Study of strip-filling for old room and pillar mining goaf
According to the problems of land resources destruction and environmental pollution caused by the collapse of old room and pillar mining goaf, a goaf security evaluation model was established and applied to the safety assessment of a colliery in Ordos city. The results indicated that the room and pillar mining goafs in this coal mine area would fail with time passing. To solve the problems, with analyzing the structural characteristics and activation mechanism of old room and pillar mining goaf, based on the theory of strip mining, a new method of strip-filling for controlling subsidence of old room and pillar mining goaf was put forward and used in designing of the strip-filling plan of the colliery, the filling effect prediction have been worked out. It demonstrates that the strip-filling method is economically feasible.
Mechanism on the failure and caving of roof strata in pillar and house mining
Operating against the condition of roof strata in pillars and house mining,brought forth the calculating model of the non-beam floor with post cap which calculated the stress,displacement detail and the failure process of the coal pillar and roof strata.Also brought forth the coal pillar would occur chain failure phenomenon while one of pillar destroyed first.Verified the accuracy of the calculating model by using the similar material simulating experiment and FLAC3D numerical simulation.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.