Análisis de la capacidad portante y la susceptibilidad a consolidación de un suelo fino en la Parroquia Borrero-Charasol, del Cantón Azogues

Abstract

In the southern sector of Ecuador, several types of soil have problems in the structures implanted on them, an example of this is fine soft soils. This kind of soil goes through volumetric changes due to the increase in the water content in its structure, generating settlements, in addition to a low bearing capacity, which could affect its functionality as a foundation floor. However, these properties may be hidden from the surface, due to the desiccation of the material where: the upper part of the soil can have a much more compact consistency than the deeper soil and therefore higher surface resistance. This phenomenon could confuse the designer, who could overestimate the capabilities of the foundations material that influences in the excavation and foundation depth. The fine soil located in the sector known as Pérez - Perazo in the Borrero-Charasol part of Azogues, is an example of soft fine soil with superficial desiccation, that is why the present work studies this material in detail, and thus warn about the presence and behavior of these types of materials. For this soil, the physical, mechanical, geophysical and consolidation properties are obtained up by choosing samples from the depth of 5 meters in 1-meter intervals, through laboratory and field tests such as humidity, granulometry using sieves, Atterberg limits, specific weight, specific gravity, simple compression, triaxial compression, vane test, multichannel analysis of surface wave, electrical tomography, one-dimensional consolidation and field settlements; through altered and unaltered samples. The results achieved, showed a very significant decrease in soil resistance depending of depth, in addition to variations in the values according to the tests performed, finding undrained shear strengths from the simple compression test of 0.064 to 0.186 kg/cm², from the triaxial test from 0.49 to 1.52 kg/cm², from vane test from 0.2 to 1.25 kg/cm² and for multichannel analysis of surface wave from 0.964 to 1.141 kg/cm²; most tests showed the highest soil resistance at 2 meters deep except for the multichannel analysis of surface wave. The permissible load capacity for the different foundation scenarios (type and depth of displacement) ranges from 12.00 to 1.10 and 9.47 to 0.92 kg/cm² for square and continuous foundation slabs respectively. The consolidation phenomenon is important for the tested soil; a soft soil will generate significant settlements that must be taken into consideration in the design of structures using these materials. The present work analyzes the behavior by consolidation of the soil, obtaining a compression index (Cc) between 0.136 and 0.257, the rebound index (Cs) varies from 0.003 to 0.018, the consolidation index (Cv) from 0.0001 to 0.0005 cm²/s and the secondary compression index (Cα) from 0.0025 to 0.0081 in the laboratory and contrasting them with values estimated by correlations. The field settlement measurement test results in a measured settlement of 75.9 mm at the end of the primary consolidation process and a measure total settlement of 54.0 mm in the 57 days of test duration. Subsequently, an evaluation is performed of David & Poulos's Simple Diffusion theory and Terzaghi's one-dimensional consolidation with the measurements recorded in the field, without getting a good fit of the field data towards the consolidation theories. The settlement analysis is carried out by modifying the combinations of geometry (L / B ratio), depth of shed (Df) and applied foundation load. Finally, conclusions and recommendations are issued for prevention and / or control of the problems identified in the soil.