Fracture mechanism simulation of inhomogeneous anisotropic rocks by extended finite element method

The vast majority of rock masses is anisotropic due to factors such as layering, unequal in-situ stresses, joint sets, and discontinuities. Meanwhile, given the frequently asymmetric distribution of pores, grain sizes or different mineralogical compounds in different locations, they are often classified as inhomogeneous materials. In such materials, stress intensity factors (SIFs) at the crack tip, which control the initiation of failure, strongly depend on mechanical properties of the material near that area. On the other hand, crack propagation trajectories highly depend on the orthotropic properties of the rock mass. In this study, the SIFs are calculated by means of anisotropic crack tip enrichments and an interaction integral are developed for inhomogeneous materials with the help of the extended finite element method (XFEM). We also use the T-stress within the crack tip fields to develop a new criterion to estimate the crack initiation angles and propagation in rock masses. To verify and validate the proposed approach, the results are compared with experimental test results and those reported in the literature. It is found that the ratio of elastic moduli, shear stiffnesses, and material orientation angles have a significant impact on the SIFs. However, the rate of change in material properties is found to have a moderate effect on these factors and a more pronounced effect on the failure force. The results highlight the potential of the proposed formulation in the estimation of SIFs and crack propagation paths in inhomogeneous anisotropic materials

Engineering Geological Problems Associated With Karst Terrains: Their Investigation. Monitoring, And Mitigation And Design Of Engineering Structures On Karst Terrains

The design and construction of civil engineering structures in karst regions confronts many problems due to unpredictable location, dimensions and geometry of the karst structure and voids. Karst terrain is one of the most intricate grounds to be assessed for civil engineering purposes. Conventional methods of site exploration like desk studies, site reconnaissance, borings, test pits, geophysical techniques, have their advantages and disadvantages; none of them are 100% accurate; therefore they should be used in concert, adapted to each project, the available budget and the undertaken risk. As not two sides are identical in karst, site investigation should be tailored to each site. Factors that should be considered when designing site investigation in karst are: maturity of karst landforms, depth of the karst features, overburden thickness, lateral extent of the karst features, hydrogeology of the area, laoding, etc. The main problems confronted by engineers designing structures on or in karst terrain are: difficulties in excavation and grading the ground over pinnacled rockheads; collapse of the roof over subsurface voids, subsidence of cover soil over sinkhole, difficulties in founding a structure over an irregular or pinnacled rockhead, loss of water from dam reservoirs, pollution of groundwater, etc. A number of solutions have been practiced by engineers to solve these problems like: relocating the structure on a safer site, filling the voids and the fractures with concrete, improving the foundation ground with grouting and/or geogrids, replacing foundation soil, bridging the voids with rigid mats or beams, using deep foundations (piling, drilled shafts, etc.), minimizing future sinkhole development by controlling surface and ground water, etc

Influence of surface roughness on color changes in building stones

The influence of surface roughness on color change in several Spanish building stones is studied in samples of the following: Red Alicante, Black Marquina, White Macael, and Yellow Triana. In an experimental laboratory test (acid attack), we simulated the weathering process and made a comparative analysis between this and the polishing process. Changes in both color and roughness were measured during these processes. In limestones with medium or high chroma (Red Alicante) and both low chroma and lightness (Black Marquina), the total color changes were particularly affected in both the polishing and acid attack processes. On the other hand, in marbles with both low chroma and high lightness (White Macael and Yellow Triana), the total color changes were almost imperceptible in both processes. However, no change occurred in the hue of any of the analyzed stones. Spectrophotometric data showed that color change was due mainly to changes in surface roughness and not to chemical reactions that may have altered the oxidation state of the chromophore in the chromogen of the stone.Contract grant sponsor: Research Project GV-97-RN-14-3 Contract grant sponsor: predoctoral research fellowship from Generalitat Valenciana awarded to D. Benavente

Engineering Geological Problems Associated With Karst Terrains: Their Investigation. Monitoring, And Mitigation And Design Of Engineering Structures On Karst Terrains

The design and construction of civil engineering structures in karst regions confronts many problems due to unpredictable location, dimensions and geometry of the karst structure and voids. Karst terrain is one of the most intricate grounds to be assessed for civil engineering purposes. Conventional methods of site exploration like desk studies, site reconnaissance, borings, test pits, geophysical techniques, have their advantages and disadvantages; none of them are 100% accurate; therefore they should be used in concert, adapted to each project, the available budget and the undertaken risk. As not two sides are identical in karst, site investigation should be tailored to each site. Factors that should be considered when designing site investigation in karst are: maturity of karst landforms, depth of the karst features, overburden thickness, lateral extent of the karst features, hydrogeology of the area, laoding, etc. The main problems confronted by engineers designing structures on or in karst terrain are: difficulties in excavation and grading the ground over pinnacled rockheads; collapse of the roof over subsurface voids, subsidence of cover soil over sinkhole, difficulties in founding a structure over an irregular or pinnacled rockhead, loss of water from dam reservoirs, pollution of groundwater, etc. A number of solutions have been practiced by engineers to solve these problems like: relocating the structure on a safer site, filling the voids and the fractures with concrete, improving the foundation ground with grouting and/or geogrids, replacing foundation soil, bridging the voids with rigid mats or beams, using deep foundations (piling, drilled shafts, etc.), minimizing future sinkhole development by controlling surface and ground water, etc

Porcine respiratory syndrome causes significant mortality in wild boar piglets

Presentado a la 12th Conference of the European Wildlife Disease Association (EWDA), celebrada en Berlin (Alemania) del 27 al 31 de agosto de 2016.Peer Reviewe