厚黏土层软弱覆岩采动破坏的泥盖效应

以榆神矿区某矿2301工作面为例,采用钻孔注水、孔内视频采集和相似材料模拟试验3种研究方法,对厚泥盖层下覆岩破坏规律进行了综合研究。通过井下钻孔冲洗液漏失量和孔壁裂隙发育特征的观测,确定了垮落带、导水裂缝带的发育高度,相似材料模拟试验揭示了采动裂隙“发生-发展-弥合”的动态演化特征,指出厚泥盖层下采动破坏显现出“泥盖效应”。同时,运用XRD、SEM和膨胀性测试等实验方法,分析了泥盖效应产生的矿物学原因。研究表明:薄基岩厚泥盖条件下,采高为7 m时,覆岩破坏高度为45.7~49.3 m,裂采比6.53~7.04,较类似开采条件中硬类型覆岩破坏高度降低了15%~53%;基岩厚度变化时,覆岩破坏形态呈现非对称特点,沿工作面推进方向呈现弥合分区特征,泥盖层在裂隙演变过程中易出现整体下沉,且对采动裂隙的上向发育起主导作用;黏土矿物具有的强塑性、亲水性、膨胀性等是泥盖效应产生的本质原因,当导水裂缝带上部的微小裂隙进入到黏土层,由于黏土矿物良好的膨胀性,使裂隙会在采动影响的发生和发展过程中自行闭合,同时泥盖层受载后亦易于密实,从而抑制导水裂缝带的发育,显现出“泥盖效应”相关特征。

Influence of vegetation cover and other sources of variability on sediment and runoff response in a burned forest in South Korea

Post-fire field measurements of sediment and run off yield were undertaken in natural rainfall event-basis during five rainy months in Korea on a total of 15 small plots: four replica burned unseeded plots, six replica burned seeded plots, and five replica unburned plots. The main aim was to evaluate the effects of vegetation recovery and spatial distribution patterns on sediment and runoff response between and within the treatment replica erosion plots. Sixyears after the wildfire, total sediment and runoff yield in the burned unseeded plots with 20%-30%vegetation cover was still 120.8 and 20.6 times higher than in the unburned treatment plots with 100%ground cover, 8.3 and 6.7 times higher than in the burned seeded plots with 70%-80% vegetation cover,while only 1.6 and 2.0 times higher than in the burned seeded plots with 50%-60% vegetation cover,respectively. The differences in sediment and runoff yield between the treatment plots was proportional to total vegetation cover, distance of bare soil to vegetation cover, magnitude of rainfall characteristics and changes in soil properties, but not slope gradient.Three out of the six within-treatment pairs of two replica plots showed large differences in sediment and runoff yield of up to 6.0 and 4.2 times and mean CV of up to 99.1% and 62.2%, respectively. This was due to differences in the spatial distribution patterns of surface cover features, including aggregation of vegetation and litter covers, the distance of bare soil exposed to vegetation cover closer to the plot sediment collector and micro topographic mounds and sinks between pairs of replica plots. Small differences in sediment and runoff of only 0.9-1.4folds and mean CV of 8.6%-25% were observed where the within-treatment pairs of replica plots had similar slope, total surface cover components and comparable spatial distribution pattern of vegetation and bare soil exposed surface covers. The results indicated that post-fire hillslopes undergoing effective vegetation recovery have the potential to reduce sediment and runoff production nearer to unburned levels within 6-years after burning while wildfire impacts could last more than 6-years on burned unseeded ridge slopes undergoing slow vegetation recovery.

Effect of Land Use Change on Runoff and Sediment Yield in Da River Basin of Hoa Binh province, Northwest Vietnam

