concern where structure-soil-structure-interaction (SSSI) may occur in conjunction with full or partial liquefaction.This study investigates the seismic performance of isolated and adjacent structures built on shallow foundations on soils of different permeability (i.e. with different amounts of drainage and therefore generating different amounts of excess pore water pressure) using a combination of dynamic centrifuge modelling and Finite Element Modelling (FEM). The results demonstrate that the reduction in free-field ground surface intensity measure (specifically, Housner Intensity) due to increasing liquefaction can be correlated to an index which is the normalised integral of excess pore pressure ratio (ru) with depth. This index can express the amount of liquefaction uniquely even when full liquefaction occurs to only partial depth, or where excess pore water pressures are increased but below the level of full liquefaction at all depths. This underlying correlation means that structural demand reduction (e.g. reduction in interstorey drift ratio) with liquefaction (SSI effect) can be linked to either (i) the r u -depth index, (ii) the depth of the liquefaction front, that can be estimated from a liquefaction triggering analysis; or (iii) the Qi, S & Knappett, JA 2021, 'Effect of soil permeability on soil-structure and structure-soil-structure interaction of lowrise structures', Geotechnique, pp. 1-16. https://doi.org/10.1680/jgeot.20.P.109 ground surface intensity amplification/attenuation in the free-field from the results of 1D free field soil column analyses. Where there are adjacent structures, a strongly beneficial SSSI effect on co-seismic settlement and detrimental effect on drift in non-liquefied soil, as observed in this and previous studies, reduced towards a null-effect in both cases with increased liquefaction, with liquefaction appearing to isolate the structures from each other (at least for the configuration considered herein). This has also been linked to the amount of amplification/attenuation of surface ground motion in the free-field (or amount of liquefaction) as a simple indicator of the likely importance of SSSI effects in liquefiable soil.

Slope topographic effects on the nonlinear seismic behavior of groups of similar buildings

“…Buildings in the city blocks are usually built in the 3D rectangular (or square) plan shapes; however, in most studies on the effects of SSSI, 2D arrangement of structures (3D or 2D modeling approach for building groups of 1×n) is considered 28,31,33,36,88–90 . Arrangement of adjacent structures in the 3D multibuilding SSSI is one of the important factors that can influence the seismic performance of buildings compared with the 2D arrangement of buildings 12,26,30,91 .…”

“…in the city blocks are usually built in the 3D rectangular (or square) plan shapes; however, in most studies on the effects of SSSI, 2D arrangement of structures (3D or 2D modeling approach for building groups of 1×n) is considered. 28,31,33,36,[88][89][90] Arrangement of adjacent structures in the 3D multibuilding SSSI is one of the important factors that can influence the seismic performance of buildings compared with the 2D arrangement of buildings. 12,26,30,91 In order to investigate the 2D and 3D effects of SSSI, in this study, the 1×2 (see Figure 3D without the 3 rd building) and 2×2 (Figure 4D) groups of adjacent buildings were modeled, respectively, through the 3D nonlinear finite element SSSI and TSSSI analysis.…”

Numerical Simulations of the Seismic Response of a RC Structure Resting on Liquefiable Soil

“…Evidence from past earthquakes has demonstrated the devastating effect of soil liquefaction on the seismic response of buildings. Thus, the response of buildings resting on liquefiable ground and subjected to earthquake effects has received considerable attention in the literature in order to produce better insights into the potential seismic response of buildings and hence to enhance design procedures [1][2][3][4][5][6][7][8][9][10][11]. A summary of information from previous studies is listed in Table 1.…”

“…Forcellini [10] conducted 3D finite element analyses to evaluate the response of a building resting on potentially liquefiable ground by changing the height and weight of the building. Qi and Knappett [11] studied the influence of soil permeability on the performance of isolated and adjacent buildings using centrifuge modelling. Low (1.35 × 10 −4 m/s) and high permeability (5.40 × 10 −3 m/s) were considered in the investigations.…”

Structure–soil–structure interaction (SSSI) of adjacent buildings with shallow foundations on liquefiable soil

“…In most real-life cases, the assumption of a single, isolated foundation is unrealistic and potentially un-conservative. Indeed, the very few centrifuge studies that have examined two adjacent foundations at different distances from each other, [28][29][30][31][32] all conclude that ignoring SSSI is un-conservative. For structures sufficiently close to each other, a trend of increased outwards rotation was observed by Hayden et al, 29 similarly to the well-documented case history of the Teverler buildings in Adapazari (Bray et al 2000, Figure 1A).…”