## 4 Test Results  
### Tension Load Test and Elastic Characteristics  
Five micropiles installed using the gravitational grouting (denoted as \(Gr\)), 3 with the geotextile packer (\(Ge\)), and 5 with the rubber packer (\(Ru\)) were tested by the tension load tests (Figure 4). Note that the testing results vary due to the spatial variability of the ground; however, it can be said that similar trends were observed within the same method. The displacement linearly increased and decreased in general, regardless of the installation methods. [PERSON]'s analysis [28] indicated that all results are less than the ultimate settlement or bearing capacity within the given level of loads. Based on Figure 4, the results from the tension load tests were averaged within the same method for comparison, and presented in Figure 5. A higher pullout resistance was observed in an order of \(Ru\), \(Ge\), and \(Gr\). The \(\delta_{\text{t}}\) at \(P\) = 1600 kN showed 6.14 mm, 9.34 mm, and 12.26 mm for \(Ru\), \(Ge\), and \(Gr\), respectively. Figure 4: Results of tension load tests. (**a**) Micropiles installed using only gravitational grouting (\(Gr\)), (**b**) geotextile packer (\(Ge\)), and (**c**) rubber packer (\(Ru\)). Assuming the behavior is elastic, the pullout modulus of the load-displacement relationship was calculated dividing the applied load by the total displacement for each loading (\(M_{\text{loading}}\)) and unloading zone (\(M_{\text{unloading}}\)). The value of R\({}^{2}\) was found to be 0.98-0.99, and thus, it was confirmed that the given load is within the elastic zone. The values obtained values are summarized in Table 3. For the pullout modulus during the loading cycle, \(M_{\text{loading}}\) showed 280.5 kN/mm, 179.9 kN/mm, and 139.3 kN/mm for \(Ru\), \(Ge\), and \(Gr\), respectively. As the total displacement at \(P=1600\) kN was lower in an order of \(Ru\), \(Ge\), and \(Gr\), the calculated modulus was higher in an order of \(Ru\), \(Ge\), and \(Gr\). The \(M_{\text{unloading}}\), the pullout modulus during the unloading cycle, was 299.4 kN/mm, 215.9 kN/mm, and 157.8 kN/mm for \(Ru\), \(Ge\), and \(Gr\), respectively. The \(M_{\text{unloading}}\) showed a higher value than \(M_{\text{loading}}\) due to stress hardening. The order of \(M_{\text{unloading}}\) is same as the order of \(M_{\text{loading}}\). Assuming an elastic loading mechanism, the theoretical elastic modulus of the micropile was analyzed and summarized in Table 3 as well. A predicted elastic modulus (\(E_{\text{predicted}}\)) based on the properties of the reinforcing bar and the grout was calculated as 62 GPa ([\(A_{\text{g}}E_{\text{g}}+A_{\text{s}}E_{\text{s}}\)]/[\(A_{\text{g}}+A_{\text{s}}\)]). A measured elastic modulus (\(E_{\text{loading}}\) and \(E_{\text{unloading}}\)) was calculated using the applied load, area, and vertical strain (e.g., total displacement over micropile length, Table 3). The \(E_{\text{loading}}\) for \(Gr\) was 67.9 GPa, and this was sufficiently similar to \(E_{\text{predicted}}=62\) GPa. The \(E_{\text{loading}}\) for Ge (\(E_{\text{loading}(\text{Ge})}\)) gave the value of 87.7 GPa and this value is 41.5% higher than \(E_{\text{predicted}}\). The \(E_{\text{loading}(\text{Ge})}\) was equivalent to the micropile with \(D_{\text{rebar}}=100.3\) mm with \(D_{\text{hole}}=177\) mm. Given that the testing ground is fractured soft rock, it was concluded that the bonding stress between the grout and soils was effectively improved by the infiltration of the pressured footing through the fractures in accordance with previous research [17]. The \(E_{\text{loading}(\text{Ru})}\) was calculated as 136.8 GPa, which is 221% higher than \(E_{\text{predicted}}\). The value corresponds to \(D_{\text{rebar}}=147.6\) mm with \(D_{\text{hole}}=177\) mm. The \(E_{\text{loading}(\text{Ru})}=136.8\) GPa presented 56% higher than \(E_{\text{loading}(\text{Ge})}=87.7\) GPa. Therefore, it  
Figure 5: Comparison of pullout capacity of micropiles with different installation methods.