Reinforcement of slopes using soil nailing can effectively improve slope stability, and it has been widely used in upgrading cut slopes. Based on the assumptions of stresses on the slip surface, a new method for analy...Reinforcement of slopes using soil nailing can effectively improve slope stability, and it has been widely used in upgrading cut slopes. Based on the assumptions of stresses on the slip surface, a new method for analyzing the stability of a slope reinforced with soil nails was established in the limit equilibrium theory framework, by considering that slope sliding occurs owing to shear failure of the slip surface, which subjects to Mohr–Coulomb(M–C) strength criterion. Meanwhile, in order to easily analyze the stability of a soil nailed slope in actual engineering and facilitate optimum design of parameters for soil nailing, factor of safety(FOS) contour curve charts were drawn on the basis of the established linear proportional relationship between the spacing of soil nails and slope height, and the length of soil nails and slope height. Then, by analyzing and verifying the results obtained from classic examples, some conclusions can be got as follows: 1) The results obtained from the current method are close to those obtained from the traditional limit equilibrium methods, and the current method can provide a strict solution for the slope FOS as it satisfies all the static equilibrium conditions of a sliding body, thus confirming the feasibility of the current method; 2) The slope FOS contour curve charts can be used not only to reliably analyze the stability of a soil nailed slope, but also to design optimally the parameters of soil nailing for the slope with a certain safety requirement.展开更多
The pull-out capacities for soil nailing systems comprising of one single 29 mm diameter(type A) and four 16 mm diameter(type B) rebars with grouted cement were examined.A field test and numerical analysis for the typ...The pull-out capacities for soil nailing systems comprising of one single 29 mm diameter(type A) and four 16 mm diameter(type B) rebars with grouted cement were examined.A field test and numerical analysis for the type A and type B systems were carried out to investigate the pull-out capacities and the slope stability reinforcement efficiency in soil and rock slopes.The results of the pull-out tests show the mobilized shear force and load transfer characteristics with respect to soil depth.The load-displacement relationship was examined for both type A and type B systems.Slope stability analyses were carried out to study the relationships between soil and nail reinforcement and bending stiffness as well as combined axial tension and shear forces.Factors of safety were calculated in relation to the number of nails and their outside diameters.Both soil and rock slopes were included in this evaluation.展开更多
A complete case of a deep excavation was explored. According to the practical working conditions, a 3D non-linear finite element procedure is used to simulate a deep excavation supported by the composite soil nailed w...A complete case of a deep excavation was explored. According to the practical working conditions, a 3D non-linear finite element procedure is used to simulate a deep excavation supported by the composite soil nailed wall with bored piles in soft soil. The modified cam clay model is employed as the constitutive relationship of the soil in the numerical simulation. Results from the numerical analysis are fitted well with the field data, which indicate that the research approach used is reliable. Based on the field data and numerical results of the deep excavation supported by four different patterns of the composite soil nailed wall, the significant corner effect is founded in the 3D deep excavation. If bored piles or soil anchors are considered in the composite soil nailed wall, they are beneficial to decreasing deformations and internal forces of bored piles, cement mixing piles, soil anchors, soil nailings and soil around the deep excavation. Besides, the effects due to bored piles are more significant than those deduced from soil anchors. All mentioned above prove that the composite soil nailed wall with bored piles is feasible in the deep excavation.展开更多
