Effects of aggregate size on water retention capacity and microstructure of lime-treated silty soil

International audienceLime treatment is a common technique of improving the workability and geotechnical properties of soils. In this study, the aggregate size effects on the water retention capacity and microstructure of lime-treated soil were investigated. Two soil powders with different maximum aggregate sizes (D max = 0·4 and 5 mm) were prepared and stabilised by 2% lime (by weight of dry soil). Soil samples were prepared by compaction at dry side of optimum water content (w = 17%) with a dry density of 1·65 Mg/m 3. Suction and pore size distribution were determined after different curing periods. The results obtained show that: (a) the treated soil with smaller D max presents relatively smaller modal sizes and lower frequency of macropores (10–330 μm); (b) lime addition effectively improves the soil water retention capacity and decreases both the modal sizes of macro-and micropores gradually over time. Moreover, a higher air entry value and larger water retention capacity were also observed for a smaller D max value, in agreement with the pore size distributions

Desiccation and cracking behaviour of clay layer from slurry state under wetting-drying cycles

International audienceLaboratory tests were conducted to investigate the effect of wetting-drying (W-D) cycles on the initiation and evolution of cracks in clay layer. Four identical slurry specimens were prepared and subjected to five subsequent W-D cycles. The water evaporation, surface cracks evolution and structure evolution during the W-D cycles were monitored. The effect of W-D cycles on the geometric characteristics of crack patterns was analyzed by image processing. The results show that the desiccation and cracking behaviour was significantly affected by the applied W-D cycles: the measured cracking water content c, surface crack ratio Rsc and final thickness hf of the specimen increased significantly in the first three W-D cycles and then tended to reach equilibrium; the formed crack patterns after the second W-D cycle were more irregular than that after the first W-D cycle; the increase of surface cracks was accompanied by the decrease of pore volume shrinkage during drying. In addition, it was found that the applied W-D cycles resulted in significant rearrangement of specimen structure: the initially homogeneous and non-aggregated structure was converted to a clear aggregated-structure with obvious inter-aggregate pores after the second W-D cycle; the specimen volume generally increased with increasing cycles due to the aggregation and increased porosity. The image analysis results show that the geometric characteristics of crack pattern were significantly influenced by the W-D cycles, but this influence was reduced after the third cycle. This is consistent with the observations over the experiment, and indicates that the image processing can be used for quantitatively analyzing the W-D cycle dependence of clay desiccation cracking behaviour

A Study of the Hydro-Mechanical Behaviour of Compacted Crushed Argillite

International audienceThe argillite extracted from Bure site (France) is proposed, after being crushed and com-pacted, as a possible sealing and backfill material in the geological high-level radioactive waste disposal. In this study, the effects of the grain size distribution and the microstruc-ture on the hydro-mechanical behaviour of the compacted crushed argillite have been in-vestigated. The volume change properties were investigated by running one-dimensional compression tests under constant water content (2.4-2.8%) with loading-unloading cycles. Under various vertical stresses, water flooding tests were carried out in constant volume condition. Depending on the vertical stress level, either swelling or collapse behavior was observed in the sense that vertical stress increased or decreased upon flooding respectively. A clear effect of grain size distribution has been also identified: finer samples exhibit stiffer compression behaviour and higher swelling potential. To provide a microstructure insight into the macroscopic behaviour feature observed, both mercury intrusion po-rosimetry (MIP) and scanning electron microscopy (SEM) observations were performed, evidencing that: (i) at the same dry density, the size of inter-aggregates pores is larger for the coarser crushed material; (ii) mechanical compression only reduces the inter-aggregate porosity in the stress range considered; (iii) the micro-mechanisms governing the flooding under constant-volume condition include the swelling of the clay particles, the increase of the intra-aggregate pores and the collapse of the inter-aggregates pores. The results show a strong effect of the grain size distribution on the hydro-mechanical behaviour and thus the close link between the microstructure and the hydro-mechanical behaviour

Investigating the Swelling Pressure of Compacted Crushed-Callovo-Oxfordian Claystone