The objective of this study was to assess runoff discharge and sediment yield from Da River Basin in the Northwest of Vietnam using Soil and Water Assessment Tools(SWAT) model.The SWAT model was calibrated and validated using the observed monthly stream flows and sediment yield at selected gauging stations.The results indicated that SWAT generally performs well in simulating runoff and sediment yield according to Nash-Sutcliffe efficiency(NSE), Observation's standard deviation ratio(RSR), and percent bias(PBIAS) values.For runoff, the values of NSE, RSR, and PBIAS were 0.98,0.02, and 3.69 during calibration period and 0.99,0.01, and 1.56 during validation period, respectively.For sediment yield, the efficiency was lower than the value of NSE, RSR, and PBIAS during calibration period were 0.81, 0.19, and-4.14 and 0.84, 0.16, and-2.56 during validation period, respectively.The results of the study indicated that the vegetation status has a significant impact on runoff and sediment yield.Changes in land use type between 1995 and2005 from forest to field crop and urban strongly contributed to increasing the average annual runoff from 182.5 to 342.7 mm and sediment yield from101.3 to 148.1 ton-1 ha.Between 2005 and 2010, adecrease of both runoff(from 342.7 to 167.6 mm) and sediment yield(from 148.1 to 74.0 ton-1 ha) was due to the expansion of forested area and application of soil conservation practices.The results of this study are important for developing soil and water conservation programs, extending future SWAT modelling studies and disseminating these results to other regions in Vietnam.

Influence of Vegetation on Runoff and Sediment in Wind-water Erosion Crisscross Region in the Upper Yellow River of China

All characteristics of vegetation,runoff and sediment from 1960 to 2010 in the Xiliu Gully Watershed,which is a representative watershed in wind-water erosion crisscross region in the upper reaches of the Yellow River of China,have been analyzed in this study.Based on the remote sensing image data,and used multi-spectral interpretation method,the characteristics of vegetation variation in the Xiliu Gully Watershed have been analyzed.And the rules of precipitation,runoff and sediment's changes have been illuminated by using mathematical statistics method.What′s more,the influence mechanism of vegetation on runoff and sediment has been discussed by using the data obtained from artificial rainfall simulation test.The results showed that the main vegetation type was given priority to low coverage,and the area of the low vegetation coverage type was reducing year by year.On the country,the area of the high vegetation coverage type was gradually increasing.In a word,vegetation conditions had got better improved since 2000 when the watershed management project started.The average annual precipitation of the river basin also got slightly increase in 2000–2010.The average annual runoff reduced by 37.5%,and the average annual sediment reduced by 73.9% in the same period.The results of artificial rainfall simulation tests showed that the improvement of vegetation coverage could increase not only soil infiltration but also vegetation evapotranspiration,and then made the rainfall-induced runoff production decrease.Vegetation root system could increases the resistance ability of soil to erosion,and vegetation aboveground part could reduce raindrop kinetic energy and splash soil erosion.Therefore,with the increase of vegetation coverage,the rainfall-induced sediment could decrease.

Temperature Effect Investigation toward Peat Surface CO2 Emissions by Planting Leguminous Cover Crops in Oil Palm Plantations in West Kalimantan

The aim of this research was to know the impact of planting leguminous cover crops （LCCs） of Mucuna bracteata and Calopogonium mucunoides in oil palm plantation on peatland on reducing CO2 emissions. Atmosphere temperature, peat surface temperature, in-closed chamber temperature and peat surface CO2 fluxes were monitored on two adjacent experimental plots. The first experimental plot was on the newly opened peat surface （NOPS） and another was on the eight years planted oil palm land （EPOL）. The closed chamber techniques adopted from International Atomic Energy Agency （IAEA） （1993） were implemented to trap CO2 emissions emitted from 24 treatment plots at the 1st, 3rd and 6th months observations. Average CO2 fluxes observed on no LCCs plots in the NOPS site were 61.25 ± 8.98, 33.76 ± 2.92 and 33.75 ± 3.45 g/m2.h, while in the EPOL site were 55.38 ± 15.95, 29.90 ± 5.32 and 27.70 ± 4.62 g/mLh at the 1st, 3rd and 6th months monitoring, respectively. Average CO2 fluxes observed on the planted M. bracteata plots in the NOPS site were 68.2 ± 24.5, 12.88 ± 3.70 and 10.40 ± 1.28 g/m2.h, whereas in the EPOL site were 54.04 ± 6.70, 11.45 ± 2.00 and 9.33 ± 3.49 g/m2.h at the 1st, 3rd and 6th months monitoring, respectively. Average CO2 flux observed on the planted C. mucunoides plots in the NOPS site were 66.5 ± 23.7, 15.41 ± 1.51 and 9.74 ± 2.55 g/m2.h, while in the EPOL site were 47.00 ± 5.00, 9.34 ± 1.23 and 10.52 ± 4.80 g/m2.h at the 1st, 3rd and 6th months, respectively. P-value for the experimental sites was 0.008 （〈 0.05）, indicating the significant difference in the level of CO2 fluxes between the sites. P-value for the treatments in the experimental plots was 0.000 （〈 0.05）, indicating markedly different level of CO2 fluxes among treatments. P-value for the age ofM. bracteata and C. mucunoides planted on the experimental plots was 0.000 （〈 0.05）, indicating the significant difference in the level of CO2 fluxes due to the enhanced LCCs age performing at the increase of shading effects. The comparison of CO2 fluxes among experimental plots shows that planting M. bracteata and C. mucunoides on the peatland could reduce CO2 emission.