Pullout resistance of a soil nail is a critical parameter in design and analysis for geotechnical engineers. Due to the complexity of field conditions, the pullout behaviour of cement grouted soil nail in field is not...Pullout resistance of a soil nail is a critical parameter in design and analysis for geotechnical engineers. Due to the complexity of field conditions, the pullout behaviour of cement grouted soil nail in field is not well investigated. In this work, a number of field pullout tests of pressure grouted soil nails were conducted to estimate the pullout resistance of soil nails. The effective bond lengths of field soil nails were accurately controlled by a new grouting packer system. Typical field test results and the related comparison with typical laboratory test results reveal that the apparent coefficient of friction （ACF） decreases with the increase of overburden soil pressure when grouting pressure is constant, but increases almost linearly with the increase of grouting pressure when overburden pressure （soil depth） is unchanged. Water contents of soil samples at soil nail surfaces show obvious reductions compared with the results of soil samples from drillholes. After soil nails were completely pulled out of the ground, surface conditions of the soil nails and surrounding soil were examined. It is found that the water content values of the soil at the soil/nail interfaces decrease substantially compared with those of soil samples extracted from drillholes. In addition, all soil nails expand significantly in the diametrical direction after being pulled out of ground, indicating that the pressurized cement grout compacts the soil and penetrates into soil voids, leading to a corresponding shift of failure surface into surrounding soil mass significantly.展开更多
目的探索股骨近端防旋髓内钉(proximal femoral nail anti-rotatio,PFNA)内固定术老年患者术后营养风险相关因素并建立营养不良预测模型。方法纳入2021年1月至2024年6月于我院接受PFNA内固定术老年患者574例,分为营养不良组(389例)和营...目的探索股骨近端防旋髓内钉(proximal femoral nail anti-rotatio,PFNA)内固定术老年患者术后营养风险相关因素并建立营养不良预测模型。方法纳入2021年1月至2024年6月于我院接受PFNA内固定术老年患者574例,分为营养不良组(389例)和营养良好组(185例),比较2组患者生理、心理、社会、经济、环境、医学等因素共39个指标的差异,采用Logistic分析筛选营养风险危险因素并构建列线图模型。结果年龄偏高、BMI指数偏低、术后SAS评分偏高、骨折前较少锻炼、农民、经济压力较高,及术前白蛋白、前蛋白、血红蛋白偏低,骨折前Barthel指数偏低是PFNA内固定术患者营养风险的独立危险因素(P<0.05)。纳入上述因素构建列线图预测模型,预测该类患者发生营养不良风险的AUC(95%CI)=0.995(0.987~1.000),在阈概率>0.02时采用本模型预测PFNA内固定术患者术后营养不良风险均可临床获益。结论基于年龄、BMI指数、经济压力、骨折前锻炼情况及术前白蛋白等指标构建老年患者PFNA内固定术术后营养风险预测模型,有较高的准确性和临床应用价值。展开更多
目的探究高龄股骨转子间骨折(femoral intertrochanteric fracture,FIF)髓内治疗失败行人工股骨头置换术(femoral head replacement,FHR)后脱位的原因。方法选择2018年12月至2023年1月于河南科技大学第一附属医院因股骨近端防旋髓内钉(P...目的探究高龄股骨转子间骨折(femoral intertrochanteric fracture,FIF)髓内治疗失败行人工股骨头置换术(femoral head replacement,FHR)后脱位的原因。方法选择2018年12月至2023年1月于河南科技大学第一附属医院因股骨近端防旋髓内钉(PFNA)治疗后髓内钉失效行FHR治疗的FIF老年患者175例为研究对象,根据FHR术后股骨头是否脱位,分为脱位组(45例)和未脱位组(130例)。评估FHR的临床疗效,收集患者的临床资料(包括年龄、性别、围术期资料等)进行对比分析,判断影响FHR效果的因素是否存在多重共线性,采用LASSO回归分析筛选预测因子,根据多因素Logistic回归分析危险因素,通过各危险因素的比值比(OR)构建简易风险评分模型。绘制受试者工作特征(ROC)曲线评价模型的区分度,以Hosmer-Lemeshow(H-L)检验判断模型的校准度。结果与术前相比,术后1、12个月患者的各Harris评分均显著改善(均P<0.05);FHR术后患者并发症较少,主要包括肺部感染(2.86%)、下肢静脉血栓(2.86%)以及心功能障碍(2.86%)。LASSO回归模型获得6个预测因子,多因素Logistic回归分析发现其中患者年龄、神经及肌肉系统疾病、手术入路、术后生活习惯、术后护理为股骨头发生脱位的独立影响因素(均P<0.05)。简易风险评分模型的评分在0~21.6分,可划分为低危(<11分)、中危(11~15分)和高危(>15分)3个风险等级;训练集和验证集患者的脱位发生率无显著差异(P>0.05)。模型验证结果显示,其区分度和校准度较好。结论高龄患者FIF髓内钉固定失效后行FHR能够有效改善患者髋关节功能,且术后并发症较少。年龄、神经及肌肉系统疾病、手术入路、术后生活习惯、术后护理等为FHR后股骨头发生脱位的独立影响因素,在临床治疗时要加以重视及预防。展开更多
锂离子电池已广泛应用,但安全性仍是制约其性能提升和应用拓展的关键。本研究聚焦负极材料对三元软包电池热失控路径的影响,对比石墨与锂金属负极在针刺及外部短路测试中的安全响应。通过同步监测温度、电压、电流等关键参数并结合电池...锂离子电池已广泛应用,但安全性仍是制约其性能提升和应用拓展的关键。本研究聚焦负极材料对三元软包电池热失控路径的影响,对比石墨与锂金属负极在针刺及外部短路测试中的安全响应。通过同步监测温度、电压、电流等关键参数并结合电池拆解分析,研究发现负极特性从根本上决定了电池的失效机制。在外部短路中,锂金属负极的高反应活性及其循环后表面形成的粉末状沉积锂加剧了副反应放热,导致其瞬时电流(148.7 A vs.100.9 A)和最高温度(273℃vs.104℃)远超石墨负极,表现出更高的热失控风险。然而,在针刺测试中,锂金属负极却展现出安全优势。针刺造成的局部熔融,以及伴随的物理脱离与快速化学钝化,共同使接触电阻上升至超过40Ω,有效阻断了持续短路,从而避免热失控。相反,石墨负极因其刚性结构维持短路通路,引发剧烈放热,温度变化速率峰值超过420℃/s。本研究揭示了负极材料与热失效行为的构效关系,为通过负极改性开发兼具高能量密度和高安全性的金属锂负极二次电池提供新思路。展开更多
基金Project(2015M580702)supported by the Postdoctoral Science Foundation of ChinaProject(51608541)supported by the National Natural Science Foundation of ChinaProject(2014122066)supported by the Guizhou Provincial Department of Transportation Foundation,China
文摘Reinforcement of slopes using soil nailing can effectively improve slope stability, and it has been widely used in upgrading cut slopes. Based on the assumptions of stresses on the slip surface, a new method for analyzing the stability of a slope reinforced with soil nails was established in the limit equilibrium theory framework, by considering that slope sliding occurs owing to shear failure of the slip surface, which subjects to Mohr–Coulomb(M–C) strength criterion. Meanwhile, in order to easily analyze the stability of a soil nailed slope in actual engineering and facilitate optimum design of parameters for soil nailing, factor of safety(FOS) contour curve charts were drawn on the basis of the established linear proportional relationship between the spacing of soil nails and slope height, and the length of soil nails and slope height. Then, by analyzing and verifying the results obtained from classic examples, some conclusions can be got as follows: 1) The results obtained from the current method are close to those obtained from the traditional limit equilibrium methods, and the current method can provide a strict solution for the slope FOS as it satisfies all the static equilibrium conditions of a sliding body, thus confirming the feasibility of the current method; 2) The slope FOS contour curve charts can be used not only to reliably analyze the stability of a soil nailed slope, but also to design optimally the parameters of soil nailing for the slope with a certain safety requirement.
