Person: Garzón Roca, Julio
Universidad Complutense de Madrid
Faculty / Institute
Geodinámica, Estratigrafía y Paleontología
Now showing 1 - 9 of 9
- PublicationIdentification and Mitigation of Subsidence and Collapse Hazards in Karstic Areas: A Case Study in Alcalá de Ebro (Spain)(MDPI, 2023-05-05) Gracia, Alberto; Torrijo, Francisco Javier; Garzón Roca, Julio; Pérez Picallo, Miguel; Alonso Pandavenes, OlegarioSinkholes are a severe problem in urban areas located in karstic regions, especially where evaporitic rocks such as gypsum exist. Identification and proposal of mitigation measures are needed to reduce this geo-hazard effect on buildings and social urban living. This paper presents a case study of the town of Alcalá de Ebro (Spain), which is located in the highest sinkhole risk region of Europe. The identification and mitigation of a series of sinkholes that appeared are analyzed. The former involves a geological investigation, including boreholes, field tests and geophysics. The latter is addressed by the use of geogrids, mortar injections and polyurethane injections. A complementary finite element analysis is carried out to set the ground behavior associated with the sinking process and assess its future evolution. The Ebro River appears to be the main cause of sinkholes, and results show that ground treatments applied were successful in their purpose, as there are no apparent deformations indicating that the subsidence or sinking process is still active in the area. The use of different techniques depending on the size of the sinkhole, the objectives pursued and the element affected is discussed.
- PublicationEarly Investigation of a Landslide Sliding Surface by HVSR and VES Geophysical Techniques Combined, a Case Study in Guarumales (Ecuador)(MDPI, 2023-01-12) Alonso Pandavenes, Olegario; Torrijo, Francisco Javier; Garzón Roca, Julio; Gracia, AlbertoThe access road to the powerhouse’s hydraulic system’s facilities in Guarumales (Azuay, Ecuador) presents a medium-sized landslide. Geophysical tests were conducted in the initial research stage, combining electrical and seismic methods. A vertical electrical sounding (VES) and horizontal to vertical spectral ratio (HVSR) survey campaign have been taken as a reference for the analysis of the landslide area. The distribution of these test points has been at three different levels along the landslide where the access road crosses it, trying to cover the area’s most extensive possible length and width. In the area, we find the geology dominated by the presence of schists, altered to different degrees and presenting blocks of material with a lower degree of alteration within colluvium formed by a clayey matrix and coarse material of the exact nature. There is also observed runoff water and groundwater in the area. The results obtained through SEV tests have allowed for defining the separation zone of the mobilized or sliding materials compared to the fixed or immobile ones (potentially, the sliding surface was marked). Using the HVSR technique, the natural vibration frequencies of the ground associated with the sliding mass (separation of seismic impedances between a two-layer model: mobile and fixed) have been determined. Previous authors proposed an empirical relationship establishing the exponential relationship, already proposed by previous authors, between sediment thickness and natural frequencies. It has been possible to determine the depth of the position of the loosely compacted sediment zone (and probably moving or mobilized) compared to that of compact materials (immobile) and thereby define the potential rupture surface.
- PublicationAbove the Ravines: Flood Vulnerability Assessment of Earthen Architectural Heritage in Quito (Ecuador)(MDPI, 2022) Trizio, Francesca; Garzón Roca, Julio; Eguibar, Miguel Ángel; Bracchi, Paola; Torrijo, Francisco JavierFloods represent one of the most threatening risks for earthen architectural heritage. Developing risk assessment tools is considered crucial to mitigate the risk and to protect heritage buildings. Due to its hygroscopic nature, earthen architecture is generally considered to be vulnerable to water, requiring a specific analysis. This paper proposes a vulnerability assessment method for earthen buildings in flood-prone areas. Based on the evaluation of the susceptibility of the building’s components and characteristics, the method allows for quantifying the vulnerability of the assets, in non-monetary terms. An application of the methodology is carried out assessing a selection of earthen construction in Quito Historic Centre (Ecuador). The results show the influence of each component in the global vulnerability of the earthen buildings. The response of different construction techniques and the importance of the maintenance of heritage buildings is exposed. Vulnerability assessment methods at the meso-small scale constitute the foundation for risk assessment. Thus, this study aims to provide a significant assessment tool that can be used for further analysis and future lines of research, aiming to protect cultural heritage that is at risk.
