Angle of break(AOB)is the acute angle created by the coal seam bedding plane and caving line formed by roof strata movement after extraction of a longwall panel.It has a significant influence on stress redistribution ...Angle of break(AOB)is the acute angle created by the coal seam bedding plane and caving line formed by roof strata movement after extraction of a longwall panel.It has a significant influence on stress redistribution both in the gob and abutment.Throughout numerical simulation investigations up to now,little attention has been paid to it or an AOB of 90°was used,which however,is not realistic.This paper presents a detailed numerical modelling incorporating the AOB against Zhenchengdi Coal Mine.The AOB was obtained through cross-measure boreholes.Hoek-Brown constitutive model was used to simulate the rock masses.Double-yield constitutive model,which was best fitted by Salamon's model,was used to simulate the gob.The results show that a‘‘/\shape"shear failure zone develops around the gob.The shear failure in the floor along the panel edge is due to opposite shear of rock mass on two sides of the caving line,and the number of yielded zones within the gob floor close to the gob edge is smaller.According to the research,the entry was determined to be driven under the gob edge employing splitlevel longwall panel layout(SLPL).The other numerical simulation for SLPL shows that stress around the god-side entry is much smaller than pre-mining stress,and the area of intact rock mass at the elevating section is larger than conventional layout.Numerical modelling was then validated by field observation.展开更多
For shallow tunnels of single-lane railway and four-lane road,numerical simulation using finite differential code was conducted.The mechanical behavior of loose rock masses was studied considering the influences of sh...For shallow tunnels of single-lane railway and four-lane road,numerical simulation using finite differential code was conducted.The mechanical behavior of loose rock masses was studied considering the influences of shear dilation on the shape of the failure surface for the shallow tunnels,and the break angles using numerical simulation was compared with those using the Rankine's analytical solutions and design code.From the comparisons,it is found that the difference between the break angle by numerical simulation and the design code is small when the shear dilation angle is equal to 0,with the maximum relative difference being less than 0.2% in road tunnels.With the dilation angle's increase,the loose plasticity zone area of surrounding rock reduces obviously,and the break angle increases gradually.When the dilation angle is equal to the internal friction angle,the materials follow associated flow rule,and the numerical solution of the break angle is larger than the analytical solution,with the maximum relative difference being greater than 16.7% in road tunnels.Therefore,associated flow rule leads to overestimating break angle,and the dilation angle has an important influence on the failure surface shape for shallow tunnels in the loose surrounding rocks.展开更多
Chemical softener (Cepreton UN) is used to soften the cellulosic fiber (cotton) in the textile industries to make clothes better to touch. Therefore, this study investigated the effects of Cepreton UN on both physical...Chemical softener (Cepreton UN) is used to soften the cellulosic fiber (cotton) in the textile industries to make clothes better to touch. Therefore, this study investigated the effects of Cepreton UN on both physical (length, aspect ratio, contact angle, and moisture regain) and mechanical (load at break, elongation at break, tensile stress, young’s modulus, and tenacity) properties of the lignocellulosic canola (HYREAR 3) fibers extracted from narrow, medium, and wide stems. ANOVA showed that fiber diameter had strong effects on elongation at break, load at break, tensile stress, young’s modulus, and aspect ratio for all fibers. Corrgram values showed that tensile stress, young’s modulus, and aspect ratio were negatively correlated to fiber diameter whereas load at break and tenacity were mostly positively correlated to fiber diameter. The fibers were treated with 2% and 10% Cepreton UN and compared with control fibers. In most cases, the fiber diameter was decreased in both 2% and 10% treated medium stem fibers. The mean values of elongation at break, load at break, tenacity, and contact angle were decreased for 10% and increased for 2% and the mean values of tensile stress, young’s modulus, and aspect ratio were decreased for 2% and increased for 10% treated medium stem fibers. Moisture regain (%) mostly decreased for 2%, and increased for 10% treated fibers. Low pH (4.5) had an almost similar effect on fibers as 2% Cepreton UN. Overall, 2% Cepreton UN treatment is found to be better than 10% to make canola fibers less stiff and low pH was found to be an alternative softener treatment strategy.展开更多
基金This work was supported by the National Natural Science Foundation of China,Young Scientists Fund(No.51804209)NSFC-Shanxi Joint Fund for Coal-Based Low-Carbon Technology(No.U1710258)Shanxi Applied Basic Research Programs,Science and Technology Foundation for Youths(No.201801D221363).THX.