文摘The pull-out capacities for soil nailing systems comprising of one single 29 mm diameter(type A) and four 16 mm diameter(type B) rebars with grouted cement were examined.A field test and numerical analysis for the type A and type B systems were carried out to investigate the pull-out capacities and the slope stability reinforcement efficiency in soil and rock slopes.The results of the pull-out tests show the mobilized shear force and load transfer characteristics with respect to soil depth.The load-displacement relationship was examined for both type A and type B systems.Slope stability analyses were carried out to study the relationships between soil and nail reinforcement and bending stiffness as well as combined axial tension and shear forces.Factors of safety were calculated in relation to the number of nails and their outside diameters.Both soil and rock slopes were included in this evaluation.
基金Foundation item： Project（2009-K3-2） supported by the Ministry of Housing and Urban-Rural Development of China
文摘A complete case of a deep excavation was explored. According to the practical working conditions, a 3D non-linear finite element procedure is used to simulate a deep excavation supported by the composite soil nailed wall with bored piles in soft soil. The modified cam clay model is employed as the constitutive relationship of the soil in the numerical simulation. Results from the numerical analysis are fitted well with the field data, which indicate that the research approach used is reliable. Based on the field data and numerical results of the deep excavation supported by four different patterns of the composite soil nailed wall, the significant corner effect is founded in the 3D deep excavation. If bored piles or soil anchors are considered in the composite soil nailed wall, they are beneficial to decreasing deformations and internal forces of bored piles, cement mixing piles, soil anchors, soil nailings and soil around the deep excavation. Besides, the effects due to bored piles are more significant than those deduced from soil anchors. All mentioned above prove that the composite soil nailed wall with bored piles is feasible in the deep excavation.
基金Foundation item： Project（NTF 12015） supported by the Scientific Research Foundation for Talent of Shantou University, China Project（PolyU 5320107E） supported by the Research Grants Committee General Research Fund, China
文摘Pullout resistance of a soil nail is a critical parameter in design and analysis for geotechnical engineers. Due to the complexity of field conditions, the pullout behaviour of cement grouted soil nail in field is not well investigated. In this work, a number of field pullout tests of pressure grouted soil nails were conducted to estimate the pullout resistance of soil nails. The effective bond lengths of field soil nails were accurately controlled by a new grouting packer system. Typical field test results and the related comparison with typical laboratory test results reveal that the apparent coefficient of friction （ACF） decreases with the increase of overburden soil pressure when grouting pressure is constant, but increases almost linearly with the increase of grouting pressure when overburden pressure （soil depth） is unchanged. Water contents of soil samples at soil nail surfaces show obvious reductions compared with the results of soil samples from drillholes. After soil nails were completely pulled out of the ground, surface conditions of the soil nails and surrounding soil were examined. It is found that the water content values of the soil at the soil/nail interfaces decrease substantially compared with those of soil samples extracted from drillholes. In addition, all soil nails expand significantly in the diametrical direction after being pulled out of ground, indicating that the pressurized cement grout compacts the soil and penetrates into soil voids, leading to a corresponding shift of failure surface into surrounding soil mass significantly.