- PublicationDiagenesis, provenance and tectonic setting of siliciclastic rocks. A case study from Upper Devonian of the Iberian Chain (Tabuenca, Spain)(Consejo Superior de Investigaciones Científicas, Museo Nacional de Ciencias Naturales, 2022) Torrijo, Francisco Javier; Gozalo, Rodolfo; Garzón Roca, Julio; Company, JulioThis paper describes the petrography and infers the provenance of siliciclastic rocks from the Upper Devonian of the Iberian Chains (Tabuenca, NE Spain), and outlines the tectonic setting associated with the Ebro Massif. These Devonian deposits are constituted by four different siliciclastic units: the Rodanas, Bolloncillos, Hoya and Huechaseca Formations. The provenance and diagenesis of over 400 sedimentary rocks samples are studied with a combination of petrographic polarizing microscope, scanning electron microscopy, atomic absorption spectroscopy, X-ray fluorescence and X-ray diffraction. In this sense, AAS and XRF analysis were used to determine the content of Ca, Mg, Fe, Mn, Na, K and Sr, among others; and XRD analysis was used to determine the clay´s crystalline phases. These rocks experienced intense compaction and quartz cementation processes after deposition. No primary porosity remains nowadays and secondary porosity is rare. The formation of these siliciclastic rocks occurred mainly under subtropical climatic conditions, given the paleogeographical position of the current Iberian landmass during the Devonian.
- PublicationGeomechanical characterization and analysis of the Upper Cretaceous flysch materials found in the Basque Arc Alpine region(Springer, 2021) Garzón Roca, Julio; Torrijo, Francisco Javier; Company, Julio; Cobos, GuillermoFlysch materials are one of the most challenging geological materials and often give rise to slope instability problems. Due to its natural heterogeneity, geomechanical characterization of flysch materials is somewhat difficult. The Spanish Basque Arc Alpine region is a very well-known location for flysch materials. In this paper, an area of approximately 100 km2 in the region is intensively studied and their flysch materials geomechanically characterized. A total of 33 locations are investigated by a broad geological-geotechnical investigation, involving petrographic analyses, geomechanical stations, boreholes, and mechanical laboratory tests. In addition, a slope inventory was carried out to assess the situation in the existing slopes in the area. Characterization of materials is carried out in terms of RQD, RMR, and GSI as well as using the Hoek–Brown failure criterion. Different correlations are assessed, establishing their appropriateness for estimating the mechanical parameters of a flysch material rock mass.
- PublicationA Case Study of a Large Unstable Mass Stabilization: “El Portalet” Pass at the Central Spanish Pyrenees(MDPI, 2021-08-04) Cobos, Guillermo; Eguibar, Miguel Ángel; Torrijo, Francisco Javier; Garzón Roca, JulioThis case study presents the engineering approach conducted for stabilizing a landslide that occurred at “El Portalet” Pass in the Central Spanish Pyrenees activated due to the construction of a parking lot. Unlike common slope stabilization cases, measures projected here were aimed at slowing and controlling the landslide, and not completely stopping the movement. This decision was taken due to the slow movement of the landslide and the large unstable mass involved. The degree of success of the stabilization measures was assessed by stability analyses and data obtained from different geotechnical investigations and satellite survey techniques such as GB-SAR and DinSAR conducted by different authors in the area under study. The water table was found to be a critical factor in the landslide’s stability, and the tendency of the unstable slope for null movement (total stability) was related to the water table lowering process, which needs more than 10 years to occur due to regional and climatic issues. Results showed a good performance of the stabilization measures to control the landslide, demonstrating the effectiveness of the approach followed, and which became an example of a good response to the classical engineering duality cost–safety.
