Longhole caving method was used to mine gently inclined thick orebody step by step in a test stope of tin mine under complex filling body. The problem that the complex filling body around the stope affects the stabili...Longhole caving method was used to mine gently inclined thick orebody step by step in a test stope of tin mine under complex filling body. The problem that the complex filling body around the stope affects the stability of roof thickness, chamber and spacer pillar in actual mining was investigated; meanwhile, the formed goaf during mining is so vulnerable that surrounding rock collapses early. Based on this point, elasticity mechanics and limit span theory were used to study separately the roof thickness and the span limit of goaf formed in mining, and then a reasonable roof thickness of 8 m and goaf span of 14 m are proposed. In addition, the stability of roof thickness, chamber and spacer pillar were investigated and analyzed by using numerical analysis method; meanwhile, the field monitoring on the displacement of caving chamber was conducted. The results show that the maximum compressive stress of surrounding rock is 20 MPa, and the maximum tensile stress is 1.2 MPa, which is less than the ultimate tensile strength of 2.4 MPa. Moreover, plastic zone has little influence on stope stability. In addition, the displacement of 11 mm is also smaller. The displacement monitoring results are consistent with the numerical results. Thus, the roof thickness and span of goaf proposed are safe.展开更多
To evaluate the papilla alterations around single-implant restorations in the anterior maxillae after crown attachment and to study the influence of soft tissue thickness on the papilla fill alteration. According to t...To evaluate the papilla alterations around single-implant restorations in the anterior maxillae after crown attachment and to study the influence of soft tissue thickness on the papilla fill alteration. According to the inclusion criteria, 32 patients subjected to implant-supported single-tooth restorations in anterior maxillae were included. The patients were assigned to two groups according to the mucosal thickness： （i） group 1, 1.5 mm≤mucosal thickness≤3 mm; and （ii） group 2, 3 mm〈mucosal thickness≤4.5 mm. Assessments of interproximal papillae at the time of crown placement （baseline） and at 6-month postloading （follow-up） were made by two prosthodontists using papilla fill index （PFI）. The mean mucosal thickness was （2.49±0.31） mm （group 1） and （3.81±0.31） mm （group 2） for the two groups respectively. A significant difference in PFI between the groups was detected at the baseline （P〈O.O01）. PFI improvements over time occurred after 6-month follow-up irrespective of the groups. When compared to group 1, the likelihood to obtain papilla fill was significantly higher for group 2 with an odds ratio of 6.05 （P〈O.O01）. The interproximal papilla level around single-implant restorations could improve significantly over time after 6-month restoration according to PFI assessment. The thicker mucosa before implant placement implied a more favorable esthetic outcome in papilla alteration.展开更多
基金Project(2012BAK09B02-05)supported by the National Science and Technology Pillar Program during the 12th Five-Year Plan PeriodProject(11KF02)supported by the Research Fund of the State Key Laboratory of Coal Resources and Mine Safety
文摘Longhole caving method was used to mine gently inclined thick orebody step by step in a test stope of tin mine under complex filling body. The problem that the complex filling body around the stope affects the stability of roof thickness, chamber and spacer pillar in actual mining was investigated; meanwhile, the formed goaf during mining is so vulnerable that surrounding rock collapses early. Based on this point, elasticity mechanics and limit span theory were used to study separately the roof thickness and the span limit of goaf formed in mining, and then a reasonable roof thickness of 8 m and goaf span of 14 m are proposed. In addition, the stability of roof thickness, chamber and spacer pillar were investigated and analyzed by using numerical analysis method; meanwhile, the field monitoring on the displacement of caving chamber was conducted. The results show that the maximum compressive stress of surrounding rock is 20 MPa, and the maximum tensile stress is 1.2 MPa, which is less than the ultimate tensile strength of 2.4 MPa. Moreover, plastic zone has little influence on stope stability. In addition, the displacement of 11 mm is also smaller. The displacement monitoring results are consistent with the numerical results. Thus, the roof thickness and span of goaf proposed are safe.
基金supported by Science and Technology Commission of Shanghai Municipality (09411955000 and 1052nm04500)National Natural Science Foundation of China (31070842)National Basic Research Program of China (2012CB933604)
文摘To evaluate the papilla alterations around single-implant restorations in the anterior maxillae after crown attachment and to study the influence of soft tissue thickness on the papilla fill alteration. According to the inclusion criteria, 32 patients subjected to implant-supported single-tooth restorations in anterior maxillae were included. The patients were assigned to two groups according to the mucosal thickness： （i） group 1, 1.5 mm≤mucosal thickness≤3 mm; and （ii） group 2, 3 mm〈mucosal thickness≤4.5 mm. Assessments of interproximal papillae at the time of crown placement （baseline） and at 6-month postloading （follow-up） were made by two prosthodontists using papilla fill index （PFI）. The mean mucosal thickness was （2.49±0.31） mm （group 1） and （3.81±0.31） mm （group 2） for the two groups respectively. A significant difference in PFI between the groups was detected at the baseline （P〈O.O01）. PFI improvements over time occurred after 6-month follow-up irrespective of the groups. When compared to group 1, the likelihood to obtain papilla fill was significantly higher for group 2 with an odds ratio of 6.05 （P〈O.O01）. The interproximal papilla level around single-implant restorations could improve significantly over time after 6-month restoration according to PFI assessment. The thicker mucosa before implant placement implied a more favorable esthetic outcome in papilla alteration.
