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Approximation frameworks for phase-field models of brittle fracture are presented and compared in this work. Such methods aim to address the computational cost associated with conducting full-scale simulations of brittle fracture in heterogeneous materials where material parameters, such as fracture toughness, can vary spatially. They proceed by combining a dimension reduction with learning between function spaces. Two classes of approximations are considered. In the first class, deep learning models are used to perform regression in ad hoc latent spaces. PCA-Net and Fourier neural operators are specifically presented for the sake of comparison. In the second class of techniques, statistical sampling is used to approximate the forward map in latent space, using conditioning. To ensure proper measure concentration, a reduced-order Hamiltonian Monte Carlo technique (namely, probabilistic learning on manifold) is employed. The accuracy of these methods is then investigated on a proxy application where the fracture toughness is modeled as a non-Gaussian random field. It is shown that the probabilistic framework achieves comparable performance in the L2 sense while enabling the end-user to bypass the art of defining and training deep learning models. [ABSTRACT FROM AUTHOR]

Graded gravel is a typical filler for railroad subgrade and the procedures for designing and evaluating it are crucial. The current specifications only stipulate the physical indicators of graded gravel material groups and the mechanical indications following on-site compaction. The lack of indoor mechanical standards makes it impossible to predict the on-site construction. Furthermore, the specification specifies various varieties and vast ranges of gradation, making it difficult to construct a skeleton structure. The current specification uses the heavy compaction method (HCM) and static compaction method (SCM) for the test method of graded gravel, which are no longer compatible with the current vibration compaction molding process. In this work, the effects of grading types, compaction coefficients, and water content conditions on the mechanical properties of the subgrade surface grading gravel were studied. Then the correlation between the field and indoor mechanical indexes was investigated and the K30 predictive index of graded gravel was proposed and verified by combining it with the test section. The results show that compared with HCM and SCM, the correlation between vertical vibration compaction method (VVCM) and the field was greater than 90%. Compared with standard graded gravel, the California bearing ratio (CBR), Rc , and E0 of the strongly embedded skeleton compact gradation (VGM) graded gravel can be increased by 55%, 162%, and 171%, respectively. When the compaction coefficient increases by 1%, the CBR, Rc , and E0 can be increased by 12%, 28%, 31%, respectively. Compared with graded gravel with the optimal water content, the CBR, Rc , and E0 of dry graded gravel can be increased by 7%, 94%, and 14%. The proposed CBR1 design standard, Evd acceptance standard, and graded gravel design method can better predict the K30 index on-site. [ABSTRACT FROM AUTHOR]

Herein, a vertical vibration compaction method (VVTM) is proposed to stimulate the practical compaction loading condition for a large stone asphalt mixture with nominal maximum size of 53 mm (LSAM-50) and its reliability is verified. The physical and mechanical properties of LSAM-50 specimens formed using VVTM and the static pressure method (PCT) were compared. The results show that the compression strength and splitting strength of VVTM specimens are 1.29 times and 1.31 times that of the PCT specimens, respectively. Compared with the field test, the compressive strengths of the VVTM and PCT specimens are 94.4% and 72.9% of the field core, respectively. The splitting strengths of the VVTM and PCT specimens are 89.5% and 68.0%, respectively. Additionally, the extraction test revealed that the degree of damage to the internal aggregates of VVTM specimens was considerably less than that of the PCT specimens. Therefore, the performance of VVTM specimens surpasses that of the PCT specimens, and the compaction effect of VVTM is more relevant to field compaction, making it a better choice for evaluating the mechanical and volumetric properties of LSAM-50. [ABSTRACT FROM AUTHOR]

The calculation method of asphalt film thickness was proposed by considering the specific surface area of coarse and fine aggregates [computed tomography (CT) and Blaine test methods] and the wrapping effect of fine particles (<0.075 mm) on the aggregates to investigate the optimal asphalt dosage of asphalt mixtures. The effect of asphalt film thickness on the pavement performance of asphalt mixtures was studied. The optimal asphalt film thickness determination method for asphalt mixtures is proposed based on the pavement performance. The study shows that the asphalt film thickness of 4.4 μm has the best high-temperature performance. The higher the asphalt film thickness, the better its low-temperature performance, water stability, and fatigue performance. The optimal asphalt film thickness is selected according to the performance requirements of the asphalt mixture in different structural layers and environmental conditions. [ABSTRACT FROM AUTHOR]

The effects of fiber type and content on the properties of emulsified asphalt cold recycled mixture (ECRM) produced using vertical vibration compaction are examined. The reliability of the vertical vibration testing method (VVTM) is verified by comparing the physical properties of VVTM-prepared samples with those prepared via the Marshall compaction method (MCM) and with the mechanical properties of core samples from a construction site. Furthermore, the mechanical strength and pavement performance of ECRM with different fibers are tested. Finally, using the entropy-weight technique for order of preference by similarity to ideal solution (TOPSIS) model, the fiber type and content for the optimal comprehensive performance of ECRM are recommended. Results show that the correlation between the mechanical strength of the VVTM-prepared ECRM sample and construction site core sample is >90%. An increase in fiber content first increases and then decreases the mechanical strength and road performance of the ECRM; its influence on water stability is not significant. With the same fiber content, the improvement effect of four fiber types on ECRM's comprehensive performance is ordered as follows: lignin fiber > polyester fiber > mineral fiber > basalt fiber. Based on the entropy-weight TOPSIS model, 0.4% lignin fiber content is the optimal scheme for the comprehensive performance of ECRM. Overall, the results provide a reference for the fiber type and content selection for ECRM and have important engineering significance for improving ECRM's comprehensive performance. [ABSTRACT FROM AUTHOR]

With the accelerated worldwide urbanization process, land-use zoning has been playing an increasingly important role in urban planning and development. Ahead of detailed planning, regional land-use zoning provides significant guidance to subsequent design and constructions, especially for large conurbations in less developed regions. Foshan, lies in the south of China with an area of 3,813.64 km2 and a population of about 3.36 million, is a typical Chinese city with a relatively well-developed industry. This paper studies how land-use zoning diagnose the present urban land use, optimize the landscape pattern, as well as improves urban development sustainability. On the basis of integrated evaluation of ecological capacity, ecological suitability, ecosystem services, and ecological footprint, this paper designs the three-level land-use zoning for Foshan. Four areas, 11 sections, and 78 cells have been designed within four main classifications of function zones: ecological conservation area, ecologically sensitive area, ecological construction area, and ecological regulation area. Accordingly the overall land-use pattern of Foshan has been clearly improved in terms of urban sprawl control, landscape pattern optimization, industrial layout redesign, and ecological conservation. [ABSTRACT FROM AUTHOR]