- PublicationCombining Project Based Learning and Cooperative Learning Strategies in a Geotechnical Engineering Course(MDPI, 2021) Torrijo, Francisco Javier; Garzón Roca, Julio; Cobos, Guillermo; Eguibar, Miguel ÁngelThis paper presents the implementation of a learning methodology following a student-centred approach. The methodology is based on the use of project based and cooperative learning and mainly consists of commissioning students to prepare a presentation on a topic of their subject. Students work in groups, and later must deliver a real lecture to their colleagues. The proposed methodology was applied across 7 years and its implementation was monitored via day-to-day observations, annual surveys, the gathering of direct feedback as well as by analysing the students’ academic performance. Results show the ability of the proposed learning methodology to enhance motivation and engagement of students, facilitate the improvement of four soft skills (team-working, practical thinking, effective communication and critical thinking), eliminate absenteeism and facilitate long-term retention of the knowledge and skills acquired in a subject.
- PublicationBasement tectonic structure and sediment thickness of a valley defined using HVSR geophysical investigation, Azuela valley, Ecuador(Springer, 2022) Alonso Pandavenes, Olegario; Torres, Gabriela; Torrijo, Francisco Javier; Garzón Roca, JulioUsing a small set of boreholes, as fixed information of basement, combined with the analysis of microtremor surveys, can provide a transversal detailed section of a valley where a dam was constructed. In this paper, horizontal to vertical spectra ratio (HVSR) technique is applied as a quick and economic method to establish the thickness of the sediments existing over rock basement in the San Marcos dam area, constructed in the Azuela valley (Cayambe, Ecuador). Previous investigations made for construction of dam did not reach the bottom of the 700 m transverse section of dam foundation; only the ends were well deferred, where the rock is close to surface. So, involving some little number of boreholes as control points, in comparison with other similar studies, a relation between natural frequency of ground vibration (fo) and sediment thickness is established. Along the dam toe, and over it, was measured 20 HVSR single station points and analysed in the three main directions (N-S, E-W, and Z) the components of ground natural vibrations (rumour). This provides the variation of the ratio between the horizontal components and the vertical one and using the natural frequency of vibration in each point can be established a correlation between this one and sediment thickness. After this, the geological cross-section of the bottom of the valley was delineated, revealing tectonic structures (faults) not defined before that they can be useful in further studies for control of settlement of dam. The new formula could be used too as a quick tool to investigate accurately the area around the dam and defined other tectonic structures not evidenced at this moment.
- PublicationFlood Hazards in Flat Coastal Areas of the Eastern Iberian Peninsula: A Case Study in Oliva (Valencia, Spain)(MDPI, 2021-10-21) Eguibar, Miguel Ángel; Porta-García, Raimon; Torrijo, Francisco Javier; Garzón Roca, JulioEnhancing resilience against flooding events is of great importance. Eastern Iberian Peninsula coastal areas are well known for high intensity rainfalls known as DANA or “cold drop”. Extreme records in 24 h can exceed the annual average of the historical series. This phenomenon occurs normally in autumn due to convective storms generated by the existence of cold air in the upper layers of the atmosphere combined with warm winds coming from the Mediterranean Sea. In many coastal areas of the Eastern Iberian Peninsula, their flat topography, sometimes of a marsh nature, and the natural (e.g., dune ridges) and man-made (e.g., infrastructures) factors, result in devastating flooding events of great potential damage and risk for urban and rural areas. In this context, this paper presents the case study of the town of Oliva (Valencia, Spain) and how in a flooding event the flow tends to spread and accumulate along the flat coastal strip of this populated area, causing great potential damage. From that point, the paper discusses the particular issues that flood studies should consider in such flat and heavy rainy areas in terms of the hydrological and hydraulic models to be conducted to serve as the key tool of a correct risk assessment. This includes the correct statistical simulation of rainfalls, the hydrological model dependency on the return period and the correct geometry definition of all possible water barriers. An analysis of the disturbance that climatic change effects may introduce in future flooding events is also performed.