# Effect of Micropiles on Clean Sand Liquefaction Risk Based on CPT and SPT
## 2 Material and Methods
### SPT-Based Simplifeid Liquefaction Assessment (Site II)  
At site II, SPT, as one of the popular tools in soil liquefaction assessment, was used. The first simplified liquefaction correlation was developed based on the SPT results [31]. Similar to the CPT-based simplified analysis, CRR and CSR quantities and Equation (1) were used for the liquefaction assessment in site II, which mainly contains clean sand (SP) soils. A factor of safety of 1 was considered in the calculations. Empirical base curves to assess the soil liquefaction potential were developed based  
Figure 5: CPT-based liquefaction analysis of clean sand for \(\sigma^{\prime}_{\text{v0}}=100\) Kpa and \(CRR_{M=7.5}\), following [PERSON] 2006 recommendations: (**a**) Liquefaction evaluation before jet grouting, (**b**) liquefaction assessment after jet grouting by micropiles and based on the Eurocode 8 specifications, (**c**) liquefaction evaluation before jet grouting, (**d**) liquefaction evaluation after jet grouting using micropiles. on the SPT database of clean sands in the site II. The database includes the case histories of major earthquakes, with or without the liquefaction triggering. The database outcomes were adopted for the \(\sigma^{\prime}_{\
u 0}=1\) atm and moment magnitude M\({}_{\mathrm{W}}=7.5\) to be presented as a single base curve. The effects of fines contents and overburden stress were considered in the liquefaction analysis. In this regard, the available data of fine-grained soils were categorized and compared to the equivalent corrected SPT blow count values for the clean sand. The finalized base curve for the SPT-based liquefaction triggering analysis is presented as \((N_{1})_{60\mathrm{cs}}\) versus CSR\({}_{\sigma^{\prime}_{\
u 0-1}\mathrm{M}_{\mathrm{W}}=7.5}\). Table 2 shows the soil profile and SPT-based liquefaction risk results using the [PERSON] and Idriss 2014 method [31] before and after jet grouting by implementing micropiles. Revised MSF and FC quantities, based on the new SPT-based case histories by [PERSON] [50], were used in the liquefaction triggering analysis. The effect of the different depth values of soil layers was adjusted in the calculations using the r\({}_{\mathrm{d}}\) coefficient. Using the logging data of five boreholes (BH-II-1,5), the SPT values were measured in a single boring at the same location prior to and after the grouting. In Table 2, analyzing the as \((N_{1})_{60\mathrm{cs}}\), CRR, and FS parameters before and after using jet-grouted micropiles indicates improvement of soil strength against liquefaction. Figure 6 presents the effect of jet grouting on the improvement of the \((N_{1})_{60\mathrm{cs}}\) values in only SP clean sand layers. The \((N_{1})_{60\mathrm{cs}}\) values were measured at various depths based on the results from five drilled boreholes. The same depth values are related to different borehole numbers, as identified in the Table 2. The average rate of improvement for \((N_{1})_{60\mathrm{cs}}\) in the clean sand was 29%. The highest increase rate of the \((N_{1})_{60\mathrm{cs}}\) was reported as 45% at a 12 m depth belonging to the borehole BH-II-3. Figure 7 indicates the \((N_{1})_{60\mathrm{cs}}\) measurements before and after soil remediation by micropiles in SP-SC, SP-SM, SC, and SM soil layers. The \((N_{1})_{60\mathrm{cs}}\) value for these soils increased with an average rate of 23%, and the maximum rate of change was measured as 36% for the SC soil at a depth of 7.5 m, BH-II-5. The slightly higher improvement rate of \((N_{1})_{60\mathrm{cs}}\) in clean sand (SP), compared to the soil containing silt and clay, was due to the higher porosity of the SP soil. Figure 6: Corrected SPT values before and after jet grouting using micropiles in the soil profile containing only poorly graded sand. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{ \begin{tabular}{c} **BH** \\ **\#** \\ **\#** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Point** \\ **ID** \\ **(m)** \\ \end{tabular}  } & \multirow{2}{*}{