Experimental and numerical investigation on coal drawing from thick steep seam with longwall top coal caving mining

Steep coal seam mining activities will frequently occur during the next few decades in China. In this study, both experimental and numerical methods are employed to investigate the coal drawing from thick steep seam with longwall top coal caving mining. A series of analyses is performed to investigate the features of the drawing body, the distribution of top coal recovery ratio and the shape of the rock flow under steep conditions. The results indicate that the drawing body of top coal develops prior to upper side of the panel face obviously, and the top coal in the central part of the panel has a higher recovery ratio than that in the lower and upper parts in steep coal seam with caving mining method. The flow paths of the fragmented top coal are nearly straight lines moving towards the drawing window, and the fastest path maintains a constant angle with the plumb line. The spatial shape of the rock flow indicates “bidirectional asymmetry,” which results from the presence of the shield beam and dip angle of the coal seam; thus, this is the root cause of the appearance of the drawing body’s prior development towards the upper side of the panel. The field observation data indicates the same distribution of top coal recovery as that in the physical experiment and numerical simulation. Furthermore, suggested measurements are proposed to improve top coal recovery in steep seam mining based on the engineering practice of Dayuan coal mine.     

Study on the natural radioactivity level of stone coal-bearing strata in East China

Based on γ-radiation dose rate and radon concentration measurements and ²³⁸U, ²³²Th, ²²⁶Ra, and ⁴⁰K radionuclide testing, this study identifies the radioactive anomalies of stone coal-bearing strata in East China and evaluates the natural radioactivity levels in the air, solid, water and plant media in the typical area of the regional stone coal-bearing layers. The stone coal-bearing strata in East China occur in the lower Cambrian system along the margin of the Yangtze block; additionally, the radioactive anomaly area is sporadically distributed in the stone coal-bearing layers. The background values of ²³⁸U, ²³²Th, ²²⁶Ra, and ⁴⁰K are higher in the stone coal-bearing areas, and the spatial distribution of these natural radionuclides shows significant variability. ²³⁸U and ²²⁶Ra clearly accumulate in the coal, coal gangue and soil and are the main sources of the environmental radiation in coal mines. The γ-radiation shows a higher background value in the stone coal-bearing area, and this radioactive pollution cannot be ignored. Typically, the effective dose of γ-radiation exceeds the limit value of 5 mSv/a, and the total α and total β concentrations of the groundwater are 10–30 times the limit value at some points. The residents near the mining area are subjected to a higher radiation dose, and the groundwater, building materials, and plants have been contaminated by the radioactive pollution sporadically through time. It is necessary to strengthen the monitoring work of radioactive environments and to take appropriate control measures.     

白马雪山冰川槽谷发育的形态特征及其影响因素探讨

白马雪山地处横断山脉腹地,对于重建西南季风影响区的环境变迁以及探讨冰川作用特点具有重要科学意义。这里保留着典型的晚第四纪冰川侵蚀地貌,其中冰川槽谷发育特征明显。本文运用抛物线形态参数、梯级宽深比、形态比率等定量分析冰川槽谷的研究方法,对保存在白马雪山主峰扎拉雀尼(5429m)东北坡的两条简单冰川槽谷的形态特征进行分析。采用7个典型剖面的形态特征参数与其他地区对比,探讨冰川槽谷发育的可能影响因素如水热条件、冰川性质、冰川规模、岩性特点、冰川作用时间等。结果显示: 白马雪山冰川槽谷抛物线形态参数b值为1.779,明显小于冰川性质相同的螺髻山(1.835),主要是由于区域降水条件的不同所造成的差异,而与冰川性质不同天山乌鲁木齐河源区(1.825)冰川槽谷的形态特征的差异,可能与冰川规模、作用时间以及岩性条件密切相关; 梯级宽深比中槽谷形态参数沿程变化可以反映冰川流动过程中的动力变化,梯级宽深比中的形态参数Af和Bf值最大处对应的谷肩位置接近雪线位置。根据槽谷谷肩的位置确定末次冰期早期/中期的雪线高度为4140m,这与用地貌法如冰斗底部高程法、侧碛堤最大高度法和冰川末端至冰斗后壁最大高度法等综合确定的雪线高度4092m基本一致。因此,在冰川槽谷发育的冰川作用区,用槽谷谷肩的海拔高度估算雪线高度可以成为一种比较可靠的确定古雪线方法; 白马雪山的冰川槽谷形态参数b-FR的特征表明,即使是海洋性冰川作用区也不符合Hiran和Aniya提出的山地冰川模式,但运用b-FR相关关系可以很好的反映冰川的侵蚀过程。白马雪山地区冰川侧蚀作用导致槽谷坡降值较小,底部较平坦宽阔,呈现出相对完整的U型形态。此外,用形态比率FR值也可以验证雪线的位置高度。     

Basin-wide Holocene environmental changes in the marginal area of the Asian monsoon,northwest China

