# Integrated Geotechnical Analysis of Allophanic Volcanic Ash Soils: SDMT and Laboratory Perspectives
## 4 Discussion  
### In Situ Test Result  
* DMT Caupicho  
Comparing Caupicho with Mayanquer, Albuja, and Seismic Quito, we have on average Cu = 5-15 Kpa, and in lower percentages, Cu = 20-40 Kpa; \(\dot{\Phi}\) = 30-45\({}^{\circ}\); Ko\({}_{\text{2-13 m}}\) = 0.5-0.7, far from average. In addition, P4-SQ Ko\({}_{\text{1-11 m}}\) = 0.3-4; OCR\({}_{\text{1-2 m}}\) = 1-13 (overconsolidated), OCR\({}_{\text{2-4 m}}\) = 1-4, and OCR\({}_{\text{4-13 m}}\) = 1 (normally consolidated); on average, \(\dot{Y}\) = 13-16 KN/m\({}^{3}\), and in lower percentages, \(\dot{Y}\) = 16-21 KN/m\({}^{3}\) (Figure 16).  
Comparing the Marchetti ID values in Table 25, we found a higher percentage of clays and silts and a lower percentage of sands. For P4-SQ, 34.48% of the soil was peat.  
Figure 16: _Cont._  
As seen in Table 26, Caupicho has 40.35% vs. Mayanquer's 21.08% of MUD (silt or clay mixed with water).  
Table 27 shows a topographic difference of 22.92 between Caupicho3 and Mayanquer, which indicates that the soil deposits partially follow the original topography of the terrain.  
\begin{table}
\begin{tabular}{c c c} \hline
**Soil** & **Caupicho** & **Mayanquer** \\ \hline MUD & 40.35 & 21.08 \\ Clay & 20.09 & 22.17 \\ Silt & 23.60 & 45.59 \\ Sand & 15.96 & 11.15 \\ \hline Total (\%) & 100.00 & 100.00 \\ \hline \end{tabular}
\end{table}
Table 26: Marchetti classification—comparison of soil types between Caupicho and Mayanquer.  
Figure 16: Relation of Caupicho geotechnical parameters using the Marchetti dilatometer vs. Quito seismic zoning project (P4-SQ, P5-SQ) and Mayanquer (S1, S2, S3, S4), listed as: (**a**) material index (I\({}_{\text{D}}\))–depth; (**b**) cohesion of unconsolidated undrained soil (Cu)–depth; (**c**) angle of internal friction ( \(\up\)) in degrees–depth; (**d**) coefficient of lateral soil pressure (Ko)–depth; (**e**) relationship between preconsolidation pressure \(\sigma\)c and the present effective vertical pressure \(\sigma\)’o (OCR)–depth; and (**f**) specific weight of soil ( Y )–depth.  
\begin{table}
\begin{tabular}{c c c} \hline \multicolumn{3}{c}{**Topographic Height**} \\ \hline
**Study** & **Height z (m)** & **Az** \\ \hline Mayanquer & 2994.46 & 22.92 \\ Albaja & 2993.73 & 22.19 \\ Caupichol & 2986.39 & 14.85 \\ Caupicho2 & 2976.18 & 4.64 \\ Caupicho3 & 2971.54 & 0.00 \\ \hline \end{tabular}
\end{table}
Table 27: Topographic difference per study in meters above sea level.  
SDMT-Vs Caupicho  
Figure 17 shows the geographic location of the geophysical soundings. The information in Table 28 was obtained from nine shots per seismic line. The shot locations along the array were at \(-\)8.33 m (profile), 12.50 m, 29.17 m, 45.83 m, 62.5 m (center), 79.17 m, 95.83 m, 112.50 m, and 133.33 m (counter profile). Six hits were made at each position, resulting in 54 records per seismic line. Data processing was performed by the multichannel analysis of surface waves (MASW) method using the Geopsy software version 3.4.1 [44].  
To calculate Vs30, we used Formula (8):  
\[Vs_{30}=\frac{\sum di}{\sum\frac{di}{Vs_{i}}} \tag{8}\]  
In Table 29, we show the Vs values for Caupicho1 compared to the geophysical surveys T42, T44, and T46. It is observed that Caupicho1 has two strata of Vs: 74.30-82.00 m/s at depths of 1.50-6.50 m and 8.50-9.60 m, similar to the values obtained with CPTu in organic soil deposits [42]; two strata of Vs were observed: 330.25-353.50 m/s at depths of 6.50-8.5  
In summary, Caupicho has Vs10 = 107-120 m/s and Vs30 = 169 m/s, with point strata showing Vs = 74-82 m/s and Vs = 330-354 m/s.