文摘目的探索股骨近端防旋髓内钉(proximal femoral nail anti-rotatio,PFNA)内固定术老年患者术后营养风险相关因素并建立营养不良预测模型。方法纳入2021年1月至2024年6月于我院接受PFNA内固定术老年患者574例,分为营养不良组(389例)和营养良好组(185例),比较2组患者生理、心理、社会、经济、环境、医学等因素共39个指标的差异,采用Logistic分析筛选营养风险危险因素并构建列线图模型。结果年龄偏高、BMI指数偏低、术后SAS评分偏高、骨折前较少锻炼、农民、经济压力较高,及术前白蛋白、前蛋白、血红蛋白偏低,骨折前Barthel指数偏低是PFNA内固定术患者营养风险的独立危险因素(P<0.05)。纳入上述因素构建列线图预测模型,预测该类患者发生营养不良风险的AUC(95%CI)=0.995(0.987~1.000),在阈概率>0.02时采用本模型预测PFNA内固定术患者术后营养不良风险均可临床获益。结论基于年龄、BMI指数、经济压力、骨折前锻炼情况及术前白蛋白等指标构建老年患者PFNA内固定术术后营养风险预测模型,有较高的准确性和临床应用价值。
文摘目的探究高龄股骨转子间骨折(femoral intertrochanteric fracture,FIF)髓内治疗失败行人工股骨头置换术(femoral head replacement,FHR)后脱位的原因。方法选择2018年12月至2023年1月于河南科技大学第一附属医院因股骨近端防旋髓内钉(PFNA)治疗后髓内钉失效行FHR治疗的FIF老年患者175例为研究对象,根据FHR术后股骨头是否脱位,分为脱位组(45例)和未脱位组(130例)。评估FHR的临床疗效,收集患者的临床资料(包括年龄、性别、围术期资料等)进行对比分析,判断影响FHR效果的因素是否存在多重共线性,采用LASSO回归分析筛选预测因子,根据多因素Logistic回归分析危险因素,通过各危险因素的比值比(OR)构建简易风险评分模型。绘制受试者工作特征(ROC)曲线评价模型的区分度,以Hosmer-Lemeshow(H-L)检验判断模型的校准度。结果与术前相比,术后1、12个月患者的各Harris评分均显著改善(均P<0.05);FHR术后患者并发症较少,主要包括肺部感染(2.86%)、下肢静脉血栓(2.86%)以及心功能障碍(2.86%)。LASSO回归模型获得6个预测因子,多因素Logistic回归分析发现其中患者年龄、神经及肌肉系统疾病、手术入路、术后生活习惯、术后护理为股骨头发生脱位的独立影响因素(均P<0.05)。简易风险评分模型的评分在0~21.6分,可划分为低危(<11分)、中危(11~15分)和高危(>15分)3个风险等级;训练集和验证集患者的脱位发生率无显著差异(P>0.05)。模型验证结果显示,其区分度和校准度较好。结论高龄患者FIF髓内钉固定失效后行FHR能够有效改善患者髋关节功能,且术后并发症较少。年龄、神经及肌肉系统疾病、手术入路、术后生活习惯、术后护理等为FHR后股骨头发生脱位的独立影响因素,在临床治疗时要加以重视及预防。
文摘锂离子电池已广泛应用,但安全性仍是制约其性能提升和应用拓展的关键。本研究聚焦负极材料对三元软包电池热失控路径的影响,对比石墨与锂金属负极在针刺及外部短路测试中的安全响应。通过同步监测温度、电压、电流等关键参数并结合电池拆解分析,研究发现负极特性从根本上决定了电池的失效机制。在外部短路中,锂金属负极的高反应活性及其循环后表面形成的粉末状沉积锂加剧了副反应放热,导致其瞬时电流(148.7 A vs.100.9 A)和最高温度(273℃vs.104℃)远超石墨负极,表现出更高的热失控风险。然而,在针刺测试中,锂金属负极却展现出安全优势。针刺造成的局部熔融,以及伴随的物理脱离与快速化学钝化,共同使接触电阻上升至超过40Ω,有效阻断了持续短路,从而避免热失控。相反,石墨负极因其刚性结构维持短路通路,引发剧烈放热,温度变化速率峰值超过420℃/s。本研究揭示了负极材料与热失效行为的构效关系,为通过负极改性开发兼具高能量密度和高安全性的金属锂负极二次电池提供新思路。