文摘Angle of break(AOB)is the acute angle created by the coal seam bedding plane and caving line formed by roof strata movement after extraction of a longwall panel.It has a significant influence on stress redistribution both in the gob and abutment.Throughout numerical simulation investigations up to now,little attention has been paid to it or an AOB of 90°was used,which however,is not realistic.This paper presents a detailed numerical modelling incorporating the AOB against Zhenchengdi Coal Mine.The AOB was obtained through cross-measure boreholes.Hoek-Brown constitutive model was used to simulate the rock masses.Double-yield constitutive model,which was best fitted by Salamon's model,was used to simulate the gob.The results show that a‘‘/\shape"shear failure zone develops around the gob.The shear failure in the floor along the panel edge is due to opposite shear of rock mass on two sides of the caving line,and the number of yielded zones within the gob floor close to the gob edge is smaller.According to the research,the entry was determined to be driven under the gob edge employing splitlevel longwall panel layout(SLPL).The other numerical simulation for SLPL shows that stress around the god-side entry is much smaller than pre-mining stress,and the area of intact rock mass at the elevating section is larger than conventional layout.Numerical modelling was then validated by field observation.
基金Project (200631878557) supported by West Traffic of Science and Technology of ChinaProject (200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of ChinaProject (05-0686) supported by the Program for New Century Excellent Talents in University
文摘For shallow tunnels of single-lane railway and four-lane road,numerical simulation using finite differential code was conducted.The mechanical behavior of loose rock masses was studied considering the influences of shear dilation on the shape of the failure surface for the shallow tunnels,and the break angles using numerical simulation was compared with those using the Rankine's analytical solutions and design code.From the comparisons,it is found that the difference between the break angle by numerical simulation and the design code is small when the shear dilation angle is equal to 0,with the maximum relative difference being less than 0.2% in road tunnels.With the dilation angle's increase,the loose plasticity zone area of surrounding rock reduces obviously,and the break angle increases gradually.When the dilation angle is equal to the internal friction angle,the materials follow associated flow rule,and the numerical solution of the break angle is larger than the analytical solution,with the maximum relative difference being greater than 16.7% in road tunnels.Therefore,associated flow rule leads to overestimating break angle,and the dilation angle has an important influence on the failure surface shape for shallow tunnels in the loose surrounding rocks.
文摘Chemical softener (Cepreton UN) is used to soften the cellulosic fiber (cotton) in the textile industries to make clothes better to touch. Therefore, this study investigated the effects of Cepreton UN on both physical (length, aspect ratio, contact angle, and moisture regain) and mechanical (load at break, elongation at break, tensile stress, young’s modulus, and tenacity) properties of the lignocellulosic canola (HYREAR 3) fibers extracted from narrow, medium, and wide stems. ANOVA showed that fiber diameter had strong effects on elongation at break, load at break, tensile stress, young’s modulus, and aspect ratio for all fibers. Corrgram values showed that tensile stress, young’s modulus, and aspect ratio were negatively correlated to fiber diameter whereas load at break and tenacity were mostly positively correlated to fiber diameter. The fibers were treated with 2% and 10% Cepreton UN and compared with control fibers. In most cases, the fiber diameter was decreased in both 2% and 10% treated medium stem fibers. The mean values of elongation at break, load at break, tenacity, and contact angle were decreased for 10% and increased for 2% and the mean values of tensile stress, young’s modulus, and aspect ratio were decreased for 2% and increased for 10% treated medium stem fibers. Moisture regain (%) mostly decreased for 2%, and increased for 10% treated fibers. Low pH (4.5) had an almost similar effect on fibers as 2% Cepreton UN. Overall, 2% Cepreton UN treatment is found to be better than 10% to make canola fibers less stiff and low pH was found to be an alternative softener treatment strategy.
文摘采用正交试验设计方法,对纳米TiO2纯棉织物抗皱整理工艺参数进行五因素五水平试验,运用数学方法分析此整理体系中各影响因素的显著程度,并得到最佳的整理工艺.分析表明,树脂浓度和催化剂MgCl2的浓度对折皱回复角和强力保留率的影响均较大,其中树脂用量对折皱回复角的影响最为显著.纳米TiO2纯棉织物抗皱整理的最佳工艺为:纳米TiO2质量浓度为0.5 g/L,树脂质量浓度为100 g/L,催化剂质量浓度为10 g/L,焙烘条件为160℃×3 min.
