**3.1 Interpretive structural model of seismic soil liquefaction significant factors**

In the ISM technique, a first endeavor is made to ascertain the significant seismic of soil liquefaction factors from the literature using systematic literature review (SLR) approach which is recommended by Okoli and Schabram [5]. The SLR is a systematic, explicit, and reproducible method for identifying, evaluating, and synthesizing the existing body of completed and recorded work published by researchers, scholars, and practitioners [12].

There are three groups of parameters that govern the soil liquefaction phenomenon, according to published research papers, namely seismic parameters, site conditions, and soil parameters [13–18]. Each of these contains a wide range of factors that characterize liquefaction, to a varying degree of significance. The details of these parameters are given below.

meaningful guiding significance for the subsequent prediction of seismic liquefaction potential. Furthermore Ahmad et al. [18] concluded that cone tip resistance (*qc*) has a considerable influence on liquefaction triggering. Furthermore, Ahmad et al. [28] used the equivalent clean sand penetration resistance (*qc*1*Ncs*) to decrease uncertainty and has found the strongest influence on liquefaction potential.

It is widely known that the increase in the vertical effective stress increases the bearing capacity and shear strength of soil, and consequently increases the shear stress required to cause liquefaction and decreases the potential for liquefaction. Many researchers have reported that saturated sands deeper than 15 to 18 m are not probably to liquefy [29]. These depths are in general agreement to Kishada [30], who states that a saturated sandy soil is not liquefiable if the value of the vertical

pressure the occurrence of liquefaction decreases [31, 32]. Tesfamariam and Liu [20] considered the Stark and Olson [21] earthquake liquefaction datasets and, intuited that, with a decrease in vertical effective stress, the likelihood of soil liquefaction increases. As vertical effective stress is conditioned on total vertical stress therefore accordingly, total and vertical effective stresses are included in the

In order to induce extensive damage at ground surface level due to liquefaction, the liquefied soil layer must be sufficient thick thereby resulting uplift pressure and amount of water expelled from the liquefied layer can result in ground damage such as sand boiling and fissuring (Ishihara [26]; Dobry [33]). If the liquefied sand layer is thin and deposited within the soil profile, the presence of a non-liquefiable surface layer may prevent the effects of the at-depth liquefaction from reaching the surface. Ishihara [26] established a standard that specifies a threshold value for the thickness of a non-liquefiable surface layer to avoid ground damage due to liquefaction.

It was intuited in the survey report prepared by Japan society of Civil Engineers that the big-sized earthquake liquefied the sand layer when the thickness is more than 3.0 m. When the thickness of the liquefied layer is very thin, the presence of a non-liquefiable surface layer may prevent the effects of the in-depth liquefaction

The resistance of soil to liquefaction is weakened as groundwater levels rise. The effect on soil liquefaction potential increases as groundwater levels rise above 2 m [34]. The water table regime must be minimized as one of the design criteria against seismic soil liquefaction [35]. The vertical effective stress is closely related to the depth of soil deposit. The vertical effective stress increases as the depth of the soil deposit increases. Increased vertical stress has been shown to improve the soil's bearing capacity and shear strength, reducing the risk of liquefaction. Even liquefaction from very loose sand is almost impossible for over 15 m of overburden, according to Florin and Ivanov [36], and Satyam [37] concluded the same for the preliminary

assessment of the soil liquefaction potential in a seismically active region.

the soil liquefaction factors retrieved from the literature were important for

The significant factors of seismic soil liquefaction that are identified through

expanding exploratory research by developing structural self-interaction matrix for interpretive structural modeling. The set of liquefaction factors identified in **Table 2** for seismic soil liquefaction potential was used to develop the model which represented the correlation between eleven seismic soil liquefaction factors. In the ISM model, for the development of the structural self-interaction matrix (SSIM),

Field experts' examined and analyzed the preliminary list and they believed that

. It is reported that an increase in the overburden

*3.1.3 Site condition*

effective stress exceeds 190 kN/m<sup>2</sup>

*Elucidation of Seismic Soil Liquefaction Significant Factors*

*DOI: http://dx.doi.org/10.5772/intechopen.97278*

proposed model as governing factors.

from reaching the surface.

SLR approach are presented in **Table 2**.

**167**

### *3.1.1 Seismic parameter*

The vulnerability of any cohesionless soil to liquefaction during an earthquake depends on the magnitude and number of cycles of stresses or strains caused by the seismic excitation. These in turn are correlated to the intensity, duration of ground shaking and predominant frequency. The degree of soil liquefaction varies with the different earthquake magnitude. Based on on-site observations and a simple parametric study, Green and Bommer [19] have concluded that a small earthquake with a moment magnitude of 4.5 will trigger liquefaction in highly susceptible soil deposits. However, for soil profiles suitable for building structures, the minimum earthquake magnitude is about 5 that cause liquefaction. Tesfamariam and Liu [20] considered the Stark and Olson [21] earthquake liquefaction datasets and intuited that with increase in *M* and *a*max, the likelihood of liquefaction increases. Peak ground acceleration (PGA) is a function of earthquake magnitude, site to fault distance, fault type and soil type as per Boore et al. [22] and usually used to quantify the ground motion intensity.

Pirhadi et al. [14] used closest distance to rupture surface which is among the other seismic parameters such as earthquake magnitude and peak ground acceleration as an influence factor and concluded that among the seismic parameters earthquake magnitude, peak ground acceleration and closest distance to rupture surface illustrate lesser effects on liquefaction triggering as compared to the cumulative absolute velocity. It is generally agreed, that earthquake magnitude, peak ground acceleration, and closest distance to rupture surface are the three major factors that affect the seismic intensity at the site.

#### *3.1.2 Soil parameter*

Liquefaction is usually observed in shallow, loose, saturated cohesionless soils subjected to strong ground motions. In case of in-situ cone penetration test, soil behavior type index is used to classify soils based on fines content presented by Robertson and Wride [23]. The liquefaction susceptibility depends on soil type, where fine-size particles are easier to liquefaction than coarse particles.

The type of soil that is more prone to liquefaction is one in which deformation resistance is mobilized by particle friction. When other factors like grain shape, uniformity coefficient, and relative density are held constant, the frictional resistance of cohesion less soils decreases as grain size decreases. Gravelly soils mobilize more strength during shearing and dissipate excess pore pressures more quickly than sandy soils. There are some case histories [24–26] that show liquefaction in loose gravelly soils during severe ground shaking or when the gravel layer is confined by an impervious layer.

The strength of soil liquefaction may vary depending on the fines content. Several studies have found that fines content has a significant impact on soil susceptibility to liquefaction [24–26]. Soil liquefaction potential increases as fines content exceeds 30%. When fines content exceeds 50%, however, the soil's liquefaction potential is reduced [27].

Zhou et al. [27] concluded that the cone tip resistance (*qc*) factor is sensitive among the predictor variables in CPT in-situ test method, which provides

meaningful guiding significance for the subsequent prediction of seismic liquefaction potential. Furthermore Ahmad et al. [18] concluded that cone tip resistance (*qc*) has a considerable influence on liquefaction triggering. Furthermore, Ahmad et al. [28] used the equivalent clean sand penetration resistance (*qc*1*Ncs*) to decrease uncertainty and has found the strongest influence on liquefaction potential.
