## 3 Results and Discussions
### Soil Reinforcement Tests
#### 3.2.3 Stress-Strain Curves  
Figure 7 presents the stress-strain curves obtained from the UCS tests on samples treated by different methods. For comparison, the stress-strain curve of untreated soil was also displayed in Figure 7. The stress-strain curve of the untreated soil displayed a response characterized by linear elastic behavior followed by a slow decrease in strength after peak strength, showing plastic failure characteristics. After solidification by both EICP and the improved EICP with organic  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Treatment Number** & **Treatment Method** & **Mean UCS (kPa)** & \
\begin{tabular}{c} **Rate Higher Than** \\ **Untreated Soil (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Rate Higher Than** \\ **EICP-Treated Soil (\%)** \\ \end{tabular} \\ \hline D1 & Untreated & 324.76 & - & - \\ D2 & Skim milk powder & 442.18 & 36.16 & - \\ D3 & Glutinous rice powder & 345.07 & 6.25 & - \\ D4 & Brown sugar & 494.22 & 52.18 & - \\ D5 & EICP & 1167.23 & 259.41 & - \\ A4 & EICP + skim milk powder & 1547.95 & 376.64 & 32.62 \\ B4 & EICP + glutinous rice powder & 1464.52 & 350.95 & 25.47 \\ C5 & EICP + brown sugar & 1455.41 & 348.15 & 24.69 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Mean UCS and the strength increasing rate of the proposed methods.  
Figure 6: Unconfined compression strength for soil treated by different methods.  
material added, the stress-strain curves can be roughly divided into three stages. In the first stage, the stress increased rapidly with the strain in a linear relationship, indicating that the pores of the samples were gradually compacted. In the second stage, the stress increased slowly with the strain and the relationship curved downward in a convex manner until the stress reached a maximum. In the third stage, the stress decreased sharply with the strain after reaching peak strength. In addition, the stress-strain curves of soil reinforced only by one kind of organic material also underwent three stages: a linear increasing stage, a slow decreasing stage, and a rapid declining stage. Basically none of the reinforced specimens maintained a certain residual strength after failure, which is a typical brittle failure [47].  
Some stress and strain parameters acquired from the UCS tests were calculated and are listed in Table 5. The compressive elastic modulus of EICP-treated soil with organic material added was nearly 30-53% higher than that without organic material and was five-fold higher than that of untreated soil. The failure strain and peak strain for soil treated by the improved EICP was 60-80% of that for untreated soil. Compared with untreated soil, both the failure strain and peak strain for soil treated only by organic material showed little change. The peak strength of the soil reinforced by the improved EICP with skim milk powder at the optimum concentration was the largest, with brittle failure characteristics being the most significant, followed by glutinous rice powder and brown sugar at their optimum concentrations. The greater the increase in the compressive strength was, the more significant the characteristics of brittle failure.