International audienceThis paper presents an experimental study on the swelling pressure of heavily compacted crushed Callovo-Oxfordian (Cox) claystone at a dry unit mass d = 2.0 Mg/m3 using four different methods: constant-volume, swell-reload, zero-swell and adjusted constant-volume method. Results show that the swelling pressure varies in the range of 1-5 MPa and depends significantly on the test method. From the constant-volume tests, it is observed that the swelling behaviour during wetting is a function of the suction and depends on both the hydration paths and wetting conditions (e.g. vapour-wetting or liquid-wetting). The swelling pressure decreases significantly with saturation time. To identify the microstructure changes of specimens before and after wetting, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) tests were performed. It is observed that, after wetting, the large inter-aggregate pores observed in the as-compacted specimen are no longer apparent; the whole pattern is characterized by a general swell of hydrated clay particles, rendering the soil more homogeneous. Results from MIP indicated that wetting caused a significant reduction of the entrance diameter of the dominant inter-aggregate pores from 2.1 to 0.5 m whereas intra-aggregate pores were not significantly influenced

Epiphytic microbiota source stimulates the fermentation profile and bacterial community of alfalfa-corn mixed silage

The epiphytic microbiota source on plants plays a crucial role in the production of high-quality silage. To gain a better understanding of its contribution, the microbiota of alfalfa (M1C0), corn (M0C1) and the resulting mixture (M1C1) was applied in alfalfa-corn mixed silage production system. M1C0 decreased ammonia-N levels in terms of total nitrogen (57.59–118.23 g/kg TN) and pH (3.59–4.40) values (p < 0.01), which increased lactic acid (33.73–61.89 g/kg DM) content (p < 0.01). Consequently, this resulted in higher residual water-soluble carbohydrate (29.13–41.76 g/kg DM) and crude protein (152.54–167.91 g/kg DM) contents, as well as lower NDF (427.27 g/kg DM) and ADF (269.53 g/kg DM) contents in the silage compared to M1C1- and M0C1-treated samples. Moreover, M1C0 silage showed significantly higher bacterial alpha diversity indices (p < 0.05), including the number of observed species and Chao1 and Shannon diversity indices, at the later stages of ensiling. Lactobacillus, Kosakonia and Enterobacter were the dominant bacterial species in silages, with a relative abundance of >80%. However, the abundance of Lactobacillus amylovorus in M0C1- and M1C1-treated silage increased (p < 0.01) in the late stages of ensiling. These findings confirmed that the epiphytic microbiota source exerts competitive effects during anaerobic storage of alfalfa-corn mixed silage

Multiple Sclerosis Identification by 14-Layer Convolutional Neural Network With Batch Normalization, Dropout, and Stochastic Pooling

Aim: Multiple sclerosis is a severe brain and/or spinal cord disease. It may lead to a wide range of symptoms. Hence, the early diagnosis and treatment is quite important.Method: This study proposed a 14-layer convolutional neural network, combined with three advanced techniques: batch normalization, dropout, and stochastic pooling. The output of the stochastic pooling was obtained via sampling from a multinomial distribution formed from the activations of each pooling region. In addition, we used data augmentation method to enhance the training set. In total 10 runs were implemented with the hold-out randomly set for each run.Results: The results showed that our 14-layer CNN secured a sensitivity of 98.77 ± 0.35%, a specificity of 98.76 ± 0.58%, and an accuracy of 98.77 ± 0.39%.Conclusion: Our results were compared with CNN using maximum pooling and average pooling. The comparison shows stochastic pooling gives better performance than other two pooling methods. Furthermore, we compared our proposed method with six state-of-the-art approaches, including five traditional artificial intelligence methods and one deep learning method. The comparison shows our method is superior to all other six state-of-the-art approaches

Alcoholism Identification Based on an AlexNet Transfer Learning Model

Aim: This paper proposes a novel alcoholism identification approach that can assist radiologists in patient diagnosis.Method: AlexNet was used as the basic transfer learning model. The global learning rate was small, at 10−4, and the iteration epoch number was at 10. The learning rate factor of replaced layers was 10 times larger than that of the transferred layers. We tested five different replacement configurations of transfer learning.Results: The experiment shows that the best performance was achieved by replacing the final fully connected layer. Our method yielded a sensitivity of 97.44%± 1.15%, a specificity of 97.41 ± 1.51%, a precision of 97.34 ± 1.49%, an accuracy of 97.42 ± 0.95%, and an F1 score of 97.37 ± 0.97% on the test set.Conclusion: This method can assist radiologists in their routine alcoholism screening of brain magnetic resonance images

Stress and strain evolution of remoulded COx argillite during saturation

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