Scale modelling should be a very useful strategy for the design of lunar structures. Preventing structural damages in the lunar environment is crucial and scale models are helpful to achieve this ...aim. The size of these models must be scaled to take into account the different gravitational levels. Since the lunar gravity acceleration is about one-sixth of the terrestrial one, it follows that the models on Earth will be very smaller than the prototype to be realized on the Moon. This strategy will represent an opportunity for engineers working on lunar structure design, provided that the errors, both computational and experimental, related to the change of scale are quantified, allowing reliable extension of the physical scale modelling results to the prototype. In this work, a three-dimensional finite element analysis of walls retaining lunar regolith backfill is described and discussed, in order to provide preliminary results, which can guide a future experimental investigation based on physical scale-modelling. In particular, computational errors related to the scale effects are assessed, with respect to a virtual prototype of the lunar geotechnical structure, and compared with errors from other sources of discrepancy, like the adopted constitutive model, the variability of the geotechnical parameters and the calculation section used in the 3D analysis. The results seem to suggest the soundness of this strategy of modelling and are likely to encourage new research, both numerical and experimental, supporting the structure serviceability assessment.
With increasing awareness about environmental sustainability issues, the geotechnical engineering community is in search of sustainable materials, innovative applications and ground improvement ...technologies which are resilient to climate change, involve low carbon emissions, are ecologically friendly and affordable, yet effective. As such, this reprint brings together 18 novel contributions providing the state-of-the-art in “Sustainable Geotechnics” with special focus on the reuse and recycling of waste materials in geotechnical applications as well as sustainable design, construction, and monitoring of the performance of geostructures. This reprint may be of particular interest to geotechnical professional engineers and researchers who are facing the challenging task of increasing the sustainability and resiliency of geotechnical assets and infrastructures.
In this study the effect of using a biopolymer soil stabilizer on soil stiffness characteristics was investigated. Chitosan is a bio-waste material that is obtained by chemical treatment of chitin (a ...chemical component of fungi or crustaceans’ shells). Using chitosan solution as a soil stabilizer is based on the assumption that the biopolymer forms temporary bonds with soil particles. What is important is that these bonds are biodegradable, so the product does not leave any harmful waste and has high eco-compatibility. The biopolymer itself is a by-product of many industrial chemical processes, so its application is compliant with the goals of sustainable geotechnical engineering. The effect of chitosan on soil shear strength, permeability or surface erosion has already been investigated in several different studies. In this study specimens of low-cohesive soil stabilized with two different chitosan solutions were subject to cyclic loading (torsional shearing test) and dynamic loading (resonant column) to obtain soil shear modulus G as a function of strain values. It has been shown that chitosan solution added to medium-grained materials improves their shear modulus G substantially (up to 3 times) even for relatively low chitosan concentration solutions (1.5 g of chitosan per 1 kg of dry silica sand). The results obtained in this study and the known chitosan properties suggest that chitosan solutions can be a very effective and eco-friendly short-term stabilizer for temporary geotechnical structures, e.g., working platforms.
A significant part of geotechnical structures such as parts of tunnels, adits, retaining walls, etc., is made of reinforced concrete. In reinforced concrete structures there are often cracks in ...places where they were not considered in the design. It is up to the engineer performing the fault diagnosis to determine the nature of the cracks, the cause of the occurrence and the follow-up measures to prevent their further development or eventual sanitation. The principles of conventional methods of visual diagnosis of such structures are simple, but possible disturbances may occur in inaccessible places. Typically, performing visual diagnostics requires stopping the operation in the surrounding areas of structure under investigation to ensure the safety of the persons performing it. As a result, a device that ensures continuous monitoring of cracks even in hard-to-reach areas or in locations with increased operation has been developed. This device can continuously monitor the evolution of the crack over time, store the evaluated data chronologically or send it to the server, and notify the competent authorities about changes.
Construction of geotechnical structures on marine soils improved by deep mixing method (DMM) is recent trend in Korea. Since there are many uncertainties involved in the design of structures on DMM ...foundation, introducing reliability methods to deal with uncertainties of DMM foundation has been discussed in the engineering society. This two-paper set addresses the reliability assessment applied to the design of the structures on DMM improved soil. In the first paper, the compressive strength data collected from the sites of DMM improved soil were analyzed and their Coefficient of Variation (COV) and probability distribution were decided. COV of compressive strength data obtained from the sites of DMM improved soil was 0.34, which was relatively smaller than the values obtained from other countries, because domestic use of the types of mixing equipment and material are not diversified. The probability distribution of the compressive strength data fit both to normal and lognormal distributions. Six limit state functions were formulated corresponding to both the external and internal stabilities of the structures on DMM improved soil. The companion paper addressed the implementation of the reliability analyses and proposed the target reliability index for the geotechnical structures on DMM improved soil.
In this paper, a new triangular discretization method for two-dimensional random field is proposed, and thecomputational formula of the covariance for any two triangular random field elements is ...developed. Its main advantage, compared to thequadrilateral discretization method, is that triangular local average method can perfectly combine with thetriangular finite element method. Also, the corresponding relation is clearer and the computer codes are simpler. Based on the new local average method, a numerical analysis for random temperature field of geotechnical structures under heat conduction conditions is presented by the Monte-Carlo method, and the computational formulas of mathematical expectation matrix and standard deviation matrix are provided. A series of computer codes have beencompiled by Matrix Laboratory (MATLAB) software. A numerical example is presented to demonstrate the random effects of uncertain parameters, and the accurateness of the proposed approach is proven by comparing these results with the results derived from quadrilateral local average method.
During the last years solid waste disposal has increasing significantly, causing health and environmental problems. In order to study an alternative to mitigate these problems, the re-use of ...polyethylene- terephthalate bottles as a replacement of conventional lightweight materials used on the leveling or filling of soils is investigated.For this purpose, a mechanical characterization of the PET most popular bottles on the market was carried out. Laboratory test results indicate that PET bottles exhibit compression resistances, which suggest that this material can be used on the construction of lightweight structures.
In many geotechnical engineering cases, the factor of safety may be defined as the ratio of the capacity, of the geotechnical structure or its support elements, to the pertinent demand. By ...representing the capacity and the demand as independent piecewise linear random variables, an analytic solution is obtained for the probability density and cumulative distribution functions of the factor of safety. Thus, solutions for the calculation of the mean value, the standard deviation and the minimum and maximum values of the factor of safety, are provided. Application of the developed analytical solutions, to the probabilistic analysis of a published case of rock spalling in a deposition tunnel complex, follows. The methodology allows for the parametric evaluation of the effect of specific design variables to the distribution of the safety factor and to the probability of failure. The closed form solution may be programmed as a computer code that may run easily on a tablet or netbook or even on a smartphone. It proves useful for the probabilistic design of a variety of geotechnical applications, such as foundations, tunneling, mining, underground roof reinforcement, and earth retaining structures, and permits decisions to be taken in terms of risk and reliability.
Durante los últimos años la producción de residuos sólidos ha aumentado significativamente, causando problemas de salud y medio ambiente. Con el fin de plantear una alternativa para mitigar estos ...problemas, se investiga la reutilización de los envases de Polietileno-Tereftalato (PET) como una sustitución de materiales ligeros convencionales utilizados en la nivelación o reemplazo de suelo. Para ello, se llevó a cabo una caracterización mecánica de los envases de PET más populares en el mercado de forma individual y grupal. Los resultados de las pruebas de compresión indican que los envases de PET exhiben resistencias de compresión que sugieren que estos se pueden aprovechar en la construcción de estructuras ligeras.
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