榆林矿区浅埋深厚土层薄基岩煤层开采覆岩破坏规律研究

通过对陕北地区浅埋煤层的地质采矿条件研究,揭示陕北地区新近系红土层胶结性好,隔水能力强,能够抑制导水裂缝带的发育;由数值模拟及实践开采得出陕北地区浅埋深厚土层薄基岩煤层的覆岩结构为"上软下硬",岩性属软弱,煤层开采后覆岩破坏实测高度小于经验预计数值,符合"泥盖效应"规律,为类似条件保水开采提供了技术依据。

Effects of Vegetation Cover and Rainfall Intensity on Sediment-Bound Nutrient Loss,Size Composition and Volume Fractal Dimension of Sediment Particles

Vegetation and rainfall are two important factors affecting soil erosion and thus resulting in nutrient loss in the Chinese Loess Plateau.A field experiment was conducted to investigate the effects of rainfall intensities(60,100 and 140 mm h-1) and vegetation(Caragana korshinskii) coverages(0%,30% and 80%) on soil loss,nutrient loss,and the composition and volume fractal dimension of eroded sediment particles under simulated rainfall conditions.The results showed that vegetation cover,rainfall intensity and their interaction all had significant effects on sediment transport and the sedimentbound nutrient loss.Higher rainfall intensity and lower coverage led to higher sediment and nutrient losses.Positive linear relationships were observed between soil loss and nutrient loss.The treatments showed more significant effects on the enrichment ratio(ER) of nitrogen(ERN) than organic matter(EROM) and phosphorus(ERP).Compared with the original surface soil,the eroded sediment contained more fine particles.Under the same coverage,the clay content significantly decreased with increasing rainfall intensity.The ER of sediment-bound nutrients was positively correlated with that of clay,suggesting that the clay fraction was preferentially eroded and soil nutrients were mainly adsorbed onto or contained within this fraction.There were increments in the fractal dimension of the sediment particles compared to that of the original surface soil.Moreover,the fractal dimension was positively correlated with clay,silt,and sediment-bound OM,N,and P contents,whereas it was negatively correlated with sand content.This study demonstrated that fractal dimension analysis can be used to characterize differences in particle-size distribution and nutrient loss associated with soil erosion.

Holocene peatland development and vegetation changes in the Zoige Basin, eastern Tibetan Plateau

Peat sediments and peatland evolution process offer abundant clues into the history of vegetation and climate changes.In order to reconstruct Holocene peatland, vegetation and climate changes on eastern Tibetan Plateau, we conducted analyses of fossil pollen, loss-on-ignition, and carbon accumulation rate on one peat core from Zoige Basin. Our results show local peatland initiated at 10.3 ka, thrived in the early-mid Holocene, and then began to degrade. Throughout the Holocene, Zoige Basin was dominated by alpine meadow. Coniferous forest on montane regions expanded for several times during 10.5–4.6ka, and then dramatically retreated. Results of peatland property, principal component analysis on fossil pollen suggested the climate maintained warm/wet during 10–5.5 ka, and became relatively cold/dry in the late Holocene. Rapid degradation of peatland, retreat of coniferous forest and climatic drought/cooling occurred at 10.2–10, 9.7–9.5, 8.7–8.5, 7.7–7.4, 6.4–6, 5.5–5.2,4.8–4.5, 4–3.6, 3.1–2.7, 1.4–1.2 and 0.8–0.6 ka. The long-term variations of Holocene climate and vegetation on eastern Tibetan Plateau could be attributed to changes in insolation-driven temperature and Asian Summer Monsoon intensity, while those rapid centennial changes were probably triggered by abrupt monsoon failures and temperature anomalies in the high northern latitudes.