In arid regions, because of spatial variability, using single climate records is difficult to reconstruct the past climate change for the drainage basins. Holocene environmental records were collected from the upper, middle and lower regions of the Shiyang River drainage basin in the marginal area of the Asian monsoon (northwest China). The main objective of this paper was to compare the records from the terminal lake and the middle and upper reaches of the basin to study the basin-wide environmental changes. During the early Holocene the vegetation was sparse, and the effective moisture was relatively low in the basin. The Holocene Climatic Optimum started between 7.0 and 8.0 cal ka BP, during which the lake level reached the highest level in the terminal lake; the vegetation density and the effective moisture reached the highest level during the Holocene in the drainage basin. From 4.7 cal ka BP the terminal lake began to shrink, while the vegetation density decreased dramatically. In the middle and upper regions of the drainage, the effective moisture began to decrease since 3.5 cal ka BP, and the arid tendency was earlier in the terminal lake than it was in the middle and upper regions of the drainage basin. During the early Holocene the relatively arid environment was affected by the gradually intensifying East Asian monsoon and the dry westerly winds. The mid-Holocene Optimum benefited from the intensive East Asian monsoon and the humid westerly winds. Then, the East Asian monsoon retreated since the late-Holocene. In the basin the arid tendency may be related to the retracting of the East Asian monsoon. However, the intensifying acidification after 1.5 cal ka BP may be correlated to the increasing dryness of the westerly winds.     

Advances in Oxygenation Theory and Technology in Deep Lakes

Deep lakes always maintain vertical thermal stratification due to their physical structure. The thermocline prevents the transfer of oxygen from epilimnion to hypolimnion, leading to the formation of anoxic conditions in deeper water, the enhanced release of endogenous pollutants and the deterioration of water quality. Oxygenation is an effective measure to improve the water quality of deep lakes and mitigate the release of endogenous pollutants via the increase of the oxygen level in water. This paper provided an overview of the method and theory of oxygenation in deep lakes. Advantages and limitations of different methods of oxygenation, including artificial destratification, airlift aerators, Speece cone and bubble plume diffusers, were discussed. In addition, challenges and prospects of oxygenation were assessed based on the analyzing of typical examples of oxygenation in deep lakes and the difference in oxygenation system used in deep lakes and shallow lakes.     

Phosphorus speciation in surface sediments of a hypertrophic lake,Southwestern China: insights from fractionation and 31P NMR

Acta Geochimica - Phosphorus (P) species in surface sediments from a shallow, hypertrophic lake, Lake Dianchi, China, were investigated by P fractionation and 31P nuclear magnetic resonance (NMR)...     

Geochronology and geochemistry of the Hekoulinchang Sn-Pb-Zn-Ag polymetallic deposit (73240 t) in Heilongjiang Province,China

The Hekoulinchang Sn-Pb-Zn-Ag polymetallic deposit(20000 t Sn at 0.27%,236 t Ag at 122.89 g/t,15000 t Pb at 0.84%,and 38000 t Zn at 1.43%)is located in the Wandashan Terrane of the easternmost segment of the Central Asian Orogenic Belt.The timing of Sn-Pb-Zn-Ag polymetallic mineralization remains unclear due to a lack of precise isotope dating directly conducted on ore minerals.The authors herein report that the LA-ICP-MS U-Pb ages of cassiterite and zircon from the granite porphyry in the Hekoulinchang Sn-Pb-Zn-Ag polymetallic deposit are 101.4±7.9 Ma and 115.4±1.0 Ma,respectively,indicating that Sn mineralization and magmatism occurred during the Early Cretaceous.The granite porphyry belongs to the subalkaline series peraluminous I-type granites that are depleted in Nb,Ta,and Ti and enriched in Rb,Th,U,and Pb.TheεHf(t)values of the granite porphyry range from 0.9 to 7.4,with an average of about 5.6 and two-stage model ages(T_DM2)of 705–1116 Ma,with an average age of 819 Ma.The ε_Nd(t)values of the apatites are–1.60–0.45,with an average of–0.9,and two-stage model ages(T_DM2)of 872–1040 Ma,with an average age of 983 Ma.The Nd-Hf isotope data indicate that the magma may have been derived from the partial melting of juvenile crustal material.     

Multielemental Neutron Activation Analysis of Chinese Geochemical Reference Samples

The concentrations of 36 elements in geochemical reference samples issued by the Ministry of Geology and Mineral Resources of China were determined by neutron activation analysis. Three main variants of the technique, instrumental, epithermal, and nreirradiation separation neutron activation analysis (INAA, ENAA, PNAA), were employed in a systematic study of the samples by three laboratories: the Institute of Atomic Energy of the Academia Sinica (INAA, ENAA), the Institute of High Energy Physics of the Academia Sinica (INAA), and the Institute of Geophysical and Geochemical Prosnecting of the Ministry of Geology and Mineral resources (INAA,PNAA). Both long and short irradiations and both Ge(Li) and HPGe detectors were used. A supplementary software nackage for data processing was developed. About 81% of the data determined by neutron activation agreed with recomended values with in 15%.     

钴—5—Br—PADNm络合物的光度性质研究及其应用

本文研究了钴(Ⅱ)-5-Br-PADNm络合物的光度性质。在pH5.0缓冲溶液中,有TritonX-100存在时,Co~(2 )与5-Br-PADNm形成1:2红色络合物,λ_(max)为547nm,ε为1.35×10~5l·mol~(-1)·cm~(-1)。所提出的方法用于矿石及茶叶中Co的测定,得到满意结果。     

强夯地基效应及加固机制浅析

强夯地基效应,是指经强夯处理使地基土的结构形式,强度和变形大小,及其作用过程发生的改变。通过对强夯过程中一系列的现象分析,揭示强夯地基效应的形成机制,对强夯地基效应的三个方面及其之间的联系进行分析,其结论对于强夯处理设计和加固机制的认识有较大意义。