# Integrated Geotechnical Analysis of Allophanic Volcanic Ash Soils: SDMT and Laboratory Perspectives
## 5 Conclusions and Recommendations  
Structurally, to the east of the study area there is an anticlinal and geological fault parallel to the Machangara River. Petrographic analysis and X-ray diffraction show minerals corresponding to volcanic rocks, such as andesite-dacite, mainly from the volcanic emissions of Atacazo. The mineral crystals present well-defined and angular forms, suggesting a small degree of transport (volcanic ash). Electron micrographs show spongy aggregates with a rounded nodular appearance from the weathered volcanic ash (allophane). The Caupicho soil is an organic mineral sediment, with 57-70% siltyc much, non-peat, and fossil diatoms, indicating a lacustrine period.  
In Caupicho, we have an OH silt with organic content between 5 and 25%. The oedometric test gives us a compression index \(\mathrm{C}\)c = 2.21-3.71; swelling index \(\mathrm{C}\)s = 0.15-0.31; and consolidation coefficient \(\mathrm{C}\)v = 1.96-14.94 mm\({}^{2}\)/min for pressure loads of 50-800 KPa. The drained consolidated triaxial test presents an effective friction angle \(\mathrm{\Phi}^{\prime}\) = 26-30\({}^{\circ}\) and effective cohesion \(\mathrm{c}^{\prime}\) = 12-47 Kpa, with an axial deformation of 14%. The average soil permeability for effective stresses \(\mathrm{\sigma}^{\prime}\)= 0-50 KPa is \(\mathrm{K}\)v = 3 \(\times\) 10\({}^{-8}\) m/s (oedometer) and \(\mathrm{Kh}\) = 2 \(\times\) 10\({}^{-7}\) m/s (DMT). The seismic wave velocities obtained are \(\mathrm{V}\)s = 74-82 m/s with two strata of 2 m and 1 m thick, with \(\mathrm{V}\)s values of 330 and 354 m/s respectively (DMT).  
Figure 20: Relation of Caupicho with Fiavé peat, oedometric test [47].  
\begin{table}
\begin{tabular}{l c c c c} \hline  & \multicolumn{4}{c}{**Type of Test**} \\ \hline  & \multicolumn{2}{c}{**Unconsolidated**} & \multicolumn{2}{c}{**Consolidated Undrained**} & \multicolumn{2}{c}{**Consolidated Drained**} & \multicolumn{1}{c}{**Reference**} \\ \hline
**Soil** & **UU** & **CU** & **CD** & \\ \hline Clay & 0\({}^{\circ}\) if saturated & 3–20\({}^{\circ}\) & 20–42 & \" \\ Silty clay & 17–22 & & & [44] \\ Muddy & 20.8 & & & \" \\ Peat & & 27.8–31.7 * & [45] \\ Organic silt-Caupicho & & 25.5–30 ** & Current research \\ \hline \end{tabular}  
* * Axial strain 20%; ** axial strain 14.4%.  
\end{table}
Table 33: _Cont._The studies of Albuja, Penafiel, and Mayanquer statistically coincided with the available geotechnical parameters of the soil, except for P4-SQ (Seismic Quito), which presented 35% peat according to the DMT test (I\({}_{\text{D}}\)).  
Cracks in the masonry of houses and enclosures indicate differential settlement due to consolidation in silt-organic muds limited by sand strata. Low-quality soil, seismic tectonic conditions, and accelerated urbanization in Caupicho should encourage new geotechnical studies on soil-bearing capacity, soil dynamics, and consolidation settlements.  
E.F.S.: investigation, conceptualization, and methodology; J.A.-S.: conceptualization, review, and supervision; M.C.: laboratory. All authors have read and agreed to the published version of the manuscript.  
This study did not receive any external funding. [PERSON] financed 60% of the project. The PURE assumed the rest.  
Not Applicable.  
The analyzed data can be provided upon request.  
The authors would like to thank the Laboratory of Materials Strength, Soil Mechanics, Pavements, and Geotechnics, especially [PERSON] and [PERSON], and the staff of the Research Department of the Pontifical Catholic University of Ecuador (PUCE) for their support during the development of this research.  
The authors declare no conflicts of interest.