# Effect of Micropiles on Clean Sand Liquefaction Risk Based on CPT and SPT
## 2 Material and Methods
### CPT-Based Simplifeid Liquefaction Assessment (Site I)
The average improvement rate of the q\({}_{\text{c1 NCs}}\) value in these soils was 28.5% and the highest rate of change was recorded as 84% for the clayy sand at depth of 18.5 m, BH-I-5. The higher improvement rate of q\({}_{\text{c1 NCs}}\) in clean sand (SP), compared to the soil containing silt and clay, was because of the higher porosity of the SP soil. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c} \hline \hline
**BH** & **Point** & **Depth** & **USCS** & \(\gamma\) & \(\sigma_{\
u 0}\) & \(\sigma_{\
u 0}^{{}^{\prime}}\) & \multicolumn{3}{c}{**Before** & **Grouting**} & \multicolumn{3}{c}{**After** & **Grouting**} \\
**\#** & **ID** & **(m)** & **USCS** & **(KN/m2)** & **FC \%** & **(KPa)** & **(KPa)** &  
CPT-based liquefaction potential analysis for site I was performed following the recommendations of [PERSON] 2006. The Juang method was developed based on a case history from the Chi-Chi earthquake in Taiwan. In the liquefaction assessment procedure of site I using the Juang method with [PERSON]'s criteria [48] was included. [PERSON] adjusted the effect of fines contents in the liquefaction assessment correlations based on the measured cone penetration resistance and sleeve friction values. The r\({}_{\text{d}}\) modifications following [PERSON] and [PERSON]'s relationship [49] were included in the calculations. The MSF was calculated using NCEER-97 recommendations. Other parameters and assumptions remained the same, as used for the Idriks CPT-based liquefaction method. Figure 5 illustrates the effect of fines contents on the liquefaction assessment procedure. Figure 4: Cone penetration resistance values before and after jet grouting using micropiles in soil profile containing (SP-SC, SP-SM, SC, and SM). Figure 3: Cone penetration resistance values before and after jet grouting using micropiles in soil profile containing only poorly graded sand. of using jet-grouted micropiles on enhancing the resistance of the soil against liquefaction based on the Juang and Eurocode 8 methods. In these methods, the base curve for evaluation of liquefaction triggering is developed for \(\sigma^{\prime}_{\text{v0}}=100\) Kpa and \(CRR_{M=7.5}\). This curve is used for the liquefaction triggering evaluation based on the CSR and \(\text{q}_{\text{c1 Ncs}}\) values. Figure 5a shows the liquefaction analysis of the existing soil, before the jet grouting. Figure 5b illustrates the liquefaction condition of the soil improved by grouting. After the soil remediation using micropiles, the number of blue points in the \"No Liquefaction\" area was increased by 36%. This improvement against the liquefaction risk sheds light on the significance of soil stabilization using micropiles in clean sands. In the third attempt, the CPT-based liquefaction assessment for site I was conducted in accordance with the Eurocode 8 specifications. Deposits of dense and medium dense sand in this site were categorized as type C subsoil in the analysis procedure. The fines contents' corrections referring to NCEER-97 recommendations were used in the calculation. Other parameters such as GWL (before and during the earthquake), \(\text{a}_{\text{max}}=0.35\) g, \(\text{r}_{\text{d}}\), and MSF coefficients remained the same, as mentioned in the analysis procedure by the Boulanger and Idriss 2014 method [31]]. The results of the liquefaction analysis prior to and after micropile installation are shown in Figure 5. The number of cases in the safe \"No Liquefaction\" region was increased from 4 cases (Figure 5c) to 13 cases (Figure 5d) after performing soil remediation by jet grouting.