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8. Research on stress distribution and deformation law of surrounding rock of deep and large mining height gob-side entry retaining

Author

XU Zhengzheng, YANG Yugui, CHEN Yong, HOU Shanshan, and CHEN Xiaohu

Subjects
gob-side entry retaining, large mining height, high water filling, numerical simulation, stress evolution, law of deformation, Mining engineering. Metallurgy, TN1-997
Abstract

To study the mechanical properties of high water filling materials, achieving the purpose of filling the side of the roadway, through uniaxial compression tests on high water materials with different water-cement ratios, we analyze the relationship of uniaxial stress-strain and the relationship of strength and maintenance at different stages. Taking Xishan Coal and Electricity Tunlan Mine as the engineering background, the deformation characteristics of the surrounding and the stress evolution law were investigated by numerical analysis. The results show that with the increase of water-cement ratio, the strength of high-water filling material decreases obviously, the uniaxial compressive strength of the material is 6.62 MPa when the water-cement ratio is 1.5∶1, 4.08 MPa when the water-cement ratio is 2∶1, and 2.85 MPa when the water-cement ratio is 2.5∶1, which are reduced by 38% and 60%, respectively; in the tunneling stage, the maximum roof and floor movement is 45.6 mm, and the maximum roof and floor movement is 203.0 mm during mining. During the period of roadway retention, the roadway is greatly affected by mining within 30 m of the advance working face, and the roof obviously sinks.

Published
2022
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50. Morphological change of the mouth bar in relation to natural and anthropogenic interferences

Author

Ying Chen, Yao Wu, He Yong, Yang Yugui, Wu Menwu, and Chen Lu

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Sediment, Geology, Empirical orthogonal functions, Estuary, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, Mouth bar, 01 natural sciences, Thalweg, Erosion, Bathymetry, 0105 earth and related environmental sciences, Bar (unit)
Abstract

Mouth bars are important morphological units in deltaic and estuarine systems, which have encountered with significant topography variations driven by anthropogenic interferences and natural forcings. On the basis of seven selected maritime charts covering from 1960s to 2016, we focus on the morphological evolution of mouth bar with bifurcating channels in the Modaomen Estuary, the main fluvially-dominated estuary of the Pearl River Delta. The bar area is relatively in equilibrium with barely aggregation and degradation before 1990 while overall erosion was found thereafter. Sediment volume of the mouth bar between the −2 m and −7 m isobaths drastically decreased after 1990s. Correspondingly, the area of −4 m isobaths of the bar stepwise decreased from about 18 × 106 m2 to 2 × 106 m2, indicating the body of mouth bar above −4 m almost disappeared. The two side channels also suffered significantly morphological evolution. The West Channel (WC) was subjected to uninterrupted erosion. Especially during 2000–2005, the WC below the −2 m isobath experienced remarkable erosion with the increment of water volume reaching 6.7 × 106 m3. The East Channel (EC) had the potential to expand seaward between 2000 and 2011 yet encountered with accumulation after 2011. Meanwhile, the thalweg of the EC seemed hard to distinguish and the WC displayed more meandering thalweg. Furthermore, Empirical Orthogonal Function was applied to quantify the bathymetric changes with independent modes. The temporal variations of fluvial sediment input displayed significant decreasing trend at MK from 1960 to 2014, which presented a statistically significant relationship with the third mode. However, it only accounts for 13.4% of the overall evolution patterns. Although the remarkable reduction of sediment input generally associates with the degradation in bar area, the sediment load is probably not the primary mechanisms driving morphological changes in the Modaomen Estuary. Anthropogenic interferences including large-scale reclamation and intensive sand excavation should be responsible for the morphological changes.

Published
2019

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