María de la Luz Pérez-Rea

Use of Effective Stresses to Model the Collapse upon Wetting in Unsaturated Soils

AbstractThis paper presents the modeling of the phenomenon of collapse upon wetting using the effective stress approach. To this purpose, Bishop’s effective stress equation is applied in addition to an elastoplastic framework for the volumetric behavior of unsaturated soils. Bishop’s parameter χ is obtained from a porous-solid model that is able to simulate the soil-water retention curves during wetting-drying cycles. The proposed framework includes the hysteresis of the retention curve and to some extent the hydro-mechanical coupling of unsaturated soils. This model is able to reproduce quite precisely the phenomenon of collapse upon wetting using a single valued compressibility index. It also represents a unifying framework for saturated and unsaturated soils.

Impact of diesel contamination on the compressibility of a clayey soil

Every day petrochemical activities, spills, and leaks in the storage pipes contaminate the soil. For example, if a spill occurs or there is a leak of a pipe near where there is a building, the mechanical properties of the soil can be affected, causing economic problems or, in extreme cases, loss of life due to lack of stability in the structure. It is possible to take decisions if we know the behavior of the soil in contact with some contaminant. In Mexico, some works have been initiated that evaluate the physical and mechanical properties of the soil contaminated; however, this information cannot be generalized because each place has various soil formations. In this work, we present a study of a high compressibility clayey soil (CH) contaminated with diesel to evaluate its impact on the limits of consistency and the compressibility index of the soil. We found that the liquid limit decreased when the soil was contaminated with diesel. The results showed that in the consolidation process in the contaminated soil a decrease in the compressibility index of 19% compared to the soil with water.

Geostatistical characterization of the soil of Aguascalientes, México, by using spatial estimation techniques

Four spatial estimation techniques available in commercial computational packages are evaluated and compared, namely: regularized splines interpolation, tension splines interpolation, inverse distance weighted interpolation, and ordinary Kriging estimation, in order to establish the best representation for the shallow stratigraphic configuration in the city of Aguascalientes, in Central Mexico. Data from 478 sample points along with the software ArcGIS (Environmental Systems Research Institute, Inc. (ESRI), ArcGIS, ver. 9.3, Redlands, California 2008) to calculate the spatial estimates. Each technique was evaluated based on the root mean square error, calculated from a validation between the generated estimates and measured data from 64 sample points which were not used in the spatial estimation process. The present study shows that, for the estimation of the hard-soil layer, ordinary Kriging offered the best performance among the evaluated techniques.

Percolation theory in engineering: a practical approach

Engineers work with a great variety of materials including porous media, polymers, composites, etc. A powerful tool for studying their behaviour and to model many of their properties, is the so-called Percolation Theory. However, many engineers face these types of problems via classical theories without the knowledge of the capabilities of innovative approaches such as percolation or sets renormalisation theory. In fact, many engineering problems could be satisfactory solved by resorting to the above mentioned theories. A review of the fundamentals of Percolation Theory as well as some examples of their use in solving actual engineering problems, is presented.